SPAM-assisted partial volume correction algorithm for PET

Energy Technology Data Exchange (ETDEWEB)

Cho, Sung Il; Kang, Keon Wook; Lee, Jae Sung; Lee, Dong Soo; Chung, June Key; Soh, Kwang Sup; Lee, Myung Chul [College of Medicine, Seoul National Univ., Seoul (Korea, Republic of)

2000-07-01

A probabilistic atlas of the human brain (Statistical Probability Anatomical Maps: SPAM) was developed by the International Consortium for Brain Mapping (ICBM). It will be a good frame for calculating volume of interest (VOI) according to statistical variability of human brain in many fields of brain images. We show that we can get more exact quantification of the counts in VOI by using SPAM in the correlation of partial volume effect for simulated PET image. The MRI of a patient with dementia was segmented into gray matter and white matter, and then they were smoothed to PET resolution. Simulated PET image was made by adding one third of the smoothed white matter to the smoothed gray matter. Spillover effect and partial volume effect were corrected for this simulated PET image with the aid of the segmented and smoothed MR images. The images were spatially normalized to the average brain MRI atlas of ICBM, and were multiplied by the probablities of 98 VOIs of SPAM images of Montreal Neurological Institute. After the correction of partial volume effect, the counts of frontal, partietal, temporal, and occipital lobes were increased by 38{+-}6%, while those of hippocampus and amygdala by 4{+-}3%. By calculating the counts in VOI using the product of probability of SPAM images and counts in the simulated PET image, the counts increase and become closer to the true values. SPAM-assisted partial volume correction is useful for quantification of VOIs in PET images.

SPAM-assisted partial volume correction algorithm for PET

International Nuclear Information System (INIS)

Cho, Sung Il; Kang, Keon Wook; Lee, Jae Sung; Lee, Dong Soo; Chung, June Key; Soh, Kwang Sup; Lee, Myung Chul

2000-01-01

A probabilistic atlas of the human brain (Statistical Probability Anatomical Maps: SPAM) was developed by the International Consortium for Brain Mapping (ICBM). It will be a good frame for calculating volume of interest (VOI) according to statistical variability of human brain in many fields of brain images. We show that we can get more exact quantification of the counts in VOI by using SPAM in the correlation of partial volume effect for simulated PET image. The MRI of a patient with dementia was segmented into gray matter and white matter, and then they were smoothed to PET resolution. Simulated PET image was made by adding one third of the smoothed white matter to the smoothed gray matter. Spillover effect and partial volume effect were corrected for this simulated PET image with the aid of the segmented and smoothed MR images. The images were spatially normalized to the average brain MRI atlas of ICBM, and were multiplied by the probablities of 98 VOIs of SPAM images of Montreal Neurological Institute. After the correction of partial volume effect, the counts of frontal, partietal, temporal, and occipital lobes were increased by 38±6%, while those of hippocampus and amygdala by 4±3%. By calculating the counts in VOI using the product of probability of SPAM images and counts in the simulated PET image, the counts increase and become closer to the true values. SPAM-assisted partial volume correction is useful for quantification of VOIs in PET images

The impact of 3D volume of interest definition on accuracy and precision of activity estimation in quantitative SPECT and planar processing methods

Science.gov (United States)

He, Bin; Frey, Eric C.

2010-06-01

Accurate and precise estimation of organ activities is essential for treatment planning in targeted radionuclide therapy. We have previously evaluated the impact of processing methodology, statistical noise and variability in activity distribution and anatomy on the accuracy and precision of organ activity estimates obtained with quantitative SPECT (QSPECT) and planar (QPlanar) processing. Another important factor impacting the accuracy and precision of organ activity estimates is accuracy of and variability in the definition of organ regions of interest (ROI) or volumes of interest (VOI). The goal of this work was thus to systematically study the effects of VOI definition on the reliability of activity estimates. To this end, we performed Monte Carlo simulation studies using randomly perturbed and shifted VOIs to assess the impact on organ activity estimates. The 3D NCAT phantom was used with activities that modeled clinically observed 111In ibritumomab tiuxetan distributions. In order to study the errors resulting from misdefinitions due to manual segmentation errors, VOIs of the liver and left kidney were first manually defined. Each control point was then randomly perturbed to one of the nearest or next-nearest voxels in three ways: with no, inward or outward directional bias, resulting in random perturbation, erosion or dilation, respectively, of the VOIs. In order to study the errors resulting from the misregistration of VOIs, as would happen, e.g. in the case where the VOIs were defined using a misregistered anatomical image, the reconstructed SPECT images or projections were shifted by amounts ranging from -1 to 1 voxels in increments of with 0.1 voxels in both the transaxial and axial directions. The activity estimates from the shifted reconstructions or projections were compared to those from the originals, and average errors were computed for the QSPECT and QPlanar methods, respectively. For misregistration, errors in organ activity estimations were

The impact of 3D volume of interest definition on accuracy and precision of activity estimation in quantitative SPECT and planar processing methods

Energy Technology Data Exchange (ETDEWEB)

He Bin [Division of Nuclear Medicine, Department of Radiology, New York Presbyterian Hospital-Weill Medical College of Cornell University, New York, NY 10021 (United States); Frey, Eric C, E-mail: bih2006@med.cornell.ed, E-mail: efrey1@jhmi.ed [Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical Institutions, Baltimore, MD 21287-0859 (United States)

2010-06-21

Accurate and precise estimation of organ activities is essential for treatment planning in targeted radionuclide therapy. We have previously evaluated the impact of processing methodology, statistical noise and variability in activity distribution and anatomy on the accuracy and precision of organ activity estimates obtained with quantitative SPECT (QSPECT) and planar (QPlanar) processing. Another important factor impacting the accuracy and precision of organ activity estimates is accuracy of and variability in the definition of organ regions of interest (ROI) or volumes of interest (VOI). The goal of this work was thus to systematically study the effects of VOI definition on the reliability of activity estimates. To this end, we performed Monte Carlo simulation studies using randomly perturbed and shifted VOIs to assess the impact on organ activity estimates. The 3D NCAT phantom was used with activities that modeled clinically observed {sup 111}In ibritumomab tiuxetan distributions. In order to study the errors resulting from misdefinitions due to manual segmentation errors, VOIs of the liver and left kidney were first manually defined. Each control point was then randomly perturbed to one of the nearest or next-nearest voxels in three ways: with no, inward or outward directional bias, resulting in random perturbation, erosion or dilation, respectively, of the VOIs. In order to study the errors resulting from the misregistration of VOIs, as would happen, e.g. in the case where the VOIs were defined using a misregistered anatomical image, the reconstructed SPECT images or projections were shifted by amounts ranging from -1 to 1 voxels in increments of with 0.1 voxels in both the transaxial and axial directions. The activity estimates from the shifted reconstructions or projections were compared to those from the originals, and average errors were computed for the QSPECT and QPlanar methods, respectively. For misregistration, errors in organ activity estimations

Construction site Voice Operated Information System (VOIS) test

Science.gov (United States)

Lawrence, Debbie J.; Hettchen, William

1991-01-01

The Voice Activated Information System (VAIS), developed by USACERL, allows inspectors to verbally log on-site inspection reports on a hand held tape recorder. The tape is later processed by the VAIS, which enters the information into the system's database and produces a written report. The Voice Operated Information System (VOIS), developed by USACERL and Automated Sciences Group, through a ESACERL cooperative research and development agreement (CRDA), is an improved voice recognition system based on the concepts and function of the VAIS. To determine the applicability of the VOIS to Corps of Engineers construction projects, Technology Transfer Test Bad (T3B) funds were provided to the Corps of Engineers National Security Agency (NSA) Area Office (Fort Meade) to procure and implement the VOIS, and to train personnel in its use. This report summarizes the NSA application of the VOIS to quality assurance inspection of radio frequency shielding and to progress payment logs, and concludes that the VOIS is an easily implemented system that can offer improvements when applied to repetitive inspection procedures. Use of VOIS can save time during inspection, improve documentation storage, and provide flexible retrieval of stored information.

Volume of interest-based [18F]fluorodeoxyglucose PET discriminates MCI converting to Alzheimer's disease from healthy controls. A European Alzheimer's Disease Consortium (EADC study

Directory of Open Access Journals (Sweden)

M. Pagani

2015-01-01

Full Text Available An emerging issue in neuroimaging is to assess the diagnostic reliability of PET and its application in clinical practice. We aimed at assessing the accuracy of brain FDG-PET in discriminating patients with MCI due to Alzheimer's disease and healthy controls. Sixty-two patients with amnestic MCI and 109 healthy subjects recruited in five centers of the European AD Consortium were enrolled. Group analysis was performed by SPM8 to confirm metabolic differences. Discriminant analyses were then carried out using the mean FDG uptake values normalized to the cerebellum computed in 45 anatomical volumes of interest (VOIs in each hemisphere (90 VOIs as defined in the Automated Anatomical Labeling (AAL Atlas and on 12 meta-VOIs, bilaterally, obtained merging VOIs with similar anatomo-functional characteristics. Further, asymmetry indexes were calculated for both datasets. Accuracy of discrimination by a Support Vector Machine (SVM and the AAL VOIs was tested against a validated method (PALZ. At the voxel level SMP8 showed a relative hypometabolism in the bilateral precuneus, and posterior cingulate, temporo-parietal and frontal cortices. Discriminant analysis classified subjects with an accuracy ranging between .91 and .83 as a function of data organization. The best values were obtained from a subset of 6 meta-VOIs plus 6 asymmetry values reaching an area under the ROC curve of .947, significantly larger than the one obtained by the PALZ score. High accuracy in discriminating MCI converters from healthy controls was reached by a non-linear classifier based on SVM applied on predefined anatomo-functional regions and inter-hemispheric asymmetries. Data pre-processing was automated and simplified by an in-house created Matlab-based script encouraging its routine clinical use. Further validation toward nonconverter MCI patients with adequately long follow-up is needed.

Partial volume and aliasing artefacts in helical cone-beam CT

International Nuclear Information System (INIS)

Zou Yu; Sidky, Emil Y; Pan, Xiaochuan

2004-01-01

A generalization of the quasi-exact algorithms of Kudo et al (2000 IEEE Trans. Med. Imaging 19 902-21) is developed that allows for data acquisition in a 'practical' frame for clinical diagnostic helical, cone-beam computed tomography (CT). The algorithm is investigated using data that model nonlinear partial volume averaging. This investigation leads to an understanding of aliasing artefacts in helical, cone-beam CT image reconstruction. An ad hoc scheme is proposed to mitigate artefacts due to the nonlinear partial volume and aliasing artefacts

Validation of simple quantification methods for 18F FP CIT PET Using Automatic Delineation of volumes of interest based on statistical probabilistic anatomical mapping and isocontour margin setting

International Nuclear Information System (INIS)

Kim, Yong Il; Im, Hyung Jun; Paeng, Jin Chul; Lee, Jae Sung; Eo, Jae Seon; Kim, Dong Hyun; Kim, Euishin E.; Kang, Keon Wook; Chung, June Key; Lee Dong Soo

2012-01-01

18 F FP CIT positron emission tomography (PET) is an effective imaging for dopamine transporters. In usual clinical practice, 18 F FP CIT PET is analyzed visually or quantified using manual delineation of a volume of interest (VOI) fir the stratum. in this study, we suggested and validated two simple quantitative methods based on automatic VOI delineation using statistical probabilistic anatomical mapping (SPAM) and isocontour margin setting. Seventy five 18 F FP CIT images acquired in routine clinical practice were used for this study. A study-specific image template was made and the subject images were normalized to the template. afterwards, uptakes in the striatal regions and cerebellum were quantified using probabilistic VOI based on SPAM. A quantitative parameter, Q SPAM, was calculated to simulate binding potential. additionally, the functional volume of each striatal region and its uptake were measured in automatically delineated VOI using isocontour margin setting. Uptake volume product(Q UVP) was calculated for each striatal region. Q SPAMa nd Q UVPw as calculated for each visual grading and the influence of cerebral atrophy on the measurements was tested. Image analyses were successful in all the cases. Both the Q SPAMa nd Q UVPw ere significantly different according to visual grading (0.001). The agreements of Q UVPa nd Q SPAMw ith visual grading were slight to fair for the caudate nucleus (K= 0.421 and 0.291, respectively) and good to prefect to the putamen (K=0.663 and 0.607, respectively). Also, Q SPAMa nd Q UVPh ad a significant correlation with each other (0.001). Cerebral atrophy made a significant difference in Q SPAMa nd Q UVPo f the caudate nuclei regions with decreased 18 F FP CIT uptake. Simple quantitative measurements of Q SPAMa nd Q UVPs howed acceptable agreement with visual grad-ing. although Q SPAMi n some group may be influenced by cerebral atrophy, these simple methods are expected to be effective in the quantitative analysis of F FP

Cone-beam volume CT mammographic imaging: feasibility study

Science.gov (United States)

Chen, Biao; Ning, Ruola

2001-06-01

X-ray projection mammography, using a film/screen combination or digital techniques, has proven to be the most effective imaging modality for early detection of breast cancer currently available. However, the inherent superimposition of structures makes small carcinoma (a few millimeters in size) difficult to detect in the occultation case or in dense breasts, resulting in a high false positive biopsy rate. The cone-beam x-ray projection based volume imaging using flat panel detectors (FPDs) makes it possible to obtain three-dimensional breast images. This may benefit diagnosis of the structure and pattern of the lesion while eliminating hard compression of the breast. This paper presents a novel cone-beam volume CT mammographic imaging protocol based on the above techniques. Through computer simulation, the key issues of the system and imaging techniques, including the x-ray imaging geometry and corresponding reconstruction algorithms, x-ray characteristics of breast tissues, x-ray setting techniques, the absorbed dose estimation and the quantitative effect of x-ray scattering on image quality, are addressed. The preliminary simulation results support the proposed cone-beam volume CT mammographic imaging modality in respect to feasibility and practicability for mammography. The absorbed dose level is comparable to that of current two-view mammography and would not be a prominent problem for this imaging protocol. Compared to traditional mammography, the proposed imaging protocol with isotropic spatial resolution will potentially provide significantly better low contrast detectability of breast tumors and more accurate location of breast lesions.

Interobserver and Intraobserver Reproducibility with Volume Dynamic Contrast Enhanced Computed Tomography (DCE-CT) in Gastroesophageal Junction Cancer

DEFF Research Database (Denmark)

Lundsgaard Hansen, Martin; Fallentin, Eva; Axelsen, Thomas

2016-01-01

-dimensional (2D) fixed ROIs) placed in the tumor periphery, (II) 2-dimensional regions of interest (2D-ROI) along the tumor border in the tumor center, and (III) 3-dimensional volumes of interest (3D-VOI) containing the entire tumor volume. Arterial flow, blood volume and permeability (k(trans)) were recorded...

Efficient transmission of compressed data for remote volume visualization.

Science.gov (United States)

Krishnan, Karthik; Marcellin, Michael W; Bilgin, Ali; Nadar, Mariappan S

2006-09-01

One of the goals of telemedicine is to enable remote visualization and browsing of medical volumes. There is a need to employ scalable compression schemes and efficient client-server models to obtain interactivity and an enhanced viewing experience. First, we present a scheme that uses JPEG2000 and JPIP (JPEG2000 Interactive Protocol) to transmit data in a multi-resolution and progressive fashion. The server exploits the spatial locality offered by the wavelet transform and packet indexing information to transmit, in so far as possible, compressed volume data relevant to the clients query. Once the client identifies its volume of interest (VOI), the volume is refined progressively within the VOI from an initial lossy to a final lossless representation. Contextual background information can also be made available having quality fading away from the VOI. Second, we present a prioritization that enables the client to progressively visualize scene content from a compressed file. In our specific example, the client is able to make requests to progressively receive data corresponding to any tissue type. The server is now capable of reordering the same compressed data file on the fly to serve data packets prioritized as per the client's request. Lastly, we describe the effect of compression parameters on compression ratio, decoding times and interactivity. We also present suggestions for optimizing JPEG2000 for remote volume visualization and volume browsing applications. The resulting system is ideally suited for client-server applications with the server maintaining the compressed volume data, to be browsed by a client with a low bandwidth constraint.

MR-based automatic delineation of volumes of interest in human brain PET images using probability maps

DEFF Research Database (Denmark)

Svarer, Claus; Madsen, Karina; Hasselbalch, Steen G.

2005-01-01

subjects' MR-images, where VOI sets have been defined manually. High-resolution structural MR-images and 5-HT(2A) receptor binding PET-images (in terms of (18)F-altanserin binding) from 10 healthy volunteers and 10 patients with mild cognitive impairment were included for the analysis. A template including...... 35 VOIs was manually delineated on the subjects' MR images. Through a warping algorithm template VOI sets defined from each individual were transferred to the other subjects MR-images and the voxel overlap was compared to the VOI set specifically drawn for that particular individual. Comparisons were...... delineation of the VOI set. The approach was also shown to work equally well in individuals with pronounced cerebral atrophy. Probability-map-based automatic delineation of VOIs is a fast, objective, reproducible, and safe way to assess regional brain values from PET or SPECT scans. In addition, the method...

GPU-Based 3D Cone-Beam CT Image Reconstruction for Large Data Volume

Directory of Open Access Journals (Sweden)

Xing Zhao

2009-01-01

Full Text Available Currently, 3D cone-beam CT image reconstruction speed is still a severe limitation for clinical application. The computational power of modern graphics processing units (GPUs has been harnessed to provide impressive acceleration of 3D volume image reconstruction. For extra large data volume exceeding the physical graphic memory of GPU, a straightforward compromise is to divide data volume into blocks. Different from the conventional Octree partition method, a new partition scheme is proposed in this paper. This method divides both projection data and reconstructed image volume into subsets according to geometric symmetries in circular cone-beam projection layout, and a fast reconstruction for large data volume can be implemented by packing the subsets of projection data into the RGBA channels of GPU, performing the reconstruction chunk by chunk and combining the individual results in the end. The method is evaluated by reconstructing 3D images from computer-simulation data and real micro-CT data. Our results indicate that the GPU implementation can maintain original precision and speed up the reconstruction process by 110–120 times for circular cone-beam scan, as compared to traditional CPU implementation.

Vestibular schwannomas: Accuracy of tumor volume estimated by ice cream cone formula using thin-sliced MR images.

Science.gov (United States)

Ho, Hsing-Hao; Li, Ya-Hui; Lee, Jih-Chin; Wang, Chih-Wei; Yu, Yi-Lin; Hueng, Dueng-Yuan; Ma, Hsin-I; Hsu, Hsian-He; Juan, Chun-Jung

2018-01-01

We estimated the volume of vestibular schwannomas by an ice cream cone formula using thin-sliced magnetic resonance images (MRI) and compared the estimation accuracy among different estimating formulas and between different models. The study was approved by a local institutional review board. A total of 100 patients with vestibular schwannomas examined by MRI between January 2011 and November 2015 were enrolled retrospectively. Informed consent was waived. Volumes of vestibular schwannomas were estimated by cuboidal, ellipsoidal, and spherical formulas based on a one-component model, and cuboidal, ellipsoidal, Linskey's, and ice cream cone formulas based on a two-component model. The estimated volumes were compared to the volumes measured by planimetry. Intraobserver reproducibility and interobserver agreement was tested. Estimation error, including absolute percentage error (APE) and percentage error (PE), was calculated. Statistical analysis included intraclass correlation coefficient (ICC), linear regression analysis, one-way analysis of variance, and paired t-tests with P ice cream cone method, and ellipsoidal and Linskey's formulas significantly reduced the APE to 11.0%, 10.1%, and 12.5%, respectively (all P ice cream cone method and other two-component formulas including the ellipsoidal and Linskey's formulas allow for estimation of vestibular schwannoma volume more accurately than all one-component formulas.

Improved quantification for local regions of interest in preclinical PET imaging

Science.gov (United States)

Cal-González, J.; Moore, S. C.; Park, M.-A.; Herraiz, J. L.; Vaquero, J. J.; Desco, M.; Udias, J. M.

2015-09-01

In Positron Emission Tomography, there are several causes of quantitative inaccuracy, such as partial volume or spillover effects. The impact of these effects is greater when using radionuclides that have a large positron range, e.g. 68Ga and 124I, which have been increasingly used in the clinic. We have implemented and evaluated a local projection algorithm (LPA), originally evaluated for SPECT, to compensate for both partial-volume and spillover effects in PET. This method is based on the use of a high-resolution CT or MR image, co-registered with a PET image, which permits a high-resolution segmentation of a few tissues within a volume of interest (VOI) centered on a region within which tissue-activity values need to be estimated. The additional boundary information is used to obtain improved activity estimates for each tissue within the VOI, by solving a simple inversion problem. We implemented this algorithm for the preclinical Argus PET/CT scanner and assessed its performance using the radionuclides 18F, 68Ga and 124I. We also evaluated and compared the results obtained when it was applied during the iterative reconstruction, as well as after the reconstruction as a postprocessing procedure. In addition, we studied how LPA can help to reduce the ‘spillover contamination’, which causes inaccurate quantification of lesions in the immediate neighborhood of large, ‘hot’ sources. Quantification was significantly improved by using LPA, which provided more accurate ratios of lesion-to-background activity concentration for hot and cold regions. For 18F, the contrast was improved from 3.0 to 4.0 in hot lesions (when the true ratio was 4.0) and from 0.16 to 0.06 in cold lesions (true ratio  =  0.0), when using the LPA postprocessing. Furthermore, activity values estimated within the VOI using LPA during reconstruction were slightly more accurate than those obtained by post-processing, while also visually improving the image contrast and uniformity

In vitro assessment of artifacts induced by titanium, titanium-zirconium and zirconium dioxide implants in cone-beam computed tomography.

Science.gov (United States)

Sancho-Puchades, Manuel; Hämmerle, Christoph H F; Benic, Goran I

2015-10-01

The aim of this study was to test whether or not the intensity of artifacts around implants in cone-beam computed tomography (CBCT) differs between titanium, titanium-zirconium and zirconium dioxide implants. Twenty models of a human mandible, each containing one implant in the single-tooth gap position 45, were cast in dental stone. Five test models were produced for each of the following implant types: titanium 4.1 mm diameter (Ti4.1 ), titanium 3.3 mm diameter (Ti3.3 ), titanium-zirconium 3.3 mm diameter (TiZr3.3 ) and zirconium dioxide 3.5-4.5 mm diameter (ZrO3.5-4.5 ) implants. For control purposes, three models without implants were produced. Each model was scanned using a CBCT device. Gray values (GV) were recorded at eight circumferential positions around the implants at 0.5 mm, 1 mm and 2 mm from the implant surface (GVT est ). GV were assessed in the corresponding volumes of interest (VOI) in the control models without implants (GVC ontrol ). Differences of gray values (ΔGV) between GVT est and GVC ontrol were calculated as percentages. One-way ANOVA and post hoc tests were applied to detect differences between implant types. Mean ΔGV for ZrO3.5-4.5 presented the highest absolute values, generally followed by TiZr3.3 , Ti4.1 and Ti3.3 implants. The differences of ΔGV between ZrO3.5-4.5 and the remaining groups were statistically significant in the majority of the VOI (P ≤ 0.0167). ΔGV for TiZr3.3 , Ti4.1 and Ti3.3 implants did not differ significantly in the most VOI. For all implant types, ΔGV showed positive values buccally, mesio-buccally, lingually and disto-lingually, whereas negative values were detected mesially and distally. Zirconium dioxide implants generate significantly more artifacts as compared to titanium and titanium-zirconium implants. The intensity of artifacts around zirconium dioxide implants exhibited in average the threefold in comparison with titanium implants. © 2014 John Wiley & Sons A/S. Published by John Wiley

Motion compensation in extremity cone-beam CT using a penalized image sharpness criterion

Science.gov (United States)

Sisniega, A.; Stayman, J. W.; Yorkston, J.; Siewerdsen, J. H.; Zbijewski, W.

2017-05-01

Cone-beam CT (CBCT) for musculoskeletal imaging would benefit from a method to reduce the effects of involuntary patient motion. In particular, the continuing improvement in spatial resolution of CBCT may enable tasks such as quantitative assessment of bone microarchitecture (0.1 mm-0.2 mm detail size), where even subtle, sub-mm motion blur might be detrimental. We propose a purely image based motion compensation method that requires no fiducials, tracking hardware or prior images. A statistical optimization algorithm (CMA-ES) is used to estimate a motion trajectory that optimizes an objective function consisting of an image sharpness criterion augmented by a regularization term that encourages smooth motion trajectories. The objective function is evaluated using a volume of interest (VOI, e.g. a single bone and surrounding area) where the motion can be assumed to be rigid. More complex motions can be addressed by using multiple VOIs. Gradient variance was found to be a suitable sharpness metric for this application. The performance of the compensation algorithm was evaluated in simulated and experimental CBCT data, and in a clinical dataset. Motion-induced artifacts and blurring were significantly reduced across a broad range of motion amplitudes, from 0.5 mm to 10 mm. Structure similarity index (SSIM) against a static volume was used in the simulation studies to quantify the performance of the motion compensation. In studies with translational motion, the SSIM improved from 0.86 before compensation to 0.97 after compensation for 0.5 mm motion, from 0.8 to 0.94 for 2 mm motion and from 0.52 to 0.87 for 10 mm motion (~70% increase). Similar reduction of artifacts was observed in a benchtop experiment with controlled translational motion of an anthropomorphic hand phantom, where SSIM (against a reconstruction of a static phantom) improved from 0.3 to 0.8 for 10 mm motion. Application to a clinical dataset of a lower extremity showed dramatic reduction

Variability of silver fir (Abies alba Mill. cones – variability of cone parameters

Directory of Open Access Journals (Sweden)

Aniszewska Monika

2016-09-01

Full Text Available This study aimed at determining the shape of closed silver fir cones from the Jawor Forest District (Wroclaw, based purely on measurements of their length and thickness. Using these two parameters, the most accurate estimations were achieved with a fourth-degree polynomial fitting function. We then calculated the cones’ surface area and volume in three different ways: 1 Using the fourth-degree polynomial shape estimation, 2 Introducing indicators of compliance (k1, k2, k3 to calculate the volume and then comparing it to its actual value as measured in a pitcher filled with water, 3 Comparing the surface area of the cones as calculated with the polynomial function to the value obtained from ratios of indicators of compliance (ratios k4 and k5. We found that the calculated surface area and volume were substantially higher than the corresponding measured values. Test values of cone volume and surface area as calculated by our model were 8% and 5% lower, respectively, compared to direct measurements. We also determined the fir cones apparent density to be 0.8 g·cm-3on average. The gathered data on cone surface area, volume and bulk density is a valuable tool for optimizing the thermal peeling process in mill cabinets to acquire high quality seeds.

Cone-beam volume CT breast imaging: Feasibility study

International Nuclear Information System (INIS)

Chen Biao; Ning Ruola

2002-01-01

X-ray projection mammography, using a film/screen combination, or digital techniques, has proven to be the most effective imaging modality currently available for early detection of breast cancer. However, the inherent superimposition of structures makes a small carcinoma (a few millimeters in size) difficult to detect when it is occult or in dense breasts, leading to a high false-positive biopsy rate. Cone-beam x-ray-projection-based volume imaging using flat panel detectors (FPDs) may allow obtaining three-dimensional breast images, resulting in more accurate diagnosis of structures and patterns of lesions while eliminating the hard compression of breasts. This article presents a novel cone-beam volume computed tomographic breast imaging (CBVCTBI) technique based on the above techniques. Through a variety of computer simulations, the key issues of the system and imaging techniques were addressed, including the x-ray imaging geometry and corresponding reconstruction algorithms, x-ray characteristics of breast tissue and lesions, x-ray setting techniques, the absorbed dose estimation, and the quantitative effect of x-ray scattering on image quality. The preliminary simulation results support the proposed CVBCTBI modality for breast imaging in respect to its feasibility and practicability. The absorbed dose level is comparable to that of current mammography and will not be a prominent problem for this imaging technique. Compared to conventional mammography, the proposed imaging technique with isotropic spatial resolution will potentially provide significantly better low-contrast detectability of breast tumors and more accurate location of breast lesions

Fuzzy hidden Markov chains segmentation for volume determination and quantitation in PET

Energy Technology Data Exchange (ETDEWEB)

Hatt, M [INSERM U650, Laboratoire du Traitement de l' Information Medicale (LaTIM), CHU Morvan, Bat 2bis (I3S), 5 avenue Foch, Brest, 29609 (France); Lamare, F [INSERM U650, Laboratoire du Traitement de l' Information Medicale (LaTIM), CHU Morvan, Bat 2bis (I3S), 5 avenue Foch, Brest, 29609, (France); Boussion, N [INSERM U650, Laboratoire du Traitement de l' Information Medicale (LaTIM), CHU Morvan, Bat 2bis (I3S), 5 avenue Foch, Brest, 29609 (France); Turzo, A [INSERM U650, Laboratoire du Traitement de l' Information Medicale (LaTIM), CHU Morvan, Bat 2bis (I3S), 5 avenue Foch, Brest, 29609 (France); Collet, C [Ecole Nationale Superieure de Physique de Strasbourg (ENSPS), ULP, Strasbourg, F-67000 (France); Salzenstein, F [Institut d' Electronique du Solide et des Systemes (InESS), ULP, Strasbourg, F-67000 (France); Roux, C [INSERM U650, Laboratoire du Traitement de l' Information Medicale (LaTIM), CHU Morvan, Bat 2bis (I3S), 5 avenue Foch, Brest, 29609 (France); Jarritt, P [Medical Physics Agency, Royal Victoria Hospital, Belfast (United Kingdom); Carson, K [Medical Physics Agency, Royal Victoria Hospital, Belfast (United Kingdom); Rest, C Cheze-Le [INSERM U650, Laboratoire du Traitement de l' Information Medicale (LaTIM), CHU Morvan, Bat 2bis (I3S), 5 avenue Foch, Brest, 29609 (France); Visvikis, D [INSERM U650, Laboratoire du Traitement de l' Information Medicale (LaTIM), CHU Morvan, Bat 2bis (I3S), 5 avenue Foch, Brest, 29609 (France)

2007-07-21

Accurate volume of interest (VOI) estimation in PET is crucial in different oncology applications such as response to therapy evaluation and radiotherapy treatment planning. The objective of our study was to evaluate the performance of the proposed algorithm for automatic lesion volume delineation; namely the fuzzy hidden Markov chains (FHMC), with that of current state of the art in clinical practice threshold based techniques. As the classical hidden Markov chain (HMC) algorithm, FHMC takes into account noise, voxel intensity and spatial correlation, in order to classify a voxel as background or functional VOI. However the novelty of the fuzzy model consists of the inclusion of an estimation of imprecision, which should subsequently lead to a better modelling of the 'fuzzy' nature of the object of interest boundaries in emission tomography data. The performance of the algorithms has been assessed on both simulated and acquired datasets of the IEC phantom, covering a large range of spherical lesion sizes (from 10 to 37 mm), contrast ratios (4:1 and 8:1) and image noise levels. Both lesion activity recovery and VOI determination tasks were assessed in reconstructed images using two different voxel sizes (8 mm{sup 3} and 64 mm{sup 3}). In order to account for both the functional volume location and its size, the concept of % classification errors was introduced in the evaluation of volume segmentation using the simulated datasets. Results reveal that FHMC performs substantially better than the threshold based methodology for functional volume determination or activity concentration recovery considering a contrast ratio of 4:1 and lesion sizes of <28 mm. Furthermore differences between classification and volume estimation errors evaluated were smaller for the segmented volumes provided by the FHMC algorithm. Finally, the performance of the automatic algorithms was less susceptible to image noise levels in comparison to the threshold based techniques. The

High-quality 3D correction of ring and radiant artifacts in flat panel detector-based cone beam volume CT imaging

Science.gov (United States)

Abu Anas, Emran Mohammad; Kim, Jae Gon; Lee, Soo Yeol; Kamrul Hasan, Md

2011-10-01

The use of an x-ray flat panel detector is increasingly becoming popular in 3D cone beam volume CT machines. Due to the deficient semiconductor array manufacturing process, the cone beam projection data are often corrupted by different types of abnormalities, which cause severe ring and radiant artifacts in a cone beam reconstruction image, and as a result, the diagnostic image quality is degraded. In this paper, a novel technique is presented for the correction of error in the 2D cone beam projections due to abnormalities often observed in 2D x-ray flat panel detectors. Template images are derived from the responses of the detector pixels using their statistical properties and then an effective non-causal derivative-based detection algorithm in 2D space is presented for the detection of defective and mis-calibrated detector elements separately. An image inpainting-based 3D correction scheme is proposed for the estimation of responses of defective detector elements, and the responses of the mis-calibrated detector elements are corrected using the normalization technique. For real-time implementation, a simplification of the proposed off-line method is also suggested. Finally, the proposed algorithms are tested using different real cone beam volume CT images and the experimental results demonstrate that the proposed methods can effectively remove ring and radiant artifacts from cone beam volume CT images compared to other reported techniques in the literature.

High-quality 3D correction of ring and radiant artifacts in flat panel detector-based cone beam volume CT imaging

International Nuclear Information System (INIS)

Anas, Emran Mohammad Abu; Hasan, Md Kamrul; Kim, Jae Gon; Lee, Soo Yeol

2011-01-01

The use of an x-ray flat panel detector is increasingly becoming popular in 3D cone beam volume CT machines. Due to the deficient semiconductor array manufacturing process, the cone beam projection data are often corrupted by different types of abnormalities, which cause severe ring and radiant artifacts in a cone beam reconstruction image, and as a result, the diagnostic image quality is degraded. In this paper, a novel technique is presented for the correction of error in the 2D cone beam projections due to abnormalities often observed in 2D x-ray flat panel detectors. Template images are derived from the responses of the detector pixels using their statistical properties and then an effective non-causal derivative-based detection algorithm in 2D space is presented for the detection of defective and mis-calibrated detector elements separately. An image inpainting-based 3D correction scheme is proposed for the estimation of responses of defective detector elements, and the responses of the mis-calibrated detector elements are corrected using the normalization technique. For real-time implementation, a simplification of the proposed off-line method is also suggested. Finally, the proposed algorithms are tested using different real cone beam volume CT images and the experimental results demonstrate that the proposed methods can effectively remove ring and radiant artifacts from cone beam volume CT images compared to other reported techniques in the literature.

Filtered region of interest cone-beam rotational angiography

International Nuclear Information System (INIS)

Schafer, Sebastian; Noeel, Peter B.; Walczak, Alan M.; Hoffmann, Kenneth R.

2010-01-01

Purpose: Cone-beam rotational angiography (CBRA) is widely used in the modern clinical settings. In a number of procedures, the area of interest is often considerably smaller than the field of view (FOV) of the detector, subjecting the patient to potentially unnecessary x-ray dose. The authors therefore propose a filter-based method to reduce the dose in the regions of low interest, while supplying high image quality in the region of interest (ROI). Methods: For such procedures, the authors propose a method of filtered region of interest (FROI)-CBRA. In the authors' approach, a gadolinium filter with a circular central opening is placed into the x-ray beam during image acquisition. The central region is imaged with high contrast, while peripheral regions are subjected to a substantial lower intensity and dose through beam filtering. The resulting images contain a high contrast/intensity ROI, as well as a low contrast/intensity peripheral region, and a transition region in between. To equalize the two regions' intensities, the first projection of the acquisition is performed with and without the filter in place. The equalization relationship, based on Beer's law, is established through linear regression using corresponding filtered and nonfiltered data. The transition region is equalized based on radial profiles. Results: Evaluations in 2D and 3D show no visible difference between conventional FROI-CBRA projection images and reconstructions in the ROI. CNR evaluations show similar image quality in the ROI, with a reduced CNR in the reconstructed peripheral region. In all filtered projection images, the scatter fraction inside the ROI was reduced. Theoretical and experimental dose evaluations show a considerable dose reduction; using a ROI half the original FOV reduces the dose by 60% for the filter thickness of 1.29 mm. Conclusions: These results indicate the potential of FROI-CBRA to reduce the dose to the patient while supplying the physician with the desired

Filtered region of interest cone-beam rotational angiography

Energy Technology Data Exchange (ETDEWEB)

Schafer, Sebastian; Noeel, Peter B.; Walczak, Alan M.; Hoffmann, Kenneth R. [Department of Mechanical Engineering, SUNY at Buffalo, 3435 Main Street, Buffalo, New York 14214 (United States); Department of Neurosurgery, SUNY at Buffalo, 3435 Main Street, Buffalo, New York 14214 (United States) and Toshiba Stroke Research Center, SUNY at Buffalo, 3435 Main Street, Buffalo, New York 14214 (United States); Department of Neurosurgery, SUNY at Buffalo, 3435 Main Street, Buffalo, New York 14214 (United States); Department of Computer Science, SUNY at Buffalo, 3435 Main Street, Buffalo, New York 14214 (United States) and Toshiba Stroke Research Center, SUNY at Buffalo, 3435 Main Street, Buffalo, New York 14214 (United States); Department of Neurosurgery, SUNY at Buffalo, 3435 Main Street, Buffalo, New York 14214 and Toshiba Stroke Research Center, SUNY at Buffalo, 3435 Main Street, Buffalo, New York 14214 (United States); Department of Mechanical Engineering, SUNY at Buffalo, 3435 Main Street, Buffalo, New York 14214 (United States); Department of Neurosurgery, SUNY at Buffalo, 3435 Main Street, Buffalo, New York 14214 (United States); Department of Computer Science, SUNY at Buffalo, 3435 Main Street, Buffalo, New York 14214 (United States) and Toshiba Stroke Research Center, SUNY at Buffalo, 3435 Main Street, Buffalo, New York 14214 (United States)

2010-02-15

Purpose: Cone-beam rotational angiography (CBRA) is widely used in the modern clinical settings. In a number of procedures, the area of interest is often considerably smaller than the field of view (FOV) of the detector, subjecting the patient to potentially unnecessary x-ray dose. The authors therefore propose a filter-based method to reduce the dose in the regions of low interest, while supplying high image quality in the region of interest (ROI). Methods: For such procedures, the authors propose a method of filtered region of interest (FROI)-CBRA. In the authors' approach, a gadolinium filter with a circular central opening is placed into the x-ray beam during image acquisition. The central region is imaged with high contrast, while peripheral regions are subjected to a substantial lower intensity and dose through beam filtering. The resulting images contain a high contrast/intensity ROI, as well as a low contrast/intensity peripheral region, and a transition region in between. To equalize the two regions' intensities, the first projection of the acquisition is performed with and without the filter in place. The equalization relationship, based on Beer's law, is established through linear regression using corresponding filtered and nonfiltered data. The transition region is equalized based on radial profiles. Results: Evaluations in 2D and 3D show no visible difference between conventional FROI-CBRA projection images and reconstructions in the ROI. CNR evaluations show similar image quality in the ROI, with a reduced CNR in the reconstructed peripheral region. In all filtered projection images, the scatter fraction inside the ROI was reduced. Theoretical and experimental dose evaluations show a considerable dose reduction; using a ROI half the original FOV reduces the dose by 60% for the filter thickness of 1.29 mm. Conclusions: These results indicate the potential of FROI-CBRA to reduce the dose to the patient while supplying the physician with

Diagnostic performance of whole brain volume perfusion CT in intra-axial brain tumors: Preoperative classification accuracy and histopathologic correlation

International Nuclear Information System (INIS)

Xyda, Argyro; Haberland, Ulrike; Klotz, Ernst; Jung, Klaus; Bock, Hans Christoph; Schramm, Ramona; Knauth, Michael; Schramm, Peter

2012-01-01

Background: To evaluate the preoperative diagnostic power and classification accuracy of perfusion parameters derived from whole brain volume perfusion CT (VPCT) in patients with cerebral tumors. Methods: Sixty-three patients (31 male, 32 female; mean age 55.6 ± 13.9 years), with MRI findings suspected of cerebral lesions, underwent VPCT. Two readers independently evaluated VPCT data. Volumes of interest (VOIs) were marked circumscript around the tumor according to maximum intensity projection volumes, and then mapped automatically onto the cerebral blood volume (CBV), flow (CBF) and permeability Ktrans perfusion datasets. A second VOI was placed in the contra lateral cortex, as control. Correlations among perfusion values, tumor grade, cerebral hemisphere and VOIs were evaluated. Moreover, the diagnostic power of VPCT parameters, by means of positive and negative predictive value, was analyzed. Results: Our cohort included 32 high-grade gliomas WHO III/IV, 18 low-grade I/II, 6 primary cerebral lymphomas, 4 metastases and 3 tumor-like lesions. Ktrans demonstrated the highest sensitivity, specificity and positive predictive value, with a cut-off point of 2.21 mL/100 mL/min, for both the comparisons between high-grade versus low-grade and low-grade versus primary cerebral lymphomas. However, for the differentiation between high-grade and primary cerebral lymphomas, CBF and CBV proved to have 100% specificity and 100% positive predictive value, identifying preoperatively all the histopathologically proven high-grade gliomas. Conclusion: Volumetric perfusion data enable the hemodynamic assessment of the entire tumor extent and provide a method of preoperative differentiation among intra-axial cerebral tumors with promising diagnostic accuracy.

Exact finite volume expectation values of \\overline{Ψ}Ψ in the massive Thirring model from light-cone lattice correlators

Science.gov (United States)

Hegedűs, Árpád

2018-03-01

In this paper, using the light-cone lattice regularization, we compute the finite volume expectation values of the composite operator \\overline{Ψ}Ψ between pure fermion states in the Massive Thirring Model. In the light-cone regularized picture, this expectation value is related to 2-point functions of lattice spin operators being located at neighboring sites of the lattice. The operator \\overline{Ψ}Ψ is proportional to the trace of the stress-energy tensor. This is why the continuum finite volume expectation values can be computed also from the set of non-linear integral equations (NLIE) governing the finite volume spectrum of the theory. Our results for the expectation values coming from the computation of lattice correlators agree with those of the NLIE computations. Previous conjectures for the LeClair-Mussardo-type series representation of the expectation values are also checked.

Basal ganglia volumes in drug-naive first-episode schizophrenia patients before and after short-term treatment with either a typical or an atypical antipsychotic drug

DEFF Research Database (Denmark)

Glenthoj, Andreas; Glenthøj, Birte Yding; Mackeprang, Torben

2007-01-01

or intracranial volume, the only significant difference between patients and controls was a Hemisphere x Group interaction for the caudate nucleus at baseline, with controls having larger left than right caudate nuclei and patients having marginally larger right than left caudate volumes. Within patients, the two...... of exposure to medication and in controls at baseline. Caudate nucleus, nucleus accumbens, and putamen volumes were measured. Compared with controls, absolute volumes of interest (VOIs) were smaller in patients at baseline and increased after treatment. However, with controls for age, gender and whole brain...

Basal ganglia volumes in drug-naive first-episode schizophrenia patients before and after short-term treatment with either a typical or an atypical antipsychotic drug

DEFF Research Database (Denmark)

Glenthoj, Andreas; Glenthoj, Birte Y; Mackeprang, Torben

2007-01-01

of exposure to medication and in controls at baseline. Caudate nucleus, nucleus accumbens, and putamen volumes were measured. Compared with controls, absolute volumes of interest (VOIs) were smaller in patients at baseline and increased after treatment. However, with controls for age, gender and whole brain...... or intracranial volume, the only significant difference between patients and controls was a Hemisphere x Group interaction for the caudate nucleus at baseline, with controls having larger left than right caudate nuclei and patients having marginally larger right than left caudate volumes. Within patients, the two...

Region-of-interest reconstruction for a cone-beam dental CT with a circular trajectory

International Nuclear Information System (INIS)

Hu, Zhanli; Zou, Jing; Gui, Jianbao; Zheng, Hairong; Xia, Dan

2013-01-01

Dental CT is the most appropriate and accurate device for preoperative evaluation of dental implantation. It can demonstrate the quantity of bone in three dimensions (3D), the location of important adjacent anatomic structures and the quality of available bone with minimal geometric distortion. Nevertheless, with the rapid increase of dental CT examinations, we are facing the problem of dose reduction without loss of image quality. In this work, backprojection-filtration (BPF) and Feldkamp–Davis–Kress (FDK) algorithm was applied to reconstruct the 3D full image and region-of-interest (ROI) image from complete and truncated circular cone-beam data respectively by computer-simulation. In addition, the BPF algorithm was evaluated based on the 3D ROI-image reconstruction from real data, which was acquired from our developed circular cone-beam prototype dental CT system. The results demonstrated that the ROI-image quality reconstructed from truncated data using the BPF algorithm was comparable to that reconstructed from complete data. The FDK algorithm, however, created artifacts while reconstructing ROI-image. Thus it can be seen, for circular cone-beam dental CT, reducing scanning angular range of the BPF algorithm used for ROI-image reconstruction are helpful for reducing the radiation dose and scanning time. Finally, an analytical method was developed for estimation of the ROI projection area on the detector before CT scanning, which would help doctors to roughly estimate the total radiation dose before the CT examination. -- Highlights: ► BPF algorithm was applied by using dental CT for the first time. ► A method was developed for estimation of projection region before CT scanning. ► Roughly predict the total radiation dose before CT scans. ► Potential reduce imaging radiation dose, scatter, and scanning time

Cross-cultural adaptation of the Chilean version of the Voice Symptom Scale - VoiSS.

Science.gov (United States)

Ruston, Francisco Contreras; Moreti, Felipe; Vivero, Martín; Malebran, Celina; Behlau, Mara

This research aims to accomplish the cross-cultural equivalence of the Chilean version of the VoiSS protocol through its cultural and linguistic adaptation. After the translation of the VoiSS protocol to Chilean Spanish by two bilingual speech therapists and its back translation to English, we compared the items of the original tool with the previous translated version. The existing discrepancies were modified by a consensus committee of five speech therapists and the translated version was entitled Escala de Sintomas Vocales - ESV, with 30 questions and five answers: "Never", "Occasionally", "Sometimes", "Most of the time", "Always". For cross-cultural equivalence, the protocol was applied to 15 individuals with vocal problems. In each question the option of "Not applicable" was added to the answer choices for identification of the questions not comprehended or not appropriate for the target population. Two individuals had difficulty answering two questions, which made it necessary to adapt the translation of only one of them. The modified ESV was applied to three individuals with vocal problems, and there were incomprehensible inappropriate questions for the Chilean culture. The ESV reflects the original English version, both in the number of questions and the limitations of the emotional and physical domains. There is now a cross-cultural equivalence of VoiSS in Chilean Spanish, titled ESV. The validation of the ESV for Chilean Spanish is ongoing. RESUMEN Este estudio tuvo como objetivo realizar la equivalencia cultural de la versión Chilena del protocolo Voice Symptom Scale - VoiSS por medio de su adaptación cultural y lingüística. Después de la traducción del VoiSS para el Español Chileno, por dos fonoaudiólogos bilingües, y de la retro traducción para el inglés, se realizó una comparación de los ítems del instrumento original con la versión traducida, surgiendo discrepancias; tales divergencias fueron resueltas por un comité compuesto por

Pancreas segmentation from 3D abdominal CT images using patient-specific weighted subspatial probabilistic atlases

Science.gov (United States)

Karasawa, Kenichi; Oda, Masahiro; Hayashi, Yuichiro; Nimura, Yukitaka; Kitasaka, Takayuki; Misawa, Kazunari; Fujiwara, Michitaka; Rueckert, Daniel; Mori, Kensaku

2015-03-01

Abdominal organ segmentations from CT volumes are now widely used in the computer-aided diagnosis and surgery assistance systems. Among abdominal organs, the pancreas is especially difficult to segment because of its large individual differences of the shape and position. In this paper, we propose a new pancreas segmentation method from 3D abdominal CT volumes using patient-specific weighted-subspatial probabilistic atlases. First of all, we perform normalization of organ shapes in training volumes and an input volume. We extract the Volume Of Interest (VOI) of the pancreas from the training volumes and an input volume. We divide each training VOI and input VOI into some cubic regions. We use a nonrigid registration method to register these cubic regions of the training VOI to corresponding regions of the input VOI. Based on the registration results, we calculate similarities between each cubic region of the training VOI and corresponding region of the input VOI. We select cubic regions of training volumes having the top N similarities in each cubic region. We subspatially construct probabilistic atlases weighted by the similarities in each cubic region. After integrating these probabilistic atlases in cubic regions into one, we perform a rough-to-precise segmentation of the pancreas using the atlas. The results of the experiments showed that utilization of the training volumes having the top N similarities in each cubic region led good results of the pancreas segmentation. The Jaccard Index and the average surface distance of the result were 58.9% and 2.04mm on average, respectively.

Fundamentals of cone beam computed tomography for a prosthodontist

Directory of Open Access Journals (Sweden)

George Puthenpurayil John

2015-01-01

Full Text Available Cone beam computed tomography (CBCT, also referred to as C-arm computed tomography [CT], cone beam volume CT, or flat panel CT is a medical imaging technique of X-ray CT where the X-rays are divergent, forming a cone. [1] CBCT systems have been designed for imaging hard tissues of the maxillofacial region. CBCT is capable of providing sub-millimeter resolution in images of high diagnostic quality, with short scanning times (10-70 s and radiation dosages reportedly up to 15-100 times lower than those of conventional CT scans. Increasing availability of this technology provides the dental clinician with an imaging modality capable of providing a three-dimensional representation of the maxillofacial skeleton with minimal distortion. The aim of this article is to sensitize the Prosthodontist to CBCT technology, provide an overview of currently available maxillofacial CBCT systems and review the specific application of various CBCT display modes to clinical Prosthodontic practice. A MEDLINE search for relevant articles in this specific area of interest was conducted. The selected articles were critically reviewed and the data acquired were systematically compiled.

Fundamentals of cone beam computed tomography for a prosthodontist

Science.gov (United States)

John, George Puthenpurayil; Joy, Tatu Elenjickal; Mathew, Justin; Kumar, Vinod R. B.

2015-01-01

Cone beam computed tomography (CBCT, also referred to as C-arm computed tomography [CT], cone beam volume CT, or flat panel CT) is a medical imaging technique of X-ray CT where the X-rays are divergent, forming a cone.[1] CBCT systems have been designed for imaging hard tissues of the maxillofacial region. CBCT is capable of providing sub-millimeter resolution in images of high diagnostic quality, with short scanning times (10–70 s) and radiation dosages reportedly up to 15–100 times lower than those of conventional CT scans. Increasing availability of this technology provides the dental clinician with an imaging modality capable of providing a three-dimensional representation of the maxillofacial skeleton with minimal distortion. The aim of this article is to sensitize the Prosthodontist to CBCT technology, provide an overview of currently available maxillofacial CBCT systems and review the specific application of various CBCT display modes to clinical Prosthodontic practice. A MEDLINE search for relevant articles in this specific area of interest was conducted. The selected articles were critically reviewed and the data acquired were systematically compiled. PMID:26929479

Volume-of-change cone-beam CT for image-guided surgery

International Nuclear Information System (INIS)

Lee, Junghoon; Stayman, J Webster; Otake, Yoshito; Schafer, Sebastian; Zbijewski, Wojciech; Khanna, A Jay; Siewerdsen, Jeffrey H; Prince, Jerry L

2012-01-01

C-arm cone-beam CT (CBCT) can provide intraoperative 3D imaging capability for surgical guidance, but workflow and radiation dose are the significant barriers to broad utilization. One main reason is that each 3D image acquisition requires a complete scan with a full radiation dose to present a completely new 3D image every time. In this paper, we propose to utilize patient-specific CT or CBCT as prior knowledge to accurately reconstruct the aspects of the region that have changed by the surgical procedure from only a sparse set of x-rays. The proposed methods consist of a 3D–2D registration between the prior volume and a sparse set of intraoperative x-rays, creating digitally reconstructed radiographs (DRRs) from the registered prior volume, computing difference images by subtracting DRRs from the intraoperative x-rays, a penalized likelihood reconstruction of the volume of change (VOC) from the difference images, and finally a fusion of VOC reconstruction with the prior volume to visualize the entire surgical field. When the surgical changes are local and relatively small, the VOC reconstruction involves only a small volume size and a small number of projections, allowing less computation and lower radiation dose than is needed to reconstruct the entire surgical field. We applied this approach to sacroplasty phantom data obtained from a CBCT test bench and vertebroplasty data with a fresh cadaver acquired from a C-arm CBCT system with a flat-panel detector. The VOCs were reconstructed from a varying number of images (10–66 images) and compared to the CBCT ground truth using four different metrics (mean squared error, correlation coefficient, structural similarity index and perceptual difference model). The results show promising reconstruction quality with structural similarity to the ground truth close to 1 even when only 15–20 images were used, allowing dose reduction by the factor of 10–20. (paper)

Effects of computing parameters and measurement locations on the estimation of 3D NPS in non-stationary MDCT images.

Science.gov (United States)

Miéville, Frédéric A; Bolard, Gregory; Bulling, Shelley; Gudinchet, François; Bochud, François O; Verdun, François R

2013-11-01

The goal of this study was to investigate the impact of computing parameters and the location of volumes of interest (VOI) on the calculation of 3D noise power spectrum (NPS) in order to determine an optimal set of computing parameters and propose a robust method for evaluating the noise properties of imaging systems. Noise stationarity in noise volumes acquired with a water phantom on a 128-MDCT and a 320-MDCT scanner were analyzed in the spatial domain in order to define locally stationary VOIs. The influence of the computing parameters in the 3D NPS measurement: the sampling distances bx,y,z and the VOI lengths Lx,y,z, the number of VOIs NVOI and the structured noise were investigated to minimize measurement errors. The effect of the VOI locations on the NPS was also investigated. Results showed that the noise (standard deviation) varies more in the r-direction (phantom radius) than z-direction plane. A 25 × 25 × 40 mm(3) VOI associated with DFOV = 200 mm (Lx,y,z = 64, bx,y = 0.391 mm with 512 × 512 matrix) and a first-order detrending method to reduce structured noise led to an accurate NPS estimation. NPS estimated from off centered small VOIs had a directional dependency contrary to NPS obtained from large VOIs located in the center of the volume or from small VOIs located on a concentric circle. This showed that the VOI size and location play a major role in the determination of NPS when images are not stationary. This study emphasizes the need for consistent measurement methods to assess and compare image quality in CT. Copyright © 2012 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

A template-based procedure for determining white matter integrity in the internal capsule early after stroke

Directory of Open Access Journals (Sweden)

Matthew A. Petoe

2014-01-01

Full Text Available The integrity of descending white matter pathways, measured by fractional anisotropy from DW-MRI, is a key prognostic indicator of motor recovery after stroke. Barriers to translation of fractional anisotropy measures into routine clinical practice include the time required for manually delineating volumes of interest (VOIs, and inter-examiner variability in this process. This study investigated whether registering and then editing template volumes of interest ‘as required’ would improve inter-examiner reliability compared with manual delineation, without compromising validity. MRI was performed with 30 sub-acute stroke patients with motor deficits (mean NIHSS = 11, range 0–17. Four independent examiners manually delineated VOIs for the posterior limbs of the internal capsules on T1 images, or edited template VOIs that had been registered to the T1 images if they encroached on ventricles or basal ganglia. Fractional anisotropy within each VOI and interhemispheric asymmetry were then calculated. We found that 13/30 registered template VOIs required editing. Edited template VOIs were more spatially similar between examiners than the manually delineated VOIs (p = 0.005. Both methods produced similar asymmetry values that correlated with clinical scores with near perfect levels of agreement between examiners. Contralesional fractional anisotropy correlated with age when edited template VOIs were used but not when VOIs were manually delineated. Editing template VOIs as required is reliable, increases the validity of fractional anisotropy measurements in the posterior limb of the internal capsule, and is less time-consuming compared to manual delineation. This approach could support the use of FA asymmetry measures in routine clinical practice.

Natural gas markets integration in the Southern Cone: analysis of interests and stakeholders; Perspectivas para a integracao gasifera no Cone Sul: uma analise dos principais interesses e interessados

Energy Technology Data Exchange (ETDEWEB)

Villas Boas, Marina Vieira [PETROBRAS, Rio de Janeiro, RJ (Brazil)

2004-07-01

Natural gas has been recently gaining importance in the world energy mix especially because of its economical and environmental advantages but also because of technological and geopolitical issues. In the Southern Cone, natural gas demand shall maintain its upward trend in the next years mainly due to its use in power generation. This region owns significant natural gas reserves and, at the same time, a growing and with high potential market. In this scenario, natural gas markets integration is seen simultaneously as an opportunity and a necessity as it can contribute to demand and production interconnection, price competitiveness and security of supply. Nevertheless, there are important barriers to the consolidation of natural gas market integration in the Southern Cone region that have to be overcome. For the natural gas markets integration to be a sustainable project it is necessary to identify the major stakeholders and their interests and pursue a balance between them. (author)

Light-cone observables and gauge-invariance in the geodesic light-cone formalism

Energy Technology Data Exchange (ETDEWEB)

Scaccabarozzi, Fulvio; Yoo, Jaiyul, E-mail: fulvio@physik.uzh.ch, E-mail: jyoo@physik.uzh.ch [Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zürich, Winterthurerstrasse 190, CH-8057, Zürich (Switzerland)

2017-06-01

The remarkable properties of the geodesic light-cone (GLC) coordinates allow analytic expressions for the light-cone observables, providing a new non-perturbative way for calculating the effects of inhomogeneities in our Universe. However, the gauge-invariance of these expressions in the GLC formalism has not been shown explicitly. Here we provide this missing part of the GLC formalism by proving the gauge-invariance of the GLC expressions for the light-cone observables, such as the observed redshift, the luminosity distance, and the physical area and volume of the observed sources. Our study provides a new insight on the properties of the GLC coordinates and it complements the previous work by the GLC collaboration, leading to a comprehensive description of light propagation in the GLC representation.

Proceedings of the nuclear and particle physics on the light cone workshop

International Nuclear Information System (INIS)

Johnson, M.B.; Kisslinger, L.

1988-01-01

This book deals with phenomena in nuclear and particle physics that occur at high energy and at high momentum transfer. At high energy, particles move near the light cone, and the topics covered deal with the physics from this perspective. The light-cone description is familiar in particle physics, but until recently it has not been used in nuclear physics. In view of the fact that nuclear physicists are increasingly looking to questions that can be answered only by experiments in the range of energy where the light-cone description seems to be of advantage, and that the ideas involved are new to many people in the nuclear physics community, efforts were made to ensure that each main speaker would give an introduction to the subject as well as present recent developments. The book should, therefore, be valuable to those who want to learn about light-cone approaches, in particular experimentalists and students, as well as to specialists. The volume is divided into eight chapters. The first chapter is an overview of the meeting and an introduction to the subject of light-cone physics. The remaining chapters encompass various applications and current topics in nuclear and particle physics where use of light-cone methods leads to understanding of high-energy phenomena and their connection to the quark and mesonic substructure of the nucleus. These include the main talks containing the introductory material, as well as shorter papers on the more specialized topics of current interest in both experimental and theoretical aspects of the subject. 38 papers have been cataloged separately

Advanced MRI assessment to predict benefit of anti-programmed cell death 1 protein immunotherapy response in patients with recurrent glioblastoma

Energy Technology Data Exchange (ETDEWEB)

Qin, Lei [Dana-Farber Cancer Institute, Department of Imaging, Boston, MA (United States); Harvard Medical School, Department of Radiology, Boston, MA (United States); Li, Xiang; Qu, Jinrong [Affiliated Cancer Hospital of Zhengzhou University, Department of Radiology, Zhengzhou, Henan (China); Brigham and Women' s Hospital, Department of Radiology, Boston, MA (United States); Stroiney, Amanda [Dana-Farber Cancer Institute, Department of Imaging, Boston, MA (United States); Northeastern University, Department of Behavioral Neuroscience, College of Sciences, Boston, MA (United States); Helgager, Jeffrey [Brigham and Women' s Hospital, Department of Pathology, Boston, MA (United States); Reardon, David A. [Dana-Farber Cancer Institute, CenterforNeuro-Oncology, Boston, MA (United States); Department of Medicine, Boston, MA (United States); Young, Geoffrey S. [Harvard Medical School, Department of Radiology, Boston, MA (United States); Brigham and Women' s Hospital, Department of Radiology, Boston, MA (United States)

2017-02-15

We describe the imaging findings encountered in GBM patients receiving immune checkpoint blockade and assess the potential of quantitative MRI biomarkers to differentiate patients who derive therapeutic benefit from those who do not. A retrospective analysis was performed on longitudinal MRIs obtained on recurrent GBM patients enrolled on clinical trials. Among 10 patients with analyzable data, bidirectional diameters were measured on contrast enhanced T1 (pGd-T1WI) and volumes of interest (VOI) representing measurable abnormality suggestive of tumor were selected on pGdT1WI (pGdT1 VOI), FLAIR-T2WI (FLAIR VOI), and ADC maps. Intermediate ADC (IADC) VOI represented voxels within the FLAIR VOI having ADC in the range of highly cellular tumor (0.7-1.1 x 10{sup -3} mm{sup 2}/s) (IADC VOI). Therapeutic benefit was determined by tissue pathology and survival on trial. IADC VOI, pGdT1 VOI, FLAIR VOI, and RANO assessment results were correlated with patient benefit. Five patients were deemed to have received therapeutic benefit and the other five patients did not. The average time on trial for the benefit group was 194 days, as compared to 81 days for the no benefit group. IADC VOI correlated well with the presence or absence of clinical benefit in 10 patients. Furthermore, pGd VOI, FLAIR VOI, and RANO assessment correlated less well with response. MRI reveals an initial increase in volumes of abnormal tissue with contrast enhancement, edema, and intermediate ADC suggesting hypercellularity within the first 0-6 months of immunotherapy. Subsequent stabilization and improvement in IADC VOI appear to better predict ultimate therapeutic benefit from these agents than conventional imaging. (orig.)

Exact cone beam CT with a spiral scan

International Nuclear Information System (INIS)

Tam, K.C.; Samarasekera, S.; Sauer, F.

1998-01-01

A method is developed which makes it possible to scan and reconstruct an object with cone beam x-rays in a spiral scan path with area detectors much shorter than the length of the object. The method is mathematically exact. If only a region of interest of the object is to be imaged, a top circle scan at the top level of the region of interest and a bottom circle scan at the bottom level of the region of interest are added. The height of the detector is required to cover only the distance between adjacent turns in the spiral projected at the detector. To reconstruct the object, the Radon transform for each plane intersecting the object is computed from the totality of the cone beam data. This is achieved by suitably combining the cone beam data taken at different source positions on the scan path; the angular range of the cone beam data required at each source position can be determined easily with a mask which is the spiral scan path projected on the detector from the current source position. The spiral scan algorithm has been successfully validated with simulated cone beam data. (author)

Under which conditions, additional monitoring data are worth gathering for improving decision making? Application of the VOI theory in the Bayesian Event Tree eruption forecasting framework

Science.gov (United States)

Loschetter, Annick; Rohmer, Jérémy

2016-04-01

. For the parameters that concern expert setting, the weight attributed to monitoring measurement ω, the mean of thresholds, the economic context and the setting of the decision threshold are very influential. The interest of applying the VOI theory (more precisely the value of imperfect information) in the BET framework was demonstrated as support for helping experts in the setting of the monitoring system or for helping managers to decide the installation of additional monitoring systems. Acknowledgments: This work was carried out in the framework of the project MEDSUV. This project is funded under the call FP7 ENV.2012.6.4-2: Long-term monitoring experiment in geologically active regions of Europe prone to natural hazards: the Supersite concept. Grant agreement n°308665.

The NLO jet vertex in the small-cone approximation for kt and cone algorithms

International Nuclear Information System (INIS)

Colferai, D.; Niccoli, A.

2015-01-01

We determine the jet vertex for Mueller-Navelet jets and forward jets in the small-cone approximation for two particular choices of jet algoritms: the kt algorithm and the cone algorithm. These choices are motivated by the extensive use of such algorithms in the phenomenology of jets. The differences with the original calculations of the small-cone jet vertex by Ivanov and Papa, which is found to be equivalent to a formerly algorithm proposed by Furman, are shown at both analytic and numerical level, and turn out to be sizeable. A detailed numerical study of the error introduced by the small-cone approximation is also presented, for various observables of phenomenological interest. For values of the jet “radius” R=0.5, the use of the small-cone approximation amounts to an error of about 5% at the level of cross section, while it reduces to less than 2% for ratios of distributions such as those involved in the measure of the azimuthal decorrelation of dijets.

The NLO jet vertex in the small-cone approximation for kt and cone algorithms

Energy Technology Data Exchange (ETDEWEB)

Colferai, D.; Niccoli, A. [Dipartimento di Fisica e Astronomia, Università di Firenze and INFN, Sezione di Firenze, 50019 Sesto Fiorentino (Italy)

2015-04-15

We determine the jet vertex for Mueller-Navelet jets and forward jets in the small-cone approximation for two particular choices of jet algoritms: the kt algorithm and the cone algorithm. These choices are motivated by the extensive use of such algorithms in the phenomenology of jets. The differences with the original calculations of the small-cone jet vertex by Ivanov and Papa, which is found to be equivalent to a formerly algorithm proposed by Furman, are shown at both analytic and numerical level, and turn out to be sizeable. A detailed numerical study of the error introduced by the small-cone approximation is also presented, for various observables of phenomenological interest. For values of the jet “radius” R=0.5, the use of the small-cone approximation amounts to an error of about 5% at the level of cross section, while it reduces to less than 2% for ratios of distributions such as those involved in the measure of the azimuthal decorrelation of dijets.

Kinetic parameter estimation from SPECT cone-beam projection measurements

International Nuclear Information System (INIS)

Huesman, Ronald H.; Reutter, Bryan W.; Zeng, G. Larry; Gullberg, Grant T.

1998-01-01

Kinetic parameters are commonly estimated from dynamically acquired nuclear medicine data by first reconstructing a dynamic sequence of images and subsequently fitting the parameters to time-activity curves generated from regions of interest overlaid upon the image sequence. Biased estimates can result from images reconstructed using inconsistent projections of a time-varying distribution of radiopharmaceutical acquired by a rotating SPECT system. If the SPECT data are acquired using cone-beam collimators wherein the gantry rotates so that the focal point of the collimators always remains in a plane, additional biases can arise from images reconstructed using insufficient, as well as truncated, projection samples. To overcome these problems we have investigated the estimation of kinetic parameters directly from SPECT cone-beam projection data by modelling the data acquisition process. To accomplish this it was necessary to parametrize the spatial and temporal distribution of the radiopharmaceutical within the SPECT field of view. In a simulated chest image volume, kinetic parameters were estimated for simple one-compartment models for four myocardial regions of interest. Myocardial uptake and washout parameters estimated by conventional analysis of noiseless simulated cone-beam data had biases ranging between 3-26% and 0-28%, respectively. Parameters estimated directly from the noiseless projection data were unbiased as expected, since the model used for fitting was faithful to the simulation. Statistical uncertainties of parameter estimates for 10 000 000 events ranged between 0.2-9% for the uptake parameters and between 0.3-6% for the washout parameters. (author)

Cones for dental radiography

Energy Technology Data Exchange (ETDEWEB)

Butler, M J [National Radiological Protection Board, Harwell (UK)

1977-04-01

Dental radiographic techniques are summarized. The advantages and disadvantages of the use of both the conventional plastic pointer cone and the open-ended cylinders or divergent cones favoured both by the ICRP (Protection against Ionizing Radiation from External Sources, Oxford, Pergamon Press, 1973, ICRP Publication 15), and in the Code of Practice for the Protection of Persons against Ionizing Radiation arising from Medical and Dental Use (1972, 3rd edition, London, HMSO) are discussed. The use of the word 'should' in these recommendations to signify a desirable requirement, not an essential one, is noted. This wording is currently of interest both nationally and internationally in relation to regulations, standards and notes for guidance. The National Radiological Protection Board (NRPB) has been reviewing the position, and has concluded that open-ended cones have disadvantages which may sometimes outweigh their advantages. Although open-ended cones are preferable under some circumstances, the recommendation that they should be used ought not to be followed without an understanding of the issues involved. The hazards associated with the use of interchangeable cones are considered. The NRPB now proposes that the requirement for the replacement of pointer cones (for both new and existing equipment) should be withdrawn.

Estimating study costs for use in VOI, a study of dutch publicly funded drug related research

NARCIS (Netherlands)

Van Asselt, A.D.; Ramaekers, B.L.; Corro Ramos, I.; Joore, M.A.; Al, M.J.; Lesman-Leegte, I.; Postma, M.J.; Vemer, P.; Feenstra, T.F.

2016-01-01

Objectives: To perform value of information (VOI) analyses, an estimate of research costs is needed. However, reference values for such costs are not available. This study aimed to analyze empirical data on research budgets and, by means of a cost tool, provide an overview of costs of several types

Histogram analysis reveals a better delineation of tumor volume from background in 18F-FET PET compared to CBV maps in a hybrid PET–MR studie in gliomas

International Nuclear Information System (INIS)

Filss, Christian P.; Stoffels, Gabriele; Galldiks, Norbert; Sabel, Michael; Wittsack, Hans J.; Coenen, Heinz H.; Shah, Nadim J.; Herzog, Hans

2014-01-01

Anatomical imaging with magnetic resonance imaging (MRI) is currently the method of first choice for diagnostic investigation of glial tumors. However, different MR sequences may over- or underestimate tumor size and thus it may not be possible to delineate tumor from adjacent brain. In order to compensate this confinement additonal MR sequences like perfusion weighted MRI (PWI) with regional cerebral blood volume (rCBV) or positron emission tomography (PET) with aminoacids are used to gain further information. Recent studies suggest that both of theses image modalities provide similar diagnostic information. For comparison tumor to brain ratios (TBR) with mean and maximum values are frequently used but results from different studies can often not be checked against each other. Furthermore, especially the maximum TBR in rCBV is at risk to be falsified by artifacts (e.g. blood vessels). These confinements are reduced by the use of histograms since all information of the VOIs are equally displayed. In this study we measured and compared the intersection of tumor and reference tissue histograms in 18 F-FET PET and rCBV maps in glioma patients. Methods: Twenty-seven glioma patients with contrast enhancing lesion on T1-weighted MR images were investigated using static 18 F-FET PET and rCBV in MRI using a PET–MR hybrid scanner. In all patients diagnosis was confirmed histologically (7 grade II gliomas, 6 grade III gliomas and 14 grade IV gliomas). We generated a set of tumor and reference tissue Volumes-of-Interest (VOIs) based on T1 weighted images in MRI with the tumor VOI defined by contrast enhancement and transferred these VOIs to the corresponding 18 F-FET PET scans and rCBV maps. From these VOIs we generated tumor and reference tissue histograms with a unity of one for each curve integral and measured the proportion of the area under the tumor curve that falls into the reference curve for 18 F-FET PET and rCBV maps for each patient. Results: The mean proportion

Cone-Beam CT Localization of Internal Target Volumes for Stereotactic Body Radiotherapy of Lung Lesions

International Nuclear Information System (INIS)

Wang Zhiheng; Wu, Q. Jackie; Marks, Lawrence B.; Larrier, Nicole; Yin Fangfang

2007-01-01

Purpose: In this study, we investigate a technique of matching internal target volumes (ITVs) in four-dimensional (4D) simulation computed tomography (CT) to the composite target volume in free-breathing on-board cone-beam (CB) CT. The technique is illustrated by using both phantom and patient cases. Methods and Materials: A dynamic phantom with a target ball simulating respiratory motion with various amplitude and cycle times was used to verify localization accuracy. The dynamic phantom was scanned using simulation CT with a phase-based retrospective sorting technique. The ITV was then determined based on 10 sets of sorted images. The size and epicenter of the ITV identified from 4D simulation CT images and the composite target volume identified from on-board CBCT images were compared to assess localization accuracy. Similarly, for two clinical cases of patients with lung cancer, ITVs defined from 4D simulation CT images and CBCT images were compared. Results: For the phantom, localization accuracy between the ITV in 4D simulation CT and the composite target volume in CBCT was within 1 mm, and ITV was within 8.7%. For patient cases, ITVs on simulation CT and CBCT were within 8.0%. Conclusion: This study shows that CBCT is a useful tool to localize ITV for targets affected by respiratory motion. Verification of the ITV from 4D simulation CT using on-board free-breathing CBCT is feasible for the target localization of lung tumors

Sedimentology, eruptive mechanism and facies architecture of basaltic scoria cones from the Auckland Volcanic Field (New Zealand)

Science.gov (United States)

Kereszturi, Gábor; Németh, Károly

2016-09-01

Scoria cones are a common type of basaltic to andesitic small-volume volcanoes (e.g. 10- 1-10- 5 km3) that results from gas-bubble driven explosive eruptive styles. Although they are small in volume, they can produce complex eruptions, involving multiple eruptive styles. Eight scoria cones from the Quaternary Auckland Volcanic Field in New Zealand were selected to define the eruptive style variability from their volcanic facies architecture. The reconstruction of their eruptive and pyroclastic transport mechanisms was established on the basis of study of their volcanic sedimentology, stratigraphy, and measurement of their pyroclast density, porosity, Scanning Electron Microscopy, 2D particle morphology analysis and Visible and Near Visible Infrared Spectroscopy. Collection of these data allowed defining three end-member types of scoria cones inferred to be constructed from lava-fountaining, transitional fountaining and Strombolian type, and explosive Strombolian type. Using the physical and field-based characteristics of scoriaceous samples a simple generalised facies model of basaltic scoria cones for the AVF is developed that can be extended to other scoria cones elsewhere. The typical AVF scoria cone has an initial phreatomagmatic phases that might reduce the volume of magma available for subsequent scoria cone forming eruptions. This inferred to have the main reason to have decreased cone volumes recognised from Auckland in comparison to other volcanic fields evolved dominantly in dry eruptive condition (e.g. no external water influence). It suggests that such subtle eruptive style variations through a scoria cone evolution need to be integrated into the hazard assessment of a potentially active volcanic field such as that in Auckland.

Some Extensions of Banach's Contraction Principle in Complete Cone Metric Spaces

Directory of Open Access Journals (Sweden)

Raja P

2008-01-01

Full Text Available Abstract In this paper we consider complete cone metric spaces. We generalize some definitions such as -nonexpansive and -uniformly locally contractive functions -closure, -isometric in cone metric spaces, and certain fixed point theorems will be proved in those spaces. Among other results, we prove some interesting applications for the fixed point theorems in cone metric spaces.

Does hyrax expansion therapy affect maxillary sinus volume? A cone-beam computed tomography report

International Nuclear Information System (INIS)

Darsey, Drew M.; English, Jeryl D.; Ellis, Randy K.; Akyalcin, Sercan; Kau, Chung H

2012-01-01

The aim of this study was to investigate the initial effects of maxillary expansion therapy with Hyrax appliance and to evaluate the related changes in maxillary sinus volume. Thirty patients (20 females, 10 males; 13.8 years) requiring maxillary expansion therapy, as part of their comprehensive orthodontic treatment, were examined. Each patient had cone-beam computed tomography (CBCT) images taken before (T1) and after (T2) maxillary expansion therapy with a banded Hyrax appliance. Multiplanar slices were used to measure linear dimensions and palatal vault angle. Volumetric analysis was used to measure maxillary sinus volumes. Student t tests were used to compare the pre- and post-treatment measurements. Additionally, differences between two age groups were compared with Mann-Whitney U test. The level of significance was set at p=0.05. Comparison of pre-treatment to post-treatment variables revealed significant changes in the transverse dimension related to both maxillary skeletal and dental structures and palatal vault angle, resulting in a widened palatal vault (p<0.05). Hard palate showed no significant movement in the vertical and anteroposterior planes. Nasal cavity width increased on a mean value of 0.93 mm(SD=0.23, p<0.05). Maxillary sinus volume remained virtually stable. No significant age differences were observed in the sample. Hyrax expansion therapy did not have a significant impact on maxillary sinus volume.

Does hyrax expansion therapy affect maxillary sinus volume? A cone-beam computed tomography report

Energy Technology Data Exchange (ETDEWEB)

Darsey, Drew M.; English, Jeryl D.; Ellis, Randy K.; Akyalcin, Sercan [School of Dentistry, University of Texas Health Science Center at Houston, Houston (United States); Kau, Chung H [School of Dentistry, University of Alabama at Birmingham, Birmingham (United States)

2012-06-15

The aim of this study was to investigate the initial effects of maxillary expansion therapy with Hyrax appliance and to evaluate the related changes in maxillary sinus volume. Thirty patients (20 females, 10 males; 13.8 years) requiring maxillary expansion therapy, as part of their comprehensive orthodontic treatment, were examined. Each patient had cone-beam computed tomography (CBCT) images taken before (T1) and after (T2) maxillary expansion therapy with a banded Hyrax appliance. Multiplanar slices were used to measure linear dimensions and palatal vault angle. Volumetric analysis was used to measure maxillary sinus volumes. Student t tests were used to compare the pre- and post-treatment measurements. Additionally, differences between two age groups were compared with Mann-Whitney U test. The level of significance was set at p=0.05. Comparison of pre-treatment to post-treatment variables revealed significant changes in the transverse dimension related to both maxillary skeletal and dental structures and palatal vault angle, resulting in a widened palatal vault (p<0.05). Hard palate showed no significant movement in the vertical and anteroposterior planes. Nasal cavity width increased on a mean value of 0.93 mm(SD=0.23, p<0.05). Maxillary sinus volume remained virtually stable. No significant age differences were observed in the sample. Hyrax expansion therapy did not have a significant impact on maxillary sinus volume.

Utilization of cone-beam CT for offline evaluation of target volume coverage during prostate image-guided radiotherapy based on bony anatomy alignment.

Science.gov (United States)

Paluska, Petr; Hanus, Josef; Sefrova, Jana; Rouskova, Lucie; Grepl, Jakub; Jansa, Jan; Kasaova, Linda; Hodek, Miroslav; Zouhar, Milan; Vosmik, Milan; Petera, Jiri

2012-01-01

To assess target volume coverage during prostate image-guided radiotherapy based on bony anatomy alignment and to assess possibility of safety margin reduction. Implementation of IGRT should influence safety margins. Utilization of cone-beam CT provides current 3D anatomic information directly in irradiation position. Such information enables reconstruction of the actual dose distribution. Seventeen prostate patients were treated with daily bony anatomy image-guidance. Cone-beam CT (CBCT) scans were acquired once a week immediately after bony anatomy alignment. After the prostate, seminal vesicles, rectum and bladder were contoured, the delivered dose distribution was reconstructed. Target dose coverage was evaluated by the proportion of the CTV encompassed by the 95% isodose. Original plans employed a 1 cm safety margin. Alternative plans assuming a smaller 7 mm margin between CTV and PTV were evaluated in the same way. Rectal and bladder volumes were compared with the initial ones. Rectal and bladder volumes irradiated with doses higher than 75 Gy, 70 Gy, 60 Gy, 50 Gy and 40 Gy were analyzed. In 12% of reconstructed plans the prostate coverage was not sufficient. The prostate underdosage was observed in 5 patients. Coverage of seminal vesicles was not satisfactory in 3% of plans. Most of the target underdosage corresponded to excessive rectal or bladder filling. Evaluation of alternative plans assuming a smaller 7 mm margin revealed 22% and 11% of plans where prostate and seminal vesicles coverage, respectively, was compromised. These were distributed over 8 and 7 patients, respectively. Sufficient dose coverage of target volumes was not achieved for all patients. Reducing of safety margin is not acceptable. Initial rectal and bladder volumes cannot be considered representative for subsequent treatment.

Quantification of bone quality using different cone beam computed tomography devices: Accuracy assessment for edentulous human mandibles.

Science.gov (United States)

Van Dessel, Jeroen; Nicolielo, Laura Ferreira Pinheiro; Huang, Yan; Slagmolen, Pieter; Politis, Constantinus; Lambrichts, Ivo; Jacobs, Reinhilde

To determine the accuracy of the latest cone beam computed tomography (CBCT) machines in comparison to multi-slice computer tomography (MSCT) and micro computed tomography (micro-CT) for objectively assessing trabecular and cortical bone quality prior to implant placement. Eight edentulous human mandibular bone samples were scanned with seven CBCT scanners (3D Accuitomo 170, i-CAT Next Generation, ProMax 3D Max, Scanora 3D, Cranex 3D, Newtom GiANO and Carestream 9300) and one MSCT system (Somatom Definition Flash) using the clinical exposure protocol with the highest resolution. Micro-CT (SkyScan 1174) images served as a gold standard. A volume of interest (VOI) comprising trabecular and cortical bone only was delineated on the micro-CT. After spatial alignment of all scan types, micro-CT VOIs were overlaid on the CBCT and MSCT images. Segmentation was applied and morphometric parameters were calculated for each scanner. CBCT and MSCT morphometric parameters were compared with micro-CT using mixed-effect models. Intraclass correlation analysis was used to grade the accuracy of each scanner in assessing trabecular and cortical quality in comparison with the gold standard. Bone structure patterns of each scanner were compared with micro-CT in 2D and 3D to facilitate the interpretation of the morphometric analysis. Morphometric analysis showed an overestimation of the cortical and trabecular bone quantity during CBCT and MSCT evaluation compared to the gold standard micro-CT. The trabecular thickness (Tb.Th) was found to be significantly (P 3D Max (180 µm), followed by the 3D Accuitomo 170 (200 µm), Carestream 9300 (220 µm), Newtom GiANO (240 µm), Cranex 3D (280 µm), Scanora 3D (300 µm), high resolution MSCT (310 µm), i-CAT Next Generation (430 µm) and standard resolution MSCT (510 µm). The underestimation of the cortical thickness (Ct.Th) in ProMax 3D Max (-10 µm), the overestimation in Newtom GiANO (10 µm) and the high resolution

Comparison of Volumes between Four-Dimensional Computed Tomography and Cone-Beam Computed Tomography Images using Dynamic Phantom

Energy Technology Data Exchange (ETDEWEB)

Kim, Seong Eun; Won, Hui Su; Hong, Joo Wan; Chang, Nam Jun; Jung, Woo Hyun; Choi, Byeong Don [Dept. of Radiation Oncology, Seoul National University Bundang Hospital, Sungnam (Korea, Republic of)

2016-12-15

The aim of this study was to compare the differences between the volumes acquired with four-dimensional computed tomography (4DCT)images with a reconstruction image-filtering algorithm and cone-beam computed tomography (CBCT) images with dynamic phantom. The 4DCT images were obtained from the computerized imaging reference systems (CIRS) phantom using a computed tomography (CT) simulator. We analyzed the volumes for maximum intensity projection (MIP), minimum intensity projection (MinIP) and average intensity projection (AVG) of the images obtained with the 4DCT scanner against those acquired from CBCT images with CT ranger tools. Difference in volume for node of 1, 2 and 3 cm between CBCT and 4DCT was 0.54⁓2.33, 5.16⁓8.06, 9.03⁓20.11 ml in MIP, respectively, 0.00⁓1.48, 0.00⁓8.47, 1.42⁓24.85 ml in MinIP, respectively and 0.00⁓1.17, 0.00⁓2.19, 0.04⁓3.35 ml in AVG, respectively. After a comparative analysis of the volumes for each nodal size, it was apparent that the CBCT images were similar to the AVG images acquired using 4DCT.

SU-E-T-143: Effect of X-Ray and Cone Beam CT Reconstruction Parameters On Estimation of Bone Volume of Mice Used in Aging Research

Energy Technology Data Exchange (ETDEWEB)

Russ, M; Pang, M; Troen, B; Rudin, S; Ionita, C [University at Buffalo, Buffalo, NY (United States)

2014-06-01

Purpose: To investigate the variations in bone volume calculations in mice involved in aging research when changing cone beam micro-CT x-ray and reconstruction parameters. Methods: Mouse spines were placed on an indexed turn table that rotated 0.5° per projection and imaged by a self-built micro CT machine containing a CCD-based high-resolution x-ray detector. After the full 360° rotation data set of object images was obtained, a standard filtered back-projection cone beam reconstruction was performed. Four different kVp's between 40–70 kVp in 10kVp increments were selected. For each kVp two mAs settings were used. Each acquisition was reconstructed using two voxel sizes (12 and 25μm) and two step angles, 0.5° and 1°, respectively. A LabView program was written to determine the total bone volume contained in the mouse's total spine volume (bone plus gaps) as a measure of spine health. First, the user selected the desired 512×512 reconstruction to view the whole spine volume which was then used to select a gray-level threshold that allowed for viewing of the bone structure, then another threshold to include gaps. The program returned bone volume, bone × gap volume, and their ratio, BVF. Results: The calculated bone volume fractions were compared as a function of tube potential. Cases with 25μm slice thickness showed trials with lower kVp's had greater image contrast, which resulted in higher calculated bone volume fractions. Cases with 12μm reconstructed slice thickness were significantly noisier, and showed no clear maximum BVF. Conclusion: Using the projection images and reconstructions acquired from the micro CT, it can be shown that the micro-CT x-ray and reconstruction parameters significantly affect the total bone volume calculations. When comparing mice cohorts treated with different therapies researchers need to be aware of such details and use volumes which were acquired and processed in identical conditions.

Cone Algorithm of Spinning Vehicles under Dynamic Coning Environment

Directory of Open Access Journals (Sweden)

Shuang-biao Zhang

2015-01-01

Full Text Available Due to the fact that attitude error of vehicles has an intense trend of divergence when vehicles undergo worsening coning environment, in this paper, the model of dynamic coning environment is derived firstly. Then, through investigation of the effect on Euler attitude algorithm for the equivalency of traditional attitude algorithm, it is found that attitude error is actually the roll angle error including drifting error and oscillating error, which is induced directly by dynamic coning environment and further affects the pitch angle and yaw angle through transferring. Based on definition of the cone frame and cone attitude, a cone algorithm is proposed by rotation relationship to calculate cone attitude, and the relationship between cone attitude and Euler attitude of spinning vehicle is established. Through numerical simulations with different conditions of dynamic coning environment, it is shown that the induced error of Euler attitude fluctuates by the variation of precession and nutation, especially by that of nutation, and the oscillating frequency of roll angle error is twice that of pitch angle error and yaw angle error. In addition, the rotation angle is more competent to describe the spinning process of vehicles under coning environment than Euler angle gamma, and the real pitch angle and yaw angle are calculated finally.

On the zero mode problem of the light-cone quantization

International Nuclear Information System (INIS)

Huang, Suzhou; Lin, Wei

1993-01-01

The light-cone quantization for theories involving arbitrarily interacting scalars is studied systematically. The zero mode, which plays a special role in the light-cone quantization, is treated explicitly. The arguments utilize a lattice regularization and the constrained path-integral method. It is shown, to all orders in coupling constants or the loop expansion, that the ghost fields, introduced to enforce the constraints, decouple from all the virtual processes in the infinite-volume limit. The only possibility for the light-cone quantization to deviate from the equal-time quantization is when the interaction is such that the bosonic ghost fields develop expectation values and consequently alter the location of the minimum point of the effective potential. 24 refs

Comparison of standardized uptake values measured on 18F-NaF PET/CT scans using three different tube current intensities

OpenAIRE

Agnes Araujo Valadares; Paulo Schiavom Duarte; Eduardo Bechtloff Woellner; George Barberio Coura-Filho; Marcelo Tatit Sapienza; Carlos Alberto Buchpiguel

2015-01-01

Objective: To analyze standardized uptake values (SUVs) using three different tube current intensities for attenuation correction on 18FNaF PET/CT scans. Materials and Methods: A total of 254 18F-NaF PET/CT studies were analyzed using 10, 20 and 30 mAs. The SUVs were calculated in volumes of interest (VOIs) drawn on three skeletal regions, namely, right proximal humeral diaphysis (RH), right proximal femoral diaphysis (RF), and first lumbar vertebra (LV1) in a total of 712 VOIs. The analyses ...

Proton radiography of intense-laser-irradiated wire-attached cone targets

International Nuclear Information System (INIS)

Yabuuchi, T.; Sawada, H.; Bartal, T.; Beg, F.N.; Batani, D.; Gizzi, L.A.; Key, M.H.; Mackinnon, A.J.; McLean, H.S.; Patel, P.K.; Norreys, P.A.; Spindloe, C.; Stephens, R.B.; Wei, M.S.; Theobald, W.

2011-01-01

Measurements of extreme electrostatic and magnetic fields are of interest for the study of high-energy-density plasmas. Results of proton deflectometry of cone-wire targets that are of interest to fast-ignition inertial confinement fusion are presented. (authors)

Calculating potential error in sodium MRI with respect to the analysis of small objects.

Science.gov (United States)

Stobbe, Robert W; Beaulieu, Christian

2018-06-01

To facilitate correct interpretation of sodium MRI measurements, calculation of error with respect to rapid signal decay is introduced and combined with that of spatially correlated noise to assess volume-of-interest (VOI) 23 Na signal measurement inaccuracies, particularly for small objects. Noise and signal decay-related error calculations were verified using twisted projection imaging and a specially designed phantom with different sized spheres of constant elevated sodium concentration. As a demonstration, lesion signal measurement variation (5 multiple sclerosis participants) was compared with that predicted from calculation. Both theory and phantom experiment showed that VOI signal measurement in a large 10-mL, 314-voxel sphere was 20% less than expected on account of point-spread-function smearing when the VOI was drawn to include the full sphere. Volume-of-interest contraction reduced this error but increased noise-related error. Errors were even greater for smaller spheres (40-60% less than expected for a 0.35-mL, 11-voxel sphere). Image-intensity VOI measurements varied and increased with multiple sclerosis lesion size in a manner similar to that predicted from theory. Correlation suggests large underestimation of 23 Na signal in small lesions. Acquisition-specific measurement error calculation aids 23 Na MRI data analysis and highlights the limitations of current low-resolution methodologies. Magn Reson Med 79:2968-2977, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

The Power of Neuroimaging Biomarkers for Screening Frontotemporal Dementia

Science.gov (United States)

McMillan, Corey T.; Avants, Brian B.; Cook, Philip; Ungar, Lyle; Trojanowski, John Q.; Grossman, Murray

2014-01-01

Frontotemporal dementia (FTD) is a clinically and pathologically heterogeneous neurodegenerative disease that can result from either frontotemporal lobar degeneration (FTLD) or Alzheimer’s disease (AD) pathology. It is critical to establish statistically powerful biomarkers that can achieve substantial cost-savings and increase feasibility of clinical trials. We assessed three broad categories of neuroimaging methods to screen underlying FTLD and AD pathology in a clinical FTD series: global measures (e.g., ventricular volume), anatomical volumes of interest (VOIs) (e.g., hippocampus) using a standard atlas, and data-driven VOIs using Eigenanatomy. We evaluated clinical FTD patients (N=93) with cerebrospinal fluid, gray matter (GM) MRI, and diffusion tensor imaging (DTI) to assess whether they had underlying FTLD or AD pathology. Linear regression was performed to identify the optimal VOIs for each method in a training dataset and then we evaluated classification sensitivity and specificity in an independent test cohort. Power was evaluated by calculating minimum sample sizes (mSS) required in the test classification analyses for each model. The data-driven VOI analysis using a multimodal combination of GM MRI and DTI achieved the greatest classification accuracy (89% SENSITIVE; 89% SPECIFIC) and required a lower minimum sample size (N=26) relative to anatomical VOI and global measures. We conclude that a data-driven VOI approach employing Eigenanatomy provides more accurate classification, benefits from increased statistical power in unseen datasets, and therefore provides a robust method for screening underlying pathology in FTD patients for entry into clinical trials. PMID:24687814

Polyhedral combinatorics of UPGMA cones

OpenAIRE

Davidson, Ruth; Sullivant, Seth

2013-01-01

Distance-based methods such as UPGMA (Unweighted Pair Group Method with Arithmetic Mean) continue to play a significant role in phylogenetic research. We use polyhedral combinatorics to analyze the natural subdivision of the positive orthant induced by classifying the input vectors according to tree topologies returned by the algorithm. The partition lattice informs the study of UPGMA trees. We give a closed form for the extreme rays of UPGMA cones on n taxa, and compute the normalized volume...

Cone beam volume tomography: an imaging option for diagnosis of complex mandibular third molar anatomical relationships.

Science.gov (United States)

Danforth, Robert A; Peck, Jerry; Hall, Paul

2003-11-01

Complex impacted third molars present potential treatment complications and possible patient morbidity. Objectives of diagnostic imaging are to facilitate diagnosis, decision making, and enhance treatment outcomes. As cases become more complex, advanced multiplane imaging methods allowing for a 3-D view are more likely to meet these objectives than traditional 2-D radiography. Until recently, advanced imaging options were somewhat limited to standard film tomography or medical CT, but development of cone beam volume tomography (CBVT) multiplane 3-D imaging systems specifically for dental use now provides an alternative imaging option. Two cases were utilized to compare the role of CBVT to these other imaging options and to illustrate how multiplane visualization can assist the pretreatment evaluation and decision-making process for complex impacted mandibular third molar cases.

Properties of image intensifier-related halation artifact in limited volume cone-beam CT for dental use

International Nuclear Information System (INIS)

Hirukawa, Akiko; Okumura, Shinji; Matsuo, Ayae; Yokoi, Midori; Gotoh, Kenichi; Katsumata, Akitoshi; Naitoh, Munetaka; Ariji, Eiichiro

2006-01-01

Artifacts due to halation from an image intensifier (I.I.)/charge coupled device (CCD) system appear on limited-volume cone-beam computed tomography (CBCT). Regarding anterior tooth imaging, properties of this artifact in the geometrical relationships between field of view (FOV) and objective jaw region were studied. A water-filled plastic cylinder was used as a phantom of the head. A test object was constructed as a bone-equivalent phantom to be imaged. The test object was set in the phantom at positions corresponding to the anterior tooth arch. Position of the test object was shifted to simulate individual variations in the thickness of the labial soft tissue. Limited-volume CBCT images were acquired using a 3DX system in the various offset FOV position. The affection of an artifact was evaluated by the size of the object's image. The position of the test object in the phantom, i.e. the thickness of the labial soft tissue contributes to the intensity of artifact. However, even when the labial soft tissue was thick, affection from artifact was prominent when the FOV was set so that the image of the test object was depicted near the margin of FOV. (author)

Effect of inlet cone pipe angle in catalytic converter

Science.gov (United States)

Amira Zainal, Nurul; Farhain Azmi, Ezzatul; Arifin Samad, Mohd

2018-03-01

The catalytic converter shows significant consequence to improve the performance of the vehicle start from it launched into production. Nowadays, the geometric design of the catalytic converter has become critical to avoid the behavior of backpressure in the exhaust system. The backpressure essentially reduced the performance of vehicles and increased the fuel consumption gradually. Consequently, this study aims to design various models of catalytic converter and optimize the volume of fluid flow inside the catalytic converter by changing the inlet cone pipe angles. Three different geometry angles of the inlet cone pipe of the catalytic converter were assessed. The model is simulated in Solidworks software to determine the optimum geometric design of the catalytic converter. The result showed that by decreasing the divergence angle of inlet cone pipe will upsurge the performance of the catalytic converter.

Model-based segmentation in orbital volume measurement with cone beam computed tomography and evaluation against current concepts.

Science.gov (United States)

Wagner, Maximilian E H; Gellrich, Nils-Claudius; Friese, Karl-Ingo; Becker, Matthias; Wolter, Franz-Erich; Lichtenstein, Juergen T; Stoetzer, Marcus; Rana, Majeed; Essig, Harald

2016-01-01

Objective determination of the orbital volume is important in the diagnostic process and in evaluating the efficacy of medical and/or surgical treatment of orbital diseases. Tools designed to measure orbital volume with computed tomography (CT) often cannot be used with cone beam CT (CBCT) because of inferior tissue representation, although CBCT has the benefit of greater availability and lower patient radiation exposure. Therefore, a model-based segmentation technique is presented as a new method for measuring orbital volume and compared to alternative techniques. Both eyes from thirty subjects with no known orbital pathology who had undergone CBCT as a part of routine care were evaluated (n = 60 eyes). Orbital volume was measured with manual, atlas-based, and model-based segmentation methods. Volume measurements, volume determination time, and usability were compared between the three methods. Differences in means were tested for statistical significance using two-tailed Student's t tests. Neither atlas-based (26.63 ± 3.15 mm(3)) nor model-based (26.87 ± 2.99 mm(3)) measurements were significantly different from manual volume measurements (26.65 ± 4.0 mm(3)). However, the time required to determine orbital volume was significantly longer for manual measurements (10.24 ± 1.21 min) than for atlas-based (6.96 ± 2.62 min, p < 0.001) or model-based (5.73 ± 1.12 min, p < 0.001) measurements. All three orbital volume measurement methods examined can accurately measure orbital volume, although atlas-based and model-based methods seem to be more user-friendly and less time-consuming. The new model-based technique achieves fully automated segmentation results, whereas all atlas-based segmentations at least required manipulations to the anterior closing. Additionally, model-based segmentation can provide reliable orbital volume measurements when CT image quality is poor.

Cone Beam CT Imaging Analysis of Interfractional Variations in Bladder Volume and Position During Radiotherapy for Bladder Cancer

International Nuclear Information System (INIS)

Yee, Don; Parliament, Matthew; Rathee, Satyapal; Ghosh, Sunita; Ko, Lawrence; Murray, Brad

2010-01-01

Purpose: To quantify daily bladder size and position variations during bladder cancer radiotherapy. Methods and Materials: Ten bladder cancer patients underwent daily cone beam CT (CBCT) imaging of the bladder during radiotherapy. Bladder and planning target volumes (bladder/PTV) from CBCT and planning CT scans were compared with respect to bladder center-of-mass shifts in the x (lateral), y (anterior-posterior), and z (superior-inferior) coordinates, bladder/PTV size, bladder/PTV margin positions, overlapping areas, and mutually exclusive regions. Results: A total of 262 CBCT images were obtained from 10 bladder cancer patients. Bladder center of mass shifted most in the y coordinate (mean, -0.32 cm). The anterior bladder wall shifted the most (mean, -0.58 cm). Mean ratios of CBCT-derived bladder and PTV volumes to planning CT-derived counterparts were 0.83 and 0.88. The mean CBCT-derived bladder volume (± standard deviation [SD]) outside the planning CT counterpart was 29.24 cm 3 (SD, 29.71 cm 3 ). The mean planning CT-derived bladder volume outside the CBCT counterpart was 47.74 cm 3 (SD, 21.64 cm 3 ). The mean CBCT PTV outside the planning CT-derived PTV was 47.35 cm 3 (SD, 36.51 cm 3 ). The mean planning CT-derived PTV outside the CBCT-derived PTV was 93.16 cm 3 (SD, 50.21). The mean CBCT-derived bladder volume outside the planning PTV was 2.41 cm 3 (SD, 3.97 cm 3 ). CBCT bladder/ PTV volumes significantly differed from planning CT counterparts (p = 0.047). Conclusions: Significant variations in bladder and PTV volume and position occurred in patients in this trial.

Image-derived input function obtained in a 3TMR-brainPET

Energy Technology Data Exchange (ETDEWEB)

Silva, N.A. da [Institute of Biophysics and Biomedical Engineering, University of Lisbon (Portugal); Institute of Neurosciences and Medicine - 4, Juelich (Germany); Herzog, H., E-mail: h.herzog@fz-juelich.de [Institute of Neurosciences and Medicine - 4, Juelich (Germany); Weirich, C.; Tellmann, L.; Rota Kops, E. [Institute of Neurosciences and Medicine - 4, Juelich (Germany); Hautzel, H. [Department of Nuclear Medicine (KME), University of Duesseldorf, Medical Faculty at Research Center Juelich, Juelich (Germany); Almeida, P. [Institute of Biophysics and Biomedical Engineering, University of Lisbon (Portugal)

2013-02-21

Aim: The combination of a high-resolution MR-compatible BrainPET insert operated within a 3 T MAGNETOM Trio MR scanner is an excellent tool for obtaining an image derived input function (IDIF), due to simultaneous imaging. In this work, we explore the possibility of obtaining an IDIF from volumes of interest (VOI) defined over the carotid arteries (CAs) using the MR data. Material and methods: FDG data from three patients without brain disorders were included. VOIs were drawn bilaterally over the CAs on a MPRAGE image using a 50% isocontour (MR50VOI). CA PET/MR co-registration was examined based on an individual and combined CA co-registration. After that, to estimate the IDIF, the MR50VOI average (IDIF-A), four hottest pixels per plane (IDIF-4H) and four hottest pixels in VOI (IDIF-4V) were considered. A model-based correction for residual partial volume effects involving venous blood samples was applied, from which partial volume (PV) and spillover (SP) coefficients were estimated. Additionally, a theoretical PV coefficient (PVt) was calculated based on MR50VOI. Results: The results show an excellent co-registration between the MR and PET, with an area under the curve ratio between both co-registration methods of 1.00±0.04. A good agreement between PV and PVt was found for IDIF-A, with PV of 0.39±0.06 and PVt 0.40±0.03, and for IDIF-4H, with PV of 0.47±0.05 and PVt 0.47±0.03. The SPs were 0.20±0.03 and 0.21±0.03 for IDIF-A and IDIF-4H, respectively. Conclusion: The integration of a high resolution BrainPET in an MR scanner allows to obtain an IDIF from an MR-based VOI. This must be corrected for a residual partial volume effect.

Renal cortical and medullary blood flow responses to altered NO-availability in humans

DEFF Research Database (Denmark)

Damkjaer, Mads; Vafaee, Manoucher; Møller, Michael Lehd

2010-01-01

The objective was to quantify regional renal blood flow in humans. In nine young volunteers on a controlled diet, the lower abdomen was CT-scanned and regional renal blood flow determined by positron emission tomography (PET) scanning using H(2)(15)O as tracer. Measurements were performed...... of one voxel were eliminated stepwise from the external surface of the VOI ('voxel peeling'), and the blood flow subsequently determined in each new, reduced VOI. Blood flow in the shrinking volumes of interest (VOIs) decreased as the number of cycles of voxel peeling increased. After 4-5 cycles, blood...... flow was not reduced further by additional voxel peeling. This volume-insensitive flow was measured to be 2.30 ±0.17 ml·(g·min)(-1) during the control period; it increased during infusion of glyceryl nitrate to 2.97 ±0.18 ml·(g·min)(-1) (p...

A unified analysis of FBP-based algorithms in helical cone-beam and circular cone- and fan-beam scans

International Nuclear Information System (INIS)

Pan Xiaochuan; Xia Dan; Zou Yu; Yu Lifeng

2004-01-01

A circular scanning trajectory is and will likely remain a popular choice of trajectory in computed tomography (CT) imaging because it is easy to implement and control. Filtered-backprojection (FBP)-based algorithms have been developed previously for approximate and exact reconstruction of the entire image or a region of interest within the image in circular cone-beam and fan-beam cases. Recently, we have developed a 3D FBP-based algorithm for image reconstruction on PI-line segments in a helical cone-beam scan. In this work, we demonstrated that the 3D FBP-based algorithm indeed provided a rather general formulation for image reconstruction from divergent projections (such as cone-beam and fan-beam projections). On the basis of this formulation we derived new approximate or exact algorithms for image reconstruction in circular cone-beam or fan-beam scans, which can be interpreted as special cases of the helical scan. Existing algorithms corresponding to the derived algorithms were identified. We also performed a preliminary numerical study to verify our theoretical results in each of the cases. The results in the work can readily be generalized to other non-circular trajectories

3D exemplar-based random walks for tooth segmentation from cone-beam computed tomography images

Energy Technology Data Exchange (ETDEWEB)

Pei, Yuru, E-mail: peiyuru@cis.pku.edu.cn; Ai, Xingsheng; Zha, Hongbin [Department of Machine Intelligence, School of EECS, Peking University, Beijing 100871 (China); Xu, Tianmin [School of Stomatology, Stomatology Hospital, Peking University, Beijing 100081 (China); Ma, Gengyu [uSens, Inc., San Jose, California 95110 (United States)

2016-09-15

Purpose: Tooth segmentation is an essential step in acquiring patient-specific dental geometries from cone-beam computed tomography (CBCT) images. Tooth segmentation from CBCT images is still a challenging task considering the comparatively low image quality caused by the limited radiation dose, as well as structural ambiguities from intercuspation and nearby alveolar bones. The goal of this paper is to present and discuss the latest accomplishments in semisupervised tooth segmentation with adaptive 3D shape constraints. Methods: The authors propose a 3D exemplar-based random walk method of tooth segmentation from CBCT images. The proposed method integrates semisupervised label propagation and regularization by 3D exemplar registration. To begin with, the pure random walk method is to get an initial segmentation of the teeth, which tends to be erroneous because of the structural ambiguity of CBCT images. And then, as an iterative refinement, the authors conduct a regularization by using 3D exemplar registration, as well as label propagation by random walks with soft constraints, to improve the tooth segmentation. In the first stage of the iteration, 3D exemplars with well-defined topologies are adapted to fit the tooth contours, which are obtained from the random walks based segmentation. The soft constraints on voxel labeling are defined by shape-based foreground dentine probability acquired by the exemplar registration, as well as the appearance-based probability from a support vector machine (SVM) classifier. In the second stage, the labels of the volume-of-interest (VOI) are updated by the random walks with soft constraints. The two stages are optimized iteratively. Instead of the one-shot label propagation in the VOI, an iterative refinement process can achieve a reliable tooth segmentation by virtue of exemplar-based random walks with adaptive soft constraints. Results: The proposed method was applied for tooth segmentation of twenty clinically captured CBCT

Mathematical Modelling of Fluid Flow in Cone and Cavitation Formation

Directory of Open Access Journals (Sweden)

Milada KOZUBKOVÁ

2011-06-01

Full Text Available Problem of cavitation is the undesirable phenomena occuring in the fluid flow in many hydraulic application (pumps, turbines, valves, etc.. Therefore this is in the focus of interest using experimental and mathematical methods. Based on cavitation modelling in Laval nozzle results and experience [1], [2], [4], following problem described as the water flow at the outlet from turbine blade wheel was solved. Primarily the problem is simplified into modelling of water flow in cone. Profiles of axial, radial and tangential velocity are defined on inlet zone. The value of pressure is defined on the outlet. Boundary conditions were defined by main investigator of the grant project – Energy Institute, Victor Kaplan’s Department of Fluid Engineering, Faculty of Mechanical Engineering, Brno University of Technology. The value of air volume was insignificant. Cavitation was solved by Singhal model of cavitation.

Two-Tier VoI Prioritization System on Requirement-Based Data Streaming toward IoT

Directory of Open Access Journals (Sweden)

Sunyanan Choochotkaew

2017-01-01

Full Text Available Toward the world of Internet of Things, people utilize knowledge from sensor streams in various kinds of smart applications. The number of sensing devices is rapidly increasing along with the amount of sensing data. Consequently, a bottleneck problem at the local gateway has attracted high concern. An example scenario is smart elderly houses in rural areas where each house installs thousands of sensors and all connect to resource-limited and unstable 2G/3G networks. The bottleneck state can incur unacceptable latency and loss of significant data due to the limited waiting-queue. Orthogonally to the existing solutions, we propose a two-tier prioritization system to enhance information quality, indicated by VoI, at the local gateway. The proposed system has been designed to support several requirements with several conflicting criteria over shared sensing streams. Our approach adopts Multicriteria Decision Analysis technique to merge requirements and to assess the VoI. We introduce the framework that can reduce the computational cost by precalculation. Through a case study of building management systems, we have shown that our merge algorithm can provide 0.995 cosine-similarity for representing all user requirements and the evaluation approach can obtain satisfaction values around 3 times higher than the naïve strategies for the top-list data.

Trabecular bone structure parameters from 3D image processing of clinical multi-slice and cone-beam computed tomography data

Energy Technology Data Exchange (ETDEWEB)

Klintstroem, Eva; Smedby, Oerjan [Linkoeping University, Center for Medical Image Science and Visualization (CMIV), Linkoeping (Sweden); UHL County Council of Oestergoetland, Department of Radiology, Linkoeping (Sweden); Linkoeping University, Department of Medical and Health Sciences (IMH)/Radiology, Linkoeping (Sweden); Moreno, Rodrigo [Linkoeping University, Center for Medical Image Science and Visualization (CMIV), Linkoeping (Sweden); Linkoeping University, Department of Medical and Health Sciences (IMH)/Radiology, Linkoeping (Sweden); Brismar, Torkel B. [KUS Huddinge, Department of Clinical Science, Intervention and Technology at Karolinska Institutet and Department of Radiology, Stockholm (Sweden)

2014-02-15

Bone strength depends on both mineral content and bone structure. The aim of this in vitro study was to develop a method of quantitatively assessing trabecular bone structure by applying three-dimensional image processing to data acquired with multi-slice and cone-beam computed tomography using micro-computed tomography as a reference. Fifteen bone samples from the radius were examined. After segmentation, quantitative measures of bone volume, trabecular thickness, trabecular separation, trabecular number, trabecular nodes, and trabecular termini were obtained. The clinical machines overestimated bone volume and trabecular thickness and underestimated trabecular nodes and number, but cone-beam CT to a lesser extent. Parameters obtained from cone beam CT were strongly correlated with μCT, with correlation coefficients between 0.93 and 0.98 for all parameters except trabecular termini. The high correlation between cone-beam CT and micro-CT suggest the possibility of quantifying and monitoring changes of trabecular bone microarchitecture in vivo using cone beam CT. (orig.)

Localization of Epileptogenic Zones using Partical Volume Corrected FDG Uptake on FDG PET and Voxel Based Morphometry on MRI

Energy Technology Data Exchange (ETDEWEB)

Kang, Won Jun; Lee, Ho Young; Lee, Jae Sung; Lee, Dong Soo; Lee, Sang Kun; Chung, June Key; Lee, Myung Chul [College of Medicine, Univ. of Seoul National, Seoul (Korea, Republic of)

2003-07-01

Partial volume corrected (PVC) FDG uptake yields information about regional metabolic level void of volume change, and voxel based morphometry (VBM) yields objective information regarding gray matter concentration. We investigated the roles of PVC PET and VBM to localize epileptogenic zones in medial temporal lobe epilepsy (mTLE) and non-lesional neocortical epilepsy. As a control group for PVC, 40 normal volunteers without history of neurologic or psychiatric diseases underwent FDG PET and MRI. Seventeen mTLE patients (M: F=7: 10, age=309 y) and nine neocortical epilepsy patients (M: F=6: 3, age=246, lateral temporal: 5, frontal: 3, occipital: 1) confirmed by surgery or epilepsy board meeting were enrolled. Standard VBM analysis was performed using individual MRI images compared with those of age-matched controls. For PVC, FDG PET was co-registered with its own MRI. PVC PET was obtained by dividing spillover-corrected PET by smoothed gray matter image pixel by pixel. SPAM was applied as a mask of volume of interest (VOI) to calculate gyral FDG uptake on PVC-FDG PET. Hippocampus, amygdala, superior, middle, inferior temporal gyrus and parahippocampal gyrus were the gyral SPAM VOIs in mTLE. Globally normalized PVC-FDG counts were compared with those of age-matched controls in mTLE and neocortical epilepsy patients. In mTlE, PVC-FDG PET correctly localized epileptogenic zones with the accuracy of 76% (13/17) in hippocampus and 82% (14/17) in any of six regions. VBM correctly localized 59% (10/17) in mTLE. In neocortical epilepsy, PVC-FDG PET localized epileptogenic zones in 44%, and VBM in 33%, Using VBM and PVC-FDG PET altogether, epileptogenic zones were localized in 66% (6/9). In mTLE, gyral PVC FDG uptake of temporal lobes was useful in localizing epileptogenic zones by demonstrating partial volume-void FDG concentration. In non-lesional cryptogenic neocortical epilepsy, combination of PVC-FDG PET and VBM is recommended to localize epileptogenic zones.

Direct linear measurement of root dentin thickness and dentin volume changes with post space preparation: A cone-beam computed tomography study

Directory of Open Access Journals (Sweden)

Shoeb Yakub Shaikh

2018-01-01

Full Text Available Aim: The purpose of the present study was direct linear measurement of dentin thickness and dentin volume changes for post space preparation with cone-beam computed tomography (CBCT. Materials and Methods: Ten maxillary central incisors were scanned, before and after root canal and post space preparation, with Orthophos XG three-dimensional hybrid unit. Thirteen axial section scans of each tooth from orifice to apex and dentin thickness for buccal, lingual, mesial, and distal were measured using proprietary measuring tool and thereafter subjected to statistical analysis. Furthermore, dentin volume was evaluated using ITK-SNAP software. Results: There was statistically significant difference between the dentin thickness in pre- and postinstrumentation (paired t-test and also between different groups (one-way ANOVA. In the shortest post length of 4.5mm the post space preparation resulted in 2.17% loss of hard tissue volume, where as 11mm longest post length post space preparation resulted in >40% loss of hard tissue volume. Conclusion: CBCT axial section scan for direct measurements of root dentin thickness can be guideline before and after post space preparation for selection of drill length and diameter.

Receiver operating characteristic (ROC) curve for classification of {sup 18}F-NaF uptake on PET/CT

Energy Technology Data Exchange (ETDEWEB)

Valadares, Agnes Araujo, E-mail: agnesvaladares@me.com [Universidade de Sao Paulo (HC/FM/USP), SP (Brazil). Hospital das Clinicas. Fac. de Mediciana; Duarte, Paulo Schiavom; Ono, Carla Rachel; Coura-Filho, George Barberio; Sado, Heitor Naoki; Carvalho, Giovanna [Instituto do Cancer do Estado de Sao Paulo Octavio Frias de Oliveira (ICESP), Sao Paulo, SP (Brazil). Servico de Medicina Nuclear; Sapienza, Marcelo Tatit; Buchpiguel, Carlos Alberto [Universidade de Sao Paulo (FM/USP), Sao Paulo, SP (Brazil). Fac. de Medicina. Dept. de Radiologia e Oncologia

2016-01-15

Objective: To assess the cutoff values established by ROC curves to classify {sup 18}F-NaF uptake as normal or malignant. Materials and Methods: PET/CT images were acquired 1 hour after administration of 185 MBq of {sup 18}F-NaF. Volumes of interest (VOIs) were drawn on three regions of the skeleton as follows: proximal right humerus diaphysis (HD), proximal right femoral diaphysis (FD) and first vertebral body (VB1), in a total of 254 patients, totalling 762 VOIs. The uptake in the VOIs was classified as normal or malignant on the basis of the radiopharmaceutical distribution pattern and of the CT images. A total of 675 volumes were classified as normal and 52 were classified as malignant. Thirty-five VOIs classified as indeterminate or nonmalignant lesions were excluded from analysis. The standardized uptake value (SUV) measured on the VOIs were plotted on an ROC curve for each one of the three regions. The area under the ROC (AUC) as well as the best cutoff SUVs to classify the VOIs were calculated. The best cutoff values were established as the ones with higher result of the sum of sensitivity and specificity. Results: The AUCs were 0.933, 0.889 and 0.975 for UD, FD and VB1, respectively. The best SUV cutoffs were 9.0 (sensitivity: 73%; specificity: 99%), 8.4 (sensitivity: 79%; specificity: 94%) and 21.0 (sensitivity: 93%; specificity: 95%) for UD, FD and VB1, respectively. Conclusion: The best cutoff value varies according to bone region of analysis and it is not possible to establish one value for the whole body. (author)

Relationship between foveal cone specialization and pit morphology in albinism.

Science.gov (United States)

Wilk, Melissa A; McAllister, John T; Cooper, Robert F; Dubis, Adam M; Patitucci, Teresa N; Summerfelt, Phyllis; Anderson, Jennifer L; Stepien, Kimberly E; Costakos, Deborah M; Connor, Thomas B; Wirostko, William J; Chiang, Pei-Wen; Dubra, Alfredo; Curcio, Christine A; Brilliant, Murray H; Summers, C Gail; Carroll, Joseph

2014-05-20

Albinism is associated with disrupted foveal development, though intersubject variability is becoming appreciated. We sought to quantify this variability, and examine the relationship between foveal cone specialization and pit morphology in patients with a clinical diagnosis of albinism. We recruited 32 subjects with a clinical diagnosis of albinism. DNA was obtained from 25 subjects, and known albinism genes were analyzed for mutations. Relative inner and outer segment (IS and OS) lengthening (fovea-to-perifovea ratio) was determined from manually segmented spectral domain-optical coherence tomography (SD-OCT) B-scans. Foveal pit morphology was quantified for eight subjects from macular SD-OCT volumes. Ten subjects underwent imaging with adaptive optics scanning light ophthalmoscopy (AOSLO), and cone density was measured. We found mutations in 22 of 25 subjects, including five novel mutations. All subjects lacked complete excavation of inner retinal layers at the fovea, though four subjects had foveal pits with normal diameter and/or volume. Peak cone density and OS lengthening were variable and overlapped with that observed in normal controls. A fifth hyper-reflective band was observed in the outer retina on SD-OCT in the majority of the subjects with albinism. Foveal cone specialization and pit morphology vary greatly in albinism. Normal cone packing was observed in the absence of a foveal pit, suggesting a pit is not required for packing to occur. The degree to which retinal anatomy correlates with genotype or visual function remains unclear, and future examination of larger patient groups will provide important insight on this issue. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Three-dimensional focus of attention for iterative cone-beam micro-CT reconstruction

International Nuclear Information System (INIS)

Benson, T M; Gregor, J

2006-01-01

Three-dimensional iterative reconstruction of high-resolution, circular orbit cone-beam x-ray CT data is often considered impractical due to the demand for vast amounts of computer cycles and associated memory. In this paper, we show that the computational burden can be reduced by limiting the reconstruction to a small, well-defined portion of the image volume. We first discuss using the support region defined by the set of voxels covered by all of the projection views. We then present a data-driven preprocessing technique called focus of attention that heuristically separates both image and projection data into object and background before reconstruction, thereby further reducing the reconstruction region of interest. We present experimental results for both methods based on mouse data and a parallelized implementation of the SIRT algorithm. The computational savings associated with the support region are substantial. However, the results for focus of attention are even more impressive in that only about one quarter of the computer cycles and memory are needed compared with reconstruction of the entire image volume. The image quality is not compromised by either method

Synthesized interstitial lung texture for use in anthropomorphic computational phantoms

Science.gov (United States)

Becchetti, Marc F.; Solomon, Justin B.; Segars, W. Paul; Samei, Ehsan

2016-04-01

A realistic model of the anatomical texture from the pulmonary interstitium was developed with the goal of extending the capability of anthropomorphic computational phantoms (e.g., XCAT, Duke University), allowing for more accurate image quality assessment. Contrast-enhanced, high dose, thorax images for a healthy patient from a clinical CT system (Discovery CT750HD, GE healthcare) with thin (0.625 mm) slices and filtered back- projection (FBP) were used to inform the model. The interstitium which gives rise to the texture was defined using 24 volumes of interest (VOIs). These VOIs were selected manually to avoid vasculature, bronchi, and bronchioles. A small scale Hessian-based line filter was applied to minimize the amount of partial-volumed supernumerary vessels and bronchioles within the VOIs. The texture in the VOIs was characterized using 8 Haralick and 13 gray-level run length features. A clustered lumpy background (CLB) model with added noise and blurring to match CT system was optimized to resemble the texture in the VOIs using a genetic algorithm with the Mahalanobis distance as a similarity metric between the texture features. The most similar CLB model was then used to generate the interstitial texture to fill the lung. The optimization improved the similarity by 45%. This will substantially enhance the capabilities of anthropomorphic computational phantoms, allowing for more realistic CT simulations.

Cone-based Electrical Resistivity Tomography

Science.gov (United States)

Pidlisecky, A.; Knight, R.; Haber, E.

2005-05-01

Determining the 3D spatial distribution of subsurface properties is a critical part of managing the clean-up of contaminated sites. Most standard hydrologic methods sample small regions immediately adjacent to wells or testing devices. This provides data which are not representative of the entire region of interest. Furthermore, at many contaminated sites invasive methods are not acceptable, due to the risks associated with contacting and spreading the contaminants. To address these issues, we have developed a minimally invasive technology that provides information about the 3D distribution of electrical conductivity. This new technique, cone-based electrical resistivity tomography (C-bert), involves placing several permanent current electrodes in the subsurface and using electrodes mounted on a cone penetrometer to measure the resultant potential field while advancing the cone into the subsurface. In addition to potential field measurements, we obtain the standard suite of cone-penetration measurements, including high resolution resistivity logs; these data can then be used to constrain the inversion of the potential field data. A major challenge of working with these data is that the cone penetrometer is highly conductive, and thus presents a large local perturbation around the measurement location. As the cone is very small (approximately 30mm in diameter) with respect to the total model space, explicitly modeling the cone is computationally demanding. We developed a method for solving the forward model that reduces computational time by an order of magnitude. This solution method, iteratively determined boundary conditions, makes it possible to correct for the cone effect before inversion of the data. Results from synthetic experiments suggest that the C-bert method of data acquisition can result in high quality electrical conductivity images of the subsurface. We tested the practicality of this technique by performing a field test of the C-bert system to image

Evaluation of software tools for automated identification of neuroanatomical structures in quantitative β-amyloid PET imaging to diagnose Alzheimer's disease

Energy Technology Data Exchange (ETDEWEB)

Tuszynski, Tobias; Luthardt, Julia; Butzke, Daniel; Tiepolt, Solveig; Seese, Anita; Barthel, Henryk [Leipzig University Medical Centre, Department of Nuclear Medicine, Leipzig (Germany); Rullmann, Michael; Hesse, Swen; Sabri, Osama [Leipzig University Medical Centre, Department of Nuclear Medicine, Leipzig (Germany); Leipzig University Medical Centre, Integrated Treatment and Research Centre (IFB) Adiposity Diseases, Leipzig (Germany); Gertz, Hermann-Josef [Leipzig University Medical Centre, Department of Psychiatry, Leipzig (Germany); Lobsien, Donald [Leipzig University Medical Centre, Department of Neuroradiology, Leipzig (Germany)

2016-06-15

For regional quantification of nuclear brain imaging data, defining volumes of interest (VOIs) by hand is still the gold standard. As this procedure is time-consuming and operator-dependent, a variety of software tools for automated identification of neuroanatomical structures were developed. As the quality and performance of those tools are poorly investigated so far in analyzing amyloid PET data, we compared in this project four algorithms for automated VOI definition (HERMES Brass, two PMOD approaches, and FreeSurfer) against the conventional method. We systematically analyzed florbetaben brain PET and MRI data of ten patients with probable Alzheimer's dementia (AD) and ten age-matched healthy controls (HCs) collected in a previous clinical study. VOIs were manually defined on the data as well as through the four automated workflows. Standardized uptake value ratios (SUVRs) with the cerebellar cortex as a reference region were obtained for each VOI. SUVR comparisons between ADs and HCs were carried out using Mann-Whitney-U tests, and effect sizes (Cohen's d) were calculated. SUVRs of automatically generated VOIs were correlated with SUVRs of conventionally derived VOIs (Pearson's tests). The composite neocortex SUVRs obtained by manually defined VOIs were significantly higher for ADs vs. HCs (p=0.010, d=1.53). This was also the case for the four tested automated approaches which achieved effect sizes of d=1.38 to d=1.62. SUVRs of automatically generated VOIs correlated significantly with those of the hand-drawn VOIs in a number of brain regions, with regional differences in the degree of these correlations. Best overall correlation was observed in the lateral temporal VOI for all tested software tools (r=0.82 to r=0.95, p<0.001). Automated VOI definition by the software tools tested has a great potential to substitute for the current standard procedure to manually define VOIs in β-amyloid PET data analysis. (orig.)

Geomorphometric variability of "monogenetic" volcanic cones: Evidence from Mauna Kea, Lanzarote and experimental cones

Science.gov (United States)

Kervyn, M.; Ernst, G. G. J.; Carracedo, J.-C.; Jacobs, P.

2012-01-01

Volcanic cones are the most common volcanic constructs on Earth. Their shape can be quantified using two morphometric ratios: the crater/cone base ratio (W cr/W co) and the cone height/width ratio (H co/W co). The average values for these ratios obtained over entire cone fields have been explained by the repose angle of loose granular material (i.e. scoria) controlling cone slopes. The observed variability in these ratios between individual cones has been attributed to the effect of erosional processes or contrasting eruptive conditions on cone morphometry. Using a GIS-based approach, high spatial resolution Digital Elevation Models and airphotos, two new geomorphometry datasets for cone fields at Mauna Kea (Hawaii, USA) and Lanzarote (Canary Islands, Spain) are extracted and analyzed here. The key observation in these datasets is the great variability in morphometric ratios, even for simple-shape and well-preserved cones. Simple analog experiments are presented to analyze factors influencing the morphometric ratios. The formation of a crater is simulated within an analog cone (i.e. a sand pile) by opening a drainage conduit at the cone base. Results from experiments show that variability in the morphometric ratios can be attributed to variations in the width, height and horizontal offset of the drainage point relative to the cone symmetry axis, to the dip of the underlying slope or to the influence of a small proportion of fine cohesive material. GIS analysis and analog experiments, together with specific examples of cones documented in the field, suggest that the morphometric ratios for well-preserved volcanic cones are controlled by a combination of 1) the intrinsic cone material properties, 2) time-dependent eruption conditions, 3) the local setting, and 4) the method used to estimate the cone height. Implications for interpreting cone morphometry solely as either an age or as an eruption condition indicator are highlighted.

Molecular connectivity disruptions in males with major depressive disorder.

Science.gov (United States)

Pillai, Rajapillai Li; Zhang, Mengru; Yang, Jie; Mann, J John; Oquendo, Maria A; Parsey, Ramin V; DeLorenzo, Christine

2018-01-01

In most positron emission tomography (PET) molecular brain imaging studies, regions of interest have been defined anatomically and examined in isolation. However, by defining regions based on physiology and examining relationships between them, we may derive more sensitive measures of receptor abnormalities in conditions such as major depressive disorder (MDD). Using an average of 52 normalized binding potential maps, acquired using radiotracer [ 11 C]-WAY100635 and full arterial input analysis, we identified two molecular volumes of interest (VOIs) with contiguously high serotonin 1A receptor (5-HT 1A ) binding sites: the olfactory sulcus (OLFS) and a band of tissue including piriform, olfactory, and entorhinal cortex (PRF). We applied these VOIs to a separate cohort of 25 healthy control males and 16 males with MDD who received [ 11 C]-WAY100635 imaging. Patients with MDD had significantly higher binding than controls in both VOIs, ( p molecular connectivity, i.e. the correlation between binding of raphe nucleus (RN) 5-HT 1A autoreceptors and post-synaptic receptors in molecular VOIs. Molecular connectivity was significant in healthy controls ( p molecular connectivity allowed identification of MDD cases with high sensitivity (81%) and specificity (88%).

An Analysis Model for Water Cone Subsidence in Bottom Water Drive Reservoirs

Science.gov (United States)

Wang, Jianjun; Xu, Hui; Wu, Shucheng; Yang, Chao; Kong, lingxiao; Zeng, Baoquan; Xu, Haixia; Qu, Tailai

2017-12-01

Water coning in bottom water drive reservoirs, which will result in earlier water breakthrough, rapid increase in water cut and low recovery level, has drawn tremendous attention in petroleum engineering field. As one simple and effective method to inhibit bottom water coning, shut-in coning control is usually preferred in oilfield to control the water cone and furthermore to enhance economic performance. However, most of the water coning researchers just have been done on investigation of the coning behavior as it grows up, the reported studies for water cone subsidence are very scarce. The goal of this work is to present an analytical model for water cone subsidence to analyze the subsidence of water cone when the well shut in. Based on Dupuit critical oil production rate formula, an analytical model is developed to estimate the initial water cone shape at the point of critical drawdown. Then, with the initial water cone shape equation, we propose an analysis model for water cone subsidence in bottom water reservoir reservoirs. Model analysis and several sensitivity studies are conducted. This work presents accurate and fast analytical model to perform the water cone subsidence in bottom water drive reservoirs. To consider the recent interests in development of bottom drive reservoirs, our approach provides a promising technique for better understanding the subsidence of water cone.

A reconstruction method for cone-beam differential x-ray phase-contrast computed tomography.

Science.gov (United States)

Fu, Jian; Velroyen, Astrid; Tan, Renbo; Zhang, Junwei; Chen, Liyuan; Tapfer, Arne; Bech, Martin; Pfeiffer, Franz

2012-09-10

Most existing differential phase-contrast computed tomography (DPC-CT) approaches are based on three kinds of scanning geometries, described by parallel-beam, fan-beam and cone-beam. Due to the potential of compact imaging systems with magnified spatial resolution, cone-beam DPC-CT has attracted significant interest. In this paper, we report a reconstruction method based on a back-projection filtration (BPF) algorithm for cone-beam DPC-CT. Due to the differential nature of phase contrast projections, the algorithm restrains from differentiation of the projection data prior to back-projection, unlike BPF algorithms commonly used for absorption-based CT data. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a micro-focus x-ray tube source. Moreover, the numerical simulation and experimental results demonstrate that the proposed method can deal with several classes of truncated cone-beam datasets. We believe that this feature is of particular interest for future medical cone-beam phase-contrast CT imaging applications.

3D Monte Carlo model of optical transport in laser-irradiated cutaneous vascular malformations

Science.gov (United States)

Majaron, Boris; Milanič, Matija; Jia, Wangcun; Nelson, J. S.

2010-11-01

We have developed a three-dimensional Monte Carlo (MC) model of optical transport in skin and applied it to analysis of port wine stain treatment with sequential laser irradiation and intermittent cryogen spray cooling. Our MC model extends the approaches of the popular multi-layer model by Wang et al.1 to three dimensions, thus allowing treatment of skin inclusions with more complex geometries and arbitrary irradiation patterns. To overcome the obvious drawbacks of either "escape" or "mirror" boundary conditions at the lateral boundaries of the finely discretized volume of interest (VOI), photons exiting the VOI are propagated in laterally infinite tissue layers with appropriate optical properties, until they loose all their energy, escape into the air, or return to the VOI, but the energy deposition outside of the VOI is not computed and recorded. After discussing the selection of tissue parameters, we apply the model to analysis of blood photocoagulation and collateral thermal damage in treatment of port wine stain (PWS) lesions with sequential laser irradiation and intermittent cryogen spray cooling.

Cold knife cone biopsy

Science.gov (United States)

... biopsy; Pap smear - cone biopsy; HPV - cone biopsy; Human papilloma virus - cone biopsy; Cervix - cone biopsy; Colposcopy - cone biopsy Images Female reproductive anatomy Cold cone biopsy Cold cone removal References Baggish ...

Packing and deploying Soft Origami to and from cylindrical volumes with application to automotive airbags.

Science.gov (United States)

Bruton, Jared T; Nelson, Todd G; Zimmerman, Trent K; Fernelius, Janette D; Magleby, Spencer P; Howell, Larry L

2016-09-01

Packing soft-sheet materials of approximately zero bending stiffness using Soft Origami (origami patterns applied to soft-sheet materials) into cylindrical volumes and their deployment via mechanisms or internal pressure (inflation) is of interest in fields including automobile airbags, deployable heart stents, inflatable space habitats, and dirigible and parachute packing. This paper explores twofold patterns, the 'flasher' and the 'inverted-cone fold', for packing soft-sheet materials into cylindrical volumes. Two initial packing methods and mechanisms are examined for each of the flasher and inverted-cone fold patterns. An application to driver's side automobile airbags is performed, and deployment tests are completed to compare the influence of packing method and origami pattern on deployment performance. Following deployment tests, two additional packing methods for the inverted-cone fold pattern are explored and applied to automobile airbags. It is shown that modifying the packing method (using different methods to impose the same base pattern on the soft-sheet material) can lead to different deployment performance. In total, two origami patterns and six packing methods are examined, and the benefits of using Soft Origami patterns and packing methods are discussed. Soft Origami is presented as a viable method for efficiently packing soft-sheet materials into cylindrical volumes.

Eruptive and Geomorphic Processes at the Lathrop Wells Scoria Cone

International Nuclear Information System (INIS)

G. Valentine; D.J. Krier; F.V. Perry; G. Heiken

2006-01-01

The ∼80 ka Lathrop Wells volcano (southern Nevada, U.S.A.) preserves evidence for a range of explosive processes and emplacement mechanisms of pyroclastic deposits and lava fields in a small-volume basaltic center. Early cone building by Strombolian bursts was accompanied by development of a fan-like lava field reaching ∼800 m distance from the cone, built upon a gently sloping surface. Lava flows carried rafts of cone deposits, which provide indirect evidence for cone facies in lieu of direct exposures in the active quarry. Subsequent activity was of a violent Strombolian nature, with many episodes of sustained eruption columns up to a few km in height. These deposited layers of scoria lapilli and ash in different directions depending upon wind direction at the time of a given episode, reaching up to ∼20 km from the vent, and also produced the bulk of the scoria cone. Lava effusion migrated from south to north around the eastern base of the cone as accumulation of lavas successively reversed the topography at the base of the cone. Late lavas were emplaced during violent Strombolian activity and continued for some time after explosive eruptions had waned. Volumes of the eruptive products are: fallout--0.07 km 3 , scoria cone--0.02 km 3 , and lavas--0.03 km 3 . Shallow-derived xenolith concentrations suggest an upper bound on average conduit diameter of ∼21 m in the uppermost 335 m beneath the volcano. The volcano was constructed over a period of at least seven months with cone building occurring only during part of that time, based upon analogy with historical eruptions. Post-eruptive geomorphic evolution varied for the three main surface types that were produced by volcanic activity: (1) scoria cone, (2) low relief surfaces (including lavas) with abundant pyroclastic material, and (3) lavas with little pyroclastic material. The role of these different initial textures must be accounted for in estimating relative ages of volcanic surfaces, and failure to

Eruptive and Geomorphic Processes at the Lathrop Wells Scoria Cone

Energy Technology Data Exchange (ETDEWEB)

G. Valentine; D.J. Krier; F.V. Perry; G. Heiken

2006-08-03

The {approx}80 ka Lathrop Wells volcano (southern Nevada, U.S.A.) preserves evidence for a range of explosive processes and emplacement mechanisms of pyroclastic deposits and lava fields in a small-volume basaltic center. Early cone building by Strombolian bursts was accompanied by development of a fan-like lava field reaching {approx}800 m distance from the cone, built upon a gently sloping surface. Lava flows carried rafts of cone deposits, which provide indirect evidence for cone facies in lieu of direct exposures in the active quarry. Subsequent activity was of a violent Strombolian nature, with many episodes of sustained eruption columns up to a few km in height. These deposited layers of scoria lapilli and ash in different directions depending upon wind direction at the time of a given episode, reaching up to {approx}20 km from the vent, and also produced the bulk of the scoria cone. Lava effusion migrated from south to north around the eastern base of the cone as accumulation of lavas successively reversed the topography at the base of the cone. Late lavas were emplaced during violent Strombolian activity and continued for some time after explosive eruptions had waned. Volumes of the eruptive products are: fallout--0.07 km{sup 3}, scoria cone--0.02 km{sup 3}, and lavas--0.03 km{sup 3}. Shallow-derived xenolith concentrations suggest an upper bound on average conduit diameter of {approx}21 m in the uppermost 335 m beneath the volcano. The volcano was constructed over a period of at least seven months with cone building occurring only during part of that time, based upon analogy with historical eruptions. Post-eruptive geomorphic evolution varied for the three main surface types that were produced by volcanic activity: (1) scoria cone, (2) low relief surfaces (including lavas) with abundant pyroclastic material, and (3) lavas with little pyroclastic material. The role of these different initial textures must be accounted for in estimating relative ages of

Neurosurgeon as innovator: William V. Cone (1897-1959).

Science.gov (United States)

Preul, M C; Stratford, J; Bertrand, G; Feindel, W

1993-10-01

Neurosurgeons are well known for being productive researchers and innovators. Few, however, have possessed the prolific ingenuity of William Cone. In 1934, he and William Penfield were cofounders of the Montreal Neurological Institute where, until 1959, he filled the twin roles of neurosurgeon-in-chief and neuropathologist. Because he did not find writing easy, many of his technical inventions and refinements remained unpublished. His numerous innovations included the extensive use of twist-drill technique for biopsy, drainage for subdural hematoma and cerebral abscess, and ventriculography. In the mid-1940's, he developed power tools driven by nitrogen that led to the modern, universally used air-driven tool systems. He had a special interest in the treatment of spinal dysfunction, for which he invented the Cone-Barton skull-traction tongs along with the Cone spinal operating table. He also devised operative procedures for vertebral fracture-dislocation and craniospinal anomalies. For the maintenance of muscle tone in the paralyzed bladder, he constructed a tidal drainage system. He introduced and popularized ventriculoperitoneal shunting techniques and carried out some of the earliest experimental trails to treat brain infections with sulphonamide and antibiotic drugs. He designed his own set of surgical suction devices, bone rongeurs, and a personal suction "air-conditioning" system for each surgeon. He had a keen early interest in intracranial tumors, and also demonstrated on monkeys how subdural mass lesions caused pupillary dilation and mesial temporal lobe damage due to cerebral compression. His work for the military during World War II on effects of altitude on brain pressure remained classified for many years. The first clipping and excision of an intracranial aneurysm is attributed to Cone. Although Penfield was known as "the Chief," Cone was referred to as "the Boss." His fervent dedication to provide total care to his patients was expressed in round

Comparison of internal target volumes defined on 3-dimensional, 4-dimensonal, and cone-beam CT images of non-small-cell lung cancer

Directory of Open Access Journals (Sweden)

Li F

2016-11-01

Full Text Available Fengxiang Li,1 Jianbin Li,1 Zhifang Ma,1 Yingjie Zhang,1 Jun Xing,1 Huanpeng Qi,1 Dongping Shang21Department of Radiation Oncology, 2Department of Big Bore CT Room, Shandong Cancer Hospital Affiliated to Shandong University, Shandong Academy of Medical Sciences, Jinan, Shandong, People’s Republic of ChinaPurpose: The purpose of this study was to compare the positional and volumetric differences of internal target volumes defined on three-dimensional computed tomography (3DCT, four-dimensional CT (4DCT, and cone-beam CT (CBCT images of non-small-cell lung cancer (NSCLC. Materials and methods: Thirty-one patients with NSCLC sequentially underwent 3DCT and 4DCT simulation scans of the thorax during free breathing. The first CBCT was performed and registered to the planning CT using the bony anatomy registration during radiotherapy. The gross tumor volumes were contoured on the basis of 3DCT, maximum intensity projection (MIP of 4DCT, and CBCT. CTV3D (clinical target volume, internal target volumes, ITVMIP and ITVCBCT, were defined with a 7 mm margin accounting for microscopic disease. ITV10 mm and ITV5 mm were defined on the basis of CTV3D: ITV10 mm with a 5 mm margin in left–right (LR, anterior–posterior (AP directions and 10 mm in cranial–caudal (CC direction; ITV5 mm with an isotropic internal margin (IM of 5 mm. The differences in the position, size, Dice’s similarity coefficient (DSC and inclusion relation of different volumes were evaluated.Results: The median size ratios of ITV10 mm, ITV5 mm, and ITVMIP to ITVCBCT were 2.33, 1.88, and 1.03, respectively, for tumors in the upper lobe and 2.13, 1.76, and 1.1, respectively, for tumors in the middle-lower lobe. The median DSCs of ITV10 mm, ITV5 mm, ITVMIP, and ITVCBCT were 0.6, 0.66, and 0.83 for all patients. The median percentages of ITVCBCT not included in ITV10 mm, ITV5 mm, and ITVMIP were 0.1%, 1.63%, and 15.21%, respectively, while the median percentages of ITV10 mm, ITV5 mm

3D algebraic iterative reconstruction for cone-beam x-ray differential phase-contrast computed tomography.

Science.gov (United States)

Fu, Jian; Hu, Xinhua; Velroyen, Astrid; Bech, Martin; Jiang, Ming; Pfeiffer, Franz

2015-01-01

Due to the potential of compact imaging systems with magnified spatial resolution and contrast, cone-beam x-ray differential phase-contrast computed tomography (DPC-CT) has attracted significant interest. The current proposed FDK reconstruction algorithm with the Hilbert imaginary filter will induce severe cone-beam artifacts when the cone-beam angle becomes large. In this paper, we propose an algebraic iterative reconstruction (AIR) method for cone-beam DPC-CT and report its experiment results. This approach considers the reconstruction process as the optimization of a discrete representation of the object function to satisfy a system of equations that describes the cone-beam DPC-CT imaging modality. Unlike the conventional iterative algorithms for absorption-based CT, it involves the derivative operation to the forward projections of the reconstructed intermediate image to take into account the differential nature of the DPC projections. This method is based on the algebraic reconstruction technique, reconstructs the image ray by ray, and is expected to provide better derivative estimates in iterations. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a mini-focus x-ray tube source. It is shown that the proposed method can reduce the cone-beam artifacts and performs better than FDK under large cone-beam angles. This algorithm is of interest for future cone-beam DPC-CT applications.

Constructing a large variety of Dirac-cone materials in the Bi(1-x)Sb(x) thin film system.

Science.gov (United States)

Tang, Shuang; Dresselhaus, Mildred S

2012-12-21

We theoretically predict that a large variety of Dirac-cone materials can be constructed in Bi(1-x)Sb(x) thin films and we here show how to construct single-, bi- and tri-Dirac-cone materials with various amounts of wave vector anisotropy. These different types of Dirac cones can be of special interest to electronic device design, quantum electrodynamics and other fields.

Determination of CME 3D parameters based on a new full ice-cream cone model

Science.gov (United States)

Na, Hyeonock; Moon, Yong-Jae

2017-08-01

In space weather forecast, it is important to determine three-dimensional properties of CMEs. Using 29 limb CMEs, we examine which cone type is close to a CME three-dimensional structure. We find that most CMEs have near full ice-cream cone structure which is a symmetrical circular cone combined with a hemisphere. We develop a full ice-cream cone model based on a new methodology that the full ice-cream cone consists of many flat cones with different heights and angular widths. By applying this model to 12 SOHO/LASCO halo CMEs, we find that 3D parameters from our method are similar to those from other stereoscopic methods (i.e., a triangulation method and a Graduated Cylindrical Shell model). In addition, we derive CME mean density (ρmean=Mtotal/Vcone) based on the full ice-cream cone structure. For several limb events, we determine CME mass by applying the Solarsoft procedure (e.g., cme_mass.pro) to SOHO/LASCO C3 images. CME volumes are estimated from the full ice-cream cone structure. From the power-law relationship between CME mean density and its height, we estimate CME mean densities at 20 solar radii (Rs). We will compare the CME densities at 20 Rs with their corresponding ICME densities.

Evaluation of elastix-based propagated align algorithm for VOI- and voxel-based analysis of longitudinal (18)F-FDG PET/CT data from patients with non-small cell lung cancer (NSCLC).

Science.gov (United States)

Kerner, Gerald Sma; Fischer, Alexander; Koole, Michel Jb; Pruim, Jan; Groen, Harry Jm

2015-01-01

Deformable image registration allows volume of interest (VOI)- and voxel-based analysis of longitudinal changes in fluorodeoxyglucose (FDG) tumor uptake in patients with non-small cell lung cancer (NSCLC). This study evaluates the performance of the elastix toolbox deformable image registration algorithm for VOI and voxel-wise assessment of longitudinal variations in FDG tumor uptake in NSCLC patients. Evaluation of the elastix toolbox was performed using (18)F-FDG PET/CT at baseline and after 2 cycles of therapy (follow-up) data in advanced NSCLC patients. The elastix toolbox, an integrated part of the IMALYTICS workstation, was used to apply a CT-based non-linear image registration of follow-up PET/CT data using the baseline PET/CT data as reference. Lesion statistics were compared to assess the impact on therapy response assessment. Next, CT-based deformable image registration was performed anew on the deformed follow-up PET/CT data using the original follow-up PET/CT data as reference, yielding a realigned follow-up PET dataset. Performance was evaluated by determining the correlation coefficient between original and realigned follow-up PET datasets. The intra- and extra-thoracic tumors were automatically delineated on the original PET using a 41% of maximum standardized uptake value (SUVmax) adaptive threshold. Equivalence between reference and realigned images was tested (determining 95% range of the difference) and estimating the percentage of voxel values that fell within that range. Thirty-nine patients with 191 tumor lesions were included. In 37/39 and 12/39 patients, respectively, thoracic and non-thoracic lesions were evaluable for response assessment. Using the EORTC/SUVmax-based criteria, 5/37 patients had a discordant response of thoracic, and 2/12 a discordant response of non-thoracic lesions between the reference and the realigned image. FDG uptake values of corresponding tumor voxels in the original and realigned reference PET correlated well (R

Partial volume effect estimation and correction in the aortic vascular wall in PET imaging

International Nuclear Information System (INIS)

Burg, S; Le Guludec, D; Dupas, A; Stute, S; Dieudonné, A; Huet, P; Buvat, I

2013-01-01

We evaluated the impact of partial volume effect (PVE) in the assessment of arterial diseases with 18 FDG PET. An anthropomorphic digital phantom enabling the modeling of aorta related diseases like atherosclerosis and arteritis was used. Based on this phantom, we performed GATE Monte Carlo simulations to produce realistic PET images with a known organ segmentation and ground truth activity values. Images corresponding to 15 different activity-concentration ratios between the aortic wall and the blood and to 7 different wall thicknesses were generated. Using the PET images, we compared the theoretical wall-to-blood activity-concentration ratios (WBRs) with the measured WBRs obtained with five measurement methods: (1) measurement made by a physician (Expert), (2) automated measurement supposed to mimic the physician measurements (Max), (3) simple correction based on a recovery coefficient (Max-RC), (4) measurement based on an ideal VOI segmentation (Mean-VOI) and (5) measurement corrected for PVE using an ideal geometric transfer matrix (GTM) method. We found that Mean-VOI WBRs values were strongly affected by PVE. WBRs obtained by the physician measurement, by the Max method and by the Max-RC method were more accurate than WBRs obtained with the Mean-VOI approach. However Expert, Max and Max-RC WBRs strongly depended on the wall thickness. Only the GTM corrected WBRs did not depend on the wall thickness. Using the GTM method, we obtained more reproducible ratio values that could be compared across wall thickness. Yet, the feasibility of the implementation of a GTM-like method on real data remains to be studied. (paper)

High-resolution-cone beam tomography analysis of bone microarchitecture in patients with acromegaly and radiological vertebral fractures.

Science.gov (United States)

Maffezzoni, Filippo; Maddalo, Michele; Frara, Stefano; Mezzone, Monica; Zorza, Ivan; Baruffaldi, Fabio; Doglietto, Francesco; Mazziotti, Gherardo; Maroldi, Roberto; Giustina, Andrea

2016-11-01

Vertebral fractures are an emerging complication of acromegaly but their prediction is still difficult occurring even in patients with normal bone mineral density. In this study we evaluated the ability of high-resolution cone-beam computed tomography to provide information on skeletal abnormalities associated with vertebral fractures in acromegaly. 40 patients (24 females, 16 males; median age 57 years, range 25-72) and 21 healthy volunteers (10 females, 11 males; median age 60 years, range: 25-68) were evaluated for trabecular (bone volume/trabecular volume ratio, mean trabecular separation, and mean trabecular thickness) and cortical (thickness and porosity) parameters at distal radius using a high-resolution cone-beam computed tomography system. All acromegaly patients were evaluated for morphometric vertebral fractures and for mineral bone density by dual-energy X-ray absorptiometry at lumbar spine, total hip, femoral neck, and distal radius. Acromegaly patients with vertebral fractures (15 cases) had significantly (p acromegaly patients did not have significant differences in bone density at either skeletal site. Patients with acromegaly showed lower bone volume/trabecular volume ratio (p = 0.003) and mean trabecular thickness (p acromegaly. High-resolution cone-beam computed tomography at the distal radius may be useful to evaluate and predict the effects of acromegaly on bone microstructure.

Les kystes hydatiques du foie rompus dans les voies biliaires: à propos de 120 cas

Science.gov (United States)

Moujahid, Mountassir; Tajdine, Mohamed Tarik

2011-01-01

Etude rétrospective rapportant une série de kystes hydatiques rompus dans les voies biliaires colligés dans le service de chirurgie de l'hôpital militaire Avicenne à Marrakech. Entre 1990 à 2008, sur 536 kystes hydatiques du foie opérés dans le service, 120 étaient compliqués de rupture dans les voies biliaires soit 22,38%. Il y avait 82hommes et 38 femmes. L’âge moyen était de 35 ans avec des extrêmes allant de 10 à 60 ans. La clinique était dominée par la crise d'angiocholite ou une douleur du flanc droit. L'ictère était isolé dans huit cas. La fistule biliokystique était latente dans plus de 50% des cas. Le traitement a consisté en une résection du dôme saillant dans103cas (85,84%), une périkystectomie chez 11 malades (9,16%) et une lobectomie gauche dans six cas (5%). Le traitement de la fistule bilio kystique a consisté en une suture chez 36malades et un drainage bipolaire dans 25 cas, La déconnexion kysto-biliaire ou cholédocotomie trans hépatico kystique selon Perdomo était pratiquée dans 49cas et une anastomose bilio-digestive cholédoco-duodénale dans 10 cas. La durée moyenne d'hospitalisation était de 20jours. Nous déplorons deux décès par choc septique et un troisième par encéphalopathie secondaire à une cirrhose biliaire. La morbidité était représentée par huit abcès sous phrénique, douze fistules biliaires prolongées et deux occlusions intestinales. Les kystes hydatiques rompus dans les voies biliaires représentent la complication la plus grave de cette pathologie bénigne. Le traitement repose sur des méthodes radicales qui sont d'une efficacité reconnue, mais de réalisation dangereuse et les méthodes conservatrices, en particulier la déconnexion kysto-biliaire qui est une méthode simple et qui donne de bons résultats à court et à long terme. PMID:22384289

Individual patient dosimetry using quantitative SPECT imaging

International Nuclear Information System (INIS)

Gonzalez, J.; Oliva, J.; Baum, R.; Fisher, S.

2002-01-01

An approach is described to provide individual patient dosimetry for routine clinical use. Accurate quantitative SPECT imaging was achieved using appropriate methods. The volume of interest (VOI) was defined semi-automatically using a fixed threshold value obtained from phantom studies. The calibration factor to convert the voxel counts from SPECT images into activity values was determine from calibrated point source using the same threshold value as in phantom studies. From selected radionuclide the dose within and outside a sphere of voxel dimension at different distances was computed through dose point-kernels to obtain a discrete absorbed dose kernel representation around the volume source with uniform activity distribution. The spatial activity distribution from SPECT imaging was convolved with this kernel representation using the discrete Fourier transform method to yield three-dimensional absorbed dose rate distribution. The accuracy of dose rates calculation was validated by software phantoms. The absorbed dose was determined by integration of the dose rate distribution for each volume of interest (VOI). Parameters for treatment optimization such as dose rate volume histograms and dose rate statistic are provided. A patient example was used to illustrate our dosimetric calculations

The effect of using an inverted master cone in a lateral compaction technique on the density of the gutta-percha fill.

Science.gov (United States)

Wu, Min-Kai; de Groot, Sjoerd D; van der Sluis, Luc W M; Wesselink, Paul R

2003-09-01

We sought to measure and calculate the percentage of the gutta-percha-filled area in the apical root canal after the use of a standardized or inverted master cone in cold lateral compaction.Study design Two groups of extracted mandibular premolars with a single canal were instrumented with instruments of the same size; furthermore, they were obturated with laterally compacted gutta-percha cones with AH26 used as a sealer. In the first group, a standardized master cone was used with its narrow end in an apical position, whereas in the other group, an inverted master cone was used with its wide end in an apical position. The 2 master cones had the same apical diameter and fit in the apical canal. After lateral compaction, horizontal sections were cut at a level 3 and 5 mm from the apex of each filled tooth. Photographs of the sections were taken by using a microscope equipped with a digital camera; the photos were then scanned as tagged-image file format images. The cross-sectional area of the canal and the gutta-percha were measured by using an image-analysis program. The percentage of gutta-percha-filled area was calculated. At both levels, the inverted master cone produced a significantly higher percentage, statistically, of gutta-percha-filled area than did the standardized master cone (P =.001 at 3 mm; P =.012 at 5 mm). The use of an inverted master cone in cold lateral compaction may facilitate the apical placement of accessory cones, significantly increasing the volume of gutta-percha while reducing the volume of sealer in the apical root canal.

Case histories of roller cone core bit application in crystalline rock

International Nuclear Information System (INIS)

Dahlem, J.S.

1988-01-01

The increased interest in deep crystalline rock drilling projects has resulted in a requirement for premium coring bits which are effective in such a harsh and abrasive environment. Hard formation roller cone insert bits have traditionally and constantly performed well in crystalline rock. As a result, the application of state of the art roller cone rock bit technology to the design and development of core bits has made crystalline coring projects more viable than ever before. This paper follows the development of roller cone core bits by examining their use on project such as HDR (Hot Dry Rock, Los Alamos); NAGRA (Nuclear Waste Disposal Wells in Switzerland); Camborne School of Mines Geothermal Project in Cornwall, UK; Deep Gas Project in Sweden; and the KTB Deep Drilling Project in West Germany

Short-term myeloid growth factor mediated expansion of bone marrow haemopoiesis studied by localized magnetic resonance proton spectroscopy

DEFF Research Database (Denmark)

Jensen, K E; Hansen, P B; Larsen, V A

1994-01-01

(day 0), day 5 and day 12. Spectroscopic examinations were performed with the stimulated echo acquisition mode (STEAM) method on a 1.5 T clinical whole-body imaging unit. A cubic volume of interest (VOI) was selected in the bone marrow of the left iliac bone. The patients responded with a rise in blood...

Identification d’une nouvelle molécule d’intérêt chez le cheval atteint d’obstruction récurrente des voies respiratoires: La Pentraxine 3

OpenAIRE

Ramery, Eve

2010-01-01

L’ORVR ou obstruction récurrente des voies respiratoires (ORVR) est la cause la plus fréquente de maladie pulmonaire chronique chez le cheval adulte. La maladie se caractérise par une hyperréactivité bronchique, une production excessive de mucus et une inflammation neutrophilique pulmonaire qui ont pour effet de réduire la compliance dynamique du poumon et d’augmenter la résistance des voies respiratoires au débit aérien. Alors que la maladie est une entité documentée dans la littérature depu...

Metabolic connectivity by interregional correlation analysis using statistical parametric mapping (SPM) and FDG brain PET; methodological development and patterns of metabolic connectivity in adults

International Nuclear Information System (INIS)

Lee, Dong Soo; Oh, Jungsu S.; Lee, Jae Sung; Lee, Myung Chul; Kang, Hyejin; Kim, Heejung; Park, Hyojin

2008-01-01

Regionally connected areas of the resting brain can be detected by fluorodeoxyglucose-positron emission tomography (FDG-PET). Voxel-wise metabolic connectivity was examined, and normative data were established by performing interregional correlation analysis on statistical parametric mapping of FDG-PET data. Characteristics of seed volumes of interest (VOIs) as functional brain units were represented by their locations, sizes, and the independent methods of their determination. Seed brain areas were identified as population-based gyral VOIs (n=70) or as population-based cytoarchitectonic Brodmann areas (BA; n=28). FDG uptakes in these areas were used as independent variables in a general linear model to search for voxels correlated with average seed VOI counts. Positive correlations were searched in entire brain areas. In normal adults, one third of gyral VOIs yielded correlations that were confined to themselves, but in the others, correlated voxels extended to adjacent areas and/or contralateral homologous regions. In tens of these latter areas with extensive connectivity, correlated voxels were found across midline, and asymmetry was observed in the patterns of connectivity of left and right homologous seed VOIs. Most of the available BAs yielded correlations reaching contralateral homologous regions and/or neighboring areas. Extents of metabolic connectivity were not found to be related to seed VOI size or to the methods used to define seed VOIs. These findings indicate that patterns of metabolic connectivity of functional brain units depend on their regional locations. We propose that interregional correlation analysis of FDG-PET data offers a means of examining voxel-wise regional metabolic connectivity of the resting human brain. (orig.)

Metabolic connectivity by interregional correlation analysis using statistical parametric mapping (SPM) and FDG brain PET; methodological development and patterns of metabolic connectivity in adults

Energy Technology Data Exchange (ETDEWEB)

Lee, Dong Soo; Oh, Jungsu S.; Lee, Jae Sung; Lee, Myung Chul [Seoul National University, College of Medicine, Department of Nuclear Medicine, Jongno-gu, Seoul (Korea); Kang, Hyejin [Seoul National University, College of Medicine, Department of Nuclear Medicine, Jongno-gu, Seoul (Korea); Seoul National University, Programs in Brain and Neuroscience, Seoul (Korea); Kim, Heejung; Park, Hyojin [Seoul National University, College of Medicine, Department of Nuclear Medicine, Jongno-gu, Seoul (Korea); Seoul National University, Interdisciplinary Program in Cognitive Science, Seoul (Korea)

2008-09-15

Regionally connected areas of the resting brain can be detected by fluorodeoxyglucose-positron emission tomography (FDG-PET). Voxel-wise metabolic connectivity was examined, and normative data were established by performing interregional correlation analysis on statistical parametric mapping of FDG-PET data. Characteristics of seed volumes of interest (VOIs) as functional brain units were represented by their locations, sizes, and the independent methods of their determination. Seed brain areas were identified as population-based gyral VOIs (n=70) or as population-based cytoarchitectonic Brodmann areas (BA; n=28). FDG uptakes in these areas were used as independent variables in a general linear model to search for voxels correlated with average seed VOI counts. Positive correlations were searched in entire brain areas. In normal adults, one third of gyral VOIs yielded correlations that were confined to themselves, but in the others, correlated voxels extended to adjacent areas and/or contralateral homologous regions. In tens of these latter areas with extensive connectivity, correlated voxels were found across midline, and asymmetry was observed in the patterns of connectivity of left and right homologous seed VOIs. Most of the available BAs yielded correlations reaching contralateral homologous regions and/or neighboring areas. Extents of metabolic connectivity were not found to be related to seed VOI size or to the methods used to define seed VOIs. These findings indicate that patterns of metabolic connectivity of functional brain units depend on their regional locations. We propose that interregional correlation analysis of FDG-PET data offers a means of examining voxel-wise regional metabolic connectivity of the resting human brain. (orig.)

Realization of fluence field modulated CT on a clinical TomoTherapy megavoltage CT system

International Nuclear Information System (INIS)

Szczykutowicz, Timothy P; Hermus, James; Geurts, Mark; Smilowitz, Jennifer

2015-01-01

The multi-leaf collimator (MLC) assembly present on TomoTherapy (Accuray, Madison WI) radiation therapy (RT) and mega voltage CT machines is well suited to perform fluence field modulated CT (FFMCT). In addition, there is a demand in the RT environment for FFMCT imaging techniques, specifically volume of interest (VOI) imaging.A clinical TomoTherapy machine was programmed to perform VOI. Four different size ROIs were placed at varying distances from isocenter. Projections intersecting the VOI received ‘full dose’ while those not intersecting the VOI received 30% of the dose (i.e. the incident fluence for non VOI projections was 30% of the incident fluence for projections intersecting the VOI). Additional scans without fluence field modulation were acquired at ‘full’ and 30% dose. The noise (pixel standard deviation) and mean CT number were measured inside the VOI region and compared between the three scans. Dose maps were generated using a dedicated TomoTherapy treatment planning dose calculator.The VOI-FFMCT technique produced an image noise 1.05, 1.00, 1.03, and 1.05 times higher than the ‘full dose’ scan for ROI sizes of 10 cm, 13 cm, 10 cm, and 6 cm respectively within the VOI region. The VOI-FFMCT technique required a total imaging dose equal to 0.61, 0.69, 0.60, and 0.50 times the ‘full dose’ acquisition dose for ROI sizes of 10 cm, 13 cm, 10 cm, and 6 cm respectively within the VOI region.Noise levels can be almost unchanged within clinically relevant VOIs sizes for RT applications while the integral imaging dose to the patient can be decreased, and/or the image quality in RT can be dramatically increased with no change in dose relative to non-FFMCT RT imaging. The ability to shift dose away from regions unimportant for clinical evaluation in order to improve image quality or reduce imaging dose has been demonstrated. This paper demonstrates that FFMCT can be performed using the MLC on a clinical TomoTherapy machine for the

Combined 18F-Fluciclovine PET/MRI Shows Potential for Detection and Characterization of High-Risk Prostate Cancer.

Science.gov (United States)

Elschot, Mattijs; Selnæs, Kirsten M; Sandsmark, Elise; Krüger-Stokke, Brage; Størkersen, Øystein; Giskeødegård, Guro F; Tessem, May-Britt; Moestue, Siver A; Bertilsson, Helena; Bathen, Tone F

2018-05-01

The objective of this study was to investigate whether quantitative imaging features derived from combined 18 F-fluciclovine PET/multiparametric MRI show potential for detection and characterization of primary prostate cancer. Methods: Twenty-eight patients diagnosed with high-risk prostate cancer underwent simultaneous 18 F-fluciclovine PET/MRI before radical prostatectomy. Volumes of interest (VOIs) for prostate tumors, benign prostatic hyperplasia (BPH) nodules, prostatitis, and healthy tissue were delineated on T2-weighted images, using histology as a reference. Tumor VOIs were marked as high-grade (≥Gleason grade group 3) or not. MRI and PET features were extracted on the voxel and VOI levels. Partial least-squared discriminant analysis (PLS-DA) with double leave-one-patient-out cross-validation was performed to distinguish tumors from benign tissue (BPH, prostatitis, or healthy tissue) and high-grade tumors from other tissue (low-grade tumors or benign tissue). The performance levels of PET, MRI, and combined PET/MRI features were compared using the area under the receiver-operating-characteristic curve (AUC). Results: Voxel and VOI features were extracted from 40 tumor VOIs (26 high-grade), 36 BPH VOIs, 6 prostatitis VOIs, and 37 healthy-tissue VOIs. PET/MRI performed better than MRI and PET alone for distinguishing tumors from benign tissue (AUCs of 87%, 81%, and 83%, respectively, at the voxel level and 96%, 93%, and 93%, respectively, at the VOI level) and high-grade tumors from other tissue (AUCs of 85%, 79%, and 81%, respectively, at the voxel level and 93%, 93%, and 91%, respectively, at the VOI level). T2-weighted MRI, diffusion-weighted MRI, and PET features were the most important for classification. Conclusion: Combined 18 F-fluciclovine PET/multiparametric MRI shows potential for improving detection and characterization of high-risk prostate cancer, in comparison to MRI and PET alone. © 2018 by the Society of Nuclear Medicine and Molecular

Direct numerical simulations of mack-mode damping on porous coated cones

Science.gov (United States)

Lüdeke, H.; Wartemann, V.

2013-06-01

The flow field over a 3 degree blunt cone is investigated with respect to a hypersonic stability analysis of the boundary-layer flow at Mach 6 with porous as well as smooth walls by comparing local direct numerical simulations (DNS) and linear stability theory (LST) data. The original boundary-layer profile is generated by a finite volume solver, using shock capturing techniques to generate an axisymmetric flow field. Local boundary-layer profiles are extracted from this flow field and hypersonic Mack-modes are superimposed for cone-walls with and without a porous surface used as a passive transition-reduction device. Special care is taken of curvature effects of the wall on the mode development over smooth and porous walls.

Foveal cone spacing and cone photopigment density difference: objective measurements in the same subjects.

Science.gov (United States)

Marcos, S; Tornow, R P; Elsner, A E; Navarro, R

1997-07-01

Foveal cone spacing was measured in vivo using an objective technique: ocular speckle interferometry. Cone packing density was computed from cone spacing data. Foveal cone photopigment density difference was measured in the same subjects using retinal densitometry with a scanning laser ophthalmoscope. Both the cone packing density and cone photopigment density difference decreased sharply with increasing retinal eccentricity. From the comparison of both sets of measurements, the computed amounts of photopigment per cone increased slightly with increasing retinal eccentricity. Consistent with previous results, decreases in cone outer segment length are over-compensated by an increase in the outer segment area, at least in retinal eccentricities up to 1 deg.

Image reconstruction in circular cone-beam computed tomography by constrained, total-variation minimization

International Nuclear Information System (INIS)

Sidky, Emil Y; Pan Xiaochuan

2008-01-01

An iterative algorithm, based on recent work in compressive sensing, is developed for volume image reconstruction from a circular cone-beam scan. The algorithm minimizes the total variation (TV) of the image subject to the constraint that the estimated projection data is within a specified tolerance of the available data and that the values of the volume image are non-negative. The constraints are enforced by the use of projection onto convex sets (POCS) and the TV objective is minimized by steepest descent with an adaptive step-size. The algorithm is referred to as adaptive-steepest-descent-POCS (ASD-POCS). It appears to be robust against cone-beam artifacts, and may be particularly useful when the angular range is limited or when the angular sampling rate is low. The ASD-POCS algorithm is tested with the Defrise disk and jaw computerized phantoms. Some comparisons are performed with the POCS and expectation-maximization (EM) algorithms. Although the algorithm is presented in the context of circular cone-beam image reconstruction, it can also be applied to scanning geometries involving other x-ray source trajectories

Comparison study of portable bladder scanner versus cone-beam CT scan for measuring bladder volumes in post-prostatectomy patients undergoing radiotherapy.

Science.gov (United States)

Ung, K A; White, R; Mathlum, M; Mak-Hau, V; Lynch, R

2014-01-01

In post-prostatectomy radiotherapy to the prostatic bed, consistent bladder volume is essential to maintain the position of treatment target volume. We assessed the differences between bladder volume readings from a portable bladder scanner (BS-V) and those obtained from planning CT (CT-V) or cone-beam CT (CBCT-V). Interfraction bladder volume variation was also determined. BS-V was recorded before and after planning CT or CBCT. The percentage differences between the readings using the two imaging modalities, standard deviations and 95% confidence intervals were determined. Data were analysed for the whole patient cohort and separately for the older BladderScan™ BVI3000 and newer BVI9400 model. Interfraction bladder volume variation was determined from the percentage difference between the CT-V and CBCT-V. Treatment duration, incorporating the time needed for BS and CBCT, was recorded. Fourteen patients were enrolled, producing 133 data sets for analysis. BS-V was taken using the BVI9400 in four patients (43 data sets). The mean BS-V was 253.2 mL, and the mean CT-V or CBCT-V was 199 cm(3). The mean percentage difference between the two modalities was 19.7% (SD 42.2; 95%CI 12.4 to 26.9). The BVI9400 model produced more consistent readings, with a mean percentage difference of -6.2% (SD 27.8; 95% CI -14.7 to -2.4%). The mean percentage difference between CT-V and CBCT-V was 31.3% (range -48% to 199.4%). Treatment duration from time of first BS reading to CBCT was, on average, 12 min (range 6-27). The BS produces bladder volume readings of an average 19.7% difference from CT-V or CBCT-V and can potentially be used to screen for large interfraction bladder volume variations in radiotherapy to prostatic bed. The observed interfraction bladder volume variation suggests the need to improve bladder volume consistency. Incorporating the BS into practice is feasible. © 2014 The Royal Australian and New Zealand College of Radiologists.

Light-cone quantization of quantum chromodynamics

International Nuclear Information System (INIS)

Brodsky, S.J.; Pauli, H.C.

1991-06-01

We discuss the light-cone quantization of gauge theories from two perspectives: as a calculational tool for representing hadrons as QCD bound-states of relativistic quarks and gluons, and also as a novel method for simulating quantum field theory on a computer. The light-cone Fock state expansion of wavefunctions at fixed light cone time provides a precise definition of the parton model and a general calculus for hadronic matrix elements. We present several new applications of light-cone Fock methods, including calculations of exclusive weak decays of heavy hadrons, and intrinsic heavy-quark contributions to structure functions. A general nonperturbative method for numerically solving quantum field theories, ''discretized light-cone quantization,'' is outlined and applied to several gauge theories, including QCD in one space and one time dimension, and quantum electrodynamics in physical space-time at large coupling strength. The DLCQ method is invariant under the large class of light-cone Lorentz transformations, and it can be formulated such at ultraviolet regularization is independent of the momentum space discretization. Both the bound-state spectrum and the corresponding relativistic light-cone wavefunctions can be obtained by matrix diagonalization and related techniques. We also discuss the construction of the light-cone Fock basis, the structure of the light-cone vacuum, and outline the renormalization techniques required for solving gauge theories within the light-cone Hamiltonian formalism

Light-cone quantization of quantum chromodynamics

Energy Technology Data Exchange (ETDEWEB)

Brodsky, S.J. (Stanford Linear Accelerator Center, Menlo Park, CA (USA)); Pauli, H.C. (Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany, F.R.))

1991-06-01

We discuss the light-cone quantization of gauge theories from two perspectives: as a calculational tool for representing hadrons as QCD bound-states of relativistic quarks and gluons, and also as a novel method for simulating quantum field theory on a computer. The light-cone Fock state expansion of wavefunctions at fixed light cone time provides a precise definition of the parton model and a general calculus for hadronic matrix elements. We present several new applications of light-cone Fock methods, including calculations of exclusive weak decays of heavy hadrons, and intrinsic heavy-quark contributions to structure functions. A general nonperturbative method for numerically solving quantum field theories, discretized light-cone quantization,'' is outlined and applied to several gauge theories, including QCD in one space and one time dimension, and quantum electrodynamics in physical space-time at large coupling strength. The DLCQ method is invariant under the large class of light-cone Lorentz transformations, and it can be formulated such at ultraviolet regularization is independent of the momentum space discretization. Both the bound-state spectrum and the corresponding relativistic light-cone wavefunctions can be obtained by matrix diagonalization and related techniques. We also discuss the construction of the light-cone Fock basis, the structure of the light-cone vacuum, and outline the renormalization techniques required for solving gauge theories within the light-cone Hamiltonian formalism.

Comparison study of portable bladder scanner versus cone-beam CT scan for measuring bladder volumes in post-prostatectomy patients undergoing radiotherapy

International Nuclear Information System (INIS)

Ung, K.A.; White, R.; Mathlum, M.; Lynch, R.; Mak-Hau, V.

2014-01-01

In post-prostatectomy radiotherapy to the prostatic bed, consistent bladder volume is essential to maintain the position of treatment target volume. We assessed the differences between bladder volume readings from a portable bladder scanner (BS-V) and those obtained from planning CT (CT-V) or cone-beam CT (CBCT-V). Interfraction bladder volume variation was also determined. BS-V was recorded before and after planning CT or CBCT. The percentage differences between the readings using the two imaging modalities, standard deviations and 95% confidence intervals were determined. Data were analysed for the whole patient cohort and separately for the older BladderScan™ BVI3000 and newer BVI9400 model. Interfraction bladder volume variation was determined from the percentage difference between the CT-V and CBCT-V. Treatment duration, incorporating the time needed for BS and CBCT, was recorded. Fourteen patients were enrolled, producing 133 data sets for analysis. BS-V was taken using the BVI9400 in four patients (43 data sets). The mean BS-V was 253.2mL, and the mean CT-V or CBCT-V was 199cm3. The mean percentage difference between the two modalities was 19.7% (SD 42.2; 95%CI 12.4 to 26.9). The BVI9400 model produced more consistent readings, with a mean percentage difference of −6.2% (SD 27.8; 95% CI −14.7 to −2.4%). The mean percentage difference between CT-V and CBCT-V was 31.3% (range −48% to 199.4%). Treatment duration from time of first BS reading to CBCT was, on average, 12min (range 6–27). The BS produces bladder volume readings of an average 19.7% difference from CT-V or CBCT-V and can potentially be used to screen for large interfraction bladder volume variations in radiotherapy to prostatic bed. The observed interfraction bladder volume variation suggests the need to improve bladder volume consistency. Incorporating the BS into practice is feasible.

The holographic entropy cone

Energy Technology Data Exchange (ETDEWEB)

Bao, Ning [Institute for Quantum Information and Matter, California Institute of Technology,Pasadena, CA 91125 (United States); Walter Burke Institute for Theoretical Physics, California Institute of Technology,452-48, Pasadena, CA 91125 (United States); Nezami, Sepehr [Stanford Institute for Theoretical Physics, Stanford University,Stanford, CA 94305 (United States); Ooguri, Hirosi [Walter Burke Institute for Theoretical Physics, California Institute of Technology,452-48, Pasadena, CA 91125 (United States); Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo,Kashiwa 277-8583 (Japan); Stoica, Bogdan [Walter Burke Institute for Theoretical Physics, California Institute of Technology,452-48, Pasadena, CA 91125 (United States); Sully, James [Theory Group, SLAC National Accelerator Laboratory, Stanford University,Menlo Park, CA 94025 (United States); Walter, Michael [Stanford Institute for Theoretical Physics, Stanford University,Stanford, CA 94305 (United States)

2015-09-21

We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phase space of Ryu-Takayanagi entropies, defining the holographic entropy cone. We characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. We find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. To establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in Riemannian geometry and graph theory.

The holographic entropy cone

International Nuclear Information System (INIS)

Bao, Ning; Nezami, Sepehr; Ooguri, Hirosi; Stoica, Bogdan; Sully, James; Walter, Michael

2015-01-01

We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phase space of Ryu-Takayanagi entropies, defining the holographic entropy cone. We characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. We find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. To establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in Riemannian geometry and graph theory.

Applying the dynamic cone penetrometer (DCP) design method to low volume roads

CSIR Research Space (South Africa)

Paige-Green, P

2011-07-01

Full Text Available The Dynamic Cone Penetrometer (DCP) has been in use since the 1950s for various applications in pavement investigation. During the 1980s, Kleyn and Van Zyl described a method for upgrading unsealed roads to light sealed road standard based...

Quotient normed cones

Indian Academy of Sciences (India)

general setting of the space CL(X, Y ) of all continuous linear mappings from a normed cone (X, p) to a normed cone (Y, q), extending several well-known results related to open continuous linear mappings between normed linear spaces. Keywords. Normed cone; extended quasi-metric; continuous linear mapping; bicom-.

Light Cone 2016 : Challenges for Theory and Experiment in Hadron and Nuclear Physics on the Light Front

CERN Document Server

Pena, Teresa

2018-01-01

The Light-Cone 2016 conference, held in September 2016 in Lisbon, Portugal, belongs to a series of yearly Light-Cone meetings that started in 1991. As its predecessors, this conference was guided by the objectives defined by the International Light Cone Advisory Committee, namely to “advance research in quantum field theory, particularly light-cone quantization methods applicable to the solution of physical problems”. This volume compiles selected papers presented at the conference by experts from all over the world, which describe recent progress in theoretical research, and new results and planned activities at leading experimental facilities, with special emphasis on the physics of hadrons and nuclei.

A rotating and warping projector/backprojector for fan-beam and cone-beam iterative algorithm

International Nuclear Information System (INIS)

Zeng, G.L.; Hsieh, Y.L.; Gullberg, G.T.

1994-01-01

A rotating-and-warping projector/backprojector is proposed for iterative algorithms used to reconstruct fan-beam and cone-beam single photon emission computed tomography (SPECT) data. The development of a new projector/backprojector for implementing attenuation, geometric point response, and scatter models is motivated by the need to reduce the computation time yet to preserve the fidelity of the corrected reconstruction. At each projection angle, the projector/backprojector first rotates the image volume so that the pixelized cube remains parallel to the detector, and then warps the image volume so that the fan-beam and cone-beam rays are converted into parallel rays. In the authors implementation, these two steps are combined so that the interpolation of voxel values are performed only once. The projection operation is achieved by a simple weighted summation, and the backprojection operation is achieved by copying weighted projection array values to the image volume. An advantage of this projector/backprojector is that the system point response function can be deconvolved via the Fast Fourier Transform using the shift-invariant property of the point response when the voxel-to-detector distance is constant. The fan-beam and cone-beam rotating-and-warping projector/backprojector is applied to SPECT data showing improved resolution

SU-F-J-183: Interior Region-Of-Interest Tomography by Using Inverse Geometry System

Energy Technology Data Exchange (ETDEWEB)

Kim, K; Kim, D; Kang, S; Kim, T; Shin, D; Cho, M; Noh, Y; Suh, T [Department of Biomedical Engineering and Research Institute of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seoul (Korea, Republic of)

2016-06-15

Purpose: The inverse geometry computed tomography (IGCT) composed of multiple source and small size detector has several merits such as reduction of scatter effect and large volumetric imaging within one rotation without cone-beam artifact, compared to conventional cone-beam computed tomography (CBCT). By using this multi-source characteristics, we intend to present a selective and multiple interior region-of-interest (ROI) imaging method by using a designed source on-off sequence of IGCT. Methods: All of the IGCT sources are operated one by one sequentially, and each projection in the shape of narrow cone-beam covers its own partial volume of full field of view (FOV) determined from system geometry. Thus, through controlling multi source operation, limited irradiation within ROI is possible and selective radon space data for ROI imaging can be acquired without additional X-ray filtration. With this feature, we designed a source on-off sequence for multi ROI-IGCT imaging, and projections of ROI-IGCT were generated by using the on-off sequence. Multi ROI-IGCT images were reconstructed by using filtered back-projection algorithm. All these imaging process of our study has been performed by utilizing digital phantom and patient CT data. ROI-IGCT images of the phantom were compared to CBCT image and the phantom data for the image quality evaluation. Results: Image quality of ROI-IGCT was comparable to that of CBCT. However, the distal axial-plane from the FOV center, large cone-angle region, ROI-IGCT showed uniform image quality without significant cone-beam artifact contrary to CBCT. Conclusion: ROI-IGCT showed comparable image quality and has the capability to provide multi ROI image within a rotation. Projection of ROI-IGCT is performed by selective irradiation, hence unnecessary imaging dose to non-interest region can be reduced. In this regard, it seems to be useful for diagnostic or image guidance purpose in radiotherapy such as low dose target localization and

SU-F-J-183: Interior Region-Of-Interest Tomography by Using Inverse Geometry System

International Nuclear Information System (INIS)

Kim, K; Kim, D; Kang, S; Kim, T; Shin, D; Cho, M; Noh, Y; Suh, T

2016-01-01

Purpose: The inverse geometry computed tomography (IGCT) composed of multiple source and small size detector has several merits such as reduction of scatter effect and large volumetric imaging within one rotation without cone-beam artifact, compared to conventional cone-beam computed tomography (CBCT). By using this multi-source characteristics, we intend to present a selective and multiple interior region-of-interest (ROI) imaging method by using a designed source on-off sequence of IGCT. Methods: All of the IGCT sources are operated one by one sequentially, and each projection in the shape of narrow cone-beam covers its own partial volume of full field of view (FOV) determined from system geometry. Thus, through controlling multi source operation, limited irradiation within ROI is possible and selective radon space data for ROI imaging can be acquired without additional X-ray filtration. With this feature, we designed a source on-off sequence for multi ROI-IGCT imaging, and projections of ROI-IGCT were generated by using the on-off sequence. Multi ROI-IGCT images were reconstructed by using filtered back-projection algorithm. All these imaging process of our study has been performed by utilizing digital phantom and patient CT data. ROI-IGCT images of the phantom were compared to CBCT image and the phantom data for the image quality evaluation. Results: Image quality of ROI-IGCT was comparable to that of CBCT. However, the distal axial-plane from the FOV center, large cone-angle region, ROI-IGCT showed uniform image quality without significant cone-beam artifact contrary to CBCT. Conclusion: ROI-IGCT showed comparable image quality and has the capability to provide multi ROI image within a rotation. Projection of ROI-IGCT is performed by selective irradiation, hence unnecessary imaging dose to non-interest region can be reduced. In this regard, it seems to be useful for diagnostic or image guidance purpose in radiotherapy such as low dose target localization and

Quantification of Tumor Vessels in Glioblastoma Patients Using Time-of-Flight Angiography at 7 Tesla: A Feasibility Study

Science.gov (United States)

Radbruch, Alexander; Eidel, Oliver; Wiestler, Benedikt; Paech, Daniel; Burth, Sina; Kickingereder, Philipp; Nowosielski, Martha; Bäumer, Philipp; Wick, Wolfgang; Schlemmer, Heinz-Peter; Bendszus, Martin; Ladd, Mark; Nagel, Armin Michael; Heiland, Sabine

2014-01-01

Purpose To analyze if tumor vessels can be visualized, segmented and quantified in glioblastoma patients with time of flight (ToF) angiography at 7 Tesla and multiscale vessel enhancement filtering. Materials and Methods Twelve patients with newly diagnosed glioblastoma were examined with ToF angiography (TR = 15 ms, TE = 4.8 ms, flip angle = 15°, FOV = 160×210 mm2, voxel size: 0.31×0.31×0.40 mm3) on a whole-body 7 T MR system. A volume of interest (VOI) was placed within the border of the contrast enhancing part on T1-weighted images of the glioblastoma and a reference VOI was placed in the non-affected contralateral white matter. Automated segmentation and quantification of vessels within the two VOIs was achieved using multiscale vessel enhancement filtering in ImageJ. Results Tumor vessels were clearly visible in all patients. When comparing tumor and the reference VOI, total vessel surface (45.3±13.9 mm2 vs. 29.0±21.0 mm2 (pTesla MRI enables characterization and quantification of the internal vascular morphology of glioblastoma and may be used for the evaluation of therapy response within future studies. PMID:25415327

Gastroenteropancreatic Neuroendocrine Tumors: Standardizing Therapy Monitoring with 68Ga-DOTATOC PET/CT Using the Example of Somatostatin Receptor Radionuclide Therapy

Directory of Open Access Journals (Sweden)

Wolfgang Luboldt

2010-11-01

Full Text Available The purpose of this study was to standardize therapy monitoring of hepatic metastases from gastroenteropancreatic neuroendocrine tumors (GEP-NETs during the course of somatostatin receptor radionuclide therapy (SRRT. In 21 consecutive patients with nonresectable hepatic metastases of GEP-NETs, chromogranin A (CgA and 68Ga-DOTATOC PET/CT were compared before and after the last SRRT. On 68Ga-DOTATOC PET/CT, the maximum standard uptake values (SUVmax of normal liver and hepatic metastases were calculated. In addition, the volumes of hepatic metastases (volume of interest [VOI] were measured using four cut-offs to separate normal liver tissue from metastases (SUVmax of the normal liver plus 10% [VOIliver+10%], 20% [VOIliver+20%], 30% [VOIliver+30%] and SUV = 10 [VOI10SUV]. The SUVmaxof the normal liver was below 10 (7.2 ± 1.3 in all patients and without significant changes. Overall therapy changes (Δ per patient (mean [95% CI] were statistically significant with p < .01 for ΔCgA = −43 (−69 to −17, ΔSUVmax = −22 (−29 to −14, and ΔVOI10SUV = −53 (−68 to −38% and significant with p < .05 for ΔVOIliver+10% = −29 (−55 to −3%, ΔVOIliver+20% = −32 (−62 to −2 and ΔVOIliver+30% = −37 (−66 to −8. Correlations were found only between ΔCgA and ΔVOI10SUV (r = .595; p < .01, ΔSUVmax and ΔVOI10SUV (0.629, p < .01, and SUVmax and ΔSUVmax (r = .446; p < .05. 68Ga-DOTATOC PET/CT allows volumetric therapy monitoring via an SUV-based cut-off separating hepatic metastases from normal liver tissue (10 SUV recommended.

Volumetric accuracy of cone-beam computed tomography

Energy Technology Data Exchange (ETDEWEB)

Park, Cheol Woo; Kim, Jin Ho; Seo, Yu Kyeong; Lee, Sae Rom; Kang, Ju Hee; Oh, Song Hee; Kim, Gyu Tae; Choi, Yong Suk; Hwang, Eui Hwan [Dept. of Oral and Maxillofacial Radiology, Graduate School, Kyung Hee University, Seoul (Korea, Republic of)

2017-09-15

This study was performed to investigate the influence of object shape and distance from the center of the image on the volumetric accuracy of cone-beam computed tomography (CBCT) scans, according to different parameters of tube voltage and current. Four geometric objects (cylinder, cube, pyramid, and hexagon) with predefined dimensions were fabricated. The objects consisted of Teflon-perfluoroalkoxy embedded in a hydrocolloid matrix (Dupli-Coe-Loid TM; GC America Inc., Alsip, IL, USA), encased in an acrylic resin cylinder assembly. An Alphard Vega Dental CT system (Asahi Roentgen Ind. Co., Ltd, Kyoto, Japan) was used to acquire CBCT images. OnDemand 3D (CyberMed Inc., Seoul, Korea) software was used for object segmentation and image analysis. The accuracy was expressed by the volume error (VE). The VE was calculated under 3 different exposure settings. The measured volumes of the objects were compared to the true volumes for statistical analysis. The mean VE ranged from −4.47% to 2.35%. There was no significant relationship between an object's shape and the VE. A significant correlation was found between the distance of the object to the center of the image and the VE. Tube voltage affected the volume measurements and the VE, but tube current did not. The evaluated CBCT device provided satisfactory volume measurements. To assess volume measurements, it might be sufficient to use serial scans with a high resolution, but a low dose. This information may provide useful guidance for assessing volume measurements.

Volumetric accuracy of cone-beam computed tomography

International Nuclear Information System (INIS)

Park, Cheol Woo; Kim, Jin Ho; Seo, Yu Kyeong; Lee, Sae Rom; Kang, Ju Hee; Oh, Song Hee; Kim, Gyu Tae; Choi, Yong Suk; Hwang, Eui Hwan

2017-01-01

This study was performed to investigate the influence of object shape and distance from the center of the image on the volumetric accuracy of cone-beam computed tomography (CBCT) scans, according to different parameters of tube voltage and current. Four geometric objects (cylinder, cube, pyramid, and hexagon) with predefined dimensions were fabricated. The objects consisted of Teflon-perfluoroalkoxy embedded in a hydrocolloid matrix (Dupli-Coe-Loid TM; GC America Inc., Alsip, IL, USA), encased in an acrylic resin cylinder assembly. An Alphard Vega Dental CT system (Asahi Roentgen Ind. Co., Ltd, Kyoto, Japan) was used to acquire CBCT images. OnDemand 3D (CyberMed Inc., Seoul, Korea) software was used for object segmentation and image analysis. The accuracy was expressed by the volume error (VE). The VE was calculated under 3 different exposure settings. The measured volumes of the objects were compared to the true volumes for statistical analysis. The mean VE ranged from −4.47% to 2.35%. There was no significant relationship between an object's shape and the VE. A significant correlation was found between the distance of the object to the center of the image and the VE. Tube voltage affected the volume measurements and the VE, but tube current did not. The evaluated CBCT device provided satisfactory volume measurements. To assess volume measurements, it might be sufficient to use serial scans with a high resolution, but a low dose. This information may provide useful guidance for assessing volume measurements

Berkeley Lighting Cone

Energy Technology Data Exchange (ETDEWEB)

Lask, Kathleen [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Gadgil, Ashok [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2016-10-24

A lighting cone is a simple metal cone placed on the fuel bed of a stove during ignition to act as a chimney, increasing the draft through the fuel bed. Many stoves tend to be difficult to light due to poor draft through the fuel bed, so lighting cones are used in various parts of the world as an inexpensive accessory to help with ignition.

Development and degeneration of cone bipolar cells are independent of cone photoreceptors in a mouse model of retinitis pigmentosa.

Directory of Open Access Journals (Sweden)

Miao Chen

Full Text Available Retinal photoreceptors die during retinal synaptogenesis in a portion of retinal degeneration. Whether cone bipolar cells establish regular retinal mosaics and mature morphologies, and resist degeneration are not completely understood. To explore these issues, we backcrossed a transgenic mouse expressing enhanced green fluorescent protein (EGFP in one subset of cone bipolar cells (type 7 into rd1 mice, a classic mouse model of retinal degeneration, to examine the development and survival of cone bipolar cells in a background of retinal degeneration. Our data revealed that both the development and degeneration of cone bipolar cells are independent of the normal activity of cone photoreceptors. We found that type 7 cone bipolar cells achieved a uniform tiling of the retinal surface and developed normal dendritic and axonal arbors without the influence of cone photoreceptor innervation. On the other hand, degeneration of type 7 cone bipolar cells, contrary to our belief of central-to-peripheral progression, was spatially uniform across the retina independent of the spatiotemporal pattern of cone degeneration. The results have important implications for the design of more effective therapies to restore vision in retinal degeneration.

A One-Step Cone-Beam CT-Enabled Planning-to-Treatment Model for Palliative Radiotherapy-From Development to Implementation

International Nuclear Information System (INIS)

Wong, Rebecca K.S.; Letourneau, Daniel; Varma, Anita; Bissonnette, Jean Pierre; Fitzpatrick, David; Grabarz, Daniel; Elder, Christine; Martin, Melanie; Bezjak, Andrea; Panzarella, Tony; Gospodarowicz, Mary; Jaffray, David A.

2012-01-01

Purpose: To develop a cone-beam computed tomography (CT)–enabled one-step simulation-to-treatment process for the treatment of bone metastases. Methods and Materials: A three-phase prospective study was conducted. Patients requiring palliative radiotherapy to the spine, mediastinum, or abdomen/pelvis suitable for treatment with simple beam geometry (≤2 beams) were accrued. Phase A established the accuracy of cone-beam CT images for the purpose of gross tumor target volume (GTV) definition. Phase B evaluated the feasibility of implementing the cone-beam CT–enabled planning process at the treatment unit. Phase C evaluated the online cone-beam CT–enabled process for the planning and treatment of patients requiring radiotherapy for bone metastases. Results: Eighty-four patients participated in this study. Phase A (n = 9) established the adequacy of cone-beam CT images for target definition. Phase B (n = 45) established the quality of treatment plans to be adequate for clinical implementation for bone metastases. When the process was applied clinically in bone metastases (Phase C), the degree of overlap between planning computed tomography (PCT) and cone-beam CT for GTV and between PCT and cone-beam CT for treatment field was 82% ± 11% and 97% ± 4%, respectively. The oncologist’s decision to accept the plan under a time-pressured environment remained of high quality, with the cone-beam CT–generated treatment plan delivering at least 90% of the prescribed dose to 100% ± 0% of the cone-beam CT planning target volume (PTV). With the assumption that the PCT PTV is the gold-standard target, the cone-beam CT–generated treatment plan delivered at least 90% and at least 95% of dose to 98% ± 2% and 97% ± 5% of the PCT PTV, respectively. The mean time for the online planning and treatment process was 32.7 ± 4.0 minutes. Patient satisfaction was high, with a trend for superior satisfaction with the cone-beam CT–enabled process. Conclusions: The cone-beam CT�

A One-Step Cone-Beam CT-Enabled Planning-to-Treatment Model for Palliative Radiotherapy-From Development to Implementation

Energy Technology Data Exchange (ETDEWEB)

Wong, Rebecca K.S., E-mail: rebecca.wong@rmp.uhn.on.ca [Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario (Canada); Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Letourneau, Daniel; Varma, Anita [Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario (Canada); Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Bissonnette, Jean Pierre; Fitzpatrick, David; Grabarz, Daniel; Elder, Christine [Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario (Canada); Martin, Melanie; Bezjak, Andrea [Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario (Canada); Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Panzarella, Tony [Department of Biostatistics, Princess Margaret Hospital, Toronto, Ontario (Canada); Gospodarowicz, Mary [Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario (Canada); Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Jaffray, David A. [Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario (Canada); Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Department of Medical Biophysics, University of Toronto, Toronto, Ontario (Canada)

2012-11-01

Purpose: To develop a cone-beam computed tomography (CT)-enabled one-step simulation-to-treatment process for the treatment of bone metastases. Methods and Materials: A three-phase prospective study was conducted. Patients requiring palliative radiotherapy to the spine, mediastinum, or abdomen/pelvis suitable for treatment with simple beam geometry ({<=}2 beams) were accrued. Phase A established the accuracy of cone-beam CT images for the purpose of gross tumor target volume (GTV) definition. Phase B evaluated the feasibility of implementing the cone-beam CT-enabled planning process at the treatment unit. Phase C evaluated the online cone-beam CT-enabled process for the planning and treatment of patients requiring radiotherapy for bone metastases. Results: Eighty-four patients participated in this study. Phase A (n = 9) established the adequacy of cone-beam CT images for target definition. Phase B (n = 45) established the quality of treatment plans to be adequate for clinical implementation for bone metastases. When the process was applied clinically in bone metastases (Phase C), the degree of overlap between planning computed tomography (PCT) and cone-beam CT for GTV and between PCT and cone-beam CT for treatment field was 82% {+-} 11% and 97% {+-} 4%, respectively. The oncologist's decision to accept the plan under a time-pressured environment remained of high quality, with the cone-beam CT-generated treatment plan delivering at least 90% of the prescribed dose to 100% {+-} 0% of the cone-beam CT planning target volume (PTV). With the assumption that the PCT PTV is the gold-standard target, the cone-beam CT-generated treatment plan delivered at least 90% and at least 95% of dose to 98% {+-} 2% and 97% {+-} 5% of the PCT PTV, respectively. The mean time for the online planning and treatment process was 32.7 {+-} 4.0 minutes. Patient satisfaction was high, with a trend for superior satisfaction with the cone-beam CT-enabled process. Conclusions: The cone

A proposed method for accurate 3D analysis of cochlear implant migration using fusion of cone beam CT

Directory of Open Access Journals (Sweden)

Guido eDees

2016-01-01

Full Text Available IntroductionThe goal of this investigation was to compare fusion of sequential cone beam CT volumes to the gold standard (fiducial registration in order to be able to analyze clinical CI migration with high accuracy in three dimensions. Materials and MethodsPaired time-lapsed cone beam CT volumes were performed on five human cadaver temporal bones and one human subject. These volumes were fused using 3D Slicer 4 and BRAINSFit software. Using a gold standard fiducial technique, the accuracy, robustness and performance time of the fusion process were assessed.Results This proposed fusion protocol achieves a sub voxel mean Euclidean distance of 0.05 millimeter in human cadaver temporal bones and 0.16 millimeter when applied to the described in vivo human synthetic data set in over 95% of all fusions. Performance times are less than two minutes.ConclusionHere a new and validated method based on existing techniques is described which could be used to accurately quantify migration of cochlear implant electrodes.

Dynamic 2-[18F]fluoro-2-deoxy-d-glucose positron emission tomography of liver tumours without blood sampling

International Nuclear Information System (INIS)

Keiding, S.; Munk, O.L.; Schioett, K.M.; Hansen, S.B.

2000-01-01

Positron emission tomography (PET) using 2-[ 18 F]fluoro-2-deoxy-d-glucose (FDG) is a useful diagnostic tool for the detection of tumours. Using dynamic FDG PET, net metabolic clearance of FDG, K, can be calculated by Gjedde-Patlak analysis of the time course of the radioactivity concentrations in tissue and arterial blood. We examined whether time-activity curves (TACs) based on arterial blood sampling could be replaced by TACs obtained from the descending aorta in dynamic PET scans of patients with liver tumours. The study was performed in two parts, using data from dynamic liver scans with arterial blood sampling in human subjects: First, data from four patients with no liver tumours and five patients with liver tumours were used as a training group. Volumes of interest were defined in the descending aorta (aorta VOIs) by four different methods. K values were calculated based on the corresponding TACs and compared with those based on TACs of the arterial blood sample radioactivity concentrations. The aorta VOI which gave K values that were in best agreement with the K values based on the arterial blood sample measurements was called the AORTA-VOI. Use of the AORTA-VOI was subsequently tested in a test group of 19 tumour patients by comparing the K values from the AORTA-VOI with the K values based on the arterial blood sample measurements. The AORTA-VOI consisted of the sum of small regions of interest (ROIs) drawn in the centre of the aorta (approximately six pixels of 2.4 x 2.4 mm per transaxial slice of 3.1 mm thickness) in as many transaxial slices as possible (30-40 slices). There were no statistically significant differences between the two sets of K values. The ratio of K values in tumour tissue to K values in reference tissue was 2.1-9.7:1 (mean, 5.4:1) based on the AORTA TACs, and 2.1-8.4:1 (mean, 4.6:1) based on blood sample TACs (P>0.3). We conclude that arterial blood sampling can be replaced by the present AORTA-VOI in the calculation of the net

Progress in light cone physics

International Nuclear Information System (INIS)

Preparata, G.

1973-01-01

A very brief review is given of the progress made in the physics of the light cone in the past year. Included are the light cone expansion, gauge invariance and the consequences of precocious scaling near threshold, the light cone description of the muon pair experiment, light cone expansions, and the assessment and exploitation of analyticity properties in both mass and energy of light cone amplitudes. (U.S.)

Light-cone gauge versus proper-time gauge for massless spinning particles

International Nuclear Information System (INIS)

Skagerstam, B.S.; Stern, A.

1987-01-01

Although the light-cone gauge is convenient for many applications in physics, it is known to distort topology. We show that as a consequence, some interesting, possibly physical, features of a quantum theory may be missed when working in the light-cone gauge. We shall illustrate this by examining the description of massless spinning particles in an arbitrary number of space-time dimensions. When quantizing such particles in four space-time dimensions (without introducing Grassmann degrees of freedom), the light-cone gauge yields a purely bosonic spectrum, i.e. the helicity λ is integer-valued. The problem is rectified by going to the proper-time gauge; there λ = 0, ±1/2, ±1, ... Upon using the proper-time gauge to quantize massless particle systems in more than four space-time dimensions, we find the following interesting features: Except for space-time dimension d equal to 5 and 9, (i) wave functions cannot be expressed as global functions of momentum (or position). (This is also true for d=4.) Further, for d ≠ 5 and 9, (ii) the helicity group spin (d-2) and (iii) canonical position operators do not exist, globally. (The result that helicity cannot be globally defined resembles a known property of nonabelian monopoles arising in grand unified theories. There, topological obstructions prevent one from defining the color group, globally.) All of the features (i)-(iii) are missed when working in the light-cone gauge. (orig.)

Ejecta evolution during cone impact

KAUST Repository

Marston, Jeremy

2014-07-07

We present findings from an experimental investigation into the impact of solid cone-shaped bodies onto liquid pools. Using a variety of cone angles and liquid physical properties, we show that the ejecta formed during the impact exhibits self-similarity for all impact speeds for very low surface tension liquids, whilst for high-surface tension liquids similarity is only achieved at high impact speeds. We find that the ejecta tip can detach from the cone and that this phenomenon can be attributed to the air entrainment phenomenon. We analyse of a range of cone angles, including some ogive cones, and impact speeds in terms of the spatiotemporal evolution of the ejecta tip. Using superhydrophobic cones, we also examine the entry of cones which entrain an air layer.

Asymptomatic radiopaque lesions of the jaws. A radiographic study using cone-beam computed tomography

International Nuclear Information System (INIS)

Araki, Masao; Matsumoto, Naoyuki; Matsumoto, Kunihito; Ohnishi, Masaaki; Honda, Kazuya; Komiyama, Kazuo

2011-01-01

Panoramic radiography and cone-beam computed tomography (CT) were used to analyze asymptomatic radiopaque lesions in the jaw bones and determine the diagnostic relevance of the lesions based on their relationships to teeth and site of origin. One hundred radiopaque lesions detected between 1998 and 2002 were examined by both panoramic radiography and cone-beam CT. On the basis of panoramic radiographs, the region was classified as periapical, body, or edentulous, and the site was classified as molar or premolar. Follow-up data from medical records were available for only 36 of these cases. The study protocol for simultaneous use of cone-beam CT was approved by the ethics review board of our institution. A large majority of radiopaque lesions were observed in premolar and molar sites of the mandible; 60% of lesions were periapical, 24% were in the body, and 16% were in the edentulous region. An interesting type of radiopaque lesion, which we named a pearl shell structure (PSS), was observed on cone-beam CT in 34 of the 100 lesions. The PSS is a distinctive structure, and this finding on cone-beam CT likely represents the start of bone formation before bone sclerosis. (author)

ON Cone Bipolar Cell Axonal Synapses in the OFF Inner Plexiform Layer of the Rabbit Retina

Science.gov (United States)

Lauritzen, J. Scott; Anderson, James R.; Jones, Bryan W.; Watt, Carl B.; Mohammed, Shoeb; Hoang, John V.; Marc, Robert E.

2012-01-01

Analysis of the rabbit retinal connectome RC1 reveals that the division between the ON and OFF inner plexiform layer (IPL) is not structurally absolute. ON cone bipolar cells make non-canonical axonal synapses onto specific targets and receive amacrine cell synapses in the nominal OFF layer, creating novel motifs, including inhibitory crossover networks. Automated transmission electron microscope (ATEM) imaging, molecular tagging, tracing, and rendering of ≈ 400 bipolar cells reveals axonal ribbons in 36% of ON cone bipolar cells, throughout the OFF IPL. The targets include GABA-positive amacrine cells (γACs), glycine-positive amacrine cells (GACs) and ganglion cells. Most ON cone bipolar cell axonal contacts target GACs driven by OFF cone bipolar cells, forming new architectures for generating ON-OFF amacrine cells. Many of these ON-OFF GACs target ON cone bipolar cell axons, ON γACs and/or ON-OFF ganglion cells, representing widespread mechanisms for OFF to ON crossover inhibition. Other targets include OFF γACs presynaptic to OFF bipolar cells, forming γAC-mediated crossover motifs. ON cone bipolar cell axonal ribbons drive bistratified ON-OFF ganglion cells in the OFF layer and provide ON drive to polarity-appropriate targets such as bistratified diving ganglion cells (bsdGCs). The targeting precision of ON cone bipolar cell axonal synapses shows that this drive incidence is necessarily a joint distribution of cone bipolar cell axonal frequency and target cell trajectories through a given volume of the OFF layer. Such joint distribution sampling is likely common when targets are sparser than sources and when sources are coupled, as are ON cone bipolar cells. PMID:23042441

Design of a trichromatic cone array.

Directory of Open Access Journals (Sweden)

Patrick Garrigan

2010-02-01

Full Text Available Cones with peak sensitivity to light at long (L, medium (M and short (S wavelengths are unequal in number on the human retina: S cones are rare (<10% while increasing in fraction from center to periphery, and the L/M cone proportions are highly variable between individuals. What optical properties of the eye, and statistical properties of natural scenes, might drive this organization? We found that the spatial-chromatic structure of natural scenes was largely symmetric between the L, M and S sensitivity bands. Given this symmetry, short wavelength attenuation by ocular media gave L/M cones a modest signal-to-noise advantage, which was amplified, especially in the denser central retina, by long-wavelength accommodation of the lens. Meanwhile, total information represented by the cone mosaic remained relatively insensitive to L/M proportions. Thus, the observed cone array design along with a long-wavelength accommodated lens provides a selective advantage: it is maximally informative.

Time-resolved C-arm cone beam CT angiography (TR-CBCTA) imaging from a single short-scan C-arm cone beam CT acquisition with intra-arterial contrast injection

Science.gov (United States)

Li, Yinsheng; Garrett, John W.; Li, Ke; Wu, Yijing; Johnson, Kevin; Schafer, Sebastian; Strother, Charles; Chen, Guang-Hong

2018-04-01

Time-resolved C-arm cone-beam CT (CBCT) angiography (TR-CBCTA) images can be generated from a series of CBCT acquisitions that satisfy data sufficiency condition in analytical image reconstruction theory. In this work, a new technique was developed to generate TR-CBCTA images from a single short-scan CBCT data acquisition with contrast media injection. The reconstruction technique enabling this application is a previously developed image reconstruction technique, synchronized multi-artifact reduction with tomographic reconstruction (SMART-RECON). In this new application, the acquired short-scan CBCT projection data were sorted into a union of several sub-sectors of view angles and each sub-sector of view angles corresponds to an individual image volume to be reconstructed. The SMART-RECON method was then used to jointly reconstruct all of these individual image volumes under two constraints: (1) each individual image volume is maximally consistent with the measured cone-beam projection data within the corresponding view angle sector and (2) the nuclear norm of the image matrix is minimized. The difference between these reconstructed individual image volumes is used to generated the desired subtracted angiograms. To validate the technique, numerical simulation data generated from a fractal tree angiogram phantom were used to quantitatively study the accuracy of the proposed method and retrospective in vivo human subject studies were used to demonstrate the feasibility of generating TR-CBCTA in clinical practice.

A combination-weighted Feldkamp-based reconstruction algorithm for cone-beam CT

International Nuclear Information System (INIS)

Mori, Shinichiro; Endo, Masahiro; Komatsu, Shuhei; Kandatsu, Susumu; Yashiro, Tomoyasu; Baba, Masayuki

2006-01-01

The combination-weighted Feldkamp algorithm (CW-FDK) was developed and tested in a phantom in order to reduce cone-beam artefacts and enhance cranio-caudal reconstruction coverage in an attempt to improve image quality when utilizing cone-beam computed tomography (CBCT). Using a 256-slice cone-beam CT (256CBCT), image quality (CT-number uniformity and geometrical accuracy) was quantitatively evaluated in phantom and clinical studies, and the results were compared to those obtained with the original Feldkamp algorithm. A clinical study was done in lung cancer patients under breath holding and free breathing. Image quality for the original Feldkamp algorithm is degraded at the edge of the scan region due to the missing volume, commensurate with the cranio-caudal distance between the reconstruction and central planes. The CW-FDK extended the reconstruction coverage to equal the scan coverage and improved reconstruction accuracy, unaffected by the cranio-caudal distance. The extended reconstruction coverage with good image quality provided by the CW-FDK will be clinically investigated for improving diagnostic and radiotherapy applications. In addition, this algorithm can also be adapted for use in relatively wide cone-angle CBCT such as with a flat-panel detector CBCT

Correlation Between Cone Penetration Rate And Measured Cone Penetration Parameters In Silty Soils

DEFF Research Database (Denmark)

Poulsen, Rikke; Nielsen, Benjaminn Nordahl; Ibsen, Lars Bo

2013-01-01

This paper shows, how a change in cone penetration rate affects the cone penetration measurements, hence the cone resistance, pore pressure, and sleeve friction in silty soil. The standard rate of penetration is 20 mm/s, and it is generally accepted that undrained penetration occurs in clay while...... drained penetration occurs in sand. When lowering the penetration rate, the soil pore water starts to dissipate and a change in the drainage condition is seen. In intermediate soils such as silty soils, the standard cone penetration rate may result in a drainage condition that could be undrained......, partially or fully drained. However, lowering the penetration rate in silty soils has a great significance because of the soil permeability, and only a small change in penetration rate will result in changed cone penetration measurements. In this paper, analyses will be done on data from 15 field cone...

Evaluation of tilted cone-beam CT orbits in the development of a dedicated hybrid mammotomograph

International Nuclear Information System (INIS)

Madhav, P; Crotty, D J; Tornai, M P; McKinley, R L

2009-01-01

A compact dedicated 3D breast SPECT-CT (mammotomography) system is currently under development. In its initial prototype, the cone-beam CT sub-system is restricted to a fixed-tilt circular rotation around the patient's pendant breast. This study evaluated stationary-tilt angles for the CT sub-system that will enable maximal volumetric sampling and viewing of the breast and chest wall. Images of geometric/anthropomorphic phantoms were acquired using various fixed-tilt circular and 3D sinusoidal trajectories. The iteratively reconstructed images showed more distortion and attenuation coefficient inaccuracy from tilted cone-beam orbits than from the complex trajectory. Additionally, line profiles illustrated cupping artifacts in planes distal to the central plane of the tilted cone-beam, otherwise not apparent for images acquired with complex trajectories. This indicates that undersampled cone-beam data may be an additional cause of cupping artifacts. High-frequency objects could be distinguished for all trajectories, but their shapes and locations were corrupted by out-of-plane frequency information. Although more acrylic balls were visualized with a fixed-tilt and nearly flat cone-beam at the posterior of the breast, 3D complex trajectories have less distortion and more complete sampling throughout the reconstruction volume. While complex trajectories would ideally be preferred, negatively fixed-tilt source-detector configuration demonstrates minimally distorted patient images.

Cone and Seed Maturation of Southern Pines

Science.gov (United States)

James P. Barnett

1976-01-01

If slightly reduced yields and viability are acceptable, loblolly and slash cone collections can begin 2 to 3 weeks before maturity if the cones are stored before processing. Longleaf(P. palestris Mill.) pine cones should be collected only when mature, as storage decreased germination of seeds from immature cones. Biochemical analyses to determine reducing sugar...

Comparison of manual and automated quantification methods of 123I-ADAM

International Nuclear Information System (INIS)

Kauppinen, T.; Keski-Rahkonen, A.; Sihvola, E.; Helsinki Univ. Central Hospital

2005-01-01

123 I-ADAM is a novel radioligand for imaging of the brain serotonin transporters (SERTs). Traditionally, the analysis of brain receptor studies has been based on observer-dependent manual region of interest definitions and visual interpretation. Our aim was to create a template for automated image registrations and volume of interest (VOI) quantification and to show that an automated quantification method of 123 I-ADAM is more repeatable than the manual method. Patients, methods: A template and a predefined VOI map was created from 123 I-ADAM scans done for healthy volunteers (n=15). Scans of another group of healthy persons (HS, n=12) and patients with bulimia nervosa (BN, n=10) were automatically fitted to the template and specific binding ratios (SBRs) were calculated by using the VOI map. Manual VOI definitions were done for the HS and BN groups by both one and two observers. The repeatability of the automated method was evaluated by using the BN group. Results: For the manual method, the interobserver coefficient of repeatability was 0.61 for the HS group and 1.00 for the BN group. The intra-observer coefficient of repeatability for the BN group was 0.70. For the automated method, the coefficient of repeatability was 0.13 for SBRs in midbrain. Conclusion: An automated quantification gives valuable information in addition to visual interpretation decreasing also the total image handling time and giving clear advantages for research work. An automated method for analysing 123 I-ADAM binding to the brain SERT gives repeatable results for fitting the studies to the template and for calculating SBRs, and could therefore replace manual methods. (orig.)

A simple algorithm for subregional striatal uptake analysis with partial volume correction in dopaminergic PET imaging

International Nuclear Information System (INIS)

Lue Kunhan; Lin Hsinhon; Chuang Kehshih; Kao Chihhao, K.; Hsieh Hungjen; Liu Shuhsin

2014-01-01

In positron emission tomography (PET) of the dopaminergic system, quantitative measurements of nigrostriatal dopamine function are useful for differential diagnosis. A subregional analysis of striatal uptake enables the diagnostic performance to be more powerful. However, the partial volume effect (PVE) induces an underestimation of the true radioactivity concentration in small structures. This work proposes a simple algorithm for subregional analysis of striatal uptake with partial volume correction (PVC) in dopaminergic PET imaging. The PVC algorithm analyzes the separate striatal subregions and takes into account the PVE based on the recovery coefficient (RC). The RC is defined as the ratio of the PVE-uncorrected to PVE-corrected radioactivity concentration, and is derived from a combination of the traditional volume of interest (VOI) analysis and the large VOI technique. The clinical studies, comprising 11 patients with Parkinson's disease (PD) and 6 healthy subjects, were used to assess the impact of PVC on the quantitative measurements. Simulations on a numerical phantom that mimicked realistic healthy and neurodegenerative situations were used to evaluate the performance of the proposed PVC algorithm. In both the clinical and the simulation studies, the striatal-to-occipital ratio (SOR) values for the entire striatum and its subregions were calculated with and without PVC. In the clinical studies, the SOR values in each structure (caudate, anterior putamen, posterior putamen, putamen, and striatum) were significantly higher by using PVC in contrast to those without. Among the PD patients, the SOR values in each structure and quantitative disease severity ratings were shown to be significantly related only when PVC was used. For the simulation studies, the average absolute percentage error of the SOR estimates before and after PVC were 22.74% and 1.54% in the healthy situation, respectively; those in the neurodegenerative situation were 20.69% and 2

The impact of reconstruction and scanner characterisation on the diagnostic capability of a normal database for [(123)I]FP-CIT SPECT imaging

DEFF Research Database (Denmark)

Dickson, John C; Tossici-Bolt, Livia; Sera, Terez

2017-01-01

for scan normality using the ENC-DAT normal database obtained in well-documented healthy subjects. Patient and normal data were reconstructed with iterative reconstruction with correction for attenuation, scatter and septal penetration (ACSC), the same reconstruction without corrections (IRNC......), and filtered back-projection (FBP) with data quantified using small volume-of-interest (VOI) (BRASS) and large VOI (Southampton) analysis methods. Test performance was assessed with and without system characterisation, using receiver operating characteristics (ROC) analysis for age-independent data and using......BACKGROUND: The use of a normal database for [(123)I]FP-CIT SPECT imaging has been found to be helpful for cases which are difficult to interpret by visual assessment alone, and to improve reproducibility in scan interpretation. The aim of this study was to assess whether the use of different...

Comparison of manual and automated quantification methods of {sup 123}I-ADAM

Energy Technology Data Exchange (ETDEWEB)

Kauppinen, T. [Helsinki Univ. Central Hospital (Finland). HUS Helsinki Medical Imaging Center; Helsinki Univ. Central Hospital (Finland). Division of Nuclear Medicine; Koskela, A.; Ahonen, A. [Helsinki Univ. Central Hospital (Finland). Division of Nuclear Medicine; Diemling, M. [Hermes Medical Solutions, Stockholm (Sweden); Keski-Rahkonen, A.; Sihvola, E. [Helsinki Univ. (Finland). Dept. of Public Health; Helsinki Univ. Central Hospital (Finland). Dept. of Psychiatry

2005-07-01

{sup 123}I-ADAM is a novel radioligand for imaging of the brain serotonin transporters (SERTs). Traditionally, the analysis of brain receptor studies has been based on observer-dependent manual region of interest definitions and visual interpretation. Our aim was to create a template for automated image registrations and volume of interest (VOI) quantification and to show that an automated quantification method of {sup 123}I-ADAM is more repeatable than the manual method. Patients, methods: A template and a predefined VOI map was created from {sup 123}I-ADAM scans done for healthy volunteers (n=15). Scans of another group of healthy persons (HS, n=12) and patients with bulimia nervosa (BN, n=10) were automatically fitted to the template and specific binding ratios (SBRs) were calculated by using the VOI map. Manual VOI definitions were done for the HS and BN groups by both one and two observers. The repeatability of the automated method was evaluated by using the BN group. Results: For the manual method, the interobserver coefficient of repeatability was 0.61 for the HS group and 1.00 for the BN group. The intra-observer coefficient of repeatability for the BN group was 0.70. For the automated method, the coefficient of repeatability was 0.13 for SBRs in midbrain. Conclusion: An automated quantification gives valuable information in addition to visual interpretation decreasing also the total image handling time and giving clear advantages for research work. An automated method for analysing {sup 123}I-ADAM binding to the brain SERT gives repeatable results for fitting the studies to the template and for calculating SBRs, and could therefore replace manual methods. (orig.)

”EI OIKEASSA ELÄMÄSSÄ VOI JUOSTA MIEKKA OJOSSA LOHIKÄÄRMETTÄ KOHTI”: Digipelaajien kokemus omasta hyvinvoinnistaan

OpenAIRE

Engström, Paula

2016-01-01

Paula Engström. ”Ei oikeassa elämässä voi juosta miekka ojossa lohikäärmettä kohti”: Digipelaajien kokemus omasta hyvinvoinnistaan. Diak Etelä, Helsinki, syksy 2016, 57s., 1 liite. Diakonia-ammattikorkeakoulu, Sosiaalialan koulutusohjelma, sosionomi (AMK). Opinnäytetyön aihe syntyi Ehkäisevä päihdetyö EHYT ry:n toiveista saada kooste vuonna 2015 toteutetun Pelaajien hyvinvointikyselyn tuloksista. Opinnäytetyön tavoitteena oli saada selville, miten digitaalisia pelejä harrastavat nuor...

Metabolic liver function measured in vivo by dynamic (18)F-FDGal PET/CT without arterial blood sampling.

Science.gov (United States)

Horsager, Jacob; Munk, Ole Lajord; Sørensen, Michael

2015-01-01

Metabolic liver function can be measured by dynamic PET/CT with the radio-labelled galactose-analogue 2-[(18)F]fluoro-2-deoxy-D-galactose ((18)F-FDGal) in terms of hepatic systemic clearance of (18)F-FDGal (K, ml blood/ml liver tissue/min). The method requires arterial blood sampling from a radial artery (arterial input function), and the aim of this study was to develop a method for extracting an image-derived, non-invasive input function from a volume of interest (VOI). Dynamic (18)F-FDGal PET/CT data from 16 subjects without liver disease (healthy subjects) and 16 patients with liver cirrhosis were included in the study. Five different input VOIs were tested: four in the abdominal aorta and one in the left ventricle of the heart. Arterial input function from manual blood sampling was available for all subjects. K*-values were calculated using time-activity curves (TACs) from each VOI as input and compared to the K-value calculated using arterial blood samples as input. Each input VOI was tested on PET data reconstructed with and without resolution modelling. All five image-derived input VOIs yielded K*-values that correlated significantly with K calculated using arterial blood samples. Furthermore, TACs from two different VOIs yielded K*-values that did not statistically deviate from K calculated using arterial blood samples. A semicircle drawn in the posterior part of the abdominal aorta was the only VOI that was successful for both healthy subjects and patients as well as for PET data reconstructed with and without resolution modelling. Metabolic liver function using (18)F-FDGal PET/CT can be measured without arterial blood samples by using input data from a semicircle VOI drawn in the posterior part of the abdominal aorta.

Quantification of 18F-FDG PET images using probabilistic brain atlas: clinical application in temporal lobe epilepsy patients

International Nuclear Information System (INIS)

Kang, Keon Wook; Lee, Dong Soo; Cho, Jae Hoon; Lee, Jae Sung; Yeo, Jeong Seok; Lee, Sang Gun; Chung, June Key; Lee, Myung Chul

2000-01-01

A probabilistic atlas of the human brain (Statistical Probability Anatomical Maps: SPAM) was developed by the international consortium for brain mapping (ICBM). After calculating the counts in volume of interest (VOI) using the product of probability of SPAM images and counts in FDG images, asymmetric indexes(AI) were calculated and used for finding epileptogenic zones in temporal lobe epilepsy (TLE). FDG PET images from 28 surgically confirmed TLE patients and 12 age-matched controls were spatially normalized to the averaged brain MRI atlas of ICBM. The counts from normalized PET images were multiplied with the probability of 12 VOIs (superior temporal gyrus, middle temporal gyrus, inferior temporal gyrus, hippocampus, parahippocampal gyrus, and amygdala in each hemisphere) of SPAM images of Montreal Neurological Institute. Finally AI was calculated on each pair of VOI, and compared with visual assessment. If AI was deviated more than 2 standard deviation of normal controls, we considered epileptogenic zones were found successfully. The counts of VOIs in normal controls were symmetric (AI 0.05) except those of inferior temporal gyrus (p<0.01). AIs in 5 pairs of VOI excluding inferior temporal gyrus were deviated to one side in TLE (p<0.05). Lateralization was correct in 23/28 of patients by AI, but all of 28 were consistent with visual inspection. In 3 patients with normal AI was symmetric on visual inspection. In 2 patients falsely lateralized using AI, metabolism was also decreased visually on contra-lateral side. Asymmetric index obtained by the product of statistical probability anatomical map and FDG PET correlated well with visual assessment in TLE patients. SPAM is useful for quantification of VOIs in functional images

Computational Study of Hypersonic Boundary Layer Stability on Cones

Science.gov (United States)

Gronvall, Joel Edwin

Due to the complex nature of boundary layer laminar-turbulent transition in hypersonic flows and the resultant effect on the design of re-entry vehicles, there remains considerable interest in developing a deeper understanding of the underlying physics. To that end, the use of experimental observations and computational analysis in a complementary manner will provide the greatest insights. It is the intent of this work to provide such an analysis for two ongoing experimental investigations. The first focuses on the hypersonic boundary layer transition experiments for a slender cone that are being conducted at JAXA's free-piston shock tunnel HIEST facility. Of particular interest are the measurements of disturbance frequencies associated with transition at high enthalpies. The computational analysis provided for these cases included two-dimensional CFD mean flow solutions for use in boundary layer stability analyses. The disturbances in the boundary layer were calculated using the linear parabolized stability equations. Estimates for transition locations, comparisons of measured disturbance frequencies and computed frequencies, and a determination of the type of disturbances present were made. It was found that for the cases where the disturbances were measured at locations where the flow was still laminar but nearly transitional, that the highly amplified disturbances showed reasonable agreement with the computations. Additionally, an investigation of the effects of finite-rate chemistry and vibrational excitation on flows over cones was conducted for a set of theoretical operational conditions at the HIEST facility. The second study focuses on transition in three-dimensional hypersonic boundary layers, and for this the cone at angle of attack experiments being conducted at the Boeing/AFOSR Mach-6 quiet tunnel at Purdue University were examined. Specifically, the effect of surface roughness on the development of the stationary crossflow instability are investigated

Inverted cones grating for flexible metafilter at optical and infrared frequencies

Energy Technology Data Exchange (ETDEWEB)

Brückner, Jean-Baptiste; Le Rouzo, Judikaël; Escoubas, Ludovic [Aix-Marseille Université, IM2NP, CNRS-UMR 7334, Domaine Universitaire de Saint-Jérôme, Service 231, 13397 Marseille Cedex 20 (France); Brissonneau, Vincent; Dubarry, Christophe [CEA-LITEN DTNM, 17 Avenue des Martyrs, 38054 Grenoble cedex 9 (France); Ferchichi, Abdelkerim; Gourgon, Cécile [LTM CNRS, Laboratoire des Technologies de la Microélectronique 17 Avenue des Martyrs, 38054 Grenoble cedex 9 (France); Berginc, Gérard [Thales Optronique S.A., 2 Avenue Gay Lussac, 78990 Elancourt (France)

2014-02-24

By combining the antireflective properties from gradual changes in the effective refractive index and cavity coupling from cone gratings and the efficient optical behavior of a tungsten film, a flexible filter showing very broad antireflective properties from the visible to short wavelength infrared region and, simultaneously, a mirror-like behavior in the mid-infrared wavelength region and long-infrared wavelength region has been conceived. Nanoimprint technology has permitted the replication of inverted cone patterns on a large scale on a flexible polymer, afterwards coated with a thin tungsten film. This optical metafilter is of great interest in the stealth domain where optical signature reduction from the optical to short wavelength infrared region is an important matter. As it also acts as selective thermal emitter offering a good solar-absorption/infrared-emissivity ratio, interests are found as well for solar heating applications.

A general exact method for synthesizing parallel-beam projections from cone-beam projections via filtered backprojection

International Nuclear Information System (INIS)

Li Liang; Chen Zhiqiang; Xing Yuxiang; Zhang Li; Kang Kejun; Wang Ge

2006-01-01

In recent years, image reconstruction methods for cone-beam computed tomography (CT) have been extensively studied. However, few of these studies discussed computing parallel-beam projections from cone-beam projections. In this paper, we focus on the exact synthesis of complete or incomplete parallel-beam projections from cone-beam projections. First, an extended central slice theorem is described to establish a relationship between the Radon space and the Fourier space. Then, data sufficiency conditions are proposed for computing parallel-beam projection data from cone-beam data. Using these results, a general filtered backprojection algorithm is formulated that can exactly synthesize parallel-beam projection data from cone-beam projection data. As an example, we prove that parallel-beam projections can be exactly synthesized in an angular range in the case of circular cone-beam scanning. Interestingly, this angular range is larger than that derived in the Feldkamp reconstruction framework. Numerical experiments are performed in the circular scanning case to verify our method

Analytical fan-beam and cone-beam reconstruction algorithms with uniform attenuation correction for SPECT

International Nuclear Information System (INIS)

Tang Qiulin; Zeng, Gengsheng L; Gullberg, Grant T

2005-01-01

In this paper, we developed an analytical fan-beam reconstruction algorithm that compensates for uniform attenuation in SPECT. The new fan-beam algorithm is in the form of backprojection first, then filtering, and is mathematically exact. The algorithm is based on three components. The first one is the established generalized central-slice theorem, which relates the 1D Fourier transform of a set of arbitrary data and the 2D Fourier transform of the backprojected image. The second one is the fact that the backprojection of the fan-beam measurements is identical to the backprojection of the parallel measurements of the same object with the same attenuator. The third one is the stable analytical reconstruction algorithm for uniformly attenuated Radon data, developed by Metz and Pan. The fan-beam algorithm is then extended into a cone-beam reconstruction algorithm, where the orbit of the focal point of the cone-beam imaging geometry is a circle. This orbit geometry does not satisfy Tuy's condition and the obtained cone-beam algorithm is an approximation. In the cone-beam algorithm, the cone-beam data are first backprojected into the 3D image volume; then a slice-by-slice filtering is performed. This slice-by-slice filtering procedure is identical to that of the fan-beam algorithm. Both the fan-beam and cone-beam algorithms are efficient, and computer simulations are presented. The new cone-beam algorithm is compared with Bronnikov's cone-beam algorithm, and it is shown to have better performance with noisy projections

Lateralisation with magnetic resonance spectroscopic imaging in temporal lobe epilepsy: an evaluation of visual and region-of-interest analysis of metabolite concentration images

Energy Technology Data Exchange (ETDEWEB)

Vikhoff-Baaz, B. [Sahlgrenska University Hospital, Goeteborg (Sweden); Div. of Medical Physics and Biomedical Engineering, Goeteborg Univ. (Sweden); Goeteborg Univ. (Sweden). Dept. of Radiation Physics; Malmgren, K. [Dept. of Neurology, Goeteborg Univ. (Sweden); Joensson, L.; Ekholm, S. [Dept. of Radiology, Goeteborg Univ. (Sweden); Starck, G. [Div. of Medical Physics and Biomedical Engineering, Goeteborg Univ. (Sweden); Ljungberg, M.; Forssell-Aronsson, E. [Goeteborg Univ. (Sweden). Dept. of Radiation Physics; Uvebrant, P. [Dept. of Paediatrics, Goeteborg Univ. (Sweden)

2001-09-01

We carried out spectroscopic imaging (MRSI) on nine consecutive patients with temporal lobe epilepsy being assessed for epilepsy surgery, and nine neurologically healthy, age-matched volunteers. A volume of interest (VOI) was angled along the temporal horns on axial and sagittal images, and symmetrically over the temporal lobes on coronal images. Images showing the concentrations of N-acetylaspartate (NAA) and of choline-containing compounds plus creatine and phosphocreatine (Cho + Cr) were used for lateralisation. We compared assessment by visual inspection and by signal analysis from regions of interest (ROI) in different positions, where side-to-side differences in NAA/(Cho + Cr) ratio were used for lateralisation. The NAA/(Cho + Cr) ratio from the different ROI was also compared with that in the brain stem to assess if the latter could be used as an internal reference, e. g., for identification of bilateral changes. The metabolite concentration images were found useful for lateralisation of temporal lobe abnormalities related to epilepsy. Visual analysis can, with high accuracy, be used routinely. ROI analysis is useful for quantifying changes, giving more quantitative information about spatial distribution and the degree of signal loss. There was a large variation in NAA/(Cho + Cr) values in both patients and volunteers. The brain stem may be used as a reference for identification of bilateral changes. (orig.)

Lateralisation with magnetic resonance spectroscopic imaging in temporal lobe epilepsy: an evaluation of visual and region-of-interest analysis of metabolite concentration images

International Nuclear Information System (INIS)

Vikhoff-Baaz, B.; Joensson, L.; Ekholm, S.; Starck, G.

2001-01-01

We carried out spectroscopic imaging (MRSI) on nine consecutive patients with temporal lobe epilepsy being assessed for epilepsy surgery, and nine neurologically healthy, age-matched volunteers. A volume of interest (VOI) was angled along the temporal horns on axial and sagittal images, and symmetrically over the temporal lobes on coronal images. Images showing the concentrations of N-acetylaspartate (NAA) and of choline-containing compounds plus creatine and phosphocreatine (Cho + Cr) were used for lateralisation. We compared assessment by visual inspection and by signal analysis from regions of interest (ROI) in different positions, where side-to-side differences in NAA/(Cho + Cr) ratio were used for lateralisation. The NAA/(Cho + Cr) ratio from the different ROI was also compared with that in the brain stem to assess if the latter could be used as an internal reference, e. g., for identification of bilateral changes. The metabolite concentration images were found useful for lateralisation of temporal lobe abnormalities related to epilepsy. Visual analysis can, with high accuracy, be used routinely. ROI analysis is useful for quantifying changes, giving more quantitative information about spatial distribution and the degree of signal loss. There was a large variation in NAA/(Cho + Cr) values in both patients and volunteers. The brain stem may be used as a reference for identification of bilateral changes. (orig.)

Spectral characteristics of light sources for S-cone stimulation.

Science.gov (United States)

Schlegelmilch, F; Nolte, R; Schellhorn, K; Husar, P; Henning, G; Tornow, R P

2002-11-01

Electrophysiological investigations of the short-wavelength sensitive pathway of the human eye require the use of a suitable light source as a S-cone stimulator. Different light sources with their spectral distribution properties were investigated and compared with the ideal S-cone stimulator. First, the theoretical background of the calculation of relative cone energy absorption from the spectral distribution function of the light source is summarized. From the results of the calculation, the photometric properties of the ideal S-cone stimulator will be derived. The calculation procedure was applied to virtual light sources (computer generated spectral distribution functions with different medium wavelengths and spectrum widths) and to real light sources (blue and green light emitting diodes, blue phosphor of CRT-monitor, multimedia projector, LCD monitor and notebook display). The calculated relative cone absorbencies are compared to the conditions of an ideal S-cone stimulator. Monochromatic light sources with wavelengths of less than 456 nm are close to the conditions of an ideal S-cone stimulator. Spectrum widths up to 21 nm do not affect the S-cone activation significantly (S-cone activation change < 0.2%). Blue light emitting diodes with peak wavelength at 448 nm and spectrum bandwidth of 25 nm are very useful for S-cone stimulation (S-cone activation approximately 95%). A suitable display for S-cone stimulation is the Trinitron computer monitor (S-cone activation approximately 87%). The multimedia projector has a S-cone activation up to 91%, but their spectral distribution properties depends on the selected intensity. LCD monitor and notebook displays have a lower S-cone activation (< or = 74%). Carefully selecting the blue light source for S-cone stimulation can reduce the unwanted L-and M-cone activation down to 4% for M-cones and 1.5% for L-cones.

Light-cone distribution amplitudes of the baryon octet

International Nuclear Information System (INIS)

Bali, Gunnar S.; Braun, Vladimir M.; Göckeler, Meinulf; Gruber, Michael; Hutzler, Fabian; Schäfer, Andreas; Schiel, Rainer W.; Simeth, Jakob; Söldner, Wolfgang; Sternbeck, Andre; Wein, Philipp

2016-01-01

We present results of the first ab initio lattice QCD calculation of the normalization constants and first moments of the leading twist distribution amplitudes of the full baryon octet, corresponding to the small transverse distance limit of the associated S-wave light-cone wave functions. The P-wave (higher twist) normalization constants are evaluated as well. The calculation is done using N_f=2+1 flavors of dynamical (clover) fermions on lattices of different volumes and pion masses down to 222 MeV. Significant SU(3) flavor symmetry violation effects in the shape of the distribution amplitudes are observed.

Light-cone distribution amplitudes of the baryon octet

Energy Technology Data Exchange (ETDEWEB)

Bali, Gunnar S. [Institut für Theoretische Physik, Universität Regensburg,Universitätsstraße 31, D-93040 Regensburg (Germany); Department of Theoretical Physics, Tata Institute of Fundamental Research,Homi Bhabha Road, Mumbai 400005 (India); Braun, Vladimir M.; Göckeler, Meinulf; Gruber, Michael; Hutzler, Fabian; Schäfer, Andreas; Schiel, Rainer W.; Simeth, Jakob; Söldner, Wolfgang [Institut für Theoretische Physik, Universität Regensburg,Universitätsstraße 31, D-93040 Regensburg (Germany); Sternbeck, Andre [Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universität Jena,Max-Wien-Platz 1, D-07743 Jena (Germany); Wein, Philipp [Institut für Theoretische Physik, Universität Regensburg,Universitätsstraße 31, D-93040 Regensburg (Germany)

2016-02-10

We present results of the first ab initio lattice QCD calculation of the normalization constants and first moments of the leading twist distribution amplitudes of the full baryon octet, corresponding to the small transverse distance limit of the associated S-wave light-cone wave functions. The P-wave (higher twist) normalization constants are evaluated as well. The calculation is done using N{sub f}=2+1 flavors of dynamical (clover) fermions on lattices of different volumes and pion masses down to 222 MeV. Significant SU(3) flavor symmetry violation effects in the shape of the distribution amplitudes are observed.

Computerized detection of diffuse lung disease in MDCT: the usefulness of statistical texture features

International Nuclear Information System (INIS)

Wang Jiahui; Li Qiang; Li Feng; Doi Kunio

2009-01-01

Accurate detection of diffuse lung disease is an important step for computerized diagnosis and quantification of this disease. It is also a difficult clinical task for radiologists. We developed a computerized scheme to assist radiologists in the detection of diffuse lung disease in multi-detector computed tomography (CT). Two radiologists selected 31 normal and 37 abnormal CT scans with ground glass opacity, reticular, honeycombing and nodular disease patterns based on clinical reports. The abnormal cases in our database must contain at least an abnormal area with a severity of moderate or severe level that was subjectively rated by the radiologists. Because statistical texture features may lack the power to distinguish a nodular pattern from a normal pattern, the abnormal cases that contain only a nodular pattern were excluded. The areas that included specific abnormal patterns in the selected CT images were then delineated as reference standards by an expert chest radiologist. The lungs were first segmented in each slice by use of a thresholding technique, and then divided into contiguous volumes of interest (VOIs) with a 64 x 64 x 64 matrix size. For each VOI, we determined and employed statistical texture features, such as run-length and co-occurrence matrix features, to distinguish abnormal from normal lung parenchyma. In particular, we developed new run-length texture features with clear physical meanings to considerably improve the accuracy of our detection scheme. A quadratic classifier was employed for distinguishing between normal and abnormal VOIs by the use of a leave-one-case-out validation scheme. A rule-based criterion was employed to further determine whether a case was normal or abnormal. We investigated the impact of new and conventional texture features, VOI size and the dimensionality for regions of interest on detecting diffuse lung disease. When we employed new texture features for 3D VOIs of 64 x 64 x 64 voxels, our system achieved the

Chloride currents in cones modify feedback from horizontal cells to cones in goldfish retina

Science.gov (United States)

Endeman, Duco; Fahrenfort, Iris; Sjoerdsma, Trijntje; Steijaert, Marvin; ten Eikelder, Huub; Kamermans, Maarten

2012-01-01

In neuronal systems, excitation and inhibition must be well balanced to ensure reliable information transfer. The cone/horizontal cell (HC) interaction in the retina is an example of this. Because natural scenes encompass an enormous intensity range both in temporal and spatial domains, the balance between excitation and inhibition in the outer retina needs to be adaptable. How this is achieved is unknown. Using electrophysiological techniques in the isolated retina of the goldfish, it was found that opening Ca2+-dependent Cl− channels in recorded cones reduced the size of feedback responses measured in both cones and HCs. Furthermore, we show that cones express Cl− channels that are gated by GABA released from HCs. Similar to activation of ICl(Ca), opening of these GABA-gated Cl− channels reduced the size of light-induced feedback responses both in cones and HCs. Conversely, application of picrotoxin, a blocker of GABAA and GABAC receptors, had the opposite effect. In addition, reducing GABA release from HCs by blocking GABA transporters also led to an increase in the size of feedback. Because the independent manipulation of Ca2+-dependent Cl− currents in individual cones yielded results comparable to bath-applied GABA, it was concluded that activation of either Cl− current by itself is sufficient to reduce the size of HC feedback. However, additional effects of GABA on outer retinal processing cannot be excluded. These results can be accounted for by an ephaptic feedback model in which a cone Cl− current shunts the current flow in the synaptic cleft. The Ca2+-dependent Cl− current might be essential to set the initial balance between the feedforward and the feedback signals active in the cone HC synapse. It prevents that strong feedback from HCs to cones flood the cone with Ca2+. Modulation of the feedback strength by GABA might play a role during light/dark adaptation, adjusting the amount of negative feedback to the signal to noise ratio of the

Numerical simulation of energy equation with viscous dissipation for compressible flow over cones

International Nuclear Information System (INIS)

Asif, M.; Chughtai, I.R.

1998-01-01

A finite volume discretization technique has been used to solve the energy equation with viscous dissipation. The effects of viscous heat dissipation for Mach numbers 1.5 and 2.0, at an angle of attack of 0 degree, over sharp and blunt cones have been studied. Algebraic equations have been solved using line-by-line Tda method. Supersonic flow over cones has been analyzed and discussed with and without considering the viscous dissipation effects. It has been found that the effects of viscous dissipation increase with the increase in Mach number. Viscous dissipation affects the temperature distribution of the body. However, the temperature difference in these cases was insignificant. This may be due to the fact that these analysis have been done at 0 km altitude. (author)

Use of RI-cone penetrometer in clay foundations

International Nuclear Information System (INIS)

Mimura, Mamoru; Shibata, Toru; Shrivastava, A.K.

1993-01-01

RI cone penetrometer tests are carried out at four different sites. The foundation grounds discussed here mainly consist of clayey materials. The measured results by RI cone penetrometers are shown for Kyobashi, Hachirougata, Kurihama and Kinkai Bay site. According to comparison of water content and density profiles by RI cone measurement with the conventional testing results, RI cone penetrometers are proved to be versatile tools for site investigation. Settlement assessment by RI cone penetrometer is also discussed by exemplifying the embankment at Kinkai Bay site. Elasto-vis-coplastic finite element analysis correspondingly performed strongly supports the RI cone based assessment. Repeated use of RI cone penetrometer with the advance of construction enables us to assess the consolidation process of the clay foundation. (author)

Critical condition for the transformation from Taylor cone to cone-jet

International Nuclear Information System (INIS)

Wei Cheng; Zhao Yang; Gang Tie-Qiang; Chen Li-Jie

2014-01-01

An energy method is proposed to investigate the critical transformation condition from a Taylor cone to a cone-jet. Based on the kinetic theorem, the system power allocation and the electrohydrodynamics stability are discussed. The numerical results indicate that the energy of the liquid cone tip experiences a maximum value during the transformation. With the proposed jetting energy, we give the critical transformation condition under which the derivative of jetting energy with respect to the surface area is greater than or equal to the energy required to form a unit of new liquid surface

Poster — Thur Eve — 29: Characterization of Patient Immobilization for Head and Neck Cancer Treatment

International Nuclear Information System (INIS)

Courneyea, L; Mullins, J; Howard, M; Beltran, C; Brinkmann, D; Pafundi, D

2014-01-01

Purpose: Evaluate an immobilization system to determine its adequacy for the reduced margins required for proton therapy. Methods: Twelve head-and-neck cancer patients were immobilized for conventional photon radiotherapy and imaged with pre- and post-treatment cone beam CTs (CBCTs) for each treatment fraction. To quantify the patient positioning reproducibility, each CBCT was registered to the simulation CT offline. Registrations were performed using auto-match tools and a matching volume-of-interest (VOI) consisting of a 5mm expansion around the mandible, occipital bone, C1/C2 and C7/T1. For each registration, the bony anatomy in the VOI was evaluated for agreement with the simulation position using 3 and 5mm margins. Registrations were initially restricted to translational corrections. If the bony anatomy did not agree with the simulation position to within 3mm or 5mm, the auto-match was repeated with 3 additional rotational corrections. Intrafraction motion was calculated as the difference between the pre- and post-treatment CBCT matches. Results: Pre-treatment patient positioning agreed with the simulation CT to within 3mm/5mm for 62%/86% of fractions using translational matching and 84%/100% of fractions when rotations were included. Intrafraction motion averaged 1.1±0.8mm, with 12% of fractions having >2mm intrafraction motion. Post-treatment positioning accuracy was 57%/84% and 80%/100% for registrations without/with rotations. For the mandible, positioning accuracy dropped from 93% pre-treatment to 82% post-treatment. Conclusion: If rotational corrections are available, the immobilization system studied created reproducible patient positioning to within 3mm for 84% of fractions. However, intrafraction motion caused additional anatomy to fall outside the 3mm margin by the end of treatment

Poster — Thur Eve — 29: Characterization of Patient Immobilization for Head and Neck Cancer Treatment

Energy Technology Data Exchange (ETDEWEB)

Courneyea, L; Mullins, J; Howard, M; Beltran, C; Brinkmann, D; Pafundi, D [Mayo Clinic, Rochester, MN (United States)

2014-08-15

Purpose: Evaluate an immobilization system to determine its adequacy for the reduced margins required for proton therapy. Methods: Twelve head-and-neck cancer patients were immobilized for conventional photon radiotherapy and imaged with pre- and post-treatment cone beam CTs (CBCTs) for each treatment fraction. To quantify the patient positioning reproducibility, each CBCT was registered to the simulation CT offline. Registrations were performed using auto-match tools and a matching volume-of-interest (VOI) consisting of a 5mm expansion around the mandible, occipital bone, C1/C2 and C7/T1. For each registration, the bony anatomy in the VOI was evaluated for agreement with the simulation position using 3 and 5mm margins. Registrations were initially restricted to translational corrections. If the bony anatomy did not agree with the simulation position to within 3mm or 5mm, the auto-match was repeated with 3 additional rotational corrections. Intrafraction motion was calculated as the difference between the pre- and post-treatment CBCT matches. Results: Pre-treatment patient positioning agreed with the simulation CT to within 3mm/5mm for 62%/86% of fractions using translational matching and 84%/100% of fractions when rotations were included. Intrafraction motion averaged 1.1±0.8mm, with 12% of fractions having >2mm intrafraction motion. Post-treatment positioning accuracy was 57%/84% and 80%/100% for registrations without/with rotations. For the mandible, positioning accuracy dropped from 93% pre-treatment to 82% post-treatment. Conclusion: If rotational corrections are available, the immobilization system studied created reproducible patient positioning to within 3mm for 84% of fractions. However, intrafraction motion caused additional anatomy to fall outside the 3mm margin by the end of treatment.

Implementation of Tuy's cone-beam inversion formula

International Nuclear Information System (INIS)

Zeng, G.L.; Clack, R.; Gullberg, G.T.

1994-01-01

Tuy's cone-beam inversion formula was modified to develop a cone-beam reconstruction algorithm. The algorithm was implemented for a cone-beam vertex orbit consisting of a circle and two orthogonal lines. This orbit geometry satisfies the cone-beam data sufficiency condition and is easy to implement on commercial single photon emission computed tomography (SPECT) systems. The algorithm which consists of two derivative steps, one rebinning step, and one three-dimensional backprojection step, was verified by computer simulations and by reconstructing physical phantom data collected on a clinical SPECT system. The proposed algorithm gives equivalent results and is as efficient as other analytical cone-beam reconstruction algorithms. (Author)

Review on resonance cone fields

International Nuclear Information System (INIS)

Ohnuma, Toshiro.

1980-02-01

Resonance cone fields and lower hybrid heating are reviewed in this report. The resonance cone fields were reported by Fisher and Gould, and they proposed the use of the measurement of resonance cones and structure as a diagnostic tool to determine the plasma density and electron temperature in magnetoplasma. After the resonance cone, a wave-like disturbance persists. Ohnuma et al. have measured bending, reflection and ducting of resonance cones in detail. The thermal modes in inhomogeneous magnetoplasma were seen. The reflection of thermal mode near an electron plasma frequency layer and an insulating plate has been observed. The non-linear effects of resonance cones is reported. Monochromatic electron beam produces the noise of broad band whistler mode. Lower hybrid waves have been the subject of propagation from the edge of plasma to the lower hybrid layer. Linear lower hybrid waves were studied. The lower hybrid and ion acoustic waves radiated from a point source were observed. The parametric decay of finite-extent, cold electron plasma waves was studied. The lower hybrid cone radiated from a point source going along magnetic field lines was observed. Several experimental data on the lower hybrid heating in tokamak devices have been reported. The theories on resonance cones and lower hybrid waves are introduced in this report. (Kato, T.)

Discrimination of dementia with Lewy bodies from Alzheimer's disease using voxel-based morphometry of white matter by statistical parametric mapping 8 plus diffeomorphic anatomic registration through exponentiated Lie algebra.

Science.gov (United States)

Nakatsuka, Tomoya; Imabayashi, Etsuko; Matsuda, Hiroshi; Sakakibara, Ryuji; Inaoka, Tsutomu; Terada, Hitoshi

2013-05-01

The purpose of this study was to identify brain atrophy specific for dementia with Lewy bodies (DLB) and to evaluate the discriminatory performance of this specific atrophy between DLB and Alzheimer's disease (AD). We retrospectively reviewed 60 DLB and 30 AD patients who had undergone 3D T1-weighted MRI. We randomly divided the DLB patients into two equal groups (A and B). First, we obtained a target volume of interest (VOI) for DLB-specific atrophy using correlation analysis of the percentage rate of significant whole white matter (WM) atrophy calculated using the Voxel-based Specific Regional Analysis System for Alzheimer's Disease (VSRAD) based on statistical parametric mapping 8 (SPM8) plus diffeomorphic anatomic registration through exponentiated Lie algebra, with segmented WM images in group A. We then evaluated the usefulness of this target VOI for discriminating the remaining 30 DLB patients in group B from the 30 AD patients. Z score values in this target VOI obtained from VSRAD were used as the determinant in receiver operating characteristic (ROC) analysis. Specific target VOIs for DLB were determined in the right-side dominant dorsal midbrain, right-side dominant dorsal pons, and bilateral cerebellum. ROC analysis revealed that the target VOI limited to the midbrain exhibited the highest area under the ROC curves of 0.75. DLB patients showed specific atrophy in the midbrain, pons, and cerebellum. Midbrain atrophy demonstrated the highest power for discriminating DLB and AD. This approach may be useful for determining the contributions of DLB and AD pathologies to the dementia syndrome.

The measurement of proton stopping power using proton-cone-beam computed tomography

International Nuclear Information System (INIS)

Zygmanski, P.; Rabin, M.S.Z.; Gall, K.P.; Rosenthal, S.J.

2000-01-01

A cone-beam computed tomography (CT) system utilizing a proton beam has been developed and tested. The cone beam is produced by scattering a 160 MeV proton beam with a modifier that results in a signal in the detector system, which decreases monotonically with depth in the medium. The detector system consists of a Gd 2 O 2 S:Tb intensifying screen viewed by a cooled CCD camera. The Feldkamp-Davis-Kress cone-beam reconstruction algorithm is applied to the projection data to obtain the CT voxel data representing proton stopping power. The system described is capable of reconstructing data over a 16x16x16cm 3 volume into 512x512x512 voxels. A spatial and contrast resolution phantom was scanned to determine the performance of the system. Spatial resolution is significantly degraded by multiple Coulomb scattering effects. Comparison of the reconstructed proton CT values with x-ray CT derived proton stopping powers shows that there may be some advantage to obtaining stopping powers directly with proton CT. The system described suggests a possible practical method of obtaining this measurement in vivo. (author)

Understanding the cone scale in Cupressaceae: insights from seed-cone teratology in Glyptostrobus pensilis.

Science.gov (United States)

Dörken, Veit Martin; Rudall, Paula J

2018-01-01

Both wild-type and teratological seed cones are described in the monoecious conifer Glyptostrobus pensilis and compared with those of other Cupressaceae sensu lato and other conifers. Some Cupressaceae apparently possess a proliferation of axillary structures in their cone scales. In our interpretation, in Glyptostrobus each bract of both typical and atypical seed cones bears two descending accessory shoots, interpreted here as seed scales (ovuliferous scales). The primary seed scale is fertile and forms the ovules, the second is sterile and forms characteristic tooth-like structures. The bract and the two axillary seed scales are each supplied with a single distinct vascular bundle that enters the cone axis as a separate strand; this vasculature also characterises the descending accessory short shoots in the vegetative parts of the crown. In wild-type seed cones, the fertile seed scale is reduced to its ovules, and the ovules are always axillary. In contrast, the ovules of some of the teratological seed cones examined were located at the centre of the cone scale. An additional tissue found on the upper surface of the sterile lower seed scale is here interpreted as the axis of the fertile seed scale. Thus, the central position of the ovules can be explained by recaulescent fusion of the upper fertile and lower sterile seed scales. In several teratological cone scales, the ovules were enveloped by an additional sterile tissue that is uniseriate and represents an epidermal outgrowth of the fertile seed scale. Close to the ovules, the epidermis was detached from lower tissue and surrounded the ovule completely, except at the micropyle. These teratological features are potentially significant in understanding seed-cone homologies among extant conifers.

Renal cortical and medullary blood flow responses to altered NO availability in humans.

Science.gov (United States)

Damkjær, Mads; Vafaee, Manoucher; Møller, Michael L; Braad, Poul Erik; Petersen, Henrik; Høilund-Carlsen, Poul Flemming; Bie, Peter

2010-12-01

The objective of this study was to quantify regional renal blood flow in humans. In nine young volunteers on a controlled diet, the lower abdomen was CT-scanned, and regional renal blood flow was determined by positron emission tomography (PET) scanning using H(2)(15)O as tracer. Measurements were performed at baseline, during constant intravenous infusion of nitric oxide (NO) donor glyceryl nitrate and after intravenous injection of NO synthase inhibitor N(ω)-monomethyl-L-arginine (L-NMMA). Using the CT image, the kidney pole areas were delineated as volumes of interest (VOI). In the data analysis, tissue layers with a thickness of one voxel were eliminated stepwise from the external surface of the VOI (voxel peeling), and the blood flow subsequently was determined in each new, reduced VOI. Blood flow in the shrinking VOIs decreased as the number of cycles of voxel peeling increased. After 4-5 cycles, blood flow was not reduced further by additional voxel peeling. This volume-insensitive flow was measured to be 2.30 ± 0.17 ml·g tissue(-1)·min(-1) during the control period; it increased during infusion of glyceryl nitrate to 2.97 ± 0.18 ml·g tissue(-1)·min(-1) (P blood flow was 4.67 ± 0.31 ml·g tissue(-1)·min(-1) during control, unchanged by glyceryl nitrate, and decreased after L-NMMA [3.48 ± 0.23 ml·(g·min)(-1), P renal medullary region in which the measured blood flow is 1) low, 2) independent of reduction in the VOI, and 3) reactive to changes in systemic NO supply. The technique seems to provide indices of renal medullary blood flow in humans.

Dynamic contrast-enhanced micro-CT on mice with mammary carcinoma for the assessment of antiangiogenic therapy response

Energy Technology Data Exchange (ETDEWEB)

Eisa, Fabian [University of Erlangen-Nuremberg, Institute of Medical Physics, Erlangen (Germany); University of Erlangen-Nuremberg, Graduate School in Advanced Optical Technologies (SAOT), Erlangen (Germany); Brauweiler, Robert; Hupfer, Martin; Nowak, Tristan; Kalender, Willi A. [University of Erlangen-Nuremberg, Institute of Medical Physics, Erlangen (Germany); Lotz, Laura; Hoffmann, Inge; Dittrich, Ralf; Beckmann, Matthias W. [University of Erlangen-Nuremberg, OB/GYN, University Hospital Erlangen, Erlangen (Germany); Wachter, David [University Hospital Erlangen, Institute of Pathology, Erlangen (Germany); Jost, Gregor; Pietsch, Hubertus [Bayer Pharma AG, Berlin (Germany)

2012-04-15

To evaluate the potential of in vivo dynamic contrast-enhanced micro-computed tomography (DCE micro-CT) for the assessment of antiangiogenic drug therapy response of mice with mammary carcinoma. 20 female mice with implanted MCF7 tumours were split into control group and therapy group treated with a known effective antiangiogenic drug. All mice underwent DCE micro-CT for the 3D analysis of functional parameters (relative blood volume [rBV], vascular permeability [K], area under the time-enhancement curve [AUC]) and morphology. All parameters were determined for total, peripheral and central tumour volumes of interest (VOIs). Immunohistochemistry was performed to characterise tumour vascularisation. 3D dose distributions were determined. The mean AUCs were significantly lower in therapy with P values of 0.012, 0.007 and 0.023 for total, peripheral and central tumour VOIs. K and rBV showed significant differences for the peripheral (P{sub per}{sup K} = 0.032, P{sub per}{sup rBV} = 0.029), but not for the total and central tumour VOIs (P{sub total}{sup K} = 0.108, P{sub central}{sup K} = 0.246, P{sub total}{sup rBV} = 0.093, P{sub central}{sup rBV} = 0.136). Mean tumour volume was significantly smaller in therapy (P{sub in} {sub vivo} = 0.001, P{sub ex} {sub vivo} = 0.005). Histology revealed greater vascularisation in the controls and central tumour necrosis. Doses ranged from 150 to 300 mGy. This study indicates the great potential of DCE micro-CT for early in vivo assessment of antiangiogenic drug therapy response. (orig.)

Méthode analytique généralisée pour le calcul du coning. Nouvelle solution pour calculer le coning de gaz, d'eau et double coning dans les puits verticaux et horizontaux Generalized Analytical Method for Coning Calculation. New Solution to Calculation Both the Gas Coning, Water Coning and Dual Coning for Vertical and Horizontal Wells

Directory of Open Access Journals (Sweden)

Pietraru V.

2006-11-01

for a given coning height (hcw. First, how must be calculed using Equation 4. 2. - Calculating the height of the coning peak (hcw for a given watercut (fw. In a similar way, the GOR is calculated for gas coning. The correlations given above were developed while considering that the production flow rate is constant. However, application of the superposition principle can be used to apply the proposed methods to cases of variable flow rate, hence the following options that may be analyzed with this method. Constant oil flow rate : This option has a theoretical nature. It can be applied in practice only up to breakthrough. The watertut, which is insignificant up to breakthrough, effectively increases very quickly after breakthrough. Constant total liquid flow rate : This is the simplest variant in practise, especially when the wells are pumped. The oil flow rate decreases in time. Constant watercut : With a continuous decrease in the oil flow rate in time. This option can be used to optimize the cumulative oil produced. It is difficult to apply in practice, but it is the ideal variant. Production with decrease of the liquid flow rate in stages : This is an interesting combination, in practice, of the preceding two flow regimes. This regime consists of a succession of constant liquid flow ratestages with a decrease in the flow rate each time the fixed acceptable limit of the fw (or GOR is reached. The method proposed in this article is approximate because of the simplifying hypotheses introduced and because of :- the coning heights are calculated without taking the existence of perforations into consideration;- for high watercuts, the zero pressure-drop hypothesis in the aquifer has been retained, although it is not very realistic. The method has been checked, at least in the range between 1 and 10 to the power of 4 in adimensional time td, by comparison with :- production data,- laboratory experiments, - and numerical simulations. Data published for four wells [9, 10, 11

SU-E-J-231: Comparison of Delineation Variability of Soft Tissue Volume and Position in Head-And-Neck Between Two T1-Weighted Pulse Sequences Using An MR-Simulator with Immobilization

Energy Technology Data Exchange (ETDEWEB)

Wong, O; Lo, G; Yuan, J; Law, M; Ding, A; Cheng, K; Chan, K; Cheung, K; Yu, S [Hong Kong Sanatorium & Hospital, Hong Kong (Hong Kong)

2015-06-15

Purpose: There is growing interests in applying MR-simulator(MR-sim) in radiotherapy but MR images subject to hardware, patient and pulse sequence dependent geometric distortion that may potentially influence target definition. This study aimed to evaluate the influence on head-and-neck tissue delineation, in terms of positional and volumetric variability, of two T1-weighted(T1w) MR sequences on a 1.5T MR-sim Methods: Four healthy volunteers were scanned (4 scans for each on different days) using both spin-echo (3DCUBE, TR/TE=500/14ms, TA=183s) and gradient-echo sequences (3DFSPGR, TE/TR=7/4ms, TA=173s) with identical coverage, voxel-size(0.8×0.8×1.0mm3), receiver-bandwidth(62.5kHz/pix) and geometric correction on a 1.5T MR-sim immobilized with personalized thermoplastic cast and head-rest. Under this setting, similar T1w contrast and signal-to-noise ratio were obtained, and factors other than sequence that might bias image distortion and tissue delineation were minimized. VOIs of parotid gland(PGR, PGL), pituitary gland(PIT) and eyeballs(EyeL, EyeR) were carefully drawn, and inter-scan coefficient-of-variation(CV) of VOI centroid position and volume were calculated for each subject. Mean and standard deviation(SD) of the CVs for four subjects were compared between sequences using Wilcoxon ranksum test. Results: The mean positional(<4%) and volumetric(<7%) CVs varied between tissues, majorly dependent on tissue inherent properties like volume, location, mobility and deformability. Smaller mean volumetric CV was found in 3DCUBE, probably due to its less proneness to tissue susceptibility, but only PGL showed significant difference(P<0.05). Positional CVs had no significant differences for all VOIs(P>0.05) between sequences, suggesting volumetric variation might be more sensitive to sequence-dependent delineation difference. Conclusion: Although 3DCUBE is considered less prone to tissue susceptibility-induced artifact and distortion, our preliminary data showed

X-treme CT analysis of cancellous bone at the rotator cuff insertion in human individuals with osteoporosis: superficial versus deep quality.

Science.gov (United States)

Kirchhoff, Chlodwig; Kirchhoff, Sonja; Sprecher, Christoph M; Ahrens, Philipp; Imhoff, Andreas B; Hinterwimmer, Stefan; Milz, Stefan; Braunstein, Volker

2013-03-01

Rotator cuff (RC) repair-especially in the elderly population-is problematic since the patients suffer to a high extent from bone mineral density loss at the reattachment site. Therefore, the study was primarily driven by the question whether it is possible to reach more or qualitatively better cancellous bone and thus a more stable postoperative result if anchors with greater length are used for RC repair and/or the conventional anchors are screwed deeper into the bone. In anatomical terms, the question is raised whether cancellous bone is of better quality close to or far off the RC enthesis. Axial HRqCT scans (X-tremeCT, Scanco Medical) of 36 human cadaveric humeral heads (75 ± 11 years) were performed to determine the ratio of bone volume to total volume (BV/TV), trabecular thickness (Trab Th), number of trabecles (Trab N), trabecular separation (Trab Sp) as well as non-metric indices such as connectivity density (Conn Dens) and structure model index (SMI). Within the greater tuberosity (GT), 6 volumes of interest (VOI) (A1, B1, C1, A2, B2, C2), in the lesser tuberosity (LT) 2 VOIs (D1, D2) and one control VOI in the subchondral bone were set. The analyzed bone cylinder of each VOI was divided into a superficial and a deep portion. The parameters BV/TV, Trab N, Trab Th and Conn Dens in all volumes of the GT and LT revealed higher values in the superficial portion reaching different levels of significance (p significance for the non-metric parameter SMI in no volume of the GT/LT, although the higher values were found superficially. Our data show that cancellous bone presents with decreasing bone quality when analyzing increasingly deeper portions of the bone cylinders of the GT and LT starting at the articular surface. This information seems to be crucial for shoulder surgeons, especially when treating elderly patients. Our results clearly prove that screwing in anchors to a deeper extent will not improve stability, since the deeper bone stock is of worse

Understanding the cone scale in Cupressaceae: insights from seed-cone teratology in Glyptostrobus pensilis

Directory of Open Access Journals (Sweden)

Veit Martin Dörken

2018-06-01

Full Text Available Both wild-type and teratological seed cones are described in the monoecious conifer Glyptostrobus pensilis and compared with those of other Cupressaceae sensu lato and other conifers. Some Cupressaceae apparently possess a proliferation of axillary structures in their cone scales. In our interpretation, in Glyptostrobus each bract of both typical and atypical seed cones bears two descending accessory shoots, interpreted here as seed scales (ovuliferous scales. The primary seed scale is fertile and forms the ovules, the second is sterile and forms characteristic tooth-like structures. The bract and the two axillary seed scales are each supplied with a single distinct vascular bundle that enters the cone axis as a separate strand; this vasculature also characterises the descending accessory short shoots in the vegetative parts of the crown. In wild-type seed cones, the fertile seed scale is reduced to its ovules, and the ovules are always axillary. In contrast, the ovules of some of the teratological seed cones examined were located at the centre of the cone scale. An additional tissue found on the upper surface of the sterile lower seed scale is here interpreted as the axis of the fertile seed scale. Thus, the central position of the ovules can be explained by recaulescent fusion of the upper fertile and lower sterile seed scales. In several teratological cone scales, the ovules were enveloped by an additional sterile tissue that is uniseriate and represents an epidermal outgrowth of the fertile seed scale. Close to the ovules, the epidermis was detached from lower tissue and surrounded the ovule completely, except at the micropyle. These teratological features are potentially significant in understanding seed-cone homologies among extant conifers.

Singularities of plane complex curves and limits of Kähler metrics with cone singularities. I: Tangent Cones

Directory of Open Access Journals (Sweden)

Borbon Martin de

2017-02-01

Full Text Available The goal of this article is to provide a construction and classification, in the case of two complex dimensions, of the possible tangent cones at points of limit spaces of non-collapsed sequences of Kähler-Einstein metrics with cone singularities. The proofs and constructions are completely elementary, nevertheless they have an intrinsic beauty. In a few words; tangent cones correspond to spherical metrics with cone singularities in the projective line by means of the Kähler quotient construction with respect to the S1-action generated by the Reeb vector field, except in the irregular case ℂβ₁×ℂβ₂ with β₂/ β₁ ∉ Q.

High-Chern-number bands and tunable Dirac cones in beta-graphyne

NARCIS (Netherlands)

van Miert, Guido; Smith, Cristiane Morais; Juricic, Vladimir

2014-01-01

Graphynes represent an emerging family of carbon allotropes that recently attracted much interest due to the tunability of the Dirac cones in the band structure. Here, we show that the spin-orbit couplings in beta-graphyne could produce various effects related to the topological properties of its

Intensity-Modulated Radiotherapy With Use of Cone-Down Boost for Pediatric Head-and-Neck Rhabdomyosarcoma

International Nuclear Information System (INIS)

McDonald, Mark W.; Esiashvili, Natia; George, Bradley A.; Katzenstein, Howard M.; Olson, Thomas A.; Rapkin, Louis B.; Marcus, Robert B.

2008-01-01

Purpose: To report our initial experience using intensity-modulated radiotherapy (IMRT) with a cone-down boost for pediatric head-and-neck rhabdomyosarcoma (RMS). Methods and Materials: A review of institutional treatment records identified children treated with IMRT for head-and-neck RMS between January 2000 and February 2007. All patients had undergone chemotherapy according to cooperative group RMS protocols. The initial planning target volume (PTV) covered the prechemotherapy tumor extent with variable margins, generally 1-2 cm. The boost PTV covered the postchemotherapy tumor volume, usually with a margin of 0.5-1 cm. Results: A total of 20 patients were treated with IMRT for head-and-neck RMS. Of these 20 patients, 4 had Group II, 15 Group III, and 1 Group IV disease. The site was parameningeal in 12, nonparameningeal in 6, and orbit primary in 2. Of the 20 patients, 14 were treated with a cone-down boost after a median dose of 36 Gy (range, 30-45.6). The mean initial PTV was 213.5 cm 3 , and the mean boost PTV was 76.9 cm 3 . Patients received a median total dose of 50.4 Gy. The median follow-up time was 29 months. The 3-year Kaplan-Meier local control rate was 100%, although 1 patient developed an in-field recurrence 50 months after IMRT. The 3-year event-free survival rate, overall survival rate, and risk of central nervous system failure was 74%, 76%, and 7%, respectively. Conclusions: Our preliminary follow-up of pediatric head-and-neck RMS patients treated with IMRT revealed excellent local control. The initial targeting of the prechemotherapy tumor volume with 1-2-cm margin to 30.6 or 36 Gy followed by a cone-down boost to the postchemotherapy tumor volume with a 0.5-1-cm margin allowed for significant sparing of normal tissues and provided good local control

Quantification of {sup 18}F-FDG PET images using probabilistic brain atlas: clinical application in temporal lobe epilepsy patients

Energy Technology Data Exchange (ETDEWEB)

Kang, Keon Wook; Lee, Dong Soo; Cho, Jae Hoon; Lee, Jae Sung; Yeo, Jeong Seok; Lee, Sang Gun; Chung, June Key; Lee, Myung Chul [Seoul National Univ., Seoul (Korea, Republic of)

2000-07-01

A probabilistic atlas of the human brain (Statistical Probability Anatomical Maps: SPAM) was developed by the international consortium for brain mapping (ICBM). After calculating the counts in volume of interest (VOI) using the product of probability of SPAM images and counts in FDG images, asymmetric indexes(AI) were calculated and used for finding epileptogenic zones in temporal lobe epilepsy (TLE). FDG PET images from 28 surgically confirmed TLE patients and 12 age-matched controls were spatially normalized to the averaged brain MRI atlas of ICBM. The counts from normalized PET images were multiplied with the probability of 12 VOIs (superior temporal gyrus, middle temporal gyrus, inferior temporal gyrus, hippocampus, parahippocampal gyrus, and amygdala in each hemisphere) of SPAM images of Montreal Neurological Institute. Finally AI was calculated on each pair of VOI, and compared with visual assessment. If AI was deviated more than 2 standard deviation of normal controls, we considered epileptogenic zones were found successfully. The counts of VOIs in normal controls were symmetric (AI <6%, paired t-test p>0.05) except those of inferior temporal gyrus (p<0.01). AIs in 5 pairs of VOI excluding inferior temporal gyrus were deviated to one side in TLE (p<0.05). Lateralization was correct in 23/28 of patients by AI, but all of 28 were consistent with visual inspection. In 3 patients with normal AI was symmetric on visual inspection. In 2 patients falsely lateralized using AI, metabolism was also decreased visually on contra-lateral side. Asymmetric index obtained by the product of statistical probability anatomical map and FDG PET correlated well with visual assessment in TLE patients. SPAM is useful for quantification of VOIs in functional images.

Measuring the apparent diffusion coefficient in primary rectal tumors: is there a benefit in performing histogram analyses?

Science.gov (United States)

van Heeswijk, Miriam M; Lambregts, Doenja M J; Maas, Monique; Lahaye, Max J; Ayas, Z; Slenter, Jos M G M; Beets, Geerard L; Bakers, Frans C H; Beets-Tan, Regina G H

2017-06-01

The apparent diffusion coefficient (ADC) is a potential prognostic imaging marker in rectal cancer. Typically, mean ADC values are used, derived from precise manual whole-volume tumor delineations by experts. The aim was first to explore whether non-precise circular delineation combined with histogram analysis can be a less cumbersome alternative to acquire similar ADC measurements and second to explore whether histogram analyses provide additional prognostic information. Thirty-seven patients who underwent a primary staging MRI including diffusion-weighted imaging (DWI; b0, 25, 50, 100, 500, 1000; 1.5 T) were included. Volumes-of-interest (VOIs) were drawn on b1000-DWI: (a) precise delineation, manually tracing tumor boundaries (2 expert readers), and (b) non-precise delineation, drawing circular VOIs with a wide margin around the tumor (2 non-experts). Mean ADC and histogram metrics (mean, min, max, median, SD, skewness, kurtosis, 5th-95th percentiles) were derived from the VOIs and delineation time was recorded. Measurements were compared between the two methods and correlated with prognostic outcome parameters. Median delineation time reduced from 47-165 s (precise) to 21-43 s (non-precise). The 45th percentile of the non-precise delineation showed the best correlation with the mean ADC from the precise delineation as the reference standard (ICC 0.71-0.75). None of the mean ADC or histogram parameters showed significant prognostic value; only the total tumor volume (VOI) was significantly larger in patients with positive clinical N stage and mesorectal fascia involvement. When performing non-precise tumor delineation, histogram analysis (in specific 45th ADC percentile) may be used as an alternative to obtain similar ADC values as with precise whole tumor delineation. Histogram analyses are not beneficial to obtain additional prognostic information.

Micro-morphologic changes around biophysically-stimulated titanium implants in ovariectomized rats

Directory of Open Access Journals (Sweden)

Chang Ting-Ling

2007-07-01

Full Text Available Abstract Background Osteoporosis may present a risk factor in achievement of osseointegration because of its impact on bone remodeling properties of skeletal phsiology. The purpose of this study was to evaluate micro-morphological changes in bone around titanium implants exposed to mechanical and electrical-energy in osteoporotic rats. Methods Fifteen 12-week old sprague-dowley rats were ovariectomized to develop osteoporosis. After 8 weeks of healing period, two titanium implants were bilaterally placed in the proximal metaphyses of tibia. The animals were randomly divided into a control group and biophysically-stimulated two test groups with five animals in each group. In the first test group, a pulsed electromagnetic field (PEMF stimulation was administrated at a 0.2 mT 4 h/day, whereas the second group received low-magnitude high-frequency mechanical vibration (MECHVIB at 50 Hz 14 min/day. Following completion of two week treatment period, all animals were sacrificed. Bone sites including implants were sectioned, removed en bloc and analyzed using a microCT unit. Relative bone volume and bone micro-structural parameters were evaluated for 144 μm wide peri-implant volume of interest (VOI. Results Mean relative bone volume in the peri-implant VOI around implants PEMF and MECHVIB was significantly higher than of those in control (P P > .05 while the difference in trabecular-number among test and control groups was significant in all VOIs (P Conclusion Biophysical stimulation remarkably enhances bone volume around titanium implants placed in osteoporotic rats. Low-magnitude high-frequency MECHVIB is more effective than PEMF on bone healing in terms of relative bone volume.

The oldest example of compound interest in Sumer: Seventh power of four-thirds

OpenAIRE

Muroi, Kazuo

2015-01-01

In the present paper I shall clarify that the origin of compound interest goes back 4400 years to Sumer by showing the Sumerian scribe of Enmetena Foundation Cone calculated seventh power of four-thirds.

The influence of target and patient characteristics on the volume obtained from cone beam CT in lung stereotactic body radiation therapy

International Nuclear Information System (INIS)

Liu, Hong-Wei; Khan, Rao; D’Ambrosi, Rafael; Krobutschek, Krista; Nugent, Zoann; Lau, Harold

2013-01-01

Purpose: To investigate the influence of tumor and patient characteristics on the target volume obtained from cone beam CT (CBCT) in lung stereotactic body radiation therapy (SBRT). Materials and methods: For a given cohort of 71 patients, the internal target volume (ITV) in CBCT obtained from four different datasets was compared with a reference ITV drawn on a four-dimensional CT (4DCT). The significance of the tumor size, location, relative target motion (RM) and patient’s body mass index (BMI) and gender on the adequacy of ITV obtained from CBCT was determined. Results: The median ITV-CBCT was found to be smaller than the ITV-4DCT by 11.8% (range: −49.8 to +24.3%, P < 0.001). Small tumors located in the lower lung were found to have a larger RM than large tumors in the upper lung. Tumors located near the central lung had high CT background which reduced the target contrast near the edges. Tumor location close to center vs. periphery was the only significant factor (P = 0.046) causing underestimation of ITV in CBCT, rather than RM (P = 0.323) and other factors. Conclusions: The current clinical study has identified that the location of tumor is a major source of discrepancy between ITV-CBCT and ITV-4DCT for lung SBRT

Quantitative Evaluation of Segmentation- and Atlas-Based Attenuation Correction for PET/MR on Pediatric Patients.

Science.gov (United States)

Bezrukov, Ilja; Schmidt, Holger; Gatidis, Sergios; Mantlik, Frédéric; Schäfer, Jürgen F; Schwenzer, Nina; Pichler, Bernd J

2015-07-01

Pediatric imaging is regarded as a key application for combined PET/MR imaging systems. Because existing MR-based attenuation-correction methods were not designed specifically for pediatric patients, we assessed the impact of 2 potentially influential factors: inter- and intrapatient variability of attenuation coefficients and anatomic variability. Furthermore, we evaluated the quantification accuracy of 3 methods for MR-based attenuation correction without (SEGbase) and with bone prediction using an adult and a pediatric atlas (SEGwBONEad and SEGwBONEpe, respectively) on PET data of pediatric patients. The variability of attenuation coefficients between and within pediatric (5-17 y, n = 17) and adult (27-66 y, n = 16) patient collectives was assessed on volumes of interest (VOIs) in CT datasets for different tissue types. Anatomic variability was assessed on SEGwBONEad/pe attenuation maps by computing mean differences to CT-based attenuation maps for regions of bone tissue, lungs, and soft tissue. PET quantification was evaluated on VOIs with physiologic uptake and on 80% isocontour VOIs with elevated uptake in the thorax and abdomen/pelvis. Inter- and intrapatient variability of the bias was assessed for each VOI group and method. Statistically significant differences in mean VOI Hounsfield unit values and linear attenuation coefficients between adult and pediatric collectives were found in the lungs and femur. The prediction of attenuation maps using the pediatric atlas showed a reduced error in bone tissue and better delineation of bone structure. Evaluation of PET quantification accuracy showed statistically significant mean errors in mean standardized uptake values of -14% ± 5% and -23% ± 6% in bone marrow and femur-adjacent VOIs with physiologic uptake for SEGbase, which could be reduced to 0% ± 4% and -1% ± 5% using SEGwBONEpe attenuation maps. Bias in soft-tissue VOIs was less than 5% for all methods. Lung VOIs showed high SDs in the range of 15% for

Brain regional α-[11C]methyl-L-tryptophan trapping, used as an index of 5-HT synthesis, in healthy adults: absence of an age effect

International Nuclear Information System (INIS)

Rosa-Neto, Pedro; Benkelfat, Chawki; Leyton, Marco; Sakai, Yojiro; Morais, Jose A.; Diksic, Mirko

2007-01-01

Previous functional neuroimaging studies suggest that selective aspects of the brain serotonin (5-HT) system change during the aging process. Here, we assessed the effects of aging on the brain regional α-[ 11 C]methyl-L-tryptophan (α-[ 11 C]MTrp) trapping rate constant (K*; μl.g -1 .min -1 ), which, with certain assumptions, could be taken as a proxy of 5-HT synthesis. Thirty-six healthy right-handed subjects had positron emission tomography (PET) scans following injection with α-[ 11 C]MTrp [18 males aged 46.6 ± 22.2 years (range 20-80 years) and 18 females aged 33.0 ± 15.5 years (range 20-80 years)]. The trapping rate constant, K*, was calculated with the graphical method for irreversible ligands using the sinus-venous input function. A priori selected volumes of interest (VOIs) were defined using an automatic algorithm. VOI analysis showed no correlation between age and brain regional K* values. As reported by others, significant age-related reductions of gray matter were observed in the thalamus and frontal and cingulate cortices; even with partial volume correction there was still no significant relationship between K* and age. Further exploratory SPM voxelwise correlation between age and α-[ 11 C]MTrp trapping, using p = 0.05 (uncorrected), as well as voxel-based morphometry, was in agreement with the VOI analysis. The dissociation between age-related changes in brain anatomy and this index of serotonin synthesis suggests independent mechanisms underlying the normal aging process. (orig.)

Cone-beam CT angiography of the thorax. An experimental study

International Nuclear Information System (INIS)

Yoshida, Katsuya; Shimada, Kazuhiro; Tadokoro, Hiroyuki

1999-01-01

The authors recently developed a cone-beam computed tomography (CT) scanner and this report presents their evaluation of its potential for thoracic vascular imaging. An X-ray tube and a video-fluoroscopic system were rotated around the objects and 360 projected images were collected in a 12-s scan. Each image was digitized and a 3 dimensional (D) image (256 x 256 x 256 voxel volume with a voxel dimension of 0.9 x 0.9 x 0.9 mm) was reconstructed. Two different 3D-CT angiographies were investigated in 2 pigs: right atriography and thoracic aortography. Each pig was anesthetized, mechanically ventilated and positioned within the scanner. Contrast agent was infused through the right atrium or the aortic root at a rate of 3 ml/s during the scan. The right atriography scan clearly delineated the anatomy of the pulmonary artery, heart chambers and thoracic aorta. The thoracic aortography scan also clearly delineated the aortic anatomy including the internal thoracic and intercostal arteries. In conclusion, cone-beam CT angiography is potentially useful for thoracic vascular imaging. (author)

QCD on the light cone

International Nuclear Information System (INIS)

Brodsky, S.J.

1992-09-01

The quantization of gauge theory at fixed light-cone time τ = t - z/c provides new perspectives for solving non-perturbative problems in quantum chromodynamics. The light-cone Fock state expansion provides both a precise definition of the relativistic wavefunctions of hadrons as bound-states of quarks and gluons and a general calculus for predicting QCD processes at the amplitude level. Applications to exclusive processes and weak decay amplitudes are discussed. The problem of computing the hadronic spectrum and the corresponding light-cone wavefunctions of QCD in one space and one time dimension has been successfully reduced to the diagonalization of a discrete representation of the light-cone Hamiltonian. The problems confronting the solution of gauge theories in 3 + 1 dimensions in the light-cone quantization formalism,, including zero modes and non-perturbative renormalization, are reviewed

Cone photoreceptor structure in patients with x-linked cone dysfunction and red-green color vision deficiency

DEFF Research Database (Denmark)

Patterson, Emily J.; Wilk, Melissa; Langlo, Christopher S.

2016-01-01

encoded by exon 4, and two with a novel insertion in exon 2. Foveal cone structure and retinal thickness was disrupted to a variable degree, even among related individuals with the same L/M array. CONCLUSIONS. Our findings provide a direct link between disruption of the cone mosaic and L/ M opsin variants......PURPOSE. Mutations in the coding sequence of the L and M opsin genes are often associated with X-linked cone dysfunction (such as Bornholm Eye Disease, BED), though the exact color vision phenotype associated with these disorders is variable. We examined individuals with L/ M opsin gene mutations...... to clarify the link between color vision deficiency and cone dysfunction.  METHODS. We recruited 17 males for imaging. The thickness and integrity of the photoreceptor layers were evaluated using spectral-domain optical coherence tomography. Cone density was measured using high-resolution images of the cone...

Three-dimensional evaluation of pharyngeal airway in individuals with varying growth patterns using cone beam computed tomography

OpenAIRE

Rohan Diwakar; Maninder Singh Sidhu; Mona Prabhakar; Seema Grover; Ritu Phogat

2015-01-01

Introduction: The purpose of this study was to evaluate the pharyngeal airway volume in individuals with different vertical growth patterns. Methods: Cone beam computed tomography scans were evaluated of 40 subjects with the age range from 14 to 25 years and were divided into three groups. Horizontal growers consisted of 13 subjects, normal growers consisted of 14 subjects, and the vertical growers consisted of 13 subjects. The pharyngeal airway volume was measured using In Vivo Dental 5.1 so...

NMNAT1 variants cause cone and cone-rod dystrophy.

Science.gov (United States)

Nash, Benjamin M; Symes, Richard; Goel, Himanshu; Dinger, Marcel E; Bennetts, Bruce; Grigg, John R; Jamieson, Robyn V

2018-03-01

Cone and cone-rod dystrophies (CD and CRD, respectively) are degenerative retinal diseases that predominantly affect the cone photoreceptors. The underlying disease gene is not known in approximately 75% of autosomal recessive cases. Variants in NMNAT1 cause a severe, early-onset retinal dystrophy called Leber congenital amaurosis (LCA). We report two patients where clinical phenotyping indicated diagnoses of CD and CRD, respectively. NMNAT1 variants were identified, with Case 1 showing an extremely rare homozygous variant c.[271G > A] p.(Glu91Lys) and Case 2 compound heterozygous variants c.[53 A > G];[769G > A] p.(Asn18Ser);(Glu257Lys). The detailed variant analysis, in combination with the observation of an associated macular atrophy phenotype, indicated that these variants were disease-causing. This report demonstrates that the variants in NMNAT1 may cause CD or CRD associated with macular atrophy. Genetic investigations of the patients with CD or CRD should include NMNAT1 in the genes examined.

Serotonin transporter binding in the hypothalamus correlates negatively with tonic heat pain ratings in healthy subjects: A [11C]DASB PET study

DEFF Research Database (Denmark)

Kupers, Ron; Frokjaer, Vibe G.; Erritzoe, David

2010-01-01

There is a large body of evidence that the serotonergic system plays an important role in the transmission and regulation of pain. Here we used positron emission tomography (PET) with the serotonin transporter (SERT) tracer [11C]DASB to study the relationship between SERT binding in the brain and....... The negative correlation between SERT binding in the hypothalamus and insula with tonic pain ratings suggests a possible serotonergic control of the role of these areas in the modulation or in the affective appreciation of pain.......) tonic noxious heat stimulus. PET data were analyzed using both volume-of-interest (VOI) and voxel-based approaches. VOI analysis revealed a significant negative correlation between tonic pain ratings and SERT binding in the hypothalamus (r = −0.59; p = 0.008), a finding confirmed by the parametric...... analysis. The parametric analysis also revealed a negative correlation between tonic pain ratings and SERT binding in the right anterior insula. Measures of regional SERT binding did not correlate with pain threshold or with responses to short phasic suprathreshold phasic heat stimuli. Finally, the VOI...

Non-uniform versus uniform attenuation correction in brain perfusion SPET of healthy volunteers

International Nuclear Information System (INIS)

Van Laere, K.; Versijpt, J.; Dierckx, R.; Koole, M.

2001-01-01

Although non-uniform attenuation correction (NUAC) can supply more accurate absolute quantification, it is not entirely clear whether NUAC provides clear-cut benefits in the routine clinical practice of brain SPET imaging. The aim of this study was to compare the effect of NUAC versus uniform attenuation correction (UAC) on volume of interest (VOI)-based semi-quantification of a large age- and gender-stratified brain perfusion normal database. Eighty-nine healthy volunteers (46 females and 43 males, aged 20-81 years) underwent standardised high-resolution single-photon emission tomography (SPET) with 925 MBq 99m Tc-ethyl cysteinate dimer (ECD) on a Toshiba GCA-9300A camera with 153 Gd or 99m Tc transmission CT scanning. Emission images were reconstructed by filtered back-projection and scatter corrected using the triple-energy window correction method. Both non-uniform Chang attenuation correction (one iteration) and uniform Sorenson correction (attenuation coefficient 0.09 cm -1 ) were applied. Images were automatically re-oriented to a stereotactic template on which 35 predefined VOIs were defined for semi-quantification (normalisation on total VOI counts). Small but significant differences between relative VOI uptake values for NUAC versus UAC in the infratentorial region were found. VOI standard deviations were significantly smaller for UAC, 4.5% (range 2.6-7.5), than for NUAC, 5.0% (2.3-9.0) (P 99m Tc-ECD uptake values in healthy volunteers to those obtained with NUAC, although values for the infratentorial region are slightly lower. NUAC produces a slight increase in inter-subject variability. Further study is necessary in various patient populations to establish the full clinical impact of NUAC in brain perfusion SPET. (orig.)

Strain engineering of Dirac cones in graphyne

Energy Technology Data Exchange (ETDEWEB)

Wang, Gaoxue; Kumar, Ashok; Pandey, Ravindra, E-mail: pandey@mtu.edu [Department of Physics, Michigan Technological University, Houghton, Michigan 49931 (United States); Si, Mingsu [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

2014-05-26

6,6,12-graphyne, one of the two-dimensional carbon allotropes with the rectangular lattice structure, has two kinds of non-equivalent anisotropic Dirac cones in the first Brillouin zone. We show that Dirac cones can be tuned independently by the uniaxial compressive strain applied to graphyne, which induces n-type and p-type self-doping effect, by shifting the energy of the Dirac cones in the opposite directions. On the other hand, application of the tensile strain results into a transition from gapless to finite gap system for the monolayer. For the AB-stacked bilayer, the results predict tunability of Dirac-cones by in-plane strains as well as the strain applied perpendicular to the plane. The group velocities of the Dirac cones show enhancement in the resistance anisotropy for bilayer relative to the case of monolayer. Such tunable and direction-dependent electronic properties predicted for 6,6,12-graphyne make it to be competitive for the next-generation electronic devices at nanoscale.

Region-of-interest imaging in cone beam computerized tomography

International Nuclear Information System (INIS)

Tam, K.C.

1996-01-01

Imaging a sectional region within an object with a detector just big enough to cover the sectional region-of-interest is analyzed. We show that with some suitable choice of scanning configuration and with an innovative method of data combination, all the Radon data can be obtained accurately. The algorithm is mathematically exact, and requires no iterations and no additional measurements. The method can be applied to inspect portions of large industrial objects in industrial imaging, as well as to image portions of human bodies in medical diagnosis

Mach cones in space and laboratory dusty magnetoplasmas

International Nuclear Information System (INIS)

Mamun, A.A.; Shukla, P.K

2004-07-01

We present a rigorous theoretical investigation on the possibility for the formation of Mach cones in both space and laboratory dusty magnetoplasmas. We find the parametric regimes for which different types of Mach cones, such as dust acoustic Mach cones, dust magneto-acoustic Mach cones, oscillonic Mach cones, etc. are formed in space and laboratory dusty magnetoplasmas. We also identify the basic features of such different classes of Mach cones (viz. dust- acoustic, dust magneto-acoustic, oscillonic Mach cones, etc.), and clearly explain how they are relevant to space and laboratory dusty manetoplasmas. (author)

Quantification of organ motion during chemoradiotherapy of rectal cancer using cone-beam computed tomography.

LENUS (Irish Health Repository)

Chong, Irene

2011-11-15

There has been no previously published data related to the quantification of rectal motion using cone-beam computed tomography (CBCT) during standard conformal long-course chemoradiotherapy. The purpose of the present study was to quantify the interfractional changes in rectal movement and dimensions and rectal and bladder volume using CBCT and to quantify the bony anatomy displacements to calculate the margins required to account for systematic (Σ) and random (σ) setup errors.

The discovery of the growth cone and its influence on the study of axon guidance

Directory of Open Access Journals (Sweden)

Elisa eTamariz

2015-05-01

Full Text Available For over a century, there has been a great deal of interest in understanding how neural connectivity is established during development and regeneration. Interest in the latter arises from the possibility that knowledge of this process can be used to reestablish lost connections after lesion or neurodegeneration. At the end of the XIX century, Santiago Ramón y Cajal discovered that the distal tip of growing axons contained a structure that he called the growth cone. He proposed that this structure enabled the axon’s oriented growth in response to attractants, now known as chemotropic molecules. He further proposed that the physical properties of the surrounding tissues could influence the growth cone and the direction of growth. This seminal discovery afforded a plausible explanation for directed axonal growth and has led to the discovery of axon guidance mechanisms that include diffusible attractants and repellants and guidance cues anchored to cell membranes or extracellular matrix. In this review the major events in the development of this field are discussed.

Demise of light cone field theory

International Nuclear Information System (INIS)

Hagen, C.R.

1977-01-01

It is shown that the massive spin one-half field is noncovariant in two dimensional light cone coordinates. It is shown that spin one-half is noncovariant in four dimensions as well. It is concluded that since the case of the spin one-half field is an absolute necessity if one is to build a world containing fermions. It seems safe to infer that light cone quantization cannot be useful in the quark binding problem as currently conceived. It is suggested that further work on light cone quantization be focused solely upon the questions of consistency as discussed rather than on applications to model building. 9 references

Ordered cones and approximation

CERN Document Server

Keimel, Klaus

1992-01-01

This book presents a unified approach to Korovkin-type approximation theorems. It includes classical material on the approximation of real-valuedfunctions as well as recent and new results on set-valued functions and stochastic processes, and on weighted approximation. The results are notonly of qualitative nature, but include quantitative bounds on the order of approximation. The book is addressed to researchers in functional analysis and approximation theory as well as to those that want to applythese methods in other fields. It is largely self- contained, but the readershould have a solid background in abstract functional analysis. The unified approach is based on a new notion of locally convex ordered cones that are not embeddable in vector spaces but allow Hahn-Banach type separation and extension theorems. This concept seems to be of independent interest.

Clinical Course, Genetic Etiology, and Visual Outcome in Cone and Cone-Rod Dystrophy

NARCIS (Netherlands)

Thiadens, Alberta A. H. J.; Phan, T. My Lan; Zekveld-Vroon, Renate C.; Leroy, Bart P.; van den Born, L. Ingeborgh; Hoyng, Carel B.; Klaver, Caroline C. W.; Roosing, Susanne; Pott, Jan-Willem R.; van Schooneveld, Mary J.; van Moll-Ramirez, Norka; van Genderen, Maria M.; Boon, Camiel J. F.; den Hollander, Anneke I.; Bergen, Arthur A. B.; De Baere, Elfride; Cremers, Frans P. M.; Lotery, Andrew J.

Objective: To evaluate the clinical course, genetic etiology, and visual prognosis in patients with cone dystrophy (CD) and cone-rod dystrophy (CRD). Design: Clinic-based, longitudinal, multicenter study. Participants: Consecutive probands with CD (N = 98), CRD (N = 83), and affected relatives (N =

Prognostic value of defining the systemic tumor volume with FDG-PET in diffuse large b cell lymphoma

International Nuclear Information System (INIS)

Byun, Byung Hyun; Lim, Sang Moo; Cheon, Gi Jeong; Choi, Chang Woon; Kang, Hye Jin; Na, Im Il; Ryoo, Baek Yeol; Yang, Sung Hyun

2007-01-01

We measured the systemic tumor volume using FDG-PET in patients with diffuse large B cell lymphoma (DLBL). We also investigated its prognostic role, and compared it with that of other prognostic factors. FDG PET was performed in 38 newly diagnosed DLBL patients (20 men, 18 women, age 55.715.1 years) at pre-treatment of chemotherapy. Clinical staging of lymphoma was evaluated by Ann Arbor system. On each FDG PET scan, we acquired volume of interest (VOl) at the cut-off value of SUV=2.5 in every measurable tumor by the automatic edge detection software. According to the VOI, we measured the metabolic volume and mean SUV, and estimated volume-activity indexes (SUV Vol) as mean SUV times metabolic volume. And then, we calculated the summed metabolic volume (VOLsum) and summed SUV Vol (SUV Volsum) in every FDG PET scan. Maximum SUV of involved lesion (SUVmax) was also acquired on each FDG PET scan. Time to treatment failure (TTF) was compared among VOLsum (median), SUV Volsum (median), SUVmax (median), clinical stage, gender, age, LDH, and performance status-assigned response designations by Kaplan-Meier survival analysis. Initial stages of DLBL patients were stage I in 4, II in 14, III in 15, and IV in 4 by Ann Arbor system. Median follow up period was 15.5months, and estimated mean TTF was 22.3 months. Univariate analysis demonstrated that TTF is statistically significantly reduced in those with high VOLsum (>215.1cm2, p=0.004), high SUV Volsum (>1577.5, p=0.003), and increased LDH (p=0.036). TTF did not correlate with SUVmax (p=0.571), clinical stage (p=0.194), gender (p=0.549), and age (p=0.128), and performance status =2 (p=0.074). Multivariate analysis using VOLsum, SUV Volsum, LDH, and performance status demonstrated no statistically significant predictor of TTF (p>0.05). Systemic tumor volume measurement using FDG-PET is suggestive to be the significant prognostic factor in patients with DLBL

Strong Localization in Disordered Media: Analysis of the Backscattering Cone

KAUST Repository

Delgado, Edgar

2012-06-01

A very interesting effect in light propagation through a disordered system is Anderson localization of light, this phenomenon emerges as the result of multiple scattering of waves by electric inhomogeneities like spatial variations of index of refraction; as the amount of scattering is increased, light propagation is converted from quasi-diffusive to exponentially localized, with photons confined in a limited spatial region characterized by a fundamental quantity known as localization length. Light localization is strongly related to another interference phenomenon emerged from the multiple scattering effect: the coherent backscattering effect. In multiple scattering of waves, in fact, coherence is preserved in the backscattering direction and produces a reinforcement of the field flux originating an observable peak in the backscattered intensity, known as backscattering cone. The study of this peak provide quantitative information about the transport properties of light in the material. In this thesis we report a complete FDTD ab-initio study of light localization and coherent backscattering. In particular, we consider a supercontinuum pulse impinging on a sample composed of randomly positioned scatterers. We study coherent backscattering by averaging over several realizations of the sample properties. We study then the coherent backscattering cone properties as the relative permittivity of the sample is changed, relating the latter with the light localization inside the sample. We demonstrate important relationships between the width of the backscattering cone and the localization length, which shows a linear proportionality in the strong localization regime.

Plasma microinstabilities driven by loss-cone distributions

International Nuclear Information System (INIS)

Summers, D.; Thorne, R.M.

1995-01-01

Electromagnetic and electrostatic instabilities driven by loss-cone particle distributions have been invoked to explain a variety of plasma phenomena observed in space and in the laboratory. In this paper we analyse how the loss-cone feature (as determined by the loss-cone index or indices) influences the growth of such instabilities in a fully ionized, homogeneous, hot plasma in a uniform magnetic field. Specifically, we consider three loss-cone distributions: a generalized Lorentzian (kappa) loss-cone distribution, the Dory-Guest-Harris distribution and the Ashour-Abdalla-Kennel distribution (involving a subtracted Maxwellian). Our findings are common to all three distributions. We find that, for parallel propagation, electromagnetic instabilities are only affected by the loss-cone indices in terms of their occurrence in the temperature anisotropy. However, for oblique propagation, even including propagation at small angles to the ambient magnetic field, the loss-cone indices do independently affect the growth of instabilities for electromagnetic waves, in contrast to certain claims in the literature. For electrostatic waves such that 1/2(κ perpendicular to ρ L σ 2 L σ is the Larmor radius for particle species σ, we find that the loss-cone indices only enter the dispersion equation via the temperature anisotropy, and so in this case the loss-cone feature and perpendicular effective thermal speed do not independently affect wave growth. (Author)

Integrity of the cone photoreceptor mosaic in oligocone trichromacy

DEFF Research Database (Denmark)

Michaelides, Michel; Rha, Jungtae; Dees, Elise W

2011-01-01

Oligocone trichromacy (OT) is an unusual cone dysfunction syndrome characterized by reduced visual acuity, mild photophobia, reduced amplitude of the cone electroretinogram with normal rod responses, normal fundus appearance, and normal or near-normal color vision. It has been proposed that these...... that these patients have a reduced number of normal functioning cones (oligocone). This paper has sought to evaluate the integrity of the cone photoreceptor mosaic in four patients previously described as having OT....

Radiation dose in cone-beam computed tomography: myth or reality

International Nuclear Information System (INIS)

Madi, Medhini

2013-01-01

In the growing inventory of clinical computed tomography technologies, cone-beam X-ray computed tomography is a relatively recent instalment. It is an advancement in computed tomography imaging which is designed to provide relatively low-dose high-spatial-resolution visualization of high contrast structures in the head and neck and other anatomic areas. Comparatively low dosing requirements and relatively compact design has led to intense interest in surgical planning and intra-operative cone-beam computed tomography applications, particularly in head and neck, and also in spinal, thoracic, abdominal and orthopaedic procedures. The use of this emerging imaging technology, which has potential applications for imaging of high-contrast structures in the head and neck as well as dentomaxillofacial regions, has been the subject of criticism as well as acclaim. This paper envisages to discuss the state-of-the-art of the technique. (author)

CRYOVOLCANISM AND THE MYSTERY OF THE PATOM CONE

Directory of Open Access Journals (Sweden)

Vladimir R. Alekseyev

2012-01-01

Full Text Available In the Earth’s regions with cold climate, cryovolcanism is widespread. This phenomena is manifested as eruptions of material due to freezing of closed-type or open-type water-bearing systems which is accompanied by generation of effusive topographic forms, such as «pingo». The Patom cone is a typical structure created by cryovolcanism in fractured bedrocksof the Proterozoic age. The cone was shaped a result of the long-term, possibly multistage freezing of the hydrogeological structure during continuous and complicated phase of cryo- and speleo-genesis. The ice-saturated breccia containing limestone, sandstone and shale, which composed the cone, was subject to slow spreading due to its plastic properties; the top of the mound developed into a subsidence cone bordered by ring-shaped ramparts and a knoll in the middle, while thelongitudinal profile took on an asymmetric form. The absence of soil and vegetation cover on the surface of the cone, and a relatively weak degree of weathering of the rudaceous deposits bear no evidence that the geological object is young. The question as to the age of the cone is still open.

Brain regional {alpha}-[{sup 11}C]methyl-L-tryptophan trapping, used as an index of 5-HT synthesis, in healthy adults: absence of an age effect

Energy Technology Data Exchange (ETDEWEB)

Rosa-Neto, Pedro; Benkelfat, Chawki; Leyton, Marco [Department of Neurology and Neurosurgery, Montreal (Canada); McGill University, Department of Psychiatry, Montreal, Quebec (Canada); Sakai, Yojiro [Department of Neurology and Neurosurgery, Montreal (Canada); University of Tokyo, Department of Psychosomatic Medicine, Tokyo (Japan); Morais, Jose A. [McGill University, Department of Geriatrics, Montreal, Quebec (Canada); Diksic, Mirko [Department of Neurology and Neurosurgery, Montreal (Canada)

2007-08-15

Previous functional neuroimaging studies suggest that selective aspects of the brain serotonin (5-HT) system change during the aging process. Here, we assessed the effects of aging on the brain regional {alpha}-[{sup 11}C]methyl-L-tryptophan ({alpha}-[{sup 11}C]MTrp) trapping rate constant (K*; {mu}l.g{sup -1}.min{sup -1}), which, with certain assumptions, could be taken as a proxy of 5-HT synthesis. Thirty-six healthy right-handed subjects had positron emission tomography (PET) scans following injection with {alpha}-[{sup 11}C]MTrp [18 males aged 46.6 {+-} 22.2 years (range 20-80 years) and 18 females aged 33.0 {+-} 15.5 years (range 20-80 years)]. The trapping rate constant, K*, was calculated with the graphical method for irreversible ligands using the sinus-venous input function. A priori selected volumes of interest (VOIs) were defined using an automatic algorithm. VOI analysis showed no correlation between age and brain regional K* values. As reported by others, significant age-related reductions of gray matter were observed in the thalamus and frontal and cingulate cortices; even with partial volume correction there was still no significant relationship between K* and age. Further exploratory SPM voxelwise correlation between age and {alpha}-[{sup 11}C]MTrp trapping, using p = 0.05 (uncorrected), as well as voxel-based morphometry, was in agreement with the VOI analysis. The dissociation between age-related changes in brain anatomy and this index of serotonin synthesis suggests independent mechanisms underlying the normal aging process. (orig.)

Simulation analysis of the effects of an initial cone position and opening angle on a cone-guided implosion

Energy Technology Data Exchange (ETDEWEB)

Yanagawa, T. [Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan); Sakagami, H. [Fundamental Physics Simulation Division, National Institute for Fusion Science, Oroshi-cho, Toki, Gifu 509-5292 (Japan); Nagatomo, H. [Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan)

2013-10-15

In inertial confinement fusion, the implosion process is important in forming a high-density plasma core. In the case of a fast ignition scheme using a cone-guided target, the fuel target is imploded with a cone inserted. This scheme is advantageous for efficiently heating the imploded fuel core; however, asymmetric implosion is essentially inevitable. Moreover, the effect of cone position and opening angle on implosion also becomes critical. Focusing on these problems, the effect of the asymmetric implosion, the initial position, and the opening angle on the compression rate of the fuel is investigated using a three-dimensional pure hydrodynamic code.

Quantification of tumor vessels in glioblastoma patients using time-of-flight angiography at 7 Tesla: a feasibility study.

Directory of Open Access Journals (Sweden)

Alexander Radbruch

Full Text Available PURPOSE: To analyze if tumor vessels can be visualized, segmented and quantified in glioblastoma patients with time of flight (ToF angiography at 7 Tesla and multiscale vessel enhancement filtering. MATERIALS AND METHODS: Twelve patients with newly diagnosed glioblastoma were examined with ToF angiography (TR = 15 ms, TE = 4.8 ms, flip angle = 15°, FOV = 160 × 210 mm(2, voxel size: 0.31 × 0.31 × 0.40 mm(3 on a whole-body 7 T MR system. A volume of interest (VOI was placed within the border of the contrast enhancing part on T1-weighted images of the glioblastoma and a reference VOI was placed in the non-affected contralateral white matter. Automated segmentation and quantification of vessels within the two VOIs was achieved using multiscale vessel enhancement filtering in ImageJ. RESULTS: Tumor vessels were clearly visible in all patients. When comparing tumor and the reference VOI, total vessel surface (45.3 ± 13.9 mm(2 vs. 29.0 ± 21.0 mm(2 (p<0.035 and number of branches (3.5 ± 1.8 vs. 1.0 ± 0.6 (p<0.001 per cubic centimeter were significantly higher, while mean vessel branch length was significantly lower (3.8 ± 1.5 mm vs 7.2 ± 2.8 mm (p<0.001 in the tumor. DISCUSSION: ToF angiography at 7-Tesla MRI enables characterization and quantification of the internal vascular morphology of glioblastoma and may be used for the evaluation of therapy response within future studies.

Determination and evaluation of intra fractional and set-up changes during radiotherapy to the cervical carcinoma using cone beam computed tomography

International Nuclear Information System (INIS)

Pathak, Pankaj; Kumar, Rajesh; Birbiya, Narendra; Mishra, Praveen Kumar; Singh, Manisha; Mishra, Pankaj Kumar

2017-01-01

To confirm the accuracy of the location of the Fudicial markings in relation to the actual isocentre of the irradiated volume due to Intra-fractional and Set-Up changes in Cancer Cervix with the help of Cone Beam computed Tomography (CBCT)

SU-F-J-23: Field-Of-View Expansion in Cone-Beam CT Reconstruction by Use of Prior Information

Energy Technology Data Exchange (ETDEWEB)

Haga, A; Magome, T; Nakano, M; Nakagawa, K [University of Tokyo Hospital, Tokyo (Japan); Kotoku, J [Teikyo University, Tokyo (Japan)

2016-06-15

Purpose: Cone-beam CT (CBCT) has become an integral part of online patient setup in an image-guided radiation therapy (IGRT). In addition, the utility of CBCT for dose calculation has actively been investigated. However, the limited size of field-of-view (FOV) and resulted CBCT image with a lack of peripheral area of patient body prevents the reliability of dose calculation. In this study, we aim to develop an FOV expanded CBCT in IGRT system to allow the dose calculation. Methods: Three lung cancer patients were selected in this study. We collected the cone-beam projection images in the CBCT-based IGRT system (X-ray volume imaging unit, ELEKTA), where FOV size of the provided CBCT with these projections was 410 × 410 mm{sup 2} (normal FOV). Using these projections, CBCT with a size of 728 × 728 mm{sup 2} was reconstructed by a posteriori estimation algorithm including a prior image constrained compressed sensing (PICCS). The treatment planning CT was used as a prior image. To assess the effectiveness of FOV expansion, a dose calculation was performed on the expanded CBCT image with region-of-interest (ROI) density mapping method, and it was compared with that of treatment planning CT as well as that of CBCT reconstructed by filtered back projection (FBP) algorithm. Results: A posteriori estimation algorithm with PICCS clearly visualized an area outside normal FOV, whereas the FBP algorithm yielded severe streak artifacts outside normal FOV due to under-sampling. The dose calculation result using the expanded CBCT agreed with that using treatment planning CT very well; a maximum dose difference was 1.3% for gross tumor volumes. Conclusion: With a posteriori estimation algorithm, FOV in CBCT can be expanded. Dose comparison results suggested that the use of expanded CBCTs is acceptable for dose calculation in adaptive radiation therapy. This study has been supported by KAKENHI (15K08691).

Conceptual Design of Deployment Structure of Morphing Nose Cone

Directory of Open Access Journals (Sweden)

Junlan Li

2013-01-01

Full Text Available For a reusable space vehicle or a missile, the shape of the nose cone has a significant effect on the drag of the vehicle. In this paper, the concept of morphing nose cone is proposed to reduce the drag when the reentry vehicle flies back into the atmosphere. The conceptual design of the structure of morphing nose cone is conducted. Mechanical design and optimization approach are developed by employing genetic algorithm to find the optimal geometric parameters of the morphing structure. An example is analyzed by using the proposed method. The results show that optimal solution supplies the minimum position error. The concept of morphing nose cone will provide a novel way for the drag reduction of reentry vehicle. The proposed method could be practically used for the design and optimization of the deployable structure of morphing nose cone.

3D tumor measurement in cone-beam CT breast imaging

Science.gov (United States)

Chen, Zikuan; Ning, Ruola

2004-05-01

Cone-beam CT breast imaging provides a digital volume representation of a breast. With a digital breast volume, the immediate task is to extract the breast tissue information, especially for suspicious tumors, preferably in an automatic manner or with minimal user interaction. This paper reports a program for three-dimensional breast tissue analysis. It consists of volumetric segmentation (by globally thresholding), subsegmentation (connection-based separation), and volumetric component measurement (volume, surface, shape, and other geometrical specifications). A combination scheme of multi-thresholding and binary volume morphology is proposed to fast determine the surface gradients, which may be interpreted as the surface evolution (outward growth or inward shrinkage) for a tumor volume. This scheme is also used to optimize the volumetric segmentation. With a binary volume, we decompose the foreground into components according to spatial connectedness. Since this decomposition procedure is performed after volumetric segmentation, it is called subsegmentation. The subsegmentation brings the convenience for component visualization and measurement, in the whole support space, without interference from others. Upon the tumor component identification, we measure the following specifications: volume, surface area, roundness, elongation, aspect, star-shapedness, and location (centroid). A 3D morphological operation is used to extract the cluster shell and, by delineating the corresponding volume from the grayscale volume, to measure the shell stiffness. This 3D tissue measurement is demonstrated with a tumor-borne breast specimen (a surgical part).

MRS of normal and impaired fetal brain development

International Nuclear Information System (INIS)

Girard, Nadine; Fogliarini, Celine; Viola, Angele; Confort-Gouny, Sylviane; Le Fur, Yann; Viout, Patrick; Chapon, Frederique; Levrier, Olivier; Cozzone, Patrick

2006-01-01

Cerebral maturation in the human fetal brain was investigated by in utero localized proton magnetic resonance spectroscopy (MRS). Spectra were acquired on a clinical MR system operating at 1.5 T. Body phased array coils (four coils) were used in combination with spinal coils (two coils). The size of the nominal volume of interest (VOI) was 4.5 cm 3 (20 mm x 15 mm x 15 mm). The MRS acquisitions were performed using a spin echo sequence at short and long echo times (TE = 30 ms and 135 ms) with a VOI located within the cerebral hemisphere at the level of the centrum semiovale. A significant reduction in myo-inositol and choline and an increase in N-acetylaspartate were observed with progressive age. The normal MR spectroscopy data reported here will help to determine whether brain metabolism is altered, especially when subtle anatomic changes are observed on conventional images. Some examples of impaired fetal brain development studied by MRS are illustrated

MRS of normal and impaired fetal brain development

Energy Technology Data Exchange (ETDEWEB)

Girard, Nadine [Service de Neuroradiologie, Assistance Publique-Hopitaux de Marseille, Hopital la Timone, Universite de la Mediterranee, Marseille (France)]. E-mail: nadine.girard@ap-hm.fr; Fogliarini, Celine [Centre de Resonance Magnetique Biologique et Medicale, UMR CNRS 6612, Universite de la Mediterranee, Faculte de Medecine la Timone, Marseille (France); Viola, Angele [Centre de Resonance Magnetique Biologique et Medicale, UMR CNRS 6612, Universite de la Mediterranee, Faculte de Medecine la Timone, Marseille (France); Confort-Gouny, Sylviane [Centre de Resonance Magnetique Biologique et Medicale, UMR CNRS 6612, Universite de la Mediterranee, Faculte de Medecine la Timone, Marseille (France); Le Fur, Yann [Centre de Resonance Magnetique Biologique et Medicale, UMR CNRS 6612, Universite de la Mediterranee, Faculte de Medecine la Timone, Marseille (France); Viout, Patrick [Centre de Resonance Magnetique Biologique et Medicale, UMR CNRS 6612, Universite de la Mediterranee, Faculte de Medecine la Timone, Marseille (France); Chapon, Frederique [Service de Neuroradiologie, Assistance Publique-Hopitaux de Marseille, Hopital la Timone, Universite de la Mediterranee, Marseille (France); Levrier, Olivier [Service de Neuroradiologie, Assistance Publique-Hopitaux de Marseille, Hopital la Timone, Universite de la Mediterranee, Marseille (France); Cozzone, Patrick [Centre de Resonance Magnetique Biologique et Medicale, UMR CNRS 6612, Universite de la Mediterranee, Faculte de Medecine la Timone, Marseille (France)

2006-02-15

Cerebral maturation in the human fetal brain was investigated by in utero localized proton magnetic resonance spectroscopy (MRS). Spectra were acquired on a clinical MR system operating at 1.5 T. Body phased array coils (four coils) were used in combination with spinal coils (two coils). The size of the nominal volume of interest (VOI) was 4.5 cm{sup 3} (20 mm x 15 mm x 15 mm). The MRS acquisitions were performed using a spin echo sequence at short and long echo times (TE = 30 ms and 135 ms) with a VOI located within the cerebral hemisphere at the level of the centrum semiovale. A significant reduction in myo-inositol and choline and an increase in N-acetylaspartate were observed with progressive age. The normal MR spectroscopy data reported here will help to determine whether brain metabolism is altered, especially when subtle anatomic changes are observed on conventional images. Some examples of impaired fetal brain development studied by MRS are illustrated.

Increasing Cone-beam projection usage by temporal fitting

DEFF Research Database (Denmark)

Lyksborg, Mark; Hansen, Mads Fogtmann; Larsen, Rasmus

2010-01-01

A Cone-beam CT system can be used to image the lung region. The system records 2D projections which will allow 3D reconstruction however a reconstruction based on all projections will lead to a blurred reconstruction in regions were respiratory motion occur. To avoid this the projections are typi......A Cone-beam CT system can be used to image the lung region. The system records 2D projections which will allow 3D reconstruction however a reconstruction based on all projections will lead to a blurred reconstruction in regions were respiratory motion occur. To avoid this the projections...... in [6] prior knowledge of the lung deformation estimated from the planning CT could be used to include all projections into the reconstruction. It has also been attempted to estimate both the motion and 3D volume simultaneously in [4]. Problems with motion estimation are ill-posed leading to suboptimal...... motion which in return affects the reconstruction. By directly including time into the image representation the effect of suboptimal motion fields are avoided and we are still capable of using phase neighbour projections. The 4D image model is fitted by solving a statistical cost function based...

Double Dirac cones in phononic crystals

KAUST Repository

Li, Yan

2014-07-07

A double Dirac cone is realized at the center of the Brillouin zone of a two-dimensional phononic crystal (PC) consisting of a triangular array of core-shell-structure cylinders in water. The double Dirac cone is induced by the accidental degeneracy of two double-degenerate Bloch states. Using a perturbation method, we demonstrate that the double Dirac cone is composed of two identical and overlapping Dirac cones whose linear slopes can also be accurately predicted from the method. Because the double Dirac cone occurs at a relatively low frequency, a slab of the PC can be mapped onto a slab of zero refractive index material by using a standard retrieval method. Total transmission without phase change and energy tunneling at the double Dirac point frequency are unambiguously demonstrated by two examples. Potential applications can be expected in diverse fields such as acoustic wave manipulations and energy flow control.

Double Dirac cones in phononic crystals

KAUST Repository

Li, Yan; Wu, Ying; Mei, Jun

2014-01-01

A double Dirac cone is realized at the center of the Brillouin zone of a two-dimensional phononic crystal (PC) consisting of a triangular array of core-shell-structure cylinders in water. The double Dirac cone is induced by the accidental degeneracy of two double-degenerate Bloch states. Using a perturbation method, we demonstrate that the double Dirac cone is composed of two identical and overlapping Dirac cones whose linear slopes can also be accurately predicted from the method. Because the double Dirac cone occurs at a relatively low frequency, a slab of the PC can be mapped onto a slab of zero refractive index material by using a standard retrieval method. Total transmission without phase change and energy tunneling at the double Dirac point frequency are unambiguously demonstrated by two examples. Potential applications can be expected in diverse fields such as acoustic wave manipulations and energy flow control.

Cone calorimeter tests of wood composites

Science.gov (United States)

Robert H. White; Kuma Sumathipala

2013-01-01

The cone calorimeter is widely used for the determination of the heat release rate (HRR) of building products and other materials. As part of an effort to increase the availability of cone calorimeter data on wood products, the U.S. Forest Products Laboratory and the American Wood Council conducted this study on composite wood products in cooperation with the Composite...

Reconstruction for interior region-of-interest inverse geometry computed tomography: preliminary study

Energy Technology Data Exchange (ETDEWEB)

Kim, Dong Su; Kim, Tae Ho; Kim, Kyeong Hyeon; Yoon, Do Kun; Suh, Tae Suk [Dept. of Biomedical Engineering, Research Institute of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seoul (Korea, Republic of); Kang, Seong Hee [Dept. of Radiation Oncology, Seoul National University Hospital, Seoul (Korea, Republic of); Cho, Min Seok [Dept. of Radiation Oncology, Asan Medical Center, Seoul (Korea, Republic of); Noh, Yu Yoon [Dept. of Radiation Oncology, Eulji University Hospital, Daejeon (Korea, Republic of)

2017-04-15

The inverse geometry computed tomography (IGCT) composed of multiple source and small size detector has several merits such as reduction of scatter effect and large volumetric imaging within one rotation without cone-beam artifact, compared to conventional cone-beam computed tomography (CBCT). By using this multi-source characteristics, we intend to present a selective and multiple interior region-of-interest (ROI) imaging method by using a designed source on-off sequence of IGCT. ROI-IGCT showed comparable image quality and has the capability to provide multi ROI image within a rotation. In this regard, it seems to be useful for diagnostic or image guidance for radiotherapy. ROI-IGCT showed comparable image quality and has the capability to provide multi ROI image within a rotation. Projection of ROI-IGCT is performed by selective irradiation, hence unnecessary imaging dose to non-interest region can be reduced. In this regard, it seems to be useful for diagnostic or image guidance for radiotherapy.

Integrity of the cone photoreceptor mosaic in oligocone trichromacy

DEFF Research Database (Denmark)

Michaelides, Michel; Rha, Jungtae; Dees, Elise W

2011-01-01

Oligocone trichromacy (OT) is an unusual cone dysfunction syndrome characterized by reduced visual acuity, mild photophobia, reduced amplitude of the cone electroretinogram with normal rod responses, normal fundus appearance, and normal or near-normal color vision. It has been proposed that these......Oligocone trichromacy (OT) is an unusual cone dysfunction syndrome characterized by reduced visual acuity, mild photophobia, reduced amplitude of the cone electroretinogram with normal rod responses, normal fundus appearance, and normal or near-normal color vision. It has been proposed...

Preparation of Au cone for fast ignition target

International Nuclear Information System (INIS)

Du Kai; Zhou Lan; Zhang Lin; Wan Xiaobo; Xiao Jiang

2005-01-01

Cone-shell target is typically used for the fast ignition experiments of inertial confinement fusion. In order to fabricate cone-shell target the Au cones with different angles were produced by electroplating and precise machining. The Au electroplating process was introduced in the paper, and the dependence of coating quality on the parameters, such as composition, temperature, pH of electroplating bath, current density and tip effect, were discussed. (author)

The volume of fluid method in spherical coordinates

NARCIS (Netherlands)

Janse, A.M.C.; Janse, A.M.C.; Dijk, P.E.; Kuipers, J.A.M.

2000-01-01

The volume of fluid (VOF) method is a numerical technique to track the developing free surfaces of liquids in motion. This method can, for example, be applied to compute the liquid flow patterns in a rotating cone reactor. For this application a spherical coordinate system is most suited. The novel

Handling data redundancy in helical cone beam reconstruction with a cone-angle-based window function and its asymptotic approximation

International Nuclear Information System (INIS)

Tang Xiangyang; Hsieh Jiang

2007-01-01

A cone-angle-based window function is defined in this manuscript for image reconstruction using helical cone beam filtered backprojection (CB-FBP) algorithms. Rather than defining the window boundaries in a two-dimensional detector acquiring projection data for computed tomographic imaging, the cone-angle-based window function deals with data redundancy by selecting rays with the smallest cone angle relative to the reconstruction plane. To be computationally efficient, an asymptotic approximation of the cone-angle-based window function is also given and analyzed in this paper. The benefit of using such an asymptotic approximation also includes the avoidance of functional discontinuities that cause artifacts in reconstructed tomographic images. The cone-angle-based window function and its asymptotic approximation provide a way, equivalent to the Tam-Danielsson-window, for helical CB-FBP reconstruction algorithms to deal with data redundancy, regardless of where the helical pitch is constant or dynamically variable during a scan. By taking the cone-parallel geometry as an example, a computer simulation study is conducted to evaluate the proposed window function and its asymptotic approximation for helical CB-FBP reconstruction algorithm to handle data redundancy. The computer simulated Forbild head and thorax phantoms are utilized in the performance evaluation, showing that the proposed cone-angle-based window function and its asymptotic approximation can deal with data redundancy very well in cone beam image reconstruction from projection data acquired along helical source trajectories. Moreover, a numerical study carried out in this paper reveals that the proposed cone-angle-based window function is actually equivalent to the Tam-Danielsson-window, and rigorous mathematical proofs are being investigated

Analysis of end-systolic pressure-volume relation by gated radionuclide angiocardiography

International Nuclear Information System (INIS)

Adachi, Haruhiko; Sugihara, Horoki; Katsume, Hiroshi; Ijichi, Hamao; Miyanaga, Hajime

1982-01-01

Left ventricular end-systolic pressure-volume relation has been proved experimentally to b e an useful index of left ventricular contractility relatively independent of preload or afterload. But less clinical application has been reported because of its invasive nature, and we evaluated this relationship non-invasively using gated radionuclide angiocardiography as volume determination and cuff sphyngomanometer in the arm as pressure measurement. Gated equilibrium blood pool scintigrams were obtained at rest and during intravenous infusion of angiotensin or nitrate. Ventricular volumes were derived from ventricular activity and peripheral blood volume and activity. The peak systolic pressure (PSP) by cuff method to end-systolic volume index (ESVI) relations showed good linearity (r gt .930 in 84% of consecutive 50 cases) and were gentler in the groups with more impaired left ventricular function. Emax was related exponentially to ejection fraction (EF) and hyperbolically to end-diastolic volume index. The dead volume (VoI) was unfixed and fell into positive or negative value, and was not related to EF under control condition. PSP/ESVI in each loading condition was less variable with the alteration of blood pressure than EF. The linear relation was found between PSP/ESVI under control condition and Emax (PSP/ESVI = 0.651.Emax + 0.958, r = 0.841, p lt .001). Thus in measuring ventricular volume, gated radionuclide angiocardiography is a non-invasive method less affected by the geometry of the left ventricle. Non-invasive determination of end-systolic pressure-volume relation using the volume by radionuclide and the blood pressure by cuff method is clinically useful in the assessment of left ventricular contractility. (author)

Reduction in cardiac volume during chemoradiotherapy for patients with esophageal cancer

Energy Technology Data Exchange (ETDEWEB)

Lutkenhaus, Lotte J., E-mail: l.j.lutkenhaus@amc.uva.nl; Kamphuis, Martijn; Wieringen, Niek van; Hulshof, Maarten C.C.M.; Bel, Arjan

2013-11-15

We investigated the change in cardiac volume over the course of chemoradiotherapy in 26 patients treated for esophageal cancer, using cone beam CT imaging. The cardiac volume reduced significantly, with a median reduction of 8%. A significant relationship with planned cardiac dose was not found.

Reduction in cardiac volume during chemoradiotherapy for patients with esophageal cancer

International Nuclear Information System (INIS)

Lutkenhaus, Lotte J.; Kamphuis, Martijn; Wieringen, Niek van; Hulshof, Maarten C.C.M.; Bel, Arjan

2013-01-01

We investigated the change in cardiac volume over the course of chemoradiotherapy in 26 patients treated for esophageal cancer, using cone beam CT imaging. The cardiac volume reduced significantly, with a median reduction of 8%. A significant relationship with planned cardiac dose was not found

Interactive lung segmentation in abnormal human and animal chest CT scans

International Nuclear Information System (INIS)

Kockelkorn, Thessa T. J. P.; Viergever, Max A.; Schaefer-Prokop, Cornelia M.; Bozovic, Gracijela; Muñoz-Barrutia, Arrate; Rikxoort, Eva M. van; Brown, Matthew S.; Jong, Pim A. de; Ginneken, Bram van

2014-01-01

Purpose: Many medical image analysis systems require segmentation of the structures of interest as a first step. For scans with gross pathology, automatic segmentation methods may fail. The authors’ aim is to develop a versatile, fast, and reliable interactive system to segment anatomical structures. In this study, this system was used for segmenting lungs in challenging thoracic computed tomography (CT) scans. Methods: In volumetric thoracic CT scans, the chest is segmented and divided into 3D volumes of interest (VOIs), containing voxels with similar densities. These VOIs are automatically labeled as either lung tissue or nonlung tissue. The automatic labeling results can be corrected using an interactive or a supervised interactive approach. When using the supervised interactive system, the user is shown the classification results per slice, whereupon he/she can adjust incorrect labels. The system is retrained continuously, taking the corrections and approvals of the user into account. In this way, the system learns to make a better distinction between lung tissue and nonlung tissue. When using the interactive framework without supervised learning, the user corrects all incorrectly labeled VOIs manually. Both interactive segmentation tools were tested on 32 volumetric CT scans of pigs, mice and humans, containing pulmonary abnormalities. Results: On average, supervised interactive lung segmentation took under 9 min of user interaction. Algorithm computing time was 2 min on average, but can easily be reduced. On average, 2.0% of all VOIs in a scan had to be relabeled. Lung segmentation using the interactive segmentation method took on average 13 min and involved relabeling 3.0% of all VOIs on average. The resulting segmentations correspond well to manual delineations of eight axial slices per scan, with an average Dice similarity coefficient of 0.933. Conclusions: The authors have developed two fast and reliable methods for interactive lung segmentation in

Clinical evaluation of respiration-induced attenuation uncertainties in pulmonary 3D PET/CT.

Science.gov (United States)

Kruis, Matthijs F; van de Kamer, Jeroen B; Vogel, Wouter V; Belderbos, José Sa; Sonke, Jan-Jakob; van Herk, Marcel

2015-12-01

In contemporary positron emission tomography (PET)/computed tomography (CT) scanners, PET attenuation correction is performed by means of a CT-based attenuation map. Respiratory motion can however induce offsets between the PET and CT data. Studies have demonstrated that these offsets can cause errors in quantitative PET measures. The purpose of this study is to quantify the effects of respiration-induced CT differences on the attenuation correction of pulmonary 18-fluordeoxyglucose (FDG) 3D PET/CT in a patient population and to investigate contributing factors. For 32 lung cancer patients, 3D-CT, 4D-PET and 4D-CT data were acquired. The 4D FDG PET data were attenuation corrected (AC) using a free-breathing 3D-CT (3D-AC), the end-inspiration CT (EI-AC), the end-expiration CT (EE-AC) or phase-by-phase (P-AC). After reconstruction and AC, the 4D-PET data were averaged. In the 4Davg data, we measured maximum tumour standardised uptake value (SUV)max in the tumour, SUVmean in a lung volume of interest (VOI) and average SUV (SUVmean) in a muscle VOI. On the 4D-CT, we measured the lung volume differences and CT number changes between inhale and exhale in the lung VOI. Compared to P-AC, we found -2.3% (range -9.7% to 1.2%) lower tumour SUVmax in EI-AC and 2.0% (range -0.9% to 9.5%) higher SUVmax in EE-AC. No differences in the muscle SUV were found. The use of 3D-AC led to respiration-induced SUVmax differences up to 20% compared to the use of P-AC. SUVmean differences in the lung VOI between EI-AC and EE-AC correlated to average CT differences in this region (ρ = 0.83). SUVmax differences in the tumour correlated to the volume changes of the lungs (ρ = -0.55) and the motion amplitude of the tumour (ρ = 0.53), both as measured on the 4D-CT. Respiration-induced CT variations in clinical data can in extreme cases lead to SUV effects larger than 10% on PET attenuation correction. These differences were case specific and correlated to differences in CT number

Dirac cones in isogonal hexagonal metallic structures

Science.gov (United States)

Wang, Kang

2018-03-01

A honeycomb hexagonal metallic lattice is equivalent to a triangular atomic one and cannot create Dirac cones in its electromagnetic wave spectrum. We study in this work the low-frequency electromagnetic band structures in isogonal hexagonal metallic lattices that are directly related to the honeycomb one and show that such structures can create Dirac cones. The band formation can be described by a tight-binding model that allows investigating, in terms of correlations between local resonance modes, the condition for the Dirac cones and the consequence of the third structure tile sustaining an extra resonance mode in the unit cell that induces band shifts and thus nonlinear deformation of the Dirac cones following the wave vectors departing from the Dirac points. We show further that, under structure deformation, the deformations of the Dirac cones result from two different correlation mechanisms, both reinforced by the lattice's metallic nature, which directly affects the resonance mode correlations. The isogonal structures provide new degrees of freedom for tuning the Dirac cones, allowing adjustment of the cone shape by modulating the structure tiles at the local scale without modifying the lattice periodicity and symmetry.

A probabilistic approach to delineating functional brain regions

DEFF Research Database (Denmark)

Kalbitzer, Jan; Svarer, Claus; Frokjaer, Vibe G

2009-01-01

The purpose of this study was to develop a reliable observer-independent approach to delineating volumes of interest (VOIs) for functional brain regions that are not identifiable on structural MR images. The case is made for the raphe nuclei, a collection of nuclei situated in the brain stem known...... to be densely packed with serotonin transporters (5-hydroxytryptaminic [5-HTT] system). METHODS: A template set for the raphe nuclei, based on their high content of 5-HTT as visualized in parametric (11)C-labeled 3-amino-4-(2-dimethylaminomethyl-phenylsulfanyl)-benzonitrile PET images, was created for 10...... healthy subjects. The templates were subsequently included in the region sets used in a previously published automatic MRI-based approach to create an observer- and activity-independent probabilistic VOI map. The probabilistic map approach was tested in a different group of 10 subjects and compared...

Loss and gain of cone types in vertebrate ciliary photoreceptor evolution.

Science.gov (United States)

Musser, Jacob M; Arendt, Detlev

2017-11-01

Ciliary photoreceptors are a diverse cell type family that comprises the rods and cones of the retina and other related cell types such as pineal photoreceptors. Ciliary photoreceptor evolution has been dynamic during vertebrate evolution with numerous gains and losses of opsin and phototransduction genes, and changes in their expression. For example, early mammals lost all but two cone opsins, indicating loss of cone receptor types in response to nocturnal lifestyle. Our review focuses on the comparison of specifying transcription factors and cell type-specific transcriptome data in vertebrate retinae to build and test hypotheses on ciliary photoreceptor evolution. Regarding cones, recent data reveal that a combination of factors specific for long-wavelength sensitive opsin (Lws)- cones in non-mammalian vertebrates (Thrb and Rxrg) is found across all differentiating cone photoreceptors in mice. This suggests that mammalian ancestors lost all but one ancestral cone type, the Lws-cone. We test this hypothesis by a correlation analysis of cone transcriptomes in mouse and chick, and find that, indeed, transcriptomes of all mouse cones are most highly correlated to avian Lws-cones. These findings underscore the importance of specifying transcription factors in tracking cell type evolution, and shed new light on the mechanisms of cell type loss and gain in retina evolution. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Cone-Beam Computed Tomography Analysis of the Nasopharyngeal Airway in Nonsyndromic Cleft Lip and Palate Subjects.

Science.gov (United States)

Al-Fahdawi, Mahmood Abd; Farid, Mary Medhat; El-Fotouh, Mona Abou; El-Kassaby, Marwa Abdelwahab

2017-03-01

  To assess the nasopharyngeal airway volume, cross-sectional area, and depth in previously repaired nonsyndromic unilateral cleft lip and palate versus bilateral cleft lip and palate patients compared with noncleft controls using cone-beam computed tomography with the ultimate goal of finding whether cleft lip and palate patients are more liable to nasopharyngeal airway obstruction.   A retrospective analysis comparing bilateral cleft lip and palate, unilateral cleft lip and palate, and control subjects. Significance at P ≤ .05.   Cleft Care Center and the outpatient clinic that are both affiliated with our faculty.   Cone-beam computed tomography data were selected of 58 individuals aged 9 to 12 years: 14 with bilateral cleft lip and palate and 20 with unilateral cleft lip and palate as well as 24 age- and gender-matched noncleft controls.   Volume, depth, and cross-sectional area of nasopharyngeal airway were measured.   Patients with bilateral cleft lip and palate showed significantly larger nasopharyngeal airway volume than controls and patients with unilateral cleft lip and palate (P cleft lip and palate showed significantly larger cross-sectional area than those with unilateral cleft lip and palate (P .05). Patients with bilateral cleft lip and palate showed significantly larger depth than controls and those with unilateral cleft lip and palate (P cleft lip and palate showed insignificant nasopharyngeal airway volume, cross-sectional area, and depth compared with controls (P > .05).   Unilateral and bilateral cleft lip and palate patients did not show significantly less volume, cross-sectional area, or depth of nasopharyngeal airway than controls. From the results of this study we conclude that unilateral and bilateral cleft lip and palate patients at the studied age and stage of repaired clefts are not more prone to nasopharyngeal airway obstruction than controls.

Non-invasive quantitation of phosphorus metabolites in human brain and brain tumors by magnetic resonance spectroscopy

International Nuclear Information System (INIS)

Naruse, Shoji; Higuchi, Toshihiro; Horikawa, Yoshiharu; Tanaka, Chuzo; Roth, K.; Hubesch, B.; Meyerhoff, D.J.; Weiner, M.W.

1989-01-01

In obtaining localized magnetic resonance spectra in the clinical setting, the exact determination of volume of interest (VOI), the relative sensitivity of detection within the VOI, the inhomogeneity of B 1 field, the Q factor of the coil, and saturation factors should be considered. Taking these items into account, a quantitative method for calculating the absolute amount of phosphorus metabolites was developed. Using this method, phosphorus metabolites in the brain were determined in 15 patients with brain tumors - meningioma (8) and astrocytoma (7), and 10 normal volunteers. The integrals for metabolite signals were determined by using the curve-fitting software. The concentrations for ATP, PCr, PDE, inorganic orthophosphate (Pi), and phosphomonosters (PME) were 2.5, 4.9, 11.3, 1.9 and 3.9 mM, respectively, in the normal brain. For the brain tumors, phosphorus metabolites were decreased, except for Pi and PME. These results encourage the clinical use of this method in the quantitative analysis of metabolites of the diseased brain. (Namekawa, K)

g-Weak Contraction in Ordered Cone Rectangular Metric Spaces

Directory of Open Access Journals (Sweden)

S. K. Malhotra

2013-01-01

Full Text Available We prove some common fixed-point theorems for the ordered g-weak contractions in cone rectangular metric spaces without assuming the normality of cone. Our results generalize some recent results from cone metric and cone rectangular metric spaces into ordered cone rectangular metric spaces. Examples are provided which illustrate the results.

Derivation of the gauge link in light cone gauge

International Nuclear Information System (INIS)

Gao Jianhua

2010-01-01

In light cone gauge, a gauge link at light cone infinity is necessary for transverse momentum-dependent parton distribution to restore the gauge invariance in some specific boundary conditions. We derive such transverse gauge link in a more regular and general method. We find the gauge link at light cone infinity naturally arises from the contribution of the pinched poles: one is from the quark propagator and the other is hidden in the gauge vector field in light cone gauge. Actually, in the amplitude level, we have obtained a more general gauge link over the hypersurface at light cone infinity which is beyond the transverse direction. The difference of such gauge link between semi-inclusive deep inelastic scattering and Drell-Yan processes can also be obtained directly and clearly in our derivation.

Design of a cone target for fast ignition

Directory of Open Access Journals (Sweden)

Sunahara Atsushi

2013-11-01

Full Text Available We propose a new type of target for the fast ignition of inertial confinement fusion. Pre-formed plasma inside a cone target can significantly reduce the energy coupling efficiency from the ultra-high intense short-pulse laser to the imploded core plasma. Also, in order to protect the tip of the cone and reduce generation of pre-formed plasma, we propose pointed shaped cone target. In our estimation, the shock traveling time can be delayed 20–30 ps by lower-Z material with larger areal density compared to the conventional gold flat tip. Also, the jet flow can sweep the blow-off plasma from the tip of the cone, and the implosion performance is not drastically affected by the existence of pointed tip. In addition, the self-generated magnetic field is generated along the boundary of cone tip and surrounding CD or DT plasma. This magnetic field can confine fast electrons and focus to the implosion core plasma. Resultant heating efficiency is improved by 30% compared to that with conventional gold flat tip.

Noise masking of S-cone increments and decrements.

Science.gov (United States)

Wang, Quanhong; Richters, David P; Eskew, Rhea T

2014-11-12

S-cone increment and decrement detection thresholds were measured in the presence of bipolar, dynamic noise masks. Noise chromaticities were the L-, M-, and S-cone directions, as well as L-M, L+M, and achromatic (L+M+S) directions. Noise contrast power was varied to measure threshold Energy versus Noise (EvN) functions. S+ and S- thresholds were similarly, and weakly, raised by achromatic noise. However, S+ thresholds were much more elevated by S, L+M, L-M, L- and M-cone noises than were S- thresholds, even though the noises consisted of two symmetric chromatic polarities of equal contrast power. A linear cone combination model accounts for the overall pattern of masking of a single test polarity well. L and M cones have opposite signs in their effects upon raising S+ and S- thresholds. The results strongly indicate that the psychophysical mechanisms responsible for S+ and S- detection, presumably based on S-ON and S-OFF pathways, are distinct, unipolar mechanisms, and that they have different spatiotemporal sampling characteristics, or contrast gains, or both. © 2014 ARVO.

Full utilization of semi-Dirac cones in photonics

Science.gov (United States)

Yasa, Utku G.; Turduev, Mirbek; Giden, Ibrahim H.; Kurt, Hamza

2018-05-01

In this study, realization and applications of anisotropic zero-refractive-index materials are proposed by exposing the unit cells of photonic crystals that exhibit Dirac-like cone dispersion to rotational symmetry reduction. Accidental degeneracy of two Bloch modes in the Brillouin zone center of two-dimensional C2-symmetric photonic crystals gives rise to the semi-Dirac cone dispersion. The proposed C2-symmetric photonic crystals behave as epsilon-and-mu-near-zero materials (ɛeff≈ 0 , μeff≈ 0 ) along one propagation direction, but behave as epsilon-near-zero material (ɛeff≈ 0 , μeff≠ 0 ) for the perpendicular direction at semi-Dirac frequency. By extracting the effective medium parameters of the proposed C4- and C2-symmetric periodic media that exhibit Dirac-like and semi-Dirac cone dispersions, intrinsic differences between isotropic and anisotropic materials are investigated. Furthermore, advantages of utilizing semi-Dirac cone materials instead of Dirac-like cone materials in photonic applications are demonstrated in both frequency and time domains. By using anisotropic transmission behavior of the semi-Dirac materials, photonic application concepts such as beam deflectors, beam splitters, and light focusing are proposed. Furthermore, to the best of our knowledge, semi-Dirac cone dispersion is also experimentally demonstrated for the first time by including negative, zero, and positive refraction states of the given material.

Light cone thermodynamics

Science.gov (United States)

De Lorenzo, Tommaso; Perez, Alejandro

2018-02-01

We show that null surfaces defined by the outgoing and infalling wave fronts emanating from and arriving at a sphere in Minkowski spacetime have thermodynamical properties that are in strict formal correspondence with those of black hole horizons in curved spacetimes. Such null surfaces, made of pieces of light cones, are bifurcate conformal Killing horizons for suitable conformally stationary observers. They can be extremal and nonextremal depending on the radius of the shining sphere. Such conformal Killing horizons have a constant light cone (conformal) temperature, given by the standard expression in terms of the generalization of surface gravity for conformal Killing horizons. Exchanges of conformally invariant energy across the horizon are described by a first law where entropy changes are given by 1 /(4 ℓp2) of the changes of a geometric quantity with the meaning of horizon area in a suitable conformal frame. These conformal horizons satisfy the zeroth to the third laws of thermodynamics in an appropriate way. In the extremal case they become light cones associated with a single event; these have vanishing temperature as well as vanishing entropy.

The presence of immigrants from Southern-Cone countries to Brazil

OpenAIRE

Sala, Gabriela Adriana; Carvalho, José Alberto Magno de

2008-01-01

Neste artigo são estimados os saldos migratórios dos nascidos na Argentina, Bolívia, Chile, Paraguai e Uruguai, correspondentes às décadas de 80 e 90 para o total do Brasil e para os estados brasileiros que concentravam maior proporção de pessoas provenientes dos países mencionados. Também são analisados alguns fatores que poderiam ter incidido nas mudanças do volume e da composição da população imigrante do Cone Sul, entre 1980 e 2000.En este artículo son estimados los saldos migratorios de ...

Cone-Beam Computed Tomography for Image-Guided Radiation Therapy of Prostate Cancer

Science.gov (United States)

2008-01-01

imaging in small- animal on-Medical Physics, Vol. 34, No. 12, December 2007cology models,” Mol. Imag. 3, 55–62 2004. 8E. B. Walters, K. Panda , J. A...publication 8 October 2007; published 28 November 2007 Cone-beam microcomputed tomography microCT is one of the most popular choices for small animal ...imaging which is becoming an important tool for studying animal models with transplanted diseases. Region-of-interest ROI imaging techniques in CT, which

Porous metal cones: gold standard for massive bone loss in complex revision knee arthroplasty? A systematic review of current literature.

Science.gov (United States)

Divano, Stefano; Cavagnaro, Luca; Zanirato, Andrea; Basso, Marco; Felli, Lamberto; Formica, Matteo

2018-04-18

Revision knee arthroplasty is increasing, and in that case, bone loss management is still a challenging problem. In the last years, the body of literature and interest surrounding porous metal cones has grown, but few systematic evaluations of the existing evidence have been performed. The aim of our systematic review is to collect and critically analyze the available evidence about metal cones in revision knee arthroplasty especially focusing our attention on indications, results, complications, and infection rate of these promising orthopaedic devices. We performed a systematic review of the available English literature, considering the outcomes and the complications of tantalum cones. The combinations of keyword were "porous metal cones", "knee revision", "bone loss", "knee arthroplasty", "periprosthetic joint infection", and "outcome". From the starting 312 papers available, 20 manuscripts were finally included. Only one included study has a control group. The main indication for metal cones is type IIb and III defects according AORI classification. Most of the papers show good clinical and radiological outcomes with low rate of complications. The examined studies provide encouraging clinical and radiological short-to-mid-term outcomes. Clinical studies have shown a low rate of aseptic loosening, intraoperative fractures, infection rate and a lower failure rate than the previous treatment methods. Higher quality papers are needed to draw definitive conclusions about porous metal cones.

Spatiotemporal regulation of ATP and Ca2+ dynamics in vertebrate rod and cone ribbon synapses.

Science.gov (United States)

Johnson, Jerry E; Perkins, Guy A; Giddabasappa, Anand; Chaney, Shawntay; Xiao, Weimin; White, Andrew D; Brown, Joshua M; Waggoner, Jenna; Ellisman, Mark H; Fox, Donald A

2007-06-15

stained for PMCA, whereas the larger cone pedicles preferentially stained for NCX1 at their active zones and PMCA near their mitochondria. EM and ET revealed that mitochondria in rod spherules and cone pedicles differed markedly in their number, location, size, volume, and total cristae surface area, and cristae junction diameter. Rod spherules had one large ovoid mitochondrion located near its active zone, whereas cone pedicles averaged five medium-sized mitochondria clustered far from their active zones. Most spherules had one ribbon synapse, whereas pedicles contained numerous ribbon synapses. Fluo-3 imaging studies revealed that during darkness rod spherules maintained a lower [Ca2+] than cone pedicles, whereas during light adaptation pedicles rapidly lowered their [Ca2+] below that observed in spherules. These findings indicate that ATP demand and mitochondrial ATP production are greater in cone pedicles than rod spherules. Rod spherules employ high affinity/low turnover PMCA and their mitochondrion to maintain a relatively low [Ca2+] in darkness, which increases their sensitivity and signal-to-noise ratio. In contrast, cone pedicles utilize low affinity/high turnover NCX to rapidly lower their high [Ca2+] during light adaptation, which increases their response kinetics. Spatiotemporal fluo-3-Ca2+ imaging results support our immunocytochemical results. The clustering of cone pedicle mitochondria likely provides increased protection from Ca2+ overload and permeability transition. In summary, these novel studies reveal that several integrated cellular and subcellular components interact to regulate ATP and Ca2+ dynamics in rod and cone synaptic terminals. These results should provide a greater understanding of in vivo photoreceptor synaptic terminal exocytosis/endocytosis, Ca2+ overload and therapies for retinal degenerations.

Volumetric analysis of the mandibular condyle using cone beam computed tomography

Energy Technology Data Exchange (ETDEWEB)

Bayram, Mehmet, E-mail: dtmehmetbayram@yahoo.com [Karadeniz Technical University, Faculty of Dentistry, Department of Orthodontics, 61080 Trabzon (Turkey); Kayipmaz, Saadettin; Sezgin, Oemer Said [Karadeniz Technical University, Faculty of Dentistry, Department of Oral Radiology, Trabzon (Turkey); Kuecuek, Murat [Karadeniz Technical University, Faculty of Arts and Sciences, Department of Chemistry, Trabzon (Turkey)

2012-08-15

Objective: The aim was to determine the accuracy of volumetric analysis of the mandibular condyle using cone-beam computed tomography (CBCT). Materials and methods: Five dry mandibles containing 9 condyles were used. CBCT scans of the mandibles and an impression of each condylar area were taken. The physical volumes of the condyles were calculated as the gold standard using the water displacement technique. After isolating, the condylar volume was sectioned in the sagittal plane, and 0.3 mm thick sections with 0.9 mm intervals were obtained from 3D reconstructions. Using the Cavalieri principle, the volume of each condyle was estimated from the CBCT images by three observers. The accuracy of the CBCT volume measurements and the relation agreements between the results of the three observers were assessed using the Wilcoxon Signed Rank test and Pearson correlation test. The level of statistical significance was set at 0.05. Results: The results of the Pearson correlation showed that there were highly significant positive correlations between the observers' measurements. According to the results of the Wilcoxon Signed Rank test comparing the physical and observers' measurements, there were no statistically significant differences (p > 0.05). Conclusion: The Cavalieri principle, used in conjunction with a planimetry method, is a valid and effective method for volume estimation of the mandibular condyle on CBCT images.

Volumetric analysis of the mandibular condyle using cone beam computed tomography

International Nuclear Information System (INIS)

Bayram, Mehmet; Kayipmaz, Saadettin; Sezgin, Ömer Said; Küçük, Murat

2012-01-01

Objective: The aim was to determine the accuracy of volumetric analysis of the mandibular condyle using cone-beam computed tomography (CBCT). Materials and methods: Five dry mandibles containing 9 condyles were used. CBCT scans of the mandibles and an impression of each condylar area were taken. The physical volumes of the condyles were calculated as the gold standard using the water displacement technique. After isolating, the condylar volume was sectioned in the sagittal plane, and 0.3 mm thick sections with 0.9 mm intervals were obtained from 3D reconstructions. Using the Cavalieri principle, the volume of each condyle was estimated from the CBCT images by three observers. The accuracy of the CBCT volume measurements and the relation agreements between the results of the three observers were assessed using the Wilcoxon Signed Rank test and Pearson correlation test. The level of statistical significance was set at 0.05. Results: The results of the Pearson correlation showed that there were highly significant positive correlations between the observers’ measurements. According to the results of the Wilcoxon Signed Rank test comparing the physical and observers’ measurements, there were no statistically significant differences (p > 0.05). Conclusion: The Cavalieri principle, used in conjunction with a planimetry method, is a valid and effective method for volume estimation of the mandibular condyle on CBCT images.

Cinder cones of Mount Slamet, Central Java, Indonesia

Directory of Open Access Journals (Sweden)

Igan S. SutawIdjaja

2014-06-01

Full Text Available http://dx.doi.org/10.17014/ijog.vol4no1.20096The Mount Slamet volcanic field in Central Java, Indonesia, contains thirty five cinder cones within an area of 90 sq. km in the east flank of the volcano. The cinder cones occur singly or in small groups, with diameter of the base ranges from 130 - 750 m and the height is around 250 m. Within the volcanic field, the cinder cones are spread over the volcanic area at the distance of 4 to 14 km from the eruption center of the Slamet Volcano. They are concentrated within latitudes 7°11’00” - 7°16’00” S,, and longitudes 109°15’00” - 109°18’00” E. The density of the cinder cones is about 1.5 cones/km2. Most of the cinder cones lie on the Tertiary sedimentary rocks along the NW-trending fault system and on radial fractures. The structural pattern may be related to the radial faults in this region. The cone surfaces are commonly blanketed by Slamet air-falls and lava flows. The deposits consist of poorly bedded, very coarse-grained, occasionally overlain by oxidized scoria, and large-sized of ballistic bombs and blocks. There are various kind of volcanic bombs originating from scoriae ballistic rock fragments. The other kind of volcanic bombs are breadcrust bomb, almond seed or contorted shape. All of the cinder cones have undergone degradation, which can be observed from the characters of gully density and surface morphology. By using Porter parameters, Hco is equal to 0.25 Wco, whilst Wcr is equal to 0.40 Wco. The Hco/Wco ratio is higher than Hco = 0.2 Wco reference line. A radiometric dating using K-Ar method carried out on a scoria bomb yields the age of 0.042 + 0.020 Ma.  

Morphometric analysis - Cone beam computed tomography to predict bone quality and quantity.

Science.gov (United States)

Hohlweg-Majert, B; Metzger, M C; Kummer, T; Schulze, D

2011-07-01

Modified quantitative computed tomography is a method used to predict bone quality and quantify the bone mass of the jaw. The aim of this study was to determine whether bone quantity or quality was detected by cone beam computed tomography (CBCT) combined with image analysis. MATERIALS AND PROCEDURES: Different measurements recorded on two phantoms (Siemens phantom, Comac phantom) were evaluated on images taken with the Somatom VolumeZoom (Siemens Medical Solutions, Erlangen, Germany) and the NewTom 9000 (NIM s.r.l., Verona, Italy) in order to calculate a calibration curve. The spatial relationships of six sample cylinders and the repositioning from four pig skull halves relative to adjacent defined anatomical structures were assessed by means of three-dimensional visualization software. The calibration curves for computer tomography (CT) and cone beam computer tomography (CBCT) using the Siemens phantom showed linear correlation in both modalities between the Hounsfield Units (HU) and bone morphology. A correction factor for CBCT was calculated. Exact information about the micromorphology of the bone cylinders was only available using of micro computer tomography. Cone-beam computer tomography is a suitable choice for analysing bone mass, but, it does not give any information about bone quality. 2010 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Analysis of macular cone photoreceptors in a case of occult macular dystrophy

Directory of Open Access Journals (Sweden)

Tojo N

2013-05-01

Full Text Available Naoki Tojo Tomoko Nakamura Hironori Ozaki Miyako Oka Toshihiko Oiwake Atsushi HayashiDepartment of Ophthalmology, University of Toyama, Toyama, JapanPurpose: To investigate changes in cone photoreceptors with adaptive optics (AO fundus imaging and spectral domain optical coherence tomography (SD-OCT in a case of occult macular dystrophy (OMD.Patient and methods: Both eyes of a 42-year-old woman diagnosed with OMD were examined. We used an AO fundus camera to obtain images of cone photoreceptors in the macula of the OMD subject and five healthy control subjects. Correlations between the AO images and the SD-OCT images were examined. Cone photoreceptors in eight areas in the macula of OMD and healthy control subjects were analyzed and compared.Results: SD-OCT showed a loss of the cone outer-segment tips line outside of the fovea in both eyes of the subject with OMD. The left eye with decreased visual acuity showed a discontinuous photoreceptor inner-segment and outer-segment line and cone outer-segment tips line at the fovea in SD-OCT and loss of cone mosaics as a dark spot in the AO image. In panoramic AO images and cone-density maps, less cone density was observed in a ring-like region outside the fovea than in the peripheral retina. In most of the areas examined, the cone densities were lower in the OMD eyes than in the healthy control eyes.Conclusions: Cone densities in the macula of the OMD patient were greatly decreased. AO images were found to be useful to evaluate morphologic changes in cone photoreceptors in patients with OMD.Keywords: occult macular dystrophy, adaptive optics, cone photoreceptor, cone analysis, optical coherence tomography

Pulmonary nodule registration in serial CT scans based on rib anatomy and nodule template matching

International Nuclear Information System (INIS)

Shi Jiazheng; Sahiner, Berkman; Chan, H.-P.; Hadjiiski, Lubomir; Zhou, C.; Cascade, Philip N.; Bogot, Naama; Kazerooni, Ella A.; Wu, Y.-T.; Wei, J.

2007-01-01

An automated method is being developed in order to identify corresponding nodules in serial thoracic CT scans for interval change analysis. The method uses the rib centerlines as the reference for initial nodule registration. A spatially adaptive rib segmentation method first locates the regions where the ribs join the spine, which define the starting locations for rib tracking. Each rib is tracked and locally segmented by expectation-maximization. The ribs are automatically labeled, and the centerlines are estimated using skeletonization. For a given nodule in the source scan, the closest three ribs are identified. A three-dimensional (3D) rigid affine transformation guided by simplex optimization aligns the centerlines of each of the three rib pairs in the source and target CT volumes. Automatically defined control points along the centerlines of the three ribs in the source scan and the registered ribs in the target scan are used to guide an initial registration using a second 3D rigid affine transformation. A search volume of interest (VOI) is then located in the target scan. Nodule candidate locations within the search VOI are identified as regions with high Hessian responses. The initial registration is refined by searching for the maximum cross-correlation between the nodule template from the source scan and the candidate locations. The method was evaluated on 48 CT scans from 20 patients. Experienced radiologists identified 101 pairs of corresponding nodules. Three metrics were used for performance evaluation. The first metric was the Euclidean distance between the nodule centers identified by the radiologist and the computer registration, the second metric was a volume overlap measure between the nodule VOIs identified by the radiologist and the computer registration, and the third metric was the hit rate, which measures the fraction of nodules whose centroid computed by the computer registration in the target scan falls within the VOI identified by the

Revision total knee arthroplasty with the use of trabecular metal cones

DEFF Research Database (Denmark)

Jensen, Claus L; Petersen, Michael Mygind; Schrøder, Henrik

2012-01-01

"Trabecular Metal Cone" (TM Cone) (Zimmer, Inc, Warsaw, Ind) for reconstruction of bone loss in the proximal tibia during revision total knee arthroplasty is now optional. Forty patients were randomized to receive revision total knee arthroplasty with or without TM Cone (No TM Cone). The Anderson...

Occurrence of maxillary sinus abnormalities detected by cone beam CT in asymptomatic patients

Directory of Open Access Journals (Sweden)

Rege Inara Carneiro

2012-08-01

Full Text Available Abstract Background Although cone beam computed tomography (CBCT images of the maxillofacial region allow the inspection of the entire volume of the maxillary sinus (MS, identifying anatomic variations and abnormalities in the image volume, this is frequently neglected by oral radiologists when interpreting images of areas at a distance from the dentoalveolar region, such as the full anatomical aspect of the MS. The aim of this study was to investigate maxillary sinus abnormalities in asymptomatic patients by using CBCT. Methods 1113 CBCT were evaluated by two examiners and identification of abnormalities, the presence of periapical lesions and proximity to the lower sinus wall were recorded. Data were analyzed using descriptive statistics, chi-square tests and Kappa statistics. Results Abnormalities were diagnosed in 68.2% of cases (kappa = 0.83. There was a significant difference between genders (p Conclusions Abnormalities in maxillary sinus emphasizes how important it is for the dentomaxillofacial radiologist to undertake an interpretation of the whole volume of CBCT images.

Cone dystrophy with "supernormal" rod ERG: psychophysical testing shows comparable rod and cone temporal sensitivity losses with no gain in rod function.

Science.gov (United States)

Stockman, Andrew; Henning, G Bruce; Michaelides, Michel; Moore, Anthony T; Webster, Andrew R; Cammack, Jocelyn; Ripamonti, Caterina

2014-02-10

We report a psychophysical investigation of 5 observers with the retinal disorder "cone dystrophy with supernormal rod ERG," caused by mutations in the gene KCNV2 that encodes a voltage-gated potassium channel found in rod and cone photoreceptors. We compared losses for rod- and for cone-mediated vision to further investigate the disorder and to assess whether the supernormal ERG is associated with any visual benefit. L-cone, S-cone, and rod temporal acuity (critical flicker fusion frequency) were measured as a function of target irradiance; L-cone temporal contrast sensitivity was measured as a function of temporal frequency. Temporal acuity measures revealed that losses for vision mediated by rods, S-cones, and L-cones are roughly equivalent. Further, the gain in rod function implied by the supernormal ERG provides no apparent benefit to near-threshold rod-mediated visual performance. The L-cone temporal contrast sensitivity function in affected observers was similar in shape to the mean normal function but only after the mean function was compressed by halving the logarithmic sensitivities. The name of this disorder is potentially misleading because the comparable losses found across rod and cone vision suggest that the disorder is a generalized cone-rod dystrophy. Temporal acuity and temporal contrast sensitivity measures are broadly consistent with the defect in the voltage-gated potassium channel producing a nonlinear distortion of the photoreceptor response but after otherwise normal transduction processes.

Semi-automated segmentation of a glioblastoma multiforme on brain MR images for radiotherapy planning.

Science.gov (United States)

Hori, Daisuke; Katsuragawa, Shigehiko; Murakami, Ryuuji; Hirai, Toshinori

2010-04-20

We propose a computerized method for semi-automated segmentation of the gross tumor volume (GTV) of a glioblastoma multiforme (GBM) on brain MR images for radiotherapy planning (RTP). Three-dimensional (3D) MR images of 28 cases with a GBM were used in this study. First, a sphere volume of interest (VOI) including the GBM was selected by clicking a part of the GBM region in the 3D image. Then, the sphere VOI was transformed to a two-dimensional (2D) image by use of a spiral-scanning technique. We employed active contour models (ACM) to delineate an optimal outline of the GBM in the transformed 2D image. After inverse transform of the optimal outline to the 3D space, a morphological filter was applied to smooth the shape of the 3D segmented region. For evaluation of our computerized method, we compared the computer output with manually segmented regions, which were obtained by a therapeutic radiologist using a manual tracking method. In evaluating our segmentation method, we employed the Jaccard similarity coefficient (JSC) and the true segmentation coefficient (TSC) in volumes between the computer output and the manually segmented region. The mean and standard deviation of JSC and TSC were 74.2+/-9.8% and 84.1+/-7.1%, respectively. Our segmentation method provided a relatively accurate outline for GBM and would be useful for radiotherapy planning.

Brain SPECT with short focal-length cone-beam collimation

International Nuclear Information System (INIS)

Park, Mi-Ae; Moore, Stephen C.; Kijewski, Marie Foley

2005-01-01

Single-photon emission-computed tomography (SPECT) imaging of deep brain structures is compromised by loss of photons due to attenuation. We have previously shown that a centrally peaked collimator sensitivity function can compensate for this phenomenon, increasing sensitivity over most of the brain. For dual-head instruments, parallel-hole collimators cannot provide variable sensitivity without simultaneously degrading spatial resolution near the center of the brain; this suggests the use of converging collimators. We have designed collimator pairs for dual-head SPECT systems to increase sensitivity, particularly in the center of the brain, and compared the new collimation approach to existing approaches on the basis of performance in estimating activity concentration of small structures at various locations in the brain. The collimator pairs we evaluated included a cone-beam collimator, for increased sensitivity, and a fan-beam collimator, for data sufficiency. We calculated projections of an ellipsoidal uniform background, with 0.9-cm-radius spherical lesions at several locations in the background. From these, we determined ideal signal-to-noise ratios (SNR CRB ) for estimation of activity concentration within the spheres, based on the Cramer-Rao lower bound on variance. We also reconstructed, by an ordered-subset expectation-maximization (OS-EM) procedure, images of this phantom, as well as of the Zubal brain phantom, to allow visual assessment and to ensure that they were free of artifacts. The best of the collimator pairs evaluated comprised a cone-beam collimator with 20 cm focal length, for which the focal point is inside the brain, and a fan-beam collimator with 40 cm focal length. This pair yielded increased SNR CRB , compared to the parallel-parallel pair, throughout the imaging volume. The factor by which SNR CRB increased ranged from 1.1 at the most axially extreme location to 3.5 at the center. The gains in SNR CRB were relatively robust to mismatches

The uniqueness of the solution of cone-like inversion models for halo CMEs

Science.gov (United States)

Zhao, X. P.

2006-12-01

Most of elliptic halo CMEs are believed to be formed by the Thompson scattering of the photospheric light by the 3-D cone-like shell of the CME plasma. To obtain the real propagation direction and angular width of the halo CMEs, such cone-like inversion models as the circular cone, the elliptic cone and the ice-cream cone models have been suggested recently. Because the number of given parameters that are used to characterize 2-D elliptic halo CMEs observed by one spacecraft are less than the number of unknown parameters that are used to characterize the 3-D elliptic cone model, the solution of the elliptic cone model is not unique. Since it is difficult to determine whether or not an observed halo CME is formed by an circular cone or elliptic cone shell, the solution of circular cone model may often be not unique too. To fix the problem of the uniqueness of the solution of various 3-D cone-like inversion models, this work tries to develop the algorithm for using the data from multi-spacecraft, such as the STEREO A and B, and the Solar Sentinels.

Reionization on large scales. IV. Predictions for the 21 cm signal incorporating the light cone effect

Energy Technology Data Exchange (ETDEWEB)

La Plante, P.; Battaglia, N.; Natarajan, A.; Peterson, J. B.; Trac, H. [McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Cen, R. [Department of Astrophysical Science, Princeton University, Princeton, NJ 08544 (United States); Loeb, A., E-mail: plaplant@andrew.cmu.edu [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)

2014-07-01

We present predictions for the 21 cm brightness temperature power spectrum during the Epoch of Reionization (EoR). We discuss the implications of the 'light cone' effect, which incorporates evolution of the neutral hydrogen fraction and 21 cm brightness temperature along the line of sight. Using a novel method calibrated against radiation-hydrodynamic simulations, we model the neutral hydrogen density field and 21 cm signal in large volumes (L = 2 Gpc h {sup –1}). The inclusion of the light cone effect leads to a relative decrease of about 50% in the 21 cm power spectrum on all scales. We also find that the effect is more prominent at the midpoint of reionization and later. The light cone effect can also introduce an anisotropy along the line of sight. By decomposing the 3D power spectrum into components perpendicular to and along the line of sight, we find that in our fiducial reionization model, there is no significant anisotropy. However, parallel modes can contribute up to 40% more power for shorter reionization scenarios. The scales on which the light cone effect is relevant are comparable to scales where one measures the baryon acoustic oscillation. We argue that due to its large comoving scale and introduction of anisotropy, the light cone effect is important when considering redshift space distortions and future application to the Alcock-Paczyński test for the determination of cosmological parameters.

Comparative study of pulsed-continuous arterial spin labeling and dynamic susceptibility contrast imaging by histogram analysis in evaluation of glial tumors.

Science.gov (United States)

Arisawa, Atsuko; Watanabe, Yoshiyuki; Tanaka, Hisashi; Takahashi, Hiroto; Matsuo, Chisato; Fujiwara, Takuya; Fujiwara, Masahiro; Fujimoto, Yasunori; Tomiyama, Noriyuki

2018-06-01

Arterial spin labeling (ASL) is a non-invasive perfusion technique that may be an alternative to dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) for assessment of brain tumors. To our knowledge, there have been no reports on histogram analysis of ASL. The purpose of this study was to determine whether ASL is comparable with DSC-MRI in terms of differentiating high-grade and low-grade gliomas by evaluating the histogram analysis of cerebral blood flow (CBF) in the entire tumor. Thirty-four patients with pathologically proven glioma underwent ASL and DSC-MRI. High-signal areas on contrast-enhanced T 1 -weighted images or high-intensity areas on fluid-attenuated inversion recovery images were designated as the volumes of interest (VOIs). ASL-CBF, DSC-CBF, and DSC-cerebral blood volume maps were constructed and co-registered to the VOI. Perfusion histogram analyses of the whole VOI and statistical analyses were performed to compare the ASL and DSC images. There was no significant difference in the mean values for any of the histogram metrics in both of the low-grade gliomas (n = 15) and the high-grade gliomas (n = 19). Strong correlations were seen in the 75th percentile, mean, median, and standard deviation values between the ASL and DSC images. The area under the curve values tended to be greater for the DSC images than for the ASL images. DSC-MRI is superior to ASL for distinguishing high-grade from low-grade glioma. ASL could be an alternative evaluation method when DSC-MRI cannot be used, e.g., in patients with renal failure, those in whom repeated examination is required, and in children.

Comparison of the WSA-ENLIL model with three CME cone types

Science.gov (United States)

Jang, Soojeong; Moon, Y.; Na, H.

2013-07-01

We have made a comparison of the CME-associated shock propagation based on the WSA-ENLIL model with three cone types using 29 halo CMEs from 2001 to 2002. These halo CMEs have cone model parameters as well as their associated interplanetary (IP) shocks. For this study we consider three different cone types (an asymmetric cone model, an ice-cream cone model and an elliptical cone model) to determine 3-D CME parameters (radial velocity, angular width and source location), which are the input values of the WSA-ENLIL model. The mean absolute error (MAE) of the arrival times for the asymmetric cone model is 10.6 hours, which is about 1 hour smaller than those of the other models. Their ensemble average of MAE is 9.5 hours. However, this value is still larger than that (8.7 hours) of the empirical model of Kim et al. (2007). We will compare their IP shock velocities and densities with those from ACE in-situ measurements and discuss them in terms of the prediction of geomagnetic storms.Abstract (2,250 Maximum Characters): We have made a comparison of the CME-associated shock propagation based on the WSA-ENLIL model with three cone types using 29 halo CMEs from 2001 to 2002. These halo CMEs have cone model parameters as well as their associated interplanetary (IP) shocks. For this study we consider three different cone types (an asymmetric cone model, an ice-cream cone model and an elliptical cone model) to determine 3-D CME parameters (radial velocity, angular width and source location), which are the input values of the WSA-ENLIL model. The mean absolute error (MAE) of the arrival times for the asymmetric cone model is 10.6 hours, which is about 1 hour smaller than those of the other models. Their ensemble average of MAE is 9.5 hours. However, this value is still larger than that (8.7 hours) of the empirical model of Kim et al. (2007). We will compare their IP shock velocities and densities with those from ACE in-situ measurements and discuss them in terms of the

Cone Beam Computed Tomography Guidance for Setup of Patients Receiving Accelerated Partial Breast Irradiation

International Nuclear Information System (INIS)

White, Elizabeth A.; Cho, John; Vallis, Katherine A.; Sharpe, Michael B.; Lee, Grace B.Sc.; Blackburn, Helen; Nageeti, Tahani; McGibney, Carol; Jaffray, David A.

2007-01-01

Purpose: To evaluate the role of cone-beam CT (CBCT) guidance for setup error reduction and soft tissue visualization in accelerated partial breast irradiation (APBI). Methods and Materials: Twenty patients were recruited for the delivery of radiotherapy to the postoperative cavity (3850 cGy in 10 fractions over 5 days) using an APBI technique. Cone-beam CT data sets were acquired after an initial skin-mark setup and before treatment delivery. These were registered online using the ipsilateral lung and external contours. Corrections were executed for translations exceeding 3 mm. The random and systematic errors associated with setup using skin-marks and setup using CBCT guidance were calculated and compared. Results: A total of 315 CBCT data sets were analyzed. The systematic errors for the skin-mark setup were 2.7, 1.7, and 2.4 mm in the right-left, anterior-posterior, and superior-inferior directions, respectively. These were reduced to 0.8, 0.7, and 0.8 mm when CBCT guidance was used. The random errors were reduced from 2.4, 2.2, and 2.9 mm for skin-marks to 1.5, 1.5, and 1.6 mm for CBCT guidance in the right-left, anterior-posterior, and superior-inferior directions, respectively. Conclusion: A skin-mark setup for APBI patients is sufficient for current planning target volume margins for the population of patients studied here. Online CBCT guidance minimizes the occurrence of large random deviations, which may have a greater impact for the accelerated fractionation schedule used in APBI. It is also likely to permit a reduction in planning target volume margins and provide skin-line visualization and dosimetric evaluation of cardiac and lung volumes

CRALBP supports the mammalian retinal visual cycle and cone vision.

Science.gov (United States)

Xue, Yunlu; Shen, Susan Q; Jui, Jonathan; Rupp, Alan C; Byrne, Leah C; Hattar, Samer; Flannery, John G; Corbo, Joseph C; Kefalov, Vladimir J

2015-02-01

Mutations in the cellular retinaldehyde-binding protein (CRALBP, encoded by RLBP1) can lead to severe cone photoreceptor-mediated vision loss in patients. It is not known how CRALBP supports cone function or how altered CRALBP leads to cone dysfunction. Here, we determined that deletion of Rlbp1 in mice impairs the retinal visual cycle. Mice lacking CRALBP exhibited M-opsin mislocalization, M-cone loss, and impaired cone-driven visual behavior and light responses. Additionally, M-cone dark adaptation was largely suppressed in CRALBP-deficient animals. While rearing CRALBP-deficient mice in the dark prevented the deterioration of cone function, it did not rescue cone dark adaptation. Adeno-associated virus-mediated restoration of CRALBP expression specifically in Müller cells, but not retinal pigment epithelial (RPE) cells, rescued the retinal visual cycle and M-cone sensitivity in knockout mice. Our results identify Müller cell CRALBP as a key component of the retinal visual cycle and demonstrate that this pathway is important for maintaining normal cone-driven vision and accelerating cone dark adaptation.

Segmentation process significantly influences the accuracy of 3D surface models derived from cone beam computed tomography

NARCIS (Netherlands)

Fourie, Zacharias; Damstra, Janalt; Schepers, Rutger H; Gerrits, Pieter; Ren, Yijin

AIMS: To assess the accuracy of surface models derived from 3D cone beam computed tomography (CBCT) with two different segmentation protocols. MATERIALS AND METHODS: Seven fresh-frozen cadaver heads were used. There was no conflict of interests in this study. CBCT scans were made of the heads and 3D

Evaluation of Skin Dose and Image Quality on Cone Beam Computed Tomography

International Nuclear Information System (INIS)

Ahn, Jong Ho; Hong, Chae Seon; Kim, Jin Man; Jang, Jun Young

2008-01-01

Cone-beam CT using linear accelerator attached to on-board imager is a image guided therapy equipment. Because it is to check the patient's set-up error, correction, organ and target movement. But imaging dose should be cause of the secondary cancer when taking a image. The aim of this study is investigation of appropriate cone beam CT scan mode to compare and estimate the image quality and skin dose. Measurement by Thermoluminescence dosimeter (TLD-100, Harshaw) with using the Rando phantom are placed on each eight sites in separately H and N, thoracic, abdominal section. each 4 methods of scan modes of are measured the for skin dose in three time. Subsequently, obtained average value. Following image quality QA protocol of equipment manufacturers using the catphan 504 phantom, image quality of each scan mode is compared and analyzed. The results of the measured skin dose are described in here. The skin dose of Head and Neck are measured mode A: 8.96 cGy, mode B: 4.59 cGy, mode C: 3.46 cGy mode D: 1.76 cGy and thoracic mode A: 9.42 cGy, mode B: 4.58 cGy, mode C: 3.65 cGy, mode D: 1.85 cGy, and abdominal mode A: 9.97 cGy, mode B: 5.12 cGy, mode C: 4.03 cGy, mode D: 2.21 cGy. Approximately, dose of mode B are reduced 50%, mode C are reduced 60%, mode D are reduced 80% a point of reference dose of mode A. the results of analyzed HU reproducibility, low contrast resolution, spatial resolution (high contrast resolution), HU uniformity in evaluation item of image quality are within the tolerance value by recommended equipment manufacturer in all scan mode. Maintaining the image quality as well as reducing the image dose are very important in cone beam CT. In the result of this study, we are considered when to take mode A when interested in soft tissue. And we are considered to take mode D when interested in bone scan and we are considered to take mode B, C when standard scan. Increasing secondary cancer risk due to cone beam CT scan should be reduced by low m

A cone-beam reconstruction algorithm using shift-variant filtering and cone-beam backprojection

International Nuclear Information System (INIS)

Defrise, M.; Clack, R.

1994-01-01

An exact inversion formula written in the form of shift-variant filtered-backprojection (FBP) is given for reconstruction from cone-beam data taken from any orbit satisfying Tuy's sufficiency conditions. The method is based on a result of Grangeat, involving the derivative of the three-dimensional (3-D) Radon transform, but unlike Grangeat's algorithm, no 3D rebinning step is required. Data redundancy, which occurs when several cone-beam projections supply the same values in the Radon domain, is handled using an elegant weighting function and without discarding data. The algorithm is expressed in a convenient cone-beam detector reference frame, and a specific example for the case of a dual orthogonal circular orbit is presented. When the method is applied to a single circular orbit, it is shown to be equivalent to the well-known algorithm of Feldkamp et al

The characteristics of cortical glucose metabolism in amblyopia

Energy Technology Data Exchange (ETDEWEB)

Ahn, Ji Young [College of Medicine, Seoul National Univ., Seoul (Korea, Republic of); Lee, Dong Soo; Chung, June Key; Shin, Seung Ai; Lee, Myung Chul [College of Medicine, Ewha Womans Univ., Seoul (Korea, Republic of)

2000-07-01

Cortical metabolism of amblyopia patients was investigated with F-18-FDG PET and Statistical Parametric Mapping (SPM) and quantificiation based on volume of interest (VOI) by statistical probabilistic anatomical map (SPAM). In 9 amblyopic patients (12{+-}7 years ) and 20 normal subjects (23{+-}2 years), F-18-FDG PET scans were peformed in amblyopic patients after amblyopic eye or sound eye was patch-closed during PET studies. SPM was done with SPM96. By multiplying SPAM to FDG images, counts of 98 VOI's were calculated and compared with 3 S. D. range of those of normal subjects. On SPM, cortical metabolism decreased (p<0.05) in occipital lobe (Ba 17, 18, 19), superior partietal lobe (Ba 7), and inferior temporal lobe (BA 37, 20). FDG uptake of gyri of occuipital lobe was decreased in 2 and increased in 2, and was normal in the other 5. FDG uptake of gyri of parietal, frontal, and temporal lobes were decreased in FDG uptake on these VOIs. We conclude that cortical metabolism in occipital lobe and extraoccipital lobes was variable but was consistent regardless of visual input during PET studies in amblyopic patients. SPM and quantification of functional images using SPAM could reveal subtle differences or changes according to visual input. The significance of metabolic changes of extraoccipital lobes should be studies further.

The characteristics of cortical glucose metabolism in amblyopia

International Nuclear Information System (INIS)

Ahn, Ji Young; Lee, Dong Soo; Chung, June Key; Shin, Seung Ai; Lee, Myung Chul

2000-01-01

Cortical metabolism of amblyopia patients was investigated with F-18-FDG PET and Statistical Parametric Mapping (SPM) and quantificiation based on volume of interest (VOI) by statistical probabilistic anatomical map (SPAM). In 9 amblyopic patients (12±7 years ) and 20 normal subjects (23±2 years), F-18-FDG PET scans were peformed in amblyopic patients after amblyopic eye or sound eye was patch-closed during PET studies. SPM was done with SPM96. By multiplying SPAM to FDG images, counts of 98 VOI's were calculated and compared with 3 S. D. range of those of normal subjects. On SPM, cortical metabolism decreased (p<0.05) in occipital lobe (Ba 17, 18, 19), superior partietal lobe (Ba 7), and inferior temporal lobe (BA 37, 20). FDG uptake of gyri of occuipital lobe was decreased in 2 and increased in 2, and was normal in the other 5. FDG uptake of gyri of parietal, frontal, and temporal lobes were decreased in FDG uptake on these VOIs. We conclude that cortical metabolism in occipital lobe and extraoccipital lobes was variable but was consistent regardless of visual input during PET studies in amblyopic patients. SPM and quantification of functional images using SPAM could reveal subtle differences or changes according to visual input. The significance of metabolic changes of extraoccipital lobes should be studies further

Clinical Evaluation of Zero-Echo-Time Attenuation Correction for Brain 18F-FDG PET/MRI: Comparison with Atlas Attenuation Correction.

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Sekine, Tetsuro; Ter Voert, Edwin E G W; Warnock, Geoffrey; Buck, Alfred; Huellner, Martin; Veit-Haibach, Patrick; Delso, Gaspar

2016-12-01

Accurate attenuation correction (AC) on PET/MR is still challenging. The purpose of this study was to evaluate the clinical feasibility of AC based on fast zero-echo-time (ZTE) MRI by comparing it with the default atlas-based AC on a clinical PET/MR scanner. We recruited 10 patients with malignant diseases not located on the brain. In all patients, a clinically indicated whole-body 18 F-FDG PET/CT scan was acquired. In addition, a head PET/MR scan was obtained voluntarily. For each patient, 2 AC maps were generated from the MR images. One was atlas-AC, derived from T1-weighted liver acquisition with volume acceleration flex images (clinical standard). The other was ZTE-AC, derived from proton-density-weighted ZTE images by applying tissue segmentation and assigning continuous attenuation values to the bone. The AC map generated by PET/CT was used as a silver standard. On the basis of each AC map, PET images were reconstructed from identical raw data on the PET/MR scanner. All PET images were normalized to the SPM5 PET template. After that, these images were qualified visually and quantified in 67 volumes of interest (VOIs; automated anatomic labeling, atlas). Relative differences and absolute relative differences between PET images based on each AC were calculated. 18 F-FDG uptake in all 670 VOIs and generalized merged VOIs were compared using a paired t test. Qualitative analysis shows that ZTE-AC was robust to patient variability. Nevertheless, misclassification of air and bone in mastoid and nasal areas led to the overestimation of PET in the temporal lobe and cerebellum (%diff of ZTE-AC, 2.46% ± 1.19% and 3.31% ± 1.70%, respectively). The |%diff| of all 670 VOIs on ZTE was improved by approximately 25% compared with atlas-AC (ZTE-AC vs. atlas-AC, 1.77% ± 1.41% vs. 2.44% ± 1.63%, P PET in regions near the skull base. © 2016 by the Society of Nuclear Medicine and Molecular Imaging, Inc.

Rapid Recovery of Visual Function Associated with Blue Cone Ablation in Zebrafish

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