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Sample records for calibration human voxel

  1. Calibration Human Voxel Phantoms for In Vivo Measurement of ''2 sup 4 sup 1 Am in Bone at the Whole Body Counter Facility of CIEMAT

    CERN Document Server

    Moraleda, M; Navarro, J F; Navarro, T

    2002-01-01

    The Whole Body Counting facility of CIEMAT is capable of carrying out In-Vivo measurements of radionuclides emitting X-rays and low energy gamma radiation internally deposited in the body. The system to use for this purpose consists of flour Low energy Germanium (LeGe) Camberra detectors working in the energy range from 10 to 1000 keV. Physical phantoms with a known contamination in the organ of interest are normally used for the calibration of the LEGe detection system. In this document we present a calibration method using the Monte Carlo technique (MCNP4C) over a voxel phantom obtained from a computerized tomography of a real human head. The phantom consists of 104017 (43x59x41) cubic voxels, 4 mn on each side, os specific tissues, but for this simulation only two types are taken into account: adipose tissue and hard bone. The skull is supposed to be contaminated with ''241 Am and the trajectories of the photons are simulated till they reach the germanium detectors. The detectors were also simulated in det...

  2. Calibration Human Voxel Phantoms for In Vivo Measurement of ''241 Am in Bone at the Whole Body Counter Facility of CIEMAT

    Energy Technology Data Exchange (ETDEWEB)

    Moraleda, M.; Lopez, M. A.; Gomez Ros, J. M.; Navarro, T.; Navarro, J. F.

    2002-07-01

    The Whole Body Counting facility of CIEMAT is capable of carrying out In-Vivo measurements of radionuclides emitting X-rays and low energy gamma radiation internally deposited in the body. The system to use for this purpose consists of flour Low energy Germanium (LeGe) Camberra detectors working in the energy range from 10 to 1000 keV. Physical phantoms with a known contamination in the organ of interest are normally used for the calibration of the LEGe detection system. In this document we present a calibration method using the Monte Carlo technique (MCNP4C) over a voxel phantom obtained from a computerized tomography of a real human head. The phantom consists of 104017 (43x59x41) cubic voxels, 4 mn on each side, os specific tissues, but for this simulation only two types are taken into account: adipose tissue and hard bone. The skull is supposed to be contaminated with ''241 Am and the trajectories of the photons are simulated till they reach the germanium detectors. The detectors were also simulated in detail to obtain a good agreement with the reality. In order to verify the accuracy of this procedure to reproduce the experiments, the MCNP results are compared with laboratory measurements of a head phantom simulating an internal contamination of 1000 Bq of ''241 Am deposited in bone. Different relative positions source-detector were tried to look for the best countring geometry for measurement of a contaminated skull. Efficiency values are obtained and compared, resulting in the validation of the mathematical method for the assessment of internal contamination of American deposited in skeleton. (Author) 16 refs.

  3. Automatic Calibration Method of Voxel Size for Cone-beam 3D-CT Scanning System

    CERN Document Server

    Yang, Min; Liu, Yipeng; Men, Fanyong; Li, Xingdong; Liu, Wenli; Wei, Dongbo

    2013-01-01

    For cone-beam three-dimensional computed tomography (3D-CT) scanning system, voxel size is an important indicator to guarantee the accuracy of data analysis and feature measurement based on 3D-CT images. Meanwhile, the voxel size changes with the movement of the rotary table along X-ray direction. In order to realize the automatic calibration of the voxel size, a new easily-implemented method is proposed. According to this method, several projections of a spherical phantom are captured at different imaging positions and the corresponding voxel size values are calculated by non-linear least square fitting. Through these interpolation values, a linear equation is obtained, which reflects the relationship between the rotary table displacement distance from its nominal zero position and the voxel size. Finally, the linear equation is imported into the calibration module of the 3D-CT scanning system, and when the rotary table is moving along X-ray direction, the accurate value of the voxel size is dynamically expo...

  4. Fast Monte Carlo simulation on a voxelized human phantom deformed to a patient

    Energy Technology Data Exchange (ETDEWEB)

    Bueno, G.; Deniz, O.; Carrascosa, C. B.; Delgado, J. M.; Brualla, L. [E.T.S.I. Industriales, Universidad de Castilla-La Mancha, Avenida Camilo Jose Cela s/n, E-13071 Ciudad Real (Spain); Instituto Oncologico (Grupo IMO), Hospital La Milagrosa, Modesto Lafuente, 14, E-28010 Madrid (Spain); NCTeam, Strahlenklinik, Universitaetsklinikum Essen, Hufelandstr. 55, D-45122 Essen (Germany)

    2009-11-15

    Purpose: A method for performing fast simulations of absorbed dose using a patient's computerized tomography (CT) scan without explicitly relying on a calibration curve is presented. Methods: The method is based on geometrical deformations performed on a standard voxelized human phantom. This involves spatially transforming the human phantom to align it with the patient CT image. Since the chemical composition and density of each voxel are given in the phantom data, a calibration curve is not used in the proposed method. For this study, the Monte Carlo (MC) code PENELOPE has been used as the simulation of reference. The results obtained with PENELOPE simulations are compared to those obtained with PENFAST and with the collapsed cone convolution algorithm implemented in a commercial treatment planning system. Results: The comparisons of the absorbed doses calculated with the different algorithms on two patient CTs and the corresponding deformed phantoms show a maximum distance to agreement of 2 mm, and in general, the obtained absorbed dose distributions are compatible within the reached statistical uncertainty. The validity of the deformation method for a broad range of patients is shown using MC simulations in random density phantoms. A PENFAST simulation of a 6 MV photon beam impinging on a patient CT reaches 2% statistical uncertainty in the absorbed dose, in a 0.1 cm{sup 3} voxel along the central axis, in 10 min running on a single core of a 2.8 GHz CPU. Conclusions: The proposed method of the absorbed dose calculation in a deformed voxelized phantom allows for dosimetric studies in the geometry of a patient CT scan. This is due to the fact that the chemical composition and material density of the phantom are known. Furthermore, simulation using the phantom geometry can provide dosimetric information for each organ. The method can be used for quality assurance procedures. In relation to PENFAST, it is shown that a purely condensed-history algorithm (class

  5. Application of Voxel Phantoms to Study the Influence of Heterogeneous Distribution of Actinides in Lungs on In Vivo Counting Calibration Factors Using Animal Experimentations

    Energy Technology Data Exchange (ETDEWEB)

    Lamart, S.; Pierrat, N.; De Carlan, L.; Franck, D. [IRSN/DRPH/SDI/LEDI, BP 17, F-92 262 Fontenay-aux-Roses (France); Dudoignon, N. [IRSN/DRPH/SRBE/LRPAT, BP 17, F-92 262 Fontenay-aux-Roses (France); Rateau, S.; Van der Meeren, A.; Rouit, E. [CEA/DSV/DRR/SRCA/LRT BP no 12, F-91680 Bruyeres-le-Chatel (France); Bottlaender, M. [CEA/SHFJ, 4, place du General Leclerc F-91400 Orsay (France)

    2006-07-01

    Calibration of lung counting system dedicated to retention assessment of actinides in the lungs remains critical due to large uncertainties in calibration factors. Among them, the detector positioning, the chest wall thickness and composition (muscle/fat) assessment, and the distribution of the contamination are the main parameters influencing the detector response. In order to reduce these uncertainties, a numerical approach based on the application of voxel phantoms (numerical phantoms based on tomographic images, CT or MRI) associated to a Monte-Carlo code (namely M.C.N.P.) was developed. It led to the development of a dedicated tool, called O.E.D.I.P.E., that allows to easily handle realistic voxel phantoms for the simulation of in vivo measurement (or dose calculation, application that will not be presented in this paper). The goal of this paper is to present our study of the influence of the lung distribution on calibration factors using both animal experimentations and our numerical method. Indeed, physical anthropomorphic phantoms used for calibration always consider a uniform distribution of the source in the lungs, which is not true in many contamination conditions. The purpose of the study is to compare the response of the measurement detectors using a real distribution of actinide particles in the lungs, obtained from animal experimentations, with the homogeneous one considered as the reference. This comparison was performed using O.E.D.I.P.E. that can almost simulate any source distribution. A non human primate was contaminated heterogeneously by intra-tracheal administration of actinide oxide. After euthanasia, gamma spectrometry measurements were performed on the pulmonary lobes to obtain the distribution of the contamination in the lungs. This realistic distribution was used to simulate an heterogeneous contamination in the numerical phantom of the non human primate, which was compared with a simulation of an homogeneous contamination presenting the

  6. Computer simulations for internal dosimetry using voxel models.

    Science.gov (United States)

    Kinase, Sakae; Mohammadi, Akram; Takahashi, Masa; Saito, Kimiaki; Zankl, Maria; Kramer, Richard

    2011-07-01

    In the Japan Atomic Energy Agency, several studies have been conducted on the use of voxel models for internal dosimetry. Absorbed fractions (AFs) and S values have been evaluated for preclinical assessments of radiopharmaceuticals using human voxel models and a mouse voxel model. Computational calibration of in vivo measurement system has been also made using Japanese and Caucasian voxel models. In addition, for radiation protection of the environment, AFs have been evaluated using a frog voxel model. Each study was performed by using Monte Carlo simulations. Consequently, it was concluded that these data of Monte Carlo simulations and voxel models could adequately reproduce measurement results. Voxel models were found to be a significant tool for internal dosimetry since the models are anatomically realistic. This fact indicates that several studies on correction of the in vivo measurement efficiency for the variability of human subjects and interspecies scaling of organ doses will succeed.

  7. A Calibrated Index of Human Development

    Science.gov (United States)

    Lind, Niels

    2010-01-01

    The weightings of the four component indicators of the UNDP's Human Development Index HDI appear to be arbitrary and have not been given justification. This paper develops a variant of the HDI, calculated to reflect peoples' revealed evaluations of education and the productivity of work. The resulting Calibrated human Development Index CDI has a…

  8. Voxel-based approach to generate entire human metacarpal bone with microscopic architecture for finite element analysis.

    Science.gov (United States)

    Tang, C Y; Tsui, C P; Tang, Y M; Wei, L; Wong, C T; Lam, K W; Ip, W Y; Lu, W W J; Pang, M Y C

    2014-01-01

    With the development of micro-computed tomography (micro-CT) technology, it is possible to construct three-dimensional (3D) models of human bone without destruction of samples and predict mechanical behavior of bone using finite element analysis (FEA). However, due to large number of elements required for constructing the FE models of entire bone, this demands a substantial computational effort and the analysis usually needs a high level of computer. In this article, a voxel-based approach for generation of FE models of entire bone with microscopic architecture from micro-CT image data is proposed. To enable the FE analyses of entire bone to be run even on a general personal computer, grayscale intensity thresholds were adopted to reduce the amount of elements. Human metacarpal bone (MCP) bone was used as an example for demonstrating the applicability of the proposed method. The micro-CT images of the MCP bone were combined and converted into 3D array of pixels. Dual grayscale intensity threshold parameters were used to distinguish the pixels of bone tissues from those of surrounding soft tissues and improve predictive accuracy for the FE analyses with different sizes of elements. The method of selecting an appropriate value of the second grayscale intensity threshold was also suggested to minimize the area error for the reconstructed cross-sections of a FE structure. Experimental results showed that the entire FE MCP bone with microscopic architecture could be modeled and analyzed on a personal computer with reasonable accuracy.

  9. Small-world and scale-free organization of voxel-based resting-state functional connectivity in the human brain.

    Science.gov (United States)

    van den Heuvel, M P; Stam, C J; Boersma, M; Hulshoff Pol, H E

    2008-11-15

    The brain is a complex dynamic system of functionally connected regions. Graph theory has been successfully used to describe the organization of such dynamic systems. Recent resting-state fMRI studies have suggested that inter-regional functional connectivity shows a small-world topology, indicating an organization of the brain in highly clustered sub-networks, combined with a high level of global connectivity. In addition, a few studies have investigated a possible scale-free topology of the human brain, but the results of these studies have been inconclusive. These studies have mainly focused on inter-regional connectivity, representing the brain as a network of brain regions, requiring an arbitrary definition of such regions. However, using a voxel-wise approach allows for the model-free examination of both inter-regional as well as intra-regional connectivity and might reveal new information on network organization. Especially, a voxel-based study could give information about a possible scale-free organization of functional connectivity in the human brain. Resting-state 3 Tesla fMRI recordings of 28 healthy subjects were acquired and individual connectivity graphs were formed out of all cortical and sub-cortical voxels with connections reflecting inter-voxel functional connectivity. Graph characteristics from these connectivity networks were computed. The clustering-coefficient of these networks turned out to be much higher than the clustering-coefficient of comparable random graphs, together with a short average path length, indicating a small-world organization. Furthermore, the connectivity distribution of the number of inter-voxel connections followed a power-law scaling with an exponent close to 2, suggesting a scale-free network topology. Our findings suggest a combined small-world and scale-free organization of the functionally connected human brain. The results are interpreted as evidence for a highly efficient organization of the functionally connected

  10. Brain regions involved in human movement perception: a quantitative voxel-based meta-analysis.

    Science.gov (United States)

    Grosbras, Marie-Hélène; Beaton, Susan; Eickhoff, Simon B

    2012-02-01

    Face, hands, and body movements are powerful signals essential for social interactions. In the last 2 decades, a large number of brain imaging studies have explored the neural correlates of the perception of these signals. Formal synthesis is crucially needed, however, to extract the key circuits involved in human motion perception across the variety of paradigms and stimuli that have been used. Here, we used the activation likelihood estimation (ALE) meta-analysis approach with random effect analysis. We performed meta-analyses on three classes of biological motion: movement of the whole body, hands, and face. Additional analyses of studies of static faces or body stimuli and sub-analyses grouping experiments as a function of their control stimuli or task employed allowed us to identify main effects of movements and forms perception, as well as effects of task demand. In addition to specific features, all conditions showed convergence in occipito-temporal and fronto-parietal regions, but with different peak location and extent. The conjunction of the three ALE maps revealed convergence in all categories in a region of the right posterior superior temporal sulcus as well as in a bilateral region at the junction between middle temporal and lateral occipital gyri. Activation in these regions was not a function of attentional demand and was significant also when controlling for non-specific motion perception. This quantitative synthesis points towards a special role for posterior superior temporal sulcus for integrating human movement percept, and supports a specific representation for body parts in middle temporal, fusiform, precentral, and parietal areas.

  11. Calibrated kallikrein generation in human plasma

    DEFF Research Database (Denmark)

    Biltoft, D; Sidelmann, J J; Olsen, L F

    2016-01-01

    generation method as a template. RESULTS: A suitable kallikrein specific fluorogenic substrate was identified (KM=0.91mM, kcat=19s(-1)), and kallikrein generation could be measured in undiluted plasma when silica was added as activator. Disturbing effects, including substrate depletion and the inner......-filter effect, however, affected the signal. These problems were corrected for by external calibration with α2-macroglobulin-kallikrein complexes. Selectivity studies of the substrate, experiments with FXII and PK depleted plasmas, and plasma with high or low complement C1-esterase inhibitor activity indicated...

  12. Gait analysis and validation using voxel data.

    Science.gov (United States)

    Wang, Fang; Stone, Erik; Dai, Wenqing; Skubic, Marjorie; Keller, James

    2009-01-01

    In this paper, we present a method for extracting gait parameters including walking speed, step time and step length from a three-dimensional voxel reconstruction, which is built from two calibrated camera views. These parameters are validated with a GAITRite Electronic mat and a Vicon motion capture system. Experiments were conducted in which subjects walked across the GAITRite mat at various speeds while the Vicon cameras recorded the motion of reflective markers attached to subjects' shoes, and our two calibrated cameras captured the images. Excellent agreements were found for walking speed. Step time and step length were also found to have good agreement given the limitation of frame rate and voxel resolution.

  13. Cerebral morphology and dopamine D2/D3 receptor distribution in humans: a combined [18F]fallypride and voxel-based morphometry study.

    Science.gov (United States)

    Woodward, Neil D; Zald, David H; Ding, Zhaohua; Riccardi, Patrizia; Ansari, M Sib; Baldwin, Ronald M; Cowan, Ronald L; Li, Rui; Kessler, Robert M

    2009-05-15

    The relationship between cerebral morphology and the expression of dopamine receptors has not been extensively studied in humans. Elucidation of such relationships may have important methodological implications for clinical studies of dopamine receptor ligand binding differences between control and patient groups. The association between cerebral morphology and dopamine receptor distribution was examined in 45 healthy subjects who completed T1-weighted structural MRI and PET scanning with the D(2)/D(3) ligand [(18)F]fallypride. Optimized voxel-based morphometry was used to create grey matter volume and density images. Grey matter volume and density images were correlated with binding potential (BP(ND)) images on a voxel-by-voxel basis using the Biological Parametric Mapping toolbox. Associations between cerebral morphology and BP(ND) were also examined for selected regions-of-interest (ROIs) after spatial normalization. Voxel-wise analyses indicated that grey matter volume and density positively correlated with BP(ND) throughout the midbrain, including the substantia nigra. Positive correlations were observed in medial cortical areas, including anterior cingulate and medial prefrontal cortex, and circumscribed regions of the temporal, frontal, and parietal lobes. ROI analyses revealed significant positive correlations between BP(ND) and cerebral morphology in the caudate, thalamus, and amygdala. Few negative correlations between morphology and BP(ND) were observed. Overall, grey matter density appeared more strongly correlated with BP(ND) than grey matter volume. Cerebral morphology, particularly grey matter density, correlates with [(18)F]fallypride BP(ND) in a regionally specific manner. Clinical studies comparing dopamine receptor availability between clinical and control groups may benefit by accounting for potential differences in cerebral morphology that exist even after spatial normalization.

  14. Multistep Lattice-Voxel method utilizing lattice function for Monte-Carlo treatment planning with pixel based voxel model.

    Science.gov (United States)

    Kumada, H; Saito, K; Nakamura, T; Sakae, T; Sakurai, H; Matsumura, A; Ono, K

    2011-12-01

    Treatment planning for boron neutron capture therapy generally utilizes Monte-Carlo methods for calculation of the dose distribution. The new treatment planning system JCDS-FX employs the multi-purpose Monte-Carlo code PHITS to calculate the dose distribution. JCDS-FX allows to build a precise voxel model consisting of pixel based voxel cells in the scale of 0.4×0.4×2.0 mm(3) voxel in order to perform high-accuracy dose estimation, e.g. for the purpose of calculating the dose distribution in a human body. However, the miniaturization of the voxel size increases calculation time considerably. The aim of this study is to investigate sophisticated modeling methods which can perform Monte-Carlo calculations for human geometry efficiently. Thus, we devised a new voxel modeling method "Multistep Lattice-Voxel method," which can configure a voxel model that combines different voxel sizes by utilizing the lattice function over and over. To verify the performance of the calculation with the modeling method, several calculations for human geometry were carried out. The results demonstrated that the Multistep Lattice-Voxel method enabled the precise voxel model to reduce calculation time substantially while keeping the high-accuracy of dose estimation.

  15. Effect of visual experience on structural organization of the human brain: A voxel based morphometric study using DARTEL

    Energy Technology Data Exchange (ETDEWEB)

    Modi, Shilpi, E-mail: modi_shilpi@yahoo.co.in [NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (DRDO), Lucknow Road, Timarpur, Delhi (India); Bhattacharya, Manisha, E-mail: manishab10@gmail.com [NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (DRDO), Lucknow Road, Timarpur, Delhi (India); Singh, Namita, E-mail: namita23m@gmail.com [NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (DRDO), Lucknow Road, Timarpur, Delhi (India); Tripathi, Rajendra Prasad, E-mail: director@inmas.drdo.in [NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (DRDO), Lucknow Road, Timarpur, Delhi (India); Khushu, Subash, E-mail: skhushu@yahoo.com [NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (DRDO), Lucknow Road, Timarpur, Delhi (India)

    2012-10-15

    Objective: To investigate structural reorganization in the brain with differential visual experience using Voxel-Based Morphometry with Diffeomorphic Anatomic Registration Through Exponentiated Lie algebra algorithm (DARTEL) approach. Materials and methods: High resolution structural MR images were taken in fifteen normal sighted healthy controls, thirteen totally blind subjects and six partial blind subjects. The analysis was carried out using SPM8 software on MATLAB 7.6.0 platform. Results: VBM study revealed gray matter volume atrophy in the cerebellum and left inferior parietal cortex in total blind subjects and in left inferior parietal cortex, right caudate nucleus, and left primary visual cortex in partial blind subjects as compared to controls. White matter volume loss was found in calcarine gyrus in total blind subjects and Thlamus-somatosensory region in partially blind subjects as compared to controls. Besides, an increase in Gray Matter volume was also found in left middle occipital and middle frontal gyrus and right entorhinal cortex, and an increase in White Matter volume was found in superior frontal gyrus, left middle temporal gyrus and right Heschl's gyrus in totally blind subjects as compared to controls. Comparison between total and partial blind subjects revealed a greater Gray Matter volume in left cerebellum of partial blinds and left Brodmann area 18 of total blind subjects. Conclusion: Results suggest that, loss of vision at an early age can induce significant structural reorganization on account of the loss of visual input. These plastic changes are different in early onset of total blindness as compared to partial blindness.

  16. 基于VOXEL-MAN虚拟人体开发平台实现经络三维表达%Three-Dimension Representation for Meridians in Visable Human Body Based on VOXEL-MAN System

    Institute of Scientific and Technical Information of China (English)

    刘红菊; 赵静; 严振国; 庄天戈

    2009-01-01

    利用VOXEL-MAN开发平台,在可视人体上采用管状模型建模的方法得到经络的控制点集合,并在重要控制点处放置球体模型,通过适当的插值和成熟的计算机图形技术实现基于三角面片的面绘制,配合光照模型、阴影处理,建立光滑的管状经络模型,实现经络的三维表达.

  17. Two adult human voxel phantoms based on polygon mesh surfaces; Dois fantomas construidos a partir de superficies mesh representando uma mulher adulta e um homem adulto

    Energy Technology Data Exchange (ETDEWEB)

    Cassola, Vagner F.; Kramer, Richard; Khoury, Helen J. [Universidade Federal de Pernambuco (UFPE), Recife (Brazil). Dept. de Energia Nuclear], e-mail: rkramer@uol.com.br; Lima, Vanildo J.M. [Universidade Federal de Pernambuco (UFPE), Recife (Brazil). Dept. de Anatomia

    2010-03-15

    Among computational models used in radiation protection, voxel phantoms based on computer tomographic (CT), nuclear magnetic resonance (NMR) or colour photographic images, became very popular in recent years. Although being a true to nature representation of the scanned individual the scanning is usually made in supine position, which causes a shift of internal organs towards the ribcage, a compression of the lungs and a reduction of the sagittal diameter especially in the abdominal region compared to the anatomy of a person in upright standing position, which in turn can influence absorbed or equivalent dose estimates. This study proposes a method for human phantom design using tools recently developed in the areas of computer graphics and animated films and applies them to the creation and modeling of artificial 3D human organs and tissues. Two models, a male and a female adult human phantom have been developed based on anatomical atlases, observing at the same time the anatomical specifications published by the International Commission on Radiological Protection for the male and female reference adult. The phantoms are called FAX{sub A}A (Female Adult voXel{sub A}verage-Average) and MAX{sub A}A (Male Adult voXel{sub A}verage-Average) because they represent female and male adults with average weight and average height. (author)

  18. Object Detection and Tracking-Based Camera Calibration for Normalized Human Height Estimation

    Directory of Open Access Journals (Sweden)

    Jaehoon Jung

    2016-01-01

    Full Text Available This paper presents a normalized human height estimation algorithm using an uncalibrated camera. To estimate the normalized human height, the proposed algorithm detects a moving object and performs tracking-based automatic camera calibration. The proposed method consists of three steps: (i moving human detection and tracking, (ii automatic camera calibration, and (iii human height estimation and error correction. The proposed method automatically calibrates camera by detecting moving humans and estimates the human height using error correction. The proposed method can be applied to object-based video surveillance systems and digital forensic.

  19. The effect of in situ/in vitro three-dimensional quantitative computed tomography image voxel size on the finite element model of human vertebral cancellous bone.

    Science.gov (United States)

    Lu, Yongtao; Engelke, Klaus; Glueer, Claus-C; Morlock, Michael M; Huber, Gerd

    2014-11-01

    Quantitative computed tomography-based finite element modeling technique is a promising clinical tool for the prediction of bone strength. However, quantitative computed tomography-based finite element models were created from image datasets with different image voxel sizes. The aim of this study was to investigate whether there is an influence of image voxel size on the finite element models. In all 12 thoracolumbar vertebrae were scanned prior to autopsy (in situ) using two different quantitative computed tomography scan protocols, which resulted in image datasets with two different voxel sizes (0.29 × 0.29 × 1.3 mm(3) vs 0.18 × 0.18 × 0.6 mm(3)). Eight of them were scanned after autopsy (in vitro) and the datasets were reconstructed with two voxel sizes (0.32 × 0.32 × 0.6 mm(3) vs. 0.18 × 0.18 × 0.3 mm(3)). Finite element models with cuboid volume of interest extracted from the vertebral cancellous part were created and inhomogeneous bilinear bone properties were defined. Axial compression was simulated. No effect of voxel size was detected on the apparent bone mineral density for both the in situ and in vitro cases. However, the apparent modulus and yield strength showed significant differences in the two voxel size group pairs (in situ and in vitro). In conclusion, the image voxel size may have to be considered when the finite element voxel modeling technique is used in clinical applications.

  20. Effects of CT based Voxel Phantoms on Dose Distribution Calculated with Monte Carlo Method

    Institute of Scientific and Technical Information of China (English)

    Chen Chaobin; Huang Qunying; Wu Yican

    2005-01-01

    A few CT-based voxel phantoms were produced to investigate the sensitivity of Monte Carlo simulations of X-ray beam and electron beam to the proportions of elements and the mass densities of the materials used to express the patient's anatomical structure. The human body can be well outlined by air, lung, adipose, muscle, soft bone and hard bone to calculate the dose distribution with Monte Carlo method. The effects of the calibration curves established by using various CT scanners are not clinically significant based on our investigation. The deviation from the values of cumulative dose volume histogram derived from CT-based voxel phantoms is less than 1% for the given target.

  1. Two-voxel spectroscopy with dynamic B0 shimming and flip angle adjustment at 7 T in the human motor cortex.

    Science.gov (United States)

    Lemke, Clark; Hess, Aaron; Clare, Stuart; Bachtiar, Velicia; Stagg, Charlotte; Jezzard, Peter; Emir, Uzay

    2015-07-01

    The aim of this study was to acquire high-quality in vivo (1) H spectra concurrently from two voxels at ultra-high field (7 T) without specialized hardware. To this end, an acquisition scheme was developed in which first-order shims and flip angles are dynamically updated to acquire spectra from both of the brain's motor cortices in an alternating fashion. To validate this acquisition scheme, separate, static, single-voxel acquisitions were also performed for comparison. Six subjects were examined using semi-LASER spectroscopy at 7 T. Barium titanate pads were used to increase the extent of the effective transmit field (B1 (+) ). Spectra were obtained from the hand area of both motor cortices for both acquisition schemes. LCModel was used to determine neurochemical profiles in order to examine variations between acquisition schemes and volumes of interest. The dynamic two-voxel acquisition protocol produced water linewidths (full width at half-maximum between 11.6 and 12.8 Hz) and signal-to-noise ratios similar to those from static single-voxel measurements. The concentrations of 13 individual and 3 combined metabolites with Cramér-Rao lower bounds below 30% were reliably detected for both acquisition schemes, and agreed well with previous postmortem assay and spectroscopy studies. The results show that high spectral quality from two voxels can be acquired concurrently without specialized hardware. This practical technique can be applied to many neuroscience applications.

  2. Spatial averaging of fields from half-wave dipole antennas and corresponding SAR calculations in the NORMAN human voxel model between 65 MHz and 2 GHz.

    Science.gov (United States)

    Findlay, R P; Dimbylow, P J

    2009-04-21

    If an antenna is located close to a person, the electric and magnetic fields produced by the antenna will vary in the region occupied by the human body. To obtain a mean value of the field for comparison with reference levels, the Institute of Electrical and Electronic Engineers (IEEE) and International Commission on Non-Ionizing Radiation Protection (ICNIRP) recommend spatially averaging the squares of the field strength over the height the body. This study attempts to assess the validity and accuracy of spatial averaging when used for half-wave dipoles at frequencies between 65 MHz and 2 GHz and distances of lambda/2, lambda/4 and lambda/8 from the body. The differences between mean electric field values calculated using ten field measurements and that of the true averaged value were approximately 15% in the 600 MHz to 2 GHz range. The results presented suggest that the use of modern survey equipment, which takes hundreds rather than tens of measurements, is advisable to arrive at a sufficiently accurate mean field value. Whole-body averaged and peak localized SAR values, normalized to calculated spatially averaged fields, were calculated for the NORMAN voxel phantom. It was found that the reference levels were conservative for all whole-body SAR values, but not for localized SAR, particularly in the 1-2 GHz region when the dipole was positioned very close to the body. However, if the maximum field is used for normalization of calculated SAR as opposed to the lower spatially averaged value, the reference levels provide a conservative estimate of the localized SAR basic restriction for all frequencies studied.

  3. Stimulus-Related Independent Component and Voxel-Wise Analysis of Human Brain Activity during Free Viewing of a Feature Film

    Science.gov (United States)

    Lahnakoski, Juha M.; Salmi, Juha; Jääskeläinen, Iiro P.; Lampinen, Jouko; Glerean, Enrico; Tikka, Pia; Sams, Mikko

    2012-01-01

    Understanding how the brain processes stimuli in a rich natural environment is a fundamental goal of neuroscience. Here, we showed a feature film to 10 healthy volunteers during functional magnetic resonance imaging (fMRI) of hemodynamic brain activity. We then annotated auditory and visual features of the motion picture to inform analysis of the hemodynamic data. The annotations were fitted to both voxel-wise data and brain network time courses extracted by independent component analysis (ICA). Auditory annotations correlated with two independent components (IC) disclosing two functional networks, one responding to variety of auditory stimulation and another responding preferentially to speech but parts of the network also responding to non-verbal communication. Visual feature annotations correlated with four ICs delineating visual areas according to their sensitivity to different visual stimulus features. In comparison, a separate voxel-wise general linear model based analysis disclosed brain areas preferentially responding to sound energy, speech, music, visual contrast edges, body motion and hand motion which largely overlapped the results revealed by ICA. Differences between the results of IC- and voxel-based analyses demonstrate that thorough analysis of voxel time courses is important for understanding the activity of specific sub-areas of the functional networks, while ICA is a valuable tool for revealing novel information about functional connectivity which need not be explained by the predefined model. Our results encourage the use of naturalistic stimuli and tasks in cognitive neuroimaging to study how the brain processes stimuli in rich natural environments. PMID:22496909

  4. Stimulus-related independent component and voxel-wise analysis of human brain activity during free viewing of a feature film.

    Directory of Open Access Journals (Sweden)

    Juha M Lahnakoski

    Full Text Available Understanding how the brain processes stimuli in a rich natural environment is a fundamental goal of neuroscience. Here, we showed a feature film to 10 healthy volunteers during functional magnetic resonance imaging (fMRI of hemodynamic brain activity. We then annotated auditory and visual features of the motion picture to inform analysis of the hemodynamic data. The annotations were fitted to both voxel-wise data and brain network time courses extracted by independent component analysis (ICA. Auditory annotations correlated with two independent components (IC disclosing two functional networks, one responding to variety of auditory stimulation and another responding preferentially to speech but parts of the network also responding to non-verbal communication. Visual feature annotations correlated with four ICs delineating visual areas according to their sensitivity to different visual stimulus features. In comparison, a separate voxel-wise general linear model based analysis disclosed brain areas preferentially responding to sound energy, speech, music, visual contrast edges, body motion and hand motion which largely overlapped the results revealed by ICA. Differences between the results of IC- and voxel-based analyses demonstrate that thorough analysis of voxel time courses is important for understanding the activity of specific sub-areas of the functional networks, while ICA is a valuable tool for revealing novel information about functional connectivity which need not be explained by the predefined model. Our results encourage the use of naturalistic stimuli and tasks in cognitive neuroimaging to study how the brain processes stimuli in rich natural environments.

  5. Construction tool and suitability of voxel phantom for skin dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Antunes, Paula C.G.; Siqueira, Paulo T.D.; Fonseca, Gabriel P.; Yoriyaz, Helio, E-mail: ptsiquei@ipen.b, E-mail: hyoriyaz@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    This paper describes a new software tool called 'SkinVop' which was developed to enable accurate voxel phantom skin dosimetry. A voxel phantom is a model used to describe human anatomy in a realistic way in radiation transport codes. This model is a three-dimensional representation of the human body in the form of an array of identification numbers that are arranged in a 3D matrix. Each entry in this array represents a voxel (volume element) directly associated to the units of picture resolution (pixel) of medical images. Currently, these voxel phantoms, in association with the transport code MCNP (Monte Carlo N-Particle), have provided subsidies to the planning systems used on the hospital routine, once they afford accurate and personalized estimative of dose distribution. However, these assessments are limited to geometric representations of organs and tissues in the voxel phantom, which do not discriminates some thin body structure, such as the skin. In this context, to enable accurate dosimetric skin dose assessment by the MCNP code, it was developed this new software tool that discriminates this region with thickness and localization in the voxel phantoms similar to the real. This methodology consists in manipulating the skin volume elements by segmenting and subdividing them in different thicknesses. A graphical user interface was designed to fulfill display the modified voxel model. This methodology is extremely useful once the skin dose is inaccurately assessed of current hospital system planning, justified justly by its small thickness. (author)

  6. WiFi-Based Real-Time Calibration-Free Passive Human Motion Detection.

    Science.gov (United States)

    Gong, Liangyi; Yang, Wu; Man, Dapeng; Dong, Guozhong; Yu, Miao; Lv, Jiguang

    2015-12-21

    With the rapid development of WLAN technology, wireless device-free passive human detection becomes a newly-developing technique and holds more potential to worldwide and ubiquitous smart applications. Recently, indoor fine-grained device-free passive human motion detection based on the PHY layer information is rapidly developed. Previous wireless device-free passive human detection systems either rely on deploying specialized systems with dense transmitter-receiver links or elaborate off-line training process, which blocks rapid deployment and weakens system robustness. In the paper, we explore to research a novel fine-grained real-time calibration-free device-free passive human motion via physical layer information, which is independent of indoor scenarios and needs no prior-calibration and normal profile. We investigate sensitivities of amplitude and phase to human motion, and discover that phase feature is more sensitive to human motion, especially to slow human motion. Aiming at lightweight and robust device-free passive human motion detection, we develop two novel and practical schemes: short-term averaged variance ratio (SVR) and long-term averaged variance ratio (LVR). We realize system design with commercial WiFi devices and evaluate it in typical multipath-rich indoor scenarios. As demonstrated in the experiments, our approach can achieve a high detection rate and low false positive rate.

  7. Two animated adult human voxel phantoms based on polygon mesh surfaces;Dois fantomas animados construidos a partir de superficies mesh representando um mulher adulta e um homem adulto

    Energy Technology Data Exchange (ETDEWEB)

    Cassola, Vagner F.; Kramer, Richard; Khoury, Helen J. [Universidade Federal de Pernambuco (DEN/UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear; Lima, Vanildo J.M. [Universidade Federal de Pernambuco (DA/UFPE), Recife, PE (Brazil). Dept. de Anatomia

    2009-07-01

    Among computational models used in radiation protection, voxel phantoms based on computer tomographic (CT), nuclear magnetic resonance (NMR) or colour photographic images, became very popular in recent years. Although being a true to nature representation of the scanned individual the scanning is usually made in supine position, which causes a shift of internal organs towards the ribcage, a compression of the lungs and a reduction of the sagittal diameter especially in the abdominal region compared to the anatomy of a person in upright standing position, which in turn can influence absorbed or equivalent dose estimates. This study proposes a method for human phantom design using tools recently developed in the areas of computer graphics and animated films and applies them to the creation and modelling of artificial 3 D human organs and tissues. Two animated models, a male and a female adult human phantom have been developed based on anatomical atlases, observing at the same time the anatomical specifications published by the International Commission on Radiological Protection for the male and female reference adult. The phantoms are called FAX{sub A}A (Female Adult voXel{sub A}verage-Average) and MAX{sub A}A (Male Adult voXel{sub A}verage-Average) because they represent female and male adults with average weight and average height. (author)

  8. Calibration and commutability assessment of the 1st International Standard for Diphtheria Antitoxin Human.

    Science.gov (United States)

    Stickings, Paul; Rigsby, Peter; Coombes, Laura; von Hunolstein, Christina; Ralli, Luisa; Pinto, Antonella; Sesardic, Dorothea

    2013-11-01

    The 1st International Standard for Diphtheria Antitoxin Human (coded 10/262) was established by the World Health Organization Expert Committee on Biological Standardization in 2012. This paper describes the production, characterization and calibration of the new standard which is intended for use in the standardization of assays used to measure diphtheria antibody responses in human serum. The new standard was calibrated in terms of the International Standard for Diphtheria Antitoxin Equine in an international collaborative study. A total of 8 participants from 8 different countries performed in vivo and/or in vitro toxin neutralization tests and returned data that was used to assign units to the proposed new standard. The new standard has a diphtheria antitoxin potency of 2 IU/ampoule and is predicted to be stable. A follow up study was performed to assess commutability of the new standard. The follow up study was an existing external quality assessment, modified to include the new standard. Results obtained suggest that the new standard is commutable, showing comparable behaviour to native human serum samples in the majority of the assays compared, and is therefore suitable for use as a reference preparation in assays used to measure the level of anti-diphtheria antibodies in human serum.

  9. Preparing a voxel-simulator of Alderson Rando physical phantom

    Energy Technology Data Exchange (ETDEWEB)

    Boia, Leonardo S.; Martins, Maximiano C.; Silva, Ademir X., E-mail: lboia@con.ufrj.br, E-mail: ademir@con.ufrj.br [Programa de Engenharia Nuclear (PEN/COPPE/UFRJ). Universidade Federal do Rio de Janeiro, RJ (Brazil); Salmon Junior, Helio A., E-mail: heliosalmon@coinet.com.br [COI - Clinicas Oncologicas Integradas, MD.X Barra Medical Center, Rio de Janeiro, RJ (Brazil); Soares, Alessandro F.N.S., E-mail: afacure@cnen.gov.br [Comissao Nacional de Engenharia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil)

    2011-07-01

    There are, nowadays, sorts of anthropomorphycal phantoms which are used for simulation of radiation transport by the matter and also the deposition of energy in such radiation in human tissues and organs, because an in-vitro dosimetry becomes very either complicated or even impossible in some cases. In the present work we prepared a computational phantom in voxels based on computational tomography of Rando-Alderson. This phantom is one of the most known human body simulators on the scope of ionizing radiation dosimetry, and it is used for radioprotection issues and dosimetry from radiotherapy and brachytherapy treatments as well. The preparation of a voxel simulator starts with the image acquisition by a tomograph found at COI/RJ (Clinicas Oncologicas Integradas). The images were generated with 1mm cuts and collected for analysis. After that step the images were processed in SAPDI (Sistema Automatizado de Processamento Digital de Imagem) in order to amplify the images regions intending to facilitate the task in their segmentation. SAPDI is based on parameters described by Hounsfield scale. After that, it has begun discretization of elements in IDs voxels using Scan2MCNP software - which converts images to a sequential text file containing the voxels' IDs ready to be introduced into MCNPX input; however, this set can be turned to a voxel's IDs matrix and used in other Monte Carlo codes, such as Geant4, PENELOPE and EGSnrc. Finished this step, the simulator is able to simulate with accurate geometry the physical phantom. It's possible to study a large number of cases by computational techniques of geometry's insertions of tumors and TLDs, which makes this simulator a research material useful for a lot of subjects. (author)

  10. VoxelStats: A MATLAB Package for Multi-Modal Voxel-Wise Brain Image Analysis.

    Science.gov (United States)

    Mathotaarachchi, Sulantha; Wang, Seqian; Shin, Monica; Pascoal, Tharick A; Benedet, Andrea L; Kang, Min Su; Beaudry, Thomas; Fonov, Vladimir S; Gauthier, Serge; Labbe, Aurélie; Rosa-Neto, Pedro

    2016-01-01

    In healthy individuals, behavioral outcomes are highly associated with the variability on brain regional structure or neurochemical phenotypes. Similarly, in the context of neurodegenerative conditions, neuroimaging reveals that cognitive decline is linked to the magnitude of atrophy, neurochemical declines, or concentrations of abnormal protein aggregates across brain regions. However, modeling the effects of multiple regional abnormalities as determinants of cognitive decline at the voxel level remains largely unexplored by multimodal imaging research, given the high computational cost of estimating regression models for every single voxel from various imaging modalities. VoxelStats is a voxel-wise computational framework to overcome these computational limitations and to perform statistical operations on multiple scalar variables and imaging modalities at the voxel level. VoxelStats package has been developed in Matlab(®) and supports imaging formats such as Nifti-1, ANALYZE, and MINC v2. Prebuilt functions in VoxelStats enable the user to perform voxel-wise general and generalized linear models and mixed effect models with multiple volumetric covariates. Importantly, VoxelStats can recognize scalar values or image volumes as response variables and can accommodate volumetric statistical covariates as well as their interaction effects with other variables. Furthermore, this package includes built-in functionality to perform voxel-wise receiver operating characteristic analysis and paired and unpaired group contrast analysis. Validation of VoxelStats was conducted by comparing the linear regression functionality with existing toolboxes such as glim_image and RMINC. The validation results were identical to existing methods and the additional functionality was demonstrated by generating feature case assessments (t-statistics, odds ratio, and true positive rate maps). In summary, VoxelStats expands the current methods for multimodal imaging analysis by allowing the

  11. Voxel inversion of airborne EM data

    DEFF Research Database (Denmark)

    Fiandaca, Gianluca G.; Auken, Esben; Christiansen, Anders Vest C A.V.C.;

    2013-01-01

    We present a geophysical inversion algorithm working directly in a voxel grid disconnected from the actual measuring points, which allows for straightforward integration of different data types in joint inversion, for informing geological/hydrogeological models directly and for easier incorporation...... for jointly inverting airborne and ground-based geophysical data. Furthermore, geological and groundwater models most often refer to a regular voxel grid not correlated to the geophysical model space, and incorporating the geophysical data into the geological/hydrological modelling grids is problematic. We...... present a voxel grid inversion routine that overcomes these problems and we discuss in detail the algorithm implementation....

  12. Calibrating the Human Mutation Rate via Ancestral Recombination Density in Diploid Genomes.

    Directory of Open Access Journals (Sweden)

    Mark Lipson

    2015-11-01

    Full Text Available The human mutation rate is an essential parameter for studying the evolution of our species, interpreting present-day genetic variation, and understanding the incidence of genetic disease. Nevertheless, our current estimates of the rate are uncertain. Most notably, recent approaches based on counting de novo mutations in family pedigrees have yielded significantly smaller values than classical methods based on sequence divergence. Here, we propose a new method that uses the fine-scale human recombination map to calibrate the rate of accumulation of mutations. By comparing local heterozygosity levels in diploid genomes to the genetic distance scale over which these levels change, we are able to estimate a long-term mutation rate averaged over hundreds or thousands of generations. We infer a rate of 1.61 ± 0.13 × 10-8 mutations per base per generation, which falls in between phylogenetic and pedigree-based estimates, and we suggest possible mechanisms to reconcile our estimate with previous studies. Our results support intermediate-age divergences among human populations and between humans and other great apes.

  13. Estimation of specific absorbed fractions for selected organs due to photons emitted by activity deposited in the human respiratory tract using ICRP/ICRU male voxel phantom in FLUKA.

    Science.gov (United States)

    Patni, H K; Akar, D K; Nadar, M Y; Ghare, V P; Rao, D D; Sarkar, P K

    2013-01-01

    The ICRP/ICRU adult male reference voxel phantom incorporated in Monte Carlo code FLUKA is used for estimating specific absorbed fractions (SAFs) for photons due to the presence of internal radioactive contamination in the human respiratory tract (RT). The compartments of the RT, i.e. extrathoracic (ET1 and ET2) and thoracic (bronchi, bronchioles, alveolar interstitial) regions, lymph nodes of both regions and lungs are considered as the source organs. The nine organs having high tissue weighting factors such as colon, lungs, stomach wall, breast, testis, urinary bladder, oesophagus, liver and thyroid and the compartments of the RT are considered as target organs. Eleven photon energies in the range of 15 keV to 4 MeV are considered for each source organ and the computed SAF values are presented in the form of tables. For the target organs in the proximity of the source organ including the source organ itself, the SAF values are relatively higher and decrease with increase in energy. As the distance between source and target organ increases, SAF values increase with energy and reach maxima depending on the position of the target organ with respect to the source organ. The SAF values are relatively higher for the target organs with smaller masses. Large deviations are seen in computed SAF values from the existing MIRD phantom data for most of the organs. These estimated SAF values play an important role in the estimation of equivalent dose to various target organs of a worker due to intake by inhalation pathway.

  14. The effect of voxel size on the measurement of mandibular thickness in cone-beam computed tomography

    Directory of Open Access Journals (Sweden)

    Ehsan Hekmatian

    2014-01-01

    Full Text Available Background: Cone-beam computed tomography (CBCT is a new imaging technology that has been widely used in implantology, oral and maxillofacial surgery and orthodontics. This method provides 3-D images that are composed of voxel, which is the smallest image unit, and determines image resolution. Smaller voxel is associated with the higher resolution and also greater radiation exposure. This study was aimed to find out the effect of voxel size on the measurement of mandibular thickness. Materials and Methods: Using voxel sizes of 0.30 mm and 0.15 mm, two CBCT protocols (protocol 1: Field of view (FOV of 15 cm, 85 kVp, 42 mAs, 0.15 mm voxel, 14 s scan time; protocol 2: FOV of 15 cm, 85 kVp, 10 mAs, 0.30 mm voxel, 14 s scan time were carried out on 16 dry human mandibles with permanent dentition. Mandibular thickness was measured at seven different sites (midline region, bilateral canine regions, bilateral mental foramen regions and bilateral molar regions. Analysis of variance was used for analysis of data using the Statistical Package for the Social Sciences version 20 (SPSS Inc., Chicago, IL, USA. P 0.05. Conclusion: Considering the insignificant differences of the mandibular thickness measurements using different voxel sizes, it would be more reasonable to use 0.30 mm voxel size instead of 0.15 mm voxel size to avoid unnecessary radiation exposure.

  15. Distinct Cortical Pathways for Music and Speech Revealed by Hypothesis-Free Voxel Decomposition.

    Science.gov (United States)

    Norman-Haignere, Sam; Kanwisher, Nancy G; McDermott, Josh H

    2015-12-16

    The organization of human auditory cortex remains unresolved, due in part to the small stimulus sets common to fMRI studies and the overlap of neural populations within voxels. To address these challenges, we measured fMRI responses to 165 natural sounds and inferred canonical response profiles ("components") whose weighted combinations explained voxel responses throughout auditory cortex. This analysis revealed six components, each with interpretable response characteristics despite being unconstrained by prior functional hypotheses. Four components embodied selectivity for particular acoustic features (frequency, spectrotemporal modulation, pitch). Two others exhibited pronounced selectivity for music and speech, respectively, and were not explainable by standard acoustic features. Anatomically, music and speech selectivity concentrated in distinct regions of non-primary auditory cortex. However, music selectivity was weak in raw voxel responses, and its detection required a decomposition method. Voxel decomposition identifies primary dimensions of response variation across natural sounds, revealing distinct cortical pathways for music and speech.

  16. Physiological HEPES buffer proposed as a calibrator for pH measurement in human blood.

    Science.gov (United States)

    Lang, W; Zander, R

    1999-05-01

    N-(2-hydroxyethyl)-piperazine-N'-2-ethanesulfonic acid, known as HEPES buffer, with pK in the physiological range was studied for use as an alternative to conventional phosphate buffer for the calibration of pH in modern clinical analyzers. In different series of aqueous equimolar HEPES buffer, pH was measured at 37 degrees C with a capillary glass electrode standardized previously using phosphate, and variations due to changes in total HEPES buffer concentration (0.025 to 0.320 mol/l), and NaCl (0 to 0.250 mol/l) were monitored. For 0.05 equimolar HEPES buffer without NaCl, the pH of 7.362+/-0.003 (n = 15) obtained coincided well with the reference pH (7.364) from the National Institute of Standards and Technology (NIST). In particular, in the preferred 0.05 equimolar HEPES buffer/0.110 mol/l NaCl, which is isotonic to human plasma (0.160 mol/l), and termed physiological HEPES buffer (PHB), the pH of 7.346+/-0.003 (n = 84) can be related to the calculated corresponding reference pH from NIST without liquid junction (7.374), and is also compatible with the pH measured in normal arterial blood, pH = 7.403+/-0.003 (n = 20). Hence, in the two-point calibration of clinical analyzers, PHB, which is defined operationally with respect to the glass electrode and to phosphate buffer, may be useful as a calibrator in the range of buffer adjustment control to meet the correct values for pH when measuring in blood. Whereas Na-HEPES salt is hygroscopic and does not meet the declared purity grade (> 99%), pure HEPES acid is non-hygroscopic and conforms to the manufacturer's purity grade (> or = 99%). Therefore, for easy preparation of PHB, HEPES acid is the preferred starting material.

  17. Voxel-Based LIDAR Analysis and Applications

    Science.gov (United States)

    Hagstrom, Shea T.

    One of the greatest recent changes in the field of remote sensing is the addition of high-quality Light Detection and Ranging (LIDAR) instruments. In particular, the past few decades have been greatly beneficial to these systems because of increases in data collection speed and accuracy, as well as a reduction in the costs of components. These improvements allow modern airborne instruments to resolve sub-meter details, making them ideal for a wide variety of applications. Because LIDAR uses active illumination to capture 3D information, its output is fundamentally different from other modalities. Despite this difference, LIDAR datasets are often processed using methods appropriate for 2D images and that do not take advantage of its primary virtue of 3-dimensional data. It is this problem we explore by using volumetric voxel modeling. Voxel-based analysis has been used in many applications, especially medical imaging, but rarely in traditional remote sensing. In part this is because the memory requirements are substantial when handling large areas, but with modern computing and storage this is no longer a significant impediment. Our reason for using voxels to model scenes from LIDAR data is that there are several advantages over standard triangle-based models, including better handling of overlapping surfaces and complex shapes. We show how incorporating system position information from early in the LIDAR point cloud generation process allows radiometrically-correct transmission and other novel voxel properties to be recovered. This voxelization technique is validated on simulated data using the Digital Imaging and Remote Sensing Image Generation (DIRSIG) software, a first-principles based ray-tracer developed at the Rochester Institute of Technology. Voxel-based modeling of LIDAR can be useful on its own, but we believe its primary advantage is when applied to problems where simpler surface-based 3D models conflict with the requirement of realistic geometry. To

  18. Looking forward by looking back: using historical calibration to improve forecasts of human disease vector distributions.

    Science.gov (United States)

    Acheson, Emily Sohanna; Kerr, Jeremy Thomas

    2015-03-01

    Arthropod disease vectors, most notably mosquitoes, ticks, tsetse flies, and sandflies, are strongly influenced by environmental conditions and responsible for the vast majority of global vector-borne human diseases. The most widely used statistical models to predict future vector distributions model species niches and project the models forward under future climate scenarios. Although these methods address variations in vector distributions through space, their capacity to predict changing distributions through time is far less certain. Here, we review modeling methods used to validate and forecast future distributions of arthropod vectors under the effects of climate change and outline the uses or limitations of these techniques. We then suggest a validation approach specific to temporal extrapolation models that is gaining momentum in macroecological modeling and has great potential for epidemiological modeling of disease vectors. We performed systematic searches in the Web of Science, ScienceDirect, and Google Scholar to identify peer-reviewed English journal articles that model arthropod disease vector distributions under future environment scenarios. We included studies published up to and including June, 2014. We identified 29 relevant articles for our review. The majority of these studies predicted current species niches and projected the models forward under future climate scenarios without temporal validation. Historically calibrated forecast models improve predictions of changing vector distributions by tracking known shifts through recently observed time periods. With accelerating climate change, accurate predictions of shifts in disease vectors are crucial to target vector control interventions where needs are greatest.

  19. Voxel2MCNP: software for handling voxel models for Monte Carlo radiation transport calculations.

    Science.gov (United States)

    Hegenbart, Lars; Pölz, Stefan; Benzler, Andreas; Urban, Manfred

    2012-02-01

    Voxel2MCNP is a program that sets up radiation protection scenarios with voxel models and generates corresponding input files for the Monte Carlo code MCNPX. Its technology is based on object-oriented programming, and the development is platform-independent. It has a user-friendly graphical interface including a two- and three-dimensional viewer. A row of equipment models is implemented in the program. Various voxel model file formats are supported. Applications include calculation of counting efficiency of in vivo measurement scenarios and calculation of dose coefficients for internal and external radiation scenarios. Moreover, anthropometric parameters of voxel models, for instance chest wall thickness, can be determined. Voxel2MCNP offers several methods for voxel model manipulations including image registration techniques. The authors demonstrate the validity of the program results and provide references for previous successful implementations. The authors illustrate the reliability of calculated dose conversion factors and specific absorbed fractions. Voxel2MCNP is used on a regular basis to generate virtual radiation protection scenarios at Karlsruhe Institute of Technology while further improvements and developments are ongoing.

  20. Calculations of internal and external radiation exposure based on voxel models. Final report; Berechnungen der internen und externen Strahlenexposition auf Grundlage von Voxel-Modellen. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Zankl, M. [Helmholtz Zentrum Muenchen - Deutsches Forschungszentrum fuer Gesundheit und Umwelt, Muenchen (Germany). Inst fuer Strahlenschutz; Becker, J.; Petoussi-Henss, N.; Schlattl, H.

    2012-02-15

    Dose estimations of internal and external radiation exposure were based so far on mathematical phantoms with rather simple geometrical descriptions of the human body and teh organs. Recently the mathematical phantoms are replaced by more realistic voxel models that allow a more realistic dose estimation for professional radiation exposed personnel, individuals and patients. The projects is aimed to calculate organ doses for exposure to environmental radiation, organ doses for patients during computed tomography and to develop a voxel model for pregnant (24th week of pregnancy) woman for the estimation of radiation doses for the unborn child.

  1. Dose-response calibration curves of {sup 137}Cs gamma rays for dicentric chromosome aberrations in human lymphocytes

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Wol Soon; Oh, Su Jung; Jeong, Soo Kyun; Yang, Kwang Mo [Dept. of Research center, Dong Nam Institute of Radiological and Medical Sciences, Busan (Korea, Republic of); Jeong, Min Ho [Dept. of Microbiology, Dong A University College of Medicine, Busan (Korea, Republic of)

    2012-11-15

    Recently, the increased threat of radiologically industrial accident such as radiation nondestructive inspection or destruction of nuclear accident by natural disaster such as Fukushima accident requires a greater capacity for cytogenetic biodosimetry, which is critical for clinical triage of potentially thousands of radiation-exposed individuals. Dicentric chromosome aberration analysis is the conventional means of assessing radiation exposure. Dose–response calibration curves for {sup 13}'7Cs gamma rays have been established for unstable chromosome aberrations in human peripheral blood lymphocytes in many laboratories of international biodosimetry network. In this study, therefore, we established dose– response calibration curves of our laboratory for {sup 137}Cs gamma raysaccording to the IAEA protocols for conducting the dicentric chromosome assay We established in vitro dose–response calibration curves for dicentric chromosome aberrations in human lymphocytes for{sup 13}'7Cs gamma rays in the 0 to 5 Gy range, using the maximum likelihood linear-quadratic model, Y = c+αD+βD2. The estimated coefficients of the fitted curves were within the 95% confidence intervals (CIs) and the curve fitting of dose–effect relationship data indicated a good fit to the linear-quadratic model. Hence, meaningful dose estimation from unknown sample can be determined accurately by using our laboratory’s calibration curve according to standard protocol.

  2. Uncertainty driven probabilistic voxel selection for image registration.

    Science.gov (United States)

    Oreshkin, Boris N; Arbel, Tal

    2013-10-01

    This paper presents a novel probabilistic voxel selection strategy for medical image registration in time-sensitive contexts, where the goal is aggressive voxel sampling (e.g., using less than 1% of the total number) while maintaining registration accuracy and low failure rate. We develop a Bayesian framework whereby, first, a voxel sampling probability field (VSPF) is built based on the uncertainty on the transformation parameters. We then describe a practical, multi-scale registration algorithm, where, at each optimization iteration, different voxel subsets are sampled based on the VSPF. The approach maximizes accuracy without committing to a particular fixed subset of voxels. The probabilistic sampling scheme developed is shown to manage the tradeoff between the robustness of traditional random voxel selection (by permitting more exploration) and the accuracy of fixed voxel selection (by permitting a greater proportion of informative voxels).

  3. Schizophrenia Patients Demonstrate Both Inter-Voxel Level and Intra-Voxel Level White Matter Alterations.

    Science.gov (United States)

    Zhuo, Chuanjun; Ma, Xiaolei; Qu, Hongru; Wang, Lina; Jia, Feng; Wang, Chunli

    2016-01-01

    Fractional anisotropy (FA) and mean diffusivity (MD) are the most frequently used metrics to investigate white matter impairments in mental disorders. However, these two metrics are derived from intra-voxel analyses and only reflect the diffusion properties solely within the voxel unit. Local diffusion homogeneity (LDH) is a newly developed inter-voxel metric which quantifies the local coherence of water molecule diffusion in a model-free manner. In this study, 94 schizophrenia patients and 91 sex- and age-matched healthy controls underwent diffusion tensor imaging (DTI) examinations. White matter integrity was assessed by FA, MD and LDH. Group differences in these metrics were compared using tract-based spatial statistics (TBSS). Compared with healthy controls, schizophrenia patients exhibited reduced FA and increased MD in the corpus callosum, cingulum, internal capsule, fornix and widespread superficial white matter in the frontal, parietal, occipital and temporal lobes. We also found decreased LDH in the corpus callosum, cingulum, internal capsule and fornix in schizophrenia. Our findings suggest that both intra-voxel and inter-voxel diffusion metrics are able to detect impairments in the anisotropic white matter regions, and intra-voxel diffusion metrics could detect additional impairments in the widespread isotropic white matter regions in schizophrenia.

  4. Variation in voxel value distribution and effect of time between exposures in six CBCT units.

    Science.gov (United States)

    Spin-Neto, R; Gotfredsen, E; Wenzel, A

    2014-01-01

    The aim of this study is to assess the variation in voxel value distribution in volumetric data sets obtained by six cone beam CT (CBCT) units, and the effect of time between exposures. Six CBCT units [Cranex(®) 3D (CRAN; Soredex Oy, Tuusula, Finland), Scanora(®) 3D (SCAN; Soredex Oy), NewTom™ 5G (NEWT; QR Srl, Verona, Italy), Promax(®) Dimax 3 (Planmeca Oy, Helsinki, Finland), i-CAT (Imaging Sciences International, Hatfield, PA) and 3D Accuitomo FPD80 (Morita, Kyoto, Japan)] were tested. Two volumetric data sets of a dry human skull embedded in acrylic were acquired by each CBCT unit in two sessions on separate days. Each session consisted of 20 exposures: 10 acquired with 30 min between exposures and 10 acquired immediately one after the other. CBCT data were exported as digital imaging and communications in medicine (DICOM) files and converted to text files. The text files were re-organized to contain x-, y- and z-position and grey shade for each voxel. The files were merged to contain 1 record per voxel position, including the voxel values from the 20 exposures in a session. For each voxel, subtractions were performed between Data Set 1 and the remaining 19 data sets (1 - 2, 1 - 3, etc) in a session. Means, medians, ranges and standard deviations for grey shade variation in the subtraction data sets were calculated for each unit and session. For all CBCT units, variation in voxel values was observed throughout the 20 exposures. A "fingerprint" for the grey shade variation was observed for CRAN, SCAN and NEWT. For the other units, the variation was (apparently) randomly distributed. Large discrepancies in voxel value distribution are seen in CBCT images. This variation should be considered in studies that assess minute changes in CBCT images.

  5. Modeling and analysis of caves using voxelization

    Science.gov (United States)

    Szeifert, Gábor; Szabó, Tivadar; Székely, Balázs

    2014-05-01

    Although there are many ways to create three dimensional representations of caves using modern information technology methods, modeling of caves has been challenging for researchers for a long time. One of these promising new alternative modeling methods is using voxels. We are using geodetic measurements as an input for our voxelization project. These geodetic underground surveys recorded the azimuth, altitude and distance of corner points of cave systems relative to each other. The diameter of each cave section is estimated from separate databases originating from different surveys. We have developed a simple but efficient method (it covers more than 99.9 % of the volume of the input model on the average) to convert these vector-type datasets to voxels. We have also developed software components to make visualization of the voxel and vector models easier. Since each cornerpoint position is measured relative to another cornerpoints positions, propagation of uncertainties is an important issue in case of long caves with many separate sections. We are using Monte Carlo simulations to analyze the effect of the error of each geodetic instrument possibly involved in a survey. Cross-sections of the simulated three dimensional distributions show, that even tiny uncertainties of individual measurements can result in high variation of positions that could be reduced by distributing the closing errors if such data are available. Using the results of our simulations, we can estimate cave volume and the error of the calculated cave volume depending on the complexity of the cave. Acknowledgements: the authors are grateful to Ariadne Karst and Cave Exploring Association and State Department of Environmental and Nature Protection of the Hungarian Ministry of Rural Development, Department of National Parks and Landscape Protection, Section Landscape and Cave Protection and Ecotourism for providing the cave measurement data. BS contributed as an Alexander von Humboldt Research

  6. Mapping the voxel-wise effective connectome in resting state FMRI.

    Directory of Open Access Journals (Sweden)

    Guo-Rong Wu

    Full Text Available A network approach to brain and dynamics opens new perspectives towards understanding of its function. The functional connectivity from functional MRI recordings in humans is widely explored at large scale, and recently also at the voxel level. The networks of dynamical directed connections are far less investigated, in particular at the voxel level. To reconstruct full brain effective connectivity network and study its topological organization, we present a novel approach to multivariate Granger causality which integrates information theory and the architecture of the dynamical network to efficiently select a limited number of variables. The proposed method aggregates conditional information sets according to community organization, allowing to perform Granger causality analysis avoiding redundancy and overfitting even for high-dimensional and short datasets, such as time series from individual voxels in fMRI. We for the first time depicted the voxel-wise hubs of incoming and outgoing information, called Granger causality density (GCD, as a complement to previous repertoire of functional and anatomical connectomes. Analogies with these networks have been presented in most part of default mode network; while differences suggested differences in the specific measure of centrality. Our findings could open the way to a new description of global organization and information influence of brain function. With this approach is thus feasible to study the architecture of directed networks at the voxel level and individuating hubs by investigation of degree, betweenness and clustering coefficient.

  7. Computerized MRS voxel registration and partial volume effects in single voxel 1H-MRS.

    Science.gov (United States)

    Lee, Hedok; Caparelli, Elisabeth; Li, Haifang; Mandal, Amit; Smith, S David; Zhang, Shaonan; Bilfinger, Thomas V; Benveniste, Helene

    2013-09-01

    Partial volume effects in proton magnetic resonance spectroscopy in the brain have been studied previously in terms of proper water concentration calculations, but there is a lack of disclosure in terms of voxel placement techniques that would affect the calculations. The purpose of this study is to facilitate a fully automated MRS voxel registration method which is time efficient, accurate, and can be extended to all imaging modalities. A total of thirteen healthy adults underwent single voxel 1H-MRS scans in 3.0T MRI scanners. Transposition of a MRS voxel onto an anatomical scan is derived along with a full calculation of water concentration with a correction term to account for the partial volume effects. Five metabolites (tNAA, Glx, tCr, mI, and tCho) known to yield high reliability are studied. Pearson's correlation analyses between tissue volume fractions and metabolite concentrations were statistically significant in parietal (tCr, Glx, and tNAA) lobe and occipital lobe (tNAA). MRS voxel overlaps quantified by dice metric over repeated visits yielded 60%~70% and coefficients of variance in metabolites concentration were 4%~10%. These findings reiterate an importance of considering the partial volume effects when tissue water is used as an internal concentration reference so as to avoid misinterpreting a morphometric difference as a metabolic difference.

  8. Automating the segmentation of medical images for the production of voxel tomographic computational models.

    Science.gov (United States)

    Caon, M; Mohyla, J

    2001-12-01

    Radiation dosimetry for the diagnostic medical imaging procedures performed on humans requires anatomically accurate, computational models. These may be constructed from medical images as voxel-based tomographic models. However, they are time consuming to produce and as a consequence, there are few available. This paper discusses the emergence of semi-automatic segmentation techniques and describes an application (iRAD) written in Microsoft Visual Basic that allows the bitmap of a medical image to be segmented interactively and semi-automatically while displayed in Microsoft Excel. iRAD will decrease the time required to construct voxel models.

  9. Influence of voxel size on specific absorbed fractions and S-values in a mouse voxel phantom.

    Science.gov (United States)

    Mohammadi, A; Kinase, S

    2011-02-01

    Photon and electron specific absorbed fractions (SAFs) and S-values have been evaluated using mouse voxel phantoms. In voxel phantoms, it is important to choose the voxel size carefully since it affects the accuracy of results. In this study, two mouse voxel phantoms were constructed, with cubic voxels, one with 0.1-mm sides and the other with 0.4-mm sides. The sources were considered to be distributed uniformly in the main organs and the radiation transport was simulated using the Monte Carlo code EGS4. It was found that the effect of voxel size on SAFs for self-irradiation was not high (voxel size was investigated on S-values for some beta emitters such as (131)I, (153)Sm, (188)Re and (90)Y.

  10. Investigation of Nonuniform Dose Voxel Geometry in Monte Carlo Calculations.

    Science.gov (United States)

    Yuan, Jiankui; Chen, Quan; Brindle, James; Zheng, Yiran; Lo, Simon; Sohn, Jason; Wessels, Barry

    2015-08-01

    The purpose of this work is to investigate the efficacy of using multi-resolution nonuniform dose voxel geometry in Monte Carlo (MC) simulations. An in-house MC code based on the dose planning method MC code was developed in C++ to accommodate the nonuniform dose voxel geometry package since general purpose MC codes use their own coupled geometry packages. We devised the package in a manner that the entire calculation volume was first divided into a coarse mesh and then the coarse mesh was subdivided into nonuniform voxels with variable voxel sizes based on density difference. We name this approach as multi-resolution subdivision (MRS). It generates larger voxels in small density gradient regions and smaller voxels in large density gradient regions. To take into account the large dose gradients due to the beam penumbra, the nonuniform voxels can be further split using ray tracing starting from the beam edges. The accuracy of the implementation of the algorithm was verified by comparing with the data published by Rogers and Mohan. The discrepancy was found to be 1% to 2%, with a maximum of 3% at the interfaces. Two clinical cases were used to investigate the efficacy of nonuniform voxel geometry in the MC code. Applying our MRS approach, we started with the initial voxel size of 5 × 5 × 3 mm(3), which was further divided into smaller voxels. The smallest voxel size was 1.25 × 1.25 × 3 mm(3). We found that the simulation time per history for the nonuniform voxels is about 30% to 40% faster than the uniform fine voxels (1.25 × 1.25 × 3 mm(3)) while maintaining similar accuracy.

  11. Calibration method for a in vivo measurement system using mathematical simulation of the radiation source and the detector; Metodo de calibracao de um sistema de medida in vivo atraves da simulacao matematica da fonte de radiacao e do detector

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, John

    1998-12-31

    A Monte Carlo program which uses a voxel phantom has been developed to simulate in vivo measurement systems for calibration purposes. The calibration method presented here employs a mathematical phantom, produced in the form of volume elements (voxels), obtained through Magnetic Resonance Images of the human body. The calibration method uses the Monte Carlo technique to simulate the tissue contamination, the transport of the photons through the tissues and the detection of the radiation. The program simulates the transport and detection of photons between 0.035 and 2 MeV and uses, for the body representation, a voxel phantom with a format of 871 slices each of 277 x 148 picture elements. The Monte Carlo code was applied to the calibration of in vivo systems and to estimate differences in counting efficiencies between homogeneous and non-homogeneous radionuclide distributions in the lung. Calculations show a factor of 20 between deposition of {sup 241} Am at the back compared with the front of the lung. The program was also used to estimate the {sup 137} Cs body burden of an internally contaminated individual, counted with an 8 x 4 Nal (TI) detector and an {sup 241} Am body burden of an internally contaminated individual, who was counted using a planar germanium detector. (author) 24 refs., 38 figs., 23 tabs.

  12. Voxel2MCNP: a framework for modeling, simulation and evaluation of radiation transport scenarios for Monte Carlo codes.

    Science.gov (United States)

    Pölz, Stefan; Laubersheimer, Sven; Eberhardt, Jakob S; Harrendorf, Marco A; Keck, Thomas; Benzler, Andreas; Breustedt, Bastian

    2013-08-21

    The basic idea of Voxel2MCNP is to provide a framework supporting users in modeling radiation transport scenarios using voxel phantoms and other geometric models, generating corresponding input for the Monte Carlo code MCNPX, and evaluating simulation output. Applications at Karlsruhe Institute of Technology are primarily whole and partial body counter calibration and calculation of dose conversion coefficients. A new generic data model describing data related to radiation transport, including phantom and detector geometries and their properties, sources, tallies and materials, has been developed. It is modular and generally independent of the targeted Monte Carlo code. The data model has been implemented as an XML-based file format to facilitate data exchange, and integrated with Voxel2MCNP to provide a common interface for modeling, visualization, and evaluation of data. Also, extensions to allow compatibility with several file formats, such as ENSDF for nuclear structure properties and radioactive decay data, SimpleGeo for solid geometry modeling, ImageJ for voxel lattices, and MCNPX's MCTAL for simulation results have been added. The framework is presented and discussed in this paper and example workflows for body counter calibration and calculation of dose conversion coefficients is given to illustrate its application.

  13. Multi-initialized States Referred Work Parameter Calibration for Gaze Tracking Human-Robot Interaction

    Directory of Open Access Journals (Sweden)

    Qijie Zhao

    2012-09-01

    Full Text Available In order to adaptively calibrate the work parameters in the infrared‐TV based eye gaze tracking Human‐Robot Interaction (HRI system, a kind of gaze direction sensing model has been provided for detecting the eye gaze identified parameters. We paid more attention to situations where the user’s head was in a different position to the interaction interface. Furthermore, the algorithm for automatically correcting work parameters of the system has also been put up by defining certain initial reference system states and analysing the historical information of the interaction between a user and the system. Moreover, considering some application cases and factors, and relying on minimum error rate Bayesian decision‐making theory, a mechanism for identifying system state and adaptively calibrating parameters has been proposed. Finally, some experiments have been done with the established system and the results suggest that the proposed mechanism and algorithm can identify the system work state in multi‐ situations, and can automatically correct the work parameters to meet the demands of a gaze tracking HRI system.

  14. The reference phantoms: voxel vs polygon.

    Science.gov (United States)

    Kim, C H; Yeom, Y S; Nguyen, T T; Wang, Z J; Kim, H S; Han, M C; Lee, J K; Zankl, M; Petoussi-Henss, N; Bolch, W E; Lee, C; Chung, B S

    2016-06-01

    The International Commission on Radiological Protection (ICRP) reference male and female adult phantoms, described in Publication 110, are voxel phantoms based on whole-body computed tomography scans of a male and a female patient, respectively. The voxel in-plane resolution and the slice thickness, of the order of a few millimetres, are insufficient for proper segmentation of smaller tissues such as the lens of the eye, the skin, and the walls of some organs. The calculated doses for these tissues therefore present some limitations, particularly for weakly penetrating radiation. Similarly, the Publication 110 phantoms cannot represent 8-40-µm-thick target regions in respiratory or alimentary tract organs. Separate stylised models have been used to represent these tissues for calculation of the ICRP reference dose coefficients (DCs). ICRP Committee 2 recently initiated a research project, the ultimate goal of which is to convert the Publication 110 phantoms to a high-quality polygon-mesh (PM) format, including all source and target regions, even those of the 8-40-µm-thick alimentary and respiratory tract organs. It is expected that the converted phantoms would lead to the same or very similar DCs as the Publication 110 reference phantoms for penetrating radiation and, at the same time, provide more accurate DCs for weakly penetrating radiation and small tissues. Additionally, the reference phantoms in the PM format would be easily deformable and, as such, could serve as a starting point to create phantoms of various postures for use, for example, in accidental dose calculations. This paper will discuss the current progress of the phantom conversion project and its significance for ICRP DC calculations.

  15. Voxel Advanced Digital-Manufacturing for Earth and Regolith in Space Project

    Science.gov (United States)

    Zeitlin, Nancy; Mueller, Robert P.

    2015-01-01

    A voxel is a discrete three-dimensional (3D) element of material that is used to construct a larger 3D object. It is the 3D equivalent of a pixel. This project will conceptualize and study various approaches in order to develop a proof of concept 3D printing device that utilizes regolith as the material of the voxels. The goal is to develop a digital printer head capable of placing discrete self-aligning voxels in additive layers in order to fabricate small parts that can be given structural integrity through a post-printing sintering or other binding process. The quicker speeds possible with the voxel 3D printing approach along with the utilization of regolith material as the substrate will advance the use of this technology to applications for In-Situ Resource Utilization (ISRU), which is key to reducing logistics from Earth to Space, thus making long-duration human exploration missions to other celestial bodies more possible.

  16. Sparse and Adaptive Diffusion Dictionary (SADD) for recovering intra-voxel white matter structure.

    Science.gov (United States)

    Aranda, Ramon; Ramirez-Manzanares, Alonso; Rivera, Mariano

    2015-12-01

    On the analysis of the Diffusion-Weighted Magnetic Resonance Images, multi-compartment models overcome the limitations of the well-known Diffusion Tensor model for fitting in vivo brain axonal orientations at voxels with fiber crossings, branching, kissing or bifurcations. Some successful multi-compartment methods are based on diffusion dictionaries. The diffusion dictionary-based methods assume that the observed Magnetic Resonance signal at each voxel is a linear combination of the fixed dictionary elements (dictionary atoms). The atoms are fixed along different orientations and diffusivity profiles. In this work, we present a sparse and adaptive diffusion dictionary method based on the Diffusion Basis Functions Model to estimate in vivo brain axonal fiber populations. Our proposal overcomes the following limitations of the diffusion dictionary-based methods: the limited angular resolution and the fixed shapes for the atom set. We propose to iteratively re-estimate the orientations and the diffusivity profile of the atoms independently at each voxel by using a simplified and easier-to-solve mathematical approach. As a result, we improve the fitting of the Diffusion-Weighted Magnetic Resonance signal. The advantages with respect to the former Diffusion Basis Functions method are demonstrated on the synthetic data-set used on the 2012 HARDI Reconstruction Challenge and in vivo human data. We demonstrate that improvements obtained in the intra-voxel fiber structure estimations benefit brain research allowing to obtain better tractography estimations. Hence, these improvements result in an accurate computation of the brain connectivity patterns.

  17. UV determination of epinephrine, uric acid, and acetaminophen in pharmaceutical formulations and some human body fluids using multivariate calibration

    Directory of Open Access Journals (Sweden)

    Hanieh Montaseri

    2014-01-01

    Full Text Available In this work, a spectrophotometric methodology was applied in order to determine epinephrine (EP, uric acid (UA, and acetaminophen (AC in pharmaceutical formulations and spiked human serum, plasma, and urine by using a multivariate approach. Multivariate calibration methods such as partial least squares (PLS methods and its derivates were used to obtain a model for simultaneous determination of EP, UA and AC with good figures of merit and mixture design was in the range of 1.8 - 35.3, 1.7 - 16.8, and 1.5 - 12.1 µg mL-1. The 2nd derivate PLS showed recoveries of 95.3 - 103.3, 93.3 - 104.0, and 94.0 - 105.5 µg mL-1 for EP, UA, and AC, respectively.

  18. All about FAX: a Female Adult voXel phantom for Monte Carlo calculation in radiation protection dosimetry.

    Science.gov (United States)

    Kramer, R; Khoury, H J; Vieira, J W; Loureiro, E C M; Lima, V J M; Lima, F R A; Hoff, G

    2004-12-01

    The International Commission on Radiological Protection (ICRP) has created a task group on dose calculations, which, among other objectives, should replace the currently used mathematical MIRD phantoms by voxel phantoms. Voxel phantoms are based on digital images recorded from scanning of real persons by computed tomography or magnetic resonance imaging (MRI). Compared to the mathematical MIRD phantoms, voxel phantoms are true to the natural representations of a human body. Connected to a radiation transport code, voxel phantoms serve as virtual humans for which equivalent dose to organs and tissues from exposure to ionizing radiation can be calculated. The principal database for the construction of the FAX (Female Adult voXel) phantom consisted of 151 CT images recorded from scanning of trunk and head of a female patient, whose body weight and height were close to the corresponding data recommended by the ICRP in Publication 89. All 22 organs and tissues at risk, except for the red bone marrow and the osteogenic cells on the endosteal surface of bone ('bone surface'), have been segmented manually with a technique recently developed at the Departamento de Energia Nuclear of the UFPE in Recife, Brazil. After segmentation the volumes of the organs and tissues have been adjusted to agree with the organ and tissue masses recommended by ICRP for the Reference Adult Female in Publication 89. Comparisons have been made with the organ and tissue masses of the mathematical EVA phantom, as well as with the corresponding data for other female voxel phantoms. The three-dimensional matrix of the segmented images has eventually been connected to the EGS4 Monte Carlo code. Effective dose conversion coefficients have been calculated for exposures to photons, and compared to data determined for the mathematical MIRD-type phantoms, as well as for other voxel phantoms.

  19. Dating the time of birth: A radiocarbon calibration curve for human eye-lens crystallines

    DEFF Research Database (Denmark)

    Kjeldsen, Henrik; Heinemeier, Jan; Heegaard, Steffen;

    2010-01-01

    Radiocarbon bomb-pulse dating has been used to measure the formation age of human eye-lens crystallines. Lens crystallines are special proteins in the eye-lens that consist of virtually inert tissue. The experimental data show that the radiocarbon ages to a large extent reflect the time of birth...

  20. ODVBA: optimally-discriminative voxel-based analysis.

    Science.gov (United States)

    Zhang, Tianhao; Davatzikos, Christos

    2011-08-01

    Gaussian smoothing of images prior to applying voxel-based statistics is an important step in voxel-based analysis and statistical parametric mapping (VBA-SPM) and is used to account for registration errors, to Gaussianize the data and to integrate imaging signals from a region around each voxel. However, it has also become a limitation of VBA-SPM based methods, since it is often chosen empirically and lacks spatial adaptivity to the shape and spatial extent of the region of interest, such as a region of atrophy or functional activity. In this paper, we propose a new framework, named optimally-discriminative voxel-based analysis (ODVBA), for determining the optimal spatially adaptive smoothing of images, followed by applying voxel-based group analysis. In ODVBA, nonnegative discriminative projection is applied regionally to get the direction that best discriminates between two groups, e.g., patients and controls; this direction is equivalent to local filtering by an optimal kernel whose coefficients define the optimally discriminative direction. By considering all the neighborhoods that contain a given voxel, we then compose this information to produce the statistic for each voxel. Finally, permutation tests are used to obtain a statistical parametric map of group differences. ODVBA has been evaluated using simulated data in which the ground truth is known and with data from an Alzheimer's disease (AD) study. The experimental results have shown that the proposed ODVBA can precisely describe the shape and location of structural abnormality.

  1. Blood groups and human groups: collecting and calibrating genetic data after World War Two.

    Science.gov (United States)

    Bangham, Jenny

    2014-09-01

    Arthur Mourant's The Distribution of the Human Blood Groups (1954) was an "indispensable" reference book on the "anthropology of blood groups" containing a vast collection of human genetic data. It was based on the results of blood-grouping tests carried out on half-a-million people and drew together studies on diverse populations around the world: from rural communities, to religious exiles, to volunteer transfusion donors. This paper pieces together sequential stages in the production of a small fraction of the blood-group data in Mourant's book, to examine how he and his colleagues made genetic data from people. Using sources from several collecting projects, I follow how blood was encountered, how it was inscribed, and how it was turned into a laboratory resource. I trace Mourant's analytical and representational strategies to make blood groups both credibly 'genetic' and understood as relevant to human ancestry, race and history. In this story, 'populations' were not simply given, but were produced through public health, colonial and post-colonial institutions, and by the labour and expertise of subjects, assistants and mediators. Genetic data were not self-evidently 'biological', but were shaped by existing historical and geographical identities, by political relationships, and by notions of kinship and belonging.

  2. Development of a voxel phantom specific for simulation of eye brachytherapy; Desenvolvimeto de um fantoma de voxel especifico para simulacao de braquiterapia ocular

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Marcilio S.; Lima, Fernando R.A., E-mail: msilveira.fisica@gmail.com, E-mail: falima@cnen.gov.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil); Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Energia Nuclear; Vieira, Jose W., E-mail: jose-wilson59@live.com [lnstituto Federal de Educacao, Ciencia e Tecnologia de Pernambuco (IFPE), Recife, PE (Brazil)

    2013-11-01

    The ophthalmic brachytherapy involves inserting a plate with seeds of radioactive material in the patient's eye for the treatment of tumors. The radiation dose to be taken by the patient is prescribed by physicians and time of application of the material is calculated from calibration curves supplied by the manufacturers of the plates. To estimate the dose absorbed by the patient, in a series of diagnostic tests, it is necessary to perform simulations using a computational model of exposure. These models are composed primarily by a anthropomorphic phantom, and a Monte Carlo code. The coupling of a phantom voxel whole body to a Monte Carlo code is a complex process because the computer model simulations with exposure takes time, knowledge of the code used and various adjustments to be implemented. The problem is aggravated even more complex when you want to radiate one region of the body. In this work we developed a phantom, specifically the region containing the eyeball, from MASH (Male Adult voxel). This model was coupled to the Monte Carlo code EGSnrc (Electron Gamma Shower) together with an algorithm simulator source of I-125 , considering only its effect of higher energy range.

  3. Calibration uncertainty

    DEFF Research Database (Denmark)

    Heydorn, Kaj; Anglov, Thomas

    2002-01-01

    Methods recommended by the International Standardization Organisation and Eurachem are not satisfactory for the correct estimation of calibration uncertainty. A novel approach is introduced and tested on actual calibration data for the determination of Pb by ICP-AES. The improved calibration unce...

  4. Determination of sulpiride in human urine using excitation-emission matrix fluorescence coupled with second-order calibration.

    Science.gov (United States)

    Nie, Jin-Fang; Wu, Hai-Long; Xia, A-Lin; Zhu, Shao-Hua; Bian, Ying-Chao; Li, Shu-Fang; Yu, Ru-Qin

    2007-12-01

    This paper proposes a new and effective approach for the quantitative analysis of sulpiride, a significant antipsychotic drug, in human urine samples by the incorporation of excitation-emission matrix (EEM) fluorescence and second-order calibration methodologies based on the alternating fitting residue (AFR) and self-weighted alternating trilinear decomposition (SWATLD) algorithms. With the application of a second-order advantage, the proposed strategy could be utilized for a direct concentration determination of sulpiride with a simple pretreatment step, even in the presence of serious natural fluorescent interferences. The average recoveries of sulpiride in complex urine samples by using AFR and SWATLD with an estimated component number of three were 101.2 +/- 2.1 and 94.4 +/- 0.7%, respectively. Moreover, the accuracy of the two algorithms was also evaluated through elliptical joint confidence region (EJCR) tests as well as the figures of merit, such as sensitivity (SEN), selectivity (SEL) and limit of detection (LOD). The experimental results demonstrated that both algorithms, as promising quantitative alternatives, have been satisfactorily applied to the determination of sulpiride in human urine, but the performance of AFR was slightly better than that of SWATLD.

  5. Voxel-by-voxel analysis of brain SPECT perfusion in Fibromyalgia

    Science.gov (United States)

    Guedj, Eric; Taïeb, David; Cammilleri, Serge; Lussato, David; de Laforte, Catherine; Niboyet, Jean; Mundler, Olivier

    2007-02-01

    We evaluated brain perfusion SPECT at rest, without noxious stiumuli, in a homogeneous group of hyperalgesic FM patients. We performed a voxel-based analysis in comparison to a control group, matched for age and gender. Under such conditions, we made the assumption that significant cerebral perfusion abnormalities could be demonstrated, evidencing altered cerebral processing associated with spontaneous pain in FM patients. The secondary objective was to study the reversibility and the prognostic value of such possible perfusion abnormalities under specific treatment. Eighteen hyperalgesic FM women (mean age 48 yr; range 25-63 yr; ACR criteria) and 10 healthy women matched for age were enrolled in the study. A voxel-by-voxel group analysis was performed using SPM2 ( ppain care unit. A second SPECT was performed a month later after specific treatment by Ketamine. Compared to control subjects, we observed individual brain SPECT abnormalities in FM patients, confirmed by SPM2 analysis with hyperperfusion of the somatosensory cortex and hypoperfusion of the frontal, cingulate, medial temporal and cerebellar cortices. We also found that a medial frontal and anterior cingulate hypoperfusions were highly predictive (PPV=83%; NPV=91%) of non-response on Ketamine, and that only responders showed significant modification of brain perfusion, after treatment. In the present study performed without noxious stimuli in hyperalgesic FM patients, we found significant hyperperfusion in regions of the brain known to be involved in sensory dimension of pain processing and significant hypoperfusion in areas assumed to be associated with the affective dimension. As current pharmacological and non-pharmacological therapies act differently on both components of pain, we hypothesize that SPECT could be a valuable and readily available tool to guide individual therapeutic strategy and provide objective follow-up of pain-processing recovery under treatment.

  6. Voxel-by-voxel analysis of brain SPECT perfusion in Fibromyalgia

    Energy Technology Data Exchange (ETDEWEB)

    Guedj, Eric [Service Central de Biophysique et de Medecine Nucleaire, AP-HM Timone, Marseille (France)]. E-mail: eric.guedj@ap-hm.fr; Taieb, David [Service Central de Biophysique et de Medecine Nucleaire, AP-HM Timone, Marseille (France); Cammilleri, Serge [Service Central de Biophysique et de Medecine Nucleaire, AP-HM Timone, Marseille (France); Lussato, David [Service Central de Biophysique et de Medecine Nucleaire, AP-HM Timone, Marseille (France); Laforte, Catherine de [Service Central de Biophysique et de Medecine Nucleaire, AP-HM Timone, Marseille (France); Niboyet, Jean [Unite d' Etude et de Traitement de la Douleur, Clinique La Phoceanne, Marseille (France); Mundler, Olivier [Service Central de Biophysique et de Medecine Nucleaire, AP-HM Timone, Marseille (France)

    2007-02-01

    We evaluated brain perfusion SPECT at rest, without noxious stiumuli, in a homogeneous group of hyperalgesic FM patients. We performed a voxel-based analysis in comparison to a control group, matched for age and gender. Under such conditions, we made the assumption that significant cerebral perfusion abnormalities could be demonstrated, evidencing altered cerebral processing associated with spontaneous pain in FM patients. The secondary objective was to study the reversibility and the prognostic value of such possible perfusion abnormalities under specific treatment. Eighteen hyperalgesic FM women (mean age 48 yr; range 25-63 yr; ACR criteria) and 10 healthy women matched for age were enrolled in the study. A voxel-by-voxel group analysis was performed using SPM2 (p<0.05, corrected for multiple comparisons). All brain SPECT were performed before any change was made in therapy in the pain care unit. A second SPECT was performed a month later after specific treatment by Ketamine. Compared to control subjects, we observed individual brain SPECT abnormalities in FM patients, confirmed by SPM2 analysis with hyperperfusion of the somatosensory cortex and hypoperfusion of the frontal, cingulate, medial temporal and cerebellar cortices. We also found that a medial frontal and anterior cingulate hypoperfusions were highly predictive (PPV=83%; NPV=91%) of non-response on Ketamine, and that only responders showed significant modification of brain perfusion, after treatment. In the present study performed without noxious stimuli in hyperalgesic FM patients, we found significant hyperperfusion in regions of the brain known to be involved in sensory dimension of pain processing and significant hypoperfusion in areas assumed to be associated with the affective dimension. As current pharmacological and non-pharmacological therapies act differently on both components of pain, we hypothesize that SPECT could be a valuable and readily available tool to guide individual therapeutic

  7. The creation of voxel phantoms for the purpose of environmental dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Caffrey, E.; Higley, K. [Oregon State University (United States)

    2014-07-01

    Basic geometric shapes have long been used as the standard for calculating radiation dose rates in non-human biota (NHB). Regulation standards have seen a shift recently, towards protection of NHB as its own endpoint. As such, there has been a growing interest in improving the calculations for NHB dose rates. To address calls for additional data, the development of voxelized models for the International Commission on Radiological Protection's (ICRP) twelve reference animal and plants (RAP) has been undertaken. Voxel models of a crab (Metacarcinus magister), flatfish (Pleuronectiformes), trout (Oncorhynchus mykiss), worm (Lumbricina), honey bee (Apis), frog (Anura), and rat, (Rattus) have been created to date. The purpose of this submission is to describe the processes of creating these voxel phantoms from radiological imaging data (i.e., Computed Tomography (CT), Magnetic Resonance Imaging (MRI), etc.). CT/MRI images of the organism are obtained and uploaded into a software package capable of segmenting the images (3D Doctor was used for the crab, flatfish, trout, worm, and honey bee). On each image slice, individual organs and other relevant anatomical features (e.g. bones or other structural tissues) are identified and segmented. Once segmentation is complete, a boundary file that describes the positioning of the organs and tissues in lattice geometry format is exported into software called Voxelizer, created by the Human Monitoring Laboratory of Canada. This software writes the boundary file geometry into an input file for Monte Carlo N-Particle (MCNP) based simulations. The user can then add appropriate materials, densities, and a desired source term. These simulations yield absorbed fraction (AF) values that are used in subsequent dose calculations with environmental concentration data. AFs are now available for the crab, flatfish, trout, worm, and honey bee at twelve photon and nine electron energies, consistent with ICRP AFs for human dosimetry

  8. Geometric features for voxel-based surface recognition

    OpenAIRE

    Yarotsky, Dmitry

    2017-01-01

    We introduce a library of geometric voxel features for CAD surface recognition/retrieval tasks. Our features include local versions of the intrinsic volumes (the usual 3D volume, surface area, integrated mean and Gaussian curvature) and a few closely related quantities. We also compute Haar wavelet and statistical distribution features by aggregating raw voxel features. We apply our features to object classification on the ESB data set and demonstrate accurate results with a small number of s...

  9. Linguistic Summarization of Video for Fall Detection Using Voxel Person and Fuzzy Logic.

    Science.gov (United States)

    Anderson, Derek; Luke, Robert H; Keller, James M; Skubic, Marjorie; Rantz, Marilyn; Aud, Myra

    2009-01-01

    In this paper, we present a method for recognizing human activity from linguistic summarizations of temporal fuzzy inference curves representing the states of a three-dimensional object called voxel person. A hierarchy of fuzzy logic is used, where the output from each level is summarized and fed into the next level. We present a two level model for fall detection. The first level infers the states of the person at each image. The second level operates on linguistic summarizations of voxel person's states and inference regarding activity is performed. The rules used for fall detection were designed under the supervision of nurses to ensure that they reflect the manner in which elders perform these activities. The proposed framework is extremely flexible. Rules can be modified, added, or removed, allowing for per-resident customization based on knowledge about their cognitive and physical ability.

  10. Voxel-based texture analysis of the brain.

    Science.gov (United States)

    Maani, Rouzbeh; Yang, Yee Hong; Kalra, Sanjay

    2015-01-01

    This paper presents a novel voxel-based method for texture analysis of brain images. Texture analysis is a powerful quantitative approach for analyzing voxel intensities and their interrelationships, but has been thus far limited to analyzing regions of interest. The proposed method provides a 3D statistical map comparing texture features on a voxel-by-voxel basis. The validity of the method was examined on artificially generated effects as well as on real MRI data in Alzheimer's Disease (AD). The artificially generated effects included hyperintense and hypointense signals added to T1-weighted brain MRIs from 30 healthy subjects. The AD dataset included 30 patients with AD and 30 age/sex matched healthy control subjects. The proposed method detected artificial effects with high accuracy and revealed statistically significant differences between the AD and control groups. This paper extends the usage of texture analysis beyond the current region of interest analysis to voxel-by-voxel 3D statistical mapping and provides a hypothesis-free analysis tool to study cerebral pathology in neurological diseases.

  11. {sup 14}C age determination for human bones during the Yayoi period - the calibration ambiguity around 2400 BP and the marine reservoir effect

    Energy Technology Data Exchange (ETDEWEB)

    Mihara, S. E-mail: cs200027@scs.kyushu-u.ac.jp; Miyamoto, K.; Nakamura, T.; Koike, H

    2004-08-01

    {sup 14}C ages for Japanese prehistoric samples from the Latest Jomon period to the early Yayoi period have a calibration ambiguity for dates around 2400 BP. It is also necessary to correct for the marine reservoir effect on {sup 14}C ages of human bone samples from people who consumed marine food as a protein source. The Ohtomo site in western Japan, is a cemetery site used from the end of the Latest Jomon period to the Kofun period, provide a useful archaeological chronology. Human bones found in dolmen burials, jar burials and cist burials. In this study, we determined the {sup 14}C ages of human bone samples and calculated the marine reservoir effect, using diet analysis based on carbon and nitrogen stable isotopes. Diet analysis showed that these people obtained from 40% to 60% of their protein from marine sources. Their {sup 14}C ages with calibration and marine reservoir correction were serially matched with the archaeological chronology.

  12. Laser-induced forward transfer (LIFT) of congruent voxels

    Energy Technology Data Exchange (ETDEWEB)

    Piqué, Alberto, E-mail: pique@nrl.navy.mil [Materials Science and Technology Division, Code 6364, Naval Research Laboratory, Washington, DC 20375 (United States); Kim, Heungsoo; Auyeung, Raymond C.Y.; Beniam, Iyoel [Materials Science and Technology Division, Code 6364, Naval Research Laboratory, Washington, DC 20375 (United States); Breckenfeld, Eric [National Research Council Fellow at the Naval Research Laboratory, Washington, DC 20375 (United States)

    2016-06-30

    Highlights: • Laser-induced forward transfer (LIFT) is demonstrated with high viscosity Ag nanopaste. • Under the right conditions (viscosity and fluence) the transfer of congruent voxels was achieved. • For viscosities under 100 Pa s, congruent voxel transfer of silver nano-suspensions is only possible under a very narrow range of conditions. • For viscosities over 100 Pa s, congruent voxel transfer of silver nano-pastes works over a wider range of fluences, donor substrate thickness, gap distances and voxel areas. • The laser transfer of congruent voxels can be used for printing electronic patterns in particular interconnects. - Abstract: Laser-induced forward transfer (LIFT) of functional materials offers unique advantages and capabilities for the rapid prototyping of electronic, optical and sensor elements. The use of LIFT for printing high viscosity metallic nano-inks and nano-pastes can be optimized for the transfer of voxels congruent with the shape of the laser pulse, forming thin film-like structures non-lithographically. These processes are capable of printing patterns with excellent lateral resolution and thickness uniformity typically found in 3-dimensional stacked assemblies, MEMS-like structures and free-standing interconnects. However, in order to achieve congruent voxel transfer with LIFT, the particle size and viscosity of the ink or paste suspensions must be adjusted to minimize variations due to wetting and drying effects. When LIFT is carried out with high-viscosity nano-suspensions, the printed voxel size and shape become controllable parameters, allowing the printing of thin-film like structures whose shape is determined by the spatial distribution of the laser pulse. The result is a new level of parallelization beyond current serial direct-write processes whereby the geometry of each printed voxel can be optimized according to the pattern design. This work shows how LIFT of congruent voxels can be applied to the fabrication of 2D

  13. Quantitative fluorescence kinetic analysis of NADH and FAD in human plasma using three- and four-way calibration methods capable of providing the second-order advantage

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Chao [School of Chemistry and Chemical Engineering, Guizhou University, Guiyang 550025 (China); Wu, Hai-Long, E-mail: hlwu@hnu.edu.cn [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China); Zhou, Chang; Xiang, Shou-Xia; Zhang, Xiao-Hua; Yu, Yong-Jie; Yu, Ru-Qin [State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China)

    2016-03-03

    The metabolic coenzymes reduced nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) are the primary electron donor and acceptor respectively, participate in almost all biological metabolic pathways. This study develops a novel method for the quantitative kinetic analysis of the degradation reaction of NADH and the formation reaction of FAD in human plasma containing an uncalibrated interferent, by using three-way calibration based on multi-way fluorescence technique. In the three-way analysis, by using the calibration set in a static manner, we directly predicted the concentrations of both analytes in the mixture at any time after the start of their reactions, even in the presence of an uncalibrated spectral interferent and a varying background interferent. The satisfactory quantitative results indicate that the proposed method allows one to directly monitor the concentration of each analyte in the mixture as the function of time in real-time and nondestructively, instead of determining the concentration after the analytical separation. Thereafter, we fitted the first-order rate law to their concentration data throughout their reactions. Additionally, a four-way calibration procedure is developed as an alternative for highly collinear systems. The results of the four-way analysis confirmed the results of the three-way analysis and revealed that both the degradation reaction of NADH and the formation reaction of FAD in human plasma fit the first-order rate law. The proposed methods could be expected to provide promising tools for simultaneous kinetic analysis of multiple reactions in complex systems in real-time and nondestructively. - Highlights: • A novel three-way calibration method for the quantitative kinetic analysis of NADH and FAD in human plasma is proposed. • The method can directly monitor the concentration of each analyte in the reaction in real-time and nondestructively. • The method has the second-order advantage. • A

  14. Multi-resolution voxel phantom modeling: a high-resolution eye model for computational dosimetry

    Science.gov (United States)

    Caracappa, Peter F.; Rhodes, Ashley; Fiedler, Derek

    2014-09-01

    Voxel models of the human body are commonly used for simulating radiation dose with a Monte Carlo radiation transport code. Due to memory limitations, the voxel resolution of these computational phantoms is typically too large to accurately represent the dimensions of small features such as the eye. Recently reduced recommended dose limits to the lens of the eye, which is a radiosensitive tissue with a significant concern for cataract formation, has lent increased importance to understanding the dose to this tissue. A high-resolution eye model is constructed using physiological data for the dimensions of radiosensitive tissues, and combined with an existing set of whole-body models to form a multi-resolution voxel phantom, which is used with the MCNPX code to calculate radiation dose from various exposure types. This phantom provides an accurate representation of the radiation transport through the structures of the eye. Two alternate methods of including a high-resolution eye model within an existing whole-body model are developed. The accuracy and performance of each method is compared against existing computational phantoms.

  15. Voxel inversion of airborne electromagnetic data for improved model integration

    Science.gov (United States)

    Fiandaca, Gianluca; Auken, Esben; Kirkegaard, Casper; Vest Christiansen, Anders

    2014-05-01

    Inversion of electromagnetic data has migrated from single site interpretations to inversions including entire surveys using spatial constraints to obtain geologically reasonable results. Though, the model space is usually linked to the actual observation points. For airborne electromagnetic (AEM) surveys the spatial discretization of the model space reflects the flight lines. On the contrary, geological and groundwater models most often refer to a regular voxel grid, not correlated to the geophysical model space, and the geophysical information has to be relocated for integration in (hydro)geological models. We have developed a new geophysical inversion algorithm working directly in a voxel grid disconnected from the actual measuring points, which then allows for informing directly geological/hydrogeological models. The new voxel model space defines the soil properties (like resistivity) on a set of nodes, and the distribution of the soil properties is computed everywhere by means of an interpolation function (e.g. inverse distance or kriging). Given this definition of the voxel model space, the 1D forward responses of the AEM data are computed as follows: 1) a 1D model subdivision, in terms of model thicknesses, is defined for each 1D data set, creating "virtual" layers. 2) the "virtual" 1D models at the sounding positions are finalized by interpolating the soil properties (the resistivity) in the center of the "virtual" layers. 3) the forward response is computed in 1D for each "virtual" model. We tested the new inversion scheme on an AEM survey carried out with the SkyTEM system close to Odder, in Denmark. The survey comprises 106054 dual mode AEM soundings, and covers an area of approximately 13 km X 16 km. The voxel inversion was carried out on a structured grid of 260 X 325 X 29 xyz nodes (50 m xy spacing), for a total of 2450500 inversion parameters. A classical spatially constrained inversion (SCI) was carried out on the same data set, using 106054

  16. Laser-induced forward transfer (LIFT) of congruent voxels

    Science.gov (United States)

    Piqué, Alberto; Kim, Heungsoo; Auyeung, Raymond C. Y.; Beniam, Iyoel; Breckenfeld, Eric

    2016-06-01

    Laser-induced forward transfer (LIFT) of functional materials offers unique advantages and capabilities for the rapid prototyping of electronic, optical and sensor elements. The use of LIFT for printing high viscosity metallic nano-inks and nano-pastes can be optimized for the transfer of voxels congruent with the shape of the laser pulse, forming thin film-like structures non-lithographically. These processes are capable of printing patterns with excellent lateral resolution and thickness uniformity typically found in 3-dimensional stacked assemblies, MEMS-like structures and free-standing interconnects. However, in order to achieve congruent voxel transfer with LIFT, the particle size and viscosity of the ink or paste suspensions must be adjusted to minimize variations due to wetting and drying effects. When LIFT is carried out with high-viscosity nano-suspensions, the printed voxel size and shape become controllable parameters, allowing the printing of thin-film like structures whose shape is determined by the spatial distribution of the laser pulse. The result is a new level of parallelization beyond current serial direct-write processes whereby the geometry of each printed voxel can be optimized according to the pattern design. This work shows how LIFT of congruent voxels can be applied to the fabrication of 2D and 3D microstructures by adjusting the viscosity of the nano-suspension and laser transfer parameters.

  17. The research on calibration methods of dual-CCD laser three-dimensional human face scanning system

    Science.gov (United States)

    Wang, Jinjiang; Chang, Tianyu; Ge, Baozhen; Tian, Qingguo; Yang, Fengting; Shi, Shendong

    2013-09-01

    In this paper, on the basis of considering the performance advantages of two-step method, we combines the stereo matching of binocular stereo vision with active laser scanning to calibrate the system. Above all, we select a reference camera coordinate system as the world coordinate system and unity the coordinates of two CCD cameras. And then obtain the new perspective projection matrix (PPM) of each camera after the epipolar rectification. By those, the corresponding epipolar equation of two cameras can be defined. So by utilizing the trigonometric parallax method, we can measure the space point position after distortion correction and achieve stereo matching calibration between two image points. Experiments verify that this method can improve accuracy and system stability is guaranteed. The stereo matching calibration has a simple process with low-cost, and simplifies regular maintenance work. It can acquire 3D coordinates only by planar checkerboard calibration without the need of designing specific standard target or using electronic theodolite. It is found that during the experiment two-step calibration error and lens distortion lead to the stratification of point cloud data. The proposed calibration method which combining active line laser scanning and binocular stereo vision has the both advantages of them. It has more flexible applicability. Theory analysis and experiment shows the method is reasonable.

  18. Evaluation of absorbed doses in voxel-based and simplified models for small animals.

    Science.gov (United States)

    Mohammadi, Akram; Kinase, Sakae; Saito, Kimiaki

    2012-07-01

    Internal dosimetry in non-human biota is desirable from the viewpoint of radiation protection of the environment. The International Commission on Radiological Protection (ICRP) proposed Reference Animals and Plants using simplified models, such as ellipsoids and spheres and calculated absorbed fractions (AFs) for whole bodies. In this study, photon and electron AFs in whole bodies of voxel-based rat and frog models have been calculated and compared with AFs in the reference models. It was found that the voxel-based and the reference frog (or rat) models can be consistent for the whole-body AFs within a discrepancy of 25%, as the source was uniformly distributed in the whole body. The specific absorbed fractions (SAFs) and S values were also evaluated in whole bodies and all organs of the voxel-based frog and rat models as the source was distributed in the whole body or skeleton. The results demonstrated that the whole-body SAFs reflect SAFs of all individual organs as the source was uniformly distributed per mass within the whole body by about 30% uncertainties with exceptions for body contour (up to -40%) for both electrons and photons due to enhanced radiation leakages, and for the skeleton for photons only (up to +185%) due to differences in the mass attenuation coefficients. For nuclides such as (90)Y and (90)Sr, which were concentrated in the skeleton, there were large differences between S values in the whole body and those in individual organs, however the whole-body S values for the reference models with the whole body as the source were remarkably similar to those for the voxel-based models with the skeleton as the source, within about 4 and 0.3%, respectively. It can be stated that whole-body SAFs or S values in simplified models without internal organs are not sufficient for accurate internal dosimetry because they do not reflect SAFs or S values of all individual organs as the source was not distributed uniformly in whole body. Thus, voxel-based models

  19. Simultaneous Determination of 6-Mercaptopurine and its Oxidative Metabolites in Synthetic Solutions and Human Plasma using Spectrophotometric Multivariate Calibration Methods

    Directory of Open Access Journals (Sweden)

    Mohammad-Reza Rashidi

    2011-06-01

    Full Text Available Introduction: 6-Mercaptopurine (6MP is an important chemotherapeutic drug in the conventional treatment of childhood acute lymphoblastic leukemia (ALL. It is catabolized to 6-thiouric acid (6TUA through 8-hydroxo-6-mercaptopurine (8OH6MP or 6-thioxanthine (6TX intermediates. Methods: High-performance liquid chromatography (HPLC is usually used to determine the contents of therapeutic drugs, metabolites and other important biomedical analytes in biological samples. In the present study, the multivariate calibration methods, partial least squares (PLS-1 and principle component regression (PCR have been developed and validated for the simultaneous determination of 6MP and its oxidative metabolites (6TUA, 8OH6MP and 6TX without analyte separation in spiked human plasma. Mixtures of 6MP, 8-8OH6MP, 6TX and 6TUA have been resolved by PLS-1 and PCR to their UV spectra. Results: Recoveries (% obtained for 6MP, 8-8OH6MP, 6TX and 6TUA were 94.5-97.5, 96.6-103.3, 95.1-96.9 and 93.4-95.8, respectively, using PLS-1 and 96.7-101.3, 96.2-98.8, 95.8-103.3 and 94.3-106.1, respectively, using PCR. The NAS (Net analyte signal concept was used to calculate multivariate analytical figures of merit such as limit of detection (LOD, selectivity and sensitivity. The limit of detections for 6MP, 8-8OH6MP, 6TX and 6TUA were calculated to be 0.734, 0.439, 0.797 and 0.482 µmol L-1, respectively, using PLS and 0.724, 0.418, 0783 and 0.535 µmol L-1, respectively, using PCR. HPLC was also applied as a validation method for simultaneous determination of these thiopurines in the synthetic solutions and human plasma. Conclusion: Combination of spectroscopic techniques and chemometric methods (PLS and PCR has provided a simple but powerful method for simultaneous analysis of multicomponent mixtures.

  20. Accuracy in the diagnosis of vertical root fractures, external root resorptions, and root perforations using cone-beam computed tomography with different voxel sizes of acquisition

    Science.gov (United States)

    Bragatto, Fernanda Paula; Iwaki Filho, Liogi; Kasuya, Amanda Vessoni Barbosa; Chicarelli, Mariliani; Queiroz, Alfredo Franco; Takeshita, Wilton Mitsunari; Iwaki, Lilian Cristina Vessoni

    2016-01-01

    Aim: The aim of this study is to assess the accuracy of images acquired with cone-beam computed tomography (CBCT) in the identification of three different root alterations. Materials and Methods: Forty human premolars were allocated to four experimental groups (n = 10): sound teeth (control), vertical root fracture (VRF), external root resorption (ERR), and root perforation (RP). After the root alterations had been produced, four teeth were randomly assembled into 10 macerated mandibles and submitted to CBCT. Images were acquired with five voxel sizes (0.125, 0.200, 0.250, 0.300, and 0.400 mm) and assessed by three experienced dental radiologists. Sensitivity, specificity, positive and negative predictive values, and the areas under the receiver operating characteristic curve (accuracy) were calculated. The accuracy of imaging in different voxel sizes was compared with Tukey exact binomial test (α=5%). Results: Accuracy with voxel sizes 0.125, 0.200, and 0.250 mm was significantly higher in the detection of ERRs and VRFs than voxel sizes 0.300 and 0.400 mm. No statistical difference was found in terms of accuracy among any of the studied voxel sizes in the identification of RPs. Conclusions: Voxel size 0.125 mm produced images with the best resolution without increasing radiation levels to the patient when compared to voxel sizes 0.200 and 0.250 mm. Voxel sizes 0.300 and 0.400 mm should be avoided in the identification of root alterations. PMID:27994322

  1. Rotating and translating anthropomorphic head voxel models to establish an horizontal Frankfort plane for dental CBCT Monte Carlo simulations: a dose comparison study

    Science.gov (United States)

    Stratis, A.; Zhang, G.; Jacobs, R.; Bogaerts, R.; Bosmans, H.

    2016-12-01

    In order to carry out Monte Carlo (MC) dosimetry studies, voxel phantoms, modeling human anatomy, and organ-based segmentation of CT image data sets are applied to simulation frameworks. The resulting voxel phantoms preserve patient CT acquisition geometry; in the case of head voxel models built upon head CT images, the head support with which CT scanners are equipped introduces an inclination to the head, and hence to the head voxel model. In dental cone beam CT (CBCT) imaging, patients are always positioned in such a way that the Frankfort line is horizontal, implying that there is no head inclination. The orientation of the head is important, as it influences the distance of critical radiosensitive organs like the thyroid and the esophagus from the x-ray tube. This work aims to propose a procedure to adjust head voxel phantom orientation, and to investigate the impact of head inclination on organ doses in dental CBCT MC dosimetry studies. The female adult ICRP, and three in-house-built paediatric voxel phantoms were in this study. An EGSnrc MC framework was employed to simulate two commonly used protocols; a Morita Accuitomo 170 dental CBCT scanner (FOVs: 60  ×  60 mm2 and 80  ×  80 mm2, standard resolution), and a 3D Teeth protocol (FOV: 100  ×  90 mm2) in a Planmeca Promax 3D MAX scanner. Result analysis revealed large absorbed organ dose differences in radiosensitive organs between the original and the geometrically corrected voxel models of this study, ranging from  -45.6% to 39.3%. Therefore, accurate dental CBCT MC dose calculations require geometrical adjustments to be applied to head voxel models.

  2. A Morphological Approach to the Voxelization of Solids

    DEFF Research Database (Denmark)

    Bærentzen, Jakob Andreas; Sramek, Milos; Christensen, Niels Jørgen

    2000-01-01

    In this paper we present a new, morphological criterion for determining whether a geometric solid is suitable for voxelization at a given resolution. The criterion embodies two conditions, namely that the curvature of the solid must be bounded and the critical points of the distance field must...... be at a certain distance from the boundary of the solid. For solids that fulfill this criterion, we present an analytic and an empirical bound for the trilinear reconstruction error. Additionally, we give a theoretical argument as to why the distance field approach to voxelization is more sound than...

  3. An Improved Optimization Method for the Relevance Voxel Machine

    DEFF Research Database (Denmark)

    Ganz, Melanie; Sabuncu, M. R.; Van Leemput, Koen

    2013-01-01

    In this paper, we will re-visit the Relevance Voxel Machine (RVoxM), a recently developed sparse Bayesian framework used for predicting biological markers, e.g., presence of disease, from high-dimensional image data, e.g., brain MRI volumes. The proposed improvement, called IRVoxM, mitigates...... the shortcomings of the greedy optimization scheme of the original RVoxM algorithm by exploiting the form of the marginal likelihood function. In addition, it allows voxels to be added and deleted from the model during the optimization. In our experiments we show that IRVoxM outperforms RVoxM on synthetic data...

  4. Selection of voxel size and photon number in voxel-based Monte Carlo method: criteria and applications.

    Science.gov (United States)

    Li, Dong; Chen, Bin; Ran, Wei Yu; Wang, Guo Xiang; Wu, Wen Juan

    2015-01-01

    The voxel-based Monte Carlo method (VMC) is now a gold standard in the simulation of light propagation in turbid media. For complex tissue structures, however, the computational cost will be higher when small voxels are used to improve smoothness of tissue interface and a large number of photons are used to obtain accurate results. To reduce computational cost, criteria were proposed to determine the voxel size and photon number in 3-dimensional VMC simulations with acceptable accuracy and computation time. The selection of the voxel size can be expressed as a function of tissue geometry and optical properties. The photon number should be at least 5 times the total voxel number. These criteria are further applied in developing a photon ray splitting scheme of local grid refinement technique to reduce computational cost of a nonuniform tissue structure with significantly varying optical properties. In the proposed technique, a nonuniform refined grid system is used, where fine grids are used for the tissue with high absorption and complex geometry, and coarse grids are used for the other part. In this technique, the total photon number is selected based on the voxel size of the coarse grid. Furthermore, the photon-splitting scheme is developed to satisfy the statistical accuracy requirement for the dense grid area. Result shows that local grid refinement technique photon ray splitting scheme can accelerate the computation by 7.6 times (reduce time consumption from 17.5 to 2.3 h) in the simulation of laser light energy deposition in skin tissue that contains port wine stain lesions.

  5. Quality control of geological voxel models using experts' gaze

    NARCIS (Netherlands)

    Maanen, van Peter-Paul; Busschers, Freek S.; Brouwer, Anne-Marie; Meulendijk, van der Michiel J.; Erp, van Jan B.F.

    2015-01-01

    Due to an expected increase in geological voxel model data-flow and user demands, the development of improved quality control for such models is crucial. This study explores the potential of a new type of quality control that improves the detection of errors by just using gaze behavior of 12 geologi

  6. Finding significantly connected voxels based on histograms of connection strengths

    DEFF Research Database (Denmark)

    Kasenburg, Niklas; Pedersen, Morten Vester; Darkner, Sune

    2016-01-01

    -distribution and significance is determined using the false discovery rate (FDR). Segmentations are based on significantly connected voxels and their FDR. In this work we focus on the thalamus and the target regions were chosen by dividing the cortex into a prefrontal/temporal zone, motor zone, somatosensory zone and a parieto...

  7. Vessel-guided airway segmentation based on voxel classification

    DEFF Research Database (Denmark)

    Lo, Pechin Chien Pau; Sporring, Jon; Ashraf, Haseem;

    2008-01-01

    This paper presents a method for improving airway tree segmentation using vessel orientation information. We use the fact that an airway branch is always accompanied by an artery, with both structures having similar orientations. This work is based on a  voxel classification airway segmentation...

  8. Robust Segmentation of Voxel Shapes using Medial Surfaces

    NARCIS (Netherlands)

    Reniers, Dennie; Telea, Alexandru

    2008-01-01

    We present a new patch-type segmentation method for 3D voxel shapes based on the medial surface, also called surface skeleton. The boundaries of the simplified fore- and background skeletons map one-to-one to increasingly fuzzy, soft convex, respectively concave, edges of the shape. Using this prope

  9. Voxel model in BNCT treatment planning: performance analysis and improvements

    Science.gov (United States)

    González, Sara J.; Carando, Daniel G.; Santa Cruz, Gustavo A.; Zamenhof, Robert G.

    2005-02-01

    In recent years, many efforts have been made to study the performance of treatment planning systems in deriving an accurate dosimetry of the complex radiation fields involved in boron neutron capture therapy (BNCT). The computational model of the patient's anatomy is one of the main factors involved in this subject. This work presents a detailed analysis of the performance of the 1 cm based voxel reconstruction approach. First, a new and improved material assignment algorithm implemented in NCTPlan treatment planning system for BNCT is described. Based on previous works, the performances of the 1 cm based voxel methods used in the MacNCTPlan and NCTPlan treatment planning systems are compared by standard simulation tests. In addition, the NCTPlan voxel model is benchmarked against in-phantom physical dosimetry of the RA-6 reactor of Argentina. This investigation shows the 1 cm resolution to be accurate enough for all reported tests, even in the extreme cases such as a parallelepiped phantom irradiated through one of its sharp edges. This accuracy can be degraded at very shallow depths in which, to improve the estimates, the anatomy images need to be positioned in a suitable way. Rules for this positioning are presented. The skin is considered one of the organs at risk in all BNCT treatments and, in the particular case of cutaneous melanoma of extremities, limits the delivered dose to the patient. Therefore, the performance of the voxel technique is deeply analysed in these shallow regions. A theoretical analysis is carried out to assess the distortion caused by homogenization and material percentage rounding processes. Then, a new strategy for the treatment of surface voxels is proposed and tested using two different irradiation problems. For a parallelepiped phantom perpendicularly irradiated with a 5 keV neutron source, the large thermal neutron fluence deviation present at shallow depths (from 54% at 0 mm depth to 5% at 4 mm depth) is reduced to 2% on average

  10. Comparison between calibration methods for in vivo monitoring in human body; Comparacao entre metodos de calibracao para monitoracao in vivo no corpo humano

    Energy Technology Data Exchange (ETDEWEB)

    Mello, J.Q. de; Almeida, A.PF.; Dantas, A.L.A.; Hunt, J.G.; Dantas, B.M., E-mail: bmdantas@ird.gov.br [Instituto de Radioprotecao e Dosimetria, (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2014-07-01

    The determination of photon emitters in the human body through in vivo measurements requires the use of specific techniques to obtain calibration factors which correlate count rates and activities present in the body. In the present work two methods were compared for the measurement of {sup 40}K in whole body geometry with a scintillation detector type NaI(Tl)3x3: (1) experimental, using a BOMAB physical anthropomorphic phantom and (2) mathematical simulation of the phantom and the interaction of the photons with the detector. The results obtained show the equivalence between the methods in the geometry and energy conditions adopted in the experiment. (author)

  11. Comparing the Effect of Different Voxel Resolutions for Assessment of Vertical Root Fracture of Permanent Teeth

    Directory of Open Access Journals (Sweden)

    Uzun

    2015-07-01

    Full Text Available Background The teeth with undiagnosed vertical root fractures (VRFs are likely to receive endodontic treatment or retreatment, leading to frustration and inappropriate endodontic therapies. Moreover, many cases of VRFs cannot be diagnosed definitively until the extraction of tooth. Objectives This study aimed to assess the use of different voxel resolutions of two different cone beam computerized tomography (CBCT units in the detection VRFs in vitro. Materials and Methods The study material comprised 74 extracted human mandibular single rooted premolar teeth without root fractures that had not undergone any root-canal treatment. Images were obtained by two different CBCT units. Four image sets were obtained as follows: 1 3D Accuitomo 170, 4 × 4 cm field of view (FOV (0.080 mm3; 2 3D Accuitomo 170. 6 × 6 cm FOV (0.125 mm3; 3 NewTom 3G, 6˝ (0.16 mm3 and 4 NewTom 3G, 9˝ FOV (0.25 mm3. Kappa coefficients were calculated to assess both intra- and inter-observer agreements for each image set. Results No significant differences were found among observers or voxel sizes, with high average Z (Az results being reported for all groups. Both intra- and inter-observer agreement values were relatively better for 3D Accuitomo 170 images than the images from NewTom 3G. The highest Az and kappa values were obtained with 3D Accuitomo 170, 4 × 4 cm FOV (0.080 mm3 images. Conclusion No significant differences were found among observers or voxel sizes, with high Az results reported for all groups.

  12. Quantitative fluorescence kinetic analysis of NADH and FAD in human plasma using three- and four-way calibration methods capable of providing the second-order advantage.

    Science.gov (United States)

    Kang, Chao; Wu, Hai-Long; Zhou, Chang; Xiang, Shou-Xia; Zhang, Xiao-Hua; Yu, Yong-Jie; Yu, Ru-Qin

    2016-03-03

    The metabolic coenzymes reduced nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) are the primary electron donor and acceptor respectively, participate in almost all biological metabolic pathways. This study develops a novel method for the quantitative kinetic analysis of the degradation reaction of NADH and the formation reaction of FAD in human plasma containing an uncalibrated interferent, by using three-way calibration based on multi-way fluorescence technique. In the three-way analysis, by using the calibration set in a static manner, we directly predicted the concentrations of both analytes in the mixture at any time after the start of their reactions, even in the presence of an uncalibrated spectral interferent and a varying background interferent. The satisfactory quantitative results indicate that the proposed method allows one to directly monitor the concentration of each analyte in the mixture as the function of time in real-time and nondestructively, instead of determining the concentration after the analytical separation. Thereafter, we fitted the first-order rate law to their concentration data throughout their reactions. Additionally, a four-way calibration procedure is developed as an alternative for highly collinear systems. The results of the four-way analysis confirmed the results of the three-way analysis and revealed that both the degradation reaction of NADH and the formation reaction of FAD in human plasma fit the first-order rate law. The proposed methods could be expected to provide promising tools for simultaneous kinetic analysis of multiple reactions in complex systems in real-time and nondestructively.

  13. An exact general remeshing scheme applied to conservative voxelization

    CERN Document Server

    Powell, Devon

    2014-01-01

    We derive new formulae to calculate volumes, moments, and polynomial integrals up to quadratic order over polytopes in two and three dimensions. In principle, our method can be used to derive analogous formulae for polynomials of any order in any dimensionality. By successively applying the divergence theorem, we reduce the dimensionality of the integrals from volumes to areas to lines to points. We arrive at closed-form expressions involving data local to the vertices that define the polytope, with no need for the entire polytope to be explicitly represented all at once. In addition, there are no latent assumptions regarding the convexity or connectedness of the domain. The form of these expressions is particularly well-suited to software implementations. We apply these formulae to the case of voxelizing polytopes using an exact volume-sampling approach, including the voxelization of polytopes with linearly and quadratically varying densities. We take particular care to avoid loss of numerical precision, ach...

  14. Connecting horizon pixels and interior voxels of a black hole

    CERN Document Server

    Nicolini, Piero

    2014-01-01

    In this paper we discuss to what extent one can infer details of the interior structure of a black hole based on its horizon. Recalling that black hole thermal properties are connected to the non-classical nature of gravity, we circumvent the restrictions of the no hair theorem by postulating that the black hole interior is singularity free due to violations of the usual energy conditions. Further these conditions allow one to establish a one-to-one, holographic projection between Planckian areal "bits" on the horizon and "voxels", representing the gravitational degrees of freedom in the black hole interior. We illustrate the repercussions of this idea by discussing an example of the black hole interior consisting of a de Sitter core postulated to arise from the local graviton quantum vacuum energy. It is shown that the black hole entropy can emerge as the statistical entropy of a gas of voxels.

  15. Fluorescent quantification of terazosin hydrochloride content in human plasma and tablets using second-order calibration based on both parallel factor analysis and alternating penalty trilinear decomposition.

    Science.gov (United States)

    Zou, Hong-Yan; Wu, Hai-Long; OuYang, Li-Qun; Zhang, Yan; Nie, Jin-Fang; Fu, Hai-Yan; Yu, Ru-Qin

    2009-09-14

    Two second-order calibration methods based on the parallel factor analysis (PARAFAC) and the alternating penalty trilinear decomposition (APTLD) method, have been utilized for the direct determination of terazosin hydrochloride (THD) in human plasma samples, coupled with the excitation-emission matrix fluorescence spectroscopy. Meanwhile, the two algorithms combing with the standard addition procedures have been applied for the determination of terazosin hydrochloride in tablets and the results were validated by the high-performance liquid chromatography with fluorescence detection. These second-order calibrations all adequately exploited the second-order advantages. For human plasma samples, the average recoveries by the PARAFAC and APTLD algorithms with the factor number of 2 (N=2) were 100.4+/-2.7% and 99.2+/-2.4%, respectively. The accuracy of two algorithms was also evaluated through elliptical joint confidence region (EJCR) tests and t-test. It was found that both algorithms could give accurate results, and only the performance of APTLD was slightly better than that of PARAFAC. Figures of merit, such as sensitivity (SEN), selectivity (SEL) and limit of detection (LOD) were also calculated to compare the performances of the two strategies. For tablets, the average concentrations of THD in tablet were 63.5 and 63.2 ng mL(-1) by using the PARAFAC and APTLD algorithms, respectively. The accuracy was evaluated by t-test and both algorithms could give accurate results, too.

  16. Efficient graphics processing unit-based voxel carving for surveillance

    Science.gov (United States)

    Ober-Gecks, Antje; Zwicker, Marius; Henrich, Dominik

    2016-07-01

    A graphics processing unit (GPU)-based implementation of a space carving method for the reconstruction of the photo hull is presented. In particular, the generalized voxel coloring with item buffer approach is transferred to the GPU. The fast computation on the GPU is realized by an incrementally calculated standard deviation within the likelihood ratio test, which is applied as color consistency criterion. A fast and efficient computation of complete voxel-pixel projections is provided using volume rendering methods. This generates a speedup of the iterative carving procedure while considering all given pixel color information. Different volume rendering methods, such as texture mapping and raycasting, are examined. The termination of the voxel carving procedure is controlled through an anytime concept. The photo hull algorithm is examined for its applicability to real-world surveillance scenarios as an online reconstruction method. For this reason, a GPU-based redesign of a visual hull algorithm is provided that utilizes geometric knowledge about known static occluders of the scene in order to create a conservative and complete visual hull that includes all given objects. This visual hull approximation serves as input for the photo hull algorithm.

  17. Voxel significance mapping in epilepsy studies using subtraction ictal SPECT

    Science.gov (United States)

    Brinkmann, Benjamin H.; O'Brien, Terence J.; Webster, Desmond B.; Robins, Peter D.; Mullan, Brian P.; Robb, Richard A.

    1999-05-01

    Subtraction ictal SPECT coregistered to MRI (SISCOM) has been shown to aid epileptogenic localization and improve surgical outcomes in partial epilepsy patients. This paper reports a new method of identifying significant areas of epileptogenic activation in the SISCOM subtraction image taking into account normal variation between sequential Tc-99m Ethyl Cysteinate Diethylester SPECT scans of single individuals. The method uses the AIR 3.0 nonlinear registration software to combine a group of subtraction images into a common anatomical framework. A map of the pixel intensity standard deviation values in the subtraction images is created, and this map is nonlinearly registered to a patient's SISCOM subtraction image. Pixels in the patient subtraction image may then be evaluated based upon the statistical characteristics of corresponding pixels in the atlas. Validation experiments were performed to verify that local image variances are not constant across the image and that nonlinear registration preserves local image variances. SISCOM images created with the voxel variance method were rated higher in quality than the conventional image variance method in images from fifteen patients. No difference in localization rate was observed between the voxel variance mapping and image variance methods. The voxel significance mapping method was shown to improve the quality of clinical SISCOM images without removing localizing information.

  18. Monte Carlo study of voxel S factor dependence on tissue density and atomic composition

    Energy Technology Data Exchange (ETDEWEB)

    Amato, Ernesto, E-mail: eamato@unime.it [University of Messina, Department of Biomedical Sciences and of Morphologic and Functional Imaging, Section of Radiological Sciences, via Consolare Valeria, 1, I-98125 Messina (Italy); Italiano, Antonio [INFN – Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Messina (Italy); Baldari, Sergio [University of Messina, Department of Biomedical Sciences and of Morphologic and Functional Imaging, Section of Radiological Sciences, via Consolare Valeria, 1, I-98125 Messina (Italy)

    2013-11-21

    Voxel dosimetry is a common approach to the internal dosimetry of non-uniform activity distributions in nuclear medicine therapies with radiopharmaceuticals and in the estimation of the radiation hazard due to internal contamination of radionuclides. Aim of the present work is to extend our analytical approach for the calculation of voxel S factors to materials different from the soft tissue. We used a Monte Carlo simulation in GEANT4 of a voxelized region of each material in which the source of monoenergetic electrons or photons was uniformly distributed within the central voxel, and the energy deposition was scored over the surrounding 11×11×11 voxels. Voxel S factors were obtained for the following standard ICRP materials: Adipose tissue, Bone cortical, Brain, Lung, Muscle skeletal and Tissue soft with 1 g cm{sup −3} density. Moreover, we considered the standard ICRU materials: Bone compact and Muscle striated. Voxel S factors were represented as a function of the “normalized radius”, defined as the ratio between the source–target voxel distance and the voxel side. We found that voxel S factors and related analytical fit functions are mainly affected by the tissue density, while the material composition gives only a slight contribution to the difference between data series, which is negligible for practical purposes. Our results can help in broadening the dosimetric three-dimensional approach based on voxel S factors to other tissues where diagnostic and therapeutic radionuclides can be taken up and radiation can propagate.

  19. Voxel-by-voxel correlations of perfusion, substrate, and metabolite signals in dynamic hyperpolarized (13) C imaging.

    Science.gov (United States)

    Lau, Justin Y C; Chen, Albert P; Gu, Yi-Ping; Cunningham, Charles H

    2016-08-01

    In this study, a mixture of pyruvic acid and the perfusion agent HP001 was co-polarized for simultaneous assessment of perfusion and metabolism in vivo. The pre-polarized mixture was administered to rats with subcutaneous MDA-MB-231 breast cancer xenografts and imaged using an interleaved sequence with designed spectral-spatial pulses and flyback echo-planar readouts. Voxel-by-voxel signal correlations from 10 animals (15 data sets) were analyzed for tumour, kidney, and muscle regions of interest. The relationship between perfusion and hyperpolarized signal was explored on a voxel-by-voxel basis in various metabolically active tissues, including tumour, healthy kidneys, and skeletal muscle. Positive pairwise correlations between lactate, pyruvate, and HP001 observed in all 10 tumours suggested that substrate delivery was the dominant factor limiting the conversion of pyruvate to lactate in the tumour model used in this study. On the other hand, in cases where conversion is the limiting factor, such as in healthy kidneys, both pyruvate and lactate can act as excellent perfusion markers. In intermediate cases between the two limits, such as in skeletal muscle, some perfusion information may be inferred from the (pyruvate + lactate) signal distribution. Co-administration of pyruvate with a dynamic nuclear polarization (DNP) perfusion agent is an effective approach for distinguishing between slow metabolism and poor perfusion and a practical strategy for lactate signal normalization to account for substrate delivery, especially in cases of rapid pyruvate-to-lactate conversion and in poorly perfused regions with inadequate pyruvate signal-to-noise ratio for reliable determination of the lactate-to-pyruvate ratio. Copyright © 2016 John Wiley & Sons, Ltd.

  20. High cone-angle x-ray computed micro-tomography with 186 GigaVoxel datasets

    Science.gov (United States)

    Myers, Glenn R.; Latham, Shane J.; Kingston, Andrew M.; Kolomazník, Jan; Krajíček, Václav; Krupka, TomáÅ.¡; Varslot, Trond K.; Sheppard, Adrian P.

    2016-10-01

    X-ray computed micro-tomography systems are able to collect data with sub-micron resolution. This high- resolution imaging has many applications but is particularly important in the study of porous materials, where the sub-micron structure can dictate large-scale physical properties (e.g. carbonates, shales, or human bone). Sample preparation and mounting become diffiult for these materials below 2mm diameter: consequently, a typical ultra-micro-CT reconstruction volume (with sub-micron resolution) will be around 3k x 3k x 10k voxels, with some reconstructions becoming much larger. In this paper, we discuss the hardware (MPI-parallel CPU/GPU) and software (python/C++/CUDA) tools used at the ANU CTlab to reconstruct 186 GigaVoxel datasets.

  1. A new anthropometric phantom of the human leg for calibrating in vivo measurements of stable lead in bone using x-ray fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    Spitz, Henry; Jenkins, Mark; Lodwick, Jeffrey [Cincinnati Univ., OH (United States). Dept. of Mechanical, Industrial and Nuclear Engineering

    1997-12-31

    Full text. A new anthropometric phantom of the human leg has been developed for calibrating in vivo measurements of stable lead in the bone using x-ray fluorescence. The phantom reproduces the shape and radiological characteristics of the midshaft of the human leg and includes tissue substitutes for cortical bone, bone marrow, and muscle which have been formulated using polyurethanes and calcium carbonate to provide the desired characteristics of density x-ray attenuation, and calcium content. The phantom includes a set of simulated tibia bones, each containing a precisely known concentration of stable lead, that can be easily inserted into the leg. Formerly, of a set of plexiglas cylinders filled with plaster of-paris, each containing a known lead content, was the consensus standard calibration phantom. Tissue substitute materials used in the new anthropometric calibration phantom are much more uniform in density and composition than the plaster-of-paris phantoms and its realistic appearance provides a practical means of evaluating the variability in measurements results due to the changes in subject-detector positioning. Use of the new anthropometric calibration phantom results in a energy spectrum that closely resembles the spectrum observed when measuring a human subject. The energy spectrum produced by the plaster-of-paris phantom lacks the substantial Compton Scattering component produced by the leg muscle mass which leads to unrealistic estimates of in vivo measurement sensitivity. The minimum detection limit (MDL) for in vivo measurement of stable lead in bone, using an efficiency derived from the new anthropometric phantom, ranges from 18,6 parts per million (ppm) to 26,3 ppm using the K{sub {beta}1,3}/Elastic ratio or the K{sup 1}/Elastic ratio, respectively. These values are significantly greater than the MDL cited in the literature obtained using a efficiency derived the conventional cylindrical plaster-of-paris phantom. Likewise, the realistic shape of

  2. Surface mesh to voxel data registration for patient-specific anatomical modeling

    Science.gov (United States)

    de Oliveira, Júlia E. E.; Giessler, Paul; Keszei, András.; Herrler, Andreas; Deserno, Thomas M.

    2016-03-01

    Virtual Physiological Human (VPH) models are frequently used for training, planning, and performing medical procedures. The Regional Anaesthesia Simulator and Assistant (RASimAs) project has the goal of increasing the application and effectiveness of regional anesthesia (RA) by combining a simulator of ultrasound-guided and electrical nerve-stimulated RA procedures and a subject-specific assistance system through an integration of image processing, physiological models, subject-specific data, and virtual reality. Individualized models enrich the virtual training tools for learning and improving regional anaesthesia (RA) skills. Therefore, we suggest patient-specific VPH models that are composed by registering the general mesh-based models with patient voxel data-based recordings. Specifically, the pelvis region has been focused for the support of the femoral nerve block. The processing pipeline is composed of different freely available toolboxes such as MatLab, the open Simulation framework (SOFA), and MeshLab. The approach of Gilles is applied for mesh-to-voxel registration. Personalized VPH models include anatomical as well as mechanical properties of the tissues. Two commercial VPH models (Zygote and Anatomium) were used together with 34 MRI data sets. Results are presented for the skin surface and pelvic bones. Future work will extend the registration procedure to cope with all model tissue (i.e., skin, muscle, bone, vessel, nerve, fascia) in a one-step procedure and extrapolating the personalized models to body regions actually being out of the captured field of view.

  3. Comparing voxel-based iterative sensitivity and voxel-based morphometry to detect abnormalities in T2-weighted MRI.

    Science.gov (United States)

    Diaz-de-Grenu, Lara Z; Acosta-Cabronero, Julio; Williams, Guy B; Nestor, Peter J

    2014-10-15

    This study aimed to test the superiority proposed by Abbott et al. (2011) of their Voxel based iterative sensitivity (VBIS) method over Voxel Based Morphometry using T2-weighted images (T2-VBM), in detecting intensity changes in Alzheimer's disease (AD). A comparison was made first in simulated intensity lesions and then in AD patients. Intensity changes were evaluated in the whole-brain with VBIS and with a simple intensity-based approach and in specific tissue classes with the conventional VBM method of using tissue probability segments. Results showed that VBIS performed well in the simulated environment though it showed no superiority in detecting the lesion compared to the much simpler VBM approach. The VBIS method, however, failed to detect any meaningful signal intensity reduction in AD patient data. Moreover, its whole brain approach was contaminated by the excess cerebrospinal fluid signal (very bright on T2-weighted scans) in areas of maximal measurable atrophy (mesial temporal lobes); this gave rise to spurious signal intensity increases in these regions in AD. The same artefact was observed for both intensity-based methods but not with the conventional VBM approach of performing statistics on grey matter segments. In conclusion, no evidence was found to indicate that VBIS offers benefits over T2-VBM in AD, nor in simulation intensity lesions. The study highlights the necessity of empirically testing voxel-based analysis techniques rather than merely claiming superiority of one method over another on theoretical grounds.

  4. Cross-Wire Calibration for Freehand 3D Ultrasonography: Measurement and Numerical Issues

    Directory of Open Access Journals (Sweden)

    J. Jan

    2005-06-01

    Full Text Available 3D freehand ultrasound is an imaging technique, which is graduallyfinding clinical applications. A position sensor is attached to aconventional ultrasound probe, so that B-scans are acquired along withtheir relative locations. This allows the B-scans to be inserted into a3D regular voxel array, which can then be visualized usingarbitrary-plane slicing, and volume or surface rendering. A keyrequirement for correct reconstruction is the calibration: determiningthe position and orientation of the B-scans with respect to theposition sensor's receiver. Following calibration, interpolation in theset of irregularly spaced B-scans is required to reconstruct aregular-voxel array. This text describes a freehand measurement of 2Dultrasonic data, an approach to the calibration problem and severalnumerical issues concerned with the calibration and reconstruction.

  5. Voxelization Algorithms for Geospatial Applications: Computational methods for voxelating spatial datasets of 3D city models containing 3D surface, curve and point data models

    NARCIS (Netherlands)

    Nourian Ghadikolaee, P.; Goncalves, R.; Zlatanova, S.; Arroyo Ohori, G.A.K.; Vu Vo, A.

    2016-01-01

    Voxel representations have been used for years in scientific computation and medical imaging. The main focus of our research is to provide easy access to methods for making large-scale voxel models of built environment for environmental modelling studies while ensuring they are spatially correct, me

  6. Micellar Enhanced Three-Dimensional Excitation-Emission Matrix Fluorescence for Rapid Determination of Antihypertensives in Human Plasma with Aid of Second-Order Calibration Methods

    Directory of Open Access Journals (Sweden)

    Hai-Yan Fu

    2015-01-01

    Full Text Available A highly sensitive three-dimensional excitation-emission fluorescence method was proposed to determine antihypertensives including valsartan and amlodipine besylate in human plasma with the aid of second-order calibration methods based on parallel factor analysis (PARAFAC and alternating trilinear decomposition (ATLD algorithms. Antihypertensives with weak fluorescent can be transformed into a strong fluorescent property by changing microenvironment in samples using micellar enhanced surfactant. Both the adopted algorithms with second-order advantage can improve the resolution and directly attain antihypertensives concentration even in the presence of potential strong intrinsic fluorescence from human plasma. The satisfactory results can be achieved for valsartan and amlodipine besylate in complicated human plasma. Furthermore, some statistical parameters and figures of merit were evaluated to investigate the performance of the proposed method, and the accuracy and precision of the proposed method were also validated by the elliptical joint confidence region (EJCR test and repeatability analysis of intraday and interday assay. The proposed method could not only light a new avenue to directly determine valsartan or amlodipine besylate in human plasma, but also hold great potential to be extended as a promising alternative for more practical applications in the determination of weak fluorescent drugs.

  7. A voxel-based approach to gray matter asymmetries.

    Science.gov (United States)

    Luders, E; Gaser, C; Jancke, L; Schlaug, G

    2004-06-01

    Voxel-based morphometry (VBM) was used to analyze gray matter (GM) asymmetries in a large sample (n = 60) of male and female professional musicians with and without absolute pitch (AP). We chose to examine these particular groups because previous studies using traditional region-of-interest (ROI) analyses have shown differences in hemispheric asymmetry related to AP and gender. Voxel-based methods may have advantages over traditional ROI-based methods since the analysis can be performed across the whole brain with minimal user bias. After determining that the VBM method was sufficiently sensitive for the detection of differences in GM asymmetries between groups, we found that male AP musicians were more leftward lateralized in the anterior region of the planum temporale (PT) than male non-AP musicians. This confirmed the results of previous studies using ROI-based methods that showed an association between PT asymmetry and the AP phenotype. We further observed that male non-AP musicians revealed an increased leftward GM asymmetry in the postcentral gyrus compared to female non-AP musicians, again corroborating results of a previously published study using ROI-based methods. By analyzing hemispheric GM differences across our entire sample, we were able to partially confirm findings of previous studies using traditional morphometric techniques, as well as more recent, voxel-based analyses. In addition, we found some unusually pronounced GM asymmetries in our musician sample not previously detected in subjects unselected for musical training. Since we were able to validate gender- and AP-related brain asymmetries previously described using traditional ROI-based morphometric techniques, the results of our analyses support the use of VBM for examinations of GM asymmetries.

  8. Human (Clovis)-gomphothere (Cuvieronius sp.) association ∼ 13,390 calibrated yBP in Sonora, Mexico.

    Science.gov (United States)

    Sanchez, Guadalupe; Holliday, Vance T; Gaines, Edmund P; Arroyo-Cabrales, Joaquín; Martínez-Tagüeña, Natalia; Kowler, Andrew; Lange, Todd; Hodgins, Gregory W L; Mentzer, Susan M; Sanchez-Morales, Ismael

    2014-07-29

    The earliest known foragers to populate most of North America south of the glaciers [∼ 11,500 to ≥ ∼ 10,800 (14)C yBP; ∼ 13,300 to ∼ 12,800 calibrated (Cal) years] made distinctive "Clovis" artifacts. They are stereotypically characterized as hunters of Pleistocene megamammals (mostly mammoth) who entered the continent via Beringia and an ice-free corridor in Canada. The origins of Clovis technology are unclear, however, with no obvious evidence of a predecessor to the north. Here we present evidence for Clovis hunting and habitation ∼ 11,550 yBP (∼ 13,390 Cal years) at "El Fin del Mundo," an archaeological site in Sonora, northwestern Mexico. The site also includes the first evidence to our knowledge for gomphothere (Cuvieronius sp.) as Clovis prey, otherwise unknown in the North American archaeological record and terminal Pleistocene paleontological record. These data (i) broaden the age and geographic range for Clovis, establishing El Fin del Mundo as one of the oldest and southernmost in situ Clovis sites, supporting the hypothesis that Clovis had its origins well south of the gateways into the continent, and (ii) expand the make-up of the North American megafauna community just before extinction.

  9. Human (Clovis)-gomphothere (Cuvieronius sp.) association ∼13,390 calibrated yBP in Sonora, Mexico

    Science.gov (United States)

    Sanchez, Guadalupe; Holliday, Vance T.; Gaines, Edmund P.; Arroyo-Cabrales, Joaquín; Martínez-Tagüeña, Natalia; Kowler, Andrew; Lange, Todd; Hodgins, Gregory W. L.; Mentzer, Susan M.; Sanchez-Morales, Ismael

    2014-07-01

    The earliest known foragers to populate most of North America south of the glaciers [∼11,500 to ≥ ∼10,800 14C yBP; ∼13,300 to ∼12,800 calibrated (Cal) years] made distinctive "Clovis" artifacts. They are stereotypically characterized as hunters of Pleistocene megamammals (mostly mammoth) who entered the continent via Beringia and an ice-free corridor in Canada. The origins of Clovis technology are unclear, however, with no obvious evidence of a predecessor to the north. Here we present evidence for Clovis hunting and habitation ∼11,550 yBP (∼13,390 Cal years) at "El Fin del Mundo," an archaeological site in Sonora, northwestern Mexico. The site also includes the first evidence to our knowledge for gomphothere (Cuvieronius sp.) as Clovis prey, otherwise unknown in the North American archaeological record and terminal Pleistocene paleontological record. These data (i) broaden the age and geographic range for Clovis, establishing El Fin del Mundo as one of the oldest and southernmost in situ Clovis sites, supporting the hypothesis that Clovis had its origins well south of the gateways into the continent, and (ii) expand the make-up of the North American megafauna community just before extinction.

  10. Human (Clovis)–gomphothere (Cuvieronius sp.) association ∼13,390 calibrated yBP in Sonora, Mexico

    Science.gov (United States)

    Sanchez, Guadalupe; Holliday, Vance T.; Gaines, Edmund P.; Arroyo-Cabrales, Joaquín; Martínez-Tagüeña, Natalia; Kowler, Andrew; Lange, Todd; Hodgins, Gregory W. L.; Mentzer, Susan M.; Sanchez-Morales, Ismael

    2014-01-01

    The earliest known foragers to populate most of North America south of the glaciers [∼11,500 to ≥ ∼10,800 14C yBP; ∼13,300 to ∼12,800 calibrated (Cal) years] made distinctive “Clovis” artifacts. They are stereotypically characterized as hunters of Pleistocene megamammals (mostly mammoth) who entered the continent via Beringia and an ice-free corridor in Canada. The origins of Clovis technology are unclear, however, with no obvious evidence of a predecessor to the north. Here we present evidence for Clovis hunting and habitation ∼11,550 yBP (∼13,390 Cal years) at “El Fin del Mundo,” an archaeological site in Sonora, northwestern Mexico. The site also includes the first evidence to our knowledge for gomphothere (Cuvieronius sp.) as Clovis prey, otherwise unknown in the North American archaeological record and terminal Pleistocene paleontological record. These data (i) broaden the age and geographic range for Clovis, establishing El Fin del Mundo as one of the oldest and southernmost in situ Clovis sites, supporting the hypothesis that Clovis had its origins well south of the gateways into the continent, and (ii) expand the make-up of the North American megafauna community just before extinction. PMID:25024193

  11. Vessel-guided airway tree segmentation: A voxel classification approach

    DEFF Research Database (Denmark)

    Ashraf, Haseem; Pedersen, Jesper J H; Lo, Pechin Chien Pau;

    2010-01-01

    This paper presents a method for airway tree segmentation that uses a combination of a trained airway appearance model, vessel and airway orientation information, and region growing. We propose a voxel classification approach for the appearance model, which uses a classifier that is trained...... method is evaluated on 250 low dose computed tomography images from a lung cancer screening trial. Our experiments showed that applying the region growing algorithm on the airway appearance model produces more complete airway segmentations, leading to on average 20% longer trees, and 50% less leakage...

  12. Voxelization algorithms for geospatial applications: Computational methods for voxelating spatial datasets of 3D city models containing 3D surface, curve and point data models.

    Science.gov (United States)

    Nourian, Pirouz; Gonçalves, Romulo; Zlatanova, Sisi; Ohori, Ken Arroyo; Vu Vo, Anh

    2016-01-01

    Voxel representations have been used for years in scientific computation and medical imaging. The main focus of our research is to provide easy access to methods for making large-scale voxel models of built environment for environmental modelling studies while ensuring they are spatially correct, meaning they correctly represent topological and semantic relations among objects. In this article, we present algorithms that generate voxels (volumetric pixels) out of point cloud, curve, or surface objects. The algorithms for voxelization of surfaces and curves are a customization of the topological voxelization approach [1]; we additionally provide an extension of this method for voxelization of point clouds. The developed software has the following advantages:•It provides easy management of connectivity levels in the resulting voxels.•It is not dependant on any external library except for primitive types and constructs; therefore, it is easy to integrate them in any application.•One of the algorithms is implemented in C++ and C for platform independence and efficiency.

  13. Fast voxel and polygon ray-tracing algorithms in intensity modulated radiation therapy treatment planning.

    Science.gov (United States)

    Fox, Christopher; Romeijn, H Edwin; Dempsey, James F

    2006-05-01

    We present work on combining three algorithms to improve ray-tracing efficiency in radiation therapy dose computation. The three algorithms include: An improved point-in-polygon algorithm, incremental voxel ray tracing algorithm, and stereographic projection of beamlets for voxel truncation. The point-in-polygon and incremental voxel ray-tracing algorithms have been used in computer graphics and nuclear medicine applications while the stereographic projection algorithm was developed by our group. These algorithms demonstrate significant improvements over the current standard algorithms in peer reviewed literature, i.e., the polygon and voxel ray-tracing algorithms of Siddon for voxel classification (point-in-polygon testing) and dose computation, respectively, and radius testing for voxel truncation. The presented polygon ray-tracing technique was tested on 10 intensity modulated radiation therapy (IMRT) treatment planning cases that required the classification of between 0.58 and 2.0 million voxels on a 2.5 mm isotropic dose grid into 1-4 targets and 5-14 structures represented as extruded polygons (a.k.a. Siddon prisms). Incremental voxel ray tracing and voxel truncation employing virtual stereographic projection was tested on the same IMRT treatment planning cases where voxel dose was required for 230-2400 beamlets using a finite-size pencil-beam algorithm. Between a 100 and 360 fold cpu time improvement over Siddon's method was observed for the polygon ray-tracing algorithm to perform classification of voxels for target and structure membership. Between a 2.6 and 3.1 fold reduction in cpu time over current algorithms was found for the implementation of incremental ray tracing. Additionally, voxel truncation via stereographic projection was observed to be 11-25 times faster than the radial-testing beamlet extent approach and was further improved 1.7-2.0 fold through point-classification using the method of translation over the cross product technique.

  14. Single Voxel Proton Spectroscopy for Neurofeedback at 7 Tesla

    Directory of Open Access Journals (Sweden)

    Mark A. Elliott

    2011-09-01

    Full Text Available Echo-planar imaging (EPI in fMRI is regularly used to reveal BOLD activation in presubscribed regions of interest (ROI. The response is mediated by relative changes in T2* which appear as changes in the image pixel intensities. We have proposed an application of functional single-voxel proton spectroscopy (fSVPS for real-time studies at ultra-high MR field which can be comparable to the EPI BOLD fMRI technique. A spin-echo SVPS protocol without water suppression was acquired with 310 repetitions on a 7T Siemens MR scanner (TE/TR = 20/1000 ms, flip angle α = 90°, voxel size 10 × 10 × 10 mm3. Transmitter reference voltage was optimized for the voxel location. Spectral processing of the water signal free induction decay (FID using log-linear regression was used to estimate the T2* change between rest and activation of a functional task. The FID spectrum was filtered with a Gaussian window around the water peak, and log-linear regression was optimized for the particular ROI by adoption of the linearization length. The spectroscopic voxel was positioned on an ROI defined from a real-time fMRI EPI BOLD localizer. Additional online signal processing algorithms performed signal drift removal (exponential moving average, despiking and low-pass filtering (modified Kalman filter and, finally, the dynamic feedback signal normalization. Two functional tasks were used to estimate the sensitivity of the SVPS method compared to BOLD signal changes, namely the primary motor cortex (PMC, left hand finger tapping and visual cortex (VC, blinking checkerboard. Four healthy volunteers performed these tasks and an additional session using real-time signal feedback modulating their activation level of the PMC. Results show that single voxel spectroscopy is able to provide a good and reliable estimation of the BOLD signal changes. Small data size and FID signal processing instead of processing entire brain volumes as well as more information revealed from the

  15. Single Voxel Proton Spectroscopy for Neurofeedback at 7 Tesla.

    Science.gov (United States)

    Koush, Yury; Elliott, Mark A; Mathiak, Klaus

    2011-09-01

    Echo-planar imaging (EPI) in fMRI is regularly used to reveal BOLD activation in presubscribed regions of interest (ROI). The response is mediated by relative changes in T2* which appear as changes in the image pixel intensities. We have proposed an application of functional single-voxel proton spectroscopy (fSVPS) for real-time studies at ultra-high MR field which can be comparable to the EPI BOLD fMRI technique. A spin-echo SVPS protocol without water suppression was acquired with 310 repetitions on a 7T Siemens MR scanner (TE/TR = 20/1000 ms, flip angle α = 90°, voxel size 10 × 10 × 10 mm(3)). Transmitter reference voltage was optimized for the voxel location. Spectral processing of the water signal free induction decay (FID) using log-linear regression was used to estimate the T2* change between rest and activation of a functional task. The FID spectrum was filtered with a Gaussian window around the water peak, and log-linear regression was optimized for the particular ROI by adoption of the linearization length. The spectroscopic voxel was positioned on an ROI defined from a real-time fMRI EPI BOLD localizer. Additional online signal processing algorithms performed signal drift removal (exponential moving average), despiking and low-pass filtering (modified Kalman filter) and, finally, the dynamic feedback signal normalization. Two functional tasks were used to estimate the sensitivity of the SVPS method compared to BOLD signal changes, namely the primary motor cortex (PMC, left hand finger tapping) and visual cortex (VC, blinking checkerboard). Four healthy volunteers performed these tasks and an additional session using real-time signal feedback modulating their activation level of the PMC. Results show that single voxel spectroscopy is able to provide a good and reliable estimation of the BOLD signal changes. Small data size and FID signal processing instead of processing entire brain volumes as well as more information revealed from the acquired total

  16. WE-D-BRE-06: Quantification of Dose-Response for High Grade Esophagtis Patients Using a Novel Voxel-To-Voxel Method

    Energy Technology Data Exchange (ETDEWEB)

    Niedzielski, J; Martel, M; Tucker, S; Gomez, D; Court, L [MD Anderson Cancer Center, Houston, TX (United States); Univ. of Texas-Graduate School of Biomedical Sciences, Houston, TX (United States); Yang, J; Briere, T [MD Anderson Cancer Center, Houston, TX (United States)

    2014-06-15

    Purpose: Radiation induces an inflammatory response in the esophagus, discernible on CT studies. This work objectively quantifies the voxel esophageal radiation-response for patients with acute esophagitis. This knowledge is an important first-step towards predicting the effect of complex dose distributions on patient esophagitis symptoms. Methods: A previously validated voxel-based methodology of quantifying radiation esophagitis severity was used to identify the voxel dose-response for 18 NSCLC patients with severe esophagitis (CTCAE grading criteria, grade2 or higher). The response is quantified as percent voxel volume change for a given dose. During treatment (6–8 weeks), patients had weekly 4DCT studies and esophagitis scoring. Planning CT esophageal contours were deformed to each weekly CT using a demons DIR algorithm. An algorithm using the Jacobian Map from the DIR of the planning CT to all weekly CTs was used to quantify voxel-volume change, along with corresponding delivered voxel dose, to the planning voxel. Dose for each voxel for each time-point was calculated on each previous weekly CT image, and accumulated using DIR. Thus, for each voxel, the volume-change and delivered dose was calculated for each time-point. The data was binned according to when the volume-change first increased by a threshold volume (10%–100%, in 10% increments), and the average delivered dose calculated for each bin. Results: The average dose resulting in a voxel volume increase of 10–100% was 21.6 to 45.9Gy, respectively. The mean population dose to give a 50% volume increase was 36.3±4.4Gy, (range:29.8 to 43.5Gy). The average week of 50% response was 4.1 (range:4.9 to 2.8 weeks). All 18 patients showed similar dose to first response curves, showing a common trend in the initial inflammatoryresponse. Conclusion: We extracted the dose-response curve of the esophagus on a voxel-to-voxel level. This may be useful for estimating the esophagus response (and patient symptoms

  17. Skeletal dosimetry for external exposures to photons based on {mu}CT images of spongiosa: Consideration of voxel resolution, cluster size, and medullary bone surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kramer, R.; Khoury, H. J.; Vieira, J. W.; Brown, K. A. Robson [Departamento de Energia Nuclear, Universidade Federal de Pernambuco, Avenida Professor Luiz Freire 1000, Cidade Universitaria, CEP 50740-540, Recife, Pernambuco (Brazil); Centro Federal de Educacao Tecnologica de Pernambuco, Avenida Professor Luiz Freire 500, CEP 50740-540, Recife, Pernambuco, Brazil and Escola Politecnica, UPE, Rua Benfica 455, CEP 50751-460, Recife, Pernambuco (Brazil); Imaging Laboratory, Department of Archaeology and Anthropology, University of Bristol, 43 Woodland Road, Bristol BS8 1UU (United Kingdom)

    2009-11-15

    Skeletal dosimetry based on {mu}CT images of trabecular bone has recently been introduced to calculate the red bone marrow (RBM) and the bone surface cell (BSC) equivalent doses in human phantoms for external exposure to photons. In order to use the {mu}CT images for skeletal dosimetry, spongiosa voxels in the skeletons were replaced at run time by so-called micromatrices, which have exactly the size of a spongiosa voxel and contain segmented trabecular bone and marrow microvoxels. A cluster (=parallelepiped) of 2x2x2=8 micromatrices was used systematically and periodically throughout the spongiosa volume during the radiation transport calculation. Systematic means that when a particle leaves a spongiosa voxel to enter into a neighboring spongiosa voxel, then the next micromatrix in the cluster will be used. Periodical means that if the particle travels through more than two spongiosa voxels in a row, then the cluster will be repeated. Based on the bone samples available at the time, clusters of up to 3x3x3=27 micromatrices were studied. While for a given trabecular bone volume fraction the whole-body RBM equivalent dose showed converging results for cluster sizes between 8 and 27 micromatrices, this was not the case for the BSC equivalent dose. The BSC equivalent dose seemed to be very sensitive to the number, form, and thickness of the trabeculae. In addition, the cluster size and/or the microvoxel resolution were considered to be possible causes for the differences observed. In order to resolve this problem, this study used a bone sample large enough to extract clusters containing up to 8x8x8=512 micromatrices and which was scanned with two different voxel resolutions. Taking into account a recent proposal, this investigation also calculated the BSC equivalent dose on medullary surfaces of cortical bone in the arm and leg bones. The results showed (1) that different voxel resolutions have no effect on the RBM equivalent dose but do influence the BSC equivalent

  18. Analysis of multiplex gene expression maps obtained by voxelation

    Directory of Open Access Journals (Sweden)

    Smith Desmond J

    2009-04-01

    Full Text Available Abstract Background Gene expression signatures in the mammalian brain hold the key to understanding neural development and neurological disease. Researchers have previously used voxelation in combination with microarrays for acquisition of genome-wide atlases of expression patterns in the mouse brain. On the other hand, some work has been performed on studying gene functions, without taking into account the location information of a gene's expression in a mouse brain. In this paper, we present an approach for identifying the relation between gene expression maps obtained by voxelation and gene functions. Results To analyze the dataset, we chose typical genes as queries and aimed at discovering similar gene groups. Gene similarity was determined by using the wavelet features extracted from the left and right hemispheres averaged gene expression maps, and by the Euclidean distance between each pair of feature vectors. We also performed a multiple clustering approach on the gene expression maps, combined with hierarchical clustering. Among each group of similar genes and clusters, the gene function similarity was measured by calculating the average gene function distances in the gene ontology structure. By applying our methodology to find similar genes to certain target genes we were able to improve our understanding of gene expression patterns and gene functions. By applying the clustering analysis method, we obtained significant clusters, which have both very similar gene expression maps and very similar gene functions respectively to their corresponding gene ontologies. The cellular component ontology resulted in prominent clusters expressed in cortex and corpus callosum. The molecular function ontology gave prominent clusters in cortex, corpus callosum and hypothalamus. The biological process ontology resulted in clusters in cortex, hypothalamus and choroid plexus. Clusters from all three ontologies combined were most prominently expressed in

  19. Traceable Pyrgeometer Calibrations

    Energy Technology Data Exchange (ETDEWEB)

    Dooraghi, Mike; Kutchenreiter, Mark; Reda, Ibrahim; Habte, Aron; Sengupta, Manajit; Andreas, Afshin; Newman, Martina

    2016-05-02

    This poster presents the development, implementation, and operation of the Broadband Outdoor Radiometer Calibrations (BORCAL) Longwave (LW) system at the Southern Great Plains Radiometric Calibration Facility for the calibration of pyrgeometers that provide traceability to the World Infrared Standard Group.

  20. Calibration of sound calibrators: an overview

    Science.gov (United States)

    Milhomem, T. A. B.; Soares, Z. M. D.

    2016-07-01

    This paper presents an overview of calibration of sound calibrators. Initially, traditional calibration methods are presented. Following, the international standard IEC 60942 is discussed emphasizing parameters, target measurement uncertainty and criteria for conformance to the requirements of the standard. Last, Regional Metrology Organizations comparisons are summarized.

  1. Construction of Chinese adult male phantom library and its application in the virtual calibration of in vivo measurement

    Science.gov (United States)

    Chen, Yizheng; Qiu, Rui; Li, Chunyan; Wu, Zhen; Li, Junli

    2016-03-01

    In vivo measurement is a main method of internal contamination evaluation, particularly for large numbers of people after a nuclear accident. Before the practical application, it is necessary to obtain the counting efficiency of the detector by calibration. The virtual calibration based on Monte Carlo simulation usually uses the reference human computational phantom, and the morphological difference between the monitored personnel with the calibrated phantom may lead to the deviation of the counting efficiency. Therefore, a phantom library containing a wide range of heights and total body masses is needed. In this study, a Chinese reference adult male polygon surface (CRAM_S) phantom was constructed based on the CRAM voxel phantom, with the organ models adjusted to match the Chinese reference data. CRAMS phantom was then transformed to sitting posture for convenience in practical monitoring. Referring to the mass and height distribution of the Chinese adult male, a phantom library containing 84 phantoms was constructed by deforming the reference surface phantom. Phantoms in the library have 7 different heights ranging from 155 cm to 185 cm, and there are 12 phantoms with different total body masses in each height. As an example of application, organ specific and total counting efficiencies of Ba-133 were calculated using the MCNPX code, with two series of phantoms selected from the library. The influence of morphological variation on the counting efficiency was analyzed. The results show only using the reference phantom in virtual calibration may lead to an error of 68.9% for total counting efficiency. Thus the influence of morphological difference on virtual calibration can be greatly reduced using the phantom library with a wide range of masses and heights instead of a single reference phantom.

  2. A comparison of three Deformable Image Registration Algorithms in 4DCT using conventional contour based methods and voxel-by-voxel comparison methods.

    Directory of Open Access Journals (Sweden)

    Mirek eFatyga

    2015-02-01

    Full Text Available Background: Commonly used methods of assessing the accuracy of Deformable Image Registration (DIR rely on image segmentation or landmark selection. These methods are very labor intensive and thus limited to relatively small number of image pairs. The direct voxel-by-voxel comparison can be automated to examine fluctuations in DIR quality on a long series of image pairs.Methods: A voxel-by-voxel comparison of three DIR algorithms applied to lung patients is presented. Registrations are compared by comparing volume histograms formed both with individual DIR maps and with a voxel-by-voxel subtraction of the two maps. When two DIR maps agree one concludes that both maps are interchangeable in treatment planning applications, though one cannot conclude that either one agrees with the ground truth. If two DIR maps significantly disagree one concludes that at least one of the maps deviates from the ground truth. We use the method to compare three DIR algorithms applied to peak inhale-peak exhale registrations of 4DFBCT data obtained from thirteen patients. Results: All three algorithms appear to be nearly equivalent when compared using DICE similarity coefficients. A comparison based on Jacobian Volume Histograms shows that all three algorithms measure changes in total volume of the lungs with reasonable accuracy, but show large differences in the variance of Jacobian distribution on all contoured structures. Analysis of voxel-by-voxel subtraction of DIR maps shows that the three algorithms differ to a degree which is sufficient to create a potential for dosimetric discrepancy during dose accumulation.Conclusions: DIR algorithms can perform well in some clinical applications, while potentially fail in others. These algorithms are best treated as potentially useful approximations of tissue deformation that need to be separately validated for every intended clinical application.

  3. Connecting horizon pixels and interior voxels of a black hole

    Energy Technology Data Exchange (ETDEWEB)

    Nicolini, Piero, E-mail: nicolini@fias.uni-frankfurt.de [Frankfurt Institute for Advanced Studies (FIAS), Ruth-Moufang-Str. 1, 60438 Frankfurt am Main (Germany); Institut für Theoretische Physik, J.W. Goethe-Universität, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany); Singleton, Douglas, E-mail: dougs@csufresno.edu [Department of Physics, California State University, Fresno, CA 93740-8031 (United States); Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, Distrito Federal, 04510 (Mexico)

    2014-11-10

    In this paper we discuss to what extent one can infer details of the interior structure of a black hole based on its horizon. Recalling that black hole thermal properties are connected to the non-classical nature of gravity, we circumvent the restrictions of the no-hair theorem by postulating that the black hole interior is singularity free due to violations of the usual energy conditions. Further these conditions allow one to establish a one-to-one, holographic projection between Planckian areal “bits” on the horizon and “voxels”, representing the gravitational degrees of freedom in the black hole interior. We illustrate the repercussions of this idea by discussing an example of the black hole interior consisting of a de Sitter core postulated to arise from the local graviton quantum vacuum energy. It is shown that the black hole entropy can emerge as the statistical entropy of a gas of voxels.

  4. Nanoscale voxel spectroscopy by simultaneous EELS and EDS tomography.

    Science.gov (United States)

    Haberfehlner, Georg; Orthacker, Angelina; Albu, Mihaela; Li, Jiehua; Kothleitner, Gerald

    2014-11-01

    Extending the capabilities of electron tomography with advanced imaging techniques and novel data processing methods, can augment the information content in three-dimensional (3D) reconstructions from projections taken in the transmission electron microscope (TEM). In this work we present the application of simultaneous electron energy-loss spectroscopy (EELS) and energy-dispersive X-ray spectroscopy (EDS) to scanning TEM tomography. Various tools, including refined tilt alignment procedures, multivariate statistical analysis and total-variation minimization enable the 3D reconstruction of analytical tomograms, providing 3D analytical metrics of materials science samples at the nanometer scale. This includes volumetric elemental maps, and reconstructions of EDS, low-loss and core-loss EELS spectra as four-dimensional spectrum volumes containing 3D local voxel spectra. From these spectra, compositional, 3D localized elemental analysis becomes possible opening the pathway to 3D nanoscale elemental quantification.

  5. Voxel datacubes for 3D visualization in Blender

    CERN Document Server

    Gárate, Matías

    2016-01-01

    The growth of computational astrophysics and complexity of multidimensional datasets evidences the need for new versatile visualization tools for both analysis and presentation of the data. In this work we show how to use the open source software Blender as a 3D visualization tool to study and visualize numerical simulation results, focusing on astrophysical hydrodynamic experiments. With a datacube as input, the software can generate a volume rendering of the 3D data, show the evolution of a simulation in time, and do a fly-around camera animation to highlight the points of interest. We explain the process to import simulation outputs into Blender using the Voxel Data format, and how to set up a visualization scene in the software interface. This method allows scientists to perform a complementary visual analysis of their data, and display their results in an appealing way, both for outreach and science presentations.

  6. Development of prostate voxel models for brachytherapy treatment

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Adriano M.; Reis, Lucas P.; Grynberg, Suely E., E-mail: amsantos@cdtn.b [Center for Development of Nuclear Technology (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2011-07-01

    The tools developed recently in the areas of computer graphics and animation movies to computer games allow the creation of new voxel anthropomorphic phantoms with better resolution and thus, more anatomical details. These phantoms can be used in nuclear applications, especially in radiation protection for estimating doses in cases of occupational or accidental radioactive incidents, and in medical and biological applications. For dose estimates, the phantoms are coupled to a Monte Carlo code, which will be responsible for the transport of radiation in this environment. This study aimed to develop a computational tool to estimate the isodose curves in the prostate after brachytherapy seed implants. For this, we have created a model called FANTPROST in the shape of a 48 mm side cube, with a standard prostate inserted in the center of this cube with different distributions of brachytherapy seeds in this volume. The prostate, according to this model, was obtained from the phantom voxels MASH2 developed by Numerical Dosimetry Group, Department of Nuclear Energy - Federal University of Pernambuco. The modeling of the seeds, added to FANTPROST, was done through the use of geometric information of Iodine-125 Amersham 6711 commercial seed. The simulations were performed by the code MCNP5 for spatial distributions containing different amounts of seeds within the FANTPROST. The obtained curves allowed an estimation of the behavior of the maximum dose that decreases with distance, showing that this tool can be used for a more accurate analysis of the effects produced by the presence of such seeds in the prostate and its vicinity. (author)

  7. 3D change detection in staggered voxels model for robotic sensing and navigation

    Science.gov (United States)

    Liu, Ruixu; Hampshire, Brandon; Asari, Vijayan K.

    2016-05-01

    3D scene change detection is a challenging problem in robotic sensing and navigation. There are several unpredictable aspects in performing scene change detection. A change detection method which can support various applications in varying environmental conditions is proposed. Point cloud models are acquired from a RGB-D sensor, which provides the required color and depth information. Change detection is performed on robot view point cloud model. A bilateral filter smooths the surface and fills the holes as well as keeps the edge details on depth image. Registration of the point cloud model is implemented by using Random Sample Consensus (RANSAC) algorithm. It uses surface normal as the previous stage for the ground and wall estimate. After preprocessing the data, we create a point voxel model which defines voxel as surface or free space. Then we create a color model which defines each voxel that has a color by the mean of all points' color value in this voxel. The preliminary change detection is detected by XOR subtract on the point voxel model. Next, the eight neighbors for this center voxel are defined. If they are neither all `changed' voxels nor all `no changed' voxels, a histogram of location and hue channel color is estimated. The experimental evaluations performed to evaluate the capability of our algorithm show promising results for novel change detection that indicate all the changing objects with very limited false alarm rate.

  8. Probing the mysterious underpinnings of multi-voxel fMRI analyses.

    Science.gov (United States)

    Op de Beeck, Hans P

    2010-04-01

    Various arguments have been proposed for or against sub-voxel sensitivity or hyperacuity in functional magnetic resonance imaging (fMRI) at standard resolution. Sub-voxel sensitivity might exist, but nevertheless the performance of multi-voxel fMRI analyses is very likely to be dominated by a larger-scale organization, even if this organization is very weak. Up to now, most arguments are indirect in nature: they do not in themselves proof or contradict sub-voxel sensitivity, but they are suggestive, seem consistent or not with sub-voxel sensitivity, or show that the principle might or might not work. Here the previously proposed smoothing argument against hyperacuity is extended with simulations that include more realistic signal, noise, and analysis properties than any of the simulations presented before. These simulations confirm the relevance of the smoothing approach to find out the scale of the functional maps that underlie the outcome of multi-voxel analyses, at least in relative terms (differences in the scale of different maps). However, image smoothing, like most other arguments in the literature, is an indirect argument, and at the end of the day such arguments are not sufficient to decide the issue on whether and how much sub-voxel maps contribute. A few suggestions are made about the type of evidence that is needed to help us understand the as yet mysterious underpinnings of multi-voxel fMRI analyses.

  9. Computational strategies for iterative solutions of large fem applications employing voxel data

    NARCIS (Netherlands)

    R. van Rietbergen (Bert); H.H. Weinans (Harrie); R. Huiskes (Rik); B.J.W. Polman (Ben)

    1996-01-01

    textabstractFE-models for structural solid mechanics analyses can be readily generated from computer images via a 'voxel convesion' method, whereby voxels in a two- or three-dimesional computer image are directly translated to elements in a FE-model. The fact that all elements thus generated are the

  10. Study on the consistency of the voxel of two photon polymerization with inclined beam

    Science.gov (United States)

    Cheng, Kai; Zhou, Xiaoqin; Zheng, Xu; Lin, Jieqiong

    2016-12-01

    In the process of two photon polymerization, the focused beam should be perpendicular to the materials to be processed. But actually it is hard to control, because of the errors of the optical system and the three-dimensional motion platform. So, the inconsistencies of voxels in size and angle due to the errors mentioned above will seriously impact the surface quality of the products. In this paper, the size, angle and location of the titled voxels formed by inclined beam are simulated according to matrix optics and polymerization theory. According to the simulation results, a method for angle errors compensation with the aid of scanning galvanometer is proposed. Although the angle of the voxels can be controlled by scanning galvanometer, but the deflection angles of the scanning galvanometer have a certain range, it should be lower than 3°, or the deformation of the voxels will be serious. Therefore the consistency of the voxel in both size and angle will be ensured.

  11. Rapid three-dimensional quantification of voxel-wise collagen fiber orientation.

    Science.gov (United States)

    Liu, Zhiyi; Quinn, Kyle P; Speroni, Lucia; Arendt, Lisa; Kuperwasser, Charlotte; Sonnenschein, Carlos; Soto, Ana M; Georgakoudi, Irene

    2015-07-01

    Defining fiber orientation at each voxel within a 3D biomedical image stack is potentially useful for a variety of applications, including cancer, wound healing and tissue regeneration. Current methods are typically computationally intensive or inaccurate. Herein, we present a 3D weighted orientation vector summation algorithm, which is a generalization of a previously reported 2D vector summation technique aimed at quantifying collagen fiber orientations simultaneously at each voxel of an image stack. As a result, voxel-wise fiber orientation information with 4° to 5° accuracy can be determined, and the computational time required to analyze a typical stack with the size of 512x512x100 voxels is less than 5 min. Thus, this technique enables the practical extraction of voxel-specific orientation data for characterizing structural anisotropy in 3D specimens. As examples, we use this approach to characterize the fiber organization in an excised mouse mammary gland and a 3D breast tissue model.

  12. A HUMANIZED CLINICALLY CALIBRATED QUANTITATIVE SYSTEMS PHARMACOLOGY MODEL FOR HYPOKINETIC MOTOR SYMPTOMS IN PARKINSON’S DISEASE

    Directory of Open Access Journals (Sweden)

    Hugo eGeerts

    2016-02-01

    Full Text Available The current treatment of Parkinson’s disease with dopamine-centric approaches such as L-DOPA and dopamine agonists, although very succesfull, is in need of alternative treatment strategies, both in terms of disease modification and symptom management. Various non-dopaminergic treatment approaches did not result in a clear clinical benefit, despite showing a clear effect in preclinical animal models. In addition, polypharmacy is common, sometimes leading to unintended effects on non-motor symptoms such as in cognitive and psychiatric domains. To explore novel targets for symptomatic treatment and possible synergistic pharmacodynamic effects between different drugs, we developed a Quantitative Systems Pharmacology (QSP platform of the closed cortico-striatal-thalamic-cortical basal ganglia loop of the dorsal motor circuit. This mechanism-based simulation platform is based on the known neuro-anatomy and neurophysiology of the basal ganglia and explicitly incorporates domain expertise in a formalized way. The calculated beta/gamma power ratio of the local field potential in the subthalamic nucleus correlates well (R2=0.71 with clinically observed extra-pyramidal symptoms triggered by antipsychotics during schizophrenia treatment (43 drug-dose combinations. When incorporating Parkinsonian (PD pathology and reported compensatory changes, the computer model suggests a major increase in b/g ratio (corresponding to bradykinesia and rigidity from a dopamine depletion of 70% onwards. The correlation between the outcome of the QSP model and the reported changes in UPDRS III Motor Part for 22 placebo-normalized drug-dose combinations is R2=0.84. The model also correctly recapitulates the lack of clinical benefit for perampanel, MK-0567 and flupirtine and offers a hypothesis for the translational disconnect. Finally, using human PET imaging studies with placebo response, the computer model predicts well the placebo response for chronic treatment, but not

  13. Study on force feeback of acupuncture manipulation at Jianliao(TE 14)based on VOXEL-MAN%基于VOXEL-MAN操作平台肩(骨谬)穴的力反馈研究

    Institute of Scientific and Technical Information of China (English)

    王海生; 严振国; 程卓; 邵水金; 庄天戈

    2009-01-01

    目的:通过在肩(骨谬)穴周围组织三维重建的基础上,探讨在该穴进针时的力学虚拟,便于初学者对穴位进针有感性认识.方法:在VOXEL-MAN操作平台中,通过对肩(骨谬)穴相关组织进行分割和数学建模的方式进行重建,即视觉再现;并构建力学模型,与虚拟人相关数据相融合,即触觉再现;联通视觉再现模块和触觉再现模块,实现力反馈仪和虚拟人操作平台之间数据交流.结果:在Linux系统下,通过力反馈仪,操作者可以体验肩(骨谬)穴进针时,针尖穿过各组织以及均匀提插时的力学变化.结论:在VOXEL-MAN操作平台的基础上,通过力反馈仪可以较为完美地再现肩(骨谬)穴进针时视觉和触觉的变化,以便于初学者临摹学习和应用.%Objective To discuss the mechanical virtual reality when acupuncture on Jianliao (TE 14) so as to get perform perceptual knowledge of acupuncture for beginners through studying 3D reconstruction of surrounding tissues of this acupoint. Methods Related tissues were segmented and reconstructed by establishing mathematics model based on the operational platform of VOXEL-MAN (vision reappearance); and mechanical model was constructed and fused with related data of virtual human (touch reappearance); data communication between the force feedback apparatus and the operational platform of virtual human were set up by interchanging vision reappearance module and touch reappearance module. Results In Linux system, the operator could experience the mechanical changes while needle-tip passing various tissues of Jianliao (TE 14) as well as lifting and thrusting evenly in needling process through the force feedback apparatus. Conclusion Based on the platform of VOXEL-MAN, the sensation of needling at jianliao (TE 14) could be reappeared idealy by strength feedback instrument, so that the beginners could imitate, learn and practice the virtual acupuncture.

  14. A free database of radionuclide voxel S values for the dosimetry of nonuniform activity distributions

    Science.gov (United States)

    Lanconelli, N.; Pacilio, M.; Lo Meo, S.; Botta, F.; Di Dia, A.; Torres Aroche, L. A.; Coca Pérez, M. A.; Cremonesi, M.

    2012-01-01

    The increasing availability of SPECT/CT devices with advanced technology offers the opportunity for the accurate assessment of the radiation dose to the biological target volume during radionuclide therapy. Voxel dosimetry can be performed employing direct Monte Carlo radiation transport simulations, based on both morphological and functional images of the patient. On the other hand, for voxel dosimetry calculations the voxel S value method can be considered an easier approach than patient-specific Monte Carlo simulations, ensuring a good dosimetric accuracy at least for anatomic regions which are characterized by uniform density tissue. However, this approach has been limited because of the lack of tabulated S values for different voxel dimensions and radionuclides. The aim of this work is to provide a free dataset of values which can be used for voxel dosimetry in targeted radionuclide studies. Seven different radionuclides (89Sr, 90Y, 131I, 153Sm, 177Lu, 186Re, 188Re), and 13 different voxel sizes (2.21, 2.33, 2.4, 3, 3.59, 3.9, 4, 4.42, 4.8, 5, 6, 6.8 and 9.28 mm) are considered. Voxel S values are calculated performing simulations of monochromatic photon and electron sources in two different homogeneous tissues (soft tissue and bone) with DOSXYZnrc code, and weighting the contributions on the basis of the radionuclide emission spectra. The outcomes are validated by comparison with Monte Carlo simulations obtained with other codes (PENELOPE and MCNP4c) performing direct simulation of the radionuclide emission spectra. The differences among the different Monte Carlo codes are of the order of a few per cent when considering the source voxel and the bremsstrahlung tail, whereas the highest differences are observed at a distance close to the maximum continuous slowing down approximation range of electrons. These discrepancies would negligibly affect dosimetric assessments. The dataset of voxel S values can be freely downloaded from the website www.medphys.it.

  15. A free database of radionuclide voxel S values for the dosimetry of nonuniform activity distributions.

    Science.gov (United States)

    Lanconelli, N; Pacilio, M; Lo Meo, S; Botta, F; Di Dia, A; Aroche, A Torres; Pérez, M A Coca; Cremonesi, M

    2012-01-21

    The increasing availability of SPECT/CT devices with advanced technology offers the opportunity for the accurate assessment of the radiation dose to the biological target volume during radionuclide therapy. Voxel dosimetry can be performed employing direct Monte Carlo radiation transport simulations, based on both morphological and functional images of the patient. On the other hand, for voxel dosimetry calculations the voxel S value method can be considered an easier approach than patient-specific Monte Carlo simulations, ensuring a good dosimetric accuracy at least for anatomic regions which are characterized by uniform density tissue. However, this approach has been limited because of the lack of tabulated S values for different voxel dimensions and radionuclides. The aim of this work is to provide a free dataset of values which can be used for voxel dosimetry in targeted radionuclide studies. Seven different radionuclides (89Sr, 90Y, 131I, 153Sm, 177Lu, 186Re, 188Re), and 13 different voxel sizes (2.21, 2.33, 2.4, 3, 3.59, 3.9, 4, 4.42, 4.8, 5, 6, 6.8 and 9.28 mm) are considered. Voxel S values are calculated performing simulations of monochromatic photon and electron sources in two different homogeneous tissues (soft tissue and bone) with DOSXYZnrc code, and weighting the contributions on the basis of the radionuclide emission spectra. The outcomes are validated by comparison with Monte Carlo simulations obtained with other codes (PENELOPE and MCNP4c) performing direct simulation of the radionuclide emission spectra. The differences among the different Monte Carlo codes are of the order of a few per cent when considering the source voxel and the bremsstrahlung tail, whereas the highest differences are observed at a distance close to the maximum continuous slowing down approximation range of electrons. These discrepancies would negligibly affect dosimetric assessments. The dataset of voxel S values can be freely downloaded from the website www.medphys.it.

  16. What do differences between multi-voxel and univariate analysis mean? How subject-, voxel-, and trial-level variance impact fMRI analysis.

    Science.gov (United States)

    Davis, Tyler; LaRocque, Karen F; Mumford, Jeanette A; Norman, Kenneth A; Wagner, Anthony D; Poldrack, Russell A

    2014-08-15

    Multi-voxel pattern analysis (MVPA) has led to major changes in how fMRI data are analyzed and interpreted. Many studies now report both MVPA results and results from standard univariate voxel-wise analysis, often with the goal of drawing different conclusions from each. Because MVPA results can be sensitive to latent multidimensional representations and processes whereas univariate voxel-wise analysis cannot, one conclusion that is often drawn when MVPA and univariate results differ is that the activation patterns underlying MVPA results contain a multidimensional code. In the current study, we conducted simulations to formally test this assumption. Our findings reveal that MVPA tests are sensitive to the magnitude of voxel-level variability in the effect of a condition within subjects, even when the same linear relationship is coded in all voxels. We also find that MVPA is insensitive to subject-level variability in mean activation across an ROI, which is the primary variance component of interest in many standard univariate tests. Together, these results illustrate that differences between MVPA and univariate tests do not afford conclusions about the nature or dimensionality of the neural code. Instead, targeted tests of the informational content and/or dimensionality of activation patterns are critical for drawing strong conclusions about the representational codes that are indicated by significant MVPA results.

  17. Empirical comparison of maximal voxel and non-isotropic adjusted cluster extent results in a voxel-based morphometry study of comorbid learning disability with schizophrenia.

    Science.gov (United States)

    Moorhead, T William J; Job, Dominic E; Spencer, Michael D; Whalley, Heather C; Johnstone, Eve C; Lawrie, Stephen M

    2005-11-15

    We present an empirical comparison of cluster extent and maximal voxel results in a voxel-based morphometry (VBM) study of brain structure. The cluster extents are adjusted for underlying deviation from uniform smoothness. We implement this comparison on a four-group cohort that has previously shown evidence of a neuro-developmental component in schizophrenia (Moorhead, T.W.J., Job, D.E., Whalley, H.C., Sanderson, T.L., Johnstone, E.C. and Lawrie, S.M. 2004. Voxel-based morphometry of comorbid schizophrenia and learning disability: analyses in normalized and native spaces using parametric and nonparametric statistical methods. NeuroImage 22: 188-202.). We find that adjusted cluster extent results provide information on the nature of deficits that occur in the schizophrenia affected groups, and these important structural differences are not all shown in maximal voxel results. The maximal voxel and cluster extent results are corrected for multiple comparisons using Random Fields (RF) methods. In order to apply the cluster extent measures, we propose a post-hoc method for determining the primary threshold in the analysis. Unadjusted cluster extent results are reported, for these, no allowance is made for non-isotropic smoothness, and comparison with the adjusted extent results shows that the unadjusted results can be either conservative or anti-conservative depending upon the underlying tissue distributions.

  18. Voxel-based morphometry in autopsy proven PSP and CBD.

    Science.gov (United States)

    Josephs, Keith A; Whitwell, Jennifer L; Dickson, Dennis W; Boeve, Bradley F; Knopman, David S; Petersen, Ronald C; Parisi, Joseph E; Jack, Clifford R

    2008-02-01

    The aim of this study was to compare the patterns of grey and white matter atrophy on MRI in autopsy confirmed progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD), and to determine whether the patterns vary depending on the clinical syndrome. Voxel-based morphometry was used to compare patterns of atrophy in 13 PSP and 11 CBD subjects and 24 controls. PSP and CBD subjects were also subdivided into those with a dominant dementia or extrapyramidal syndrome. PSP subjects showed brainstem atrophy with involvement of the cortex and underlying white matter. Frontoparietal grey and subcortical grey matter atrophy occurred in CBD. When subdivided, PSP subjects with an extrapyramidal syndrome had more brainstem atrophy and less cortical atrophy than CBD subjects with an extrapyramidal syndrome. PSP subjects with a dementia syndrome had more subcortical white matter atrophy than CBD subjects with a dementia syndrome. These results show regional differences between PSP and CBD that are useful in predicting the underlying pathology, and help to shed light on the in vivo distribution of regional atrophy in PSP and CBD.

  19. Calibration Curve for Dicentric Chromosomes Induced in Human Blood Lymphocytes Exposed to Gamma Rays at a Dose Rate of 12.5 mGy/s.

    Science.gov (United States)

    Que, Tran; Duy, Pham Ngoc; Luyen, Bui Thi Kim

    2016-01-01

    To develop a calibration curve for induction of dicentric chromosomes by radiation, we have used a 60Co gamma-ray source with dose rate of 12.5 mGy/s. Whole blood from 15 healthy donors was collected. Whole blood from each donor was divided equally into 8 parts for exposing to supposedly physical doses 0, 0.30, 0.50, 1.00, 1.50, 2.00, 3.00 and 4.00 Gy for a independent calibration curve. Whole blood from 15 donors was used to calibrate dose - effect and statistical for general calibration curve. Using Poisson test (U-test) for the distribution of dicentric chromosomes in the metaphases to determine the uniformity of the radiation field. The average from 15 independent calibration curves of linear correlated coefficient was determined to be r (y, d) = 0.5136 ± 0.0038. The model equation derived is y = aD + bD(2) + C. The calibration equation of dose-effect was y = 1.01D + 4.43D(2) + 0.56.

  20. Trinocular Calibration Method Based on Binocular Calibration

    Directory of Open Access Journals (Sweden)

    CAO Dan-Dan

    2012-10-01

    Full Text Available In order to solve the self-occlusion problem in plane-based multi-camera calibration system and expand the measurement range, a tri-camera vision system based on binocular calibration is proposed. The three cameras are grouped into two pairs, while the public camera is taken as the reference to build the global coordinate. By calibration of the measured absolute distance and the true absolute distance, global calibration is realized. The MRE (mean relative error of the global calibration of the two camera pairs in the experiments can be as low as 0.277% and 0.328% respectively. Experiment results show that this method is feasible, simple and effective, and has high precision.

  1. Outstanding Trend of Voxel-Man%可视人真实可视化的突出进展Voxel-Man(2)

    Institute of Scientific and Technical Information of China (English)

    秦笃烈

    2004-01-01

    @@ 3 Voxel-Man的应用 Voxel-Man既是一套3D数字解剖学的生动而杰出的应用程序,也是一个开发其他应用程序的平台.K.H.Hohne教授领导的研究人员不断在利用这个平台开发各种有价值、有新意的医学教育和临床应用.

  2. Postprocessing of Voxel-Based Topologies for Additive Manufacturing Using the Computational Geometry Algorithms Library (CGAL)

    Science.gov (United States)

    2015-06-01

    surfaces such as Catmull-Clark or Doo-Sabin. 2.1 Topology Optimization Topology optimization applied to structural problems using a voxel/pixel geometry...O. Topology optimization: Theory, methods and appli - cations. Springer; 2003. (Engineering Online Library). 2. Brackett D, Ashcroft I, Hague R. 22nd...ARL-MR-0892• JUNE 2015 US Army Research Laboratory Postprocessing of Voxel-Based Topologies forAdditive Manufacturing Using the Compu-tational

  3. Automated voxel classification used with atlas-guided diffuse optical tomography for assessment of functional brain networks in young and older adults.

    Science.gov (United States)

    Li, Lin; Cazzell, Mary; Babawale, Olajide; Liu, Hanli

    2016-10-01

    Atlas-guided diffuse optical tomography (atlas-DOT) is a computational means to image changes in cortical hemodynamic signals during human brain activities. Graph theory analysis (GTA) is a network analysis tool commonly used in functional neuroimaging to study brain networks. Atlas-DOT has not been analyzed with GTA to derive large-scale brain connectivity/networks based on near-infrared spectroscopy (NIRS) measurements. We introduced an automated voxel classification (AVC) method that facilitated the use of GTA with atlas-DOT images by grouping unequal-sized finite element voxels into anatomically meaningful regions of interest within the human brain. The overall approach included volume segmentation, AVC, and cross-correlation. To demonstrate the usefulness of AVC, we applied reproducibility analysis to resting-state functional connectivity measurements conducted from 15 young adults in a two-week period. We also quantified and compared changes in several brain network metrics between young and older adults, which were in agreement with those reported by a previous positron emission tomography study. Overall, this study demonstrated that AVC is a useful means for facilitating integration or combination of atlas-DOT with GTA and thus for quantifying NIRS-based, voxel-wise resting-state functional brain networks.

  4. A novel, optimized approach of voxel division for water vapor tomography

    Science.gov (United States)

    Yao, Yibin; Zhao, Qingzhi

    2017-02-01

    Water vapor information with highly spatial and temporal resolution can be acquired using Global Navigation Satellite System (GNSS) water vapor tomography technique. Usually, the targeted tomographic area is discretized into a number of voxels and the water vapor distribution can be reconstructed using a large number of GNSS signals which penetrate the entire tomographic area. Due to the influence of geographic distribution of receivers and geometric location of satellite constellation, many voxels located at the bottom and the side of research area are not crossed by signals, which would undermine the quality of tomographic result. To alleviate this problem, a novel, optimized approach of voxel division is here proposed which increases the number of voxels crossed by signals. On the vertical axis, a 3D water vapor profile is utilized, which is derived from radiosonde data for many years, to identify the maximum height of tomography space. On the horizontal axis, the total number of voxel crossed by signal is enhanced, based on the concept of non-uniform symmetrical division of horizontal voxels. In this study, tomographic experiments are implemented using GPS data from Hong Kong Satellite Positioning Reference Station Network, and tomographic result is compared with water vapor derived from radiosonde and European Center for Medium-Range Weather Forecasting (ECMWF). The result shows that the Integrated Water Vapour (IWV), RMS, and error distribution of the proposed approach are better than that of traditional method.

  5. Informational connectivity: identifying synchronized discriminability of multi-voxel patterns across the brain.

    Science.gov (United States)

    Coutanche, Marc N; Thompson-Schill, Sharon L

    2013-01-01

    The fluctuations in a brain region's activation levels over a functional magnetic resonance imaging (fMRI) time-course are used in functional connectivity (FC) to identify networks with synchronous responses. It is increasingly recognized that multi-voxel activity patterns contain information that cannot be extracted from univariate activation levels. Here we present a novel analysis method that quantifies regions' synchrony in multi-voxel activity pattern discriminability, rather than univariate activation, across a timeseries. We introduce a measure of multi-voxel pattern discriminability at each time-point, which is then used to identify regions that share synchronous time-courses of condition-specific multi-voxel information. This method has the sensitivity and access to distributed information that multi-voxel pattern analysis enjoys, allowing it to be applied to data from conditions not separable by univariate responses. We demonstrate this by analyzing data collected while people viewed four different types of man-made objects (typically not separable by univariate analyses) using both FC and informational connectivity (IC) methods. IC reveals networks of object-processing regions that are not detectable using FC. The IC results support prior findings and hypotheses about object processing. This new method allows investigators to ask questions that are not addressable through typical FC, just as multi-voxel pattern analysis (MVPA) has added new research avenues to those addressable with the general linear model (GLM).

  6. Effect of voxel size when calculating patient specific radionuclide dosimetry estimates using direct Monte Carlo simulation.

    Science.gov (United States)

    Hickson, Kevin J; O'Keefe, Graeme J

    2014-09-01

    The scalable XCAT voxelised phantom was used with the GATE Monte Carlo toolkit to investigate the effect of voxel size on dosimetry estimates of internally distributed radionuclide calculated using direct Monte Carlo simulation. A uniformly distributed Fluorine-18 source was simulated in the Kidneys of the XCAT phantom with the organ self dose (kidney ← kidney) and organ cross dose (liver ← kidney) being calculated for a number of organ and voxel sizes. Patient specific dose factors (DF) from a clinically acquired FDG PET/CT study have also been calculated for kidney self dose and liver ← kidney cross dose. Using the XCAT phantom it was found that significantly small voxel sizes are required to achieve accurate calculation of organ self dose. It has also been used to show that a voxel size of 2 mm or less is suitable for accurate calculations of organ cross dose. To compensate for insufficient voxel sampling a correction factor is proposed. This correction factor is applied to the patient specific dose factors calculated with the native voxel size of the PET/CT study.

  7. Voxel classification methodology for rapid Monte Carlo simulation of light propagation in complex media

    Institute of Scientific and Technical Information of China (English)

    Nunu Ren; Heng Zhao; Shouping Zhu; Xiaochao Qu; Hongliang Liu; Zhenhua Hu; Jimin Liang; Jie Tian

    2011-01-01

    @@ Monte Carlo (MC) method is a statistical method for simulating photon propagation in media in the optical molecular imaging field.However, obtaining an accurate result using the method is quite time-consuming,especially because the boundary of the media is complex.A voxel classification method is proposed to reduce the computation cost.All the voxels generated by dividing the media are classified into three types (outside, boundary, and inside) according to the position of the voxel.The classified information is used to determine the relative position of the photon and the intersection between photon path and media boundary in the MC method.The influencing factor8 and effectiveness of the proposed method are analyzed and validated by simulation experiments.%Monte Carlo (MC) method is a statistical method for simulating photon propagation in media in the optical molecular imaging field. However, obtaining an accurate result using the method is quite time-consuming,especially because the boundary of the media is complex. A voxel classification method is proposed to reduce the computation cost. All the voxels generated by dividing the media are classified into three types (outside, boundary, and inside) according to the position of the voxel. The classified information is used to determine the relative position of the photon and the intersection between photon path and media boundary in the MC method. The influencing factors and effectiveness of the proposed method are analyzed and validated by simulation experiments.

  8. Voxel-based morphometry evaluation of patients with photosensitive juvenile myoclonic epilepsy.

    Science.gov (United States)

    Lin, Katia; Jackowski, Andrea Parolin; Carrete, Henrique; de Araújo Filho, Gerardo Maria; Silva, Henrique Hattori; Guaranha, Mirian Salvadori Bittar; Guilhoto, Laura Maria Figueiredo Ferreira; Bressan, Rodrigo Affonseca; Yacubian, Elza Márcia Targas

    2009-10-01

    We aim to investigate structural brain abnormalities in juvenile myoclonic epilepsy (JME) patients with photosensitivity (PS). Sixty JME patients, 19 (32%) of whom were photosensitive, were submitted to 1.5T magnetic resonance voxel-based morphometry (VBM). The control group (CTL) consisted of 30 sex-matched healthy volunteers. JME patients with (JME-PS) and without (JME-NPS) PS did not differ in their duration of disease, treatment or seizure control. VBM revealed significantly reduced bilateral gray matter volume (GMV) in thalami, insula cortices and cerebellar hemispheres; while significantly increased GMV was observed in the right superior frontal, orbitofrontal and medial frontal gyri of the JME group compared to CTL. JME-PS had reduced bilateral GMV of visual cortices when compared with CTL; while it was not seen among JME-NPS patients. Reduced left hippocampus and left inferior frontal gyrus volume was observed among JME-PS compared with JME-NPS. This study demonstrates structural abnormalities beyond the limits of the frontal lobes and provides evidence for the role of the occipital cortex in human PS, reinforcing the existence of functional-anatomic ictogenic networks in JME and the concept of 'system epilepsies'.

  9. Different brain structures associated with artistic and scientific creativity: a voxel-based morphometry study

    Science.gov (United States)

    Shi, Baoguo; Cao, Xiaoqing; Chen, Qunlin; Zhuang, Kaixiang; Qiu, Jiang

    2017-01-01

    Creativity is the ability to produce original and valuable ideas or behaviors. In real life, artistic and scientific creativity promoted the development of human civilization; however, to date, no studies have systematically investigated differences in the brain structures responsible for artistic and scientific creativity in a large sample. Using voxel-based morphometry (VBM), this study identified differences in regional gray matter volume (GMV) across the brain between artistic and scientific creativity (assessed by the Creative Achievement Questionnaire) in 356 young, healthy subjects. The results showed that artistic creativity was significantly negatively associated with the regional GMV of the supplementary motor area (SMA) and anterior cingulate cortex (ACC). In contrast, scientific creativity was significantly positively correlated with the regional GMV of the left middle frontal gyrus (MFG) and left inferior occipital gyrus (IOG). Overall, artistic creativity was associated with the salience network (SN), whereas scientific creativity was associated with the executive attention network and semantic processing. These results may provide an effective marker that can be used to predict and evaluate individuals’ creative performance in the fields of science and art. PMID:28220826

  10. Investigating the brain basis of facial expression perception using multi-voxel pattern analysis.

    Science.gov (United States)

    Wegrzyn, Martin; Riehle, Marcel; Labudda, Kirsten; Woermann, Friedrich; Baumgartner, Florian; Pollmann, Stefan; Bien, Christian G; Kissler, Johanna

    2015-08-01

    Humans can readily decode emotion expressions from faces and perceive them in a categorical manner. The model by Haxby and colleagues proposes a number of different brain regions with each taking over specific roles in face processing. One key question is how these regions directly compare to one another in successfully discriminating between various emotional facial expressions. To address this issue, we compared the predictive accuracy of all key regions from the Haxby model using multi-voxel pattern analysis (MVPA) of functional magnetic resonance imaging (fMRI) data. Regions of interest were extracted using independent meta-analytical data. Participants viewed four classes of facial expressions (happy, angry, fearful and neutral) in an event-related fMRI design, while performing an orthogonal gender recognition task. Activity in all regions allowed for robust above-chance predictions. When directly comparing the regions to one another, fusiform gyrus and superior temporal sulcus (STS) showed highest accuracies. These results underscore the role of the fusiform gyrus as a key region in perception of facial expressions, alongside STS. The study suggests the need for further specification of the relative role of the various brain areas involved in the perception of facial expression. Face processing appears to rely on more interactive and functionally overlapping neural mechanisms than previously conceptualised.

  11. The calibration of PIXIE

    Science.gov (United States)

    Fixsen, D. J.; Chuss, D. T.; Kogut, Alan; Mirel, Paul; Wollack, E. J.

    2016-07-01

    The FIRAS instrument demonstrated the use of an external calibrator to compare the sky to an instrumented blackbody. The PIXIE calibrator is improved from -35 dB to -65 dB. Another significant improvement is the ability to insert the calibrator into either input of the FTS. This allows detection and correction of additional errors, reduces the effective calibration noise by a factor of 2, eliminates an entire class of systematics and allows continuous observations. This paper presents the design and use of the PIXIE calibrator.

  12. Potential of modern technologies for improvement of in vivo calibration.

    Science.gov (United States)

    Franck, D; de Carlan, L; Fisher, H; Pierrat, N; Schlagbauer, M; Wahl, W

    2007-01-01

    In the frame of IDEA project, a research programme has been carried out to study the potential of the reconstruction of numerical anthropomorphic phantoms based on personal physiological data obtained by computed tomography (CT) and Magnetic Resonance Imaging (MRI) for calibration in in vivo monitoring. As a result, new procedures have been developed taking advantage of recent progress in image processing codes that allow, after scanning and rapidly reconstructing a realistic voxel phantom, to convert the whole measurement geometry into computer file to be used on line for MCNP (Monte Carlo N-Particule code) calculations. The present paper overviews the major abilities of the OEDIPE software studies made in the frame of the IDEA project, on the examples of calibration for lung monitoring as well as whole body counting of a real patient.

  13. Metabolic patterns in prion diseases: an FDG PET voxel-based analysis

    Energy Technology Data Exchange (ETDEWEB)

    Prieto, Elena; Dominguez-Prado, Ines; Jesus Ribelles, Maria; Arbizu, Javier [Clinica Universidad de Navarra, Nuclear Medicine Department, Pamplona (Spain); Riverol, Mario; Ortega-Cubero, Sara; Rosario Luquin, Maria; Castro, Purificacion de [Clinica Universidad de Navarra, Neurology Department, Pamplona (Spain)

    2015-09-15

    Clinical diagnosis of human prion diseases can be challenging since symptoms are common to other disorders associated with rapidly progressive dementia. In this context, {sup 18}F-fluorodeoxyglucose (FDG) positron emission tomography (PET) might be a useful complementary tool. The aim of this study was to determine the metabolic pattern in human prion diseases, particularly sporadic Creutzfeldt-Jakob disease (sCJD), the new variant of Creutzfeldt-Jakob disease (vCJD) and fatal familial insomnia (FFI). We retrospectively studied 17 patients with a definitive, probable or possible prion disease who underwent FDG PET in our institution. Of these patients, 12 were diagnosed as sCJD (9 definitive, 2 probable and 1 possible), 1 was diagnosed as definitive vCJD and 4 were diagnosed as definitive FFI. The hypometabolic pattern of each individual and comparisons across the groups of subjects (control subjects, sCJD and FFI) were evaluated using a voxel-based analysis. The sCJD group exhibited a pattern of hypometabolism that affected both subcortical (bilateral caudate, thalamus) and cortical (frontal cortex) structures, while the FFI group only presented a slight hypometabolism in the thalamus. Individual analysis demonstrated a considerable variability of metabolic patterns among patients, with the thalamus and basal ganglia the most frequently affected areas, combined in some cases with frontal and temporal hypometabolism. Patients with a prion disease exhibit a characteristic pattern of brain metabolism presentation in FDG PET imaging. Consequently, in patients with rapidly progressive cognitive impairment, the detection of these patterns in the FDG PET study could orient the diagnosis to a prion disease. (orig.)

  14. Practical intraoperative stereo camera calibration.

    Science.gov (United States)

    Pratt, Philip; Bergeles, Christos; Darzi, Ara; Yang, Guang-Zhong

    2014-01-01

    Many of the currently available stereo endoscopes employed during minimally invasive surgical procedures have shallow depths of field. Consequently, focus settings are adjusted from time to time in order to achieve the best view of the operative workspace. Invalidating any prior calibration procedure, this presents a significant problem for image guidance applications as they typically rely on the calibrated camera parameters for a variety of geometric tasks, including triangulation, registration and scene reconstruction. While recalibration can be performed intraoperatively, this invariably results in a major disruption to workflow, and can be seen to represent a genuine barrier to the widespread adoption of image guidance technologies. The novel solution described herein constructs a model of the stereo endoscope across the continuum of focus settings, thereby reducing the number of degrees of freedom to one, such that a single view of reference geometry will determine the calibration uniquely. No special hardware or access to proprietary interfaces is required, and the method is ready for evaluation during human cases. A thorough quantitative analysis indicates that the resulting intrinsic and extrinsic parameters lead to calibrations as accurate as those derived from multiple pattern views.

  15. Distributed Radio Interferometric Calibration

    CERN Document Server

    Yatawatta, Sarod

    2015-01-01

    Increasing data volumes delivered by a new generation of radio interferometers require computationally efficient and robust calibration algorithms. In this paper, we propose distributed calibration as a way of improving both computational cost as well as robustness in calibration. We exploit the data parallelism across frequency that is inherent in radio astronomical observations that are recorded as multiple channels at different frequencies. Moreover, we also exploit the smoothness of the variation of calibration parameters across frequency. Data parallelism enables us to distribute the computing load across a network of compute agents. Smoothness in frequency enables us reformulate calibration as a consensus optimization problem. With this formulation, we enable flow of information between compute agents calibrating data at different frequencies, without actually passing the data, and thereby improving robustness. We present simulation results to show the feasibility as well as the advantages of distribute...

  16. Medical images of patients in voxel structures in high resolution for Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Boia, Leonardo S.; Menezes, Artur F.; Silva, Ademir X., E-mail: lboia@con.ufrj.b, E-mail: ademir@con.ufrj.b [Universidade Federal do Rio de Janeiro (PEN/COPPE/UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-Graduacao de Engenharia. Programa de Engenharia Nuclear; Salmon Junior, Helio A. [Clinicas Oncologicas Integradas (COI), Rio de Janeiro, RJ (Brazil)

    2011-07-01

    This work aims to present a computational process of conversion of tomographic and MRI medical images from patients in voxel structures to an input file, which will be manipulated in Monte Carlo Simulation code for tumor's radiotherapic treatments. The problem's scenario inherent to the patient is simulated by such process, using the volume element (voxel) as a unit of computational tracing. The head's voxel structure geometry has voxels with volumetric dimensions around 1 mm{sup 3} and a population of millions, which helps - in that way, for a realistic simulation and a decrease in image's digital process techniques for adjustments and equalizations. With such additional data from the code, a more critical analysis can be developed in order to determine the volume of the tumor, and the protection, beside the patients' medical images were borrowed by Clinicas Oncologicas Integradas (COI/RJ), joined to the previous performed planning. In order to execute this computational process, SAPDI computational system is used in a digital image process for optimization of data, conversion program Scan2MCNP, which manipulates, processes, and converts the medical images into voxel structures to input files and the graphic visualizer Moritz for the verification of image's geometry placing. (author)

  17. Influence of voxel size settings in X-Ray CT Imagery of soil in scaling properties

    Science.gov (United States)

    Heck, R.; Scaiff, N. T.; Andina, D.; Tarquis, A. M.

    2012-04-01

    Fundamental to the interpretation and comparison of X-ray CT imagery of soil is recognition of the objectivity and consistency of procedures used to generate the 3D models. Notably, there has been a lack of consistency in the size of voxels used for diverse interpretations of soils features and processes; in part, this is due to the ongoing evolution of instrumentation and computerized image processing capacity. Moreover, there is still need for discussion on whether standard voxels sizes should be recommended, and what those would be. Regardless of any eventual adoption of such standards, there is a need to also consider the manner in which voxel size is set in the 3D imagery. In the typical approaches to X-ray CT imaging, voxel size may be set at three stages: image acquisition (involving the position of the sample relative to the tube and detector), image reconstruction (where binning of pixels in the acquired images may occur), as well as post-reconstruction re-sampling (which may involve algorithms such as tri-cubic convolution). This research evaluates and compares the spatial distribution of intra-aggregate voids in 3D imagery as well as their scaling properties, of equivalent voxel size, generated using various combinations of the afore-mentioned approaches. Funding provided by Spanish Ministerio de Ciencia e Innovación (MICINN) through project no. AGL2010-21501/AGR is greatly appreciated.

  18. A visual LISP program for voxelizing AutoCAD solid models

    Science.gov (United States)

    Marschallinger, Robert; Jandrisevits, Carmen; Zobl, Fritz

    2015-01-01

    AutoCAD solid models are increasingly recognized in geological and geotechnical 3D modeling. In order to bridge the currently existing gap between AutoCAD solid models and the grid modeling realm, a Visual LISP program is presented that converts AutoCAD solid models into voxel arrays. Acad2Vox voxelizer works on a 3D-model that is made up of arbitrary non-overlapping 3D-solids. After definition of the target voxel array geometry, 3D-solids are scanned at grid positions and properties are streamed to an ASCII output file. Acad2Vox has a novel voxelization strategy that combines a hierarchical reduction of sampling dimensionality with an innovative use of AutoCAD-specific methods for a fast and memory-saving operation. Acad2Vox provides georeferenced, voxelized analogs of 3D design data that can act as regions-of-interest in later geostatistical modeling and simulation. The Supplement includes sample geological solid models with instructions for practical work with Acad2Vox.

  19. Voxel Based Morphometry Alterations in Mal de Debarquement Syndrome.

    Directory of Open Access Journals (Sweden)

    Yoon-Hee Cha

    Full Text Available Mal de debarquement syndrome (MdDS is a disorder of chronic self-motion perception that occurs though entrainment to rhythmic background motion, such as from sea voyage, and involves the perception of low-frequency rocking that can last for months or years. The neural basis of this persistent sensory perception abnormality is not well understood.We investigated grey matter volume differences underlying persistent MdDS by performing voxel-based morphometry on whole brain and pre-specified ROIs in 28 individuals with MdDS and comparing them to 18 age, sex, and handedness matched controls.MdDS participants exhibited greater grey matter volume in the left inferior parietal lobule, right inferior occipital gyrus (area V3v, right temporal pole, bilateral cerebellar hemispheric lobules VIII/IX and left lobule VIIa/VIIb. Grey matter volumes were lower in bilateral inferior frontal, orbitofrontal, pregenual anterior cingulate cortex (pgACC and left superior medial gyri (t = 3.0, p<0.005uncorr. In ROI analyses, there were no volume differences in the middle occipital gyrus (region of V5/MT or parietal operculum 2 (region of the parietoinsular vestibular cortex. Illness duration was positively related to grey matter volume in bilateral inferior frontal gyrus/anterior insula (IFG/AI, right posterior insula, superior parietal lobule, left middle occipital gyrus (V5/MT, bilateral postcentral gyrus, anterior cerebellum, and left cerebellar hemisphere and vermian lobule IX. In contrast, illness duration was negatively related to volume in pgACC, posterior middle cingulate gyrus (MCC, left middle frontal gyrus (dorsolateral prefrontal cortex-DLPFC, and right cerebellar hemispheric lobule VIIIb (t = 3.0, p<0.005uncorr. The most significant differences were decreased volume in the pgACC and increased volume in the left IFG/AI with longer illness duration (qFDRcorr <0.05. Concurrent medication use did not correlate with these findings or have a relationship with

  20. The Science of Calibration

    Science.gov (United States)

    Kent, S. M.

    2016-05-01

    This paper presents a broad overview of the many issues involved in calibrating astronomical data, covering the full electromagnetic spectrum from radio waves to gamma rays, and considering both ground-based and space-based missions. These issues include the science drivers for absolute and relative calibration, the physics behind calibration and the mechanisms used to transfer it from the laboratory to an astronomical source, the need for networks of calibrated astronomical standards, and some of the challenges faced by large surveys and missions.

  1. A Multi-Criteria Framework with Voxel-Dependent Parameters for Radiotherapy Treatment Plan Optimization

    CERN Document Server

    Zarepisheh, Masoud; Li, Nan; Jia, Xun; Jiang, Steve B

    2012-01-01

    In a treatment plan optimization problem for radiotherapy, a clinically acceptable plan is usually generated by an optimization process with weighting factors or reference doses adjusted for organs. Recent discoveries indicate that adjusting parameters associated with each voxel may lead to better plan quality. However, it is still unclear regarding the mathematical reasons behind it. To answer questions related to this problem, we establish in this work a new mathematical framework equipped with two theorems. The new framework clarifies the different consequences of adjusting organ-dependent and voxel-dependent parameters for the treatment plan optimization of radiation therapy, as well as the different effects of adjusting weighting factors versus reference doses in the optimization process. The main discoveries are threefold: 1) While in the organ-based model the selection of the objective function has an impact on the quality of the optimized plans, this is no longer an issue for the voxel-based model sin...

  2. Optimization of Voxelization Parameters in Geant4 Tracking and Improvement of the Shooter Benchmarking Program

    CERN Document Server

    Siegel, Zachary

    2013-01-01

    The geometry-based tracking of the ubiquitous particle physics simulation toolkit Geant4 utilizes the idea of voxels, which effectively partition regions into multi-dimensional slices that can decrease simulation time. The extent of voxelization and the size of the voxels is determined by a set of parameters, which until now, defaulted to arbitrary numbers. In this report I document how I tested different values for these parameters and determined which values should be the default. I modified the existing G01 Geant4 example program to get an initial look at how the performance depended on the parameters. Then I modified the Shooter benchmark program, which lacks extraneous physics processes, to collect more refined data and to provide a tool for future testers to perform comprehensive benchmarks. To this end, I created a new geometry, added features to aid in testing over ranges of parameters, and setup the default tests to provide a good sampling of different simulation scenarios.

  3. 可视人真实可视化的突出进展Voxel-Man(4)%Outstanding Trend of Voxel-Man(4)

    Institute of Scientific and Technical Information of China (English)

    秦笃烈

    2005-01-01

    @@ 3.6 Voxel-Man用于古人类生物学研究 人类生物学研究是另一个方面的应用. 分析和研究人类化石的颅内特征是研究人类进化过程的新领域.利用Voxel-Man处理化石的CT数据集,可以在消除沉积的情况下生成颅骨的完整3D重构,如图72所示.所用的人类颅骨化石取自肯尼亚和坦桑尼亚.这是IDM开辟的医学图像处理的一个新的领域.

  4. New hybrid voxelized/analytical primitive in Monte Carlo simulations for medical applications.

    Science.gov (United States)

    Bert, Julien; Lemaréchal, Yannick; Visvikis, Dimitris

    2016-05-01

    Monte Carlo simulations (MCS) applied in particle physics play a key role in medical imaging and particle therapy. In such simulations, particles are transported through voxelized phantoms derived from predominantly patient CT images. However, such voxelized object representation limits the incorporation of fine elements, such as artificial implants from CAD modeling or anatomical and functional details extracted from other imaging modalities. In this work we propose a new hYbrid Voxelized/ANalytical primitive (YVAN) that combines both voxelized and analytical object descriptions within the same MCS, without the need to simultaneously run two parallel simulations, which is the current gold standard methodology. Given that YVAN is simply a new primitive object, it does not require any modifications on the underlying MC navigation code. The new proposed primitive was assessed through a first simple MCS. Results from the YVAN primitive were compared against an MCS using a pure analytical geometry and the layer mass geometry concept. A perfect agreement was found between these simulations, leading to the conclusion that the new hybrid primitive is able to accurately and efficiently handle phantoms defined by a mixture of voxelized and analytical objects. In addition, two application-based evaluation studies in coronary angiography and intra-operative radiotherapy showed that the use of YVAN was 6.5% and 12.2% faster than the layered mass geometry method, respectively, without any associated loss of accuracy. However, the simplification advantages and differences in computational time improvements obtained with YVAN depend on the relative proportion of the analytical and voxelized structures used in the simulation as well as the size and number of triangles used in the description of the analytical object meshes.

  5. Voxel size dependency, reproducibility and sensitivity of an in vivo bone loading estimation algorithm.

    Science.gov (United States)

    Christen, Patrik; Schulte, Friederike A; Zwahlen, Alexander; van Rietbergen, Bert; Boutroy, Stephanie; Melton, L Joseph; Amin, Shreyasee; Khosla, Sundeep; Goldhahn, Jörg; Müller, Ralph

    2016-01-01

    A bone loading estimation algorithm was previously developed that provides in vivo loading conditions required for in vivo bone remodelling simulations. The algorithm derives a bone's loading history from its microstructure as assessed by high-resolution (HR) computed tomography (CT). This reverse engineering approach showed accurate and realistic results based on micro-CT and HR-peripheral quantitative CT images. However, its voxel size dependency, reproducibility and sensitivity still need to be investigated, which is the purpose of this study. Voxel size dependency was tested on cadaveric distal radii with micro-CT images scanned at 25 µm and downscaled to 50, 61, 75, 82, 100, 125 and 150 µm. Reproducibility was calculated with repeated in vitro as well as in vivo HR-pQCT measurements at 82 µm. Sensitivity was defined using HR-pQCT images from women with fracture versus non-fracture, and low versus high bone volume fraction, expecting similar and different loading histories, respectively. Our results indicate that the algorithm is voxel size independent within an average (maximum) error of 8.2% (32.9%) at 61 µm, but that the dependency increases considerably at voxel sizes bigger than 82 µm. In vitro and in vivo reproducibility are up to 4.5% and 10.2%, respectively, which is comparable to other in vitro studies and slightly higher than in other in vivo studies. Subjects with different bone volume fraction were clearly distinguished but not subjects with and without fracture. This is in agreement with bone adapting to customary loading but not to fall loads. We conclude that the in vivo bone loading estimation algorithm provides reproducible, sensitive and fairly voxel size independent results at up to 82 µm, but that smaller voxel sizes would be advantageous.

  6. New hybrid voxelized/analytical primitive in Monte Carlo simulations for medical applications

    Science.gov (United States)

    Bert, Julien; Lemaréchal, Yannick; Visvikis, Dimitris

    2016-05-01

    Monte Carlo simulations (MCS) applied in particle physics play a key role in medical imaging and particle therapy. In such simulations, particles are transported through voxelized phantoms derived from predominantly patient CT images. However, such voxelized object representation limits the incorporation of fine elements, such as artificial implants from CAD modeling or anatomical and functional details extracted from other imaging modalities. In this work we propose a new hYbrid Voxelized/ANalytical primitive (YVAN) that combines both voxelized and analytical object descriptions within the same MCS, without the need to simultaneously run two parallel simulations, which is the current gold standard methodology. Given that YVAN is simply a new primitive object, it does not require any modifications on the underlying MC navigation code. The new proposed primitive was assessed through a first simple MCS. Results from the YVAN primitive were compared against an MCS using a pure analytical geometry and the layer mass geometry concept. A perfect agreement was found between these simulations, leading to the conclusion that the new hybrid primitive is able to accurately and efficiently handle phantoms defined by a mixture of voxelized and analytical objects. In addition, two application-based evaluation studies in coronary angiography and intra-operative radiotherapy showed that the use of YVAN was 6.5% and 12.2% faster than the layered mass geometry method, respectively, without any associated loss of accuracy. However, the simplification advantages and differences in computational time improvements obtained with YVAN depend on the relative proportion of the analytical and voxelized structures used in the simulation as well as the size and number of triangles used in the description of the analytical object meshes.

  7. OLI Radiometric Calibration

    Science.gov (United States)

    Markham, Brian; Morfitt, Ron; Kvaran, Geir; Biggar, Stuart; Leisso, Nathan; Czapla-Myers, Jeff

    2011-01-01

    Goals: (1) Present an overview of the pre-launch radiance, reflectance & uniformity calibration of the Operational Land Imager (OLI) (1a) Transfer to orbit/heliostat (1b) Linearity (2) Discuss on-orbit plans for radiance, reflectance and uniformity calibration of the OLI

  8. Lidar to lidar calibration

    DEFF Research Database (Denmark)

    Fernandez Garcia, Sergio; Villanueva, Héctor

    This report presents the result of the lidar to lidar calibration performed for ground-based lidar. Calibration is here understood as the establishment of a relation between the reference lidar wind speed measurements with measurement uncertainties provided by measurement standard and correspondi...

  9. Characterization of tumor dose heterogeneity for 90Y microsphere therapies using voxel- based dosimetry

    Directory of Open Access Journals (Sweden)

    Justin Mikell

    2014-03-01

    Full Text Available Purpose: Dosimetry for 90Y microsphere therapies (YMT with Standard (SM and Partition (PM models provide only uniform dose estimates to tumor and liver. Our objective is to calculate tumor dose heterogeneity, known to effect response, using voxel-based dosimetry and investigate the limitations of SM and PM.Methods: Voxel-based dosimetry was performed on 17 YMT patients using Monte Carlo DOSXYZnrc. 90Y activity and tissue/density distributions were based on quantitative 90Y bremsstrahlung SPECT/CT. Tumors (n=31, liver, and treatment lobe/segments were segmented on diagnostic CT or MR. Dose volume histograms (DVH were created for tumors and normal liver. Bland-Altman analysis compared voxel-based mean absorbed doses to tumor and liver with SM and PM. Tumor and normal liver absorbed dose heterogeneity were investigated through metrics: integral uniformity (IU, D10/D90, COV. Correlations of heterogeneity with voxel-based mean doses and volumes were evaluated.Results: Heterogeneity metrics (mean ± 1σ for tumor dose were COV = 0.48 ± 0.28, D10/D90 = 4.7 ± 3.9, and IU = 0.8 ± 0.18. Heterogeneity metrics correlated with tumor volume (r > 0.58 but not tumor mean doses (r < 0.20. Voxel-based tumor mean doses correlated with PM (r = 0.84 but not SM (r = 0.08. Both yielded poor limits of agreement with of 83 ± 174 and -28 ± 181 Gy, respectively. Normal liver heterogeneity metrics (mean ± 1σ were COV = 0.83 ± 0.29, D10/D90 = 12 ± 15, and IU = 0.97 ± 0.03. Only D10/D90 (r = 0.49 correlated with mean normal liver absorbed dose. Voxel-based normal liver/lobe mean doses correlated with PM (r = 0.96, but had poor limits of agreement (26 ± 29 Gy.Conclusion: Tumor doses have high levels of heterogeneity that increase with volume but are independent of dose. Voxel-based DVH and dose heterogeneity metrics will promote accurate characterization of tumor response following YMT.--------------------------------------Cite this article as: Mikell J, Mourtada F

  10. The Relevance Voxel Machine (RVoxM): A Bayesian Method for Image-Based Prediction

    DEFF Research Database (Denmark)

    Sabuncu, Mert R.; Van Leemput, Koen

    2011-01-01

    to utilize a small number of spatially clustered sets of voxels that are particularly suited for clinical interpretation. RVoxM automatically tunes all its free parameters during the training phase, and offers the additional advantage of producing probabilistic prediction outcomes. Experiments on age......This paper presents the Relevance VoxelMachine (RVoxM), a Bayesian multivariate pattern analysis (MVPA) algorithm that is specifically designed for making predictions based on image data. In contrast to generic MVPA algorithms that have often been used for this purpose, the method is designed...... prediction from structural brain MRI indicate that RVoxM yields biologically meaningful models that provide excellent predictive accuracy....

  11. Neuroanatomical phenotype of Klinefelter syndrome in childhood: a voxel-based morphometry study.

    Science.gov (United States)

    Bryant, Daniel M; Hoeft, Fumiko; Lai, Song; Lackey, John; Roeltgen, David; Ross, Judith; Reiss, Allan L

    2011-05-04

    Klinefelter syndrome (KS) is a genetic disorder characterized by a supernumerary X chromosome. As such, KS offers a naturally occurring human model for the study of both X-chromosome gene expression and androgen on brain development. Previous neuroimaging studies have revealed neuroanatomical variations associated with KS, but have differed widely with respect to subject inclusion criteria, including mosaicism, pubertal status, and history of testosterone replacement therapy (TRT), all factors likely to influence neurodevelopment. We conducted a voxel-based morphometry study of regional gray and white matter (GM and WM, respectively) volumes in 31 KS males (mean age, 9.69 ± 1.70 years) and 36 typically developing (TD) male controls (10.99 ± 1.72 years). None of the participants with KS had received TRT, and all were prepubertal and had nonmosaic 47,XXY karyotypes. After controlling for age, males with KS showed trends (0.05 < p < 0.10) for significantly reduced total gray matter volume (TGMV) and total white matter volume (TWMV), relative to TD males. After controlling for TGMV and age, the KS group had significantly increased sensorimotor and parietal-occipital GM and significantly reduced amygdalar, hippocampal, insular, temporal, and inferior frontal GM relative to TD controls. After controlling for TWMV and age, the KS group had significantly increased left parietal WM as well as significantly reduced frontal and temporal WM. These findings are indicative of a characteristic prepubertal neuroanatomical phenotype that may be associated with cognitive-behavioral features of KS. This work offers new insight into the relationships among X-chromosome gene expression, neuroanatomy, and cognitive-behavioral functions impaired in KS, including language and attention.

  12. Neuroanatomical abnormalities before onset of delusions in patients with Alzheimer’s disease: a voxel-based morphometry study

    Directory of Open Access Journals (Sweden)

    Nakaaki S

    2012-12-01

    Full Text Available Shutaro Nakaaki,1 Junko Sato,2 Katsuyoshi Torii,2 Mizuki Oka,1 Atsushi Negi,2 Takashi Nakamae,3 Jin Narumoto,3 Jun Miyata,4 Toshi A Furukawa,5 Masaru Mimura11Department of Neuropsychiatry, Keio University School of Medicine, Shinjuku-ku, Tokyo, 2Department of Psychiatry and Cognitive-Behavioral Medicine, Nagoya City University Graduate School of Medical Sciences, Nagoya, 3Department of Psychiatry, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, 4Department of Neuropsychiatry, Graduate School of Medicine, Kyoto University, Kyoto, 5Department of Health Promotion and Human Behavior (Cognitive-Behavioral Medicine, Kyoto University Graduate School of Medicine and Public Health, Kyoto, JapanBackground: Structural brain abnormalities associated with delusions in Alzheimer’s disease are poorly understood. In addition, whether the neural substrate underlying the delusions develops before the onset of the delusions is unclear. In this study, we used a voxel-based morphometry approach to examine the existence of regional structural abnormalities at baseline in patients with Alzheimer’s disease who did and who did not develop delusions.Methods: Using the Neuropsychiatric Inventory, we identified patients with Alzheimer’s disease who exhibited delusions during a 2-year period. All the patients had undergone a magnetic resonance imaging examination at the start of the study period (baseline. We conducted a voxel-based morphometry analysis using statistical parametric mapping (SPM5 software and compared the results of patients with Alzheimer’s disease who did and did not develop delusions.Results: Compared with the patients who did not develop delusions (n = 35, the patients who did develop delusions (n = 18 had significantly smaller gray matter volumes on both sides of the parahippocampal gyrus, the right posterior cingulate gyrus, the right orbitofrontal cortex, both sides of the inferior frontal cortex, the right

  13. Sandia WIPP calibration traceability

    Energy Technology Data Exchange (ETDEWEB)

    Schuhen, M.D. [Sandia National Labs., Albuquerque, NM (United States); Dean, T.A. [RE/SPEC, Inc., Albuquerque, NM (United States)

    1996-05-01

    This report summarizes the work performed to establish calibration traceability for the instrumentation used by Sandia National Laboratories at the Waste Isolation Pilot Plant (WIPP) during testing from 1980-1985. Identifying the calibration traceability is an important part of establishing a pedigree for the data and is part of the qualification of existing data. In general, the requirement states that the calibration of Measuring and Test equipment must have a valid relationship to nationally recognized standards or the basis for the calibration must be documented. Sandia recognized that just establishing calibration traceability would not necessarily mean that all QA requirements were met during the certification of test instrumentation. To address this concern, the assessment was expanded to include various activities.

  14. WFPC2 Polarization Calibration

    Science.gov (United States)

    Biretta, J.; McMaster, M.

    1997-12-01

    We derive a detailed calibration for WFPC2 polarization data which is accurate to about 1.5%. We begin by computing polarizer flats, and show how they are applied to data. A physical model for the polarization effects of the WFPC2 optics is then created using Mueller matricies. This model includes corrections for the instrumental polarization (diattenuation and phase retardance) of the pick-off mirror, as well as the high cross-polarization transmission of the polarizer filter. We compare this model against the on-orbit observations of polarization calibrators, and show it predicts relative counts in the different polarizer/aperture settings to 1.5% RMS accuracy. We then show how this model can be used to calibrate GO data, and present two WWW tools which allow observers to easily calibrate their data. Detailed examples are given illustrationg the calibration and display of WFPC2 polarization data. In closing we describe future plans and possible improvements.

  15. Cobalt source calibration

    Energy Technology Data Exchange (ETDEWEB)

    Rizvi, H.M.

    1999-12-03

    The data obtained from these tests determine the dose rate of the two cobalt sources in SRTC. Building 774-A houses one of these sources while the other resides in room C-067 of Building 773-A. The data from this experiment shows the following: (1) The dose rate of the No.2 cobalt source in Building 774-A measured 1.073 x 10{sup 5} rad/h (June 17, 1999). The dose rate of the Shepherd Model 109 Gamma cobalt source in Building 773-A measured 9.27 x 10{sup 5} rad/h (June 25, 1999). These rates come from placing the graduated cylinder containing the dosimeter solution in the center of the irradiation chamber. (2) Two calibration tests in the 774-A source placed the graduated cylinder with the dosimeter solution approximately 1.5 inches off center in the axial direction. This movement of the sample reduced the measured dose rate 0.92% from 1.083 x 10{sup 5} rad/h to 1.073 x 10{sup 5} rad/h. and (3) A similar test in the cobalt source in 773-A placed the graduated cylinder approximately 2.0 inches off center in the axial direction. This change in position reduced the measured dose rate by 10.34% from 1.036 x 10{sup 6} to 9.27 x 10{sup 5}. This testing used chemical dosimetry to measure the dose rate of a radioactive source. In this method, one determines the dose by the chemical change that takes place in the dosimeter. For this calibration experiment, the author used a Fricke (ferrous ammonium sulfate) dosimeter. This solution works well for dose rates to 10{sup 7} rad/h. During irradiation of the Fricke dosimeter solution the Fe{sup 2+} ions ionize to Fe{sup 3+}. When this occurs, the solution acquires a slightly darker tint (not visible to the human eye). To determine the magnitude of the change in Fe ions, one places the solution in an UV-VIS Spectrophotometer. The UV-VIS Spectrophotometer measures the absorbency of the solution. Dividing the absorbency by the total time (in minutes) of exposure yields the dose rate.

  16. A radioactive seed implant on a rabbit's liver following a voxel model representation for dosimetric proposals

    Energy Technology Data Exchange (ETDEWEB)

    Campos, Tarcisio P.R.; Andrade, Joao Paulo Lopes de; Costa, Igor Temponi; Teixeira, Cleuza H. [Minas Gerais Univ., Belo Horizonte, MG (Brazil). Programa de Pos-graduacao em Ciencias e Tecnicas Nucleares]. E-mail: campos@nuclear.ufmg

    2005-07-01

    Animal models have been used in experimentation with ionizing radiation. The evaluation of the energy absorbed per unit tissue mass in vivo transported by nuclear particles is a task to be performed before experimentation. Stochastic or deterministic methodology can be applied, however the dosimetric protocols applied in radiotherapy center cannot be applied directly due to the inherent small geometry and chemical composition of the animal distinct from human. The present article addresses a method in development that will predict the dose distribution into the rabbit thorax based on the solution of the transport phenomena in a voxel model. The model will be applied to simulate a seed implant experiment on a rabbit. Herein, the construction of the three-dimensional voxel model anthropomorphic -anthropometrics to the rabbit is presented. The model is assembling from a set of computer tomography of the rabbit. The computational phantom of the thorax starts at the digitalisation of the CT images, tissue definition, and color image representation of each tissue and organ. The chemical composition and mass density of each tissue is evaluated as similar date presented by ICRU-44. To treat the images, a code namely SISCODES, developed in house, was used. The in vivo experiment that will be simulated is also described. That is a implant of five seeds of 1.6x2 mm performed in a rabbit's liver. The perspective of this work is the application of the model in dosimetric studies predicting the dose distribution around the seed's implanted in vivo experiments. (author)

  17. Segment Based Camera Calibration

    Institute of Scientific and Technical Information of China (English)

    马颂德; 魏国庆; 等

    1993-01-01

    The basic idea of calibrating a camera system in previous approaches is to determine camera parmeters by using a set of known 3D points as calibration reference.In this paper,we present a method of camera calibration in whih camera parameters are determined by a set of 3D lines.A set of constraints is derived on camea parameters in terms of perspective line mapping.Form these constraints,the same perspective transformation matrix as that for point mapping can be computed linearly.The minimum number of calibration lines is 6.This result generalizes that of Liu,Huang and Faugeras[12] for camera location determination in which at least 8 line correspondences are required for linear computation of camera location.Since line segments in an image can be located easily and more accurately than points,the use of lines as calibration reference tends to ease the computation in inage preprocessing and to improve calibration accuracy.Experimental results on the calibration along with stereo reconstruction are reported.

  18. Lidar to lidar calibration

    DEFF Research Database (Denmark)

    Georgieva Yankova, Ginka; Courtney, Michael

    This report presents the result of the lidar to lidar calibration performed for ground-based lidar. Calibration is here understood as the establishment of a relation between the reference lidar wind speed measurements with measurement uncertainties provided by measurement standard and corresponding...... lidar wind speed indications with associated measurement uncertainties. The lidar calibration concerns the 10 minute mean wind speed measurements. The comparison of the lidar measurements of the wind direction with that from the reference lidar measurements are given for information only....

  19. Site Calibration report

    DEFF Research Database (Denmark)

    Gómez Arranz, Paula; Vesth, Allan

    This report describes the site calibration carried out at Østerild, during a given period. The site calibration was performed with two Windcube WLS7 (v1) lidars at ten measurements heights. The lidar is not a sensor approved by the current version of the IEC 61400-12-1 [1] and therefore the site...... calibration with lidars does not comply with the standard. However, the measurements are carried out following the guidelines of IEC 61400-12-1 where possible, but with some deviations presented in the following chapters....

  20. Calibration Fixture For Anemometer Probes

    Science.gov (United States)

    Lewis, Charles R.; Nagel, Robert T.

    1993-01-01

    Fixture facilitates calibration of three-dimensional sideflow thermal anemometer probes. With fixture, probe oriented at number of angles throughout its design range. Readings calibrated as function of orientation in airflow. Calibration repeatable and verifiable.

  1. A generalization of voxel-wise procedures for highdimensional statistical inference using ridge regression

    DEFF Research Database (Denmark)

    Sjöstrand, Karl; Cardenas, Valerie A.; Larsen, Rasmus;

    2008-01-01

    regression to address this issue, allowing for a gradual introduction of correlation information into the model. We make the connections between ridge regression and voxel-wise procedures explicit and discuss relations to other statistical methods. Results are given on an in-vivo data set of deformation...

  2. List-mode image reconstruction for positron emission tomography using tetrahedral voxels

    Science.gov (United States)

    Gillam, John E.; Angelis, Georgios I.; Meikle, Steven R.

    2016-09-01

    Image space decomposition based on tetrahedral voxels are interesting candidates for use in emission tomography. Tetrahedral voxels provide many of the advantages of point clouds with irregular spacing, such as being intrinsically multi-resolution, yet they also serve as a volumetric partition of the image space and so are comparable to more standard cubic voxels. Additionally, non-rigid displacement fields can be applied to the tetrahedral mesh in a straight-forward manner. So far studies incorporating tetrahedral decomposition of the image space have concentrated on pre-calculated, node-based, system matrix elements which reduces the flexibility of the tetrahedral approach and the capacity to accurately define regions of interest. Here, a list-mode on-the-fly calculation of the system matrix elements is described using a tetrahedral decomposition of the image space and volumetric elements—voxels. The algorithm is demonstrated in the context of awake animal PET which may require both rigid and non-rigid motion compensation, as well as quantification within small regions of the brain. This approach allows accurate, event based, motion compensation including non-rigid deformations.

  3. Advances in constructing regional geological voxel models, illustrated by their application in aggregate resource assessments

    NARCIS (Netherlands)

    Maljers, D.; Stafleu, J.; Meulen, M.J. van der; Dambrink, R.M.

    2015-01-01

    Aggregate resource assessments, derived from three subsequent generations of voxel models, were compared in a qualitative way to illustrate and discuss modelling progress. We compared the models in terms of both methodology and usability. All three models were produced by the Geological Survey of th

  4. Select and Cluster: A Method for Finding Functional Networks of Clustered Voxels in fMRI

    Science.gov (United States)

    DonGiovanni, Danilo

    2016-01-01

    Extracting functional connectivity patterns among cortical regions in fMRI datasets is a challenge stimulating the development of effective data-driven or model based techniques. Here, we present a novel data-driven method for the extraction of significantly connected functional ROIs directly from the preprocessed fMRI data without relying on a priori knowledge of the expected activations. This method finds spatially compact groups of voxels which show a homogeneous pattern of significant connectivity with other regions in the brain. The method, called Select and Cluster (S&C), consists of two steps: first, a dimensionality reduction step based on a blind multiresolution pairwise correlation by which the subset of all cortical voxels with significant mutual correlation is selected and the second step in which the selected voxels are grouped into spatially compact and functionally homogeneous ROIs by means of a Support Vector Clustering (SVC) algorithm. The S&C method is described in detail. Its performance assessed on simulated and experimental fMRI data is compared to other methods commonly used in functional connectivity analyses, such as Independent Component Analysis (ICA) or clustering. S&C method simplifies the extraction of functional networks in fMRI by identifying automatically spatially compact groups of voxels (ROIs) involved in whole brain scale activation networks. PMID:27656202

  5. Anatomical specificity of vascular endothelial growth factor expression in glioblastomas: a voxel-based mapping analysis

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Xing [Capital Medical University, Department of Neurosurgery, Beijing Tiantan Hospital, Beijing (China); Wang, Yinyan [Capital Medical University, Department of Neurosurgery, Beijing Tiantan Hospital, Beijing (China); Capital Medical University, Department of Neuropathology, Beijing Neurosurgical Institute, Beijing (China); Wang, Kai; Ma, Jun; Li, Shaowu [Capital Medical University, Department of Neuroradiology, Beijing Tiantan Hospital, Beijing (China); Liu, Shuai [Chinese Academy of Medical Sciences and Peking Union Medical College, Departments of Neurosurgery, Peking Union Medical College Hospital, Beijing (China); Liu, Yong [Chinese Academy of Sciences, Brainnetome Center, Institute of Automation, Beijing (China); Jiang, Tao [Capital Medical University, Department of Neurosurgery, Beijing Tiantan Hospital, Beijing (China); Beijing Academy of Critical Illness in Brain, Department of Clinical Oncology, Beijing (China)

    2016-01-15

    The expression of vascular endothelial growth factor (VEGF) is a common genetic alteration in malignant gliomas and contributes to the angiogenesis of tumors. This study aimed to investigate the anatomical specificity of VEGF expression levels in glioblastomas using voxel-based neuroimaging analysis. Clinical information, MR scans, and immunohistochemistry stains of 209 patients with glioblastomas were reviewed. All tumor lesions were segmented manually and subsequently registered to standard brain space. Voxel-based regression analysis was performed to correlate the brain regions of tumor involvement with the level of VEGF expression. Brain regions identified as significantly associated with high or low VEGF expression were preserved following permutation correction. High VEGF expression was detected in 123 (58.9 %) of the 209 patients. Voxel-based statistical analysis demonstrated that high VEGF expression was more likely in tumors located in the left frontal lobe and the right caudate and low VEGF expression was more likely in tumors that occurred in the posterior region of the right lateral ventricle. Voxel-based neuroimaging analysis revealed the anatomic specificity of VEGF expression in glioblastoma, which may further our understanding of genetic heterogeneity during tumor origination. This finding provides primary theoretical support for potential future application of customized antiangiogenic therapy. (orig.)

  6. Evaluation of voxel-based rendering of high resolution surface descriptions

    DEFF Research Database (Denmark)

    Hammershøi, Dorte; Olesen, Søren Krarup; Markovic, Milos

    2014-01-01

    resolution scans of the room surfaces as basis for the room models. In the present work this approach is evaluated with a voxel-based method (described in earlier publications), and compared to measured impulse responses. The results are compared objectively by visual inspection of the impulse responses...

  7. Two-tensor streamline tractography through white matter intra-voxel fiber crossings

    DEFF Research Database (Denmark)

    Qazi, Arish Asif; Kindlmann, G; O'Donnell, L;

    2008-01-01

    An inherent drawback of the traditional diffusion tensor model is its limited ability to provide detailed information about multidirectional fiber architecture within a voxel. This leads to erroneous fiber tractography results in locations where fiber bundles cross each other. In this paper, we...

  8. Physically constrained voxel-based penalty adaptation for ultra-fast IMRT planning.

    Science.gov (United States)

    Wahl, Niklas; Bangert, Mark; Kamerling, Cornelis P; Ziegenhein, Peter; Bol, Gijsbert H; Raaymakers, Bas W; Oelfke, Uwe

    2016-07-08

    Conventional treatment planning in intensity-modulated radiation therapy (IMRT) is a trial-and-error process that usually involves tedious tweaking of optimization parameters. Here, we present an algorithm that automates part of this process, in particular the adaptation of voxel-based penalties within normal tissue. Thereby, the proposed algorithm explicitly considers a priori known physical limitations of photon irradiation. The efficacy of the developed algorithm is assessed during treatment planning studies comprising 16 prostate and 5 head and neck cases. We study the eradication of hot spots in the normal tissue, effects on target coverage and target conformity, as well as selected dose volume points for organs at risk. The potential of the proposed method to generate class solutions for the two indications is investigated. Run-times of the algorithms are reported. Physically constrained voxel-based penalty adaptation is an adequate means to automatically detect and eradicate hot-spots during IMRT planning while maintaining target coverage and conformity. Negative effects on organs at risk are comparably small and restricted to lower doses. Using physically constrained voxel-based penalty adaptation, it was possible to improve the generation of class solutions for both indications. Considering the reported run-times of less than 20 s, physically constrained voxel-based penalty adaptation has the potential to reduce the clinical workload during planning and automated treatment plan generation in the long run, facilitating adaptive radiation treatments.

  9. Neural Correlates of Communication Skill and Symptom Severity in Autism: A Voxel-Based Morphometry Study

    Science.gov (United States)

    Parks, Lauren K.; Hill, Dina E.; Thoma, Robert J.; Euler, Matthew J.; Lewine, Jeffrey D.; Yeo, Ronald A.

    2009-01-01

    Although many studies have compared the brains of normal controls and individuals with autism, especially older, higher-functioning individuals with autism, little is known of the neural correlates of the vast clinical heterogeneity characteristic of the disorder. In this study, we used voxel-based morphometry (VBM) to examine gray matter…

  10. Part-type Segmentation of Articulated Voxel-Shapes using the Junction Rule

    NARCIS (Netherlands)

    Reniers, Dennie; Telea, Alexandru

    2008-01-01

    We present a part-type segmentation method for articulated voxel-shapes based on curve skeletons. Shapes are considered to consist of several simpler, intersecting shapes. Our method is based on the junction rule : the observation that two intersecting shapes generate an additional junction in their

  11. Patch-type Segmentation of Voxel Shapes using Simplified Surface Skeletons

    NARCIS (Netherlands)

    Reniers, Dennie; Telea, Alexandru

    2008-01-01

    We present a new method for decomposing a 3D voxel shape into disjoint segments using the shape’s simplified surface-skeleton. The surface skeleton of a shape consists of 2D manifolds inside its volume. Each skeleton point has a maximally inscribed ball that touches the boundary in at least two cont

  12. Part-type Segmentation of Articulated Voxel-Shapes using the Junction Rule

    NARCIS (Netherlands)

    Reniers, Dennie; Telea, Alexandru

    2008-01-01

    We present a part-type segmentation method for articulated voxel-shapes based on curve skeletons. Shapes are considered to consist of several simpler, intersecting shapes. Our method is based on the junction rule: the observation that two intersecting shapes generate an additional junction in their

  13. SPOTS Calibration Example

    Directory of Open Access Journals (Sweden)

    Patterson E.

    2010-06-01

    Full Text Available The results are presented using the procedure outlined by the Standardisation Project for Optical Techniques of Strain measurement to calibrate a digital image correlation system. The process involves comparing the experimental data obtained with the optical measurement system to the theoretical values for a specially designed specimen. The standard states the criteria which must be met in order to achieve successful calibration, in addition to quantifying the measurement uncertainty in the system. The system was evaluated at three different displacement load levels, generating strain ranges from 289 µstrain to 2110 µstrain. At the 289 µstrain range, the calibration uncertainty was found to be 14.1 µstrain, and at the 2110 µstrain range it was found to be 28.9 µstrain. This calibration procedure was performed without painting a speckle pattern on the surface of the metal. Instead, the specimen surface was prepared using different grades of grit paper to produce the desired texture.

  14. Air Data Calibration Facility

    Data.gov (United States)

    Federal Laboratory Consortium — This facility is for low altitude subsonic altimeter system calibrations of air vehicles. Mission is a direct support of the AFFTC mission. Postflight data merge is...

  15. Traceable Pyrgeometer Calibrations

    Energy Technology Data Exchange (ETDEWEB)

    Dooraghi, Mike; Kutchenreiter, Mark; Reda, Ibrahim; Habte, Aron; Sengupta, Manajit; Andreas, Afshin; Newman, Martina; Webb, Craig

    2016-05-02

    This presentation provides a high-level overview of the progress on the Broadband Outdoor Radiometer Calibrations for all shortwave and longwave radiometers that are deployed by the Atmospheric Radiation Measurement program.

  16. SRHA calibration curve

    Data.gov (United States)

    U.S. Environmental Protection Agency — an UV calibration curve for SRHA quantitation This dataset is associated with the following publication: Chang, X., and D. Bouchard. Surfactant-Wrapped Multiwalled...

  17. Calibrating nacelle lidars

    DEFF Research Database (Denmark)

    Courtney, Michael

    Nacelle mounted, forward looking wind lidars are beginning to be used to provide reference wind speed measurements for the power performance testing of wind turbines. In such applications, a formal calibration procedure with a corresponding uncertainty assessment will be necessary. This report...... presents four concepts for performing such a nacelle lidar calibration. Of the four methods, two are found to be immediately relevant and are pursued in some detail. The first of these is a line of sight calibration method in which both lines of sight (for a two beam lidar) are individually calibrated...... a representative distribution of radial wind speeds. An alternative method is to place the nacelle lidar on the ground and incline the beams upwards to bisect a mast equipped with reference instrumentation at a known height and range. This method will be easier and faster to implement and execute but the beam...

  18. Variability of average SUV from several hottest voxels is lower than that of SUVmax and SUVpeak

    Energy Technology Data Exchange (ETDEWEB)

    Laffon, E. [CHU de Bordeaux, Service de Medecine Nucleaire, Hopital du Haut-Leveque, Pessac (France); Universite de Bordeaux 2, Centre de Recherche Cardio-Thoracique, Bordeaux (France); INSERM U 1045, Centre de Recherche Cardio-Thoracique, Bordeaux (France); Lamare, F.; Clermont, H. de [CHU de Bordeaux, Service de Medecine Nucleaire, Hopital du Haut-Leveque, Pessac (France); Burger, I.A. [University Hospital of Zurich, Division of Nuclear Medicine, Department Medical Radiology, Zurich (Switzerland); Marthan, R. [Universite de Bordeaux 2, Centre de Recherche Cardio-Thoracique, Bordeaux (France); INSERM U 1045, Centre de Recherche Cardio-Thoracique, Bordeaux (France)

    2014-08-15

    To assess variability of the average standard uptake value (SUV) computed by varying the number of hottest voxels within an {sup 18}F-fluorodeoxyglucose ({sup 18}F-FDG)-positive lesion. This SUV metric was compared with the maximal SUV (SUV{sub max}: the hottest voxel) and peak SUV (SUV{sub peak}: SUV{sub max} and its 26 neighbouring voxels). Twelve lung cancer patients (20 lesions) were analysed using PET dynamic acquisition involving ten successive 2.5-min frames. In each frame and lesion, average SUV obtained from the N = 5, 10, 15, 20, 25 or 30 hottest voxels (SUV{sub max-N}){sub ,} SUV{sub max} and SUV{sub peak} were assessed. The relative standard deviations (SDrs) from ten frames were calculated for each SUV metric and lesion, yielding the mean relative SD from 20 lesions for each SUV metric (SDr{sub N}, SDr{sub max} and SDr{sub peak}), and hence relative measurement error and repeatability (MEr-R). For each N, SDr{sub N} was significantly lower than SDr{sub max} and SDr{sub peak}. SDr{sub N} correlated strongly with N: 6.471 x N{sup -0.103} (r = 0.994; P < 0.01). MEr-R of SUV{sub max-30} was 8.94-12.63 % (95 % CL), versus 13.86-19.59 % and 13.41-18.95 % for SUV{sub max} and SUV{sub peak} respectively. Variability of SUV{sub max-N} is significantly lower than for SUV{sub max} and SUV{sub peak}. Further prospective studies should be performed to determine the optimal total hottest volume, as voxel volume may depend on the PET system. (orig.)

  19. Quantitative myocardial perfusion PET parametric imaging at the voxel-level.

    Science.gov (United States)

    Mohy-Ud-Din, Hassan; Lodge, Martin A; Rahmim, Arman

    2015-08-01

    Quantitative myocardial perfusion (MP) PET has the potential to enhance detection of early stages of atherosclerosis or microvascular dysfunction, characterization of flow-limiting effects of coronary artery disease (CAD), and identification of balanced reduction of flow due to multivessel stenosis. We aim to enable quantitative MP-PET at the individual voxel level, which has the potential to allow enhanced visualization and quantification of myocardial blood flow (MBF) and flow reserve (MFR) as computed from uptake parametric images. This framework is especially challenging for the (82)Rb radiotracer. The short half-life enables fast serial imaging and high patient throughput; yet, the acquired dynamic PET images suffer from high noise-levels introducing large variability in uptake parametric images and, therefore, in the estimates of MBF and MFR. Robust estimation requires substantial post-smoothing of noisy data, degrading valuable functional information of physiological and pathological importance. We present a feasible and robust approach to generate parametric images at the voxel-level that substantially reduces noise without significant loss of spatial resolution. The proposed methodology, denoted physiological clustering, makes use of the functional similarity of voxels to penalize deviation of voxel kinetics from physiological partners. The results were validated using extensive simulations (with transmural and non-transmural perfusion defects) and clinical studies. Compared to post-smoothing, physiological clustering depicted enhanced quantitative noise versus bias performance as well as superior recovery of perfusion defects (as quantified by CNR) with minimal increase in bias. Overall, parametric images obtained from the proposed methodology were robust in the presence of high-noise levels as manifested in the voxel time-activity-curves.

  20. Calibrating nacelle lidars

    OpenAIRE

    Courtney, Michael

    2013-01-01

    Nacelle mounted, forward looking wind lidars are beginning to be used to provide reference wind speed measurements for the power performance testing of wind turbines. In such applications, a formal calibration procedure with a corresponding uncertainty assessment will be necessary. This report presents four concepts for performing such a nacelle lidar calibration. Of the four methods, two are found to be immediately relevant and are pursued in some detail.The first of these is a line of sight...

  1. TWSTFT Link Calibration Report

    Science.gov (United States)

    2015-09-01

    box calibrator with unknown but constant total delay during a calibration tour Total Delay: The total electrical delay from the antenna phase center...to the UTCp including all the devices/cables that the satellite and clock signals pass through. It numerically equals the sum of all the sub-delays...PTB. To average out the dimnal effects and measurement noise , 5-7 days of continuous measurements is required. 3 Setups at the Lab(k) The setup

  2. Increasing power for voxel-wise genome-wide association studies: the random field theory, least square kernel machines and fast permutation procedures.

    Science.gov (United States)

    Ge, Tian; Feng, Jianfeng; Hibar, Derrek P; Thompson, Paul M; Nichols, Thomas E

    2012-11-01

    Imaging traits are thought to have more direct links to genetic variation than diagnostic measures based on cognitive or clinical assessments and provide a powerful substrate to examine the influence of genetics on human brains. Although imaging genetics has attracted growing attention and interest, most brain-wide genome-wide association studies focus on voxel-wise single-locus approaches, without taking advantage of the spatial information in images or combining the effect of multiple genetic variants. In this paper we present a fast implementation of voxel- and cluster-wise inferences based on the random field theory to fully use the spatial information in images. The approach is combined with a multi-locus model based on least square kernel machines to associate the joint effect of several single nucleotide polymorphisms (SNP) with imaging traits. A fast permutation procedure is also proposed which significantly reduces the number of permutations needed relative to the standard empirical method and provides accurate small p-value estimates based on parametric tail approximation. We explored the relation between 448,294 single nucleotide polymorphisms and 18,043 genes in 31,662 voxels of the entire brain across 740 elderly subjects from the Alzheimer's disease neuroimaging initiative (ADNI). Structural MRI scans were analyzed using tensor-based morphometry (TBM) to compute 3D maps of regional brain volume differences compared to an average template image based on healthy elderly subjects. We find method to be more sensitive compared with voxel-wise single-locus approaches. A number of genes were identified as having significant associations with volumetric changes. The most associated gene was GRIN2B, which encodes the N-methyl-d-aspartate (NMDA) glutamate receptor NR2B subunit and affects both the parietal and temporal lobes in human brains. Its role in Alzheimer's disease has been widely acknowledged and studied, suggesting the validity of the approach. The

  3. Calibrating nacelle lidars

    Energy Technology Data Exchange (ETDEWEB)

    Courtney, M.

    2013-01-15

    Nacelle mounted, forward looking wind lidars are beginning to be used to provide reference wind speed measurements for the power performance testing of wind turbines. In such applications, a formal calibration procedure with a corresponding uncertainty assessment will be necessary. This report presents four concepts for performing such a nacelle lidar calibration. Of the four methods, two are found to be immediately relevant and are pursued in some detail. The first of these is a line of sight calibration method in which both lines of sight (for a two beam lidar) are individually calibrated by accurately aligning the beam to pass close to a reference wind speed sensor. A testing procedure is presented, reporting requirements outlined and the uncertainty of the method analysed. It is seen that the main limitation of the line of sight calibration method is the time required to obtain a representative distribution of radial wind speeds. An alternative method is to place the nacelle lidar on the ground and incline the beams upwards to bisect a mast equipped with reference instrumentation at a known height and range. This method will be easier and faster to implement and execute but the beam inclination introduces extra uncertainties. A procedure for conducting such a calibration is presented and initial indications of the uncertainties given. A discussion of the merits and weaknesses of the two methods is given together with some proposals for the next important steps to be taken in this work. (Author)

  4. Energy calibration via correlation

    CERN Document Server

    Maier, Daniel

    2015-01-01

    The main task of an energy calibration is to find a relation between pulse-height values and the corresponding energies. Doing this for each pulse-height channel individually requires an elaborated input spectrum with an excellent counting statistics and a sophisticated data analysis. This work presents an easy to handle energy calibration process which can operate reliably on calibration measurements with low counting statistics. The method uses a parameter based model for the energy calibration and concludes on the optimal parameters of the model by finding the best correlation between the measured pulse-height spectrum and multiple synthetic pulse-height spectra which are constructed with different sets of calibration parameters. A CdTe-based semiconductor detector and the line emissions of an 241 Am source were used to test the performance of the correlation method in terms of systematic calibration errors for different counting statistics. Up to energies of 60 keV systematic errors were measured to be le...

  5. Multimodal Spatial Calibration for Accurately Registering EEG Sensor Positions

    Directory of Open Access Journals (Sweden)

    Jianhua Zhang

    2014-01-01

    Full Text Available This paper proposes a fast and accurate calibration method to calibrate multiple multimodal sensors using a novel photogrammetry system for fast localization of EEG sensors. The EEG sensors are placed on human head and multimodal sensors are installed around the head to simultaneously obtain all EEG sensor positions. A multiple views’ calibration process is implemented to obtain the transformations of multiple views. We first develop an efficient local repair algorithm to improve the depth map, and then a special calibration body is designed. Based on them, accurate and robust calibration results can be achieved. We evaluate the proposed method by corners of a chessboard calibration plate. Experimental results demonstrate that the proposed method can achieve good performance, which can be further applied to EEG source localization applications on human brain.

  6. Accuracy in the diagnosis of vertical root fractures, external root resorptions, and root perforations using cone-beam computed tomography with different voxel sizes of acquisition

    Directory of Open Access Journals (Sweden)

    Fernanda Paula Bragatto

    2016-01-01

    Conclusions: Voxel size 0.125 mm produced images with the best resolution without increasing radiation levels to the patient when compared to voxel sizes 0.200 and 0.250 mm. Voxel sizes 0.300 and 0.400 mm should be avoided in the identification of root alterations.

  7. Strategies for improving the Voxel-based statistical analysis for animal PET studies: assessment of cerebral glucose metabolism in cat deafness model

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Su; Lee, Jae Sung; Park, Min Hyun; Kang, Hye Jin; Im, Ki Chun; Moon, Dae Hyuk; Lim, Sang Moo; Oh, Seung Ha; Lee, Dong Soo [Seoul National Univ. College of Medicine, Seoul (Korea, Republic of)

    2007-07-01

    In imaging studies of the human brain, voxel-based statistical analysis method was widely used, since these methods were originally developed for the analysis of the human brain data, they are not optimal for the animal brain data. The aim of this study is to optimize the procedures for the 3D voxel-based statistical analysis of cat FDG PET brain images. A microPET Focus 120 scanner was used. Eight cats underwent FDG PET scans twice before and after inducing the deafness. Only the brain and adjacent regions were extracted from each data set by manual masking. Individual PET image at normal and deaf state was realigned to each other to remove the confounding effects by the different spatial normalization parameters on the results of statistical analyses. Distance between the sampling points on the reference image and kernel size of Gaussian filter applied to the images before estimating the realignment parameters were adjusted to 0.5 mm and 2 mm. Both data was then spatial normalized onto study-specific cat brain template. Spatially normalized PET data were smoothed and voxel-based paired t-test was performed. Cerebral glucose metabolism decreased significantly after the loss of hearing capability in parietal lobes, postcentral gyri, STG, MTG, lTG, and IC at both hemisphere and left SC (FDR corrected P < 0.05, k=50). Cerebral glucose metabolism in deaf cats was found to be significantly higher than in controls in the right cingulate (FDR corrected P < 0.05, k=50). The ROI analysis also showed significant reduction of glucose metabolism in the same areas as in the SPM analysis, except for some regions (P < 0.05). Method for the voxel-based analysis of cat brain PET data was optimized for analysis of cat brain PET. This result was also confirmed by ROI analysis. The results obtained demonstrated the high localization accuracy and specificity of the developed method, and were found to be useful for examining cerebral glucose metabolism in a cat cortical deafness model.

  8. Building Point Detection from Vehicle-Borne LiDAR Data Based on Voxel Group and Horizontal Hollow Analysis

    Directory of Open Access Journals (Sweden)

    Yu Wang

    2016-05-01

    Full Text Available Information extraction and three-dimensional (3D reconstruction of buildings using the vehicle-borne laser scanning (VLS system is significant for many applications. Extracting LiDAR points, from VLS, belonging to various types of building in large-scale complex urban environments still retains some problems. In this paper, a new technical framework for automatic and efficient building point extraction is proposed, including three main steps: (1 voxel group-based shape recognition; (2 category-oriented merging; and (3 building point identification by horizontal hollow ratio analysis. This article proposes a concept of “voxel group” based on the voxelization of VLS points: each voxel group is composed of several voxels that belong to one single real-world object. Then the shapes of point clouds in each voxel group are recognized and this shape information is utilized to merge voxel group. This article puts forward a characteristic nature of vehicle-borne LiDAR building points, called “horizontal hollow ratio”, for efficient extraction. Experiments are analyzed from two aspects: (1 building-based evaluation for overall experimental area; and (2 point-based evaluation for individual building using the completeness and correctness. The experimental results indicate that the proposed framework is effective for the extraction of LiDAR points belonging to various types of buildings in large-scale complex urban environments.

  9. Calibration Under Uncertainty.

    Energy Technology Data Exchange (ETDEWEB)

    Swiler, Laura Painton; Trucano, Timothy Guy

    2005-03-01

    This report is a white paper summarizing the literature and different approaches to the problem of calibrating computer model parameters in the face of model uncertainty. Model calibration is often formulated as finding the parameters that minimize the squared difference between the model-computed data (the predicted data) and the actual experimental data. This approach does not allow for explicit treatment of uncertainty or error in the model itself: the model is considered the %22true%22 deterministic representation of reality. While this approach does have utility, it is far from an accurate mathematical treatment of the true model calibration problem in which both the computed data and experimental data have error bars. This year, we examined methods to perform calibration accounting for the error in both the computer model and the data, as well as improving our understanding of its meaning for model predictability. We call this approach Calibration under Uncertainty (CUU). This talk presents our current thinking on CUU. We outline some current approaches in the literature, and discuss the Bayesian approach to CUU in detail.

  10. HAWC Timing Calibration

    CERN Document Server

    Huentemeyer, Petra; Dingus, Brenda

    2009-01-01

    The High-Altitude Water Cherenkov (HAWC) Experiment is a second-generation highsensitivity gamma-ray and cosmic-ray detector that builds on the experience and technology of the Milagro observatory. Like Milagro, HAWC utilizes the water Cherenkov technique to measure extensive air showers. Instead of a pond filled with water (as in Milagro) an array of closely packed water tanks is used. The event direction will be reconstructed using the times when the PMTs in each tank are triggered. Therefore, the timing calibration will be crucial for reaching an angular resolution as low as 0.25 degrees.We propose to use a laser calibration system, patterned after the calibration system in Milagro. Like Milagro, the HAWC optical calibration system will use ~1 ns laser light pulses. Unlike Milagro, the PMTs are optically isolated and require their own optical fiber calibration. For HAWC the laser light pulses will be directed through a series of optical fan-outs and fibers to illuminate the PMTs in approximately one half o...

  11. Prediction of fMRI time series of a single voxel using radial basis function neural network

    Science.gov (United States)

    Song, Sutao; Zhang, Jiacai; Yao, Li

    2011-03-01

    A great deal of current literature regarding functional neuroimaging has elucidated the relationships of neurons distributed all over the brain. Modern neuroimaging techniques, such as the functional MRI (fMRI), provide a convenient tool for people to study the correlation among different voxels as well as the spatio-temporal patterns of brain activity. In this study, we present a computational model using radial basis function neural network (RBF-NN) to predict the fMRI voxel activation with the activation of other voxels acquired at the same time. The fMRI data from a visual images stimuli presentation experiment was separated into two sets; one was used to train the model, and the other to validate the accuracy or generalizability of the model. In the visual stimuli presentation experiment, the subject did simple one-back-repetition tasks when four categories of stimuli (houses, faces, cars, and cats) were presented. Voxel sets A and B were selected from fMRI data by two different voxel selection criterion: (1) Voxel set A are those activated for any kind of object stronger than the other three objects in regions of interest (ROIs) without correction (P=0.001); (2) Voxel set B are those activated for at least one of the categories of stimuli within the ROIs (FWE correction, P=0.05). RBF-NN regression models construct the nonlinear relationship between the activation of voxels in A and B. Our test results showed that RBF-NN can capture the nonlinear relationship existing in neurons and reveal the relationship between voxel's activation from different brain regions.

  12. 基于 RGB 彩色和深度信息的人体关节点定位%Human body joint points calibration based on the RGB and depth information

    Institute of Scientific and Technical Information of China (English)

    肖秦琨; 赵艳; 高嵩

    2015-01-01

    在人体实时定位问题中,关节点定位成为了构建人体平面骨架模型、识别人体动作中一个重要研究课题。所以,提出了一种利用 RGB 彩色和深度信息来定位人体关节点的方法,首先利用 Kinect 来获取运动人体的 RGB 彩色和深度图像,接着根据人体所处背景的复杂程度来采用不同的人体分割方法将人体分割出来,再对得到的人体轮廓图像进行平滑处理,从而得到平滑且连通的人体轮廓二值图像,再采用细化算法提取出人体轮廓骨架,然后对关节点周围8个邻域的像素值进行分析,并结合人体各刚体部件的比例关系,对人体的16个关节点进行定位,进而构建出人体平面关节点模型。实验结果表明,与现有方法相比,该方法简单有效,能够从多种运动状态人体中提取出准确的关节点坐标,并具有较好的准确性和鲁棒性。%The calibration of joint points is an important research topic in the solution of construction of human two-di-mensional skeleton of models and recognition of human actions.In this paper,a novel approach about human body joint points calibration based on the RGB color and depth information was proposed.First of all,with the help of Kinect to get RGB color images and depth images,depending on the complexity of human background to divide the human body seg-mentation with different methods,and smoothing the obtained body contour images,body contour binary images are smooth and connected.Then body outline frames are extracted by thinning algorithm.Analyzing the joint 8-neighbor-hood pixel values,and combining with proportions of rigid body parts,sixteen joint points are calibrated.Finally,human two-dimensional joint of models are built.Experimental results show that this approach is simple and available compared with existing methods.Joint points are able to be located from human body with different states of motions,and with good

  13. A software to digital image processing to be used in the voxel phantom development.

    Science.gov (United States)

    Vieira, J W; Lima, F R A

    2009-11-15

    Anthropomorphic models used in computational dosimetry, also denominated phantoms, are based on digital images recorded from scanning of real people by Computed Tomography (CT) or Magnetic Resonance Imaging (MRI). The voxel phantom construction requests computational processing for transformations of image formats, to compact two-dimensional (2-D) images forming of three-dimensional (3-D) matrices, image sampling and quantization, image enhancement, restoration and segmentation, among others. Hardly the researcher of computational dosimetry will find all these available abilities in single software, and almost always this difficulty presents as a result the decrease of the rhythm of his researches or the use, sometimes inadequate, of alternative tools. The need to integrate the several tasks mentioned above to obtain an image that can be used in an exposure computational model motivated the development of the Digital Image Processing (DIP) software, mainly to solve particular problems in Dissertations and Thesis developed by members of the Grupo de Pesquisa em Dosimetria Numérica (GDN/CNPq). Because of this particular objective, the software uses the Portuguese idiom in their implementations and interfaces. This paper presents the second version of the DIP, whose main changes are the more formal organization on menus and menu items, and menu for digital image segmentation. Currently, the DIP contains the menus Fundamentos, Visualizações, Domínio Espacial, Domínio de Frequências, Segmentações and Estudos. Each menu contains items and sub-items with functionalities that, usually, request an image as input and produce an image or an attribute in the output. The DIP reads edits and writes binary files containing the 3-D matrix corresponding to a stack of axial images from a given geometry that can be a human body or other volume of interest. It also can read any type of computational image and to make conversions. When the task involves only an output image

  14. Development of VOXEL-MAN Three-Dimensional Navigator of Acupuncture%基于VOXEL-MAN针灸学三维影像浏览器的研究

    Institute of Scientific and Technical Information of China (English)

    邵水金; 牟芳芳; 严振国; 刘红菊; 白娟; 庄天戈; 赵静; 秦翊麟

    2005-01-01

    以腧穴解剖研究成果为基础,将临床常用的18个危险穴位的解剖结构数据融入汉堡大学VOXEL-MAN三维数字化虚拟人体中,开发一套VOXEL-MAN 3D Navigator:Acupuncture运行软件(针灸学三维影像浏览器),动态、三维显示腧穴的层次解剖结构和不同角度针刺所经过的断面解剖结构,并建立相关的知识库体系,能够加深对图像内容的理解,有利于提高临床针刺疗效和避免针刺意外事故的发生,并为针灸提供一种理想直观的多媒体教学手段和方法.

  15. 21 CFR 862.1150 - Calibrator.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Calibrator. 862.1150 Section 862.1150 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Chemistry Test Systems § 862.1150...

  16. Calibration Systems Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Myers, Tanya L.; Broocks, Bryan T.; Phillips, Mark C.

    2006-02-01

    The Calibration Systems project at Pacific Northwest National Laboratory (PNNL) is aimed towards developing and demonstrating compact Quantum Cascade (QC) laser-based calibration systems for infrared imaging systems. These on-board systems will improve the calibration technology for passive sensors, which enable stand-off detection for the proliferation or use of weapons of mass destruction, by replacing on-board blackbodies with QC laser-based systems. This alternative technology can minimize the impact on instrument size and weight while improving the quality of instruments for a variety of missions. The potential of replacing flight blackbodies is made feasible by the high output, stability, and repeatability of the QC laser spectral radiance.

  17. Ibis ground calibration

    Energy Technology Data Exchange (ETDEWEB)

    Bird, A.J.; Barlow, E.J.; Tikkanen, T. [Southampton Univ., School of Physics and Astronomy (United Kingdom); Bazzano, A.; Del Santo, M.; Ubertini, P. [Istituto di Astrofisica Spaziale e Fisica Cosmica - IASF/CNR, Roma (Italy); Blondel, C.; Laurent, P.; Lebrun, F. [CEA Saclay - Sap, 91 - Gif sur Yvette (France); Di Cocco, G.; Malaguti, E. [Istituto di Astrofisica Spaziale e Fisica-Bologna - IASF/CNR (Italy); Gabriele, M.; La Rosa, G.; Segreto, A. [Istituto di Astrofisica Spaziale e Fisica- IASF/CNR, Palermo (Italy); Quadrini, E. [Istituto di Astrofisica Spaziale e Fisica-Cosmica, EASF/CNR, Milano (Italy); Volkmer, R. [Institut fur Astronomie und Astrophysik, Tubingen (Germany)

    2003-11-01

    We present an overview of results obtained from IBIS ground calibrations. The spectral and spatial characteristics of the detector planes and surrounding passive materials have been determined through a series of calibration campaigns. Measurements of pixel gain, energy resolution, detection uniformity, efficiency and imaging capability are presented. The key results obtained from the ground calibration have been: - optimization of the instrument tunable parameters, - determination of energy linearity for all detection modes, - determination of energy resolution as a function of energy through the range 20 keV - 3 MeV, - demonstration of imaging capability in each mode, - measurement of intrinsic detector non-uniformity and understanding of the effects of passive materials surrounding the detector plane, and - discovery (and closure) of various leakage paths through the passive shielding system.

  18. TARGETLESS CAMERA CALIBRATION

    Directory of Open Access Journals (Sweden)

    L. Barazzetti

    2012-09-01

    Full Text Available In photogrammetry a camera is considered calibrated if its interior orientation parameters are known. These encompass the principal distance, the principal point position and some Additional Parameters used to model possible systematic errors. The current state of the art for automated camera calibration relies on the use of coded targets to accurately determine the image correspondences. This paper presents a new methodology for the efficient and rigorous photogrammetric calibration of digital cameras which does not require any longer the use of targets. A set of images depicting a scene with a good texture are sufficient for the extraction of natural corresponding image points. These are automatically matched with feature-based approaches and robust estimation techniques. The successive photogrammetric bundle adjustment retrieves the unknown camera parameters and their theoretical accuracies. Examples, considerations and comparisons with real data and different case studies are illustrated to show the potentialities of the proposed methodology.

  19. Iterative Magnetometer Calibration

    Science.gov (United States)

    Sedlak, Joseph

    2006-01-01

    This paper presents an iterative method for three-axis magnetometer (TAM) calibration that makes use of three existing utilities recently incorporated into the attitude ground support system used at NASA's Goddard Space Flight Center. The method combines attitude-independent and attitude-dependent calibration algorithms with a new spinning spacecraft Kalman filter to solve for biases, scale factors, nonorthogonal corrections to the alignment, and the orthogonal sensor alignment. The method is particularly well-suited to spin-stabilized spacecraft, but may also be useful for three-axis stabilized missions given sufficient data to provide observability.

  20. Micromechanical analysis of nanocomposites using 3D voxel based material model

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon

    2012-01-01

    A computational study on the effect of nanocomposite structures on the elastic properties is carried out with the use of the 3D voxel based model of materials and the combined Voigt–Reuss method. A hierarchical voxel based model of a material reinforced by an array of exfoliated and intercalated...... nanoclay platelets surrounded by interphase layers is developed. With this model, the elastic properties of the interphase layer are estimated using the inverse analysis. The effects of aspect ratio, intercalation and orientation of nanoparticles on the elastic properties of the nanocomposites are analyzed....... For modeling the damage in nanocomposites with intercalated structures, “four phase” model is suggested, in which the strength of “intrastack interphase” is lower than that of “outer” interphase around the nanoplatelets. Analyzing the effect of nanoreinforcement in the matrix on the failure probability...

  1. Whole-brain voxel-based morphometry of white matter in medial temporal lobe epilepsy

    Energy Technology Data Exchange (ETDEWEB)

    Yu Aihong [Department of Radiology, Xuanwu Hospital, Capital University of Medical Sciences, Beijing 100053 (China); Li Kuncheng [Department of Radiology, Xuanwu Hospital, Capital University of Medical Sciences, Beijing 100053 (China)], E-mail: Likuncheng@vip.sina.com; Li Lin; Shan Baoci [Institute of High Energy Physics, Chinese Academy of Sciences (China); Wang Yuping; Xue Sufang [Department of Neurology, Xuanwu Hospital, Capital University of Medical Sciences (China)

    2008-01-15

    Purpose: The purpose of this study was to analyze whole-brain white matter changes in medial temporal lobe epilepsy (MTLE). Materials and methods: We studied 23 patients with MTLE and 13 age- and sex-matched healthy control subjects using voxel-based morphometry (VBM) on T1-weighted 3D datasets. The seizure focus was right sided in 11 patients and left sided in 12. The data were collected on a 1.5 T MR system and analyzed by SPM 99 to generate white matter density maps. Results: Voxel-based morphometry revealed diffusively reduced white matter in MTLE prominently including bilateral frontal lobes, bilateral temporal lobes and corpus callosum. White matter reduction was also found in the bilateral cerebellar hemispheres in the left MTLE group. Conclusion: VBM is a simple and automated approach that is able to identify diffuse whole-brain white matter reduction in MTLE.

  2. Development of a voxel phantom of Japanese adult male in upright posture

    Energy Technology Data Exchange (ETDEWEB)

    Sato, K.; Endo, A.; Saito, K. [Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan); Noguchi, H. [Safety Administration Department, Japan Atomic Energy Agency, 4-49 Muramatsu, Tokai-mura, Naka-gun, Ibaraki-ken 319-1184 (Japan); Emoto, Y.; Koga, S. [Fujita Health University, School of Medicine, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake-shi, Aichi-ken 470-1192 (Japan)

    2007-07-01

    A Japanese voxel phantom in upright posture, JM2, has been developed on the basis of CT images of a healthy Japanese adult male. Body characteristics of JM2 were compared with those of the supine voxel phantom, JM, previously developed using CT images of the same person. Differences were found in the shapes of the spine and lower abdomen and the locations of several organs such as kidneys, liver and stomach between the two phantoms. Specific absorbed fractions (SAFs) for 24 target and 11 sources organs were calculated for monoenergetic photon ranging from 0.01 to 4 MeV. It was found that the SAFs for the kidneys as source organ and the lower large intestine wall as target organ in JM2 were significantly higher than those in JM for all photon energies. The differences of the SAFs between the two phantoms were attributed to the differences in the organ distance and organ geometry depending on the posture. (authors)

  3. Voxel-wise grey matter asymmetry analysis in left- and right-handers.

    Science.gov (United States)

    Ocklenburg, Sebastian; Friedrich, Patrick; Güntürkün, Onur; Genç, Erhan

    2016-10-28

    Handedness is thought to originate in the brain, but identifying its structural correlates in the cortex has yielded surprisingly incoherent results. One idea proclaimed by several authors is that structural grey matter asymmetries might underlie handedness. While some authors have found significant associations with handedness in different brain areas (e.g. in the central sulcus and precentral sulcus), others have failed to identify such associations. One method used by many researchers to determine structural grey matter asymmetries is voxel based morphometry (VBM). However, it has recently been suggested that the standard VBM protocol might not be ideal to assess structural grey matter asymmetries, as it establishes accurate voxel-wise correspondence across individuals but not across both hemispheres. This could potentially lead to biased and incoherent results. Recently, a new toolbox specifically geared at assessing structural asymmetries and involving accurate voxel-wise correspondence across hemispheres has been published [F. Kurth, C. Gaser, E. Luders. A 12-step user guide for analyzing voxel-wise gray matter asymmetries in statistical parametric mapping (SPM), Nat Protoc 10 (2015), 293-304]. Here, we used this new toolbox to re-assess grey matter asymmetry differences in left- vs. right-handers and linked them to quantitative measures of hand preference and hand skill. While we identified several significant left-right asymmetries in the overall sample, no difference between left- and right-handers reached significance after correction for multiple comparisons. These findings indicate that the structural brain correlates of handedness are unlikely to be rooted in macroscopic grey matter area differences that can be assessed with VBM. Future studies should focus on other potential structural correlates of handedness, e.g. structural white matter asymmetries.

  4. Voxel3D “搭积木”的建模软件

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    要介绍Voxel3D,先得作个名词解释:Voxel是Volume Element 这两个词的缩写,我们把Voxel叫做“体元”,它就相当于二维图像中的“像素”,是三维空间中的基本小方块。

  5. A voxel-wise encoding model for early visual areas decodes mental images of remembered scenes.

    Science.gov (United States)

    Naselaris, Thomas; Olman, Cheryl A; Stansbury, Dustin E; Ugurbil, Kamil; Gallant, Jack L

    2015-01-15

    Recent multi-voxel pattern classification (MVPC) studies have shown that in early visual cortex patterns of brain activity generated during mental imagery are similar to patterns of activity generated during perception. This finding implies that low-level visual features (e.g., space, spatial frequency, and orientation) are encoded during mental imagery. However, the specific hypothesis that low-level visual features are encoded during mental imagery is difficult to directly test using MVPC. The difficulty is especially acute when considering the representation of complex, multi-object scenes that can evoke multiple sources of variation that are distinct from low-level visual features. Therefore, we used a voxel-wise modeling and decoding approach to directly test the hypothesis that low-level visual features are encoded in activity generated during mental imagery of complex scenes. Using fMRI measurements of cortical activity evoked by viewing photographs, we constructed voxel-wise encoding models of tuning to low-level visual features. We also measured activity as subjects imagined previously memorized works of art. We then used the encoding models to determine if putative low-level visual features encoded in this activity could pick out the imagined artwork from among thousands of other randomly selected images. We show that mental images can be accurately identified in this way; moreover, mental image identification accuracy depends upon the degree of tuning to low-level visual features in the voxels selected for decoding. These results directly confirm the hypothesis that low-level visual features are encoded during mental imagery of complex scenes. Our work also points to novel forms of brain-machine interaction: we provide a proof-of-concept demonstration of an internet image search guided by mental imagery.

  6. An Eye Model for Computational Dosimetry Using A Multi-Scale Voxel Phantom

    Science.gov (United States)

    Caracappa, Peter F.; Rhodes, Ashley; Fiedler, Derek

    2014-06-01

    The lens of the eye is a radiosensitive tissue with cataract formation being the major concern. Recently reduced recommended dose limits to the lens of the eye have made understanding the dose to this tissue of increased importance. Due to memory limitations, the voxel resolution of computational phantoms used for radiation dose calculations is too large to accurately represent the dimensions of the eye. A revised eye model is constructed using physiological data for the dimensions of radiosensitive tissues, and is then transformed into a high-resolution voxel model. This eye model is combined with an existing set of whole body models to form a multi-scale voxel phantom, which is used with the MCNPX code to calculate radiation dose from various exposure types. This phantom provides an accurate representation of the radiation transport through the structures of the eye. Two alternate methods of including a high-resolution eye model within an existing whole body model are developed. The accuracy and performance of each method is compared against existing computational phantoms.

  7. A Voxel-based Method for Forest Change Detection after Fire Using LiDAR Data

    Science.gov (United States)

    Xu, Z.

    2015-12-01

    A Voxel-based Method for Forest Change Detection after Fire Using LiDAR DataZewei Xu and Jonathan A. Greenberg Traditional methods of forest fire modeling focus on the patterns of burning in two-dimensions at relatively coarse resolutions. However, fires spread in complex, three-dimensional patterns related to the horizontal and vertical distributions of woody fuel as well as the prevailing climate conditions, and the micro-scale patterns of fuel distributions over scales of only meters can determine the path that fire can take through a complex landscape. One challenge in understanding the full three-dimensional (3D) path that a fire takes through a landscape is a lack of data at landscape scales of these burns. Remote sensing approaches, while operating at landscape scales, typically focus on two-dimensional analyses using standard image-based change detection techniques. In this research, we develop a 3D voxel-based change detection method applied to multitemporal LiDAR data collected before and after forest fires in California to quantify the full 3D pattern of vegetation loss. By changing the size of the voxel, forest loss at different spatial scales is revealed. The 3D tunnel of fuel loss created by the fire was used to examine ground-to-crown transitions, firebreaks, and other three-dimensional aspects of a forest fire.

  8. Effective dose evaluation for BNCT brain tumor treatment based on voxel phantoms.

    Science.gov (United States)

    Wang, Jeng-Ning; Lee, Kuo-Wei; Jiang, Shiang-Huei

    2014-06-01

    For BNCT treatments, in addition to tumor target doses, non-negligible doses will result in all the remaining organs of the body. This work aims to evaluate the effective dose as well as the average absorbed doses of each of organs of patients with brain tumor treated in the BNCT epithermal neutron beam at THOR. The effective doses were evaluated according to the definitions of ICRP Publications 60 and 103 for the reference male and female computational phantoms developed in ICRP Publication 110 by using the MCNP5 Monte Carlo code with the THOR-Y09 beam source. The effective dose acquired in this work was compared with the results of our previous work calculated for an adult hermaphrodite mathematical phantom. It was found that the effective dose for the female voxel phantom is larger than that for the male voxel phantom by a factor of 1.2-1.5 and the effective dose for the voxel phantom is larger than that for the mathematical phantom by a factor of 1.3-1.6. For a typical brain tumor BNCT, the effective dose was calculated to be 1.51Sv and the average absorbed dose for eye lenses was 1.07Gy.

  9. VIDA: a voxel-based dosimetry method for targeted radionuclide therapy using Geant4.

    Science.gov (United States)

    Kost, Susan D; Dewaraja, Yuni K; Abramson, Richard G; Stabin, Michael G

    2015-02-01

    We have developed the Voxel-Based Internal Dosimetry Application (VIDA) to provide patient-specific dosimetry in targeted radionuclide therapy performing Monte Carlo simulations of radiation transport with the Geant4 toolkit. The code generates voxel-level dose rate maps using anatomical and physiological data taken from individual patients. Voxel level dose rate curves are then fit and integrated to yield a spatial map of radiation absorbed dose. In this article, we present validation studies using established dosimetry results, including self-dose factors (DFs) from the OLINDA/EXM program for uniform activity in unit density spheres and organ self- and cross-organ DFs in the Radiation Dose Assessment Resource (RADAR) reference adult phantom. The comparison with reference data demonstrated agreement within 5% for self-DFs to spheres and reference phantom source organs for four common radionuclides used in targeted therapy ((131)I, (90)Y, (111)In, (177)Lu). Agreement within 9% was achieved for cross-organ DFs. We also present dose estimates to normal tissues and tumors from studies of two non-Hodgkin Lymphoma patients treated by (131)I radioimmunotherapy, with comparison to results generated independently with another dosimetry code. A relative difference of 12% or less was found between methods for mean absorbed tumor doses accounting for tumor regression.

  10. The statistical analysis of multi-voxel patterns in functional imaging.

    Directory of Open Access Journals (Sweden)

    Kai Schreiber

    Full Text Available The goal of multi-voxel pattern analysis (MVPA in BOLD imaging is to determine whether patterns of activation across multiple voxels change with experimental conditions. MVPA is a powerful technique, its use is rapidly growing, but it poses serious statistical challenges. For instance, it is well-known that the slow nature of the BOLD response can lead to greatly exaggerated performance estimates. Methods are available to avoid this overestimation, and we present those here in tutorial fashion. We go on to show that, even with these methods, standard tests of significance such as Students' T and the binomial tests are invalid in typical MRI experiments. Only a carefully constructed permutation test correctly assesses statistical significance. Furthermore, our simulations show that performance estimates increase with both temporal as well as spatial signal correlations among multiple voxels. This dependence implies that a comparison of MVPA performance between areas, between subjects, or even between BOLD signals that have been preprocessed in different ways needs great care.

  11. Sensor Calibration in Support for NOAA's Satellite Mission

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Sensor calibration, including its definition, purpose, traceability options, methodology, complexity, and importance, is examined in this paper in the context of supporting NOAA's satellite mission. Common understanding of sensor calibration is essential for the effective communication among sensor vendors,calibration scientists, satellite operators, program managers, and remote sensing data users, who must cooperate to ensure that a nation's strategic investment in a sophisticated operational environmental satellite system serves the nation's interest and enhances the human lives around the world. Examples of calibration activities at NOAA/NESDIS/ORA are selected to further illustrate these concepts and to demonstrate the lessons learned from the past experience.

  12. Smart Calibration of Excavators

    DEFF Research Database (Denmark)

    Bro, Marie; Døring, Kasper; Ellekilde, Lars-Peter

    2005-01-01

    Excavators dig holes. But where is the bucket? The purpose of this report is to treat four different problems concerning calibrations of position indicators for excavators in operation at concrete construction sites. All four problems are related to the question of how to determine the precise ge...

  13. Calibrating Communication Competencies

    Science.gov (United States)

    Surges Tatum, Donna

    2016-11-01

    The Many-faceted Rasch measurement model is used in the creation of a diagnostic instrument by which communication competencies can be calibrated, the severity of observers/raters can be determined, the ability of speakers measured, and comparisons made between various groups.

  14. Entropic calibration revisited

    Energy Technology Data Exchange (ETDEWEB)

    Brody, Dorje C. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)]. E-mail: d.brody@imperial.ac.uk; Buckley, Ian R.C. [Centre for Quantitative Finance, Imperial College, London SW7 2AZ (United Kingdom); Constantinou, Irene C. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); Meister, Bernhard K. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)

    2005-04-11

    The entropic calibration of the risk-neutral density function is effective in recovering the strike dependence of options, but encounters difficulties in determining the relevant greeks. By use of put-call reversal we apply the entropic method to the time reversed economy, which allows us to obtain the spot price dependence of options and the relevant greeks.

  15. Calibration with Absolute Shrinkage

    DEFF Research Database (Denmark)

    Øjelund, Henrik; Madsen, Henrik; Thyregod, Poul

    2001-01-01

    is suggested to cope with the singular design matrix most often seen in chemometric calibration. Furthermore, the proposed algorithm may be generalized to all convex norms like Sigma/beta (j)/(gamma) where gamma greater than or equal to 1, i.e. a method that continuously varies from ridge regression...

  16. LOFAR facet calibration

    CERN Document Server

    van Weeren, R J; Hardcastle, M J; Shimwell, T W; Rafferty, D A; Sabater, J; Heald, G; Sridhar, S S; Dijkema, T J; Brunetti, G; Brüggen, M; Andrade-Santos, F; Ogrean, G A; Röttgering, H J A; Dawson, W A; Forman, W R; de Gasperin, F; Jones, C; Miley, G K; Rudnick, L; Sarazin, C L; Bonafede, A; Best, P N; Bîrzan, L; Cassano, R; Chyży, K T; Croston, J H; Ensslin, T; Ferrari, C; Hoeft, M; Horellou, C; Jarvis, M J; Kraft, R P; Mevius, M; Intema, H T; Murray, S S; Orrú, E; Pizzo, R; Simionescu, A; Stroe, A; van der Tol, S; White, G J

    2016-01-01

    LOFAR, the Low-Frequency Array, is a powerful new radio telescope operating between 10 and 240 MHz. LOFAR allows detailed sensitive high-resolution studies of the low-frequency radio sky. At the same time LOFAR also provides excellent short baseline coverage to map diffuse extended emission. However, producing high-quality deep images is challenging due to the presence of direction dependent calibration errors, caused by imperfect knowledge of the station beam shapes and the ionosphere. Furthermore, the large data volume and presence of station clock errors present additional difficulties. In this paper we present a new calibration scheme, which we name facet calibration, to obtain deep high-resolution LOFAR High Band Antenna images using the Dutch part of the array. This scheme solves and corrects the direction dependent errors in a number of facets that cover the observed field of view. Facet calibration provides close to thermal noise limited images for a typical 8 hr observing run at $\\sim$ 5arcsec resolu...

  17. Measurement System & Calibration report

    DEFF Research Database (Denmark)

    Kock, Carsten Weber; Vesth, Allan

    This Measurement System & Calibration report is describing DTU’s measurement system installed at a specific wind turbine. A major part of the sensors has been installed by others (see [1]) the rest of the sensors have been installed by DTU. The results of the measurements, described in this report...

  18. NVLAP calibration laboratory program

    Energy Technology Data Exchange (ETDEWEB)

    Cigler, J.L.

    1993-12-31

    This paper presents an overview of the progress up to April 1993 in the development of the Calibration Laboratories Accreditation Program within the framework of the National Voluntary Laboratory Accreditation Program (NVLAP) at the National Institute of Standards and Technology (NIST).

  19. A voxel-based investigation for MRI-only radiotherapy of the brain using ultra short echo times

    DEFF Research Database (Denmark)

    Edmund, Jens Morgenthaler; Kjer, Hans Martin; Van Leemput, Koen;

    2014-01-01

    , however, need to be assigned to the MRI images for dose calculation and patient setup based on digitally reconstructed radiographs (DRRs). Here, we investigate the geometric and dosimetric performance for a number of popular voxel-based methods to generate a so-called pseudo CT (pCT). Five patients...... receiving cranial irradiation, each containing a co-registered MRI and CT scan, were included. An ultra short echo time MRI sequence for bone visualization was used. Six methods were investigated for three popular types of voxel-based approaches; (1) threshold-based segmentation, (2) Bayesian segmentation...... including or excluding additional spatial information. Approach 3 used a statistical regression correlating MRI voxels with their corresponding CT voxels. A similar photon and proton treatment plan was generated for a target positioned between the nasal cavity and the brainstem for all patients. The CT...

  20. Mercury CEM Calibration

    Energy Technology Data Exchange (ETDEWEB)

    John F. Schabron; Joseph F. Rovani; Susan S. Sorini

    2007-03-31

    The Clean Air Mercury Rule (CAMR) which was published in the Federal Register on May 18, 2005, requires that calibration of mercury continuous emissions monitors (CEMs) be performed with NIST-traceable standards. Western Research Institute (WRI) is working closely with the Electric Power Research Institute (EPRI), the National Institute of Standards and Technology (NIST), and the Environmental Protection Agency (EPA) to facilitate the development of the experimental criteria for a NIST traceability protocol for dynamic elemental mercury vapor generators. The traceability protocol will be written by EPA. Traceability will be based on the actual analysis of the output of each calibration unit at several concentration levels ranging from about 2-40 ug/m{sup 3}, and this analysis will be directly traceable to analyses by NIST using isotope dilution inductively coupled plasma/mass spectrometry (ID ICP/MS) through a chain of analyses linking the calibration unit in the power plant to the NIST ID ICP/MS. Prior to this project, NIST did not provide a recommended mercury vapor pressure equation or list mercury vapor pressure in its vapor pressure database. The NIST Physical and Chemical Properties Division in Boulder, Colorado was subcontracted under this project to study the issue in detail and to recommend a mercury vapor pressure equation that the vendors of mercury vapor pressure calibration units can use to calculate the elemental mercury vapor concentration in an equilibrium chamber at a particular temperature. As part of this study, a preliminary evaluation of calibration units from five vendors was made. The work was performed by NIST in Gaithersburg, MD and Joe Rovani from WRI who traveled to NIST as a Visiting Scientist.

  1. 基于欧式距离变换的人体2D关节点标定%Study on 2D Joint Points Calibration of Human Based on Euclidean Distance Transform

    Institute of Scientific and Technical Information of China (English)

    蔡建军; 孔令富; 李海涛

    2012-01-01

    The calibration of joint points is the key problem in the solution of construction of human models and recognition of human actions. In this paper, a novel approach about the extraction of human 2D joint points based on Euclidean distance transform was proposed to locate joint points automatically in human image sequences with no manual intervention. Firstly, the method employs Euclidean distance transform to thin the object of human target in image sequences, then establishes the 2D human skeleton model with target area as a unit pixels wide, and conducts inquiries by getting the joint point using the eight values of neighboring pixels, so the real coordinates corresponding to the human 2D joint points can be extracted. Experimental results show that this approach is simple and available compared with existing techniques. The exact position coordinates are able to be captured from human body binary images with different states of motions, and with high precision and accuracy.%人体实时定位优化问题,关节点标定是构建人体模型、识别人体动作研究中要解决的一个关键问题.提出了一种欧式距离变换的人体2D关节点提取方法,从无手工干预的人体运动图像序列中自动实时定位关节点.首先采用欧式距离变换对图像序列中的人体目标对象进行细化,建立目标区域为单位像素宽的人体2D骨架模型,利用得到的关节点八邻域像素值情况进行查询,从而提取出对应的人体2D关节点的真实位置坐标.实验结果表明,与已有方法相比,改进方法简单有效,能够从多种不同运动状态的人体图像上提取出准确的人体关节点位置坐标,并具有较高的精度和准确性.

  2. Development and tests of a mouse voxel model dor MCNPX based on Digimouse images

    Energy Technology Data Exchange (ETDEWEB)

    Melo M, B.; Ferreira F, C. [Centro de Desenvolvimento da Tecnologia Nuclear / CNEN, Pte. Antonio Carlos No. 6627, Belo Horizonte 31270-901, Minas Gerais (Brazil); Garcia de A, I.; Machado T, B.; Passos Ribeiro de C, T., E-mail: bmm@cdtn.br [Universidade Federal de Minas Gerais, Departamento de Engenharia Nuclear, Pte. Antonio Carlos 6627, Belo Horizonte 31270-901, Minas Gerais (Brazil)

    2015-10-15

    Mice have been widely used in experimental protocols involving ionizing radiation. Biological effects (Be) induced by radiation can compromise studies results. Good estimates of mouse whole body and organs absorbed dose could provide valuable information to researchers. The aim of this study was to create and test a new voxel phantom for mice dosimetry from -Digimouse- project images. Micro CT images from Digimouse project were used in this work. Corel PHOTOPAINT software was utilized in segmentation process. The three-dimensional (3-D) model assembly and its voxel size manipulation were performed by Image J. SISCODES was used to adapt the model to run in MCNPX Monte Carlo code. The resulting model was called DM{sub B}RA. The volume and mass of segmented organs were compared with data available in literature. For the preliminary tests the heart was considered the source organ. Photons of diverse energies were simulated and Saf values obtained through F6:p and + F6 MCNPX tallies. The results were compared with reference data. 3-D picturing of absorbed doses patterns and relative errors distribution were generated by a C++ -in house- made program and visualized through Amide software. The organ masses of DM{sub B}RA correlated well with two models that were based on same set of images. However some organs, like eyes and adrenals, skeleton and brain showed large discrepancies. Segmentation of an identical image set by different persons and/or methods can result significant organ masses variations. We believe that the main causes of these differences were: i) operator dependent subjectivity in the definition of organ limits during the segmentation processes; and i i) distinct voxel dimensions between evaluated models. Lack of reference data for mice models construction and dosimetry was detected. Comparison with other models originated from different mice strains also demonstrated that the anatomical and size variability can be significant. Use of + F6 tally for mouse

  3. Assessing hippocampal functional reserve in temporal lobe epilepsy: A multi-voxel pattern analysis of fMRI data

    OpenAIRE

    Bonnici, Heidi M; Sidhu, Meneka; Chadwick, Martin J.; Duncan, John S.; Maguire, Eleanor A.

    2013-01-01

    Summary Assessing the functional reserve of key memory structures in the medial temporal lobes (MTL) of pre-surgical patients with intractable temporal lobe epilepsy (TLE) remains a challenge. Conventional functional MRI (fMRI) memory paradigms have yet to fully convince of their ability to confidently assess the risk of a post-surgical amnesia. An alternative fMRI analysis method, multi-voxel pattern analysis (MVPA), focuses on the patterns of activity across voxels in specific brain regions...

  4. Field calibration of cup anemometers

    DEFF Research Database (Denmark)

    Schmidt Paulsen, Uwe; Mortensen, Niels Gylling; Hansen, Jens Carsten

    2007-01-01

    A field calibration method and results are described along with the experience gained with the method. The cup anemometers to be calibrated are mounted in a row on a 10-m high rig and calibrated in the free wind against a reference cup anemometer. The method has been reported [1] to improve...... the statistical bias on the data relative to calibrations carried out in a wind tunnel. The methodology is sufficiently accurate for calibration of cup anemometers used for wind resource assessments and provides a simple, reliable and cost-effective solution to cup anemometer calibration, especially suited...

  5. CCD camera automatic calibration technology and ellipse recognition algorithm

    Institute of Scientific and Technical Information of China (English)

    Changku Sun; Xiaodong Zhang; Yunxia Qu

    2005-01-01

    A novel two-dimensional (2D) pattern used in camera calibration is presented. With one feature circle located at the center, an array of circles is photo-etched on this pattern. An ellipse recognition algorithm is proposed to implement the acquisition of interest calibration points without human intervention. According to the circle arrangement of the pattern, the relation between three-dimensional (3D) and 2D coordinates of these points can be established automatically and accurately. These calibration points are computed for intrinsic parameters calibration of charge-coupled device (CCD) camera with Tsai method. A series of experiments have shown that the algorithm is robust and reliable with the calibration error less than 0.4 pixel. This new calibration pattern and ellipse recognition algorithm can be widely used in computer vision.

  6. In vitro comparison of cone beam computed tomography with different voxel sizes for detection of simulated external root resorption.

    Science.gov (United States)

    Neves, Frederico S; de Freitas, Deborah Q; Campos, Paulo S F; de Almeida, Solange M; Haiter-Neto, Francisco

    2012-09-01

    The present study compared the efficacy of cone beam computed tomography using different voxel sizes in the diagnosis of simulated external root resorption. The presence or absence of simulated defects on buccal, mesial and distal root surfaces of 20 premolars was evaluated. The defects were small (0.26 mm in diameter and 0.08 mm deep), medium (0.62 mm in diameter and 0.19 mm deep) and large (1.05 mm in diameter and 0.24 mm deep), equally distributed on each root surface. Images were obtained using Classic i-CAT cone beam computed tomography with different voxel sizes: 0.12, 0.20, 0.25 and 0.30 mm. Five oral radiologists evaluated the images. Accuracy, sensitivity, specificity, positive and negative predictive values were determined. The sensitivity decreased and specificity increased as voxel size increased. Accuracy values were the highest for the smallest voxel size (0.12 mm). The results for voxel sizes 0.20 mm and 0.25 mm were similar. Positive and negative predictive values were similar in all protocols, except with 0.30 mm, in which they were the lowest. In conclusion, external root resorption was more easily diagnosed when a smaller voxel size was used.

  7. Comparison between external and internal standard calibration in the validation of an analytical method for 1-hydroxypyrene in human urine by high-performance liquid chromatography/tandem mass spectrometry.

    Science.gov (United States)

    Pigini, D; Cialdella, A M; Faranda, P; Tranfo, G

    2006-01-01

    1-Hydroxypyrene is a metabolite of pyrene, a member of the class of polycyclic aromatic hydrocarbons (PAHs) whose toxic properties in some cases include carcinogenicity. The determination of 1-hydroxypyrene in human urine is used as a biological indicator for exposure to PAHs, which is related to the combustion of organic materials, like smoking, living in urban environments, and eating grilled or smoked food. The determination of 1-hydroxypyrene by high-performance liquid chromatography (HPLC) with fluorescence detection has very good sensitivity but it is not highly specific: this can reduce accuracy in the quantitative determination of low levels of analyte in a complex matrix like urine. An HPLC method that uses triple quadrupole mass detection has been validated with the objective both to improve the signal-to-noise (S/N) ratio and to achieve the maximum specificity for the analyte in those urine samples that are richer in possible inteferents. The calibration range for 1-hydroxypyrene is from 0.005-0.1 microg/L in the urine of non-smoking healthy volunteers. After solid-phase extraction, samples were analyzed by HPLC/tandem mass spectrometry (MS/MS) in the multiple reaction monitoring (MRM) mode. In order to obtain reliable results quantitative analysis must be performed by means of the internal standard method (we used deuterium-labelled 1-hydroxypyrene): the method accuracy is not less than 85%. The S/N ratio at a concentration of 0.1 microg/L is about 10, and therefore this can be considered the lowest limit of quantitation. The method performance does not change if urine samples are measured using a calibration curve prepared in methanol, thus reducing the time of analysis and costs.

  8. Mercury Calibration System

    Energy Technology Data Exchange (ETDEWEB)

    John Schabron; Eric Kalberer; Joseph Rovani; Mark Sanderson; Ryan Boysen; William Schuster

    2009-03-11

    U.S. Environmental Protection Agency (EPA) Performance Specification 12 in the Clean Air Mercury Rule (CAMR) states that a mercury CEM must be calibrated with National Institute for Standards and Technology (NIST)-traceable standards. In early 2009, a NIST traceable standard for elemental mercury CEM calibration still does not exist. Despite the vacature of CAMR by a Federal appeals court in early 2008, a NIST traceable standard is still needed for whatever regulation is implemented in the future. Thermo Fisher is a major vendor providing complete integrated mercury continuous emissions monitoring (CEM) systems to the industry. WRI is participating with EPA, EPRI, NIST, and Thermo Fisher towards the development of the criteria that will be used in the traceability protocols to be issued by EPA. An initial draft of an elemental mercury calibration traceability protocol was distributed for comment to the participating research groups and vendors on a limited basis in early May 2007. In August 2007, EPA issued an interim traceability protocol for elemental mercury calibrators. Various working drafts of the new interim traceability protocols were distributed in late 2008 and early 2009 to participants in the Mercury Standards Working Committee project. The protocols include sections on qualification and certification. The qualification section describes in general terms tests that must be conducted by the calibrator vendors to demonstrate that their calibration equipment meets the minimum requirements to be established by EPA for use in CAMR monitoring. Variables to be examined include linearity, ambient temperature, back pressure, ambient pressure, line voltage, and effects of shipping. None of the procedures were described in detail in the draft interim documents; however they describe what EPA would like to eventually develop. WRI is providing the data and results to EPA for use in developing revised experimental procedures and realistic acceptance criteria based on

  9. Brain structural abnormalities in behavior therapy-resistant obsessive-compulsive disorder revealed by voxel-based morphometry

    Directory of Open Access Journals (Sweden)

    Hashimoto N

    2014-10-01

    Full Text Available Nobuhiko Hashimoto,1 Shutaro Nakaaki,2 Akiko Kawaguchi,1 Junko Sato,1 Harumasa Kasai,3 Takashi Nakamae,4 Jin Narumoto,4 Jun Miyata,5 Toshi A Furukawa,6,7 Masaru Mimura2 1Department of Psychiatry and Cognitive-Behavioral Medicine, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan; 2Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan; 3Department of Central Radiology, Nagoya City University Hospital, Nagoya, Japan; 4Department of Psychiatry, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan; 5Department of Psychiatry, Graduate School of Medicine, Kyoto University, Kyoto, Japan; 6Department of Health Promotion and Human Behavior, 7Department of Clinical Epidemiology, Kyoto University Graduate School of Medicine/School of Public Health, Kyoto, Japan Background: Although several functional imaging studies have demonstrated that behavior therapy (BT modifies the neural circuits involved in the pathogenesis of obsessive-compulsive disorder (OCD, the structural abnormalities underlying BT-resistant OCD remain unknown. Methods: In this study, we examined the existence of regional structural abnormalities in both the gray matter and the white matter of patients with OCD at baseline using voxel-based morphometry in responders (n=24 and nonresponders (n=15 to subsequent BT. Three-dimensional T1-weighted magnetic resonance imaging was performed before the completion of 12 weeks of BT. Results: Relative to the responders, the nonresponders exhibited significantly smaller gray matter volumes in the right ventromedial prefrontal cortex, the right orbitofrontal cortex, the right precentral gyrus, and the left anterior cingulate cortex. In addition, relative to the responders, the nonresponders exhibited significantly smaller white matter volumes in the left cingulate bundle and the left superior frontal white matter. Conclusion: These results suggest that the brain

  10. Relationship between personality and gray matter volume in healthy young adults: a voxel-based morphometric study.

    Directory of Open Access Journals (Sweden)

    Fengmei Lu

    Full Text Available This study aims to investigate the neurostructural foundations of the human personality in young adults. High-resolution structural T1-weighted MR images of 71 healthy young individuals were processed using voxel-based morphometric (VBM approach. Multiple regression analyses were performed to identify the associations between personality traits and gray matter volume (GMV. The Eysenck Personality Questionnaire-Revised, Short Scale for Chinese was chosen to assess the personality traits. This scale includes four dimensions, namely, extraversion, neuroticism, psychoticism, and lie. Particularly, we studied on two dimensions (extraversion and neuroticism of Eysenck's personality. Our results showed that extraversion was negatively correlated with GMV of the bilateral amygdala, the bilateral parahippocampal gyrus, the right middle temporal gyrus, and the left superior frontal gyrus, all of which are involved in emotional and social cognitive processes. These results might suggest an association between extraversion and affective processing. In addition, a positive correlation was detected between neuroticism and GMV of the right cerebellum, a key brain region for negative affect coordination. Meanwhile, a negative association was revealed between GMV of the left superior frontal gyrus and neuroticism. These results may prove that neuroticism is related to several brain regions involved in regulating negative emotions. Based on those findings, we concluded that brain regions involved in social cognition and affective process accounted for modulation and shaping of personality traits among young individuals. Results of this study may serve as a basis for elucidating the anatomical factors of personality.

  11. Relationship between personality and gray matter volume in healthy young adults: a voxel-based morphometric study.

    Science.gov (United States)

    Lu, Fengmei; Huo, Yajun; Li, Meiling; Chen, Heng; Liu, Feng; Wang, Yifeng; Long, Zhiliang; Duan, Xujun; Zhang, Jiang; Zeng, Ling; Chen, Huafu

    2014-01-01

    This study aims to investigate the neurostructural foundations of the human personality in young adults. High-resolution structural T1-weighted MR images of 71 healthy young individuals were processed using voxel-based morphometric (VBM) approach. Multiple regression analyses were performed to identify the associations between personality traits and gray matter volume (GMV). The Eysenck Personality Questionnaire-Revised, Short Scale for Chinese was chosen to assess the personality traits. This scale includes four dimensions, namely, extraversion, neuroticism, psychoticism, and lie. Particularly, we studied on two dimensions (extraversion and neuroticism) of Eysenck's personality. Our results showed that extraversion was negatively correlated with GMV of the bilateral amygdala, the bilateral parahippocampal gyrus, the right middle temporal gyrus, and the left superior frontal gyrus, all of which are involved in emotional and social cognitive processes. These results might suggest an association between extraversion and affective processing. In addition, a positive correlation was detected between neuroticism and GMV of the right cerebellum, a key brain region for negative affect coordination. Meanwhile, a negative association was revealed between GMV of the left superior frontal gyrus and neuroticism. These results may prove that neuroticism is related to several brain regions involved in regulating negative emotions. Based on those findings, we concluded that brain regions involved in social cognition and affective process accounted for modulation and shaping of personality traits among young individuals. Results of this study may serve as a basis for elucidating the anatomical factors of personality.

  12. Entorhinal volume, aerobic fitness, and recognition memory in healthy young adults: A voxel-based morphometry study.

    Science.gov (United States)

    Whiteman, Andrew S; Young, Daniel E; Budson, Andrew E; Stern, Chantal E; Schon, Karin

    2016-02-01

    Converging evidence supports the hypothesis effects of aerobic exercise and environmental enrichment are beneficial for cognition, in particular for hippocampus-supported learning and memory. Recent work in humans suggests that exercise training induces changes in hippocampal volume, but it is not known if aerobic exercise and fitness also impact the entorhinal cortex. In animal models, aerobic exercise increases expression of growth factors, including brain derived neurotrophic factor (BDNF). This exercise-enhanced expression of growth hormones may boost synaptic plasticity, and neuronal survival and differentiation, potentially supporting function and structure in brain areas including but not limited to the hippocampus. Here, using voxel based morphometry and a standard graded treadmill test to determine cardio-respiratory fitness (Bruce protocol; ·VO2 max), we examined if entorhinal and hippocampal volumes were associated with cardio-respiratory fitness in healthy young adults (N=33). In addition, we examined if volumes were modulated by recognition memory performance and by serum BDNF, a putative marker of synaptic plasticity. Our results show a positive association between volume in right entorhinal cortex and cardio-respiratory fitness. In addition, average gray matter volume in the entorhinal cortex, bilaterally, was positively associated with memory performance. These data extend prior work on the cerebral effects of aerobic exercise and fitness to the entorhinal cortex in healthy young adults thus providing compelling evidence for a relationship between aerobic fitness and structure of the medial temporal lobe memory system.

  13. PHOTOMETRYPIPELINE: An automated pipeline for calibrated photometry

    Science.gov (United States)

    Mommert, M.

    2017-01-01

    PHOTOMETRYPIPELINE (PP) is an automated pipeline that produces calibrated photometry from imaging data through image registration, aperture photometry, photometric calibration, and target identification with only minimal human interaction. PP utilizes the widely used Source Extractor software for source identification and aperture photometry; SCAMP is used for image registration. Both image registration and photometric calibration are based on matching field stars with star catalogs, requiring catalog coverage of the respective field. A number of different astrometric and photometric catalogs can be queried online. Relying on a sufficient number of background stars for image registration and photometric calibration, PP is well-suited to analyze data from small to medium-sized telescopes. Calibrated magnitudes obtained by PP are typically accurate within ≤0.03 mag and astrometric accuracies are of the order of 0.3 arcsec relative to the catalogs used in the registration. The pipeline consists of an open-source software suite written in Python 2.7, can be run on Unix-based systems on a simple desktop machine, and is capable of realtime data analysis. PP has been developed for observations of moving targets, but can be used for analyzing point source observations of any kind.

  14. The Calibration Reference Data System

    Science.gov (United States)

    Greenfield, P.; Miller, T.

    2016-07-01

    We describe a software architecture and implementation for using rules to determine which calibration files are appropriate for calibrating a given observation. This new system, the Calibration Reference Data System (CRDS), replaces what had been previously used for the Hubble Space Telescope (HST) calibration pipelines, the Calibration Database System (CDBS). CRDS will be used for the James Webb Space Telescope (JWST) calibration pipelines, and is currently being used for HST calibration pipelines. CRDS can be easily generalized for use in similar applications that need a rules-based system for selecting the appropriate item for a given dataset; we give some examples of such generalizations that will likely be used for JWST. The core functionality of the Calibration Reference Data System is available under an Open Source license. CRDS is briefly contrasted with a sampling of other similar systems used at other observatories.

  15. Lidar calibration experiments

    DEFF Research Database (Denmark)

    Ejsing Jørgensen, Hans; Mikkelsen, T.; Streicher, J.

    1997-01-01

    A series of atmospheric aerosol diffusion experiments combined with lidar detection was conducted to evaluate and calibrate an existing retrieval algorithm for aerosol backscatter lidar systems. The calibration experiments made use of two (almost) identical mini-lidar systems for aerosol cloud...... detection to test the reproducibility and uncertainty of lidars. Lidar data were obtained from both single-ended and double-ended Lidar configurations. A backstop was introduced in one of the experiments and a new method was developed where information obtained from the backstop can be used in the inversion...... algorithm. Independent in-situ aerosol plume concentrations were obtained from a simultaneous tracer gas experiment with SF6, and comparisons with the two lidars were made. The study shows that the reproducibility of the lidars is within 15%, including measurements from both sides of a plume...

  16. Optical tweezers absolute calibration

    CERN Document Server

    Dutra, R S; Neto, P A Maia; Nussenzveig, H M

    2014-01-01

    Optical tweezers are highly versatile laser traps for neutral microparticles, with fundamental applications in physics and in single molecule cell biology. Force measurements are performed by converting the stiffness response to displacement of trapped transparent microspheres, employed as force transducers. Usually, calibration is indirect, by comparison with fluid drag forces. This can lead to discrepancies by sizable factors. Progress achieved in a program aiming at absolute calibration, conducted over the past fifteen years, is briefly reviewed. Here we overcome its last major obstacle, a theoretical overestimation of the peak stiffness, within the most employed range for applications, and we perform experimental validation. The discrepancy is traced to the effect of primary aberrations of the optical system, which are now included in the theory. All required experimental parameters are readily accessible. Astigmatism, the dominant effect, is measured by analyzing reflected images of the focused laser spo...

  17. Astrid-2 SSC ASUMagnetic Calibration

    DEFF Research Database (Denmark)

    Primdahl, Fritz

    1997-01-01

    Report of the inter calibration between the starcamera and the fluxgate magnetometer onboard the ASTRID-2 satellite. This calibration was performed in the night between the 15. and 16. May 1997 at the Lovö magnetic observatory.......Report of the inter calibration between the starcamera and the fluxgate magnetometer onboard the ASTRID-2 satellite. This calibration was performed in the night between the 15. and 16. May 1997 at the Lovö magnetic observatory....

  18. Calibration Facilities for NIF

    Energy Technology Data Exchange (ETDEWEB)

    Perry, T.S.

    2000-06-15

    The calibration facilities will be dynamic and will change to meet the needs of experiments. Small sources, such as the Manson Source should be available to everyone at any time. Carrying out experiments at Omega is providing ample opportunity for practice in pre-shot preparation. Hopefully, the needs that are demonstrated in these experiments will assure the development of (or keep in service) facilities at each of the laboratories that will be essential for in-house preparation for experiments at NIF.

  19. Mesoscale hybrid calibration artifact

    Science.gov (United States)

    Tran, Hy D.; Claudet, Andre A.; Oliver, Andrew D.

    2010-09-07

    A mesoscale calibration artifact, also called a hybrid artifact, suitable for hybrid dimensional measurement and the method for make the artifact. The hybrid artifact has structural characteristics that make it suitable for dimensional measurement in both vision-based systems and touch-probe-based systems. The hybrid artifact employs the intersection of bulk-micromachined planes to fabricate edges that are sharp to the nanometer level and intersecting planes with crystal-lattice-defined angles.

  20. How does an fMRI voxel sample the neuronal activity pattern: compact-kernel or complex spatiotemporal filter?

    Science.gov (United States)

    Kriegeskorte, Nikolaus; Cusack, Rhodri; Bandettini, Peter

    2010-02-01

    Recent studies suggested that fMRI voxel patterns can convey information represented in columnar-scale neuronal population codes, even when spatial resolution is insufficient to directly image the patterns of columnar selectivity (Kamitani and Tong, 2005; Haynes and Rees, 2005). Sensitivity to subvoxel-scale pattern information, or "fMRI hyperacuity," would greatly enhance the power of fMRI when combined with pattern information analysis techniques (Kriegeskorte and Bandettini, 2007). An individual voxel might weakly reflect columnar-level information if the columns within its boundaries constituted a slightly unbalanced sample of columnar selectivities (Kamitani and Tong, 2005), providing a possible mechanism for fMRI hyperacuity. However, Op de Beeck (2009) suggests that a coarse-scale neuronal organization rather than fMRI hyperacuity may explain the presence of the information in the fMRI patterns. Here we argue (a) that the present evidence does not rule out fMRI hyperacuity, (b) that the mechanism originally suggested for fMRI hyperacuity (biased sampling by averaging within each voxel's boundaries; Kamitani and Tong, 2005) will only produce very weak sensitivity to fine-grained pattern information, and (c) that an alternative mechanism (voxel as complex spatiotemporal filter) is physiologically more accurate and promises stronger sensitivity to fine-grained pattern information: We know that each voxel samples the neuronal activity pattern through a unique fine-grained structure of venous vessels that supply its blood oxygen level-dependent signal. At the simplest level, the drainage domain of a venous vessel may sample the neuronal pattern with a selectivity bias (Gardner, 2009; Shmuel et al., 2009). Beyond biased drainage domains, we illustrate with a simple simulation how temporal properties of the hemodynamics (e.g., the speed of the blood in the capillary bed) can shape spatial properties of a voxel's filter (e.g., how finely structured it is). This

  1. Calibration of Underwater Sound Transducers

    Directory of Open Access Journals (Sweden)

    H.R.S. Sastry

    1983-07-01

    Full Text Available The techniques of calibration of underwater sound transducers for farfield, near-field and closed environment conditions are reviewed in this paper .The design of acoustic calibration tank is mentioned. The facilities available at Naval Physical & Oceanographic Laboratory, Cochin for calibration of transducers are also listed.

  2. Internet-based calibration of a multifunction calibrator

    Energy Technology Data Exchange (ETDEWEB)

    BUNTING BACA,LISA A.; DUDA JR.,LEONARD E.; WALKER,RUSSELL M.; OLDHAM,NILE; PARKER,MARK

    2000-04-17

    A new way of providing calibration services is evolving which employs the Internet to expand present capabilities and make the calibration process more interactive. Sandia National Laboratories and the National Institute of Standards and Technology are collaborating to set up and demonstrate a remote calibration of multifunction calibrators using this Internet-based technique that is becoming known as e-calibration. This paper describes the measurement philosophy and the Internet resources that can provide real-time audio/video/data exchange, consultation and training, as well as web-accessible test procedures, software and calibration reports. The communication system utilizes commercial hardware and software that should be easy to integrate into most calibration laboratories.

  3. Method of biodosimeter calibration for orbital flight

    Science.gov (United States)

    Vladislav, Petrov

    A biodosimetry method, based on estimation of an absorbed dose on the basis of assessment of unstable aberration frequency in the lymphocytes of human's peripheral blood is used broadly in ground conditions for analysis of accidental exposure to personal and citizens. A calibration curve giving the relationship between aberration frequency (generally dicentrics and centric rings) and an absorbed dose in blood samples is used for assessment of crewmember exposure. As a rule gamma - rays corresponding to character of exposure in such accidents are used for these goals. At the same time the space radiation fields are formed mainly by charged particles for which the character of effect on the body cells and tissues differs strongly from that of gamma - rays. As biodosimetry is a relative method of dose measurement it is necessary to obtain a calibration curve corresponding to the conditions in which the measurements will be performed. That is a calibration curve for space application should give a relationship between aberration frequency and a dose formed by radiation field equal to that on the spacecraft trajectory. The report contains a method of obtaining a calibration curve for a case of an orbital flight on the ISS trajectory. The radiobiological basis of the method consists of relationships between chromosomal aberration frequency in human blood lymphocytes and an absorbed dose of protons with four energies (50 MeV, 150 MeV, 400 MeV, 625 MeV) obtained in the accelerator's experiments. Due to the fact that we had experimental data only for protons the calibration curve was obtained for the proton component on the ISS orbit which is mainly formed by trapped protons. Dose spectrum for this energy distribution of protons was calculated and weighting coefficients for taking into account the input of dose of protons with various energies in forming total frequency of chromosomal aberrations were obtained on its basis. The procedure of obtaining such weighting

  4. Imaging lung function in mice using SPECT/CT and per-voxel analysis.

    Directory of Open Access Journals (Sweden)

    Brian N Jobse

    Full Text Available Chronic lung disease is a major worldwide health concern but better tools are required to understand the underlying pathologies. Ventilation/perfusion (V/Q single photon emission computed tomography (SPECT with per-voxel analysis allows for non-invasive measurement of regional lung function. A clinically adapted V/Q methodology was used in healthy mice to investigate V/Q relationships. Twelve week-old mice were imaged to describe normal lung function while 36 week-old mice were imaged to determine how age affects V/Q. Mice were ventilated with Technegas™ and injected with (99mTc-macroaggregated albumin to trace ventilation and perfusion, respectively. For both processes, SPECT and CT images were acquired, co-registered, and quantitatively analyzed. On a per-voxel basis, ventilation and perfusion were moderately correlated (R = 0.58±0.03 in 12 week old animals and a mean log(V/Q ratio of -0.07±0.01 and standard deviation of 0.36±0.02 were found, defining the extent of V/Q matching. In contrast, 36 week old animals had significantly increased levels of V/Q mismatching throughout the periphery of the lung. Measures of V/Q were consistent across healthy animals and differences were observed with age demonstrating the capability of this technique in quantifying lung function. Per-voxel analysis and the ability to non-invasively assess lung function will aid in the investigation of chronic lung disease models and drug efficacy studies.

  5. A GPU-based Monte Carlo dose calculation code for photon transport in a voxel phantom

    Energy Technology Data Exchange (ETDEWEB)

    Bellezzo, M.; Do Nascimento, E.; Yoriyaz, H., E-mail: mbellezzo@gmail.br [Instituto de Pesquisas Energeticas e Nucleares / CNEN, Av. Lineu Prestes 2242, Cidade Universitaria, 05508-000 Sao Paulo (Brazil)

    2014-08-15

    As the most accurate method to estimate absorbed dose in radiotherapy, Monte Carlo method has been widely used in radiotherapy treatment planning. Nevertheless, its efficiency can be improved for clinical routine applications. In this paper, we present the CUBMC code, a GPU-based Mc photon transport algorithm for dose calculation under the Compute Unified Device Architecture platform. The simulation of physical events is based on the algorithm used in Penelope, and the cross section table used is the one generated by the Material routine, als present in Penelope code. Photons are transported in voxel-based geometries with different compositions. To demonstrate the capabilities of the algorithm developed in the present work four 128 x 128 x 128 voxel phantoms have been considered. One of them is composed by a homogeneous water-based media, the second is composed by bone, the third is composed by lung and the fourth is composed by a heterogeneous bone and vacuum geometry. Simulations were done considering a 6 MeV monoenergetic photon point source. There are two distinct approaches that were used for transport simulation. The first of them forces the photon to stop at every voxel frontier, the second one is the Woodcock method, where the photon stop in the frontier will be considered depending on the material changing across the photon travel line. Dose calculations using these methods are compared for validation with Penelope and MCNP5 codes. Speed-up factors are compared using a NVidia GTX 560-Ti GPU card against a 2.27 GHz Intel Xeon CPU processor. (Author)

  6. MicroCT-Based Skeletal Models for Use in Tomographic Voxel Phantoms for Radiological Protection

    Energy Technology Data Exchange (ETDEWEB)

    Bolch, Wesley [Univ. of Florida, Gainesville, FL (United States)

    2010-03-30

    The University of Florida (UF) proposes to develop two high-resolution image-based skeletal dosimetry models for direct use by ICRP Committee 2’s Task Group on Dose Calculation in their forthcoming Reference Voxel Male (RVM) and Reference Voxel Female (RVF) whole-body dosimetry phantoms. These two phantoms are CT-based, and thus do not have the image resolution to delineate and perform radiation transport modeling of the individual marrow cavities and bone trabeculae throughout their skeletal structures. Furthermore, new and innovative 3D microimaging techniques will now be required for the skeletal tissues following Committee 2’s revision of the target tissues of relevance for radiogenic bone cancer induction. This target tissue had been defined in ICRP Publication 30 as a 10-μm cell layer on all bone surfaces of trabecular and cortical bone. The revised target tissue is now a 50-μm layer within the marrow cavities of trabecular bone only and is exclusive of the marrow adipocytes. Clearly, this new definition requires the use of 3D microimages of the trabecular architecture not available from past 2D optical studies of the adult skeleton. With our recent acquisition of two relatively young cadavers (males of age 18-years and 40-years), we will develop a series of reference skeletal models that can be directly applied to (1) the new ICRP reference voxel man and female phantoms developed for the ICRP, and (2) pediatric phantoms developed to target the ICRP reference children. Dosimetry data to be developed will include absorbed fractions for internal beta and alpha-particle sources, as well as photon and neutron fluence-to-dose response functions for direct use in external dosimetry studies of the ICRP reference workers and members of the general public

  7. Diffuse Decreased Gray Matter in Patients with Idiopathic Craniocervical Dystonia: a Voxel-Based Morphometry Study

    Directory of Open Access Journals (Sweden)

    Camila Callegari Piccinin

    2015-01-01

    Full Text Available Background: Recent studies have addressed the role of structures other than the basal ganglia in the pathophysiology of craniocervical dystonia. Neuroimaging studies have attempted to identify structural abnormalities in craniocervical dystonia but a clear pattern of alteration has not been established. We performed whole brain evaluation using voxel-based morphometry to identify patterns of gray matter changes in craniocervical dystonia.Methods: We compared 27 patients with craniocervical dystonia matched in age and gender to 54 healthy controls. Voxel-based morphometry was used to compare gray matter volumes. We created a two-sample t-test corrected for subjects’ age and we tested with a level of significance of p<0.001 and false discovery rate correction (p<0.05. Results: Voxel-based morphometry demonstrated significant reductions of gray matter using p<0.001 in the cerebellar vermis IV/V, bilaterally in the superior frontal gyrus, precuneus, anterior cingulate and paracingulate, insular cortex, lingual gyrus and calcarine fissure; in the left hemisphere in the supplemementary motor area (SMA, inferior frontal gyrus, inferior parietal gyrus, temporal pole, supramarginal gyrus, rolandic operculum , hippocampus, middle occipital gyrus, cerebellar lobules IV/V, superior and middle temporal gyri; in the right hemisphere, the middle cingulate and precentral gyrus. Our study did not report any significant result using the false discovery rate correction. We also detected correlations between gray matter volume and age, disease duration, duration of botulinum toxin treatment and the Marsden-Fahn dystonia scale scores.Conclusions: We detected large clusters of gray matter changes chiefly in structures primarily involved in sensorimotor integration, motor planning, visuospatial function and emotional processing.

  8. DIRECT VOXEL-PROJECTION FOR VOLUMETRIC DATA RENDERING IN MEDICAL IMAGERY

    Institute of Scientific and Technical Information of China (English)

    吕忆松; 陈亚珠; 郭玉红

    2002-01-01

    The volumetric rendering of 3-D medical image data is very effective method for communication about radiological studies to clinicians. Algorithms that produce images with artifacts and inaccuracies are not clinically useful. This paper proposed a direct voxel-projection algorithm to implement volumetric data rendering. Using this algorithm, arbitrary volume rotation, transparent and cutaway views are generated satisfactorily. Compared with the existing raytracing methods, it improves the projection image quality greatly. Some experimental results about real medical CT image data demonstrate the advantages and fidelity of the proposed algorithm.

  9. A voxel-based multiscale model to simulate the radiation response of hypoxic tumors

    Energy Technology Data Exchange (ETDEWEB)

    Espinoza, I., E-mail: iespinoza@fis.puc.cl [Institute of Physics, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile and Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg 69120 (Germany); Peschke, P. [Clinical Cooperation Unit Molecular Radiooncology, German Cancer Research Center (DKFZ), Heidelberg 69120 (Germany); Karger, C. P. [Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg 69120 (Germany)

    2015-01-15

    Purpose: In radiotherapy, it is important to predict the response of tumors to irradiation prior to the treatment. This is especially important for hypoxic tumors, which are known to be highly radioresistant. Mathematical modeling based on the dose distribution, biological parameters, and medical images may help to improve this prediction and to optimize the treatment plan. Methods: A voxel-based multiscale tumor response model for simulating the radiation response of hypoxic tumors was developed. It considers viable and dead tumor cells, capillary and normal cells, as well as the most relevant biological processes such as (i) proliferation of tumor cells, (ii) hypoxia-induced angiogenesis, (iii) spatial exchange of cells leading to tumor growth, (iv) oxygen-dependent cell survival after irradiation, (v) resorption of dead cells, and (vi) spatial exchange of cells leading to tumor shrinkage. Oxygenation is described on a microscopic scale using a previously published tumor oxygenation model, which calculates the oxygen distribution for each voxel using the vascular fraction as the most important input parameter. To demonstrate the capabilities of the model, the dependence of the oxygen distribution on tumor growth and radiation-induced shrinkage is investigated. In addition, the impact of three different reoxygenation processes is compared and tumor control probability (TCP) curves for a squamous cells carcinoma of the head and neck (HNSSC) are simulated under normoxic and hypoxic conditions. Results: The model describes the spatiotemporal behavior of the tumor on three different scales: (i) on the macroscopic scale, it describes tumor growth and shrinkage during radiation treatment, (ii) on a mesoscopic scale, it provides the cell density and vascular fraction for each voxel, and (iii) on the microscopic scale, the oxygen distribution may be obtained in terms of oxygen histograms. With increasing tumor size, the simulated tumors develop a hypoxic core. Within the

  10. Reference dosimetry calculations for neutron capture therapy with comparison of analytical and voxel models.

    Science.gov (United States)

    Goorley, J T; Kiger, W S; Zamenhof, R G

    2002-02-01

    As clinical trials of Neutron Capture Therapy (NCT) are initiated in the U.S. and other countries, new treatment planning codes are being developed to calculate detailed dose distributions in patient-specific models. The thorough evaluation and comparison of treatment planning codes is a critical step toward the eventual standardization of dosimetry, which, in turn, is an essential element for the rational comparison of clinical results from different institutions. In this paper we report development of a reference suite of computational test problems for NCT dosimetry and discuss common issues encountered in these calculations to facilitate quantitative evaluations and comparisons of NCT treatment planning codes. Specifically, detailed depth-kerma rate curves were calculated using the Monte Carlo radiation transport code MCNP4B for four different representations of the modified Snyder head phantom, an analytic, multishell, ellipsoidal model, and voxel representations of this model with cubic voxel sizes of 16, 8, and 4 mm. Monoenergetic and monodirectional beams of 0.0253 eV, 1, 2, 10, 100, and 1000 keV neutrons, and 0.2, 0.5, 1, 2, 5, and 10 MeV photons were individually simulated to calculate kerma rates to a statistical uncertainty of neutron beam with a broad neutron spectrum, similar to epithermal beams currently used or proposed for NCT clinical trials, was computed for all models. The thermal neutron, fast neutron, and photon kerma rates calculated with the 4 and 8 mm voxel models were within 2% and 4%, respectively, of those calculated for the analytical model. The 16 mm voxel model produced unacceptably large discrepancies for all dose components. The effects from different kerma data sets and tissue compositions were evaluated. Updating the kerma data from ICRU 46 to ICRU 63 data produced less than 2% difference in kerma rate profiles. The depth-dose profile data, Monte Carlo code input, kerma factors, and model construction files are available

  11. Mercury CEM Calibration

    Energy Technology Data Exchange (ETDEWEB)

    John Schabron; Joseph Rovani; Mark Sanderson

    2008-02-29

    Mercury continuous emissions monitoring systems (CEMS) are being implemented in over 800 coal-fired power plant stacks. The power industry desires to conduct at least a full year of monitoring before the formal monitoring and reporting requirement begins on January 1, 2009. It is important for the industry to have available reliable, turnkey equipment from CEM vendors. Western Research Institute (WRI) is working closely with the Electric Power Research Institute (EPRI), the National Institute of Standards and Technology (NIST), and the Environmental Protection Agency (EPA) to facilitate the development of the experimental criteria for a NIST traceability protocol for dynamic elemental mercury vapor generators. The generators are used to calibrate mercury CEMs at power plant sites. The Clean Air Mercury Rule (CAMR) which was published in the Federal Register on May 18, 2005 requires that calibration be performed with NIST-traceable standards (Federal Register 2007). Traceability procedures will be defined by EPA. An initial draft traceability protocol was issued by EPA in May 2007 for comment. In August 2007, EPA issued an interim traceability protocol for elemental mercury generators (EPA 2007). The protocol is based on the actual analysis of the output of each calibration unit at several concentration levels ranging initially from about 2-40 {micro}g/m{sup 3} elemental mercury, and in the future down to 0.2 {micro}g/m{sup 3}, and this analysis will be directly traceable to analyses by NIST. The document is divided into two separate sections. The first deals with the qualification of generators by the vendors for use in mercury CEM calibration. The second describes the procedure that the vendors must use to certify the generator models that meet the qualification specifications. The NIST traceable certification is performance based, traceable to analysis using isotope dilution inductively coupled plasma/mass spectrometry performed by NIST in Gaithersburg, MD. The

  12. CALIBRATED HYDRODYNAMIC MODEL

    Directory of Open Access Journals (Sweden)

    Sezar Gülbaz

    2015-01-01

    Full Text Available The land development and increase in urbanization in a watershed affect water quantityand water quality. On one hand, urbanization provokes the adjustment of geomorphicstructure of the streams, ultimately raises peak flow rate which causes flood; on theother hand, it diminishes water quality which results in an increase in Total SuspendedSolid (TSS. Consequently, sediment accumulation in downstream of urban areas isobserved which is not preferred for longer life of dams. In order to overcome thesediment accumulation problem in dams, the amount of TSS in streams and inwatersheds should be taken under control. Low Impact Development (LID is a BestManagement Practice (BMP which may be used for this purpose. It is a land planningand engineering design method which is applied in managing storm water runoff inorder to reduce flooding as well as simultaneously improve water quality. LID includestechniques to predict suspended solid loads in surface runoff generated over imperviousurban surfaces. In this study, the impact of LID-BMPs on surface runoff and TSS isinvestigated by employing a calibrated hydrodynamic model for Sazlidere Watershedwhich is located in Istanbul, Turkey. For this purpose, a calibrated hydrodynamicmodel was developed by using Environmental Protection Agency Storm WaterManagement Model (EPA SWMM. For model calibration and validation, we set up arain gauge and a flow meter into the field and obtain rainfall and flow rate data. Andthen, we select several LID types such as retention basins, vegetative swales andpermeable pavement and we obtain their influence on peak flow rate and pollutantbuildup and washoff for TSS. Consequently, we observe the possible effects ofLID on surface runoff and TSS in Sazlidere Watershed.

  13. ALTEA: The instrument calibration

    Energy Technology Data Exchange (ETDEWEB)

    Zaconte, V. [INFN and University of Rome Tor Vergata, Department of Physics, Via della Ricerca Scientifica 1, 00133 Rome (Italy)], E-mail: livio.narici@roma2.infn.it; Belli, F.; Bidoli, V.; Casolino, M.; Di Fino, L.; Narici, L.; Picozza, P.; Rinaldi, A. [INFN and University of Rome Tor Vergata, Department of Physics, Via della Ricerca Scientifica 1, 00133 Rome (Italy); Sannita, W.G. [DISM, University of Genova, Genova (Italy); Department of Psychiatry, SUNY, Stoony Brook, NY (United States); Finetti, N.; Nurzia, G.; Rantucci, E.; Scrimaglio, R.; Segreto, E. [Department of Physics, University and INFN, L' Aquila (Italy); Schardt, D. [GSI/Biophysik, Darmstadt (Germany)

    2008-05-15

    The ALTEA program is an international and multi-disciplinary project aimed at studying particle radiation in space environment and its effects on astronauts' brain functions, as the anomalous perception of light flashes first reported during Apollo missions. The ALTEA space facility includes a 6-silicon telescopes particle detector, and is onboard the International Space Station (ISS) since July 2006. In this paper, the detector calibration at the heavy-ion synchrotron SIS18 at GSI Darmstadt will be presented and compared to the Geant 3 Monte Carlo simulation. Finally, the results of a neural network analysis that was used for ion discrimination on fragmentation data will also be presented.

  14. Dynamic Torque Calibration Unit

    Science.gov (United States)

    Agronin, Michael L.; Marchetto, Carl A.

    1989-01-01

    Proposed dynamic torque calibration unit (DTCU) measures torque in rotary actuator components such as motors, bearings, gear trains, and flex couplings. Unique because designed specifically for testing components under low rates. Measures torque in device under test during controlled steady rotation or oscillation. Rotor oriented vertically, supported by upper angular-contact bearing and lower radial-contact bearing that floats axially to prevent thermal expansion from loading bearings. High-load capacity air bearing available to replace ball bearings when higher load capacity or reduction in rate noise required.

  15. A 12-step user guide for analyzing voxel-wise gray matter asymmetries in statistical parametric mapping (SPM).

    Science.gov (United States)

    Kurth, Florian; Gaser, Christian; Luders, Eileen

    2015-02-01

    Voxel-based morphometry (VBM) has been proven capable of capturing cerebral gray matter asymmetries with a high (voxel-wise) regional specificity. However, a standardized reference on how to conduct voxel-wise asymmetry analyses is missing. This protocol provides the scientific community with a carefully developed guide describing, in 12 distinct steps, how to take structural images from data pre-processing, via statistical analysis, to the final interpretation of the significance maps. Key adaptations compared with the standard VBM workflow involve establishing a voxel-wise hemispheric correspondence, capturing the direction and degree of asymmetry and preventing a blurring of information across hemispheres. The workflow incorporates the most recent methodological developments, including high-dimensional spatial normalization and partial volume estimations. Although the protocol is primarily designed to enable relatively inexperienced users to conduct a voxel-based asymmetry analysis on their own, it may also be useful to experienced users who wish to efficiently adapt their existing scripts or pipelines.

  16. 3D-Ultrasound probe calibration for computer-guided diagnosis and therapy

    CERN Document Server

    Baumann, Michael; Leroy, Antoine; Troccaz, Jocelyne

    2008-01-01

    With the emergence of swept-volume ultrasound (US) probes, precise and almost real-time US volume imaging has become available. This offers many new opportunities for computer guided diagnosis and therapy, 3-D images containing significantly more information than 2-D slices. However, computer guidance often requires knowledge about the exact position of US voxels relative to a tracking reference, which can only be achieved through probe calibration. In this paper we present a 3-D US probe calibration system based on a membrane phantom. The calibration matrix is retrieved by detection of a membrane plane in a dozen of US acquisitions of the phantom. Plane detection is robustly performed with the 2-D Hough transformation. The feature extraction process is fully automated, calibration requires about 20 minutes and the calibration system can be used in a clinical context. The precision of the system was evaluated to a root mean square (RMS) distance error of 1.15mm and to an RMS angular error of 0.61 degrees. The...

  17. Calibration of a radioactive ink-based stack phantom and its applications in nuclear medicine.

    Science.gov (United States)

    El-Ali, H; Ljungberg, M; Strand, S-E; Palmer, J; Malmgren, L; Nilsson, J

    2003-04-01

    This paper describes a stack phantom useful for imaging complex activity distributions. It is based on images printed with radioactive ink using a commercial ink-jet printer. The application for the phantom is in the evaluation of planar and SPECT scintillation camera images and for validation of Monte Carlo simulated images. The accuracy in generating the activity distributions on paper sheets is especially important. Here we describe the calibration procedure for the ink-jet printer. The goal of the printer calibration is to find the relationship between the digital image count (voxel grey level) and its corresponding activity on the paper sheets (radioactivity). The relationship between the voxel grey level and the radioactivity on the paper sheets (measured by scanning technique and well counter) was found to be logarithmic, and a 3rd degree polynomial was found to fit the relationship. The distribution of radioactivity in the ink cartridge was investigated by pinhole SPECT. The distribution of (99m)Tc solution was found to be homogeneous in the ink solution. Experimental studies were done directly on Monte Carlo simulated heart images from the NCAT phantom. The result showed that the simulated images are similar to the images measured using the ink-jet technique. This stack phantom could be a promising solution with an advantage that the exact geometry generated in Monte Carlo could be imitated in the phantom. The phantom is a very flexible device and clearly much more versatile than conventional phantoms which have a fixed geometry and spatial limitation.

  18. A Simple Accelerometer Calibrator

    Science.gov (United States)

    Salam, R. A.; Islamy, M. R. F.; Munir, M. M.; Latief, H.; Irsyam, M.; Khairurrijal

    2016-08-01

    High possibility of earthquake could lead to the high number of victims caused by it. It also can cause other hazards such as tsunami, landslide, etc. In that case it requires a system that can examine the earthquake occurrence. Some possible system to detect earthquake is by creating a vibration sensor system using accelerometer. However, the output of the system is usually put in the form of acceleration data. Therefore, a calibrator system for accelerometer to sense the vibration is needed. In this study, a simple accelerometer calibrator has been developed using 12 V DC motor, optocoupler, Liquid Crystal Display (LCD) and AVR 328 microcontroller as controller system. The system uses the Pulse Wave Modulation (PWM) form microcontroller to control the motor rotational speed as response to vibration frequency. The frequency of vibration was read by optocoupler and then those data was used as feedback to the system. The results show that the systems could control the rotational speed and the vibration frequencies in accordance with the defined PWM.

  19. Voxel-based MRI intensitometry reveals extent of cerebral white matter pathology in amyotrophic lateral sclerosis.

    Directory of Open Access Journals (Sweden)

    Viktor Hartung

    Full Text Available Amyotrophic lateral sclerosis (ALS is characterized by progressive loss of upper and lower motor neurons. Advanced MRI techniques such as diffusion tensor imaging have shown great potential in capturing a common white matter pathology. However the sensitivity is variable and diffusion tensor imaging is not yet applicable to the routine clinical environment. Voxel-based morphometry (VBM has revealed grey matter changes in ALS, but the bias-reducing algorithms inherent to traditional VBM are not optimized for the assessment of the white matter changes. We have developed a novel approach to white matter analysis, namely voxel-based intensitometry (VBI. High resolution T1-weighted MRI was acquired at 1.5 Tesla in 30 ALS patients and 37 age-matched healthy controls. VBI analysis at the group level revealed widespread white matter intensity increases in the corticospinal tracts, corpus callosum, sub-central, frontal and occipital white matter tracts and cerebellum. VBI results correlated with disease severity (ALSFRS-R and patterns of cerebral involvement differed between bulbar- and limb-onset. VBI would be easily translatable to the routine clinical environment, and once optimized for individual analysis offers significant biomarker potential in ALS.

  20. Dose conversion coefficients for Chinese reference adult male and female voxel phantoms from idealized neutron exposures

    CERN Document Server

    Liu, Huan; Qiu, Rui; Yang, Yue; Pan, Yu-Xi; Liu, Li-Ye

    2015-01-01

    A new set of fluence-to-dose conversion coefficients based on the Chinese reference adult voxel phantoms CRAM and CRAF are presented for six idealized external neutron exposures from 10-8 MeV to 20 MeV. The voxel phantoms CRAM and CRAF were adjusted from the previous phantoms CNMAN and CNWM respectively, and the masses of individual organs have been adjusted to the Chinese reference data. The calculation of organ-absorbed doses and effective doses were performed with the Monte Carlo transport code MCNPX. The resulting dose conversion coefficients were compared with those published in ICRP Publication 116, which represents the reference Caucasian. The organ-absorbed dose conversion coefficients of most organs are in good agreement with the results in ICRP Publication 116, however, obvious discrepancies are observed for some organs and certain geometries. For neutrons with energies above 2 MeV, the effective dose conversion coefficients of Chinese reference adult are almost identical to those of ICRP Publicatio...

  1. Absorbed dose evaluation based on a computational voxel model incorporating distinct cerebral structures

    Energy Technology Data Exchange (ETDEWEB)

    Brandao, Samia de Freitas; Trindade, Bruno; Campos, Tarcisio P.R. [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil)]. E-mail: samiabrandao@gmail.com; bmtrindade@yahoo.com; campos@nuclear.ufmg.br

    2007-07-01

    Brain tumors are quite difficult to treat due to the collateral radiation damages produced on the patients. Despite of the improvements in the therapeutics protocols for this kind of tumor, involving surgery and radiotherapy, the failure rate is still extremely high. This fact occurs because tumors can not often be totally removed by surgery since it may produce some type of deficit in the cerebral functions. Radiotherapy is applied after the surgery, and both are palliative treatments. During radiotherapy the brain does not absorb the radiation dose in homogeneous way, because the various density and chemical composition of tissues involved. With the intention of evaluating better the harmful effects caused by radiotherapy it was developed an elaborated cerebral voxel model to be used in computational simulation of the irradiation protocols of brain tumors. This paper presents some structures function of the central nervous system and a detailed cerebral voxel model, created in the SISCODES program, considering meninges, cortex, gray matter, white matter, corpus callosum, limbic system, ventricles, hypophysis, cerebellum, brain stem and spinal cord. The irradiation protocol simulation was running in the MCNP5 code. The model was irradiated with photons beam whose spectrum simulates a linear accelerator of 6 MV. The dosimetric results were exported to SISCODES, which generated the isodose curves for the protocol. The percentage isodose curves in the brain are present in this paper. (author)

  2. The brain structure correlates of individual differences in trait mindfulness: a voxel-based morphometry study.

    Science.gov (United States)

    Lu, H; Song, Y; Xu, M; Wang, X; Li, X; Liu, J

    2014-07-11

    Mindfulness is the state of being attentive to and aware of what is taking place in the present, which is beneficial for reducing stress-related symptoms and improving mental and physical health. Previous studies have demonstrated that meditation practice can improve individuals' mindfulness through modifying functions and structures of multiple brain regions, including the anterior cingulate cortex (ACC), insula, fronto-limbic network, posterior cingulate cortex (PCC), and temporal-parietal junction. However, little is known about the neuroanatomical correlates of trait mindfulness. In the current study, we used voxel-based morphometry to investigate the neural correlates of individual differences in trait mindfulness by correlating the gray matter (GM) volume of each voxel across the whole brain with trait mindfulness measured by the Mindful Attention Awareness Scale in a large sample of young adults (N=247). We found that individuals who were more mindful of the present had greater GM volume in the right hippocampus/amygdala and bilateral ACC, but less GM volume in bilateral PCC and the left orbitofrontal cortex. These results suggest that trait mindfulness is associated with brain regions involved in executive attention, emotion regulation, and self-referential processing, through which mindfulness may exert its beneficial effects on psychological and physical well-being.

  3. Regional White Matter Decreases in Alzheimer's Disease Using Optimized Voxel-Based Morphometry

    Energy Technology Data Exchange (ETDEWEB)

    Shuyu Li; Fang Pu; Feng Shi; Sheng Xie; Yinhua Wang; Tianzi Jiang (Dept. of Bioengineering, Beijing Univ. of Aeronautics and Astronautics, Beijing (China))

    2008-02-15

    Background: Most studies that attempt to clarify structural abnormalities related to functional disconnection in patients with Alzheimer's disease (AD) have focused on exploring pathological changes in cortical gray matter. However, white matter fibers connecting these cerebral areas may also be abnormal. Purpose: To investigate the regional changes of white matter volume in patients with AD compared to healthy subjects. Material and Methods: White matter volume changes in whole-brain magnetic resonance images acquired from 19 patients with AD and 20 healthy subjects (control group) were observed using the optimized voxel-based morphometry (VBM) method. In addition, the corpus callosum (CC) of AD patients and the control group was investigated further by outlining manually the boundary of the CC on a midsagittal slice. Each area of the CC was then corrected by dividing each subject's intracranial area in the midsagittal plane. Results: Compared with the control group, AD patients showed significantly reduced white matter volumes in the posterior part of the CC and the temporal lobe in the left and right hemispheres. Moreover, the voxel showing peak statistical difference in the posterior of the CC was left sided. The five subdivisions of the CC were also significantly smaller among the AD patients relative to the control group. Conclusion: Our findings suggest that these abnormalities in white matter regions may contribute to the functional disconnections in AD

  4. Regional White Matter Decreases in Alzheimer's Disease Using Optimized Voxel-Based Morphometry

    Energy Technology Data Exchange (ETDEWEB)

    Shuyu Li; Fang Pu; Feng Shi; Sheng Xie; Yinhua Wang; Tianzi Jiang [Dept. of Bioengineering, Beijing Univ. of Aeronautics and Astronautics, Beijing (China)

    2008-02-15

    Background: Most studies that attempt to clarify structural abnormalities related to functional disconnection in patients with Alzheimer's disease (AD) have focused on exploring pathological changes in cortical gray matter. However, white matter fibers connecting these cerebral areas may also be abnormal. Purpose: To investigate the regional changes of white matter volume in patients with AD compared to healthy subjects. Material and Methods: White matter volume changes in whole-brain magnetic resonance images acquired from 19 patients with AD and 20 healthy subjects (control group) were observed using the optimized voxel-based morphometry (VBM) method. In addition, the corpus callosum (CC) of AD patients and the control group was investigated further by outlining manually the boundary of the CC on a midsagittal slice. Each area of the CC was then corrected by dividing each subject's intracranial area in the midsagittal plane. Results: Compared with the control group, AD patients showed significantly reduced white matter volumes in the posterior part of the CC and the temporal lobe in the left and right hemispheres. Moreover, the voxel showing peak statistical difference in the posterior of the CC was left sided. The five subdivisions of the CC were also significantly smaller among the AD patients relative to the control group. Conclusion: Our findings suggest that these abnormalities in white matter regions may contribute to the functional disconnections in AD.

  5. Regional gray matter abnormalities in patients with schizophrenia determined with optimized voxel-based morphometry

    Science.gov (United States)

    Guo, XiaoJuan; Yao, Li; Jin, Zhen; Chen, Kewei

    2006-03-01

    This study examined regional gray matter abnormalities across the whole brain in 19 patients with schizophrenia (12 males and 7 females), comparing with 11 normal volunteers (7 males and 4 females). The customized brain templates were created in order to improve spatial normalization and segmentation. Then automated preprocessing of magnetic resonance imaging (MRI) data was conducted using optimized voxel-based morphometry (VBM). The statistical voxel based analysis was implemented in terms of two-sample t-test model. Compared with normal controls, regional gray matter concentration in patients with schizophrenia was significantly reduced in the bilateral superior temporal gyrus, bilateral middle frontal and inferior frontal gyrus, right insula, precentral and parahippocampal areas, left thalamus and hypothalamus as well as, however, significant increases in gray matter concentration were not observed across the whole brain in the patients. This study confirms and extends some earlier findings on gray matter abnormalities in schizophrenic patients. Previous behavior and fMRI researches on schizophrenia have suggested that cognitive capacity decreased and self-conscious weakened in schizophrenic patients. These regional gray matter abnormalities determined through structural MRI with optimized VBM may be potential anatomic underpinnings of schizophrenia.

  6. Automated Voxel Model from Point Clouds for Structural Analysis of Cultural Heritage

    Science.gov (United States)

    Bitelli, G.; Castellazzi, G.; D'Altri, A. M.; De Miranda, S.; Lambertini, A.; Selvaggi, I.

    2016-06-01

    In the context of cultural heritage, an accurate and comprehensive digital survey of a historical building is today essential in order to measure its geometry in detail for documentation or restoration purposes, for supporting special studies regarding materials and constructive characteristics, and finally for structural analysis. Some proven geomatic techniques, such as photogrammetry and terrestrial laser scanning, are increasingly used to survey buildings with different complexity and dimensions; one typical product is in form of point clouds. We developed a semi-automatic procedure to convert point clouds, acquired from laserscan or digital photogrammetry, to a filled volume model of the whole structure. The filled volume model, in a voxel format, can be useful for further analysis and also for the generation of a Finite Element Model (FEM) of the surveyed building. In this paper a new approach is presented with the aim to decrease operator intervention in the workflow and obtain a better description of the structure. In order to achieve this result a voxel model with variable resolution is produced. Different parameters are compared and different steps of the procedure are tested and validated in the case study of the North tower of the San Felice sul Panaro Fortress, a monumental historical building located in San Felice sul Panaro (Modena, Italy) that was hit by an earthquake in 2012.

  7. Spatial indices for measuring three-dimensional patterns in a voxel-based space

    Science.gov (United States)

    Jjumba, Anthony; Dragićević, Suzana

    2016-07-01

    Spatial indices are used to quantitatively describe the spatial arrangements of the features within a study region. However, most of the indices used are two-dimensional in their representation of the surface characteristics, and this is insufficient to quantify the three-dimensional properties of an area or geospatial features. With the increased availability of 3D data from laser scanning and other collection methods, a voxel-based representation of space is an important methodology that allows for an intuitive visualization of geospatial features and their analysis with 3D GIS techniques. The objective of this study is to conceptualize, develop, and implement indices that can characterize three-dimensional space and can be used to analyze the structure of spatial features in a landscape. The indices for three-dimensional space that are implemented are, namely, surface area volume, fractal dimension, lacunarity, and Moran's I which are all useful in the quantification of spatial organization found in ecological landscapes. In addition to providing the quantitative descriptors, the results indicate that a voxel-based representation provides a straightforward means of characterizing the form and composition of the spatial features using 3D indices.

  8. Multi-voxel pattern analysis of noun and verb differences in ventral temporal cortex.

    Science.gov (United States)

    Boylan, Christine; Trueswell, John C; Thompson-Schill, Sharon L

    2014-10-01

    Recent evidence suggests a probabilistic relationship exists between the phonological/orthographic form of a word and its lexical-syntactic category (specifically nouns vs. verbs) such that syntactic prediction may elicit form-based estimates in sensory cortex. We tested this hypothesis by conducting multi-voxel pattern analysis (MVPA) of fMRI data from early visual cortex (EVC), left ventral temporal (VT) cortex, and a subregion of the latter - the left mid fusiform gyrus (mid FG), sometimes called the "visual word form area." Crucially, we examined only those volumes sampled when subjects were predicting, but not viewing, nouns and verbs. This allowed us to investigate prediction effects in visual areas without any bottom-up orthographic input. We found that voxels in VT and mid FG, but not in EVC, were able to classify noun-predictive trials vs. verb-predictive trials in sentence contexts, suggesting that sentence-level predictions are sufficient to generate word form-based estimates in visual areas.

  9. Traceable calibration of impedance heads and artificial mastoids

    Science.gov (United States)

    Scott, D. A.; Dickinson, L. P.; Bell, T. J.

    2015-12-01

    Artificial mastoids are devices which simulate the mechanical characteristics of the human head, and in particular of the bony structure behind the ear. They are an essential tool in the calibration of bone-conduction hearing aids and audiometers. With the emergence of different types of artificial mastoids in the market, and the realisation that the visco-elastic part of these instruments changes over time, the development of a method of traceable calibration of these devices without relying on commercial software has become important for national metrology institutes. This paper describes commercially available calibration methods, and the development of a traceable calibration method including the traceable calibration of the impedance head used to measure the mechanical impedance of the artificial mastoid.

  10. Sensitivity study of voxel-based PET image comparison to image registration algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Yip, Stephen, E-mail: syip@lroc.harvard.edu; Chen, Aileen B.; Berbeco, Ross [Department of Radiation Oncology, Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115 (United States); Aerts, Hugo J. W. L. [Department of Radiation Oncology, Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115 and Department of Radiology, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts 02115 (United States)

    2014-11-01

    Purpose: Accurate deformable registration is essential for voxel-based comparison of sequential positron emission tomography (PET) images for proper adaptation of treatment plan and treatment response assessment. The comparison may be sensitive to the method of deformable registration as the optimal algorithm is unknown. This study investigated the impact of registration algorithm choice on therapy response evaluation. Methods: Sixteen patients with 20 lung tumors underwent a pre- and post-treatment computed tomography (CT) and 4D FDG-PET scans before and after chemoradiotherapy. All CT images were coregistered using a rigid and ten deformable registration algorithms. The resulting transformations were then applied to the respective PET images. Moreover, the tumor region defined by a physician on the registered PET images was classified into progressor, stable-disease, and responder subvolumes. Particularly, voxels with standardized uptake value (SUV) decreases >30% were classified as responder, while voxels with SUV increases >30% were progressor. All other voxels were considered stable-disease. The agreement of the subvolumes resulting from difference registration algorithms was assessed by Dice similarity index (DSI). Coefficient of variation (CV) was computed to assess variability of DSI between individual tumors. Root mean square difference (RMS{sub rigid}) of the rigidly registered CT images was used to measure the degree of tumor deformation. RMS{sub rigid} and DSI were correlated by Spearman correlation coefficient (R) to investigate the effect of tumor deformation on DSI. Results: Median DSI{sub rigid} was found to be 72%, 66%, and 80%, for progressor, stable-disease, and responder, respectively. Median DSI{sub deformable} was 63%–84%, 65%–81%, and 82%–89%. Variability of DSI was substantial and similar for both rigid and deformable algorithms with CV > 10% for all subvolumes. Tumor deformation had moderate to significant impact on DSI for progressor

  11. Using three-dimensional discrete spherical Fourier descriptors based on surface curvature voxels for pollen particle recognition

    Institute of Scientific and Technical Information of China (English)

    Xie Yong-Hua; Michael OhEigeartaigh

    2010-01-01

    This paper presents a new method for extract three-dimensional (3D) discrete spherical Fourier descriptors based on surface curvature voxeis for pollen particle recognition.In order to reduce the high amount of pollen information and noise disturbance,the geometric normalized curvature voxels with the principal curvedness are first extracted to represent the intrinsic pollen volumetric data.Then the curvature voxels are decomposed into radial and angular components with spherical harmonic transform in spherical coordinates.Finally the 3D discrete Fourier transform is applied to the decomposed curvature voxels to obtain the 3D spherical Fourier descriptors for pollen recognition.Experimental results show that the presented descriptors are invariant to different pollen particle geometric transformations,such as pose change and spatial rotation,and can obtain high recognition accuracy and speed simultaneously.

  12. Internal Water Vapor Photoacoustic Calibration

    Science.gov (United States)

    Pilgrim, Jeffrey S.

    2009-01-01

    Water vapor absorption is ubiquitous in the infrared wavelength range where photoacoustic trace gas detectors operate. This technique allows for discontinuous wavelength tuning by temperature-jumping a laser diode from one range to another within a time span suitable for photoacoustic calibration. The use of an internal calibration eliminates the need for external calibrated reference gases. Commercial applications include an improvement of photoacoustic spectrometers in all fields of use.

  13. VERTICAL VEGETATION STRUCTURE ANALYSIS AND HYDRAULIC ROUGHNESS DETERMINATION USING DENSE ALS POINT CLOUD DATA - A VOXEL BASED APPROACH

    Directory of Open Access Journals (Sweden)

    M. Vetter

    2012-09-01

    Full Text Available In this contribution the complexity of the vertical vegetation structure, based on dense airborne laser scanning (ALS point cloud data (25 echoes/m2 , is analyzed to calculate vegetation roughness for hydraulic applications. Using the original 3D ALS point cloud, three levels of abstractions are derived (cells, voxels and connections to analyze ALS data based on a 1×1 m2 raster over the whole data set. A voxel structure is used to count the echoes in predefined detrended height levels within each cell. In general, it is assumed that the number of voxels containing echoes is an indicator for elevated objects and consequently for increased roughness. Neighboring voxels containing at least one data point are merged together to connections. An additional height threshold is applied to connect vertical neighboring voxels with a certain distance in between. Thus, the connections indicate continuous vegetation structures. The height of the surface near or lowest connection is an indicator for hydrodynamic roughness coefficients. For cells, voxels and connections the laser echoes are counted within the structure and various statistical measures are calculated. Based on these derived statistical parameters a rule-based classification is developed by applying a decision tree to assess vegetation types. Roughness coefficient values such as Manning's n are estimated, which are used as input for 2D hydrodynamic-numerical modeling. The estimated Manning’s values from the ALS point cloud are compared with a traditional Manning's map. Finally, the effect of these two different Manning's n maps as input on the 2D hydraulics are quantified by calculating a height difference model of the inundated depth maps. The results show the large potential of using the entire vertical vegetation structure for hydraulic roughness estimation.

  14. Field calibration of cup anemometers

    DEFF Research Database (Denmark)

    Kristensen, L.; Jensen, G.; Hansen, A.

    2001-01-01

    An outdoor calibration facility for cup anemometers, where the signals from 10 anemometers of which at least one is a reference can be can be recorded simultaneously, has been established. The results are discussed with special emphasis on the statisticalsignificance of the calibration expressions....... It is concluded that the method has the advantage that many anemometers can be calibrated accurately with a minimum of work and cost. The obvious disadvantage is that the calibration of a set of anemometersmay take more than one month in order to have wind speeds covering a sufficiently large magnitude range...

  15. Radiological Calibration and Standards Facility

    Data.gov (United States)

    Federal Laboratory Consortium — PNNL maintains a state-of-the-art Radiological Calibration and Standards Laboratory on the Hanford Site at Richland, Washington. Laboratory staff provide expertise...

  16. SURF Model Calibration Strategy

    Energy Technology Data Exchange (ETDEWEB)

    Menikoff, Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-10

    SURF and SURFplus are high explosive reactive burn models for shock initiation and propagation of detonation waves. They are engineering models motivated by the ignition & growth concept of high spots and for SURFplus a second slow reaction for the energy release from carbon clustering. A key feature of the SURF model is that there is a partial decoupling between model parameters and detonation properties. This enables reduced sets of independent parameters to be calibrated sequentially for the initiation and propagation regimes. Here we focus on a methodology for tting the initiation parameters to Pop plot data based on 1-D simulations to compute a numerical Pop plot. In addition, the strategy for tting the remaining parameters for the propagation regime and failure diameter is discussed.

  17. RX130 Robot Calibration

    Science.gov (United States)

    Fugal, Mario

    2012-10-01

    In order to create precision magnets for an experiment at Oak Ridge National Laboratory, a new reverse engineering method has been proposed that uses the magnetic scalar potential to solve for the currents necessary to produce the desired field. To make the magnet it is proposed to use a copper coated G10 form, upon which a drill, mounted on a robotic arm, will carve wires. The accuracy required in the manufacturing of the wires exceeds nominal robot capabilities. However, due to the rigidity as well as the precision servo motor and harmonic gear drivers, there are robots capable of meeting this requirement with proper calibration. Improving the accuracy of an RX130 to be within 35 microns (the accuracy necessary of the wires) is the goal of this project. Using feedback from a displacement sensor, or camera and inverse kinematics it is possible to achieve this accuracy.

  18. Calibration of Nanopositioning Stages

    Directory of Open Access Journals (Sweden)

    Ning Tan

    2015-12-01

    Full Text Available Accuracy is one of the most important criteria for the performance evaluation of micro- and nanorobots or systems. Nanopositioning stages are used to achieve the high positioning resolution and accuracy for a wide and growing scope of applications. However, their positioning accuracy and repeatability are not well known and difficult to guarantee, which induces many drawbacks for many applications. For example, in the mechanical characterisation of biological samples, it is difficult to perform several cycles in a repeatable way so as not to induce negative influences on the study. It also prevents one from controlling accurately a tool with respect to a sample without adding additional sensors for closed loop control. This paper aims at quantifying the positioning repeatability and accuracy based on the ISO 9283:1998 standard, and analyzing factors influencing positioning accuracy onto a case study of 1-DoF (Degree-of-Freedom nanopositioning stage. The influence of thermal drift is notably quantified. Performances improvement of the nanopositioning stage are then investigated through robot calibration (i.e., open-loop approach. Two models (static and adaptive models are proposed to compensate for both geometric errors and thermal drift. Validation experiments are conducted over a long period (several days showing that the accuracy of the stage is improved from typical micrometer range to 400 nm using the static model and even down to 100 nm using the adaptive model. In addition, we extend the 1-DoF calibration to multi-DoF with a case study of a 2-DoF nanopositioning robot. Results demonstrate that the model efficiently improved the 2D accuracy from 1400 nm to 200 nm.

  19. Evaluation of a deterministic grid-based Boltzmann solver (GBBS) for voxel-level absorbed dose calculations in nuclear medicine.

    Science.gov (United States)

    Mikell, Justin; Cheenu Kappadath, S; Wareing, Todd; Erwin, William D; Titt, Uwe; Mourtada, Firas

    2016-06-21

    To evaluate the 3D Grid-based Boltzmann Solver (GBBS) code ATTILA (®) for coupled electron and photon transport in the nuclear medicine energy regime for electron (beta, Auger and internal conversion electrons) and photon (gamma, x-ray) sources. Codes rewritten based on ATTILA are used clinically for both high-energy photon teletherapy and (192)Ir sealed source brachytherapy; little information exists for using the GBBS to calculate voxel-level absorbed doses in nuclear medicine. We compared DOSXYZnrc Monte Carlo (MC) with published voxel-S-values to establish MC as truth. GBBS was investigated for mono-energetic 1.0, 0.1, and 0.01 MeV electron and photon sources as well as (131)I and (90)Y radionuclides. We investigated convergence of GBBS by analyzing different meshes ([Formula: see text]), energy group structures ([Formula: see text]) for each radionuclide component, angular quadrature orders ([Formula: see text], and scattering order expansions ([Formula: see text]-[Formula: see text]); higher indices imply finer discretization. We compared GBBS to MC in (1) voxel-S-value geometry for soft tissue, lung, and bone, and (2) a source at the interface between combinations of lung, soft tissue, and bone. Excluding Auger and conversion electrons, MC agreed within  ≈5% of published source voxel absorbed doses. For the finest discretization, most GBBS absorbed doses in the source voxel changed by less than 1% compared to the next finest discretization along each phase space variable indicating sufficient convergence. For the finest discretization, agreement with MC in the source voxel ranged from  -3% to  -20% with larger differences at lower energies (-3% for 1 MeV electron in lung to  -20% for 0.01 MeV photon in bone); similar agreement was found for the interface geometries. Differences between GBBS and MC in the source voxel for (90)Y and (131)I were  -6%. The GBBS ATTILA was benchmarked against MC in the nuclear medicine regime. GBBS can be a

  20. The Relevance Voxel Machine (RVoxM): A Self-Tuning Bayesian Model for Informative Image-Based Prediction

    DEFF Research Database (Denmark)

    Sabuncu, Mert R.; Van Leemput, Koen

    2012-01-01

    This paper presents the relevance voxel machine (RVoxM), a dedicated Bayesian model for making predictions based on medical imaging data. In contrast to the generic machine learning algorithms that have often been used for this purpose, the method is designed to utilize a small number of spatially...... clustered sets of voxels that are particularly suited for clinical interpretation. RVoxM automatically tunes all its free parameters during the training phase, and offers the additional advantage of producing probabilistic prediction outcomes. We demonstrate RVoxM as a regression model by predicting age...

  1. Evaluation of a deterministic grid-based Boltzmann solver (GBBS) for voxel-level absorbed dose calculations in nuclear medicine

    Science.gov (United States)

    Mikell, Justin; Cheenu Kappadath, S.; Wareing, Todd; Erwin, William D.; Titt, Uwe; Mourtada, Firas

    2016-06-01

    To evaluate the 3D Grid-based Boltzmann Solver (GBBS) code ATTILA ® for coupled electron and photon transport in the nuclear medicine energy regime for electron (beta, Auger and internal conversion electrons) and photon (gamma, x-ray) sources. Codes rewritten based on ATTILA are used clinically for both high-energy photon teletherapy and 192Ir sealed source brachytherapy; little information exists for using the GBBS to calculate voxel-level absorbed doses in nuclear medicine. We compared DOSXYZnrc Monte Carlo (MC) with published voxel-S-values to establish MC as truth. GBBS was investigated for mono-energetic 1.0, 0.1, and 0.01 MeV electron and photon sources as well as 131I and 90Y radionuclides. We investigated convergence of GBBS by analyzing different meshes ({{M}0},{{M}1},{{M}2} ), energy group structures ({{E}0},{{E}1},{{E}2} ) for each radionuclide component, angular quadrature orders (≤ft. {{S}4},{{S}8},{{S}16}\\right) , and scattering order expansions ({{P}0} -{{P}6} ); higher indices imply finer discretization. We compared GBBS to MC in (1) voxel-S-value geometry for soft tissue, lung, and bone, and (2) a source at the interface between combinations of lung, soft tissue, and bone. Excluding Auger and conversion electrons, MC agreed within  ≈5% of published source voxel absorbed doses. For the finest discretization, most GBBS absorbed doses in the source voxel changed by less than 1% compared to the next finest discretization along each phase space variable indicating sufficient convergence. For the finest discretization, agreement with MC in the source voxel ranged from  -3% to  -20% with larger differences at lower energies (-3% for 1 MeV electron in lung to  -20% for 0.01 MeV photon in bone); similar agreement was found for the interface geometries. Differences between GBBS and MC in the source voxel for 90Y and 131I were  -6%. The GBBS ATTILA was benchmarked against MC in the nuclear medicine regime. GBBS can be a viable

  2. In vivo quantification of intracerebral GABA by single-voxel {sup 1}H-MRS-How reproducible are the results?

    Energy Technology Data Exchange (ETDEWEB)

    Bogner, W. [MR Centre of Excellence, Department of Radiology, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna (Austria)], E-mail: wolfgang@nmr.at; Gruber, S. [MR Centre of Excellence, Department of Radiology, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna (Austria)], E-mail: stephan@nmr.at; Doelken, M. [Department of Neuroradiology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen (Austria)], E-mail: marc.doelken@uk-erlangen.de; Stadlbauer, A. [Department of Neurosurgery, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen (Austria)], E-mail: andi@nmr.at; Ganslandt, O. [Department of Neurosurgery, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen (Austria)], E-mail: oliver.ganslandt@uk-erlangen.de; Boettcher, U. [Siemens Medical Solution, Karl-Schall Str. 6, D-91052 Erlangen (Germany)], E-mail: uwe.boettcher@siemens.com; Trattnig, S. [MR Centre of Excellence, Department of Radiology, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna (Austria)], E-mail: siegfried.trattnig@meduniwien.ac.at; Doerfler, A. [Department of Neuroradiology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen (Austria)], E-mail: a.doerfler@nrad.imed.uni-erlangen.de; Stefan, H. [Center Epilepsy Erlangen (ZEE), Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen (Germany)], E-mail: Hermann.Stefan@uk-erlangen.de; Hammen, T. [Center Epilepsy Erlangen (ZEE), Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, D-91054 Erlangen (Germany)], E-mail: thilo.hammen@uk-erlangen.de

    2010-03-15

    Gamma aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the human brain. It plays a decisive role in a variety of nervous system disorders, such as anxiety disorders, epilepsy, schizophrenia, insomnia, and many others. The reproducibility of GABA quantification results obtained with a single-voxel spectroscopy J-difference editing sequence with Point Resolved Spectroscopy localization (MEGA-PRESS) was determined on a 3.0 Tesla MR scanner in healthy adults. Eleven volunteers were measured in long- and short-term intervals. Intra- and inter-subject reproducibility were evaluated. Internal referencing of GABA+ to total creatine (tCr) and water (H{sub 2}O), as well as two different post-processing methods for the evaluation (signal integration and time-domain fitting) were compared. In all subjects lower coefficient of variation and therefore higher reproducibility can be observed for fitting compared to integration. The GABA+/tCr ratio performs better than the GABA+/H{sub 2}O ratio or GABA+ without internal referencing for both fitting and integration (GABA+/tCr: 13.3% and 17.0%; GABA+/H{sub 2}O: 15.0% and 17.8%; GABA+: 19.2% and 21.7%). Four-day measurements on three subjects showed higher intra- than inter-subject reproducibility (GABA+/tCr {approx}10-12%). With a coefficient of variation of about 13% for inter-subject and 10-12% for intra-subject variability of GABA+/tCr, this technique seems to be a precise tool that can detect GABA confidently. The results of this study show the reproducibility limitations of GABA quantification in vivo, which are necessary for further clinical studies.

  3. PHOTOMETRYPIPELINE - An Automated Pipeline for Calibrated Photometry

    Science.gov (United States)

    Mommert, Michael; Moskovitz, Nicholas; Trilling, David E.

    2016-10-01

    Telescopes acquire massive amounts of imaging data every night. The goal of a large fraction of these observations is to obtain calibrated photometry for point sources - stars or moving Solar System targets - in different filters.We present PHOTOMETRYPIPELINE (PP, github.com/mommermi/photometrypipeline), an automated pipeline to obtain calibrated photometry from imaging data. PP is an open-source Python 2.7 software suite that provides image registration, aperture photometry, photometric calibration, and target identification with only minimal human interaction. For image registration, PP utilizes Source Extractor (Bertin & Arnouts 1996, A&AS, 117) and SWARP (Bertin et al. 2002, ASP Conf. S., 228) to find a plate solution for each frame, providing accurate target astrometry. Circular aperture photometry is performed using Source Extractor; an optimum aperture radius is identified using a curve-of-growth analysis. Photometric calibration is obtained through matching the background source catalog with star catalogs with reliable photometry (e.g., SDSS, URAT-1) in an iterative process; magnitude zeropoint accuracies are usually of the order of 0.03 mag, or better. Final calibrated photometry for each field source is written into a queriable database; target photometry is extracted from this database. Moving targets are identified using JPL Horizons (Giorgini et al. 1996, BAAS, 28) ephemerides. Image combination capabilities (using SWARP, Bertin 2006, ASP Conf. S., 112) are also available to improve the target's signal.PP is well-suited for data covering a few square arcminutes of the sky due to its dependence on background sources for registration and calibration. PP can be run on Unix-based systems on a simple desktop machine and is capable of realtime data analysis. PP has been developed for observations of moving targets, but can also be used on other observations. Efforts to improve the sky coverage for phometric calibration are in progress. Also, a module will be

  4. Prostate dose calculations for permanent implants using the MCNPX code and the Voxels phantom MAX

    Energy Technology Data Exchange (ETDEWEB)

    Reis Junior, Juraci Passos dos; Silva, Ademir Xavier da, E-mail: jjunior@con.ufrj.b, E-mail: Ademir@con.ufrj.b [Coordenacao dos Programas de Pos-Graduacao de Engenharia (COPPE/UFRJ), RJ (Brazil). Programa de Engenharia Nuclear; Facure, Alessandro N.S., E-mail: facure@cnen.gov.b [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil)

    2010-07-01

    This paper presents the modeling of 80, 88 and 100 of {sup 125}I seeds, punctual and volumetric inserted into the phantom spherical volume representing the prostate and prostate phantom voxels MAX. Starting values of minimum and maximum activity, 0.27 mCi and 0.38 mCi, respectively, were simulated in the Monte Carlo code MCNPX in order to determine whether the final dose, according to the integration of the equation of decay at time t = 0 to t = {infinity} corresponds to the default value set by the AAPM 64 which is 144 Gy. The results showed that consider sources results in doses exceeding the percentage discrepancy of the default value of 200%, while volumetric consider sources result in doses close to 144 Gy. (author)

  5. [Principles of voxel-based morphometry and availability of integrated software BAAD].

    Science.gov (United States)

    Shiino, Akihiko

    2013-01-01

    BAAD is integrated software for investigation of brain morphological change using statistical parametric mapping (SPM). The basic part of the software is voxel-based morphometry (VBM) that has been developed by Drs. Ashburner and Friston. Pathological changes with neuronal loss results in brain atrophy, which can be detected by MRI. VBM provides an automated and unbiased assessment of such morphometric change throughout the brain. Recently, VBM has been drastically improved by introducing the Diffeomorphic Anatomical Registration Through Exponentiated Lie algebra (DARTEL) registration method that implements a high dimensional warping process. BAAD supports the full-length steps for VBM analysis and makes it easy for everyone. BAAD is a free software and works on 64bit Windows machine without MATLAB installation.

  6. Mechanisms underlying fatigue: a voxel-based morphometric study of chronic fatigue syndrome

    Directory of Open Access Journals (Sweden)

    Watanabe Yasuyoshi

    2004-10-01

    Full Text Available Abstract Background Fatigue is a crucial sensation that triggers rest, yet its underlying neuronal mechanisms remain unclear. Intense long-term fatigue is a symptom of chronic fatigue syndrome, which is used as a model to study the mechanisms underlying fatigue. Methods Using magnetic resonance imaging, we conducted voxel-based morphometry of 16 patients and 49 age-matched healthy control subjects. Results We found that patients with chronic fatigue syndrome had reduced gray-matter volume in the bilateral prefrontal cortex. Within these areas, the volume reduction in the right prefrontal cortex paralleled the severity of the fatigue of the subjects. Conclusion These results are consistent with previous reports of an abnormal distribution of acetyl-L-carnitine uptake, which is one of the biochemical markers of chronic fatigue syndrome, in the prefrontal cortex. Thus, the prefrontal cortex might be an important element of the neural system that regulates sensations of fatigue.

  7. Do manual and voxel-based morphometry measure the same? – A proof of concept study

    Directory of Open Access Journals (Sweden)

    Niels K. Focke

    2014-04-01

    Full Text Available Voxel-based morphometry (VBM is a commonly used method to study volumetric variations on a whole brain basis. However it is often criticised for potential confounds, mainly based on imperfect spatial registration. We therefore aimed to evaluate if VBM and gold-standard manual volumetry are measuring the same effects with respect to subcortical grey matter volumes. Manual regions-of-interest (ROIs were drawn in the hippocampus, amygdala, nucleus accumbens, thalamus, putamen, pallidum and caudate nucleus bilaterally. Resulting volumes were used for a whole brain VBM correlation analysis with SPM8. The hippocampus, amygdala, putamen and caudate nucleus were correctly identified by SPM using the contemporary high-dimensional normalization (DARTEL toolbox. This strongly suggests that VBM and manual volumetry both are indeed measuring the same effects with regard to subcortical brain structures.

  8. Brain structure in diving players on MR imaging studied with voxel-based morphometry

    Institute of Scientific and Technical Information of China (English)

    Gaoxia Wei; Jing Luo; Youfa Li

    2009-01-01

    We adopted professional diving players as a typical subject pool to explore whether structural brain differences relative to motor skill acquisition exist between highly skilled athletes and non-athletes. Based on the voxel-based morphometric (VBM) technique, structural MRIs of the brains of 12 elite diving players with professional training were analyzed and compared with those of control subjects with-out any professional physical training. Diving players showed significantly increased gray matter density in the thalamus and left pre-central gyrus than control subjects. However, future researches are needed to prove the contribution of preposition and practice. It also suggests that athletes as the subject pool could form a new subject pool to explore plastic change induced by motor skill acquisition.

  9. Voxel-Based Dose Prediction with Multi-Patient Atlas Selection for Automated Radiotherapy Treatment Planning

    CERN Document Server

    McIntosh, Chris

    2016-01-01

    Automating the radiotherapy treatment planning process is a technically challenging problem. The majority of automated approaches have focused on customizing and inferring dose volume objectives to used in plan optimization. In this work we outline a multi-patient atlas-based dose prediction approach that learns to predict the dose-per-voxel for a novel patient directly from the computed tomography (CT) planning scan without the requirement of specifying any objectives. Our method learns to automatically select the most effective atlases for a novel patient, and then map the dose from those atlases onto the novel patient. We extend our previous work to include a conditional random field for the optimization of a joint distribution prior that matches the complementary goals of an accurately spatially distributed dose distribution while still adhering to the desired dose volume histograms. The resulting distribution can then be used for inverse-planning with a new spatial dose objective, or to create typical do...

  10. Application of digital image processing for the generation of voxels phantoms for Monte Carlo simulation.

    Science.gov (United States)

    Boia, L S; Menezes, A F; Cardoso, M A C; da Rosa, L A R; Batista, D V S; Cardoso, S C; Silva, A X; Facure, A

    2012-01-01

    This paper presents the application of a computational methodology for optimizing the conversion of medical tomographic images in voxel anthropomorphic models for simulation of radiation transport using the MCNP code. A computational system was developed for digital image processing that compresses the information from the DICOM medical image before it is converted to the Scan2MCNP software input file for optimization of the image data. In order to validate the computational methodology, a radiosurgery treatment simulation was performed using the Alderson Rando phantom and the acquisition of DICOM images was performed. The simulation results were compared with data obtained with the BrainLab planning system. The comparison showed good agreement for three orthogonal treatment beams of (60)Co gamma radiation. The percentage differences were 3.07%, 0.77% and 6.15% for axial, coronal and sagital projections, respectively.

  11. Gray matter abnormalities in Internet addiction: A voxel-based morphometry study

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Yan, E-mail: clare1475@hotmail.com [Department of Radiology, RenJi Hospital, Jiao Tong University Medical School, Shanghai 200127 (China); Lin Fuchun, E-mail: fclin@wipm.ac.cn [State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Du Yasong, E-mail: yasongdu@yahoo.com.cn [Department of Child and Adolescent Psychiatry Shanghai Mental Health Center, Shanghai Jiao Tong University, Shanghai 200030 (China); Qin Lingdi, E-mail: flyingfool838@hotmail.com [Department of Radiology, RenJi Hospital, Jiao Tong University Medical School, Shanghai 200127 (China); Zhao Zhimin, E-mail: zmzsky@163.com [Department of Child and Adolescent Psychiatry Shanghai Mental Health Center, Shanghai Jiao Tong University, Shanghai 200030 (China); Xu Jianrong, E-mail: xujianr@hotmail.com [Department of Radiology, RenJi Hospital, Jiao Tong University Medical School, Shanghai 200127 (China); Lei Hao, E-mail: leihao@wipm.ac.cn [State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China)

    2011-07-15

    Background: This study aims to investigate brain gray matter density (GMD) changes in adolescents with Internet addiction (IA) using voxel-based morphometry (VBM) analysis on high-resolution T1-weighted structural magnetic resonance images. Methods: Eighteen IA adolescents and 15 age- and gender-matched healthy controls took part in this study. High-resolution T1-weighted magnetic resonance imaging scans were performed on the two groups. VBM analysis was used to compare the GMD between the two groups. Results: Compared with healthy controls, IA adolescents had lower GMD in the left anterior cingulate cortex, left posterior cingulate cortex, left insula, and left lingual gyrus. Conclusions: Our findings suggested that brain structural changes were present in IA adolescents, and this finding may provide a new insight into the pathogenesis of IA.

  12. Second generation anthropomorphic physical phantom for mammography and DBT: Incorporating voxelized 3D printing and inkjet printing of iodinated lesion inserts

    Science.gov (United States)

    Sikaria, Dhiraj; Musinsky, Stephanie; Sturgeon, Gregory M.; Solomon, Justin; Diao, Andrew; Gehm, Michael E.; Samei, Ehsan; Glick, Stephen J.; Lo, Joseph Y.

    2016-03-01

    Physical phantoms are needed for the evaluation and optimization of new digital breast tomosynthesis (DBT) systems. Previously, we developed an anthropomorphic phantom based on human subject breast CT data and fabricated using commercial 3D printing. We now present three key advancements: voxelized 3D printing, photopolymer material doping, and 2D inkjet printing of lesion inserts. First, we bypassed the printer's control software in order to print in voxelized form instead of conventional STL surfaces, thus improving resolution and allowing dithering to mix the two photopolymer materials into arbitrary proportions. We demonstrated ability to print details as small as 150μm, and dithering to combine VeroWhitePlus and TangoPlus in 10% increments. Second, to address the limited attenuation difference among commercial photopolymers, we evaluated a beta sample from Stratasys with increased TiO2 doping concentration up to 2.5%, which corresponded to 98% breast density. By spanning 36% to 98% breast density, this doubles our previous contrast. Third, using inkjet printers modified to print with iopamidol, we created 2D lesion patterns on paper that can be sandwiched into the phantom. Inkjet printing has advantages of being inexpensive and easy, and more contrast can be delivered through overprinting. Printing resolution was maintained at 210 μm horizontally and 330 μm vertically even after 10 overprints. Contrast increased linearly with overprinting at 0.7% per overprint. Together, these three new features provide the basis for creating a new anthropomorphic physical breast phantom with improved resolution and contrast, as well as the ability to insert 2D lesions for task-based assessment of performance.

  13. Tectonic calibrations in molecular dating

    Institute of Scientific and Technical Information of China (English)

    Ullasa KODANDARAMAIAH

    2011-01-01

    Molecular dating techniques require the use of calibrations, which are usually fossil or geological vicariance-based.Fossil calibrations have been criticised because they result only in minimum age estimates. Based on a historical biogeographic perspective, Ⅰ suggest that vicariance-based calibrations are more dangerous. Almost all analytical methods in historical biogeography are strongly biased towards inferring vicariance, hence vicariance identified through such methods is unreliable. Other studies, especially of groups found on Gondwanan fragments, have simply assumed vicariance. Although it was previously believed that vicariance was the predominant mode of speciation, mounting evidence now indicates that speciation by dispersal is common, dominating vicariance in several groups. Moreover, the possibility of speciation having occurred before the said geological event cannot be precluded. Thus, geological calibrations can under- or overestimate times, whereas fossil calibrations always result in minimum estimates. Another major drawback of vicariant calibrations is the problem of circular reasoning when the resulting estimates are used to infer ages of biogeographic events. Ⅰ argue that fossil-based dating is a superior alternative to vicariance, primarily because the strongest assumption in the latter, that speciation was caused by the said geological process, is more often than not the most tenuous. When authors prefer to use a combination of fossil and vicariant calibrations, one suggestion is to report results both with and without inclusion of the geological constraints. Relying solely on vicariant calibrations should be strictly avoided.

  14. Voxel-based analysis of fractional anisotropy in post-stroke apathy.

    Directory of Open Access Journals (Sweden)

    Song-ran Yang

    Full Text Available To explore the structural basis of post-stroke apathy by using voxel-based analysis (VBA of fractional anisotropy (FA maps.We enrolled 54 consecutive patients with ischemic stroke during convalescence, and divided them into apathy (n = 31 and non-apathy (n = 23 groups. We obtained magnetic resonance images of their brains, including T1, T2 and DTI sequences. Age, sex, education level, Hamilton Depression Scale (HAMD scores, Mini-Mental State Examination (MMSE scores, National Institutes of Health Stroke Scale (NIHSS scores, and infarct locations for the two groups were compared. Finally, to investigate the structural basis of post-stroke apathy, VBA of FA maps was performed in which we included the variables that a univariate analysis determined had P-values less than 0.20 as covariates.HAMD (P = 0.01 and MMSE (P<0.01 scores differed significantly between the apathy and non-apathy groups. After controlling for age, education level, HAMD scores, and MMSE scores, significant FA reduction was detected in four clusters with peak voxels at the genu of the corpus callosum (X = -16, Y = 30, Z = 8, left anterior corona radiata (-22, 30, 10, splenium of the corpus callosum (-24, -56, 18, and right inferior frontal gyrus white matter (52, 24, 18, after family-wise error correction for multiple comparisons.Post-stroke apathy is related to depression and cognitive decline. Damage to the genu of the corpus callosum, left anterior corona radiata, splenium of the corpus callosum, and white matter in the right inferior frontal gyrus may lead to apathy after ischemic stroke.

  15. An information theoretic approach for non-rigid image registration using voxel class probabilities.

    Science.gov (United States)

    D'Agostino, Emiliano; Maes, Frederik; Vandermeulen, Dirk; Suetens, Paul

    2006-06-01

    We propose two information theoretic similarity measures that allow to incorporate tissue class information in non-rigid image registration. The first measure assumes that tissue class probabilities have been assigned to each of the images to be registered by prior segmentation of both of them. One image is then non-rigidly deformed to match the other such that the fuzzy overlap of corresponding voxel object labels becomes similar to the ideal case whereby the tissue probability maps of both images are identical. Image similarity is assessed during registration by the divergence between the ideal and actual joint class probability distributions of both images. A second registration measure is proposed that applies in case a segmentation is available for only one of the images, for instance an atlas image that is to be matched to a study image to guide the segmentation thereof. Intensities in one image are matched to the fuzzy class labels in the other image by minimizing the conditional entropy of the intensities in the first image given the class labels in the second image. We derive analytic expressions for the gradient of each measure with respect to individual voxel displacements to derive a force field that drives the registration process, which is regularized by a viscous fluid model. The performance of the class-based measures is evaluated in the context of non-rigid inter-subject registration and atlas-based segmentation of MR brain images and compared with maximization of mutual information using only intensity information. Our results demonstrate that incorporation of class information in the registration measure significantly improves the overlap between corresponding tissue classes after non-rigid matching. The methods proposed here open new perspectives for integrating segmentation and registration in a single process, whereby the output of one is used to guide the other.

  16. S values for 131I based on the ICRP adult voxel phantoms

    Science.gov (United States)

    Lamart, Stephanie; Simon, Steven L.; Bouville, Andre; Moroz, Brian E.; Lee, Choonsik

    2016-01-01

    To improve the estimates of organ doses from nuclear medicine procedures using 131I, the authors calculated a comprehensive set of 131I S values, defined as absorbed doses in target tissues per unit of nuclear transition in source regions, for different source and target combinations. The authors used the latest reference adult male and female voxel phantoms published by the International Commission on Radiological Protection (ICRP Publication 110) and the 131I photon and electron spectra from the ICRP Publication 107 to perform Monte Carlo radiation transport calculations using MCNPX2.7 to compute the S values. For each phantom, the authors simulated 55 source regions with an assumed uniform distribution of 131I. They computed the S values for 42 target tissues directly, without calculating specific absorbed fractions. From these calculations, the authors derived a comprehensive set of S values for 131I for 55 source regions and 42 target tissues in the ICRP male and female voxel phantoms. Compared with the stylised phantoms from Oak Ridge National Laboratory (ORNL) that consist of 22 source regions and 24 target regions, the new data set includes 1662 additional S values corresponding to additional combinations of source–target tissues that are not available in the stylised phantoms. In a comparison of S values derived from the ICRP and ORNL phantoms, the authors found that the S values to the radiosensitive tissues in the ICRP phantoms were 1.1 (median, female) and 1.3 (median, male) times greater than the values based on the ORNL phantoms. However, for several source–target pairs, the difference was up to 10-fold. The new set of S values can be applied prospectively or retrospectively to the calculation of radiation doses in adults internally exposed to 131I, including nuclear medicine patients treated for thyroid cancer or hyperthyroidism. PMID:25829162

  17. Voxel-based lesion-symptom mapping of stroke lesions underlying somatosensory deficits

    Directory of Open Access Journals (Sweden)

    Sarah Meyer

    2016-01-01

    Full Text Available The aim of this study was to investigate the relationship between stroke lesion location and the resulting somatosensory deficit. We studied exteroceptive and proprioceptive somatosensory symptoms and stroke lesions in 38 patients with first-ever acute stroke. The Erasmus modified Nottingham Sensory Assessment was used to clinically evaluate somatosensory functioning in the arm and hand within the first week after stroke onset. Additionally, more objective measures such as the perceptual threshold of touch and somatosensory evoked potentials were recorded. Non-parametric voxel-based lesion-symptom mapping was performed to investigate lesion contribution to different somatosensory deficits in the upper limb. Additionally, structural connectivity of brain areas that demonstrated the strongest association with somatosensory symptoms was determined, using probabilistic fiber tracking based on diffusion tensor imaging data from a healthy age-matched sample. Voxels with a significant association to somatosensory deficits were clustered in two core brain regions: the central parietal white matter, also referred to as the sensory component of the superior thalamic radiation, and the parietal operculum close to the insular cortex, representing the secondary somatosensory cortex. Our objective recordings confirmed findings from clinical assessments. Probabilistic tracking connected the first region to thalamus, internal capsule, brain stem, postcentral gyrus, cerebellum, and frontal pathways, while the second region demonstrated structural connections to thalamus, insular and primary somatosensory cortex. This study reveals that stroke lesions in the sensory fibers of the superior thalamocortical radiation and the parietal operculum are significantly associated with multiple exteroceptive and proprioceptive deficits in the arm and hand.

  18. Voxel-based lesion-symptom mapping of stroke lesions underlying somatosensory deficits

    Science.gov (United States)

    Meyer, Sarah; Kessner, Simon S.; Cheng, Bastian; Bönstrup, Marlene; Schulz, Robert; Hummel, Friedhelm C.; De Bruyn, Nele; Peeters, Andre; Van Pesch, Vincent; Duprez, Thierry; Sunaert, Stefan; Schrooten, Maarten; Feys, Hilde; Gerloff, Christian; Thomalla, Götz; Thijs, Vincent; Verheyden, Geert

    2015-01-01

    The aim of this study was to investigate the relationship between stroke lesion location and the resulting somatosensory deficit. We studied exteroceptive and proprioceptive somatosensory symptoms and stroke lesions in 38 patients with first-ever acute stroke. The Erasmus modified Nottingham Sensory Assessment was used to clinically evaluate somatosensory functioning in the arm and hand within the first week after stroke onset. Additionally, more objective measures such as the perceptual threshold of touch and somatosensory evoked potentials were recorded. Non-parametric voxel-based lesion-symptom mapping was performed to investigate lesion contribution to different somatosensory deficits in the upper limb. Additionally, structural connectivity of brain areas that demonstrated the strongest association with somatosensory symptoms was determined, using probabilistic fiber tracking based on diffusion tensor imaging data from a healthy age-matched sample. Voxels with a significant association to somatosensory deficits were clustered in two core brain regions: the central parietal white matter, also referred to as the sensory component of the superior thalamic radiation, and the parietal operculum close to the insular cortex, representing the secondary somatosensory cortex. Our objective recordings confirmed findings from clinical assessments. Probabilistic tracking connected the first region to thalamus, internal capsule, brain stem, postcentral gyrus, cerebellum, and frontal pathways, while the second region demonstrated structural connections to thalamus, insular and primary somatosensory cortex. This study reveals that stroke lesions in the sensory fibers of the superior thalamocortical radiation and the parietal operculum are significantly associated with multiple exteroceptive and proprioceptive deficits in the arm and hand. PMID:26900565

  19. Voxel-based analysis of grey and white matter degeneration in cervical spondylotic myelopathy.

    Science.gov (United States)

    Grabher, Patrick; Mohammadi, Siawoosh; Trachsler, Aaron; Friedl, Susanne; David, Gergely; Sutter, Reto; Weiskopf, Nikolaus; Thompson, Alan J; Curt, Armin; Freund, Patrick

    2016-04-20

    In this prospective study, we made an unbiased voxel-based analysis to investigate above-stenosis spinal degeneration and its relation to impairment in patients with cervical spondylotic myelopathy (CSM). Twenty patients and 18 controls were assessed with high-resolution MRI protocols above the level of stenosis. Cross-sectional areas of grey matter (GM), white matter (WM), and posterior columns (PC) were measured to determine atrophy. Diffusion indices assessed tract-specific integrity of PC and lateral corticospinal tracts (CST). Regression analysis was used to reveal relationships between MRI measures and clinical impairment. Patients showed mainly sensory impairment. Atrophy was prominent within the cervical WM (13.9%, p = 0.004), GM (7.2%, p = 0.043), and PC (16.1%, p = 0.005). Fractional anisotropy (FA) was reduced in the PC (-11.98%, p = 0.006) and lateral CST (-12.96%, p = 0.014). In addition, radial (+28.47%, p = 0.014), axial (+14.72%, p = 0.005), and mean (+16.50%, p = 0.001) diffusivities were increased in the PC. Light-touch score was associated with atrophy (R(2) = 0.3559, p = 0.020) and FA (z score 3.74, p = 0.003) in the PC, as was functional independence and FA in the lateral CST (z score 3.68, p = 0.020). This study demonstrates voxel-based degeneration far above the stenosis at a level not directly affected by the compression and provides unbiased readouts of tract-specific changes that relate to impairment.

  20. Voxel Based Analysis of Surgical Revascularization for Moyamoya Disease: Pre- and Postoperative SPECT Studies.

    Directory of Open Access Journals (Sweden)

    Yasutaka Fushimi

    Full Text Available Moyamoya disease (MMD is a chronic, progressive, cerebrovascular occlusive disease that causes abnormal enlargement of collateral pathways (moyamoya vessels in the region of the basal ganglia and thalamus. Cerebral revascularization procedures remain the preferred treatment for patients with MMD, improving the compromised cerebral blood flow (CBF. However, voxel based analysis (VBA of revascularization surgery for MMD based on data from pre- and postoperative data has not been established. The latest algorithm called as Diffeomorphic Anatomical Registration Through Exponentiated Lie Algebra (DARTEL has been introduced for VBA as the function of statistical parametric mapping (SPM8, and improved registration has been achieved by SPM8 with DARTEL. In this study, VBA was conducted to evaluate pre- and postoperative single photon emission computed tomography (SPECT images for MMD by SPM8 with DARTEL algorithm, and the results were compared with those from SPM8 without DARTEL (a conventional method. Thirty-two patients with MMD who underwent superficial temporal artery-middle cerebral artery (STA-MCA bypass surgery as the first surgery were included and all patients underwent pre- and postoperative 3D T1-weighted imaging and SPECT. Pre- and postoperative SPECT images were registered to 3D T1-weighted images, then VBA was conducted. Postoperative SPECT showed more statistically increased CBF areas in the bypassed side cerebral hemisphere by using SPM8 with DARTEL (58,989 voxels; P<0.001, and increased ratio of CBF after operation was less than 15%. Meanwhile, postoperative SPECT showed less CBF increased areas by SPM8 without DARTEL. In conclusion, VBA was conducted for patients with MMD, and SPM8 with DARTEL revealed that postoperative SPECT showed statistically significant CBF increases over a relatively large area and with at most 15% increase ratio.

  1. The Advanced LIGO Photon Calibrators

    CERN Document Server

    Karki, S; Kandhasamy, S; Abbott, B P; Abbott, T D; Anders, E H; Berliner, J; Betzwieser, J; Daveloza, H P; Cahillane, C; Canete, L; Conley, C; Gleason, J R; Goetz, E; Kissel, J S; Izumi, K; Mendell, G; Quetschke, V; Rodruck, M; Sachdev, S; Sadecki, T; Schwinberg, P B; Sottile, A; Wade, M; Weinstein, A J; West, M; Savage, R L

    2016-01-01

    The two interferometers of the Laser Interferometry Gravitaional-wave Observatory (LIGO) recently detected gravitational waves from the mergers of binary black hole systems. Accurate calibration of the output of these detectors was crucial for the observation of these events, and the extraction of parameters of the sources. The principal tools used to calibrate the responses of the second-generation (Advanced) LIGO detectors to gravitational waves are systems based on radiation pressure and referred to as Photon Calibrators. These systems, which were completely redesigned for Advanced LIGO, include several significant upgrades that enable them to meet the calibration requirements of second-generation gravitational wave detectors in the new era of gravitational-wave astronomy. We report on the design, implementation, and operation of these Advanced LIGO Photon Calibrators that are currently providing fiducial displacements on the order of $10^{-18}$ m/$\\sqrt{\\textrm{Hz}}$ with accuracy and precision of better ...

  2. The Advanced LIGO photon calibrators

    Science.gov (United States)

    Karki, S.; Tuyenbayev, D.; Kandhasamy, S.; Abbott, B. P.; Abbott, T. D.; Anders, E. H.; Berliner, J.; Betzwieser, J.; Cahillane, C.; Canete, L.; Conley, C.; Daveloza, H. P.; De Lillo, N.; Gleason, J. R.; Goetz, E.; Izumi, K.; Kissel, J. S.; Mendell, G.; Quetschke, V.; Rodruck, M.; Sachdev, S.; Sadecki, T.; Schwinberg, P. B.; Sottile, A.; Wade, M.; Weinstein, A. J.; West, M.; Savage, R. L.

    2016-11-01

    The two interferometers of the Laser Interferometry Gravitational-wave Observatory (LIGO) recently detected gravitational waves from the mergers of binary black hole systems. Accurate calibration of the output of these detectors was crucial for the observation of these events and the extraction of parameters of the sources. The principal tools used to calibrate the responses of the second-generation (Advanced) LIGO detectors to gravitational waves are systems based on radiation pressure and referred to as photon calibrators. These systems, which were completely redesigned for Advanced LIGO, include several significant upgrades that enable them to meet the calibration requirements of second-generation gravitational wave detectors in the new era of gravitational-wave astronomy. We report on the design, implementation, and operation of these Advanced LIGO photon calibrators that are currently providing fiducial displacements on the order of 1 0-18m /√{Hz } with accuracy and precision of better than 1%.

  3. TIME CALIBRATED OSCILLOSCOPE SWEEP CIRCUIT

    Science.gov (United States)

    Smith, V.L.; Carstensen, H.K.

    1959-11-24

    An improved time calibrated sweep circuit is presented, which extends the range of usefulness of conventional oscilloscopes as utilized for time calibrated display applications in accordance with U. S. Patent No. 2,832,002. Principal novelty resides in the provision of a pair of separate signal paths, each of which is phase and amplitude adjustable, to connect a high-frequency calibration oscillator to the output of a sawtooth generator also connected to the respective horizontal deflection plates of an oscilloscope cathode ray tube. The amplitude and phase of the calibration oscillator signals in the two signal paths are adjusted to balance out feedthrough currents capacitively coupled at high frequencies of the calibration oscillator from each horizontal deflection plate to the vertical plates of the cathode ray tube.

  4. Automated calibration of multistatic arrays

    Energy Technology Data Exchange (ETDEWEB)

    Henderer, Bruce

    2017-03-14

    A method is disclosed for calibrating a multistatic array having a plurality of transmitter and receiver pairs spaced from one another along a predetermined path and relative to a plurality of bin locations, and further being spaced at a fixed distance from a stationary calibration implement. A clock reference pulse may be generated, and each of the transmitters and receivers of each said transmitter/receiver pair turned on at a monotonically increasing time delay interval relative to the clock reference pulse. Ones of the transmitters and receivers may be used such that a previously calibrated transmitter or receiver of a given one of the transmitter/receiver pairs is paired with a subsequently un-calibrated one of the transmitters or receivers of an immediately subsequently positioned transmitter/receiver pair, to calibrate the transmitter or receiver of the immediately subsequent transmitter/receiver pair.

  5. Antenna Calibration and Measurement Equipment

    Science.gov (United States)

    Rochblatt, David J.; Cortes, Manuel Vazquez

    2012-01-01

    A document describes the Antenna Calibration & Measurement Equipment (ACME) system that will provide the Deep Space Network (DSN) with instrumentation enabling a trained RF engineer at each complex to perform antenna calibration measurements and to generate antenna calibration data. This data includes continuous-scan auto-bore-based data acquisition with all-sky data gathering in support of 4th order pointing model generation requirements. Other data includes antenna subreflector focus, system noise temperature and tipping curves, antenna efficiency, reports system linearity, and instrument calibration. The ACME system design is based on the on-the-fly (OTF) mapping technique and architecture. ACME has contributed to the improved RF performance of the DSN by approximately a factor of two. It improved the pointing performances of the DSN antennas and productivity of its personnel and calibration engineers.

  6. A calibrated Franklin chimes

    Science.gov (United States)

    Gonta, Igor; Williams, Earle

    1994-05-01

    Benjamin Franklin devised a simple yet intriguing device to measure electrification in the atmosphere during conditions of foul weather. He constructed a system of bells, one of which was attached to a conductor that was suspended vertically above his house. The device is illustrated in a well-known painting of Franklin (Cohen, 1985). The elevated conductor acquired a potential due to the electric field in the atmosphere and caused a brass ball to oscillate between two bells. The purpose of this study is to extend Franklin's idea by constructing a set of 'chimes' which will operate both in fair and in foul weather conditions. In addition, a mathematical relationship will be established between the frequency of oscillation of a metallic sphere in a simplified geometry and the potential on one plate due to the electrification of the atmosphere. Thus it will be possible to calibrate the 'Franklin Chimes' and to obtain a nearly instantaneous measurement of the potential of the elevated conductor in both fair and foul weather conditions.

  7. Accuracy of linear measurements from cone-beam computed tomography-derived surface models of different voxel sizes

    NARCIS (Netherlands)

    Damstra, Janalt; Fourie, Zacharias; Huddleston Slater, James J R; Ren, Yijin

    2010-01-01

    INTRODUCTION: The aims of this study were to determine the linear accuracy of 3-dimensional surface models derived from a commercially available cone-beam computed tomography (CBCT) dental imaging system and volumetric rendering software and to investigate the influence of voxel resolution on the li

  8. Segmentation Based Classification of 3D Urban Point Clouds: A Super-Voxel Based Approach with Evaluation

    Directory of Open Access Journals (Sweden)

    Laurent Trassoudaine

    2013-03-01

    Full Text Available Segmentation and classification of urban range data into different object classes have several challenges due to certain properties of the data, such as density variation, inconsistencies due to missing data and the large data size that require heavy computation and large memory. A method to classify urban scenes based on a super-voxel segmentation of sparse 3D data obtained from LiDAR sensors is presented. The 3D point cloud is first segmented into voxels, which are then characterized by several attributes transforming them into super-voxels. These are joined together by using a link-chain method rather than the usual region growing algorithm to create objects. These objects are then classified using geometrical models and local descriptors. In order to evaluate the results, a new metric that combines both segmentation and classification results simultaneously is presented. The effects of voxel size and incorporation of RGB color and laser reflectance intensity on the classification results are also discussed. The method is evaluated on standard data sets using different metrics to demonstrate its efficacy.

  9. Abnormal Functional Specialization within Medial Prefrontal Cortex in High-Functioning Autism: A Multi-Voxel Similarity Analysis

    Science.gov (United States)

    Gilbert, Sam J.; Meuwese, Julia D. I.; Towgood, Karren J.; Frith, Christopher D.; Burgess, Paul W.

    2009-01-01

    Multi-voxel pattern analyses have proved successful in "decoding" mental states from fMRI data, but have not been used to examine brain differences associated with atypical populations. We investigated a group of 16 (14 males) high-functioning participants with autism spectrum disorder (ASD) and 16 non-autistic control participants (12 males)…

  10. Dyslexia and Voxel-Based Morphometry: Correlations between Five Behavioural Measures of Dyslexia and Gray and White Matter Volumes

    Science.gov (United States)

    Tamboer, Peter; Scholte, H. Steven; Vorst, Harrie C. M.

    2015-01-01

    In voxel-based morphometry studies of dyslexia, the relation between causal theories of dyslexia and gray matter (GM) and white matter (WM) volume alterations is still under debate. Some alterations are consistently reported, but others failed to reach significance. We investigated GM alterations in a large sample of Dutch students (37 dyslexics…

  11. Voxel-Wise Functional Connectomics Using Arterial Spin Labeling Functional Magnetic Resonance Imaging: The Role of Denoising.

    Science.gov (United States)

    Liang, Xiaoyun; Connelly, Alan; Calamante, Fernando

    2015-11-01

    The objective of this study was to investigate voxel-wise functional connectomics using arterial spin labeling (ASL) functional magnetic resonance imaging (fMRI). Since ASL signal has an intrinsically low signal-to-noise ratio (SNR), the role of denoising is evaluated; in particular, a novel denoising method, dual-tree complex wavelet transform (DT-CWT) combined with the nonlocal means (NLM) algorithm is implemented and evaluated. Simulations were conducted to evaluate the performance of the proposed method in denoising images and in detecting functional networks from noisy data (including the accuracy and sensitivity of detection). In addition, denoising was applied to in vivo ASL datasets, followed by network analysis using graph theoretical approaches. Efficiencies cost was used to evaluate the performance of denoising in detecting functional networks from in vivo ASL fMRI data. Simulations showed that denoising is effective in detecting voxel-wise functional networks from low SNR data and/or from data with small total number of time points. The capability of denoised voxel-wise functional connectivity analysis was also demonstrated with in vivo data. We concluded that denoising is important for voxel-wise functional connectivity using ASL fMRI and that the proposed DT-CWT-NLM method should be a useful ASL preprocessing step.

  12. The Neural Basis of Reversible Sentence Comprehension: Evidence from Voxel-Based Lesion Symptom Mapping in Aphasia

    Science.gov (United States)

    Thothathiri, Malathi; Kimberg, Daniel Y.; Schwartz, Myrna F.

    2012-01-01

    We explored the neural basis of reversible sentence comprehension in a large group of aphasic patients (n = 79). Voxel-based lesion symptom mapping revealed a significant association between damage in temporo-parietal cortex and impaired sentence comprehension. This association remained after we controlled for phonological working memory. We…

  13. 基于锥形束CT图像采用XVMC剂量算法时射束能量的影响%The Influence of Energy on X-ray Voxel Monte Carlo Algorithm Based on Kilovoltage Cone Beam Computed Tomography Images for Dose Calculation

    Institute of Scientific and Technical Information of China (English)

    吴魁; 李光俊; 柏森

    2012-01-01

    研究在千伏级锥形束CT(CBCT)图像中不同的能量对X-ray Voxel Monte Carlo(XVMC)算法剂量计算精度的影响.采用CIRS062模体刻度CT和CBCT图像的CT值-相对电子密度表,用头颈部人体仿真模体(CDP)在相同摆位条件下分别行CT和CBCT扫描,并在CDP中模拟局部进展期鼻咽癌病例,在Monaco计划系统中设计IMRT计划,选取的能量包括6 MV和15 MV光子,用XVMC算法分别对CT和CBCT图像进行剂量计算,排除旋转摆位误差等其他因素带来的误差后对CT和CBCT计划的结果进行比较,并分析能量因素产生的影响.DVHs、靶区和危及器官受量的比较以及靶区剂量适型度和均匀性的比较均显示了CT和CBCT计划有较好的符合度,从多数评估指标来看,15 MV能量时CT和CBCT计划的偏差更小.对CT和CBCT计划的剂量分布的比较采用γ分析,标准是2 mm/2%,阈值是10%,6 MV能量时各个平面的平均通过率分别是99.3%±0.47%,15 MV能量时则是99.4%±0.44%.显示出CBCT图像重新进行相对电子密度刻度后用XVMC算法进行剂量计算时具有良好的精度,选用15 MV能量时计算结果精度更高.%This paper is to investigate how the different energy impact the accuracy of X-ray Voxel Monte Carlo (XVMC ) algorithm when it is applied for dose calculation in Kilovoltage cone beam CT(kv-CBCT) images. The CIRS model 062 was used to calibrate the CT numbers-relative electron density table of CT and CBCT images. CT and CBCT scans were performed when simulation model of human head-and-neck placed in same position to simulate locally advanced nasopharyngeal carcinoma. 6MV and 15MV photon were selected in Monaco TPS to design intensity-modulated radiotherapy( 1MRT) plans. XVMC algorithm was selected for dose calculation then the calculation results were compared and the impact of energy on the calculation accuracy was analyzed. The comparison results of dose volume histograms(DVHs), dose received by targets, organs at

  14. Mercury Continuous Emmission Monitor Calibration

    Energy Technology Data Exchange (ETDEWEB)

    John Schabron; Eric Kalberer; Ryan Boysen; William Schuster; Joseph Rovani

    2009-03-12

    Mercury continuous emissions monitoring systems (CEMs) are being implemented in over 800 coal-fired power plant stacks throughput the U.S. Western Research Institute (WRI) is working closely with the Electric Power Research Institute (EPRI), the National Institute of Standards and Technology (NIST), and the Environmental Protection Agency (EPA) to facilitate the development of the experimental criteria for a NIST traceability protocol for dynamic elemental mercury vapor calibrators/generators. These devices are used to calibrate mercury CEMs at power plant sites. The Clean Air Mercury Rule (CAMR) which was published in the Federal Register on May 18, 2005 and vacated by a Federal appeals court in early 2008 required that calibration be performed with NIST-traceable standards. Despite the vacature, mercury emissions regulations in the future will require NIST traceable calibration standards, and EPA does not want to interrupt the effort towards developing NIST traceability protocols. The traceability procedures will be defined by EPA. An initial draft traceability protocol was issued by EPA in May 2007 for comment. In August 2007, EPA issued a conceptual interim traceability protocol for elemental mercury calibrators. The protocol is based on the actual analysis of the output of each calibration unit at several concentration levels ranging initially from about 2-40 {micro}g/m{sup 3} elemental mercury, and in the future down to 0.2 {micro}g/m{sup 3}, and this analysis will be directly traceable to analyses by NIST. The EPA traceability protocol document is divided into two separate sections. The first deals with the qualification of calibrator models by the vendors for use in mercury CEM calibration. The second describes the procedure that the vendors must use to certify the calibrators that meet the qualification specifications. The NIST traceable certification is performance based, traceable to analysis using isotope dilution inductively coupled plasma

  15. Effect of micro-computed tomography voxel size and segmentation method on trabecular bone microstructure measures in mice.

    Science.gov (United States)

    Christiansen, Blaine A

    2016-12-01

    Micro-computed tomography (μCT) is currently the gold standard for determining trabecular bone microstructure in small animal models. Numerous parameters associated with scanning and evaluation of μCT scans can strongly affect morphologic results obtained from bone samples. However, the effect of these parameters on specific trabecular bone outcomes is not well understood. This study investigated the effect of μCT scanning with nominal voxel sizes between 6-30 μm on trabecular bone outcomes quantified in mouse vertebral body trabecular bone. Additionally, two methods for determining a global segmentation threshold were compared: based on qualitative assessment of 2D images, or based on quantitative assessment of image histograms. It was found that nominal voxel size had a strong effect on several commonly reported trabecular bone parameters, in particular connectivity density, trabecular thickness, and bone tissue mineral density. Additionally, the two segmentation methods provided similar trabecular bone outcomes for scans with small nominal voxel sizes, but considerably different outcomes for scans with larger voxel sizes. The Qualitatively Selected segmentation method more consistently estimated trabecular bone volume fraction (BV/TV) and trabecular thickness across different voxel sizes, but the Histogram segmentation method more consistently estimated trabecular number, trabecular separation, and structure model index. Altogether, these results suggest that high-resolution scans be used whenever possible to provide the most accurate estimation of trabecular bone microstructure, and that the limitations of accurately determining trabecular bone outcomes should be considered when selecting scan parameters and making conclusions about inter-group variance or between-group differences in studies of trabecular bone microstructure in small animals.

  16. Mexican national pyronometer network calibration

    Science.gov (United States)

    VAldes, M.; Villarreal, L.; Estevez, H.; Riveros, D.

    2013-12-01

    In order to take advantage of the solar radiation as an alternate energy source it is necessary to evaluate the spatial and temporal availability. The Mexican National Meterological Service (SMN) has a network with 136 meteorological stations, each coupled with a pyronometer for measuring the global solar radiation. Some of these stations had not been calibrated in several years. The Mexican Department of Energy (SENER) in order to count on a reliable evaluation of the solar resource funded this project to calibrate the SMN pyrometer network and validate the data. The calibration of the 136 pyronometers by the intercomparison method recommended by the World Meterological Organization (WMO) requires lengthy observations and specific environmental conditions such as clear skies and a stable atmosphere, circumstances that determine the site and season of the calibration. The Solar Radiation Section of the Instituto de Geofísica of the Universidad Nacional Autónoma de México is a Regional Center of the WMO and is certified to carry out the calibration procedures and emit certificates. We are responsible for the recalibration of the pyronometer network of the SMN. A continuous emission solar simulator with exposed areas with 30cm diameters was acquired to reduce the calibration time and not depend on atmospheric conditions. We present the results of the calibration of 10 thermopile pyronometers and one photovoltaic cell by the intercomparison method with more than 10000 observations each and those obtained with the solar simulator.

  17. Jet energy calibration in ATLAS

    CERN Document Server

    Schouten, Doug

    A correct energy calibration for jets is essential to the success of the ATLAS experi- ment. In this thesis I study a method for deriving an in situ jet energy calibration for the ATLAS detector. In particular, I show the applicability of the missing transverse energy projection fraction method. This method is shown to set the correct mean energy for jets. Pileup effects due to the high luminosities at ATLAS are also stud- ied. I study the correlations in lateral distributions of pileup energy, as well as the luminosity dependence of the in situ calibration metho

  18. Calibrating System for Vacuum Gauges

    Institute of Scientific and Technical Information of China (English)

    MengJun; YangXiaotian; HaoBinggan; HouShengjun; HuZhenjun

    2003-01-01

    In order to measure the vacuum degree, a lot of vacuum gauges will be used in CSR vacuum system. We bought several types of vacuum gauges. We know that different typos of vacuum gauges or even one type of vacuum gauges have different measure results in same condition, so they must be calibrated. But it seems impossible for us to send so many gauges to the calibrating station outside because of the high price. So the best choice is to build a second class calibrating station for vacuum gauges by ourselves (Fig.l).

  19. A two-stage scheme for multi-view human pose estimation

    Science.gov (United States)

    Yan, Junchi; Sun, Bing; Liu, Yuncai

    2010-08-01

    We present a two-stage scheme integrating voxel reconstruction and human motion tacking. By combining voxel reconstruction with human motion tracking interactively, our method can work in a cluttered background where perfect foreground silhouettes are hardly available. For each frame, a silhouette-based 3D volume reconstruction method and hierarchical tracking algorithm are applied in two stages. In the first stage, coarse reconstruction and tracking results are obtained, and then the refinement for reconstruction is applied in the second stage. The experimental results demonstrate our approach is promising. Although our method focuses on the problem of human body voxel reconstruction and motion tracking in this paper, our scheme can be used to reconstruct voxel data and infer the pose of many specified rigid and articulated objects.

  20. Calibration of "Babyline" RP instruments

    CERN Multimedia

    2015-01-01

      If you have old RP instrumentation of the “Babyline” type, as shown in the photo, please contact the Radiation Protection Group (Joffrey Germa, 73171) to have the instrument checked and calibrated. Thank you. Radiation Protection Group

  1. Field calibration of cup anemometers

    Energy Technology Data Exchange (ETDEWEB)

    Kristensen, L.; Jensen, G.; Hansen, A.; Kirkegaard, P.

    2001-01-01

    An outdoor calibration facility for cup anemometers, where the signals from 10 anemometers of which at least one is a reference can be recorded simultaneously, has been established. The results are discussed with special emphasis on the statistical significance of the calibration expressions. It is concluded that the method has the advantage that many anemometers can be calibrated accurately with a minimum of work and cost. The obvious disadvantage is that the calibration of a set of anemometers may take more than one month in order to have wind speeds covering a sufficiently large magnitude range in a wind direction sector where we can be sure that the instruments are exposed to identical, simultaneous wind flows. Another main conclusion is that statistical uncertainty must be carefully evaluated since the individual 10 minute wind-speed averages are not statistically independent. (au)

  2. Infrasound Sensor Calibration and Response

    Science.gov (United States)

    2012-09-01

    functions with faster rise times. SUMMARY We have documented past work on the determination of the calibration constant of the LANL infrasound sensor...Monitoring Technologies 735 Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden for the collection of information is estimated...National Laboratory ( LANL ) has operated an infrasound sensor calibration chamber that operates over a frequency range of 0.02 to 4 Hz. This chamber has

  3. Bayesian Calibration of Microsimulation Models.

    Science.gov (United States)

    Rutter, Carolyn M; Miglioretti, Diana L; Savarino, James E

    2009-12-01

    Microsimulation models that describe disease processes synthesize information from multiple sources and can be used to estimate the effects of screening and treatment on cancer incidence and mortality at a population level. These models are characterized by simulation of individual event histories for an idealized population of interest. Microsimulation models are complex and invariably include parameters that are not well informed by existing data. Therefore, a key component of model development is the choice of parameter values. Microsimulation model parameter values are selected to reproduce expected or known results though the process of model calibration. Calibration may be done by perturbing model parameters one at a time or by using a search algorithm. As an alternative, we propose a Bayesian method to calibrate microsimulation models that uses Markov chain Monte Carlo. We show that this approach converges to the target distribution and use a simulation study to demonstrate its finite-sample performance. Although computationally intensive, this approach has several advantages over previously proposed methods, including the use of statistical criteria to select parameter values, simultaneous calibration of multiple parameters to multiple data sources, incorporation of information via prior distributions, description of parameter identifiability, and the ability to obtain interval estimates of model parameters. We develop a microsimulation model for colorectal cancer and use our proposed method to calibrate model parameters. The microsimulation model provides a good fit to the calibration data. We find evidence that some parameters are identified primarily through prior distributions. Our results underscore the need to incorporate multiple sources of variability (i.e., due to calibration data, unknown parameters, and estimated parameters and predicted values) when calibrating and applying microsimulation models.

  4. Pressures Detector Calibration and Measurement

    CERN Document Server

    AUTHOR|(CDS)2156315

    2016-01-01

    This is report of my first and second projects (of 3) in NA61. I did data taking and analysis in order to do calibration of pressure detectors and verified it. I analyzed the data by ROOT software using the C ++ programming language. The first part of my project was determination of calibration factor of pressure sensors. Based on that result, I examined the relation between pressure drop, gas flow rate of in paper filter and its diameter.

  5. Beam Imaging and Luminosity Calibration

    CERN Document Server

    Klute, Markus; Salfeld-Nebgen, Jakob

    2016-01-01

    We discuss a method to reconstruct two-dimensional proton bunch densities using vertex distributions accumulated during LHC beam-beam scans. The $x$-$y$ correlations in the beam shapes are studied and an alternative luminosity calibration technique is introduced. We demonstrate the method on simulated beam-beam scans and estimate the uncertainty on the luminosity calibration associated to the beam-shape reconstruction to be below 1\\%.

  6. Comparison among physical and mathematical simulation methods to calibrate the scintillating detector to determine the high energy radionuclides in human body; Comparacao entre metodos de simulacao fisica e matematica para calibracao de detetor de cintilacao, visando a determinacao de radionuclideos de alta energia no corpo humano

    Energy Technology Data Exchange (ETDEWEB)

    Mello, J.Q.; Dantas, A.L.A.; Almeida, A.P.F.; Hunt, J.G.; Dantas, B.M., E-mail: jquince@bolsista.ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2015-07-01

    In vivo monitoring of photon emitters requires prior calibration of the detectors in order to obtain factors relate the count rate obtained in measuring the individual with this activity in the body. In this work were compared two calibration methods of a Nal scintillation detector (Tl) 3 x 3 for determination in vivo of {sup 40}K: (1) Experimental method using a physical-anthropomorphic simulator called BOMAB and (2) mathematical method using the VMC software (Visual Monte Carlo). Both methods aim at simulation of radionuclide distribution in the human body geometry and interaction of photons with the detector. The obtained results show the similarities and limitations of the evaluated methods for the measurement conditions used.

  7. Voxel-based clustered imaging by multiparameter diffusion tensor images for glioma grading.

    Science.gov (United States)

    Inano, Rika; Oishi, Naoya; Kunieda, Takeharu; Arakawa, Yoshiki; Yamao, Yukihiro; Shibata, Sumiya; Kikuchi, Takayuki; Fukuyama, Hidenao; Miyamoto, Susumu

    2014-01-01

    Gliomas are the most common intra-axial primary brain tumour; therefore, predicting glioma grade would influence therapeutic strategies. Although several methods based on single or multiple parameters from diagnostic images exist, a definitive method for pre-operatively determining glioma grade remains unknown. We aimed to develop an unsupervised method using multiple parameters from pre-operative diffusion tensor images for obtaining a clustered image that could enable visual grading of gliomas. Fourteen patients with low-grade gliomas and 19 with high-grade gliomas underwent diffusion tensor imaging and three-dimensional T1-weighted magnetic resonance imaging before tumour resection. Seven features including diffusion-weighted imaging, fractional anisotropy, first eigenvalue, second eigenvalue, third eigenvalue, mean diffusivity and raw T2 signal with no diffusion weighting, were extracted as multiple parameters from diffusion tensor imaging. We developed a two-level clustering approach for a self-organizing map followed by the K-means algorithm to enable unsupervised clustering of a large number of input vectors with the seven features for the whole brain. The vectors were grouped by the self-organizing map as protoclusters, which were classified into the smaller number of clusters by K-means to make a voxel-based diffusion tensor-based clustered image. Furthermore, we also determined if the diffusion tensor-based clustered image was really helpful for predicting pre-operative glioma grade in a supervised manner. The ratio of each class in the diffusion tensor-based clustered images was calculated from the regions of interest manually traced on the diffusion tensor imaging space, and the common logarithmic ratio scales were calculated. We then applied support vector machine as a classifier for distinguishing between low- and high-grade gliomas. Consequently, the sensitivity, specificity, accuracy and area under the curve of receiver operating characteristic

  8. The accuracy of linear measurements of maxillary and mandibular edentulous sites in cone-beam computed tomography images with different fields of view and voxel sizes under simulated clinical conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ganguly, Rumpa; Ramesh, Aruna; Pagni, Sarah [Tufts University School of Dental Medicine, Boston (United States)

    2016-06-15

    The objective of this study was to investigate the effect of varying resolutions of cone-beam computed tomography images on the accuracy of linear measurements of edentulous areas in human cadaver heads. Intact cadaver heads were used to simulate a clinical situation. Fiduciary markers were placed in the edentulous areas of 4 intact embalmed cadaver heads. The heads were scanned with two different CBCT units using a large field of view (13 cm×16 cm) and small field of view (5 cm×8 cm) at varying voxel sizes (0.3 mm, 0.2 mm, and 0.16 mm). The ground truth was established with digital caliper measurements. The imaging measurements were then compared with caliper measurements to determine accuracy. The Wilcoxon signed rank test revealed no statistically significant difference between the medians of the physical measurements obtained with calipers and the medians of the CBCT measurements. A comparison of accuracy among the different imaging protocols revealed no significant differences as determined by the Friedman test. The intraclass correlation coefficient was 0.961, indicating excellent reproducibility. Inter-observer variability was determined graphically with a Bland-Altman plot and by calculating the intraclass correlation coefficient. The Bland-Altman plot indicated very good reproducibility for smaller measurements but larger discrepancies with larger measurements. The CBCT-based linear measurements in the edentulous sites using different voxel sizes and FOVs are accurate compared with the direct caliper measurements of these sites. Higher resolution CBCT images with smaller voxel size did not result in greater accuracy of the linear measurements.

  9. Differences among Monte Carlo codes in the calculations of voxel S values for radionuclide targeted therapy and analysis of their impact on absorbed dose evaluations

    Energy Technology Data Exchange (ETDEWEB)

    Pacilio, M.; Lanconelli, N.; Lo Meo, S.; Betti, M.; Montani, L.; Torres Aroche, L. A.; Coca Perez, M. A. [Department of Medical Physics, Azienda Ospedaliera S. Camillo Forlanini, Piazza Forlanini 1, Rome 00151 (Italy); Department of Physics, Alma Mater Studiorum University of Bologna, Viale Berti-Pichat 6/2, Bologna 40127 (Italy); Department of Medical Physics, Azienda Ospedaliera S. Camillo Forlanini, Piazza Forlanini 1, Rome 00151 (Italy); Department of Medical Physics, Azienda Ospedaliera Sant' Andrea, Via di Grotarossa 1035, Rome 00189 (Italy); Department of Medical Physics, Center for Clinical Researches, Calle 34 North 4501, Havana 11300 (Cuba)

    2009-05-15

    Several updated Monte Carlo (MC) codes are available to perform calculations of voxel S values for radionuclide targeted therapy. The aim of this work is to analyze the differences in the calculations obtained by different MC codes and their impact on absorbed dose evaluations performed by voxel dosimetry. Voxel S values for monoenergetic sources (electrons and photons) and different radionuclides ({sup 90}Y, {sup 131}I, and {sup 188}Re) were calculated. Simulations were performed in soft tissue. Three general-purpose MC codes were employed for simulating radiation transport: MCNP4C, EGSnrc, and GEANT4. The data published by the MIRD Committee in Pamphlet No. 17, obtained with the EGS4 MC code, were also included in the comparisons. The impact of the differences (in terms of voxel S values) among the MC codes was also studied by convolution calculations of the absorbed dose in a volume of interest. For uniform activity distribution of a given radionuclide, dose calculations were performed on spherical and elliptical volumes, varying the mass from 1 to 500 g. For simulations with monochromatic sources, differences for self-irradiation voxel S values were mostly confined within 10% for both photons and electrons, but with electron energy less than 500 keV, the voxel S values referred to the first neighbor voxels showed large differences (up to 130%, with respect to EGSnrc) among the updated MC codes. For radionuclide simulations, noticeable differences arose in voxel S values, especially in the bremsstrahlung tails, or when a high contribution from electrons with energy of less than 500 keV is involved. In particular, for {sup 90}Y the updated codes showed a remarkable divergence in the bremsstrahlung region (up to about 90% in terms of voxel S values) with respect to the EGS4 code. Further, variations were observed up to about 30%, for small source-target voxel distances, when low-energy electrons cover an important part of the emission spectrum of the radionuclide

  10. SU-E-CAMPUS-I-02: Estimation of the Dosimetric Error Caused by the Voxelization of Hybrid Computational Phantoms Using Triangle Mesh-Based Monte Carlo Transport

    Energy Technology Data Exchange (ETDEWEB)

    Lee, C [Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD (United States); Badal, A [U.S. Food ' Drug Administration (CDRH/OSEL), Silver Spring, MD (United States)

    2014-06-15

    Purpose: Computational voxel phantom provides realistic anatomy but the voxel structure may result in dosimetric error compared to real anatomy composed of perfect surface. We analyzed the dosimetric error caused from the voxel structure in hybrid computational phantoms by comparing the voxel-based doses at different resolutions with triangle mesh-based doses. Methods: We incorporated the existing adult male UF/NCI hybrid phantom in mesh format into a Monte Carlo transport code, penMesh that supports triangle meshes. We calculated energy deposition to selected organs of interest for parallel photon beams with three mono energies (0.1, 1, and 10 MeV) in antero-posterior geometry. We also calculated organ energy deposition using three voxel phantoms with different voxel resolutions (1, 5, and 10 mm) using MCNPX2.7. Results: Comparison of organ energy deposition between the two methods showed that agreement overall improved for higher voxel resolution, but for many organs the differences were small. Difference in the energy deposition for 1 MeV, for example, decreased from 11.5% to 1.7% in muscle but only from 0.6% to 0.3% in liver as voxel resolution increased from 10 mm to 1 mm. The differences were smaller at higher energies. The number of photon histories processed per second in voxels were 6.4×10{sup 4}, 3.3×10{sup 4}, and 1.3×10{sup 4}, for 10, 5, and 1 mm resolutions at 10 MeV, respectively, while meshes ran at 4.0×10{sup 4} histories/sec. Conclusion: The combination of hybrid mesh phantom and penMesh was proved to be accurate and of similar speed compared to the voxel phantom and MCNPX. The lowest voxel resolution caused a maximum dosimetric error of 12.6% at 0.1 MeV and 6.8% at 10 MeV but the error was insignificant in some organs. We will apply the tool to calculate dose to very thin layer tissues (e.g., radiosensitive layer in gastro intestines) which cannot be modeled by voxel phantoms.

  11. Gray Matter Volume Decreases in Elderly Patients with Schizophrenia: A Voxel-based Morphometry Study

    Science.gov (United States)

    Schuster, Caroline; Schuller, Anne Marie; Paulos, Carlos; Namer, Izzie; Pull, Charles; Danion, Jean Marie; Foucher, Jack René

    2012-01-01

    Background: Aged patients (>50 years old) with residual schizophrenic symptoms differ from young patients. They represent a subpopulation with a more unfavorable Kraepelinian course and have an increased risk (up to 30%) for dementia of unknown origin. However, our current understanding of age-related brain changes in schizophrenia is derived from studies that included less than 17% of patients who were older than 50 years of age. This study investigated the anatomical distribution of gray matter (GM) brain deficits in aged patients with ongoing schizophrenia. Methods: Voxel-based morphometry was applied to 3D-T1 magnetic resonance images obtained from 27 aged patients with schizophrenia (mean age of 60 years) and 40 age-matched normal controls. Results: Older patients with schizophrenia showed a bilateral reduction of GM volume in the thalamus, the prefrontal cortex, and in a large posterior region centered on the occipito-temporo-parietal junction. Only the latter region showed accelerated GM volume loss with increasing age. None of these results could be accounted for by institutionalization, antipsychotic medication, or cognitive scores. Conclusions: This study replicated most common findings in patients with schizophrenia with regard to thalamic and frontal GM deficits. However, it uncovered an unexpected large region of GM atrophy in the posterior tertiary cortices. The latter observation may be specific to this aged and chronically symptomatic subpopulation, as atrophy in this region is rarely reported in younger patients and is accelerated with age. PMID:21205677

  12. The Neuroanatomical Basis of Panic Disorder and Social Phobia in Schizophrenia: A Voxel Based Morphometric Study

    Science.gov (United States)

    Picado, Marisol; Carmona, Susanna; Hoekzema, Elseline; Pailhez, Guillem; Bergé, Daniel; Mané, Anna; Fauquet, Jordi; Hilferty, Joseph; Moreno, Ana; Cortizo, Romina; Vilarroya, Oscar; Bulbena, Antoni

    2015-01-01

    Objective It is known that there is a high prevalence of certain anxiety disorders among schizophrenic patients, especially panic disorder and social phobia. However, the neural underpinnings of the comorbidity of such anxiety disorders and schizophrenia remain unclear. Our study aims to determine the neuroanatomical basis of the co-occurrence of schizophrenia with panic disorder and social phobia. Methods Voxel-based morphometry was used in order to examine brain structure and to measure between-group differences, comparing magnetic resonance images of 20 anxious patients, 20 schizophrenic patients, 20 schizophrenic patients with comorbid anxiety, and 20 healthy control subjects. Results Compared to the schizophrenic patients, we observed smaller grey-matter volume (GMV) decreases in the dorsolateral prefrontal cortex and precentral gyrus in the schizophrenic-anxiety group. Additionally, the schizophrenic group showed significantly reduced GMV in the dorsolateral prefrontal cortex, precentral gyrus, orbitofrontal cortex, temporal gyrus and angular/inferior parietal gyrus when compared to the control group. Conclusions Our findings suggest that the comorbidity of schizophrenia with panic disorder and social phobia might be characterized by specific neuroanatomical and clinical alterations that may be related to maladaptive emotion regulation related to anxiety. Even thought our findings need to be replicated, our study suggests that the identification of neural abnormalities involved in anxiety, schizophrenia and schizophrenia-anxiety may lead to an improved diagnosis and management of these conditions. PMID:25774979

  13. Srna-Monte Carlo codes for proton transport simulation in combined and voxelized geometries

    CERN Document Server

    Ilic, R D; Stankovic, S J

    2002-01-01

    This paper describes new Monte Carlo codes for proton transport simulations in complex geometrical forms and in materials of different composition. The SRNA codes were developed for three dimensional (3D) dose distribution calculation in proton therapy and dosimetry. The model of these codes is based on the theory of proton multiple scattering and a simple model of compound nucleus decay. The developed package consists of two codes: SRNA-2KG and SRNA-VOX. The first code simulates proton transport in combined geometry that can be described by planes and second order surfaces. The second one uses the voxelized geometry of material zones and is specifically adopted for the application of patient computer tomography data. Transition probabilities for both codes are given by the SRNADAT program. In this paper, we will present the models and algorithms of our programs, as well as the results of the numerical experiments we have carried out applying them, along with the results of proton transport simulation obtaine...

  14. Regional brain structural abnormality in ischemic stroke patients:a voxel-based morphometry study

    Institute of Scientific and Technical Information of China (English)

    Ping Wu; Lin Chen; Lin Bai; Juan Nie; San Zhang; Yan Xiong; Yu Bai; Can-xin Yin; Fan-rong Liang; Yu-mei Zhou; Fang Zeng; Zheng-jie Li; Lu Luo; Yong-xin Li; Wei Fan; Li-hua Qiu; Wei Qin

    2016-01-01

    Our previous study used regional homogeneity analysis and found that activity in some brain areas of patients with ischemic stroke changed signiifcantly. In the current study, we examined structural changes in these brain regions by taking structural magnetic resonance imaging scans of 11 ischemic stroke patients and 15 healthy participants, and analyzing the data using voxel-based morphometry. Compared with healthy participants, patients exhibited higher gray matter density in the left inferior occipital gyrus and right anterior white matter tract. In contrast, gray matter density in the right cerebellum, left precentral gyrus, right middle frontal gyrus, and left middle temporal gyrus was less in ischemic stroke patients. The changes of gray matter density in the middle frontal gyrus were negatively associated with the clin-ical rating scales of the Fugl-Meyer Motor Assessment (r = –0.609,P = 0.047) and the left middle temporal gyrus was negatively correlated with the clinical rating scales of the nervous functional deifciency scale (r = –0.737,P = 0.010). Our ifndings can objectively identify the functional abnormality in some brain regions of ischemic stroke patients.

  15. Regional brain structural abnormality in ischemic stroke patients: a voxel-based morphometry study

    Directory of Open Access Journals (Sweden)

    Ping Wu

    2016-01-01

    Full Text Available Our previous study used regional homogeneity analysis and found that activity in some brain areas of patients with ischemic stroke changed significantly. In the current study, we examined structural changes in these brain regions by taking structural magnetic resonance imaging scans of 11 ischemic stroke patients and 15 healthy participants, and analyzing the data using voxel-based morphometry. Compared with healthy participants, patients exhibited higher gray matter density in the left inferior occipital gyrus and right anterior white matter tract. In contrast, gray matter density in the right cerebellum, left precentral gyrus, right middle frontal gyrus, and left middle temporal gyrus was less in ischemic stroke patients. The changes of gray matter density in the middle frontal gyrus were negatively associated with the clinical rating scales of the Fugl-Meyer Motor Assessment (r = -0.609, P = 0.047 and the left middle temporal gyrus was negatively correlated with the clinical rating scales of the nervous functional deficiency scale (r = -0.737, P = 0.010. Our findings can objectively identify the functional abnormality in some brain regions of ischemic stroke patients.

  16. Brain correlates of pro-social personality traits: a voxel-based morphometry study.

    Science.gov (United States)

    Coutinho, Joana F; Sampaio, Adriana; Ferreira, Miguel; Soares, José M; Gonçalves, Oscar F

    2013-09-01

    Of the five personality dimensions described by the Big Five Personality Model (Costa and McCrae 1992), Extraversion and Agreeableness are the traits most commonly associated with a pro-social orientation. In this study we tested whether a pro-social orientation, as expressed in terms of Extraversion and Agreeableness, is associated with a specific grey matter phenotype. Fifty-two healthy participants underwent magnetic resonance imaging (MRI) and completed the NEO-Five Factor Inventory (NEO-FFI), a self-report measure of the Big Five personality traits. Voxel-based morphometry (VBM) was used to investigate the correlation between brain structure and the personality traits of Agreeableness and Extraversion. We found that Extraversion was negatively correlated with grey matter density in the middle frontal and orbitofrontal gyri while Agreeableness was negatively correlated with grey matter density in the inferior parietal, middle occipital and posterior cingulate gyri. No positive correlations were found. These results suggest that pro-social personality traits seem to be associated with decreases in grey matter density in more frontal regions for Extraversion, and more posterior regions for Agreeableness.

  17. Analytical calculation of proton linear energy transfer in voxelized geometries including secondary protons.

    Science.gov (United States)

    Sanchez-Parcerisa, D; Cortés-Giraldo, M A; Dolney, D; Kondrla, M; Fager, M; Carabe, A

    2016-02-21

    In order to integrate radiobiological modelling with clinical treatment planning for proton radiotherapy, we extended our in-house treatment planning system FoCa with a 3D analytical algorithm to calculate linear energy transfer (LET) in voxelized patient geometries. Both active scanning and passive scattering delivery modalities are supported. The analytical calculation is much faster than the Monte-Carlo (MC) method and it can be implemented in the inverse treatment planning optimization suite, allowing us to create LET-based objectives in inverse planning. The LET was calculated by combining a 1D analytical approach including a novel correction for secondary protons with pencil-beam type LET-kernels. Then, these LET kernels were inserted into the proton-convolution-superposition algorithm in FoCa. The analytical LET distributions were benchmarked against MC simulations carried out in Geant4. A cohort of simple phantom and patient plans representing a wide variety of sites (prostate, lung, brain, head and neck) was selected. The calculation algorithm was able to reproduce the MC LET to within 6% (1 standard deviation) for low-LET areas (under 1.7 keV μm(-1)) and within 22% for the high-LET areas above that threshold. The dose and LET distributions can be further extended, using radiobiological models, to include radiobiological effectiveness (RBE) calculations in the treatment planning system. This implementation also allows for radiobiological optimization of treatments by including RBE-weighted dose constraints in the inverse treatment planning process.

  18. Voxel-Based Morphometric Study on Chinese Blind Men's Brain Structure

    Institute of Scientific and Technical Information of China (English)

    YANG Chun-lan; PAN Wen-ju; ZHENG Lian

    2007-01-01

    Many studies have shown the functional relevance of cross-modal plasticity in blind men.In order to study the changes of their brain structure,voxel-based morphometry (VBM) methods are used.The regional gray matter (GM) and white matter (WM) concentrations of magnetic resonance (MR) images from 11 blind people and 9 sighted control subjects are compared using standard VBM.Optimized VBM is also discussed to measure the absolute local volume of GM or WM.Consistent results are achieved by statistical analysis with these methods.There are distinct differences not only in visual cortex but also the sensory area,auditory area and motor area.GM concentrations in blind men significantly decreased in Brodmann 7 and 22.While in Brodmann 18 and 19,GM concentration increased.GM volumes decreased in Brodmann 3,4,6,9 and 45.On the other hand,both WM concentration and volume increased in Brodmann 7.These results suggest that early visual deprivation can lead to changes in the brain structural anatomy which is consistent with the cortical cross-modal reorganization found by functional imaging.It may help to discover the relationship between the brain structural anatomy and the brain functional data of blind men at a macroscopic level from neuroimaging perspective.

  19. Focal retrograde amnesia: voxel-based morphometry findings in a case without MRI lesions.

    Directory of Open Access Journals (Sweden)

    Bernhard Sehm

    Full Text Available Focal retrograde amnesia (FRA is a rare neurocognitive disorder presenting with an isolated loss of retrograde memory. In the absence of detectable brain lesions, a differentiation of FRA from psychogenic causes is difficult. Here we report a case study of persisting FRA after an epileptic seizure. A thorough neuropsychological assessment confirmed severe retrograde memory deficits while anterograde memory abilities were completely normal. Neurological and psychiatric examination were unremarkable and high-resolution MRI showed no neuroradiologically apparent lesion. However, voxel-based morphometry (VBM-comparing the MRI to an education-, age-and sex-matched control group (n = 20 disclosed distinct gray matter decreases in left temporopolar cortex and a region between right posterior parahippocampal and lingual cortex. Although the results of VBM-based comparisons between a single case and a healthy control group are generally susceptible to differences unrelated to the specific symptoms of the case, we believe that our data suggest a causal role of the cortical areas detected since the retrograde memory deficit is the preeminent neuropsychological difference between patient and controls. This was paralleled by grey matter differences in central nodes of the retrograde memory network. We therefore suggest that these subtle alterations represent structural correlates of the focal retrograde amnesia in our patient. Beyond the implications for the diagnosis and etiology of FRA, our results advocate the use of VBM in conditions that do not show abnormalities in clinical radiological assessment, but show distinct neuropsychological deficits.

  20. Parallel solutions for voxel-based simulations of reaction-diffusion systems.

    Science.gov (United States)

    D'Agostino, Daniele; Pasquale, Giulia; Clematis, Andrea; Maj, Carlo; Mosca, Ettore; Milanesi, Luciano; Merelli, Ivan

    2014-01-01

    There is an increasing awareness of the pivotal role of noise in biochemical processes and of the effect of molecular crowding on the dynamics of biochemical systems. This necessity has given rise to a strong need for suitable and sophisticated algorithms for the simulation of biological phenomena taking into account both spatial effects and noise. However, the high computational effort characterizing simulation approaches, coupled with the necessity to simulate the models several times to achieve statistically relevant information on the model behaviours, makes such kind of algorithms very time-consuming for studying real systems. So far, different parallelization approaches have been deployed to reduce the computational time required to simulate the temporal dynamics of biochemical systems using stochastic algorithms. In this work we discuss these aspects for the spatial TAU-leaping in crowded compartments (STAUCC) simulator, a voxel-based method for the stochastic simulation of reaction-diffusion processes which relies on the Sτ-DPP algorithm. In particular we present how the characteristics of the algorithm can be exploited for an effective parallelization on the present heterogeneous HPC architectures.

  1. Regional gray matter density associated with emotional intelligence: evidence from voxel-based morphometry.

    Science.gov (United States)

    Takeuchi, Hikaru; Taki, Yasuyuki; Sassa, Yuko; Hashizume, Hiroshi; Sekiguchi, Atsushi; Fukushima, Ai; Kawashima, Ryuta

    2011-09-01

    Emotional Intelligence (EI) is the ability to monitor one's own and others' emotions and the ability to use the gathered information to guide one's thinking and action. EI is thought to be important for social life making it a popular subject of research. However, despite the existence of previous functional imaging studies on EI, the relationship between regional gray matter morphology and EI has never been investigated. We used voxel-based morphometry (VBM) and a questionnaire (Emotional Intelligence Scale) to measure EI to identify the gray matter correlates of each factor of individual EI (Intrapersonal factor, Interpersonal factor, Situation Management factor). We found significant negative relationships between the Intrapersonal factor and regional gray matter density (rGMD) (1-a) in an anatomical cluster that included the right anterior insula, (1-b) in the right cerebellum, (1-c) in an anatomical cluster that extends from the cuneus to the precuneus, (1-d) and in an anatomical cluster that extends from the medial prefrontal cortex to the left lateral fronto-polar cortex. We also found significant positive correlations between the Interpersonal factor and rGMD in the right superior temporal sulcus, and significant negative correlations between the Situation Management factor and rGMD in the ventromedial prefrontal cortex. These findings suggest that each factor of EI in healthy young people is related to the specific brain regions known to be involved in the networks of social cognition and self-related recognition, and in the somatic marker circuitry.

  2. Mapping the brain in type II diabetes: Voxel-based morphometry using DARTEL

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhiye [Department of Radiology, PLA General Hospital, 28 Fuxing Road, Beijing 100853 (China); Li, Lin [Department of Geriatric Endocrinology, PLA General Hospital, Beijing 100853 (China); Sun, Jie [Department of Endocrinology, PLA General Hospital, Beijing 100853 (China); Ma, Lin, E-mail: cjr.malin@vip.163.com [Department of Radiology, PLA General Hospital, 28 Fuxing Road, Beijing 100853 (China)

    2012-08-15

    Purpose: To investigate the pattern of brain volume changes of the brain in patients with type II diabetes mellitus using voxel-based morphometry. Material and methods: Institutional ethics approval and informed consent were obtained. VBM based on the high resolution three-dimensional T1-weighted fast spoiled gradient recalled echo MRI images was obtained from 16 type II diabetes patients (mean age 61.2 years) and 16 normal controls (mean age 59.6 years). All images were spatially preprocessed using Diffeomorphic Anatomical Registration using Exponentiated Lie algebra (DARTEL) algorithm, and the DARTEL templates were made from 100 normal subjects. Statistical parametric mapping was generated using analysis of covariance (ANCOVA). Results: An atrophy pattern of gray matter was seen in type II diabetes patients compared with controls that involved the right superior, middle, and inferior temporal gyri, right precentral gyrus, and left rolandic operculum region. The loss of white matter volume in type II diabetes mellitus was observed in right temporal lobe and left inferior frontal triangle region. ROI analysis revealed that the gray and white matter volume of right temporal lobe were significant lower in type II diabetes mellitus than that in controls (P < 0.05). Conclusion: This work demonstrated that type II diabetes mellitus patients mainly exhibited gray and white matter atrophy in right temporal lobe, and this finding supported that type II diabetes mellitus could lead to subtle diabetic brain structural changes in patients without dementia or macrovascular complications.

  3. Neurostructural correlates of two subtypes of specific phobia: a voxel-based morphometry study.

    Science.gov (United States)

    Hilbert, Kevin; Evens, Ricarda; Maslowski, Nina Isabel; Wittchen, Hans-Ulrich; Lueken, Ulrike

    2015-02-28

    The animal and blood-injection-injury (BII) subtypes of specific phobia are both characterized by subjective fear but distinct autonomic reactions to threat. Previous functional neuroimaging studies have related these characteristic responses to shared and non-shared neural underpinnings. However, no comparative structural data are available. This study aims to fill this gap by comparing the two subtypes and also comparing them with a non-phobic control group. Gray and white matter data of 33 snake phobia subjects (SP), 26 dental phobia subjects (DP), and 37 healthy control (HC) subjects were analyzed with voxel-based morphometry. Especially DP differed from HC and SP by showing significantly increased grey matter volumes in widespread areas including the right subgenual anterior cingulate gyrus, left insula, left orbitofrontal and left prefrontal (PFC) cortices. In addition, white matter volume was significantly increased in the left PFC in DP compared with SP. These results are in line with functional changes observed in dental phobia and point toward those brain circuits associated with emotional processing and regulation. Future studies should aim to further delineate functional and structural connectivity alterations in specific phobia.

  4. The neuroanatomical basis of panic disorder and social phobia in schizophrenia: a voxel based morphometric study.

    Directory of Open Access Journals (Sweden)

    Marisol Picado

    Full Text Available It is known that there is a high prevalence of certain anxiety disorders among schizophrenic patients, especially panic disorder and social phobia. However, the neural underpinnings of the comorbidity of such anxiety disorders and schizophrenia remain unclear. Our study aims to determine the neuroanatomical basis of the co-occurrence of schizophrenia with panic disorder and social phobia.Voxel-based morphometry was used in order to examine brain structure and to measure between-group differences, comparing magnetic resonance images of 20 anxious patients, 20 schizophrenic patients, 20 schizophrenic patients with comorbid anxiety, and 20 healthy control subjects.Compared to the schizophrenic patients, we observed smaller grey-matter volume (GMV decreases in the dorsolateral prefrontal cortex and precentral gyrus in the schizophrenic-anxiety group. Additionally, the schizophrenic group showed significantly reduced GMV in the dorsolateral prefrontal cortex, precentral gyrus, orbitofrontal cortex, temporal gyrus and angular/inferior parietal gyrus when compared to the control group.Our findings suggest that the comorbidity of schizophrenia with panic disorder and social phobia might be characterized by specific neuroanatomical and clinical alterations that may be related to maladaptive emotion regulation related to anxiety. Even thought our findings need to be replicated, our study suggests that the identification of neural abnormalities involved in anxiety, schizophrenia and schizophrenia-anxiety may lead to an improved diagnosis and management of these conditions.

  5. Cancer risk estimation in Digital Breast Tomosynthesis using GEANT4 Monte Carlo simulations and voxel phantoms.

    Science.gov (United States)

    Ferreira, P; Baptista, M; Di Maria, S; Vaz, P

    2016-05-01

    The aim of this work was to estimate the risk of radiation induced cancer following the Portuguese breast screening recommendations for Digital Mammography (DM) when applied to Digital Breast Tomosynthesis (DBT) and to evaluate how the risk to induce cancer could influence the energy used in breast diagnostic exams. The organ doses were calculated by Monte Carlo simulations using a female voxel phantom and considering the acquisition of 25 projection images. Single organ cancer incidence risks were calculated in order to assess the total effective radiation induced cancer risk. The screening strategy techniques considered were: DBT in Cranio-Caudal (CC) view and two-view DM (CC and Mediolateral Oblique (MLO)). The risk of cancer incidence following the Portuguese screening guidelines (screening every two years in the age range of 50-80years) was calculated by assuming a single CC DBT acquisition view as standalone screening strategy and compared with two-view DM. The difference in the total effective risk between DBT and DM is quite low. Nevertheless in DBT an increase of risk for the lung is observed with respect to DM. The lung is also the organ that is mainly affected when non-optimal beam energy (in terms of image quality and absorbed dose) is used instead of an optimal one. The use of non-optimal energies could increase the risk of lung cancer incidence by a factor of about 2.

  6. Grey matter abnormalities in untreated hyperthyroidism: A voxel-based morphometry study using the DARTEL approach

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wei, E-mail: will.zhang.1111@gmail.com [Department of Radiology, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China); Department of Radiology, Sichuan Provincial Corps Hospital, Chinese People' s Armed Police Forces, Leshan 614000 (China); Song, Lingheng, E-mail: songlh1023@hotmail.com [Department of Radiology, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China); Department of Radiology, No. 324 Hospital of PLA, Chongqing 400020 (China); Yin, Xuntao, E-mail: xuntaoyin@gmail.com [Department of Radiology, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China); Zhang, Jiuquan, E-mail: jiuquanzhang@yahoo.com [Department of Radiology, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China); Liu, Chen, E-mail: cqliuchen@foxmail.com [Department of Radiology, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China); Wang, Jian, E-mail: wangjian_811@yahoo.com [Department of Radiology, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China); Zhou, Daiquan, E-mail: zhoudq77@sina.com [Department of Radiology, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China); Chen, Bing, E-mail: chenbing3@medmail.com.cn [Department of Endocrinology, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China); Lii, Haitao, E-mail: haitaolii023@gmail.com [Department of Radiology, Southwest Hospital, Third Military Medical University, Chongqing 400038 (China)

    2014-01-15

    Objective: Hyperthyroidism is frequently associated with pronounced neuropsychiatric symptoms such as impulsiveness, irritability, poor concentration, and memory impairments. Functional neuroimaging has revealed changes in cerebral metabolism in hyperthyroidism, but regional changes in cortical morphology associated with specific neurological deficits have not been studied so far. To investigate the pathophysiology underlying hyperthyroid-associated neural dysfunction, we compared grey matter volume (GMV) between adult hyperthyroid patients and matched healthy controls using voxel-based morphometry (VBM). Materials and methods: High resolution 3D T1-weighted images were acquired by 3T MRI from 51 hyperthyroid patients and 51 controls. VBM analysis was performed using SPM8. Correlations between regional GMV and both serum free thyroid hormone (TH) concentrations and disease duration were assessed by multiple regression analysis. Results: Compared to controls, GM volumes in the bilateral hippocampus, parahippocampal gyrus, calcarine, lingual gyrus, and left temporal pole were lower and bilateral supplementary motor area GMV higher in hyperthyroid patients. Serum free triiodothyronine (FT3) concentration was negatively correlated with the normalized regional volume (NRV) of the left parahippocampal gyrus and serum free thyroxine (FT4) concentration negatively correlated with the NRV of the left hippocampus and right parahippocampal gyrus. Disease duration was negatively correlated with the NRV of the left hippocampus, bilateral parahippocampal gyrus, and left temporal pole. Conclusion: Hyperthyroid patients exhibited reduced GMV in regions associated with memory, attention, emotion, vision, and motor planning. Negative correlations between GMV and both free TH and disease duration suggest that chronic TH elevation induces abnormalities in the adult cortex.

  7. Parallel Solutions for Voxel-Based Simulations of Reaction-Diffusion Systems

    Science.gov (United States)

    D'Agostino, Daniele; Pasquale, Giulia; Clematis, Andrea; Maj, Carlo; Mosca, Ettore; Milanesi, Luciano; Merelli, Ivan

    2014-01-01

    There is an increasing awareness of the pivotal role of noise in biochemical processes and of the effect of molecular crowding on the dynamics of biochemical systems. This necessity has given rise to a strong need for suitable and sophisticated algorithms for the simulation of biological phenomena taking into account both spatial effects and noise. However, the high computational effort characterizing simulation approaches, coupled with the necessity to simulate the models several times to achieve statistically relevant information on the model behaviours, makes such kind of algorithms very time-consuming for studying real systems. So far, different parallelization approaches have been deployed to reduce the computational time required to simulate the temporal dynamics of biochemical systems using stochastic algorithms. In this work we discuss these aspects for the spatial TAU-leaping in crowded compartments (STAUCC) simulator, a voxel-based method for the stochastic simulation of reaction-diffusion processes which relies on the Sτ-DPP algorithm. In particular we present how the characteristics of the algorithm can be exploited for an effective parallelization on the present heterogeneous HPC architectures. PMID:25045716

  8. Parallel Solutions for Voxel-Based Simulations of Reaction-Diffusion Systems

    Directory of Open Access Journals (Sweden)

    Daniele D’Agostino

    2014-01-01

    Full Text Available There is an increasing awareness of the pivotal role of noise in biochemical processes and of the effect of molecular crowding on the dynamics of biochemical systems. This necessity has given rise to a strong need for suitable and sophisticated algorithms for the simulation of biological phenomena taking into account both spatial effects and noise. However, the high computational effort characterizing simulation approaches, coupled with the necessity to simulate the models several times to achieve statistically relevant information on the model behaviours, makes such kind of algorithms very time-consuming for studying real systems. So far, different parallelization approaches have been deployed to reduce the computational time required to simulate the temporal dynamics of biochemical systems using stochastic algorithms. In this work we discuss these aspects for the spatial TAU-leaping in crowded compartments (STAUCC simulator, a voxel-based method for the stochastic simulation of reaction-diffusion processes which relies on the Sτ-DPP algorithm. In particular we present how the characteristics of the algorithm can be exploited for an effective parallelization on the present heterogeneous HPC architectures.

  9. MRI Correlates of Parkinson’s Disease Progression: A Voxel Based Morphometry Study

    Directory of Open Access Journals (Sweden)

    Valentina Fioravanti

    2015-01-01

    Full Text Available We investigated structural brain differences between a group of early-mild PD patients at different phases of the disease and healthy subjects using voxel-based morphometry (VBM. 20 mild PD patients compared to 15 healthy at baseline and after 2 years of follow-up. VBM is a fully automated technique, which allows the identification of regional differences in the gray matter enabling an objective analysis of the whole brain between groups of subjects. With respect to controls, PD patients exhibited decreased GM volumes in right putamen and right parietal cortex. After 2 years of disease, the same patients confirmed GM loss in the putamen and parietal cortex; a significant difference was also observed in the area of pedunculopontine nucleus (PPN and in the mesencephalic locomotor region (MLR. PD is associated with brain morphological changes in cortical and subcortical structures. The first regions to be affected in PD seem to be the parietal cortex and the putamen. A third structure that undergoes atrophy is the part of the inferior-posterior midbrain, attributable to the PPN and MLR. Our findings provide new insight into the brain involvement in PD and could contribute to a better understanding of the sequence of events occurring in these patients.

  10. Voxel-based morphometry to detect brain atrophy in progressive mild cognitive impairment.

    Science.gov (United States)

    Hämäläinen, Anne; Tervo, Susanna; Grau-Olivares, Marta; Niskanen, Eini; Pennanen, Corina; Huuskonen, Jari; Kivipelto, Miia; Hänninen, Tuomo; Tapiola, Mia; Vanhanen, Matti; Hallikainen, Merja; Helkala, Eeva-Liisa; Nissinen, Aulikki; Vanninen, Ritva; Soininen, Hilkka

    2007-10-01

    Recent research has shown an increased rate of conversion to dementia in subjects with mild cognitive impairment (MCI) compared to controls. However, there are no specific methods to predict who will later develop dementia. In the present study, 22 controls and 56 MCI subjects were followed on average for 37 months (max. 60 months) and studied with magnetic resonance imaging (MRI) at baseline to assess changes in brain structure associated to later progression to dementia. Voxel-based morphometry (VBM) was used to investigate gray matter atrophy. During the follow-up, 13 subjects progressed to dementia. At baseline, no differences were detected in age or education between the control and MCI subjects, but they differed by several neuropsychological tests. The stable and progressive MCI subjects differed only by CDR sum of boxes scores and delayed verbal recall, which were also significant predictors of conversion to dementia. At the baseline imaging, the MCI subjects showed reduced gray matter density in medial temporal, temporoparietal as well as in frontal cortical areas compared to controls. Interestingly, the progressive MCI subjects showed atrophy in the left temporoparietal and posterior cingulate cortices and in the precuneus bilaterally, and a trend for hippocampal atrophy when compared to the stable MCI subjects. We conclude that widespread cortical atrophy is present already two and a half years before a clinical diagnosis of dementia can be set.

  11. An automatic framework for quantitative validation of voxel based morphometry measures of anatomical brain asymmetry.

    Science.gov (United States)

    Pepe, Antonietta; Dinov, Ivo; Tohka, Jussi

    2014-10-15

    The study of anatomical brain asymmetries has been a topic of great interest in the neuroimaging community in the past decades. However, the accuracy of brain asymmetry measurements has been rarely investigated. In this study, we propose a fully automatic methodology for the quantitative validation of brain tissue asymmetries as measured by Voxel Based Morphometry (VBM) from structural magnetic resonance (MR) images. Starting from a real MR image, the methodology generates simulated 3D MR images with a known and realistic pattern of inter-hemispheric asymmetry that models the left-occipital right-frontal petalia of a normal brain and the related rightward bending of the inter-hemispheric fissure. As an example, we generated a dataset of 64 simulated MR images and applied this dataset for the quantitative validation of optimized VBM measures of asymmetries in brain tissue composition. Our results suggested that VBM analysis strongly depended on the spatial normalization of the individual brain images, the selected template space, and the amount of spatial smoothing applied. The most accurate asymmetry detections were achieved by 9-degrees of freedom registration to the symmetrical template space with 4 to 8mm spatial smoothing.

  12. Neural correlates of post-conventional moral reasoning: a voxel-based morphometry study.

    Science.gov (United States)

    Prehn, Kristin; Korczykowski, Marc; Rao, Hengyi; Fang, Zhuo; Detre, John A; Robertson, Diana C

    2015-01-01

    Going back to Kohlberg, moral development research affirms that people progress through different stages of moral reasoning as cognitive abilities mature. Individuals at a lower level of moral reasoning judge moral issues mainly based on self-interest (personal interests schema) or based on adherence to laws and rules (maintaining norms schema), whereas individuals at the post-conventional level judge moral issues based on deeper principles and shared ideals. However, the extent to which moral development is reflected in structural brain architecture remains unknown. To investigate this question, we used voxel-based morphometry and examined the brain structure in a sample of 67 Master of Business Administration (MBA) students. Subjects completed the Defining Issues Test (DIT-2) which measures moral development in terms of cognitive schema preference. Results demonstrate that subjects at the post-conventional level of moral reasoning were characterized by increased gray matter volume in the ventromedial prefrontal cortex and subgenual anterior cingulate cortex, compared with subjects at a lower level of moral reasoning. Our findings support an important role for both cognitive and emotional processes in moral reasoning and provide first evidence for individual differences in brain structure according to the stages of moral reasoning first proposed by Kohlberg decades ago.

  13. Neural correlates of post-conventional moral reasoning: a voxel-based morphometry study.

    Directory of Open Access Journals (Sweden)

    Kristin Prehn

    Full Text Available Going back to Kohlberg, moral development research affirms that people progress through different stages of moral reasoning as cognitive abilities mature. Individuals at a lower level of moral reasoning judge moral issues mainly based on self-interest (personal interests schema or based on adherence to laws and rules (maintaining norms schema, whereas individuals at the post-conventional level judge moral issues based on deeper principles and shared ideals. However, the extent to which moral development is reflected in structural brain architecture remains unknown. To investigate this question, we used voxel-based morphometry and examined the brain structure in a sample of 67 Master of Business Administration (MBA students. Subjects completed the Defining Issues Test (DIT-2 which measures moral development in terms of cognitive schema preference. Results demonstrate that subjects at the post-conventional level of moral reasoning were characterized by increased gray matter volume in the ventromedial prefrontal cortex and subgenual anterior cingulate cortex, compared with subjects at a lower level of moral reasoning. Our findings support an important role for both cognitive and emotional processes in moral reasoning and provide first evidence for individual differences in brain structure according to the stages of moral reasoning first proposed by Kohlberg decades ago.

  14. D-optimal design of b-values for accurate intra-voxel incoherent motion imaging

    CERN Document Server

    Sansone, Mario; Petrillo, Antonella

    2016-01-01

    The aim of this paper is to optimally design the set of b-values for diffusion weighted MRI with the aim of accurate estimation of intra- voxel incoherent motion (IVIM) parameters (f perfusion fraction, Ds slow diffusion, Df fast diffusion) according to the model developed by Le Bihan. Previous studies have addressed the design in a Monte Carlo fash- ion. Due to huge computation times, this approach is feasible only for a limited number of values of the parameters (local design): however, as the parameters of a specific exam are not known a priori, it would be desirable to optimise b-values over a region of parameters. In order to overcome this issue, we propose to use a D-optimal design approach. The optimal combination of b-values can be chosen from a candidate set of predefined values taken from the literature. Our study has two key results: first, the optimal design does not depend on perfusion fraction: this allow to perform a search over a 2D parameter space instead of 3D; second, as an exhaustive searc...

  15. Srna - Monte Carlo codes for proton transport simulation in combined and voxelized geometries

    Directory of Open Access Journals (Sweden)

    Ilić Radovan D.

    2002-01-01

    Full Text Available This paper describes new Monte Carlo codes for proton transport simulations in complex geometrical forms and in materials of different composition. The SRNA codes were developed for three dimensional (3D dose distribution calculation in proton therapy and dosimetry. The model of these codes is based on the theory of proton multiple scattering and a simple model of compound nucleus decay. The developed package consists of two codes: SRNA-2KG and SRNA-VOX. The first code simulates proton transport in combined geometry that can be described by planes and second order surfaces. The second one uses the voxelized geometry of material zones and is specifically adopted for the application of patient computer tomography data. Transition probabilities for both codes are given by the SRNADAT program. In this paper, we will present the models and algorithms of our programs, as well as the results of the numerical experiments we have carried out applying them, along with the results of proton transport simulation obtained through the PETRA and GEANT programs. The simulation of the proton beam characterization by means of the Multi-Layer Faraday Cup and spatial distribution of positron emitters obtained by our program indicate the imminent application of Monte Carlo techniques in clinical practice.

  16. Multi-voxel pattern analysis of fMRI data predicts clinical symptom severity.

    Science.gov (United States)

    Coutanche, Marc N; Thompson-Schill, Sharon L; Schultz, Robert T

    2011-07-01

    Multi-voxel pattern analysis (MVPA) has been applied successfully to a variety of fMRI research questions in healthy participants. The full potential of applying MVPA to functional data from patient groups has yet to be fully explored. Our goal in this study was to investigate whether MVPA might yield a sensitive predictor of patient symptoms. We also sought to demonstrate that this benefit can be realized from existing datasets, even when they were not designed with MVPA in mind. We analyzed data from an fMRI study of the neural basis for face processing in individuals with an Autism Spectrum Disorder (ASD), who often show fusiform gyrus hypoactivation when presented with unfamiliar faces, compared to controls. We found reliable correlations between MVPA classification performance and standardized measures of symptom severity that exceeded those observed using a univariate measure; a relation that was robust across variations in ROI definition. A searchlight analysis across the ventral temporal lobes identified regions with relationships between classification performance and symptom severity that were not detected using mean activation. These analyses illustrate that MVPA has the potential to act as a sensitive functional biomarker of patient severity.

  17. Microtomography with photon counting detectors: improving the quality of tomographic reconstruction by voxel-space oversampling

    Science.gov (United States)

    Dudak, J.; Zemlicka, J.; Karch, J.; Hermanova, Z.; Kvacek, J.; Krejci, F.

    2017-01-01

    Photon counting detectors Timepix are known for their unique properties enabling X-ray imaging with extremely high contrast-to-noise ratio. Their applicability has been recently further improved since a dedicated technique for assembling large area Timepix detector arrays was introduced. Despite the fact that the sensitive area of Timepix detectors has been significantly increased, the pixel pitch is kept unchanged (55 microns). This value is much larger compared to widely used and popular X-ray imaging cameras utilizing scintillation crystals and CCD-based read-out. On the other hand, photon counting detectors provide steeper point-spread function. Therefore, with given effective pixel size of an acquired radiography, Timepix detectors provide higher spatial resolution than X-ray cameras with scintillation-based devices unless the image is affected by penumbral blur. In this paper we take an advance of steep PSF of photon counting detectors and test the possibility to improve the quality of computed tomography reconstruction using finer sampling of reconstructed voxel space. The achieved results are presented in comparison with data acquired under the same conditions using a commercially available state-of-the-art CCD X-ray camera.

  18. Fully Automated Treatment Planning for Head and Neck Radiotherapy using a Voxel-Based Dose Prediction and Dose Mimicking Method

    CERN Document Server

    McIntosh, Chris; McNiven, Andrea; Jaffray, David A; Purdie, Thomas G

    2016-01-01

    Recent works in automated radiotherapy treatment planning have used machine learning based on historical treatment plans to infer the spatial dose distribution for a novel patient directly from the planning image. We present an atlas-based approach which learns a dose prediction model for each patient (atlas) in a training database, and then learns to match novel patients to the most relevant atlases. The method creates a spatial dose objective, which specifies the desired dose-per-voxel, and therefore replaces any requirement for specifying dose-volume objectives for conveying the goals of treatment planning. A probabilistic dose distribution is inferred from the most relevant atlases, and is scalarized using a conditional random field to determine the most likely spatial distribution of dose to yield a specific dose prior (histogram) for relevant regions of interest. Voxel-based dose mimicking then converts the predicted dose distribution to a deliverable treatment plan dose distribution. In this study, we ...

  19. Brain glucose metabolism is associated with hormone level in Cushing's disease: A voxel-based study using FDG-PET

    OpenAIRE

    Shuai Liu; Yinyan Wang; Kaibin Xu; Fan Ping; Renzhi Wang; Fang Li; Xin Cheng

    2016-01-01

    Chronic exposure to elevated levels of glucocorticoids can exert a neurotoxic effect in patients, possibly manifesting as molecular imaging alterations in patients. The aim of this study was to investigate the potential association between brain metabolism and elevated hormone level using 18F-fluorodeoxyglucose positron emission tomography. We retrospectively enrolled 92 consecutive patients with confirmed diagnosis of Cushing's disease. A voxel-based analysis was performed to investigate the...

  20. Local diffusion homogeneity (LDH): an inter-voxel diffusion MRI metric for assessing inter-subject white matter variability.

    Science.gov (United States)

    Gong, Gaolang

    2013-01-01

    Many diffusion parameters and indices (e.g., fractional anisotropy [FA] and mean diffusivity [MD]) have been derived from diffusion magnetic resonance imaging (MRI) data. These parameters have been extensively applied as imaging markers for localizing white matter (WM) changes under various conditions (e.g., development, degeneration and disease). However, the vast majority of the existing parameters is derived from intra-voxel analyses and represents the diffusion properties solely within the voxel unit. Other types of parameters that characterize inter-voxel relationships have been largely overlooked. In the present study, we propose a novel inter-voxel metric referred to as the local diffusion homogeneity (LDH). This metric quantifies the local coherence of water molecule diffusion in a model-free manner. It can serve as an additional marker for evaluating the WM microstructural properties of the brain. To assess the distinguishing features between LDH and FA/MD, the metrics were systematically compared across space and subjects. As an example, both the LDH and FA/MD metrics were applied to measure age-related WM changes. The results indicate that LDH reveals unique inter-subject variability in specific WM regions (e.g., cerebral peduncle, internal capsule and splenium). Furthermore, there are regions in which measurements of age-related WM alterations with the LDH and FA/MD metrics yield discrepant results. These findings suggest that LDH and FA/MD have different sensitivities to specific WM microstructural properties. Taken together, the present study shows that LDH is complementary to the conventional diffusion-MRI markers and may provide additional insights into inter-subject WM variability. Further studies, however, are needed to uncover the neuronal mechanisms underlying the LDH.

  1. Local diffusion homogeneity (LDH: an inter-voxel diffusion MRI metric for assessing inter-subject white matter variability.

    Directory of Open Access Journals (Sweden)

    Gaolang Gong

    Full Text Available Many diffusion parameters and indices (e.g., fractional anisotropy [FA] and mean diffusivity [MD] have been derived from diffusion magnetic resonance imaging (MRI data. These parameters have been extensively applied as imaging markers for localizing white matter (WM changes under various conditions (e.g., development, degeneration and disease. However, the vast majority of the existing parameters is derived from intra-voxel analyses and represents the diffusion properties solely within the voxel unit. Other types of parameters that characterize inter-voxel relationships have been largely overlooked. In the present study, we propose a novel inter-voxel metric referred to as the local diffusion homogeneity (LDH. This metric quantifies the local coherence of water molecule diffusion in a model-free manner. It can serve as an additional marker for evaluating the WM microstructural properties of the brain. To assess the distinguishing features between LDH and FA/MD, the metrics were systematically compared across space and subjects. As an example, both the LDH and FA/MD metrics were applied to measure age-related WM changes. The results indicate that LDH reveals unique inter-subject variability in specific WM regions (e.g., cerebral peduncle, internal capsule and splenium. Furthermore, there are regions in which measurements of age-related WM alterations with the LDH and FA/MD metrics yield discrepant results. These findings suggest that LDH and FA/MD have different sensitivities to specific WM microstructural properties. Taken together, the present study shows that LDH is complementary to the conventional diffusion-MRI markers and may provide additional insights into inter-subject WM variability. Further studies, however, are needed to uncover the neuronal mechanisms underlying the LDH.

  2. The KLOE Online Calibration System

    Institute of Scientific and Technical Information of China (English)

    E.Pasqualucci

    2001-01-01

    Based on all the features of the KLOE online software,the online calibration system performs current calibration quality checking in real time and starts automatically new calibration procedures when needed.Acalibration manager process controls the system,implementing the interface to the online system,receiving information from the run control and translating its state transitions to a separate state machine.It acts as a " calibration run controller"and performs failure recovery when requested by a set of process checkers.The core of the system is a multi-threaded OO histogram server that receives histogramming commands by remote processes and operates on local ROOT histograms.A client library and C,fortran and C++ application interface libraries allow the user to connect and define his own histogram or read histograms owned by others using an bool-like interface.Several calibration processes running in parallel in a destributed,multiplatform environment can fill the same histograms,allowing fast external information check.A monitor thread allow remote browsing for visual inspection,Pre-filtered data are read in nonprivileged spy mode from the data acquisition system via the Kloe Integrated Dataflow,privileged spy mode from the data acquisiton system via the Kole Integrated Dataflow.The main characteristics of the system are presented.

  3. LED体三维显示BCC采样体素化%BCC Sampling Voxelization in LED 3D Display

    Institute of Scientific and Technical Information of China (English)

    林品武; 孔凡国; 魏盼盼

    2014-01-01

    In order to reduce the number of voxels and improve the accuracy in the LED 3D display ,BCC sampling methods is used . The"cow"model is taken as an example ,compared with the Cartesian sampling ,BCC sampling with the same number of samples reduces the voxels by 27 .6% .When the number of samples by BCC reduce to 70% of the Cartesian samples ,the voxels can be reduced by 43 .4% .%在L ED立方体三维显示中,为了减少体素量和提高精度,采用BCC栅格采样方法。以“牛”模型进行实验,对比笛卡尔采样, BCC采样在采样点数量相等的前提下体素量减少27.6%;将BCC栅格的采样点数量降低到笛卡尔栅格采样点数量的70%后, BCC采样得到的体素模型实际体素量要比笛卡尔采样得到的体素量减少43.4%。

  4. Selected organ dose conversion coefficients for external photons calculated using ICRP adult voxel phantoms and Monte Carlo code FLUKA.

    Science.gov (United States)

    Patni, H K; Nadar, M Y; Akar, D K; Bhati, S; Sarkar, P K

    2011-11-01

    The adult reference male and female computational voxel phantoms recommended by ICRP are adapted into the Monte Carlo transport code FLUKA. The FLUKA code is then utilised for computation of dose conversion coefficients (DCCs) expressed in absorbed dose per air kerma free-in-air for colon, lungs, stomach wall, breast, gonads, urinary bladder, oesophagus, liver and thyroid due to a broad parallel beam of mono-energetic photons impinging in anterior-posterior and posterior-anterior directions in the energy range of 15 keV-10 MeV. The computed DCCs of colon, lungs, stomach wall and breast are found to be in good agreement with the results published in ICRP publication 110. The present work thus validates the use of FLUKA code in computation of organ DCCs for photons using ICRP adult voxel phantoms. Further, the DCCs for gonads, urinary bladder, oesophagus, liver and thyroid are evaluated and compared with results published in ICRP 74 in the above-mentioned energy range and geometries. Significant differences in DCCs are observed for breast, testis and thyroid above 1 MeV, and for most of the organs at energies below 60 keV in comparison with the results published in ICRP 74. The DCCs of female voxel phantom were found to be higher in comparison with male phantom for almost all organs in both the geometries.

  5. A multicenter reproducibility study of single-voxel {sup 1}H-MRS of the medial temporal lobe

    Energy Technology Data Exchange (ETDEWEB)

    Traeber, Frank; Block, Wolfgang; Guer, Okan; Schild, Hans H. [University of Bonn, Department of Radiology, Bonn (Germany); Freymann, Nikolaus; Heun, Reinhard; Jessen, Frank [University of Bonn, Department of Psychiatry, Bonn (Germany); Kucinski, Thomas [University of Hamburg, Department of Neuroradiology, Hamburg (Germany); Hammen, Thilo [University of Erlangen, Department of Psychiatry, Erlangen (Germany); Ende, Gabriele [Central Institute of Mental Health, NMR Research in Psychiatry, Mannheim (Germany); Pilatus, Ulrich [University of Frankfurt, Department of Neuroradiology, Frankfurt (Germany); Hampel, Harald [University of Munich, Department of Psychiatry, Munich (Germany)

    2006-05-15

    Proton magnetic resonance spectroscopy ({sup 1}H-MRS) has provided evidence for a reduction of N-acetyl-aspartate (NAA) in the medial temporal lobe (MTL) in cerebral disorders such as Alzheimer's Disease. Within the {sup 1}H-MRS study of the German Research Network on Dementia, we determined the multicenter reproducibility of single-voxel {sup 1}H-MRS of the MTL. At five sites with 1.5T MR systems, single-voxel {sup 1}H spectra from the MTL of an identical healthy subject were measured. The same subject was also examined at one of the sites five times to assess intracenter stability. The protocol included water-suppressed spectra with TE 272 ms and TE 30 ms and unsuppressed spectra for absolute quantification of metabolite concentrations. The intracenter reproducibility of absolute NAA concentration, expressed as coefficient of variation (CV), was 1.8%. CV for the concentrations of creatine (Cr), choline (Cho), and myoinositol (MI) and for the ratios NAA/Cr, NAA/Cho, and MI/NAA varied by 11-16%. Intercenter CV was 3.9% for NAA and were below 10% for all other metabolites and metabolic ratios. Our study demonstrates that quantitative assessment of NAA with single-voxel MRS can be performed with high intercenter reproducibility. This is the basis for applying {sup 1}H-MRS in large-scale early recognition and treatment studies in MTL affecting disorders. (orig.)

  6. Reliability-Based Code Calibration

    DEFF Research Database (Denmark)

    Faber, M.H.; Sørensen, John Dalsgaard

    2003-01-01

    The present paper addresses fundamental concepts of reliability based code calibration. First basic principles of structural reliability theory are introduced and it is shown how the results of FORM based reliability analysis may be related to partial safety factors and characteristic values....... Thereafter the code calibration problem is presented in its principal decision theoretical form and it is discussed how acceptable levels of failure probability (or target reliabilities) may be established. Furthermore suggested values for acceptable annual failure probabilities are given for ultimate...... and serviceability limit states. Finally the paper describes the Joint Committee on Structural Safety (JCSS) recommended procedure - CodeCal - for the practical implementation of reliability based code calibration of LRFD based design codes....

  7. Reduced Ambiguity Calibration for LOFAR

    CERN Document Server

    Yatawatta, Sarod

    2012-01-01

    Interferometric calibration always yields non unique solutions. It is therefore essential to remove these ambiguities before the solutions could be used in any further modeling of the sky, the instrument or propagation effects such as the ionosphere. We present a method for LOFAR calibration which does not yield a unitary ambiguity, especially under ionospheric distortions. We also present exact ambiguities we get in our solutions, in closed form. Casting this as an optimization problem, we also present conditions for this approach to work. The proposed method enables us to use the solutions obtained via calibration for further modeling of instrumental and propagation effects. We provide extensive simulation results on the performance of our method. Moreover, we also give cases where due to degeneracy, this method fails to perform as expected and in such cases, we suggest exploiting diversity in time, space and frequency.

  8. Astrid-2 EMMA Magnetic Calibration

    DEFF Research Database (Denmark)

    Merayo, José M.G.; Brauer, Peter; Risbo, Torben

    1998-01-01

    The Swedish micro-satellite Astrid-2 contains a tri-axial fluxgate magnetometer with the sensor co-located with a Technical University of Denmark (DTU) star camera for absolute attitude, and extended about 0.9 m on a hinged boom. The magnetometer is part of the RIT EMMA electric and magnetic fields...... Survey of Sweden near Stockholm on the night of May 15.-16., 1997. The magnetic calibration and the intercalibration between the star camera and the magnetic sensor was performed by measuring the Earth's magnetic field and simultaneously observing the star sky with the camera. The rotation matrix between...... fit calibration parameters. Owing to time shortage, we did not evaluate the temperature coefficients of the flight sensor calibration parameters. However, this was done for an identical flight spare magnetometer sensor at the magnetic coil facility belonging to the Technical University of Braunschweig...

  9. On chromatic and geometrical calibration

    DEFF Research Database (Denmark)

    Folm-Hansen, Jørgen

    1999-01-01

    of non-uniformity of the illumination of the image plane. Only the image deforming aberrations and the non-uniformity of illumination are included in the calibration models. The topics of the pinhole camera model and the extension to the Direct Linear Transform (DLT) are described. It is shown how......The main subject of the present thesis is different methods for the geometrical and chromatic calibration of cameras in various environments. For the monochromatic issues of the calibration we present the acquisition of monochrome images, the classic monochrome aberrations and the various sources...... the DLT can be extended with non-linear models of the common lens aberrations/errors some of them caused by manufacturing defects like decentering and thin prism distortion. The relation between a warping and the non-linear defects are shown. The issue of making a good resampling of an image by using...

  10. Flexible calibration procedure for fringe projection profilometry

    OpenAIRE

    Vargas, Javier; Quiroga Mellado, Juan Antonio; Terrón López, María José

    2007-01-01

    A novel calibration method for whole field three-dimensional shape measurement by means of fringe projection is presented. Standard calibration techniques, polynomial-and model-based, have practical limitations such as the difficulty of measuring large fields of view, the need to use precise z stages, and bad calibration results due to inaccurate calibration points. The proposed calibration procedure is a mixture of the two main standard techniques, sharing their benefits and avoiding their m...

  11. Tank calibration; Arqueacao de tanques

    Energy Technology Data Exchange (ETDEWEB)

    Chan, Ana [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)

    2003-07-01

    This work relates the analysis of the norms ISO (International Organization for Standardization) for calibration of vertical cylindrical tanks used in fiscal measurement, established on Joint Regulation no 1 of June 19, 2000 between the ANP (National Agency of Petroleum) and the INMETRO (National Institute of Metrology, Normalization and Industrial Quality). In this work a comparison between norms ISO and norms published by the API (American Petroleum Institute) and the IP (Institute of Petroleum) up to 2001 was made. It was concluded that norms ISO are wider than norms API, IP, and INMETRO methods in the calibration of vertical cylindrical tanks. (author)

  12. Instrument Calibration and Certification Procedure

    Energy Technology Data Exchange (ETDEWEB)

    Davis, R. Wesley [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-05-31

    The Amptec 640SL-2 is a 4-wire Kelvin failsafe resistance meter, designed to reliably use very low-test currents for its resistance measurements. The 640SL-1 is a 2-wire version, designed to support customers using the Reynolds Industries type 311 connector. For both versions, a passive (analog) dual function DC Milliameter/Voltmeter allows the user to verify the actual 640SL output current level and the open circuit voltage on the test leads. This procedure includes tests of essential performance parameters. Any malfunction noticed during calibration, whether specifically tested for or not, shall be corrected before calibration continues or is completed.

  13. Performance standard for dose Calibrator

    CERN Document Server

    Darmawati, S

    2002-01-01

    Dose calibrator is an instrument used in hospitals to determine the activity of radionuclide for nuclear medicine purposes. International Electrotechnical Commission (IEC) has published IEC 1303:1994 standard that can be used as guidance to test the performance of the instrument. This paper briefly describes content of the document,as well as explains the assessment that had been carried out to test the instrument accuracy in Indonesia through intercomparison measurement.Its is suggested that hospitals acquire a medical physicist to perform the test for its dose calibrator. The need for performance standard in the form of Indonesia Standard is also touched.

  14. 3-D geometry calibration and markerless electromagnetic tracking with a mobile C-arm

    Science.gov (United States)

    Cheryauka, Arvi; Barrett, Johnny; Wang, Zhonghua; Litvin, Andrew; Hamadeh, Ali; Beaudet, Daniel

    2007-03-01

    The design of mobile X-ray C-arm equipment with image tomography and surgical guidance capabilities involves the retrieval of repeatable gantry positioning in three-dimensional space. Geometry misrepresentations can cause degradation of the reconstruction results with the appearance of blurred edges, image artifacts, and even false structures. It may also amplify surgical instrument tracking errors leading to improper implant placement. In our prior publications we have proposed a C-arm 3D positioner calibration method comprising separate intrinsic and extrinsic geometry calibration steps. Following this approach, in the present paper, we extend the intrinsic geometry calibration of C-gantry beyond angular positions in the orbital plane into angular positions on a unit sphere of isocentric rotation. Our method makes deployment of markerless interventional tool guidance with use of high-resolution fluoro images and electromagnetic tracking feasible at any angular position of the tube-detector assembly. Variations of the intrinsic parameters associated with C-arm motion are measured off-line as functions of orbital and lateral angles. The proposed calibration procedure provides better accuracy, and prevents unnecessary workflow steps for surgical navigation applications. With a slight modification, the Misalignment phantom, a tool for intrinsic geometry calibration, is also utilized to obtain an accurate 'image-to-sensor' mapping. We show simulation results, image quality and navigation accuracy estimates, and feasibility data acquired with the prototype system. The experimental results show the potential of high-resolution CT imaging (voxel size below 0.5 mm) and confident navigation in an interventional surgery setting with a mobile C-arm.

  15. Voxel-based clustered imaging by multiparameter diffusion tensor images for glioma grading

    Directory of Open Access Journals (Sweden)

    Rika Inano

    2014-01-01

    Full Text Available Gliomas are the most common intra-axial primary brain tumour; therefore, predicting glioma grade would influence therapeutic strategies. Although several methods based on single or multiple parameters from diagnostic images exist, a definitive method for pre-operatively determining glioma grade remains unknown. We aimed to develop an unsupervised method using multiple parameters from pre-operative diffusion tensor images for obtaining a clustered image that could enable visual grading of gliomas. Fourteen patients with low-grade gliomas and 19 with high-grade gliomas underwent diffusion tensor imaging and three-dimensional T1-weighted magnetic resonance imaging before tumour resection. Seven features including diffusion-weighted imaging, fractional anisotropy, first eigenvalue, second eigenvalue, third eigenvalue, mean diffusivity and raw T2 signal with no diffusion weighting, were extracted as multiple parameters from diffusion tensor imaging. We developed a two-level clustering approach for a self-organizing map followed by the K-means algorithm to enable unsupervised clustering of a large number of input vectors with the seven features for the whole brain. The vectors were grouped by the self-organizing map as protoclusters, which were classified into the smaller number of clusters by K-means to make a voxel-based diffusion tensor-based clustered image. Furthermore, we also determined if the diffusion tensor-based clustered image was really helpful for predicting pre-operative glioma grade in a supervised manner. The ratio of each class in the diffusion tensor-based clustered images was calculated from the regions of interest manually traced on the diffusion tensor imaging space, and the common logarithmic ratio scales were calculated. We then applied support vector machine as a classifier for distinguishing between low- and high-grade gliomas. Consequently, the sensitivity, specificity, accuracy and area under the curve of receiver operating

  16. Effects of voxel size and iterative reconstruction parameters on the spatial resolution of 99mTc SPECT/CT.

    Science.gov (United States)

    Kappadath, S Cheenu

    2011-11-15

    The purpose of this study was to evaluate the effects of voxel size and iterative reconstruction parameters on the radial and tangential resolution for 99mTc SPECT as a function of radial distance from isocenter. SPECT/CT scans of eight coplanar point sources of size smaller than 1 mm3 containing high concentration 99mTc solution were acquired on a SPECT/CT system with 5/8 inch NaI(Tl) detector and low-energy, high-resolution collimator. The tomographic projection images were acquired in step-and-shoot mode for 360 views over 360° with 250,000 counts per view, a zoom of 2.67, and an image matrix of 256 × 256 pixels that resulted in a 0.9 × 0.9 × 0.9 mm3 SPECT voxel size over 230 mm field-of-view. The projection images were also rebinned to image matrices of 128 × 128 and 64 × 64 to yield SPECT voxel sizes of 1.8 × 1.8 × 1.8 and 3.6 × 3.6 × 3.6 mm3, respectively. The SPECT/CT datasets were reconstructed using the vendor-supplied iterative reconstruction software that incorporated collimator-specific resolution recovery, CT-based attenuation correction, and dual-energy window-based scatter correction using different combinations of iterations and subsets. SPECT spatial resolution was estimated as the full width at half maximum of the radial and tangential profiles through the center of each point source in reconstructed SPECT images. Both radial and tangential resolution improved with higher iterations and subsets, and with smaller voxel sizes. Both radial and tangential resolution also improved with radial distance further away from isocenter. The magnitude of variation decreased for smaller voxel sizes and for higher number of iterations and subsets. Tangential resolution was found not to be equal to the radial resolution, and the nature of the anisotropy depended on the distribution of the radionuclide and on the reconstruction parameters used. The tangential resolution converged faster than the radial resolution, with higher iterations and subsets

  17. Voxel-wise relationships between distribution volume ratio and cerebral blood flow: implications for analysis of β-amyloid images

    Science.gov (United States)

    Sojkova, Jitka; Goh, Joshua; Bilgel, Murat; Landman, Bennett; Yang, Xue; Zhou, Yun; An, Yang; Beason-Held, Lori L.; Kraut, Michael A.; Wong, Dean F.; Resnick, Susan M.

    2017-01-01

    Quantification of β-amyloid (Aβ) in vivo is often accomplished using the distribution volume ratio (DVR), based on a simplified reference tissue model. We investigated the local relationships between DVR and cerebral blood flow (CBF), as well as relative blood flow (R1), in nondemented older adults. Methods Fifty-five nondemented participants (mean age 78.5 years) in the Baltimore Longitudinal Study of Aging underwent 15O-H2O PET CBF and dynamic 11C-PiB-PET. 15O-H2O PET images were normalized and smoothed using SPM. A simplified reference tissue model with linear regression and spatial constraints was used to generate parametric DVR images. The DVR images were regressed on CBF images on a voxel-by-voxel basis using robust Biological Parametric Mapping, adjusting for age and sex (FDR p=0.05, k=50). DVR images were also regressed on R1 images, a measure of the transport rate constant from vascular space to tissue. All analyses were performed in the entire sample, and in high and low tertiles of mean cortical DVR. Results Voxel-based analyses showed that increased DVR is associated with increased CBF in frontal, parietal, temporal, and occipital cortices. However, this association appears to spare regions that typically show early β-amyloid (Aβ) deposition. A more robust relationship between DVR and CBF was observed in the lowest tertile of DVR, i.e., negligible cortical Aβ load, compared to the highest tertile of cortical DVR and Aβ load. Spatial distributions of the DVR-CBF and DVR-R1 correlations showed similar patterns. No reliable negative voxel-wise relationships between DVR and CBF or R1 were observed. Conclusion Robust associations between DVR and CBF at negligible Aβ levels, together with similar spatial distributions of DVR-CBF and DVR-R1 correlations, suggest that regional distribution of DVR reflects blood flow and tracer influx rather than pattern of Aβ deposition in those with minimal Aβ load. DVR-CBF associations in individuals with higher DVR

  18. The SENSE-Isomorphism Theoretical Image Voxel Estimation (SENSE-ITIVE) model for reconstruction and observing statistical properties of reconstruction operators.

    Science.gov (United States)

    Bruce, Iain P; Karaman, M Muge; Rowe, Daniel B

    2012-10-01

    The acquisition of sub-sampled data from an array of receiver coils has become a common means of reducing data acquisition time in MRI. Of the various techniques used in parallel MRI, SENSitivity Encoding (SENSE) is one of the most common, making use of a complex-valued weighted least squares estimation to unfold the aliased images. It was recently shown in Bruce et al. [Magn. Reson. Imag. 29(2011):1267-1287] that when the SENSE model is represented in terms of a real-valued isomorphism,it assumes a skew-symmetric covariance between receiver coils, as well as an identity covariance structure between voxels. In this manuscript, we show that not only is the skew-symmetric coil covariance unlike that of real data, but the estimated covariance structure between voxels over a time series of experimental data is not an identity matrix. As such, a new model, entitled SENSE-ITIVE, is described with both revised coil and voxel covariance structures. Both the SENSE and SENSE-ITIVE models are represented in terms of real-valued isomorphisms, allowing for a statistical analysis of reconstructed voxel means, variances, and correlations resulting from the use of different coil and voxel covariance structures used in the reconstruction processes to be conducted. It is shown through both theoretical and experimental illustrations that the miss-specification of the coil and voxel covariance structures in the SENSE model results in a lower standard deviation in each voxel of the reconstructed images, and thus an artificial increase in SNR, compared to the standard deviation and SNR of the SENSE-ITIVE model where both the coil and voxel covariances are appropriately accounted for. It is also shown that there are differences in the correlations induced by the reconstruction operations of both models, and consequently there are differences in the correlations estimated throughout the course of reconstructed time series. These differences in correlations could result in meaningful

  19. Development of a voxel-matching technique for substantial reduction of subtraction artifacts in temporal subtraction images obtained from thoracic MDCT.

    Science.gov (United States)

    Itai, Yoshinori; Kim, Hyoungseop; Ishikawa, Seiji; Katsuragawa, Shigehiko; Doi, Kunio

    2010-02-01

    A temporal subtraction image, which is obtained by subtraction of a previous image from a current one, can be used for enhancing interval changes (such as formation of new lesions and changes in existing abnormalities) on medical images by removing most of the normal structures. However, subtraction artifacts are commonly included in temporal subtraction images obtained from thoracic computed tomography and thus tend to reduce its effectiveness in the detection of pulmonary nodules. In this study, we developed a new method for substantially removing the artifacts on temporal subtraction images of lungs obtained from multiple-detector computed tomography (MDCT) by using a voxel-matching technique. Our new method was examined on 20 clinical cases with MDCT images. With this technique, the voxel value in a warped (or nonwarped) previous image is replaced by a voxel value within a kernel, such as a small cube centered at a given location, which would be closest (identical or nearly equal) to the voxel value in the corresponding location in the current image. With the voxel-matching technique, the correspondence not only between the structures but also between the voxel values in the current and the previous images is determined. To evaluate the usefulness of the voxel-matching technique for removal of subtraction artifacts, the magnitude of artifacts remaining in the temporal subtraction images was examined by use of the full width at half maximum and the sum of a histogram of voxel values, which may indicate the average contrast and the total amount, respectively, of subtraction artifacts. With our new method, subtraction artifacts due to normal structures such as blood vessels were substantially removed on temporal subtraction images. This computerized method can enhance lung nodules on chest MDCT images without disturbing misregistration artifacts.

  20. Regional grey matter structure differences between transsexuals and healthy controls--a voxel based morphometry study.

    Directory of Open Access Journals (Sweden)

    Lajos Simon

    Full Text Available Gender identity disorder (GID refers to transsexual individuals who feel that their assigned biological gender is incongruent with their gender identity and this cannot be explained by any physical intersex condition. There is growing scientific interest in the last decades in studying the neuroanatomy and brain functions of transsexual individuals to better understand both the neuroanatomical features of transsexualism and the background of gender identity. So far, results are inconclusive but in general, transsexualism has been associated with a distinct neuroanatomical pattern. Studies mainly focused on male to female (MTF transsexuals and there is scarcity of data acquired on female to male (FTM transsexuals. Thus, our aim was to analyze structural MRI data with voxel based morphometry (VBM obtained from both FTM and MTF transsexuals (n = 17 and compare them to the data of 18 age matched healthy control subjects (both males and females. We found differences in the regional grey matter (GM structure of transsexual compared with control subjects, independent from their biological gender, in the cerebellum, the left angular gyrus and in the left inferior parietal lobule. Additionally, our findings showed that in several brain areas, regarding their GM volume, transsexual subjects did not differ significantly from controls sharing their gender identity but were different from those sharing their biological gender (areas in the left and right precentral gyri, the left postcentral gyrus, the left posterior cingulate, precuneus and calcarinus, the right cuneus, the right fusiform, lingual, middle and inferior occipital, and inferior temporal gyri. These results support the notion that structural brain differences exist between transsexual and healthy control subjects and that majority of these structural differences are dependent on the biological gender.

  1. Single voxel 1 H magnetic resonance spectroscopy in the diagnosis of musculoskeletal mass lesions

    Directory of Open Access Journals (Sweden)

    Shalini Agarwal

    2014-01-01

    Full Text Available Introduction: In vivo magnetic resonance spectroscopy (MRS is an established technique for evaluation of malignant tumors in brain, breast, prostate, etc., However, its efficacy in the diagnosis of musculoskeletal (MSK mass lesions is yet to be established. We present our experience with MRS of these lesions. Materials and Methods: Magnetic resonance imaging (MRI, dynamic contrast-enhanced MRI and single-voxel 1 H MRS was performed in 30 consecutive patients with histologically proven benign and malignant MSK tumors/mass lesions each, on a 1.5-T magnetic resonance scanner. MRS was performed with echo times (TE of 40, 135 and 270 ms. A clearly identifiable peak at 3.2 ppm in at least two of the three spectra acquired at the three TE was taken as positive for choline. MRS imaging and enhancement patterns were compared in these two groups and were analyzed by a Radiologist blinded to the histopathological findings. Results: Ages of patients in the malignant age group ranged from 2 to 65 years (M: F - 19:11 while that of patients in the benign group ranged from 7 months to 56 years (M: F - 17:13. There were two patients with Type I curve, 18 with Type II curve and 10 with Type III curve on dynamic contrast enhanced images in the malignant group while there were no patients with Type I curve, 5 with Type II curve and 25 with Type III curve in the benign group. The sensitivity of MRS for predicting malignancy was 60%, specificity was 93.33%, positive predictive value was 90%, negative predictive value was 70% and accuracy was 76.66%. Conclusion: MRS is a promising technique for evaluation of MSK mass lesions. The accuracy at present remains low. We recommend that it be used as an adjunct to routine MRI.

  2. Sports and brain morphology - a voxel-based morphometry study with endurance athletes and martial artists.

    Science.gov (United States)

    Schlaffke, L; Lissek, S; Lenz, M; Brüne, M; Juckel, G; Hinrichs, T; Platen, P; Tegenthoff, M; Schmidt-Wilcke, T

    2014-02-14

    Physical exercises and motor skill learning have been shown to induce changes in regional brain morphology, this has been demonstrated for various activities and tasks. Also individuals with special skills show differences in regional brain morphology. This has been indicated for professional musicians, London taxi drivers, as well as for athletes like dancers, golfers and judokas. However little is known about whether sports with different metabolic profiles (aerobic vs. anaerobic) are associated with different patterns of altered brain morphology. In this cross-sectional study we investigated two groups of high-performance athletes, one group performing sports that are thought to be mainly aerobic, and one group performing sports known to have intermittent phases of anaerobic metabolism. Using high-resolution structural imaging and voxel-based morphometry (VBM), we investigated a group of 26 male athletes consisting of 13 martial artists and 13 endurance athletes as well as a group of non-exercising men (n=13). VBM analyses revealed higher gray matter (GM) volumes in the supplementary motor area/dorsal premotor cortex (BA 6) in both athlete groups as compared to the control group. In addition, endurance athletes showed significantly higher GM volume in the medial temporal lobe (MTL), specifically in the hippocampus and parahippocampal gyrus, which was not seen in the martial arts group. Our data suggest that high-performance sports are associated with changes in regional brain morphology in areas implicated in motor planning and motor learning. In addition high-level endurance sports seem to affect MTL structures, areas that have previously been shown to be modulated by aerobic exercise.

  3. A Voxel-Based Morphometric MRI Study in Young Adults with Borderline Personality Disorder.

    Directory of Open Access Journals (Sweden)

    Xinhu Jin

    Full Text Available Increasing evidence has documented subtle changes in brain morphology and function in patients with borderline personality disorder (BPD. However, results of magnetic resonance imaging volumetry in patients with BPD are inconsistent. In addition, few researchers using voxel-based morphometry (VBM have focused on attachment and childhood trauma in BPD. This preliminary study was performed to investigate structural brain changes and their relationships to attachment and childhood trauma in a homogenous sample of young adults with BPD.We examined 34 young adults with BPD and 34 healthy controls (HCs to assess regionally specific differences in gray matter volume (GMV and gray matter concentration (GMC. Multiple regressions between brain volumes measured by VBM and attachment style questionnaire (ASQ and childhood trauma questionnaire (CTQ scores were performed.Compared with HCs, subjects with BPD showed significant bilateral increases in GMV in the middle cingulate cortex (MCC/posterior cingulate cortex (PCC/precuneus. GMC did not differ significantly between groups. In multiple regression models, ASQ insecure attachment scores were correlated negatively with GMV in the precuneus/MCC and middle occipital gyrus in HCs, HCs with more severe insecure attachment showed smaller volumes in precuneus/MCC and middle occipital gyrus, whereas no negative correlations between insecure attachment and GMV in any region were found in BPD group. In addition, CTQ total scores were not correlated with GMV in any region in the two groups respectively.Our findings fit with those of previous reports of larger precuneus GMV in patients with BPD, and suggest that GMV in the precuneus/MCC and middle occipital gyrus is associated inversely with insecure attachment style in HCs. Our finding of increased GMV in the MCC and PCC in patients with BPD compared with HCs has not been reported in previous VBM studies.

  4. Neuroanatomical circuitry associated with exploratory eye movement in schizophrenia: a voxel-based morphometric study.

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    Linlin Qiu

    Full Text Available Schizophrenic patients present abnormalities in a variety of eye movement tasks. Exploratory eye movement (EEM dysfunction appears to be particularly specific to schizophrenia. However, the underlying mechanisms of EEM dysfunction in schizophrenia are not clearly understood. To assess the potential neuroanatomical substrates of EEM, we recorded EEM performance and conducted a voxel-based morphometric analysis of gray matter in 33 schizophrenic patients and 29 well matched healthy controls. In schizophrenic patients, decreased responsive search score (RSS and widespread gray matter density (GMD reductions were observed. Moreover, the RSS was positively correlated with GMD in distributed brain regions in schizophrenic patients. Furthermore, in schizophrenic patients, some brain regions with neuroanatomical deficits overlapped with some ones associated with RSS. These brain regions constituted an occipito-tempro-frontal circuitry involved in visual information processing and eye movement control, including the left calcarine cortex [Brodmann area (BA 17], the left cuneus (BA 18, the left superior occipital cortex (BA 18/19, the left superior frontal gyrus (BA 6, the left cerebellum, the right lingual cortex (BA 17/18, the right middle occipital cortex (BA19, the right inferior temporal cortex (BA 37, the right dorsolateral prefrontal cortex (BA 46 and bilateral precentral gyri (BA 6 extending to the frontal eye fields (FEF, BA 8. To our knowledge, we firstly reported empirical evidence that gray matter loss in the occipito-tempro-frontal neuroanatomical circuitry of visual processing system was associated with EEM performance in schizophrenia, which may be helpful for the future effort to reveal the underlying neural mechanisms for EEM disturbances in schizophrenia.

  5. Brain volumetric abnormalities in patients with anorexia and bulimia nervosa: a voxel-based morphometry study.

    Science.gov (United States)

    Amianto, Federico; Caroppo, Paola; D'Agata, Federico; Spalatro, Angela; Lavagnino, Luca; Caglio, Marcella; Righi, Dorico; Bergui, Mauro; Abbate-Daga, Giovanni; Rigardetto, Roberto; Mortara, Paolo; Fassino, Secondo

    2013-09-30

    Recent studies focussing on neuroimaging features of eating disorders have observed that anorexia nervosa (AN) is characterized by significant grey matter (GM) atrophy in many brain regions, especially in the cerebellum and anterior cingulate cortex. To date, no studies have found GM atrophy in bulimia nervosa (BN) or have directly compared patients with AN and BN. We used voxel-based morphometry (VBM) to characterize brain abnormalities in AN and BN patients, comparing them with each other and with a control group, and correlating brain volume with clinical features. We recruited 17 AN, 13 BN and 14 healthy controls. All subjects underwent high-resolution magnetic resonance imaging (MRI) with a T1-weighted 3D image. VBM analysis was carried out with the FSL-VBM 4.1 tool. We found no global atrophy, but regional GM reduction in AN with respect to controls and BN in the cerebellum, fusiform area, supplementary motor area, and occipital cortex, and in the caudate in BN compared to AN and controls. Both groups of patients had a volumetric increase bilaterally in somatosensory regions with respect to controls, in areas that are typically involved in the sensory-motor integration of body stimuli and in mental representation of the body image. Our VBM study documented, for the first time in BN patients, the presence of volumetric alterations and replicated previous findings in AN patients. We evidenced morphological differences between AN and BN, demonstrating in the latter atrophy of the caudate nucleus, a region involved in reward mechanisms and processes of self-regulation, perhaps involved in the genesis of the binge-eating behaviors of this disorder.

  6. Voxel-based dose prediction with multi-patient atlas selection for automated radiotherapy treatment planning

    Science.gov (United States)

    McIntosh, Chris; Purdie, Thomas G.

    2017-01-01

    Automating the radiotherapy treatment planning process is a technically challenging problem. The majority of automated approaches have focused on customizing and inferring dose volume objectives to be used in plan optimization. In this work we outline a multi-patient atlas-based dose prediction approach that learns to predict the dose-per-voxel for a novel patient directly from the computed tomography planning scan without the requirement of specifying any objectives. Our method learns to automatically select the most effective atlases for a novel patient, and then map the dose from those atlases onto the novel patient. We extend our previous work to include a conditional random field for the optimization of a joint distribution prior that matches the complementary goals of an accurately spatially distributed dose distribution while still adhering to the desired dose volume histograms. The resulting distribution can then be used for inverse-planning with a new spatial dose objective, or to create typical dose volume objectives for the canonical optimization pipeline. We investigated six treatment sites (633 patients for training and 113 patients for testing) and evaluated the mean absolute difference in all DVHs for the clinical and predicted dose distribution. The results on average are favorable in comparison to our previous approach (1.91 versus 2.57). Comparing our method with and without atlas-selection further validates that atlas-selection improved dose prediction on average in whole breast (0.64 versus 1.59), prostate (2.13 versus 4.07), and rectum (1.46 versus 3.29) while it is less important in breast cavity (0.79 versus 0.92) and lung (1.33 versus 1.27) for which there is high conformity and minimal dose shaping. In CNS brain, atlas-selection has the potential to be impactful (3.65 versus 5.09), but selecting the ideal atlas is the most challenging.

  7. Voxel-Based Spatial Filtering Method for Canopy Height Retrieval from Airborne Single-Photon Lidar

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    Hao Tang

    2016-09-01

    Full Text Available Airborne single-photon lidar (SPL is a new technology that holds considerable potential for forest structure and carbon monitoring at large spatial scales because it acquires 3D measurements of vegetation faster and more efficiently than conventional lidar instruments. However, SPL instruments use green wavelength (532 nm lasers, which are sensitive to background solar noise, and therefore SPL point clouds require more elaborate noise filtering than other lidar instruments to determine canopy heights, particularly in daytime acquisitions. Histogram-based aggregation is a commonly used approach for removing noise from photon counting lidar data, but it reduces the resolution of the dataset. Here we present an alternate voxel-based spatial filtering method that filters noise points efficiently while largely preserving the spatial integrity of SPL data. We develop and test our algorithms on an experimental SPL dataset acquired over Garrett County in Maryland, USA. We then compare canopy attributes retrieved using our new algorithm with those obtained from the conventional histogram binning approach. Our results show that canopy heights derived using the new algorithm have a strong agreement with field-measured heights (r2 = 0.69, bias = 0.42 m, RMSE = 4.85 m and discrete return lidar heights (r2 = 0.94, bias = 1.07 m, RMSE = 2.42 m. Results are consistently better than height accuracies from the histogram method (field data: r2 = 0.59, bias = 0.00 m, RMSE = 6.25 m; DRL: r2 = 0.78, bias = −0.06 m and RMSE = 4.88 m. Furthermore, we find that the spatial-filtering method retains fine-scale canopy structure detail and has lower errors over steep slopes. We therefore believe that automated spatial filtering algorithms such as the one presented here can support large-scale, canopy structure mapping from airborne SPL data.

  8. Age differences in the neural representation of working memory revealed by multi-voxel pattern analysis.

    Directory of Open Access Journals (Sweden)

    Joshua eCarp

    2010-11-01

    Full Text Available Working memory function declines across the lifespan. Computational models of aging attribute such memory impairments to reduced distinctiveness between neural representations of different mental states in old age, a phenomenon termed dedifferentiation. These models predict that neural distinctiveness should be reduced uniformly across experimental conditions in older adults. In contrast, the Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH model predicts that the distinctiveness of neural representations should be increased in older adults (relative to young adults at low levels of task demand but reduced at high levels of demand. The present study used multi-voxel pattern analysis (MVPA to measure the effects of age and task demands on the distinctiveness of the neural representations of verbal and visuospatial working memory. Neural distinctiveness was estimated separately for memory encoding, maintenance, and retrieval, and for low, medium, and high memory loads. Results from sensory cortex during encoding and retrieval were consistent with the dedifferentiation hypothesis: distinctiveness of visual cortical representations during these phases was uniformly reduced in older adults, irrespective of memory load. However, maintenance-related responses in prefrontal and parietal regions yielded a strikingly different pattern of results. At low loads, older adults showed higher distinctiveness than younger adults; at high loads, this pattern reversed, such that distinctiveness was higher in young adults. This interaction between age group and memory load is at odds with the dedifferentiation hypothesis but consistent with CRUNCH. In sum, our results provide partial support for both dedifferentiation- and compensation-based models; we argue that comprehensive theories of cognitive aging must incorporate aspects of both models to fully explain complex patterns of age-related neuro-cognitive change.

  9. Rapid registration of multimodal images using a reduced number of voxels

    Science.gov (United States)

    Huang, Xishi; Hill, Nicholas A.; Ren, Jing; Peters, Terry M.

    2006-03-01

    Rapid registration of multimodal cardiac images can improve image-guided cardiac surgeries and cardiac disease diagnosis. While mutual information (MI) is arguably the most suitable registration technique, this method is too slow to converge for real time cardiac image registration; moreover, correct registration may not coincide with a global or even local maximum of MI. These limitations become quite evident when registering three-dimensional (3D) ultrasound (US) images and dynamic 3D magnetic resonance (MR) images of the beating heart. To overcome these issues, we present a registration method that uses a reduced number of voxels, while retaining adequate registration accuracy. Prior to registration we preprocess the images such that only the most representative anatomical features are depicted. By selecting samples from preprocessed images, our method dramatically speeds up the registration process, as well as ensuring correct registration. We validated this registration method for registering dynamic US and MR images of the beating heart of a volunteer. Experimental results on in vivo cardiac images demonstrate significant improvements in registration speed without compromising registration accuracy. A second validation study was performed registering US and computed tomography (CT) images of a rib cage phantom. Two similarity metrics, MI and normalized crosscorrelation (NCC) were used to register the image sets. Experimental results on the rib cage phantom indicate that our method can achieve adequate registration accuracy within 10% of the computation time of conventional registration methods. We believe this method has the potential to facilitate intra-operative image fusion for minimally invasive cardio-thoracic surgical navigation.

  10. Voxel-based moprhometry in the differential diagnosis of posttraumatic cognitive impairments

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    M.M. Odinak

    2014-01-01

    Full Text Available Brain injury (BI is a major cause of cognitive impairments (CI in young people. However, many aspects of their development remain unstudied. In particular, the role of neurodegenerative and vascular processes in the occurrence of posttraumatic disorders of higher cortical functions is still unclear. Voxel-based morphometry is one of the current neuroimaging techniques. Objective: to comprehensively study a change in the volume indicators of a number of brain structures in patients with posttraumatic, vascular, and amnestic CI.Patients and methods. The investigation enrolled 123 patients who were divided into 5 groups: 1 20 examinees without CI (a control group; 2 22 patients with mild and moderate CI and a history of mild recurrent CI; 3 19 patients with moderate posttraumatic CI after severe brain contusion; 4 41 patients with moderate vascular CI; 5 21 patients with moderate amnestic CI. Before divided into the groups, all the patients underwent comprehensive neuropsychological testing, which enabled different aspects of cognitive performance to be assessed.Results. Atrophic changes were ascertained to be uncharacteristic for the patients who had sustained mild recurrent BI. At the same time, the patients with severe consequences of BI showed a significant decrease in the volume of brain regions, primarily in that of frontal and temporal lobes. A combined comprehensive assessment of the results obtained in the group analysis using SPM8 and calculating absolute volume values using MRICroN allowed one to more accurately understand the nature of neurodegenerative changes. Comparative assessment of the data obtained in the posttraumatic, vascular, and amnestic CI groups identified a number of differences in both the distribution of atrophic changes and their level, which can be of great importance for the differential diagnosis of these conditions.

  11. Brain structure in post-traumatic stress disorder A voxel-based morphometry analysis**

    Institute of Scientific and Technical Information of China (English)

    Liwen Tan; Li Zhang; Rongfeng Qi; Guangming Lu; Lingjiang Li; Jun Liu; Weihui Li

    2013-01-01

    This study compared the difference in brain structure in 12 mine disaster survivors with chronic post-traumatic stress disorder, 7 cases of improved post-traumatic stress disorder symptoms, and 14 controls who experienced the same mine disaster but did not suffer post-traumatic stress disorder, us-ing the voxel-based morphometry method. The correlation between differences in brain structure and post-traumatic stress disorder symptoms was also investigated. Results showed that the gray matter volume was the highest in the trauma control group, fol owed by the symptoms-improved group, and the lowest in the chronic post-traumatic stress disorder group. Compared with the symptoms-improved group, the gray matter volume in the lingual gyrus of the right occipital lobe was reduced in the chronic post-traumatic stress disorder group. Compared with the trauma control group, the gray matter volume in the right middle occipital gyrus and left middle frontal gyrus was reduced in the symptoms-improved group. Compared with the trauma control group, the gray matter volume in the left superior parietal lobule and right superior frontal gyrus was reduced in the chronic post-traumatic stress disorder group. The gray matter volume in the left superior parietal lobule was significantly positively correlated with the State-Trait Anxiety Inventory subscale score in the symptoms-improved group and chronic post-traumatic stress disorder group (r = 0.477, P = 0.039). Our findings indicate that (1) chronic post-traumatic stress disorder patients have gray matter structural damage in the prefrontal lobe, occip-ital lobe, and parietal lobe, (2) after post-traumatic stress, the disorder symptoms are improved and gray matter structural damage is reduced, but cannot recover to the trauma-control level, and (3) the superior parietal lobule is possibly associated with chronic post-traumatic stress disorder. Post-traumatic stress disorder patients exhibit gray matter abnormalities.

  12. Brain structure in post-traumatic stress disorder: A voxel-based morphometry analysis.

    Science.gov (United States)

    Tan, Liwen; Zhang, Li; Qi, Rongfeng; Lu, Guangming; Li, Lingjiang; Liu, Jun; Li, Weihui

    2013-09-15

    This study compared the difference in brain structure in 12 mine disaster survivors with chronic post-traumatic stress disorder, 7 cases of improved post-traumatic stress disorder symptoms, and 14 controls who experienced the same mine disaster but did not suffer post-traumatic stress disorder, using the voxel-based morphometry method. The correlation between differences in brain structure and post-traumatic stress disorder symptoms was also investigated. Results showed that the gray matter volume was the highest in the trauma control group, followed by the symptoms-improved group, and the lowest in the chronic post-traumatic stress disorder group. Compared with the symptoms-improved group, the gray matter volume in the lingual gyrus of the right occipital lobe was reduced in the chronic post-traumatic stress disorder group. Compared with the trauma control group, the gray matter volume in the right middle occipital gyrus and left middle frontal gyrus was reduced in the symptoms-improved group. Compared with the trauma control group, the gray matter volume in the left superior parietal lobule and right superior frontal gyrus was reduced in the chronic post-traumatic stress disorder group. The gray matter volume in the left superior parietal lobule was significantly positively correlated with the State-Trait Anxiety Inventory subscale score in the symptoms-improved group and chronic post-traumatic stress disorder group (r = 0.477, P = 0.039). Our findings indicate that (1) chronic post-traumatic stress disorder patients have gray matter structural damage in the prefrontal lobe, occipital lobe, and parietal lobe, (2) after post-traumatic stress, the disorder symptoms are improved and gray matter structural damage is reduced, but cannot recover to the trauma-control level, and (3) the superior parietal lobule is possibly associated with chronic post-traumatic stress disorder. Post-traumatic stress disorder patients exhibit gray matter abnormalities.

  13. Fast computation of voxel-level brain connectivity maps from resting-state functional MRI using l₁-norm as approximation of Pearson's temporal correlation: proof-of-concept and example vector hardware implementation.

    Science.gov (United States)

    Minati, Ludovico; Zacà, Domenico; D'Incerti, Ludovico; Jovicich, Jorge

    2014-09-01

    An outstanding issue in graph-based analysis of resting-state functional MRI is choice of network nodes. Individual consideration of entire brain voxels may represent a less biased approach than parcellating the cortex according to pre-determined atlases, but entails establishing connectedness for 1(9)-1(11) links, with often prohibitive computational cost. Using a representative Human Connectome Project dataset, we show that, following appropriate time-series normalization, it may be possible to accelerate connectivity determination replacing Pearson correlation with l1-norm. Even though the adjacency matrices derived from correlation coefficients and l1-norms are not identical, their similarity is high. Further, we describe and provide in full an example vector hardware implementation of l1-norm on an array of 4096 zero instruction-set processors. Calculation times <1000 s are attainable, removing the major deterrent to voxel-based resting-sate network mapping and revealing fine-grained node degree heterogeneity. L1-norm should be given consideration as a substitute for correlation in very high-density resting-state functional connectivity analyses.

  14. Scalar Calibration of Vector Magnetometers

    DEFF Research Database (Denmark)

    Merayo, José M.G.; Brauer, Peter; Primdahl, Fritz;

    2000-01-01

    The calibration parameters of a vector magnetometer are estimated only by the use of a scalar reference magnetometer. The method presented in this paper differs from those previously reported in its linearized parametrization. This allows the determination of three offsets or signals in the absence...

  15. Measurement System and Calibration report

    DEFF Research Database (Denmark)

    Gómez Arranz, Paula; Villanueva, Héctor

    This Measurement System & Calibration report is describing DTU’s measurement system installed at a specific wind turbine. A major part of the sensors has been installed by others (see [1]) the rest of the sensors have been installed by DTU. The results of the measurements, described in this repor...

  16. CALIBRATION OF THE INFRARED OPTOMETER

    Science.gov (United States)

    An infrared optometer for measuring the absolute status of accommodation is subject to a constant error not associated with chromatic aberration or...on optometer accuracy as long as the pupil does not vignette the optometer beam. A modification is described for calibrating the infrared optometer ...for an individual subject without using trial lenses or a subjective optometer . (Author)

  17. Measurement System and Calibration report

    DEFF Research Database (Denmark)

    Kock, Carsten Weber; Vesth, Allan

    This Measurement System & Calibration report is describing DTU’s measurement system installed at a specific wind turbine. A major part of the sensors has been installed by others (see [1]) the rest of the sensors have been installed by DTU. The results of the measurements, described in this report...

  18. Measurement System and Calibration report

    DEFF Research Database (Denmark)

    Vesth, Allan; Kock, Carsten Weber

    The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to Ref. [1]. A site calibration has been carried out; see Ref. [2], and the measured flow correction factors for different wind directions are used in the present...

  19. Multi-voxel pattern analysis (MVPA) reveals abnormal fMRI activity in both the “core” and “extended” face network in congenital prosopagnosia

    Science.gov (United States)

    Rivolta, Davide; Woolgar, Alexandra; Palermo, Romina; Butko, Marina; Schmalzl, Laura; Williams, Mark A.

    2014-01-01

    The ability to identify faces is mediated by a network of cortical and subcortical brain regions in humans. It is still a matter of debate which regions represent the functional substrate of congenital prosopagnosia (CP), a condition characterized by a lifelong impairment in face recognition, and affecting around 2.5% of the general population. Here, we used functional Magnetic Resonance Imaging (fMRI) to measure neural responses to faces, objects, bodies, and body-parts in a group of seven CPs and ten healthy control participants. Using multi-voxel pattern analysis (MVPA) of the fMRI data we demonstrate that neural activity within the “core” (i.e., occipital face area and fusiform face area) and “extended” (i.e., anterior temporal cortex) face regions in CPs showed reduced discriminability between faces and objects. Reduced differentiation between faces and objects in CP was also seen in the right parahippocampal cortex. In contrast, discriminability between faces and bodies/body-parts and objects and bodies/body-parts across the ventral visual system was typical in CPs. In addition to MVPA analysis, we also ran traditional mass-univariate analysis, which failed to show any group differences in face and object discriminability. In sum, these findings demonstrate (i) face-object representations impairments in CP which encompass both the “core” and “extended” face regions, and (ii) superior power of MVPA in detecting group differences. PMID:25431556

  20. Multi-voxel pattern analysis (MVPA reveals abnormal fMRI activity in both the core and extended face network in congenital prosopagnosia

    Directory of Open Access Journals (Sweden)

    Davide eRivolta

    2014-11-01

    Full Text Available The ability to identify faces is mediated by a network of cortical and subcortical brain regions in humans. It is still a matter of debate which regions represent the functional substrate of congenital prosopagnosia (CP, a condition characterized by a lifelong impairment in face recognition, and affecting around 2.5% of the general population. Here, we used functional Magnetic Resonance Imaging (fMRI to measure neural responses to faces, objects, bodies and body-parts in a group of seven CPs and ten healthy control participants. Using multi-voxel pattern analysis (MVPA of the fMRI data we demonstrate that neural activity within the core (i.e., occipital face area and fusiform face area and extended (i.e., anterior temporal cortex face regions in CPs showed reduced discriminability between faces and objects. Reduced differentiation between faces and objects in CP was also seen in the right parahippocampal cortex. In contrast, discriminability between faces and bodies/body-parts and objects and bodies/body-parts across the ventral visual system was typical in CPs. In addition to MVPA analysis, we also ran traditional mass-univariate analysis, which failed to show any group differences in face and object discriminability. In sum, these findings demonstrate (i face-object representations impairments in CP which encompass both the core and extended face regions, and (ii superior power of MVPA in detecting group differences.

  1. Multi-voxel pattern analysis (MVPA) reveals abnormal fMRI activity in both the "core" and "extended" face network in congenital prosopagnosia.

    Science.gov (United States)

    Rivolta, Davide; Woolgar, Alexandra; Palermo, Romina; Butko, Marina; Schmalzl, Laura; Williams, Mark A

    2014-01-01

    The ability to identify faces is mediated by a network of cortical and subcortical brain regions in humans. It is still a matter of debate which regions represent the functional substrate of congenital prosopagnosia (CP), a condition characterized by a lifelong impairment in face recognition, and affecting around 2.5% of the general population. Here, we used functional Magnetic Resonance Imaging (fMRI) to measure neural responses to faces, objects, bodies, and body-parts in a group of seven CPs and ten healthy control participants. Using multi-voxel pattern analysis (MVPA) of the fMRI data we demonstrate that neural activity within the "core" (i.e., occipital face area and fusiform face area) and "extended" (i.e., anterior temporal cortex) face regions in CPs showed reduced discriminability between faces and objects. Reduced differentiation between faces and objects in CP was also seen in the right parahippocampal cortex. In contrast, discriminability between faces and bodies/body-parts and objects and bodies/body-parts across the ventral visual system was typical in CPs. In addition to MVPA analysis, we also ran traditional mass-univariate analysis, which failed to show any group differences in face and object discriminability. In sum, these findings demonstrate (i) face-object representations impairments in CP which encompass both the "core" and "extended" face regions, and (ii) superior power of MVPA in detecting group differences.

  2. Radiation calibration for LWIR Hyperspectral Imager Spectrometer

    Science.gov (United States)

    Yang, Zhixiong; Yu, Chunchao; Zheng, Wei-jian; Lei, Zhenggang; Yan, Min; Yuan, Xiaochun; Zhang, Peizhong

    2014-11-01

    The radiometric calibration of LWIR Hyperspectral imager Spectrometer is presented. The lab has been developed to LWIR Interferometric Hyperspectral imager Spectrometer Prototype(CHIPED-I) to study Lab Radiation Calibration, Two-point linear calibration is carried out for the spectrometer by using blackbody respectively. Firstly, calibration measured relative intensity is converted to the absolute radiation lightness of the object. Then, radiation lightness of the object is is converted the brightness temperature spectrum by the method of brightness temperature. The result indicated †that this method of Radiation Calibration calibration was very good.

  3. Radio Interferometric Calibration Using a Riemannian Manifold

    CERN Document Server

    Yatawatta, Sarod

    2013-01-01

    In order to cope with the increased data volumes generated by modern radio interferometers such as LOFAR (Low Frequency Array) or SKA (Square Kilometre Array), fast and efficient calibration algorithms are essential. Traditional radio interferometric calibration is performed using nonlinear optimization techniques such as the Levenberg-Marquardt algorithm in Euclidean space. In this paper, we reformulate radio interferometric calibration as a nonlinear optimization problem on a Riemannian manifold. The reformulated calibration problem is solved using the Riemannian trust-region method. We show that calibration on a Riemannian manifold has faster convergence with reduced computational cost compared to conventional calibration in Euclidean space.

  4. [Full-field and automatic methodology of spectral calibration for PGP imaging spectrometer].

    Science.gov (United States)

    Sun, Ci; Bayanheshig; Cui, Ji-cheng; Pan, Ming-zhong; Li, Xiao-tian; Tang, Yu-guo

    2014-08-01

    In order to analyze spectral data quantitatively which is obtained by prism-grating-prism imaging spectrometer, spectral calibration is required in order to determine spectral characteristics of PGP imaging spectrometer, such as the center wavelength of every spectral channel, spectral resolution and spectral bending. A spectral calibration system of full field based on collimated monochromatic light method is designed. Spherical mirror is used to provide collimated light, and a freely sliding and rotating folding mirror is adopted to change the angle of incident light in order to realize full field and automatic calibration of imaging spectrometer. Experiments of spectral calibration have been done for PGP imaging spectrometer to obtain parameters of spectral performance, and accuracy analysis combined with the structural features of the entire spectral calibration system have been done. Analysis results indicate that spectral calibration accuracy of the calibration system reaches 0.1 nm, and the bandwidth accuracy reaches 1.3%. The calibration system has merits of small size, better commonality, high precision and so on, and because of adopting the control of automation, the additional errors which are caused by human are avoided. The calibration system can be used for spectral calibration of other imaging spectrometers whose structures are similar to PGP.

  5. A Fully GPU-Based Ray-Driven Backprojector via a Ray-Culling Scheme with Voxel-Level Parallelization for Cone-Beam CT Reconstruction.

    Science.gov (United States)

    Park, Hyeong-Gyu; Shin, Yeong-Gil; Lee, Ho

    2015-12-01

    A ray-driven backprojector is based on ray-tracing, which computes the length of the intersection between the ray paths and each voxel to be reconstructed. To reduce the computational burden caused by these exhaustive intersection tests, we propose a fully graphics processing unit (GPU)-based ray-driven backprojector in conjunction with a ray-culling scheme that enables straightforward parallelization without compromising the high computing performance of a GPU. The purpose of the ray-culling scheme is to reduce the number of ray-voxel intersection tests by excluding rays irrelevant to a specific voxel computation. This rejection step is based on an axis-aligned bounding box (AABB) enclosing a region of voxel projection, where eight vertices of each voxel are projected onto the detector plane. The range of the rectangular-shaped AABB is determined by min/max operations on the coordinates in the region. Using the indices of pixels inside the AABB, the rays passing through the voxel can be identified and the voxel is weighted as the length of intersection between the voxel and the ray. This procedure makes it possible to reflect voxel-level parallelization, allowing an independent calculation at each voxel, which is feasible for a GPU implementation. To eliminate redundant calculations during ray-culling, a shared-memory optimization is applied to exploit the GPU memory hierarchy. In experimental results using real measurement data with phantoms, the proposed GPU-based ray-culling scheme reconstructed a volume of resolution 28032803176 in 77 seconds from 680 projections of resolution 10243768 , which is 26 times and 7.5 times faster than standard CPU-based and GPU-based ray-driven backprojectors, respectively. Qualitative and quantitative analyses showed that the ray-driven backprojector provides high-quality reconstruction images when compared with those generated by the Feldkamp-Davis-Kress algorithm using a pixel-driven backprojector, with an average of 2.5 times

  6. Automation of dosimeters calibration for radiotherapy in secondary dosimetric calibration laboratory of the CPHR; Automatizacion de la calibracion de dosimetros de radioterapia en el laboratorio secundario de calibracion dosimetrica del CPHR

    Energy Technology Data Exchange (ETDEWEB)

    Acosta, Andy L. Romero; Lores, Stefan Gutierrez, E-mail: c19btm@frcuba.co.cu [Centro de Proteccion e Higiene de las Radiaciones (CPHR), La Habana (Cuba)

    2013-11-01

    This paper presents the design and implementation of an automated system for measurements in the calibration of reference radiation dosimeters. It was made a software application that performs the acquisition of the measured values of electric charge, calculated calibration coefficient and automates the calibration certificate issuance. These values are stored in a log file on a PC. The use of the application improves control over the calibration process, helps to humanize the work and reduces personnel exposure. The tool developed has been applied to the calibration of dosimeters radiation patterns in the LSCD of the Centro de Proteccion e Higiene de las Radiaciones, Cuba.

  7. Voxel-based structural magnetic resonance imaging (MRI study of patients with early onset schizophrenia

    Directory of Open Access Journals (Sweden)

    Suzuki Katsuaki

    2008-12-01

    Full Text Available Abstract Background Investigation into the whole brain morphology of early onset schizophrenia (EOS to date has been sparse. We studied the regional brain volumes in EOS patients, and the correlations between regional volume measures and symptom severity. Methods A total of 18 EOS patients (onset under 16 years and 18 controls matched for age, gender, parental socioeconomic status, and height were examined. Voxel-based morphometric analysis using the Brain Analysis Morphological Mapping (BAMM software package was employed to explore alterations of the regional grey (GM and white matter (WM volumes in EOS patients. Symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS. Results EOS patients had significantly reduced GM volume in the left parahippocampal, inferior frontal, and superior temporal gyri, compared with the controls. They also had less WM volume in the left posterior limb of the internal capsule and the left inferior longitudinal fasciculus. The positive symptom score of PANSS (higher values corresponding to more severe symptoms was negatively related to GM volume in the bilateral posterior cingulate gyrus. The negative symptom score was positively correlated with GM volume in the right thalamus. As for the association with WM volume, the positive symptom score of PANSS was positively related to cerebellar WM (vermis region, and negatively correlated with WM in the brain stem (pons and in the bilateral cerebellum (hemisphere region. Conclusion Our findings of regional volume alterations of GM and WM in EOS patients coincide with those of previous studies of adult onset schizophrenia patients. However, in brain regions that had no overall structural differences between EOS patients and controls (that is, the bilateral posterior cingulate gyrus, the right thalamus, the cerebellum, and the pons, within-subject analysis of EOS patients alone revealed that there were significant associations of the volume in these areas

  8. Spatial distribution of lacunarity of voxelized airborne LiDAR point clouds in various forest assemblages

    Science.gov (United States)

    Székely, Balázs; Kania, Adam; Standovár, Tibor; Heilmeier, Hermann

    2015-04-01

    Forest ecosystems have characteristic structure of features defined by various structural elements of different scales and vertical positions: shrub layers, understory vegetation, tree trunks, and branches. Furthermore in most of the cases there are superimposed structures in distributions (mosaic or island patterns) due to topography, soil variability, or even anthropogenic factors like past/present forest management activity. This multifaceted spatial context of the forests is relevant for many ecological issues, especially for maintaining forest biodiversity. Our aim in this study is twofold: (1) to quantify this structural variability laterally and vertically using lacunarity, and (2) to relate these results to relevant ecological features, i.e quantitatively described forest properties. Airborne LiDAR data of various quality and point density have been used for our study including a number of forested sites in Central and East Europe (partly Natura 2000 sites). The point clouds have been converted to voxel format and then converted to horizontal layers as images. These images were processed further for the lacunarity calculation. Areas of interest (AOIs) have been selected based on evaluation of the forested areas and auxiliary field information. The calculation has been performed for the AOIs for all available vertical data slices. The lacunarity function referring to a certain point and given vicinity varies horizontally and vertically, depending on the vegetation structure. Furthermore, the topography may also influence this property as the growth of plants, especially spacing and size of trees are influenced by the local topography and relief (e.g., slope, aspect). The comparisons of the flatland and hilly settings show interesting differences and the spatial patterns also vary differently. Because of the large amount of data resulting from these calculations, sophisticated methods are required to analyse the results. The large data amount then has been

  9. SMAP RADAR Calibration and Validation

    Science.gov (United States)

    West, R. D.; Jaruwatanadilok, S.; Chaubel, M. J.; Spencer, M.; Chan, S. F.; Chen, C. W.; Fore, A.

    2015-12-01

    The Soil Moisture Active Passive (SMAP) mission launched on Jan 31, 2015. The mission employs L-band radar and radiometer measurements to estimate soil moisture with 4% volumetric accuracy at a resolution of 10 km, and freeze-thaw state at a resolution of 1-3 km. Immediately following launch, there was a three month instrument checkout period, followed by six months of level 1 (L1) calibration and validation. In this presentation, we will discuss the calibration and validation activities and results for the L1 radar data. Early SMAP radar data were used to check commanded timing parameters, and to work out issues in the low- and high-resolution radar processors. From April 3-13 the radar collected receive only mode data to conduct a survey of RFI sources. Analysis of the RFI environment led to a preferred operating frequency. The RFI survey data were also used to validate noise subtraction and scaling operations in the radar processors. Normal radar operations resumed on April 13. All radar data were examined closely for image quality and calibration issues which led to improvements in the radar data products for the beta release at the end of July. Radar data were used to determine and correct for small biases in the reported spacecraft attitude. Geo-location was validated against coastline positions and the known positions of corner reflectors. Residual errors at the time of the beta release are about 350 m. Intra-swath biases in the high-resolution backscatter images are reduced to less than 0.3 dB for all polarizations. Radiometric cross-calibration with Aquarius was performed using areas of the Amazon rain forest. Cross-calibration was also examined using ocean data from the low-resolution processor and comparing with the Aquarius wind model function. Using all a-priori calibration constants provided good results with co-polarized measurements matching to better than 1 dB, and cross-polarized measurements matching to about 1 dB in the beta release. During the

  10. Motion as a perturbation: Measurement-guided dose estimates to moving patient voxels during modulated arc deliveries

    Energy Technology Data Exchange (ETDEWEB)

    Feygelman, Vladimir; Zhang, Geoffrey; Hunt, Dylan; Opp, Daniel [Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States); Stambaugh, Cassandra [Department of Physics, University of South Florida, Tampa, Florida 33612 (United States); Wolf, Theresa K. [Live Oak Technologies LLC, Kirkwood, Missouri 63122 (United States); Nelms, Benjamin E. [Canis Lupus LLC, Merrimac, Wisconsin 53561 (United States)

    2013-02-15

    Purpose: To present a framework for measurement-guided VMAT dose reconstruction to moving patient voxels from a known motion kernel and the static phantom data, and to validate this perturbation-based approach with the proof-of-principle experiments. Methods: As described previously, the VMAT 3D dose to a static patient can be estimated by applying a phantom measurement-guided perturbation to the treatment planning system (TPS)-calculated dose grid. The fraction dose to any voxel in the presence of motion, assuming the motion kernel is known, can be derived in a similar fashion by applying a measurement-guided motion perturbation. The dose to the diodes in a helical phantom is recorded at 50 ms intervals and is transformed into a series of time-resolved high-density volumetric dose grids. A moving voxel is propagated through this 4D dose space and the fraction dose to that voxel in the phantom is accumulated. The ratio of this motion-perturbed, reconstructed dose to the TPS dose in the phantom serves as a perturbation factor, applied to the TPS fraction dose to the similarly situated voxel in the patient. This approach was validated by the ion chamber and film measurements on four phantoms of different shape and structure: homogeneous and inhomogeneous cylinders, a homogeneous cube, and an anthropomorphic thoracic phantom. A 2D motion stage was used to simulate the motion. The stage position was synchronized with the beam start time with the respiratory gating simulator. The motion patterns were designed such that the motion speed was in the upper range of the expected tumor motion (1-1.4 cm/s) and the range exceeded the normally observed limits (up to 5.7 cm). The conformal arc plans for X or Y motion (in the IEC 61217 coordinate system) consisted of manually created narrow (3 cm) rectangular strips moving in-phase (tracking) or phase-shifted by 90 Degree-Sign (crossing) with respect to the phantom motion. The XY motion was tested with the computer-derived VMAT

  11. Calibration of the solar radio spectrometer

    Institute of Scientific and Technical Information of China (English)

    TAN ChengMing; YAN YiHua; TAN BaoLin; XU GuiRong

    2009-01-01

    This paper shows some improvements and new results of calibration of Chinese solar radio spectrom-eter by analyzing the daily calibration data recorded in the period of 1997-2007. First, the calibration coefficient is fitted for three bands (1.0-2.0 GHz, 2.6-3.8 GHz, 5.2-7.6 GHz) of the spectrometer by using the moving-average method confined by the property of the daily calibration data. By this calibration coefficient, the standard deviation of the calibration result was less than 10 sfu for 95% frequencies of 2.6-3.8 GHz band in 2003. This result is better than that calibrated with the constant coefficient. Second, the calibration coefficient is found in good correlation with local air temperature for most frequencies of 2.6-3.8 GHz band. Moreover, these results are helpful in the research of the quiet solar radio emission.

  12. Crop physiology calibration in the CLM

    Directory of Open Access Journals (Sweden)

    I. Bilionis

    2015-04-01

    scalable and adaptive scheme based on sequential Monte Carlo (SMC. The model showed significant improvement of crop productivity with the new calibrated parameters. We demonstrate that the calibrated parameters are applicable across alternative years and different sites.

  13. Calibration of the solar radio spectrometer

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    This paper shows some improvements and new results of calibration of Chinese solar radio spectrometer by analyzing the daily calibration data recorded in the period of 1997-2007. First, the calibration coefficient is fitted for three bands (1.0-2.0 GHz, 2.6-3.8 GHz, 5.2-7.6 GHz) of the spectrometer by using the moving-average method confined by the property of the daily calibration data. By this calibration coefficient, the standard deviation of the calibration result was less than 10 sfu for 95% frequencies of 2.6-3.8 GHz band in 2003. This result is better than that calibrated with the constant coefficient. Second, the calibration coefficient is found in good correlation with local air temperature for most frequencies of 2.6-3.8 GHz band. Moreover, these results are helpful in the research of the quiet solar radio emission.

  14. Calibration and Validation of Measurement System

    DEFF Research Database (Denmark)

    Kofoed, Jens Peter; Riemann, Sven; Knapp, Wilfried

    The report deals with the calibration of the measuring equipment on board the Wave Dragon, Nissum Bredning prototype.......The report deals with the calibration of the measuring equipment on board the Wave Dragon, Nissum Bredning prototype....

  15. A Pixel Moving Voxel Surface Rendering Algorithm%像素的移动体素面绘制算法

    Institute of Scientific and Technical Information of China (English)

    郑丽萍; 李光耀; 李寰

    2012-01-01

    移动立方体算法是最具影响力的等值面构造算法.本文以移动立方体算法为基础,提出了像素点移动体素面绘制算法.根据物体表面的显示特性和体素特点,利用像素点组成的边界体素绘制物体的等值面,实现物体表面的三维重建.在实验中,对一组CT图像中的骨骼组织进行三维表面重建和显示,并与用Matlab绘制函数重建的三维结果进行比较.实验分析表明,该算法能对物体进行三维重建,避免了二义性问题,但重建表面不光滑,重建花费的时间较长.%The marching cubes algorithm is the most influential isosurface construction algorithm. In this paper, a moving pixel-voxel surface rendering algorithm is proposed. According to the marching cubes algorithm, the display properties of object surface and voxel characteristics, we render the object isosurface with boundary voxel and reconstruct the 3D surface. In the experiments, reconstruct the bone tissue with the proposed algorithm and the Matlab rendering function. Finally, by comparing two experimental results, we show that this algorithm can reconstruct an object 3D surface and avoid ambiguity. But the reconstructed 3D surface is not smooth and the reconstructed time is long.

  16. Looking for Neuroimaging Markers in Frontotemporal Lobar Degeneration Clinical Trials: A Multi-Voxel Pattern Analysis Study in Granulin Disease.

    Science.gov (United States)

    Premi, Enrico; Cauda, Franco; Costa, Tommaso; Diano, Matteo; Gazzina, Stefano; Gualeni, Vera; Alberici, Antonella; Archetti, Silvana; Magoni, Mauro; Gasparotti, Roberto; Padovani, Alessandro; Borroni, Barbara

    2016-01-01

    In light of future pharmacological interventions, neuroimaging markers able to assess the response to treatment would be crucial. In Granulin (GRN) disease, preclinical data will prompt pharmacological trials in the future. Two main points need to be assessed: (1) to identify target regions in different disease stages and (2) to determine the most accurate functional and structural neuroimaging index to be used. To this aim, we have taken advantage of the multivariate approach of multi-voxel pattern analysis (MVPA) to explore the information of brain activity patterns in a cohort of GRN Thr272fs carriers at different disease stages (14 frontotemporal dementia (FTD) patients and 17 asymptomatic carriers) and a group of 33 healthy controls. We studied structural changes by voxel-based morphometry (VBM), functional connectivity by assessing salience, default mode, fronto-parietal, dorsal attentional, executive networks, and local connectivity by regional homogeneity, amplitude of low frequency fluctuations (ALFF), fractional ALFF (fALFF), degree centrality, and voxel-mirrored homotopic connectivity. In FTD patients with GRN mutation, the most predictive measure was VBM structural analysis, while in asymptomatic carriers the best predictor marker was the local connectivity measure (fALFF). Altogether, all indexes demonstrated fronto-temporo-parietal damage in GRN pathology, with widespread structural damage of fronto-parietal and temporal regions when disease is overt. MVPA could be of aid in identifying the most accurate neuroimaging marker for clinical trials. This approach was able to identify both the target region and the best neuroimaging approach, which would be specific in the different disease stages. Further studies are needed to simultaneously integrate multimodal indexes in a classifier able to trace the disease progression moving from preclinical to clinical stage of the disease.

  17. A statistical parametric mapping toolbox used for voxel-wise analysis of FDG-PET images of rat brain.

    Directory of Open Access Journals (Sweden)

    Binbin Nie

    Full Text Available PURPOSE: PET (positron emission tomography imaging researches of functional metabolism using fluorodeoxyglucose (18F-FDG of animal brain are important in neuroscience studies. FDG-PET imaging studies are often performed on groups of rats, so it is desirable to establish an objective voxel-based statistical methodology for group data analysis. MATERIAL AND METHODS: This study establishes a statistical parametric mapping (SPM toolbox (plug-ins named spmratIHEP for voxel-wise analysis of FDG-PET images of rat brain, in which an FDG-PET template and an intracranial mask image of rat brain in Paxinos & Watson space were constructed, and the default settings were modified according to features of rat brain. Compared to previous studies, our constructed rat brain template comprises not only the cerebrum and cerebellum, but also the whole olfactory bulb which made the later cognitive studies much more exhaustive. And with an intracranial mask image in the template space, the brain tissues of individuals could be extracted automatically. Moreover, an atlas space is used for anatomically labeling the functional findings in the Paxinos & Watson space. In order to standardize the template image with the atlas accurately, a synthetic FDG-PET image with six main anatomy structures is constructed from the atlas, which performs as a target image in the co-registration. RESULTS: The spatial normalization procedure is evaluated, by which the individual rat brain images could be standardized into the Paxinos & Watson space successfully and the intracranial tissues could also be extracted accurately. The practical usability of this toolbox is evaluated using FDG-PET functional images from rats with left side middle cerebral artery occlusion (MCAO in comparison to normal control rats. And the two-sample t-test statistical result is almost related to the left side MCA. CONCLUSION: We established a toolbox of SPM8 named spmratIHEP for voxel-wise analysis of FDG

  18. Shallow subsurface control on earthquake damage patterns: first results from a 3D geological voxel model study (Tokyo Lowland, Japan)

    Science.gov (United States)

    Stafleu, Jan; Busschers, Freek; Tanabe, Susumu

    2016-04-01

    The Tokyo Lowland is situated in a Neogene sedimentary basin near the triple junction of the North American, Pacific, and Philippine tectonic plates. The basin is filled with Neogene and Quaternary sediments up to a thickness of 3 km. In the upper 70 m of the basin, thick sequences of soft Holocene sediments occur which are assumed to have played a key role in the spatial variation of damage intensity during the 1923 Kanto earthquake (Magnitude 7.9 to 8.3). Historical records show this earthquake destroyed large parts of the Tokyo urban area which in that time was largely made up by wooden houses. Although the epicentre was 70 km to the southwest of Tokyo, severe damage occurred north of the city centre, presumably due to ground motion amplification in the soft Holocene sediments in the shallow subsurface. In order to assess the presumed relation between the damage pattern of the 1923 earthquake and the occurrence of soft Holocene sediments in the shallow subsurface, we constructed a 3D geological voxel model of the central part of the Tokyo Lowland. The model was constructed using a methodology originally developed for the lowlands of the Netherlands. The modelling workflow basically consists of three steps. First, some 10,000 borehole descriptions (gathered for geomechanical purposes), were subdivided into geological units that have uniform sediment characteristics, using both lithological and geomechanical (N-value) criteria. Second, 2D bounding surfaces were constructed, representing tops and bases of the geological units. These surfaces were used to place each voxel (100 by 100 by 1 m) within the correct geological unit. The N-values and lithological units in the borehole descriptions were subsequently used to perform a 3D stochastic interpolation of N-value and lithological class within each geological unit. Using a vertical voxel stack analysis, we were able to create a map showing the accumulated thickness of soft muds in the Holocene succession. A

  19. Structural differences in gray matter between glider pilots and non-pilots. A voxel based morphometry study.

    Directory of Open Access Journals (Sweden)

    Tosif eAhamed

    2014-11-01

    Full Text Available Glider flying is a unique skill that requires pilots to control an aircraft at high speeds in three dimensions and amidst frequent full body rotations. In the present study we investigated the neural correlates of flying a glider using voxel-based morphometry (VBM. The comparison between gray matter densities of 15 glider pilots and a control group of 15 non-pilots exhibited significant gray matter density increases in left ventral premotor cortex, anterior cingulate cortex and the supplementary eye field. We posit that the identified regions might be associated with cognitive and motor processes related to flying such as joystick control, visuo-vestibular interaction and oculomotor control.

  20. Effects of voxel size and iterative reconstruction parameters on the spatial resolution of 99mTc SPECT/CT

    OpenAIRE

    Kappadath, S. Cheenu

    2011-01-01

    The purpose of this study was to evaluate the effects of voxel size and iterative reconstruction parameters on the radial and tangential resolution for 99mTc SPECT as a function of radial distance from isocenter. SPECT/CT scans of eight coplanar point sources of size smaller than 1 mm3 containing high concentration 99mTc solution were acquired on a SPECT/CT system with 5/8 inch NaI(Tl) detector and low-energy, high-resolution collimator. The tomographic projection images were acquired in step...

  1. Motion Correction of Single-Voxel Spectroscopy by Independent Component Analysis Applied to Spectra From Nonanesthetized Pediatric Subjects

    DEFF Research Database (Denmark)

    de Nijs, Robin; Miranda, Maria J.; Hansen, Lars Kai

    2009-01-01

    , but at the cost of increased sensitivity to random noise. Neither independent component analysis nor outlier identification with multiple comparisons has this problem. These two algorithms are novel in this context. The peak height values of the metabolites were increased compared to the mean of all acquisitions......For single-voxel spectroscopy, the acquisition of the spectrum is typically repeated n times and then combined with a factor in order to improve the signal-to-noise ratio. In practice, the acquisitions are not only affected by random noise but also by physiologic motion and subject movements. Since...

  2. Accelerated cerebral white matter development in preterm infants: a voxel-based morphometry study with diffusion tensor MR imaging

    DEFF Research Database (Denmark)

    Giménez, Mónica; Born, A Peter; Nagy, Zoltan;

    2008-01-01

    stratum. While some earlier findings in preterm infants have suggested developmental delays, the results of this study are more consistent with accelerated white matter development, possibly as a result of increased sensorimotor stimulation in the extrauterine environment. These results are the first......Twenty-seven preterm infants were compared to 10 full-term infants at term equivalent age using a voxel-based analysis of diffusion tensor imaging of the brain. Preterm infants exhibited higher fractional anisotropy values, which may suggest accelerated maturation, in the location of the sagittal...

  3. Optimal Reliability-Based Code Calibration

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Kroon, I. B.; Faber, M. H.

    1994-01-01

    Calibration of partial safety factors is considered in general, including classes of structures where no code exists beforehand. The partial safety factors are determined such that the difference between the reliability for the different structures in the class considered and a target reliability...... level is minimized. Code calibration on a decision theoretical basis is also considered and it is shown how target reliability indices can be calibrated. Results from code calibration for rubble mound breakwater designs are shown....

  4. Calibration of a Parallel Kinematic Machine Tool

    Institute of Scientific and Technical Information of China (English)

    HE Xiao-mei; DING Hong-sheng; FU Tie; XIE Dian-huang; XU Jin-zhong; LI Hua-feng; LIU Hui-lin

    2006-01-01

    A calibration method is presented to enhance the static accuracy of a parallel kinematic machine tool by using a coordinate measuring machine and a laser tracker. According to the established calibration model and the calibration experiment, the factual 42 kinematic parameters of BKX-I parallel kinematic machine tool are obtained. By circular tests the comparison is made between the calibrated and the uncalibrated parameters and shows that there is 80% improvement in accuracy of this machine tool.

  5. A Careful Consideration of the Calibration Concept

    Science.gov (United States)

    Phillips, S. D.; Estler, W. T.; Doiron, T.; Eberhardt, K. R.; Levenson, M. S.

    2001-01-01

    This paper presents a detailed discussion of the technical aspects of the calibration process with emphasis on the definition of the measurand, the conditions under which the calibration results are valid, and the subsequent use of the calibration results in measurement uncertainty statements. The concepts of measurement uncertainty, error, systematic error, and reproducibility are also addressed as they pertain to the calibration process. PMID:27500027

  6. Calibrating thermal behavior of electronics

    Energy Technology Data Exchange (ETDEWEB)

    Chainer, Timothy J.; Parida, Pritish R.; Schultz, Mark D.

    2017-01-03

    A method includes determining a relationship between indirect thermal data for a processor and a measured temperature associated with the processor, during a calibration process, obtaining the indirect thermal data for the processor during actual operation of the processor, and determining an actual significant temperature associated with the processor during the actual operation using the indirect thermal data for the processor during actual operation of the processor and the relationship.

  7. Nonlinear Observers for Gyro Calibration

    Science.gov (United States)

    Thienel, Julie; Sanner, Robert M.

    2003-01-01

    Nonlinear observers for gyro calibration are presented. The first observer estimates a constant gyro bias. The second observer estimates scale factor errors. The third observer estimates the gyro alignment for three orthogonal gyros. The convergence properties of all three observers are discussed. Additionally, all three observers are coupled with a nonlinear control algorithm. The stability of each of the resulting closed loop systems is analyzed. Simulated test results are presented for each system.

  8. Calibrating thermal behavior of electronics

    Science.gov (United States)

    Chainer, Timothy J.; Parida, Pritish R.; Schultz, Mark D.

    2016-05-31

    A method includes determining a relationship between indirect thermal data for a processor and a measured temperature associated with the processor, during a calibration process, obtaining the indirect thermal data for the processor during actual operation of the processor, and determining an actual significant temperature associated with the processor during the actual operation using the indirect thermal data for the processor during actual operation of the processor and the relationship.

  9. Model Calibration in Watershed Hydrology

    Science.gov (United States)

    Yilmaz, Koray K.; Vrugt, Jasper A.; Gupta, Hoshin V.; Sorooshian, Soroosh

    2009-01-01

    Hydrologic models use relatively simple mathematical equations to conceptualize and aggregate the complex, spatially distributed, and highly interrelated water, energy, and vegetation processes in a watershed. A consequence of process aggregation is that the model parameters often do not represent directly measurable entities and must, therefore, be estimated using measurements of the system inputs and outputs. During this process, known as model calibration, the parameters are adjusted so that the behavior of the model approximates, as closely and consistently as possible, the observed response of the hydrologic system over some historical period of time. This Chapter reviews the current state-of-the-art of model calibration in watershed hydrology with special emphasis on our own contributions in the last few decades. We discuss the historical background that has led to current perspectives, and review different approaches for manual and automatic single- and multi-objective parameter estimation. In particular, we highlight the recent developments in the calibration of distributed hydrologic models using parameter dimensionality reduction sampling, parameter regularization and parallel computing.

  10. Unassisted 3D camera calibration

    Science.gov (United States)

    Atanassov, Kalin; Ramachandra, Vikas; Nash, James; Goma, Sergio R.

    2012-03-01

    With the rapid growth of 3D technology, 3D image capture has become a critical part of the 3D feature set on mobile phones. 3D image quality is affected by the scene geometry as well as on-the-device processing. An automatic 3D system usually assumes known camera poses accomplished by factory calibration using a special chart. In real life settings, pose parameters estimated by factory calibration can be negatively impacted by movements of the lens barrel due to shaking, focusing, or camera drop. If any of these factors displaces the optical axes of either or both cameras, vertical disparity might exceed the maximum tolerable margin and the 3D user may experience eye strain or headaches. To make 3D capture more practical, one needs to consider unassisted (on arbitrary scenes) calibration. In this paper, we propose an algorithm that relies on detection and matching of keypoints between left and right images. Frames containing erroneous matches, along with frames with insufficiently rich keypoint constellations, are detected and discarded. Roll, pitch yaw , and scale differences between left and right frames are then estimated. The algorithm performance is evaluated in terms of the remaining vertical disparity as compared to the maximum tolerable vertical disparity.

  11. Variability among polysulphone calibration curves

    Energy Technology Data Exchange (ETDEWEB)

    Casale, G R [University of Rome ' La Sapienza' , Physics Department, P.le A. Moro 2, I-00185, Rome (Italy); Borra, M [ISPESL - Istituto Superiore per la Prevenzione E la Sicurezza del Lavoro, Occupational Hygiene Department, Via Fontana Candida 1, I-0040 Monteporzio Catone (RM) (Italy); Colosimo, A [University of Rome ' La Sapienza' , Department of Human Physiology and Pharmacology, P.le A. Moro 2, I-00185, Rome (Italy); Colucci, M [ISPESL - Istituto Superiore per la Prevenzione E la Sicurezza del Lavoro, Occupational Hygiene Department, Via Fontana Candida 1, I-0040 Monteporzio Catone (RM) (Italy); Militello, A [ISPESL - Istituto Superiore per la Prevenzione E la Sicurezza del Lavoro, Occupational Hygiene Department, Via Fontana Candida 1, I-0040 Monteporzio Catone (RM) (Italy); Siani, A M [University of Rome ' La Sapienza' , Physics Department, P.le A. Moro 2, I-00185, Rome (Italy); Sisto, R [ISPESL - Istituto Superiore per la Prevenzione E la Sicurezza del Lavoro, Occupational Hygiene Department, Via Fontana Candida 1, I-0040 Monteporzio Catone (RM) (Italy)

    2006-09-07

    Within an epidemiological study regarding the correlation between skin pathologies and personal ultraviolet (UV) exposure due to solar radiation, 14 field campaigns using polysulphone (PS) dosemeters were carried out at three different Italian sites (urban, semi-rural and rural) in every season of the year. A polysulphone calibration curve for each field experiment was obtained by measuring the ambient UV dose under almost clear sky conditions and the corresponding change in the PS film absorbance, prior and post exposure. Ambient UV doses were measured by well-calibrated broad-band radiometers and by electronic dosemeters. The dose-response relation was represented by the typical best fit to a third-degree polynomial and it was parameterized by a coefficient multiplying a cubic polynomial function. It was observed that the fit curves differed from each other in the coefficient only. It was assessed that the multiplying coefficient was affected by the solar UV spectrum at the Earth's surface whilst the polynomial factor depended on the photoinduced reaction of the polysulphone film. The mismatch between the polysulphone spectral curve and the CIE erythemal action spectrum was responsible for the variability among polysulphone calibration curves. The variability of the coefficient was related to the total ozone amount and the solar zenith angle. A mathematical explanation of such a parameterization was also discussed.

  12. PACS photometer calibration block analysis

    CERN Document Server

    Moór, A; Kiss, Cs; Balog, Z; Billot, N; Marton, G

    2013-01-01

    The absolute stability of the PACS bolometer response over the entire mission lifetime without applying any corrections is about 0.5% (standard deviation) or about 8% peak-to-peak. This fantastic stability allows us to calibrate all scientific measurements by a fixed and time-independent response file, without using any information from the PACS internal calibration sources. However, the analysis of calibration block observations revealed clear correlations of the internal source signals with the evaporator temperature and a signal drift during the first half hour after the cooler recycling. These effects are small, but can be seen in repeated measurements of standard stars. From our analysis we established corrections for both effects which push the stability of the PACS bolometer response to about 0.2% (stdev) or 2% in the blue, 3% in the green and 5% in the red channel (peak-to-peak). After both corrections we still see a correlation of the signals with PACS FPU temperatures, possibly caused by parasitic h...

  13. Net analyte signal calculation for multivariate calibration

    NARCIS (Netherlands)

    Ferre, J.; Faber, N.M.

    2003-01-01

    A unifying framework for calibration and prediction in multivariate calibration is shown based on the concept of the net analyte signal (NAS). From this perspective, the calibration step can be regarded as the calculation of a net sensitivity vector, whose length is the amount of net signal when the

  14. Optimal, Reliability-Based Code Calibration

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard

    2002-01-01

    Reliability based code calibration is considered in this paper. It is described how the results of FORM based reliability analysis may be related to the partial safety factors and characteristic values. The code calibration problem is presented in a decision theoretical form and it is discussed how...... of reliability based code calibration of LRFD based design codes....

  15. Code Calibration as a Decision Problem

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Kroon, I. B.; Faber, M. H.

    1993-01-01

    Calibration of partial coefficients for a class of structures where no code exists is considered. The partial coefficients are determined such that the difference between the reliability for the different structures in the class considered and a target reliability level is minimized. Code...... calibration on a decision theoretical basis is discussed. Results from code calibration for rubble mound breakwater designs are shown....

  16. Systems and methods of eye tracking calibration

    DEFF Research Database (Denmark)

    2014-01-01

    Methods and systems to facilitate eye tracking control calibration are provided. One or more objects are displayed on a display of a device, where the one or more objects are associated with a function unrelated to a calculation of one or more calibration parameters. The one or more calibration...

  17. 14 CFR 33.45 - Calibration tests.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Calibration tests. 33.45 Section 33.45... STANDARDS: AIRCRAFT ENGINES Block Tests; Reciprocating Aircraft Engines § 33.45 Calibration tests. (a) Each engine must be subjected to the calibration tests necessary to establish its power characteristics...

  18. 14 CFR 33.85 - Calibration tests.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Calibration tests. 33.85 Section 33.85... STANDARDS: AIRCRAFT ENGINES Block Tests; Turbine Aircraft Engines § 33.85 Calibration tests. (a) Each engine must be subjected to those calibration tests necessary to establish its power characteristics and...

  19. Development of a Monte Carlo software to photon transportation in voxel structures using graphic processing units; Desenvolvimento de um software de Monte Carlo para transporte de fotons em estruturas de voxels usando unidades de processamento grafico

    Energy Technology Data Exchange (ETDEWEB)

    Bellezzo, Murillo

    2014-09-01

    As the most accurate method to estimate absorbed dose in radiotherapy, Monte Carlo Method (MCM) has been widely used in radiotherapy treatment planning. Nevertheless, its efficiency can be improved for clinical routine applications. In this thesis, the CUBMC code is presented, a GPU-based MC photon transport algorithm for dose calculation under the Compute Unified Device Architecture (CUDA) platform. The simulation of physical events is based on the algorithm used in PENELOPE, and the cross section table used is the one generated by the MATERIAL routine, also present in PENELOPE code. Photons are transported in voxel-based geometries with different compositions. There are two distinct approaches used for transport simulation. The rst of them forces the photon to stop at every voxel frontier, the second one is the Woodcock method, where the photon ignores the existence of borders and travels in homogeneous fictitious media. The CUBMC code aims to be an alternative of Monte Carlo simulator code that, by using the capability of parallel processing of graphics processing units (GPU), provide high performance simulations in low cost compact machines, and thus can be applied in clinical cases and incorporated in treatment planning systems for radiotherapy. (author)

  20. Rapid Determination of Costunolide and Dehydrocostuslactone in Human Plasma Sample and Chinese Patent Medicine Xiang Sha Yang Wei Capsule Using HPLC-DAD Coupled with Second-order Calibration

    Institute of Scientific and Technical Information of China (English)

    刘亚娟; 吴海龙; 朱绍华; 康超; 许慧; 苏志义; 谷惠文; 俞汝勤

    2012-01-01

    A novel methodology that combines high performance liquid chromatography with photodiode-array detector (HPLC-DAD) coupled with second-order calibration method based on alternating trilinear decomposition (ATLD) algorithm was used in determination of the effective constituents such as costunolide and dehydrocostuslactone, in plasma sample and Chinese patent medicine Xiang Sha Yang Wei (XSYW) capsule. Complicated systems such as plasma and Chinese patent medicine which have intricate components are tedious to isolate and purify. The problem that chromatographic peaks are heavily overlapped among the analytes and interferents from the background matrices can be resolved, and the satisfactory quantification results have been gained with the help of the ATLD algorithm which utilized "mathematical separation" instead of partial "physical or chemical separation". Meanwhile, HPLC-MS/MS method was used to validate the accuracy of the proposed determination method.

  1. The effect of voxel size on dose distribution in Varian Clinac iX 6 MV photon beam using Monte Carlo simulation

    Science.gov (United States)

    Yani, Sitti; Dirgayussa, I. Gde E.; Rhani, Moh. Fadhillah; Haryanto, Freddy; Arif, Idam

    2015-09-01

    Recently, Monte Carlo (MC) calculation method has reported as the most accurate method of predicting dose distributions in radiotherapy. The MC code system (especially DOSXYZnrc) has been used to investigate the different voxel (volume elements) sizes effect on the accuracy of dose distributions. To investigate this effect on dosimetry parameters, calculations were made with three different voxel sizes. The effects were investigated with dose distribution calculations for seven voxel sizes: 1 × 1 × 0.1 cm3, 1 × 1 × 0.5 cm3, and 1 × 1 × 0.8 cm3. The 1 × 109 histories were simulated in order to get statistical uncertainties of 2%. This simulation takes about 9-10 hours to complete. Measurements are made with field sizes 10 × 10 cm2 for the 6 MV photon beams with Gaussian intensity distribution FWHM 0.1 cm and SSD 100.1 cm. MC simulated and measured dose distributions in a water phantom. The output of this simulation i.e. the percent depth dose and dose profile in dmax from the three sets of calculations are presented and comparisons are made with the experiment data from TTSH (Tan Tock Seng Hospital, Singapore) in 0-5 cm depth. Dose that scored in voxels is a volume averaged estimate of the dose at the center of a voxel. The results in this study show that the difference between Monte Carlo simulation and experiment data depend on the voxel size both for percent depth dose (PDD) and profile dose. PDD scan on Z axis (depth) of water phantom, the big difference obtain in the voxel size 1 × 1 × 0.8 cm3 about 17%. In this study, the profile dose focused on high gradient dose area. Profile dose scan on Y axis and the big difference get in the voxel size 1 × 1 × 0.1 cm3 about 12%. This study demonstrated that the arrange voxel in Monte Carlo simulation becomes important.

  2. The effect of voxel size on dose distribution in Varian Clinac iX 6 MV photon beam using Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Yani, Sitti, E-mail: sitti.yani@s.itb.ac.id [Nuclear Physics and Biophysics Division, Physics Department, Institut Teknologi Bandung (Indonesia); Akademi Kebidanan Pelita Ibu, Kendari (Indonesia); Dirgayussa, I Gde E.; Haryanto, Freddy; Arif, Idam [Nuclear Physics and Biophysics Division, Physics Department, Institut Teknologi Bandung (Indonesia); Rhani, Moh. Fadhillah [Tan Tock Seng Hospital (Singapore)

    2015-09-30

    Recently, Monte Carlo (MC) calculation method has reported as the most accurate method of predicting dose distributions in radiotherapy. The MC code system (especially DOSXYZnrc) has been used to investigate the different voxel (volume elements) sizes effect on the accuracy of dose distributions. To investigate this effect on dosimetry parameters, calculations were made with three different voxel sizes. The effects were investigated with dose distribution calculations for seven voxel sizes: 1 × 1 × 0.1 cm{sup 3}, 1 × 1 × 0.5 cm{sup 3}, and 1 × 1 × 0.8 cm{sup 3}. The 1 × 10{sup 9} histories were simulated in order to get statistical uncertainties of 2%. This simulation takes about 9-10 hours to complete. Measurements are made with field sizes 10 × 10 cm2 for the 6 MV photon beams with Gaussian intensity distribution FWHM 0.1 cm and SSD 100.1 cm. MC simulated and measured dose distributions in a water phantom. The output of this simulation i.e. the percent depth dose and dose profile in d{sub max} from the three sets of calculations are presented and comparisons are made with the experiment data from TTSH (Tan Tock Seng Hospital, Singapore) in 0-5 cm depth. Dose that scored in voxels is a volume averaged estimate of the dose at the center of a voxel. The results in this study show that the difference between Monte Carlo simulation and experiment data depend on the voxel size both for percent depth dose (PDD) and profile dose. PDD scan on Z axis (depth) of water phantom, the big difference obtain in the voxel size 1 × 1 × 0.8 cm{sup 3} about 17%. In this study, the profile dose focused on high gradient dose area. Profile dose scan on Y axis and the big difference get in the voxel size 1 × 1 × 0.1 cm{sup 3} about 12%. This study demonstrated that the arrange voxel in Monte Carlo simulation becomes important.

  3. Calculation of Specific Absorbed Fraction Based on VCH Voxel Model%基于可视中国数字人体素模型的比吸收分数计算

    Institute of Scientific and Technical Information of China (English)

    刘洋; 贾向红; 许峰; 刘谦

    2012-01-01

    目的 开展器官比吸收分数的计算研究,以定量计算人体的内照射剂量.方法 在高分辨可视中国人三维解剖结构数据集基础上,对原始图片进行分割、标识、赋值和低抽样,构建了基于体素数据的内辐射模型.采用基于蒙特卡洛方法的MCNPX软件,模拟了光子在人体器官组织间的传输过程,得到了各能量下源器官对目标器官的比吸收分数,并与中国数学模型的计算结果进行了比较.结果 两组数据在趋势上具有相似性,说明了计算方法的正确性;体素模型的计算结果较数学模型大,主要源自模型间器官质量和器官距离的不同;数学模型中部分结果具有明显差异性,说明其计算结果可能不准确.结论 基于中国数字人体素模型计算的比吸收分数,提供了更为准确和可靠的数据.%Objective To quantitatively calculate the internal radiation dose of the human body by studying the organ specific absorbed fractions ( SAF). Methods The voxel internal radiation model was developed with segmenting, labeling, assigning and sampling the original images, based on the three-dimensional anatomical structure datasets from high resolution Visible Chinese Human (VCH). Using MCNPX Monte Carlo code, the transport procedure of photon were simulated, and then the SAFs at various energies were obtained and compared with those from the Chinese mathematical model. Results The method was proved correct by the similar trend in the two sets of data. SAFs from the voxel model were higher than those from the mathematical model due to the discrepancies of organ mass and inter-organ distance. Part of the SAFs from the mathematical model were found quite different, which might lead to inaccurate results. Conclusion The SAF from the VCH voxel model may provide more accurate and reliable data.

  4. 42 CFR 493.1255 - Standard: Calibration and calibration verification procedures.

    Science.gov (United States)

    2010-10-01

    ..., if possible, traceable to a reference method or reference material of known value; and (ii) Including... 42 Public Health 5 2010-10-01 2010-10-01 false Standard: Calibration and calibration verification... for Nonwaived Testing Analytic Systems § 493.1255 Standard: Calibration and calibration...

  5. Spectral calibration for convex grating imaging spectrometer

    Science.gov (United States)

    Zhou, Jiankang; Chen, Xinhua; Ji, Yiqun; Chen, Yuheng; Shen, Weimin

    2013-12-01

    Spectral calibration of imaging spectrometer plays an important role for acquiring target accurate spectrum. There are two spectral calibration types in essence, the wavelength scanning and characteristic line sampling. Only the calibrated pixel is used for the wavelength scanning methods and he spectral response function (SRF) is constructed by the calibrated pixel itself. The different wavelength can be generated by the monochromator. The SRF is constructed by adjacent pixels of the calibrated one for the characteristic line sampling methods. And the pixels are illuminated by the narrow spectrum line and the center wavelength of the spectral line is exactly known. The calibration result comes from scanning method is precise, but it takes much time and data to deal with. The wavelength scanning method cannot be used in field or space environment. The characteristic line sampling method is simple, but the calibration precision is not easy to confirm. The standard spectroscopic lamp is used to calibrate our manufactured convex grating imaging spectrometer which has Offner concentric structure and can supply high resolution and uniform spectral signal. Gaussian fitting algorithm is used to determine the center position and the Full-Width-Half-Maximum(FWHM)of the characteristic spectrum line. The central wavelengths and FWHMs of spectral pixels are calibrated by cubic polynomial fitting. By setting a fitting error thresh hold and abandoning the maximum deviation point, an optimization calculation is achieved. The integrated calibration experiment equipment for spectral calibration is developed to enhance calibration efficiency. The spectral calibration result comes from spectral lamp method are verified by monochromator wavelength scanning calibration technique. The result shows that spectral calibration uncertainty of FWHM and center wavelength are both less than 0.08nm, or 5.2% of spectral FWHM.

  6. Gemini Planet Imager Observational Calibrations II: Detector Performance and Calibration

    CERN Document Server

    Ingraham, Patrick; Sadakuni, Naru; Ruffio, Jean-Baptiste; Maire, Jerome; Chilcote, Jeff; Larkin, James; Marchis, Franck; Galicher, Raphael; Weiss, Jason

    2014-01-01

    The Gemini Planet Imager is a newly commissioned facility instrument designed to measure the near-infrared spectra of young extrasolar planets in the solar neighborhood and obtain imaging polarimetry of circumstellar disks. GPI's science instrument is an integral field spectrograph that utilizes a HAWAII-2RG detector with a SIDECAR ASIC readout system. This paper describes the detector characterization and calibrations performed by the GPI Data Reduction Pipeline to compensate for effects including bad/hot/cold pixels, persistence, non-linearity, vibration induced microphonics and correlated read noise.

  7. Photometric Calibrations for the SIRTF Infrared Spectrograph

    CERN Document Server

    Morris, P W; Herter, T L; Armus, L; Houck, J; Sloan, G

    2002-01-01

    The SIRTF InfraRed Spectrograph (IRS) is faced with many of the same calibration challenges that were experienced in the ISO SWS calibration program, owing to similar wavelength coverage and overlapping spectral resolutions of the two instruments. Although the IRS is up to ~300 times more sensitive and without moving parts, imposing unique calibration challenges on their own, an overlap in photometric sensitivities of the high-resolution modules with the SWS grating sections allows lessons, resources, and certain techniques from the SWS calibration programs to be exploited. We explain where these apply in an overview of the IRS photometric calibration planning.

  8. Structural brain abnormalities in patients with Parkinson's disease with visual hallucinations: a comparative voxel-based analysis.

    Science.gov (United States)

    Gama, Romulo Lopes; Bruin, Veralice Meireles Sales; Távora, Daniel Gurgel Fernandes; Duran, Fábio L S; Bittencourt, Lia; Tufik, Sergio

    2014-06-01

    The objective is to evaluate clinical characteristics and cerebral alterations in Parkinson's disease (PD) patients with diurnal visual hallucinations (VHs). Assessment was performed using magnetic resonance image (MRI) and voxel-based morphometry (VBM). Thirty-nine patients with PD (53.8%) and ten controls were studied. Voxel based morphology analysis was performed. Eleven patients presented diurnal VHs and among these, six had cognitive dysfunction. Patients with VHs performed worse in the mentation-related UPDRS I (p=0.005) and motor-related UPDRS III (p=0.02). Patients with VHs showed significant clusters of reduced grey matter volume compared to controls in the left opercula frontal gyrus and left superior frontal gyrus. PD without hallucinations demonstrated reduced grey matter volume in the left superior frontal gyrus compared to controls. Comparisons between patients with VHs regarding the presence of cognitive dysfunction showed that cases with cognitive dysfunction as compared to those without cognitive dysfunction showed significant clusters of reduced grey matter volume in the left opercular frontal gyrus. Cases without cognitive dysfunction had reduced grey matter substance in the left insula and left trigonal frontal gyrus. Judging from our findings, an abnormal frontal cortex, particularly left sided insula, frontal opercular, trigonal frontal gyrus and orbital frontal would make PD patients vulnerable to hallucinations. Compromise of the left operculum distinguished cases with VHs and cognitive dysfunction. Our findings reinforce the theoretical concept of a top-down visual processing in the genesis of VHs in PD.

  9. Monte Carlo fast dose calculator for proton radiotherapy: application to a voxelized geometry representing a patient with prostate cancer.

    Science.gov (United States)

    Yepes, Pablo; Randeniya, Sharmalee; Taddei, Phillip J; Newhauser, Wayne D

    2009-01-07

    The Monte Carlo method is used to provide accurate dose estimates in proton radiation therapy research. While it is more accurate than commonly used analytical dose calculations, it is computationally intense. The aim of this work was to characterize for a clinical setup the fast dose calculator (FDC), a Monte Carlo track-repeating algorithm based on GEANT4. FDC was developed to increase computation speed without diminishing dosimetric accuracy. The algorithm used a database of proton trajectories in water to calculate the dose of protons in heterogeneous media. The extrapolation from water to 41 materials was achieved by scaling the proton range and the scattering angles. The scaling parameters were obtained by comparing GEANT4 dose distributions with those calculated with FDC for homogeneous phantoms. The FDC algorithm was tested by comparing dose distributions in a voxelized prostate cancer patient as calculated with well-known Monte Carlo codes (GEANT4 and MCNPX). The track-repeating approach reduced the CPU time required for a complete dose calculation in a voxelized patient anatomy by more than two orders of magnitude, while on average reproducing the results from the Monte Carlo predictions within 2% in terms of dose and within 1 mm in terms of distance.

  10. Combining terrestrial stereophotogrammetry, DGPS and GIS-based 3D voxel modelling in the volumetric recording of archaeological features

    Science.gov (United States)

    Orengo, Hector A.

    2013-02-01

    Archaeological recording of structures and excavations in high mountain areas is greatly hindered by the scarce availability of both space, to transport material, and time. The Madriu-Perafita-Claror, InterAmbAr and PCR Mont Lozère high mountain projects have documented hundreds of archaeological structures and carried out many archaeological excavations. These projects required the development of a technique which could record both structures and the process of an archaeological excavation in a fast and reliable manner. The combination of DGPS, close-range terrestrial stereophotogrammetry and voxel based GIS modelling offered a perfect solution since it helped in developing a strategy which would obtain all the required data on-site fast and with a high degree of precision. These data are treated off-site to obtain georeferenced orthoimages covering both the structures and the excavation process from which site and excavation plans can be created. The proposed workflow outputs also include digital surface models and volumetric models of the excavated areas from which topography and archaeological profiles were obtained by voxel-based GIS procedures. In this way, all the graphic recording required by standard archaeological practices was met.

  11. Dyslexia and voxel-based morphometry: correlations between five behavioural measures of dyslexia and gray and white matter volumes.

    Science.gov (United States)

    Tamboer, Peter; Scholte, H Steven; Vorst, Harrie C M

    2015-10-01

    In voxel-based morphometry studies of dyslexia, the relation between causal theories of dyslexia and gray matter (GM) and white matter (WM) volume alterations is still under debate. Some alterations are consistently reported, but others failed to reach significance. We investigated GM alterations in a large sample of Dutch students (37 dyslexics and 57 non-dyslexics) with two analyses: group differences in local GM and total GM and WM volume and correlations between GM and WM volumes and five behavioural measures. We found no significant group differences after corrections for multiple comparisons although total WM volume was lower in the group of dyslexics when age was partialled out. We presented an overview of uncorrected clusters of voxels (p  200) with reduced or increased GM volume. We found four significant correlations between factors of dyslexia representing various behavioural measures and the clusters found in the first analysis. In the whole sample, a factor related to performances in spelling correlated negatively with GM volume in the left posterior cerebellum. Within the group of dyslexics, a factor related to performances in Dutch-English rhyme words correlated positively with GM volume in the left and right caudate nucleus and negatively with increased total WM volume. Most of our findings were in accordance with previous reports. A relatively new finding was the involvement of the caudate nucleus. We confirmed the multiple cognitive nature of dyslexia and suggested that experience greatly influences anatomical alterations depending on various subtypes of dyslexia, especially in a student sample.

  12. A fourth gradient to overcome slice dependent phase effects of voxel-sized coils in planar arrays.

    Science.gov (United States)

    Bosshard, John C; Eigenbrodt, Edwin P; McDougall, Mary P; Wright, Steven M

    2010-01-01

    The signals from an array of densely spaced long and narrow receive coils for MRI are complicated when the voxel size is of comparable dimension to the coil size. The RF coil causes a phase gradient across each voxel, which is dependent on the distance from the coil, resulting in a slice dependent shift of k-space. A fourth gradient coil has been implemented and used with the system's gradient set to create a gradient field which varies with slice. The gradients are pulsed together to impart a slice dependent phase gradient to compensate for the slice dependent phase due to the RF coils. However the non-linearity in the fourth gradient which creates the desired slice dependency also results in a through-slice phase ramp, which disturbs normal slice refocusing and leads to additional signal cancelation and reduced field of view. This paper discusses the benefits and limitations of using a fourth gradient coil to compensate for the phase due to RF coils.

  13. Muon Energy Calibration of the MINOS Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Miyagawa, Paul S.

    2004-09-01

    MINOS is a long-baseline neutrino oscillation experiment designed to search for conclusive evidence of neutrino oscillations and to measure the oscillation parameters precisely. MINOS comprises two iron tracking calorimeters located at Fermilab and Soudan. The Calibration Detector at CERN is a third MINOS detector used as part of the detector response calibration programme. A correct energy calibration between these detectors is crucial for the accurate measurement of oscillation parameters. This thesis presents a calibration developed to produce a uniform response within a detector using cosmic muons. Reconstruction of tracks in cosmic ray data is discussed. This data is utilized to calculate calibration constants for each readout channel of the Calibration Detector. These constants have an average statistical error of 1.8%. The consistency of the constants is demonstrated both within a single run and between runs separated by a few days. Results are presented from applying the calibration to test beam particles measured by the Calibration Detector. The responses are calibrated to within 1.8% systematic error. The potential impact of the calibration on the measurement of oscillation parameters by MINOS is also investigated. Applying the calibration reduces the errors in the measured parameters by {approx} 10%, which is equivalent to increasing the amount of data by 20%.

  14. Muon Energy Calibration of the MINOS Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Miyagawa, Paul S. [Somerville College, Oxford (United Kingdom)

    2004-01-01

    MINOS is a long-baseline neutrino oscillation experiment designed to search for conclusive evidence of neutrino oscillations and to measure the oscillation parameters precisely. MINOS comprises two iron tracking calorimeters located at Fermilab and Soudan. The Calibration Detector at CERN is a third MINOS detector used as part of the detector response calibration programme. A correct energy calibration between these detectors is crucial for the accurate measurement of oscillation parameters. This thesis presents a calibration developed to produce a uniform response within a detector using cosmic muons. Reconstruction of tracks in cosmic ray data is discussed. This data is utilized to calculate calibration constants for each readout channel of the Calibration Detector. These constants have an average statistical error of 1.8%. The consistency of the constants is demonstrated both within a single run and between runs separated by a few days. Results are presented from applying the calibration to test beam particles measured by the Calibration Detector. The responses are calibrated to within 1.8% systematic error. The potential impact of the calibration on the measurement of oscillation parameters by MINOS is also investigated. Applying the calibration reduces the errors in the measured parameters by ~ 10%, which is equivalent to increasing the amount of data by 20%.

  15. Calibration of Models Using Groundwater Age (Invited)

    Science.gov (United States)

    Sanford, W. E.

    2009-12-01

    Water-resource managers are frequently concerned with the long-term ability of a groundwater system to deliver volumes of water for both humans and ecosystems under natural and anthropogenic stresses. Analysis of how a groundwater system responds to such stresses usually involves the construction and calibration of a numerical groundwater-flow model. The calibration procedure usually involves the use of both groundwater-level and flux observations. Water-level data are often more abundant, and thus the availability of flux data can be critical, with well discharge and base flow to streams being most often available. Lack of good flux data however is a common occurrence, especially in more arid climates where the sustainability of the water supply may be even more in question. Environmental tracers are frequently being used to estimate the “age” of a water sample, which represents the time the water has been in the subsurface since its arrival at the water table. Groundwater ages provide flux-related information and can be used successfully to help calibrate groundwater models if porosity is well constrained, especially when there is a paucity of other flux data. As several different methods of simulating groundwater age and tracer movement are possible, a review is presented here of the advantages, disadvantages, and potential pitfalls of the various numerical and tracer methods used in model calibration. The usefulness of groundwater ages for model calibration depends on the ability both to interpret a tracer so as to obtain an apparent observed age, and to use a numerical model to obtain an equivalent simulated age observation. Different levels of simplicity and assumptions accompany different methods for calculating the equivalent simulated age observation. The advantages of computational efficiency in certain methods can be offset by error associated with the underlying assumptions. Advective travel-time calculation using path-line tracking in finite

  16. "Calibration-on-the-spot": How to calibrate an EMCCD camera from its images.

    Science.gov (United States)

    Mortensen, Kim I; Flyvbjerg, Henrik

    2016-07-06

    In order to count photons with a camera, the camera must be calibrated. Photon counting is necessary, e.g., to determine the precision of localization-based super-resolution microscopy. Here we present a protocol that calibrates an EMCCD camera from information contained in isolated, diffraction-limited spots in any image taken by the camera, thus making dedicated calibration procedures redundant by enabling calibration post festum, from images filed without calibration information.

  17. Calibration-on-the-spot”: How to calibrate an EMCCD camera from its images

    DEFF Research Database (Denmark)

    Mortensen, Kim; Flyvbjerg, Henrik

    2016-01-01

    In order to count photons with a camera, the camera must be calibrated. Photon counting is necessary, e.g., to determine the precision of localization-based super-resolution microscopy. Here we present a protocol that calibrates an EMCCD camera from information contained in isolated, diffraction......-limited spots in any image taken by the camera, thus making dedicated calibration procedures redundant by enabling calibration post festum, from images filed without calibration information....

  18. Verification of L-band SAR calibration

    Science.gov (United States)

    Larson, R. W.; Jackson, P. L.; Kasischke, E.

    1985-01-01

    Absolute calibration of a digital L-band SAR system to an accuracy of better than 3 dB has been verified. This was accomplished with a calibration signal generator that produces the phase history of a point target. This signal relates calibration values to various SAR data sets. Values of radar cross-section (RCS) of reference reflectors were obtained using a derived calibration relationship for the L-band channel on the ERIM/CCRS X-C-L SAR system. Calibrated RCS values were compared to known RCS values of each reference reflector for verification and to obtain an error estimate. The calibration was based on the radar response to 21 calibrated reference reflectors.

  19. Calibration of the Cherenkov Telescope Array

    CERN Document Server

    Gaug, Markus; Berge, David; Reyes, Raquel de los; Doro, Michele; Foerster, Andreas; Maccarone, Maria Concetta; Parsons, Dan; van Eldik, Christopher

    2015-01-01

    The construction of the Cherenkov Telescope Array is expected to start soon. We will present the baseline methods and their extensions currently foreseen to calibrate the observatory. These are bound to achieve the strong requirements on allowed systematic uncertainties for the reconstructed gamma-ray energy and flux scales, as well as on the pointing resolution, and on the overall duty cycle of the observatory. Onsite calibration activities are designed to include a robust and efficient calibration of the telescope cameras, and various methods and instruments to achieve calibration of the overall optical throughput of each telescope, leading to both inter-telescope calibration and an absolute calibration of the entire observatory. One important aspect of the onsite calibration is a correct understanding of the atmosphere above the telescopes, which constitutes the calorimeter of this detection technique. It is planned to be constantly monitored with state-of-the-art instruments to obtain a full molecular and...

  20. Radio Interferometric Calibration Using The SAGE Algorithm

    CERN Document Server

    Kazemi, S; Zaroubi, S; de Bruyn, A G; Koopmans, L V E; Noordam, J

    2010-01-01

    The aim of the new generation of radio synthesis arrays such as LOFAR and SKA is to achieve much higher sensitivity, resolution and frequency coverage than what is available now. To accomplish this goal, the accuracy of the calibration techniques used is of considerable importance. Moreover, since these telescopes produce huge amounts of data, speed of convergence of calibration is a major bottleneck. The errors in calibration are due to system noise (sky and instrumental) as well as the estimation errors introduced by the calibration technique itself, which we call "solver noise". We define solver noise as the "distance" between the optimal solution, the true value of the unknowns corrupted by the system noise, and the solution obtained by calibration. We present the Space Alternating Generalized Expectation Maximization (SAGE) calibration technique, which is a modification of the Expectation Maximization algorithm, and compare its performance with the traditional Least Squares calibration based on the level...

  1. Calibration of TOB+ Thermometer's Cards

    CERN Document Server

    Banitt, Daniel

    2014-01-01

    Motivation - Under the new upgrade of the CMS detector the working temperature of the trackers had been reduced to -27 Celsius degrees. Though the thermal sensors themselves (Murata and Fenwal thermistors) are effective at these temperatures, the max1542 PLC (programmable logic controller) cards, interpreting the resistance of the thermal sensors into DC counts usable by the DCS (detector control system), are not designed for these temperatures in which the counts exceed their saturation and therefor had to be replaced. In my project I was in charge of handling the emplacement and calibration of the new PLC cards to the TOB (tracker outer barrel) control system.

  2. AFFTC Standard Airspeed Calibration Procedures

    Science.gov (United States)

    1981-06-01

    25x0UIXQXQ Results of groundLpeed course calibration are normally pre- sented in the following plots: 1. .AvP vs Vi Ŗ. All vs V ic 3. AMPC vs Mic .4...8217Average AfPeavgpo, tion correction AM /AH 10-5 per and figure V 9 PC PC feet . fu V AYpc" x q3 @ , Average position avg corred ion (AM @ AMPC /AVPC...instrument error 0 M ic From and 0), Mach number p Chart 8.5 in reference’l (AFTR 6273) (DO AMPPacer poqition error calibra- Pc tion at9 S( AMpc /’,HpC)p

  3. Neuronal injury in the motor cortex after chronic stroke and lower limb motor impairment:a voxel-based lesion symptom mapping study

    Institute of Scientific and Technical Information of China (English)

    Alexandria M. Reynolds; Denise M. Peters; Jennifer M. C. Vendemia; Lenwood P. Smith; Raymond C. Sweet; Gordon C. Baylis; Debra Krotish; Stacy L Fritz

    2014-01-01

    Many studies have examined motor impairments using voxel-based lesion symptom mapping, but few are reported regarding the corresponding relationship between cerebral cortex injury and lower limb motor impairment analyzed using this technique. This study correlated neuro-nal injury in the cerebral cortex of 16 patients with chronic stroke based on a voxel-based lesion symptom mapping analysis. Neuronal injury in the corona radiata, caudate nucleus and putamen of patients with chronic stroke could predict walking speed. The behavioral measure scores were consistent with motor deifcits expected after damage to the cortical motor system due to stroke. These ifndings suggest that voxel-based lesion symptom mapping may provide a more accurate prognosis of motor recovery from chronic stroke according to neuronal injury in cerebral motor cortex.

  4. Pulse-based internal calibration of polarimetric SAR

    DEFF Research Database (Denmark)

    Dall, Jørgen; Skou, Niels; Christensen, Erik Lintz

    1994-01-01

    Internal calibration greatly diminishes the dependence on calibration target deployment compared to external calibration. Therefore the Electromagnetics Institute (EMI) at the Technical University of Denmark (TUD) has equipped its polarimetric SAR, EMISAR, with several calibration loops and devel......Internal calibration greatly diminishes the dependence on calibration target deployment compared to external calibration. Therefore the Electromagnetics Institute (EMI) at the Technical University of Denmark (TUD) has equipped its polarimetric SAR, EMISAR, with several calibration loops...

  5. Crop physiology calibration in CLM

    Directory of Open Access Journals (Sweden)

    I. Bilionis

    2014-10-01

    Full Text Available Farming is using more terrestrial ground, as population increases and agriculture is increasingly used for non-nutritional purposes such as biofuel production. This agricultural expansion exerts an increasing impact on the terrestrial carbon cycle. In order to understand the impact of such processes, the Community Land Model (CLM has been augmented with a CLM-Crop extension that simulates the development of three crop types: maize, soybean, and spring wheat. The CLM-Crop model is a complex system that relies on a suite of parametric inputs that govern plant growth under a given atmospheric forcing and available resources. CLM-Crop development used measurements of gross primary productivity and net ecosystem exchange from AmeriFlux sites to choose parameter values that optimize crop productivity in the model. In this paper we calibrate these parameters for one crop type, soybean, in order to provide a faithful projection in terms of both plant development and net carbon exchange. Calibration is performed in a Bayesian framework by developing a scalable and adaptive scheme based on sequential Monte Carlo (SMC.

  6. Input calibration for negative originals

    Science.gov (United States)

    Tuijn, Chris

    1995-04-01

    One of the major challenges in the prepress environment consists of controlling the electronic color reproduction process such that a perfect match of any original can be realized. Whether this goal can be reached depends on many factors such as the dynamic range of the input device (scanner, camera), the color gamut of the output device (dye sublimation printer, ink-jet printer, offset), the color management software etc. The characterization of the color behavior of the peripheral devices is therefore very important. Photographs and positive transparents reflect the original scene pretty well; for negative originals, however, there is no obvious link to either the original scene or a particular print of the negative under consideration. In this paper, we establish a method to scan negatives and to convert the scanned data to a calibrated RGB space, which is known colorimetrically. This method is based on the reconstruction of the original exposure conditions (i.e., original scene) which generated the negative. Since the characteristics of negative film are quite diverse, a special calibration is required for each combination of scanner and film type.

  7. Reproducibility of BOLD, perfusion, and CMRO2 measurements with calibrated-BOLD fMRI.

    Science.gov (United States)

    Leontiev, Oleg; Buxton, Richard B

    2007-03-01

    The coupling of changes in cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO(2)) during brain activation can be characterized by an empirical index, n, defined as the ratio between fractional CBF change and fractional CMRO(2) change. The combination of blood oxygenation level dependent (BOLD) imaging with CBF measurements from arterial spin labeling (ASL) provides a potentially powerful experimental approach for measuring n, but the reproducibility of the technique previously has not been assessed. In this study, inter-subject variance and intra-subject reproducibility of the method were determined. Block design %BOLD and %CBF responses to visual stimulation and mild hypercapnia (5% CO(2)) were measured, and these data were used to compute the BOLD scaling factor M, %CMRO(2) change with activation, and the coupling index n. Reproducibility was determined for three approaches to defining regions-of-interest (ROIs): 1) Visual area V1 determined from prior retinotopic maps, 2) BOLD-activated voxels from a separate functional localizer, and 3) CBF-activated voxels from a separate functional localizer. For estimates of %BOLD, %CMRO(2) and n, intra-subject reproducibility was found to be best for regions selected according to CBF activation. Among all fMRI measurements, estimates of n were the most robust and were substantially more stable within individual subjects (coefficient of variation, CV=7.4%) than across the subject pool (CV=36.9%). The stability of n across days, despite wider variability of CBF and CMRO(2) responses, suggests that the reproducibility of blood flow changes is limited by variation in the oxidative metabolic demand. We conclude that the calibrated BOLD approach provides a highly reproducible measurement of n that can serve as a useful quantitative probe of the coupling of blood flow and energy metabolism in the brain.

  8. Third COS FUV Lifetime Calibration Program: Flatfield and Flux Calibrations

    Science.gov (United States)

    Debes, J. H.; Becker, G.; Roman-Duval, J.; Ely, J.; Massa, D.; Oliveira, C.; Plesha, R.; Proffitt, C.; Taylor, J.

    2016-10-01

    As part of the calibration of the third lifetime position (LP3) of the Cosmic Origins Spectrograph (COS) Far-Ultraviolet (FUV) detector, observations of WD 0308-565 were obtained with the G130M, G160M, and G140L gratings and observations of GD 71 were obtained in the G160M grating through the Point Source Aperture (PSA) to derive low-order flatfields (L-flats) and sensitivities at LP3. Observations were executed for all CENWAVES and all FP-POS with the exception of G130M/1055 and G130M/1096, which remained at LP2. The derivation of the L-flats and sensitivities at LP3 differed from their LP1 and LP2 counterparts in a few key ways, which we describe in this report. Firstly, we quantified a cut-off in spatial frequency that we assigned to the L-flats. Secondly, we derived a new method for simultaneously fitting both the L-flats, pixel-to-pixel flats (P-flats), and sensitvities which we compared to our previous method of separately fitting L-flats and sensitivities. These new methods produce comparable results, but provide us with an external test on the robustness of each approach individually. The results of our work show that with the new profile extraction routines, sensitivities, and L-flats, the relative and absolute flux calibration accuracies (1% and 2% respectively) at LP3 are slightly improved relative to previous locations on the COS FUV detector.

  9. Another look at volume self-calibration: calibration and self-calibration within a pinhole model of Scheimpflug cameras

    Science.gov (United States)

    Cornic, Philippe; Illoul, Cédric; Cheminet, Adam; Le Besnerais, Guy; Champagnat, Frédéric; Le Sant, Yves; Leclaire, Benjamin

    2016-09-01

    We address calibration and self-calibration of tomographic PIV experiments within a pinhole model of cameras. A complete and explicit pinhole model of a camera equipped with a 2-tilt angles Scheimpflug adapter is presented. It is then used in a calibration procedure based on a freely moving calibration plate. While the resulting calibrations are accurate enough for Tomo-PIV, we confirm, through a simple experiment, that they are not stable in time, and illustrate how the pinhole framework can be used to provide a quantitative evaluation of geometrical drifts in the setup. We propose an original self-calibration method based on global optimization of the extrinsic parameters of the pinhole model. These methods are successfully applied to the tomographic PIV of an air jet experiment. An unexpected by-product of our work is to show that volume self-calibration induces a change in the world frame coordinates. Provided the calibration drift is small, as generally observed in PIV, the bias on the estimated velocity field is negligible but the absolute location cannot be accurately recovered using standard calibration data.

  10. Compositionality and the angular gyrus: A multi-voxel similarity analysis of the semantic composition of nouns and verbs.

    Science.gov (United States)

    Boylan, Christine; Trueswell, John C; Thompson-Schill, Sharon L

    2015-11-01

    The cognitive and neural systems that enable conceptual processing must support the ability to combine (and recombine) concepts to form an infinite number of ideas. Two candidate neural systems for conceptual combination-the left anterior temporal lobe (ATL) and the left angular gyrus (AG)-have been characterized as "semantic hubs" due to both functional and anatomical properties; however, these two regions likely support different aspects of composition. Here we consider two hypotheses for the role of AG in conceptual combination, both of which differ from a putative role for the ATL in "feature-based" combinatorics (i.e., meaning derived by combining concepts' features). Firstly, we examine whether AG is more sensitive to function-argument relations of the sort that arise when a predicate is combined with its arguments. Secondly, we examine the non-mutually exclusive possibility that AG represents information carried on a verb in particular, whether this be information about event composition or about thematic relations denoted uniquely by verbs. We identified voxels that respond differentially to two-word versus one-word stimuli, and we measured the similarity of the patterns in these voxels evoked by (1) pairs of two-word phrases that shared a noun that was an argument, thus sharing function-argument composition (e.g. eats meat and with meat), in comparison with two-word phrases that shared only a noun, not an argument (e.g., eats meat and tasty meat); and (2) stimulus pairs that shared only an event (operationalized here as sharing a verb; e.g. eats meat and eats quickly), in comparison to both of the above. We found that activity patterns in left AG tracked information relating to the presence of an event-denoting verb in a pair of two-word phrases. We also found that the neural similarity in AG voxel patterns between two phrases sharing a verb correlated with subjects' ratings of how similar the meanings of those two verb phrases were. These findings

  11. Construction and evaluation of F-18 FDG PET probabilistic MAP for voxel based analysis of the rat brain

    Energy Technology Data Exchange (ETDEWEB)

    Im, K. C.; Kim, J. S.; Na, Y. S.; Moon, D. H.; Ryu, J. S. [Asan Medical Center, Seoul (Korea, Republic of)

    2007-07-01

    The purpose of this study was to develop F-18 FDG PET and MRI template for normal rat brain. Also, feasibility of SPM in detailed regional analysis of molecular changes in the rat brain was explored for F-18 FDG PET imaging of a model of traumatic brain injury (TBI). Ten normal rats were scanned with PET and MRI. The PET images were acquired with 3D mode using microPET focus 120 scanner after injection of 37 MBq F-18 FDG. T2-weighted MR images were acquired using 4.7T MRI system. A MRI-based spatial normalization was used. The PET images were coregistered to T2-weighted MR images. Maximum mutual information (MMI) registrations and affine spatial normalizations were performed using SPM2. The spatial normalization of the MRI to the standard MRI was applied to the integral images. The normalized PET images were averaged voxel wise to create PET template. Eight TBI model rats were subjected to a moderate lateral fluid percussion injury. At 2 days, 1 week, 3 weeks and 5 weeks post FPI, PET images of 8 TBI rats were acquired 4 times. TBI PET images were realigned, spatially normalized to a created PET-template and smoothed (8 mm FWHM). To assess the extent and severity of significant hypo metabolic lesions in TBI compared to normal controls were obtained by a two-sided t-test of SPM (uncorrected p < 0.001, 50 voxels). Visually acceptable PET and MRI templates were created. Registration errors were negligible when MMI procedure was used to register a translated or rotated image volume. Thirty-two PET studies of 8 TBI model subjects were obtained. SPM analysis showed injured distribution of decrease F-18 FDG uptake in TBI rats compared with normal rats. In SPM analysis, the extent and severity of significant hypo metabolic lesions were decreased according to a significant effect of time. At 5 weeks injured animals showed F-18 FDG uptake recovery using SPM analysis. These results indicate that voxel-based method will be useful for future longitudinal studies of rat brain.

  12. SU-E-T-642: PTV Is the Voxel-Wise Worst-Case of CTV in Prostate Photon Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Harrington, D; Schild, S; Wong, W; Vora, S; Liu, W [Mayo Clinic Arizona, Phoenix, AZ (United States)

    2015-06-15

    Purpose: To examine the adequacy of the planning target volume (PTV) dose distribution as the worst-case representation of clinical target volume (CTV) dose distribution in prostate volumetric-modulated arc therapy (VMAT) plans. Methods: Ten intact prostate cancer cases treated by VMAT at our institution were randomly selected. Isocenter was shifted in the three cardinal directions by a displacement equal to the PTV expansion on the CTV (±3 mm) for a total of six shifted plans per original plan. Rotationally-perturbed plans were generated with a couch rotation of ±1° to simulate patient yaw. The eight perturbed dose distributions were recalculated in the treatment planning system using the same, fixed fluence map as the original plan. The voxel-wise worst-case CTV dose distribution was constructed from the minimum value per voxel from the eight perturbed doses. The resulting dose volume histograms (DVH) were evaluated for statistical correlation between the worst-case CTV and nominal PTV dose distributions based on D95% by Wilcoxon signed-rank test with significance level p ≤ 0.05. Results: Inspection demonstrates the PTV DVH in the nominal dose distribution is bounded by the CTV DVH in the worst-case dose distribution. Comparison of D95% for the two dose distributions by Wilcoxon signed-rank test gives p = 0.131. Therefore the null hypothesis cannot be rejected since the difference in median values is not statistically significant. Conclusion: The assumption that the nominal dose distribution for PTV represents the worst-case dose distribution for CTV appears valid for the ten plans under examination. Although the worst-case dose distribution is unphysical since the dose per voxel is chosen independently, it serves as a lower bound for the possible CTV coverage. Furthermore, this is consistent with the unphysical