Energy Technology Data Exchange (ETDEWEB)
Kwag, Eujean; Lim, Soo Mee; Park, Ji Eun; Chae, In Hye [Ewha Womans University School of Medicine, Department of Radiology, Mokdong Hospital, Seoul (Korea, Republic of)
2014-09-15
To evaluate the utility of BLADE fluid-attenuated inversion recovery images (FLAIR) magnetic resonance (MR) imaging compared to conventional FLAIR for the detection of arterial hyperintensity (AH) in hyperacute territorial infarction. We retrospectively analysed MR images of patients with hyperacute (<6 h) territorial infarction over a 9-month study period. Special attention was paid to the presence or absence of AH in the frontal, parietal and temporal lobes and the number of AHs in the sylvian fissure. We also evaluated the presence of three kinds of artefacts on BLADE FLAIR and conventional FLAIR images. AH was seen in 41 (91 %) patients with conventional FLAIR and 45 (100 %) patients with BLADE FLAIR images. More instances of AH were detected in the frontal, parietal and temporal lobes and within the sylvian fissure using BLADE FLAIR. Motion artefacts, pulsation artefacts from the sigmoid sinus and incomplete cerebrospinal fluid (CSF) nulling that reduced image quality were observed more frequently on conventional FLAIR images than on BLADE FLAIR images. BLADE FLAIR sequences are more sensitive than conventional FLAIR for the detection of AH in hyperacute territorial infarctions and provide better image quality by reducing artefacts. They may be used in place of conventional FLAIR for patients with hyperacute stroke. (orig.)
Directory of Open Access Journals (Sweden)
Soo Chin Kim
Full Text Available PURPOSE: To evaluate whether adding a contrast-enhanced fluid-attenuated inversion recovery (FLAIR sequence to routine magnetic resonance imaging (MRI can detect additional abnormalities in the brains of symptomatic patients with mild traumatic brain injury. MATERIALS AND METHODS: Fifty-four patients with persistent symptoms following mild closed head injury were included in our retrospective study (M ∶ F = 32 ∶ 22, mean age: 59.8 ± 16.4, age range: 26-84 years. All MRI examinations were obtained within 14 days after head trauma (mean: 3.2 ± 4.1 days, range: 0.2-14 days. Two neuroradiologists recorded (1 the presence of traumatic brain lesions on MR images with and without contrast-enhanced FLAIR images and (2 the pattern and location of meningeal enhancement depicted on contrast-enhanced FLAIR images. The number of additional traumatic brain lesions diagnosed with contrast-enhanced FLAIR was recorded. Correlations between meningeal enhancement and clinical findings were also evaluated. RESULTS: Traumatic brain lesions were detected on routine image sequences in 25 patients. Three additional cases of brain abnormality were detected with the contrast-enhanced FLAIR images. Meningeal enhancement was identified on contrast-enhanced FLAIR images in 9 cases while the other routine image sequences showed no findings of traumatic brain injury. Overall, the additional contrast-enhanced FLAIR images revealed more extensive abnormalities than routine imaging in 37 cases (p<0.001. In multivariate logistic regression analysis, subdural hematoma and posttraumatic loss of consciousness showed a significant association with meningeal enhancement on contrast-enhanced FLAIR images, with odds ratios 13.068 (95% confidence interval 2.037 to 83.852, and 15.487 (95% confidence interval 2.545 to 94.228, respectively. CONCLUSION: Meningeal enhancement on contrast-enhanced FLAIR images can help detect traumatic brain lesions as well as additional abnormalities
Usefulness of turbo-fluid-attenuated inversion-recovery (tFLAIR) sequence in diagnosing meningioma
International Nuclear Information System (INIS)
Shimizu, Teruhiko; Miki, Hitoshi; Takeguchi, Takashi; Kikuchi, Keiichi; Mochizuki, Teruhito; Ikezoe, Junpei
2003-01-01
We evaluated qualitatively and quantitatively the usefulness of turbo-fluid-attenuated inversion-recovery (tFLAIR) in diagnosing meningioma in comparison with the T2-weighted turbo spin echo (T2W-TSE) sequence. Forty-eight patients diagnosed with meningioma were studied. In the qualitative study, we evaluated tumor delineation, contrast (Co) of tumor-to-CSF (cerebrospinal fluid), Co of tumor-to-brain parenchyma, Co of peripheral edema-to-brain parenchyma, and detectability of tumor margin. In quantitative study-1, using signal intensity (SI), we measured SI and calculated Co-SI of tumor-to-gray matter, Co-SI of tumor-to-white matter, Co-SI of peripheral edema-to-white matter, and Co-SI of tumor-to-CSF. In quantitative study-2, using film density, we measured density (De) on hard-copy film images and calculated Co-De for the same items as in quantitative study-1. In the qualitative study, tFLAIR was superior to T2W-TSE in tumor delineation, Co of tumor-to-CSF, Co of tumor-to-brain parenchyma, and Co of peripheral edema-to-brain parenchyma. In quantitative study-1, tFLAIR was superior to T2W-TSE in Co-SI of tumor-to-CSF, however, T2W-TSE was superior to tFLAIR in Co-SI of tumor-to-white matter. In quantitative study-2, tFLAIR was superior to T2W-TSE in all Co-De. tFLAIR was superior to T2W-TSE in the depiction of meningioma. (author)
Usefulness of turbo-fluid-attenuated inversion-recovery (tFLAIR) sequence in diagnosing meningioma
Energy Technology Data Exchange (ETDEWEB)
Shimizu, Teruhiko; Miki, Hitoshi; Takeguchi, Takashi; Kikuchi, Keiichi; Mochizuki, Teruhito; Ikezoe, Junpei [Ehime Univ., Shigenobu (Japan). School of Medicine
2003-04-01
We evaluated qualitatively and quantitatively the usefulness of turbo-fluid-attenuated inversion-recovery (tFLAIR) in diagnosing meningioma in comparison with the T2-weighted turbo spin echo (T2W-TSE) sequence. Forty-eight patients diagnosed with meningioma were studied. In the qualitative study, we evaluated tumor delineation, contrast (Co) of tumor-to-CSF (cerebrospinal fluid), Co of tumor-to-brain parenchyma, Co of peripheral edema-to-brain parenchyma, and detectability of tumor margin. In quantitative study-1, using signal intensity (SI), we measured SI and calculated Co-SI of tumor-to-gray matter, Co-SI of tumor-to-white matter, Co-SI of peripheral edema-to-white matter, and Co-SI of tumor-to-CSF. In quantitative study-2, using film density, we measured density (De) on hard-copy film images and calculated Co-De for the same items as in quantitative study-1. In the qualitative study, tFLAIR was superior to T2W-TSE in tumor delineation, Co of tumor-to-CSF, Co of tumor-to-brain parenchyma, and Co of peripheral edema-to-brain parenchyma. In quantitative study-1, tFLAIR was superior to T2W-TSE in Co-SI of tumor-to-CSF, however, T2W-TSE was superior to tFLAIR in Co-SI of tumor-to-white matter. In quantitative study-2, tFLAIR was superior to T2W-TSE in all Co-De. tFLAIR was superior to T2W-TSE in the depiction of meningioma. (author)
Energy Technology Data Exchange (ETDEWEB)
Hodel, Jerome; Bocher, Anne-Laure; Pruvo, Jean-Pierre; Leclerc, Xavier [Hopital Roger Salengro, Department of Neuroradiology, Lille (France); Outteryck, Olivier; Zephir, Helene; Vermersch, Patrick [Hopital Roger Salengro, Department of Neurology, Lille (France); Lambert, Oriane [Fondation Ophtalmologique Rothschild, Department of Neuroradiology, Paris (France); Benadjaoud, Mohamed Amine [Radiation Epidemiology Team, Inserm, CESP Centre for Research in Epidemiology and Population Health, U1018, Villejuif (France); Chechin, David [Philips Medical Systems, Suresnes (France)
2014-12-15
We compared the three-dimensional (3D) double inversion recovery (DIR) magnetic resonance imaging (MRI) sequence with the coronal two-dimensional (2D) short tau inversion recovery (STIR) fluid-attenuated inversion recovery (FLAIR) for the detection of optic nerve signal abnormality in patients with optic neuritis (ON). The study group consisted of 31 patients with ON (44 pathological nerves) confirmed by visual-evoked potentials used as the reference. MRI examinations included 2D coronal STIR FLAIR and 3D DIR with 3-mm coronal reformats to match with STIR FLAIR. Image artefacts were graded for each portion of the optic nerves. Each set of MR images (2D STIR FLAIR, DIR reformats and multiplanar 3D DIR) was examined independently and separately for the detection of signal abnormality. Cisternal portion of optic nerves was better delineated with DIR (p < 0.001), while artefacts impaired analysis in four patients with STIR FLAIR. Inter-observer agreement was significantly improved (p < 0.001) on 3D DIR (κ = 0.96) compared with STIR FLAIR images (κ = 0.60). Multiplanar DIR images reached the best performance for the diagnosis of ON (95 % sensitive and 94 % specific). Our study showed a high sensitivity and specificity of 3D DIR compared with STIR FLAIR for the detection of ON. These findings suggest that the 3D DIR sequence may be more useful in patients suspected of ON. (orig.)
International Nuclear Information System (INIS)
Sargent, M.A.; Poskitt, K.J.
1997-01-01
Purpose. To evaluate fast spin-echo and multi-shot echo-planar fluid-attenuated inversion recovery (FLAIR) sequences in paediatric brain imaging. Materials and methods. Matched images from 32 patients with suspected tumour or white matter disease were independently evaluated by two paediatric neuroradiologists. The observer preferences for image quality and lesion detection were analysed for differences between fast spin-echo FLAIR and multi-shot echo-planar FLAIR. Diagnostic quality was compared with that of fast spin-echo T2-weighted images. Results. Images of a diagnostic quality equivalent to that of fast spin-echo T2-weighted images were achieved with both FLAIR techniques. Grey and white matter differentiation and cerebrospinal fluid (CSF) nulling were significantly better on fast spin-echo FLAIR sequences. CSF flow artefact was reduced on multi-shot echo-planar FLAIR. There was no difference in lesion detection. Fast spin-echo FLAIR images were visually preferred at the expense of longer imaging time. Conclusion. Fast FLAIR techniques are complementary to fast spin-echo T2-weighted sequences in imaging of the paediatric brain. We find that the fast spin-echo FLAIR sequence is preferable to the multi-shot echo-planar technique. (orig.). With 5 figs., 2 tabs
Schreiner, Simon J.; Liu, Xinyang; Gietl, Anton F.; Wyss, Michael; Steininger, Stefanie C.; Gruber, Esmeralda; Treyer, Valerie; Meier, Irene B.; Kälin, Andrea M.; Leh, Sandra E.; Buck, Alfred; Nitsch, Roger M.; Pruessmann, Klaas P.; Hock, Christoph; Unschuld, Paul G.
2014-01-01
Background: Accumulation of amyloid beta (Aβ) may occur during healthy aging and is a risk factor for Alzheimer Disease (AD). While individual Aβ-accumulation can be measured non-invasively using Pittsburgh Compund-B positron emission tomography (PiB-PET), Fluid-attenuated inversion recovery (FLAIR) is a Magnetic Resonance Imaging (MRI) sequence, capable of indicating heterogeneous age-related brain pathologies associated with tissue-edema. In the current study cognitively normal elderly subjects were investigated for regional correlation of PiB- and FLAIR intensity. Methods: Fourteen healthy elderly subjects without known history of cognitive impairment received 11C-PiB-PET for estimation of regional Aβ-load. In addition, whole brain T1-MPRAGE and FLAIR-MRI sequences were acquired at high field strength of 7 Tesla (7T). Volume-normalized intensities of brain regions were assessed by applying an automated subcortical segmentation algorithm for spatial definition of brain structures. Statistical dependence between FLAIR- and PiB-PET intensities was tested using Spearman's rank correlation coefficient (rho), followed by Holm–Bonferroni correction for multiple testing. Results: Neuropsychological testing revealed normal cognitive performance levels in all participants. Mean regional PiB-PET and FLAIR intensities were normally distributed and independent. Significant correlation between volume-normalized PiB-PET signals and FLAIR intensities resulted for Hippocampus (right: rho = 0.86; left: rho = 0.84), Brainstem (rho = 0.85) and left Basal Ganglia vessel region (rho = 0.82). Conclusions: Our finding of a significant relationship between PiB- and FLAIR intensity mainly observable in the Hippocampus and Brainstem, indicates regional Aβ associated tissue-edema in cognitively normal elderly subjects. Further studies including clinical populations are necessary to clarify the relevance of our findings for estimating individual risk for age-related neurodegenerative
Directory of Open Access Journals (Sweden)
Simon J Schreiner
2014-09-01
Full Text Available Background: Accumulation of amyloid beta (Aβ may occur during healthy aging and is a risk factor for Alzheimer Disease (AD. While individual Aβ-accumulation can be measured non-invasively using Pittsburgh compound-B positron-emission-tomography (PiB-PET, Fluid-Attenuated Inversion Recovery (FLAIR is a Magnetic Resonance Imaging (MRI sequence, capable of indicating heterogeneous age-related brain pathologies associated with tissue-edema. In the current study cognitively normal elderly subjects were investigated for regional correlation of PiB- and FLAIR- intensity. Methods: 14 healthy elderly subjects without known history of cognitive impairment received 11C-PiB-PET for estimation of regional Aβ-load. In addition, whole brain T1-MPRAGE and FLAIR-MRI sequences were acquired at high field strength of 7 Tesla (7T. Volume-normalized intensities of brain regions were assessed by applying an automated subcortical segmentation algorithm for spatial definition of brain structures. Statistical dependence between FLAIR- and PiB-PET intensities was tested using Spearman's rank correlation coefficient (rho, followed by Holm-Bonferroni correction for multiple testing. Results: Neuropsychological testing revealed normal cognitive performance levels in all participants. Mean regional PiB-PET and FLAIR intensities were normally distributed and independent. Significant correlation between volume-normalized PiB-PET signals and FLAIR intensities resulted for Hippocampus (right:rho=0.86; left:rho=0.84, Brainstem (rho=0.85 and left Basal Ganglia vessel region (rho=0.82. Conclusions: Our finding of a significant relationship between PiB- and FLAIR-intensity mainly observable in the Hippocampus and Brainstem, indicates regional Aβ associated tissue-edema in cognitively normal elderly subjects. Further studies including clinical populations are necessary to clarify the relevance of our findings for estimating individual risk for age-related neurodegenerative
Energy Technology Data Exchange (ETDEWEB)
Kadowaki, Sachiko; Iwata, Osuke; Tamura, Masanori [Nagano Children' s Hospital, Toyoshina (Japan)] (and others)
2002-01-01
A follow-up study was performed to assess the correlation among the incidence of periventricular low intensities (PVLI) on MRI (magnetic resonance imaging) FLAIR (fluid attenuated inversion recovery) imaging, clinical evidence of perinatal insults that may cause white matter damage, and the outcome of the infants. We evaluated periventricular white matter lesions of 329 neonates whose MRI were obtained before two months corrected age. The detective rate of periventricular abnormalities on FLAIR imaging was significantly higher than that of T1-T2 weighted imaging. The most typical lesion detected on FLAIR imaging was periventricular low intensities (PVLI), frequently observed in the neonates with a history of preterm labour, very low birth weight, birth asphyxia and severe respiratory failure. Although we could not characterize the risk factors of PVLI, the incidence of PVLI had a strong correlation with the scores of motor and developmental tests at 12 and 36-months corrected age. In conclusion, FLAIR imaging, detecting the border zone damage of white matter, would be a strong tool to pick out neonates at high risk of neurological disturbances from those without clinical evidence of neurological insults in the neonatal period. (author)
Energy Technology Data Exchange (ETDEWEB)
Donmez, F.Y.; Aslan, H.; Coskun, M. (Dept. of Radiology, Faculty of Medicine, Baskent Univ., Ankara (Turkey))
2009-04-15
Background: Acute disseminated encephalomyelitis (ADEM) may be a rapidly progressive disease with different clinical outcomes. Purpose: To investigate the radiological findings of fulminant ADEM on diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) images, and to correlate these findings with clinical outcome. Material and Methods: Initial and follow-up magnetic resonance imaging (MRI) scans in eight patients were retrospectively evaluated for distribution of lesions on FLAIR images and presence of hemorrhage or contrast enhancement. DWI of the patients was evaluated as to cytotoxic versus vasogenic edema. The clinical records were analyzed, and MRI results and clinical outcome were correlated. Results: Four of the eight patients died, three had full recovery, and one had residual cortical blindness. The distribution of the hyperintense lesions on FLAIR sequence was as follows: frontal (37.5%), parietal (50%), temporal (37.5%), occipital (62.5%), basal ganglia (50%), pons (37.5%), mesencephalon (37.5%), and cerebellum (50%). Three of the patients who died had brainstem involvement. Two patients had a cytotoxic edema, one of whom died, and the other developed cortical blindness. Six patients had vasogenic edema: three of these patients had a rapid progression to coma and died; three of them recovered. Conclusion: DWI is not always helpful for evaluating the evolution or predicting the outcome of ADEM. However, extension of the lesions, particularly brainstem involvement, may have an influence on the prognosis.
International Nuclear Information System (INIS)
Donmez, F.Y.; Aslan, H.; Coskun, M.
2009-01-01
Background: Acute disseminated encephalomyelitis (ADEM) may be a rapidly progressive disease with different clinical outcomes. Purpose: To investigate the radiological findings of fulminant ADEM on diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) images, and to correlate these findings with clinical outcome. Material and Methods: Initial and follow-up magnetic resonance imaging (MRI) scans in eight patients were retrospectively evaluated for distribution of lesions on FLAIR images and presence of hemorrhage or contrast enhancement. DWI of the patients was evaluated as to cytotoxic versus vasogenic edema. The clinical records were analyzed, and MRI results and clinical outcome were correlated. Results: Four of the eight patients died, three had full recovery, and one had residual cortical blindness. The distribution of the hyperintense lesions on FLAIR sequence was as follows: frontal (37.5%), parietal (50%), temporal (37.5%), occipital (62.5%), basal ganglia (50%), pons (37.5%), mesencephalon (37.5%), and cerebellum (50%). Three of the patients who died had brainstem involvement. Two patients had a cytotoxic edema, one of whom died, and the other developed cortical blindness. Six patients had vasogenic edema: three of these patients had a rapid progression to coma and died; three of them recovered. Conclusion: DWI is not always helpful for evaluating the evolution or predicting the outcome of ADEM. However, extension of the lesions, particularly brainstem involvement, may have an influence on the prognosis
International Nuclear Information System (INIS)
Saini, Jitender; Kesavadas, Chandrasekharan; Thomas, Bejoy; Singh, Atampreet; Rathore, Chathurbhuj; Radhakrishnan, Ashalatha; Radhakrishnan, Kurupath; Bahuleyan, Biji
2010-01-01
Background: Focal cortical dysplasia (FCD) is often associated with epilepsy. Identification of FCD can be difficult due to subtle magnetic resonance imaging (MRI) changes. Though fluid-attenuated inversion recovery (FLAIR) sequence detects the majority of these lesions, smaller lesions may go unnoticed while larger lesions may be poorly delineated. Purpose: To determine the ability of a specialized epilepsy protocol in visualizing and delineating the extent of FCD. Material and Methods: We compared the imaging findings in nine patients with cortical malformation who underwent routine epilepsy MR imaging as well as a specialized epilepsy protocol. All imaging was done on a 1.5T MR unit. The specialized epilepsy protocol included 3D FLAIR in the sagittal plane as well as proton density (PD) and high-resolution T2-weighted (T2W) images in the transverse plane. Results: In all nine patients, the specialized protocol identified lesion anatomy better. In three patients in whom routine MRI was normal, the specialized epilepsy protocol including 3D FLAIR helped in identifying the lesions. One of these patients underwent surgery, and histo-pathology revealed a cortical dysplasia. In one patient, lesion characterization was improved, while in the remaining patients the extent of the FCD was more clearly demonstrated in the 3D FLAIR and PD images. Statistical analysis of images for cortical thickness, cortical signal intensity, adjacent white matter abnormalities, and gray-white matter junction showed significant statistical difference in the ability of 3D FLAIR to assess these aspects over conventional images. PD images were also found superior to the routine epilepsy protocol in assessment of cortical signal, adjacent white matter, and gray-white matter junction. Conclusion: Specialized MRI sequences and techniques should be performed whenever there is a high suspicion of cortical dysplasia, especially when they remain occult on conventional MR protocols. These techniques
Energy Technology Data Exchange (ETDEWEB)
Morimoto, Emiko; Kanagaki, Mitsunori; Okada, Tomohisa; Yamamoto, Akira; Togashi, Kaori [Kyoto University Graduate School of Medicine, Department of Diagnostic Imaging and Nuclear Medicine, Kyoto (Japan); Mori, Nobuyuki [Tenri Hospital, Department of Radiology, Tenri, Nara (Japan); Matsumoto, Riki; Ikeda, Akio; Takahashi, Ryosuke [Kyoto University Graduate School of Medicine, Department of Neurology, Kyoto (Japan); Mikuni, Nobuhiro [Sapporo Medical University, Department of Neurosurgery, Sapporo, Hokkaido (Japan); Kunieda, Takeharu; Miyamoto, Susumu [Kyoto University Graduate School of Medicine, Department of Neurosurgery, Kyoto (Japan); Paul, Dominik [Siemens AG Healthcare Sector, Erlangen (Germany)
2013-01-15
To investigate the diagnostic capability of anterior temporal lobe white matter abnormal signal (ATLAS) for determining seizure focus laterality in temporal lobe epilepsy (TLE) by comparing different MR sequences. This prospective study was approved by the institutional review board and written informed consent was obtained. Three 3D sequences (double inversion recovery (DIR), fluid-attenuated inversion recovery (FLAIR) and T2-weighted imaging (T2WI)) and two 2D sequences (FLAIR and T2WI) were acquired at 3 T. Signal changes in the anterior temporal white matter of 21 normal volunteers were evaluated. ATLAS laterality was evaluated in 21 TLE patients. Agreement of independent evaluations by two neuroradiologists was assessed using {kappa} statistics. Differences in concordance between ATLAS laterality and clinically defined seizure focus laterality were analysed using McNemar's test with multiple comparisons. Pre-amygdala high signals (PAHS) were detected in all volunteers only on 3D-DIR. Inter-evaluator agreement was moderate to almost perfect for each sequence. Correct diagnosis of seizure laterality was significantly more frequent on 3D-DIR than on any other sequences (P {<=} 0.031 for each evaluator). The most sensitive sequence for detecting ATLAS laterality was 3D-DIR. ATLAS laterality on 3D-DIR can be a good indicator for determining seizure focus localization in TLE. (orig.)
International Nuclear Information System (INIS)
Morimoto, Emiko; Kanagaki, Mitsunori; Okada, Tomohisa; Yamamoto, Akira; Togashi, Kaori; Mori, Nobuyuki; Matsumoto, Riki; Ikeda, Akio; Takahashi, Ryosuke; Mikuni, Nobuhiro; Kunieda, Takeharu; Miyamoto, Susumu; Paul, Dominik
2013-01-01
To investigate the diagnostic capability of anterior temporal lobe white matter abnormal signal (ATLAS) for determining seizure focus laterality in temporal lobe epilepsy (TLE) by comparing different MR sequences. This prospective study was approved by the institutional review board and written informed consent was obtained. Three 3D sequences (double inversion recovery (DIR), fluid-attenuated inversion recovery (FLAIR) and T2-weighted imaging (T2WI)) and two 2D sequences (FLAIR and T2WI) were acquired at 3 T. Signal changes in the anterior temporal white matter of 21 normal volunteers were evaluated. ATLAS laterality was evaluated in 21 TLE patients. Agreement of independent evaluations by two neuroradiologists was assessed using κ statistics. Differences in concordance between ATLAS laterality and clinically defined seizure focus laterality were analysed using McNemar's test with multiple comparisons. Pre-amygdala high signals (PAHS) were detected in all volunteers only on 3D-DIR. Inter-evaluator agreement was moderate to almost perfect for each sequence. Correct diagnosis of seizure laterality was significantly more frequent on 3D-DIR than on any other sequences (P ≤ 0.031 for each evaluator). The most sensitive sequence for detecting ATLAS laterality was 3D-DIR. ATLAS laterality on 3D-DIR can be a good indicator for determining seizure focus localization in TLE. (orig.)
Fahed, Robert; Lecler, Augustin; Sabben, Candice; Khoury, Naim; Ducroux, Célina; Chalumeau, Vanessa; Botta, Daniele; Kalsoum, Erwah; Boisseau, William; Duron, Loïc; Cabral, Dominique; Koskas, Patricia; Benaïssa, Azzedine; Koulakian, Hasmik; Obadia, Michael; Maïer, Benjamin; Weisenburger-Lile, David; Lapergue, Bertrand; Wang, Adrien; Redjem, Hocine; Ciccio, Gabriele; Smajda, Stanislas; Desilles, Jean-Philippe; Mazighi, Mikaël; Ben Maacha, Malek; Akkari, Inès; Zuber, Kevin; Blanc, Raphaël; Raymond, Jean; Piotin, Michel
2018-01-01
We aimed to study the intrarater and interrater agreement of clinicians attributing DWI-ASPECTS (Diffusion-Weighted Imaging-Alberta Stroke Program Early Computed Tomography Scores) and DWI-FLAIR (Diffusion-Weighted Imaging-Fluid Attenuated Inversion Recovery) mismatch in patients with acute ischemic stroke referred for mechanical thrombectomy. Eighteen raters independently scored anonymized magnetic resonance imaging scans of 30 participants from a multicentre thrombectomy trial, in 2 different reading sessions. Agreement was measured using Fleiss κ and Cohen κ statistics. Interrater agreement for DWI-ASPECTS was slight (κ=0.17 [0.14-0.21]). Four raters (22.2%) had a substantial (or higher) intrarater agreement. Dichotomization of the DWI-ASPECTS (0-5 versus 6-10 or 0-6 versus 7-10) increased the interrater agreement to a substantial level (κ=0.62 [0.48-0.75] and 0.68 [0.55-0.79], respectively) and more raters reached a substantial (or higher) intrarater agreement (17/18 raters [94.4%]). Interrater agreement for DWI-FLAIR mismatch was moderate (κ=0.43 [0.33-0.57]); 11 raters (61.1%) reached a substantial (or higher) intrarater agreement. Agreement between clinicians assessing DWI-ASPECTS and DWI-FLAIR mismatch may not be sufficient to make repeatable clinical decisions in mechanical thrombectomy. The dichotomization of the DWI-ASPECTS (0-5 versus 0-6 or 0-6 versus 7-10) improved interrater and intrarater agreement, however, its relevance for patients selection for mechanical thrombectomy needs to be validated in a randomized trial. © 2017 American Heart Association, Inc.
Varella, Pedro Paulo Vasconcellos; Santiago, Joselita Ferreira Carvalho; Carrete, Henrique; Higa, Elisa Mieko Suemitsu; Yacubian, Elza Márcia Targas; Centeno, Ricardo Silva; Caboclo, Luís Otávio Sales Ferreira; Castro Neto, Eduardo Ferreira de; Canzian, Mauro; Amado, Débora; Cavalheiro, Esper Abrão; Naffah-Mazzacoratti, Maria da Graça
2011-02-01
We investigated a relationship between the FLAIR signal found in mesial temporal sclerosis (MTS) and inflammation. Twenty nine patients were selected through clinical and MRI analysis and submitted to cortico-amygdalo-hippocampectomy to seizure control. Glutamate, TNFα, IL1, nitric oxide (NO) levels and immunostaining against IL1β and CD45 was performed. Control tissues (n=10) were obtained after autopsy of patients without neurological disorders. The glutamate was decreased in the temporal lobe epilepsy (TLE) -MTS group (p<0.001), suggesting increased release of this neurotransmitter. The IL1β and TNFα were increased in the hippocampus (p<0.05) demonstrating an active inflammatory process. A positive linear correlation between FLAIR signal and NO and IL1β levels and a negative linear correlation between FLAIR signal and glutamate concentration was found. Lymphocytes infiltrates were present in hippocampi of TLE patients. These data showed an association between hippocampal signal alteration and increased inflammatory markers in TLE-MTS.
Directory of Open Access Journals (Sweden)
Pedro Paulo Vasconcellos Varella
2011-02-01
Full Text Available We investigated a relationship between the FLAIR signal found in mesial temporal sclerosis (MTS and inflammation. Twenty nine patients were selected through clinical and MRI analysis and submitted to cortico-amygdalo-hippocampectomy to seizure control. Glutamate, TNFα, IL1, nitric oxide (NO levels and immunostaining against IL1β and CD45 was performed. Control tissues (n=10 were obtained after autopsy of patients without neurological disorders. The glutamate was decreased in the temporal lobe epilepsy (TLE -MTS group (p<0.001, suggesting increased release of this neurotransmitter. The IL1β and TNFα were increased in the hippocampus (p<0.05 demonstrating an active inflammatory process. A positive linear correlation between FLAIR signal and NO and IL1β levels and a negative linear correlation between FLAIR signal and glutamate concentration was found. Lymphocytes infiltrates were present in hippocampi of TLE patients. These data showed an association between hippocampal signal alteration and increased inflammatory markers in TLE-MTS.
Energy Technology Data Exchange (ETDEWEB)
Carrete Junior, Henrique; Abdala, Nitamar; Szjenfeld, Jacob; Nogueira, Roberto Gomes [Universidade Federal de Sao Paulo (UNIFESP-EPM), Sao Paulo, SP (Brazil). Dept. de Diagnostico por Imagem; Lin, Katia; Caboclo, Luis Otavio; Centeno, Ricardo Silva; Sakamoto, Americo Ceiki; Yacubian, Elza Marcia Targas [Universidade Federal de Sao Paulo (UNIFESP-EPM), Sao Paulo, SP (Brazil). Dept. de Neurologia e Neurocirurgia
2007-09-15
Objective: To determine the frequency and regional involvement of temporal pole signal abnormality (TPA) in patients with hippocampal sclerosis (HS) using fluid-attenuated inversion-recovery (FLAIR) MR imaging, and to correlate this feature with history. Method: Coronal FLAIR images of the temporal pole were assessed in 120 patients with HS and in 30 normal subjects, to evaluate gray-white matter demarcation. Results: Ninety (75%) of 120 patients had associated TPA. The HS side made difference regarding the presence of TPA, with a left side prevalence (p=0.04, {chi}{sup 2} test). The anteromedial zone of temporal pole was affected in 27 (30%) out of 90 patients. In 63 (70%) patients the lateral zone were also affected. Patients with TPA were younger at seizure onset (p=0.018), but without association with duration of epilepsy. Conclusion: Our FLAIR study show temporal pole signal abnormality in 3/4 of patients with HS, mainly seen on the anteromedial region, with a larger prevalence when the left hippocampus was involved. (author)
Energy Technology Data Exchange (ETDEWEB)
Curati, Walter L.; Oatridge, Angela; Herlihy, Amy H.; Hajnal, Joseph V.; Puri, Basant K.; Bydder, Graeme M
2001-05-01
AIM: The aim of this study was to compare the performance of three fluid attenuated inversion recovery (FLAIR) pulse sequences for control of cerebrospinal fluid (CSF) and blood flow artifacts in imaging of the brain. The first of these sequences had an initial sinc inversion pulse which was followed by conventional k-space mapping. The second had an initial sinc inversion pulse followed by k-space re-ordered by inversion time at each slice position (KRISP) and the third had an adiabatic initial inversion pulse followed by KRISP. MATERIALS AND METHODS: Ten patients with established disease were studied with all three pulse sequences. Seven were also studied with the adiabatic KRISP sequence after contrast enhancement. Their images were evaluated for patient motion artifact, CSF and blood flow artifact as well as conspicuity of the cortex, meninges, ventricular system, brainstem and cerebellum. The conspicuity of lesions and the degree of enhancement were also evaluated. RESULTS: Both the sinc and adiabatic KRISP FLAIR sequences showed better control of CSF and blood flow artifacts than the conventional FLAIR sequence. In addition the adiabatic KRISP FLAIR sequence showed better control of CSF artifact at the inferior aspect of the posterior fossa. The lesion conspicuity was similar for each of the FLAIR sequences as was the degree of contrast enhancement to that shown with a T{sub 1}weighted spin echo sequence. CONCLUSION: The KRISP FLAIR sequence controls high signal artifacts from CSF flow and blood flow and the adiabatic pulse controls high signal artifacts due to inadequate inversion of the CSF magnetization at the periphery of the head transmitter coil. The KRISP FLAIR sequence also improves cortical and meningeal definition as a result of an edge enhancement effect. The effects are synergistic and can be usefully combined in a single pulse sequence. Curati, W.L. et al. (2001)
MRI of head injury using FLAIR
Energy Technology Data Exchange (ETDEWEB)
Ashikaga, R. [Dept. of Radiology, Kinki Univ. School of Medicine, Osaka (Japan); Araki, Y. [Dept. of Radiology, Kinki Univ. School of Medicine, Osaka (Japan); Ishida, O. [Dept. of Radiology, Kinki Univ. School of Medicine, Osaka (Japan)
1997-04-01
We studied the utility of fluid-attenuated inversion-recovery (FLAIR) MRI in the investigation of head injury. We examined 56 patients with head injuries with T2-weighted spin-echo (SE) and FLAIR sequences. In all cases, the sensitivity of FLAIR images to equal or superior to that of conventional SE images to the traumatic lesions. In 9 cases, central diffuse axonal injury of the fornix and corpus callosum could be seen only on sagittal FLAIR images. (orig.). With 4 figs., 1 tab.
MRI of head injury using FLAIR
International Nuclear Information System (INIS)
Ashikaga, R.; Araki, Y.; Ishida, O.
1997-01-01
We studied the utility of fluid-attenuated inversion-recovery (FLAIR) MRI in the investigation of head injury. We examined 56 patients with head injuries with T2-weighted spin-echo (SE) and FLAIR sequences. In all cases, the sensitivity of FLAIR images to equal or superior to that of conventional SE images to the traumatic lesions. In 9 cases, central diffuse axonal injury of the fornix and corpus callosum could be seen only on sagittal FLAIR images. (orig.). With 4 figs., 1 tab
Directory of Open Access Journals (Sweden)
Henrique Carrete Junior
2007-09-01
Full Text Available OBJECTIVE: To determine the frequency and regional involvement of temporal pole signal abnormality (TPA in patients with hippocampal sclerosis (HS using fluid-attenuated inversion-recovery (FLAIR MR imaging, and to correlate this feature with history. METHOD: Coronal FLAIR images of the temporal pole were assessed in 120 patients with HS and in 30 normal subjects, to evaluate gray-white matter demarcation. RESULTS: Ninety (75% of 120 patients had associated TPA. The HS side made difference regarding the presence of TPA, with a left side prevalence (p=0.04, chi2 test. The anteromedial zone of temporal pole was affected in 27 (30% out of 90 patients. In 63 (70% patients the lateral zone were also affected. Patients with TPA were younger at seizure onset (p=0.018, but without association with duration of epilepsy. CONCLUSION: Our FLAIR study show temporal pole signal abnormality in 3/4 of patients with HS, mainly seen on the anteromedial region, with a larger prevalence when the left hippocampus was involved.OBJETIVO: Determinar a freqüência e o envolvimento regional da anormalidade de sinal do pólo temporal (APT em pacientes com esclerose hipocampal (EH utilizando seqüência inversão recuperação com supressão da água (FLAIR por RM, e correlacioná-la com a história. MÉTODO: Foram analisadas as imagens coronais FLAIR dos pólos temporais de 120 pacientes com EH e de 30 indivíduos normais, para avaliar a demarcação entre substâncias branca e cinzenta. RESULTADOS: Noventa (75% dos 120 pacientes tinham APT associada. Houve prevalência do lado esquerdo (p=0.04, chi2 teste na relação entre APT e o lado da EH. A zona ântero-medial estava acometida em 27 (30% destes pacientes. Em 63 (70% pacientes também a zona lateral estava acometida. Pacientes com APT apresentaram início da epilepsia quando mais jovens (p=0.018, porém sem associação com a sua duração. CONCLUSÃO: A seqüência FLAIR mostra haver ATP em 3/4 dos pacientes com EH
FLAIR images of brain diseases
International Nuclear Information System (INIS)
Segawa, Fuminori; Kinoshita, Masao; Kishibayashi, Jun; Kamada, Kazuhiko; Sunohara, Nobuhiko.
1994-01-01
The present study was designed to assess the usefulness of fluid-attenuated inversion recovery (FLAIR) images in diagnosing brain diseases. The subjects were 20 patients with multiple cerebral infarction, multiple sclerosis, temporal epilepsy, or brain trauma, and 20 other healthy adults. FLAIR images, with a long repetitive time of 6000 msec and a long inversion time of 1400-1600 msec, showed low signal intensity in the cerebrospinal fluid in the lateral ventricles and the cerebral sulci, and high signal intensity in brain tissues. Signal intensity on FLAIR images correlated well with T2 relaxation times under 100 msec. For multiple sclerosis and cerebral infarction, cystic lesions, which were shown on T2-weighted images with long relaxation times over 100 msec, appeared as low-signal areas; and the lesions surrounding the cystic lesions appeared as high-signal areas. For temporal lobe epilepsy, the hippocampus was visualized as a high-signal area. Hippocampal lesions were demonstrated better with FLAIR images than with conventional T2-weighted and proton-density images. In a patient with cerebral trauma, FLAIR images revealed the lobulated structure with the residual cortex shown as a high signal area. The lesions surrounding the cystic change were imaged as high signal areas. These structural changes were demonstrated better with FLAIR images than with conventional T2-weighted sequences. FLAIR images were useful in detecting white matter lesions surrounding the lateral ventricles and cortical and subcortical lesions near the brain surface, which were unclear on conventional T2-weighted and proton-density images. (N.K.)
Morphological features of MS lesions on FLAIR* at 7 T and their relation to patient characteristics
Kilsdonk, I.D.; Lopez Soriano, A.; Kuijer, J.P.A.; de Graaf, W.L.; Castelijns, J.A.; Polman, C.H.; Luijten, P.R.; Geurts, J.J.G.; Barkhof, F.; Wattjes, M.P.
2014-01-01
Recently, a new MRI technique was developed at 3 Tesla (T), called fluid attenuated inversion recovery (FLAIR). In this study, we implemented FLAIR in an existing MS cohort at 7 T, to investigate whether we could corroborate results of previous 7 T studies that introduced specific MS lesion
Fast fluid-attenuated inversion-recovery imaging: first experience with a 3D version in epilepsy
International Nuclear Information System (INIS)
Wieshmann, U.C.; Symms, M.R.; Bartlett, P.A.; Shorvon, S.D.; Barker, G.J.; Stevens, J.M.
1998-01-01
We developed a 3D version of fast fluid-attenuated inversion-recovery imaging (FLAIR) which provides images with a slice thickness of 1.5 mm. We present our initial experience with 3D fast FLAIR in patients with epilepsy. We compared 3D fast FLAIR (slice thickness 1.5 mm), 2D fast FLAIR (slice thickness 5 mm) and a 3D spoiled GRASS (IRSPGR) sequence (slice thickness 1.5 mm) in 10 patients with lesional epilepsy (head injury 1, hippocampal sclerosis 2, low-grade glioma 2, dysembryoplastic neuroepithelial tumour 2, polymicrogyria 1, perinatal infarct 1 and presumed thrombosed aneurysm 1). Both 2D and 3D fast FLAIR sequences yielded higher conspicuity for lesions than the T1-weighted IRSPGR sequence, except in the patient with polymicrogyria. The extent of the lesion, in particular that of low-grade tumours, was best assessed on 3D fast FLAIR images. 3D fast FLAIR may be a useful additional tool especially for imaging low-grade tumours. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Sie, L.T.L.; Knaap, M.S. van der [Vrije Univ. Hospital, Amsterdam (Netherlands). Dept. of Neurology; Barkhof, F.; Valk, J. [Amsterdam Univ. (Netherlands). Dept. of Diagnostic Radiology, Pathology and Gastroenterology; Lafeber, H.N. [Univ. Hospital ' Vrije Universiteit' , Amsterdam (Netherlands). Dept. of Neonatology
2000-10-01
The aim of our study was to assess the usefulness of fluid-attenuated inversion recovery (FLAIR) sequences in comparison with conventional spin-echo and inversion MR imaging in neonates for evaluation of myelination and for detection of hypoxic-ischemic brain injury. We reviewed early MR scans of 18 neonates with suspected hypoxic-ischemic brain damage. Myelination could be evaluated with confidence using conventional MR imaging in all but 2 infants; however, the presence of myelin was very difficult to assess on FLAIR images. Overall, 53 lesions or groups of lesions were identified. The FLAIR technique was more sensitive in 11 of the lesions; especially (pre)cystic lesions could be identified much better and more cysts were found. Conventional MR imaging failed to identify 2 of the lesions and was more sensitive in 14 of the lesions; especially punctate hemorrhages and lesions in basal ganglia or thalami could be better determined. The FLAIR technique missed 3 of these lesions. In the remaining 28 lesions conventional MR and FLAIR images were equally diagnostic. The FLAIR technique and conventional MR imaging are complementary in detecting early sequelae of hypoxic-ischemic brain injury in neonates. The FLAIR technique is not suitable for assessing myelination of the neonatal brain; therefore, FLAIR cannot replace conventional MR imaging. (orig.)
Clinical utility of MR FLAIR imaging for head injuries
International Nuclear Information System (INIS)
Ashikaga, Ryuichiro
1996-01-01
To study the utility of fluid attenuated inversion recovery (FLAIR) MR images in the evaluation of traumatic head injury, 56 patients with traumatic head injuries were examined with long TR/TE spin-echo (SE) sequences and FLAIR sequences. In 40 of them, long TR/short TE images were added to those sequences. Careful readings of MR images were done by two well-trained neuroradiologists. The chi-square test was used for statistical evaluation of our results. The relative sensitivities of FLAIR images were significantly better than those of long TR/TE, long TR/short TE images for the detection of diffuse axonal injury (p<0.01), cortical contusion (p<0.01), and subdural hematoma (p<0.01 for long TR/TE, p<0.05 for long TR/short TE). The number of cases of epidural hematoma and brainstem injury was too small for statistical significance to be determined. In 9 patients with corpus callosum injuries. FLAIR images demonstrated the lesions as abnormally high signal intensity in the septum pellucidum and fornix. Only sagittal FLAIR images could definitely discriminate the traumatic lesions of the fornix from the surrounding CSF. In addition, FLAIR images could easily discriminate DAI of the corpus callosum from CSF of the cavum velli interpositi. MR FLAIR images were found to be useful for detecting traumatic head injuries. (author)
Clinical utility of MR FLAIR imaging for head injuries
Energy Technology Data Exchange (ETDEWEB)
Ashikaga, Ryuichiro [Kinki Univ., Osaka-Sayama, Osaka (Japan). School of Medicine
1996-12-01
To study the utility of fluid attenuated inversion recovery (FLAIR) MR images in the evaluation of traumatic head injury, 56 patients with traumatic head injuries were examined with long TR/TE spin-echo (SE) sequences and FLAIR sequences. In 40 of them, long TR/short TE images were added to those sequences. Careful readings of MR images were done by two well-trained neuroradiologists. The chi-square test was used for statistical evaluation of our results. The relative sensitivities of FLAIR images were significantly better than those of long TR/TE, long TR/short TE images for the detection of diffuse axonal injury (p<0.01), cortical contusion (p<0.01), and subdural hematoma (p<0.01 for long TR/TE, p<0.05 for long TR/short TE). The number of cases of epidural hematoma and brainstem injury was too small for statistical significance to be determined. In 9 patients with corpus callosum injuries. FLAIR images demonstrated the lesions as abnormally high signal intensity in the septum pellucidum and fornix. Only sagittal FLAIR images could definitely discriminate the traumatic lesions of the fornix from the surrounding CSF. In addition, FLAIR images could easily discriminate DAI of the corpus callosum from CSF of the cavum velli interpositi. MR FLAIR images were found to be useful for detecting traumatic head injuries. (author)
Energy Technology Data Exchange (ETDEWEB)
Hwang, Asiry; Seo, Jeong-Jin; Jeong, Gwang Woo; Chung, Tae Woong; Jeong, Yong Yeon; Kang, Heoung Keun; Kook, Hoon; Woo, Young Jong; Hwang, Tai Joo [Chonnam Univ. Medical School, Seoul (Korea, Republic of)
1999-03-01
The purpose of this study was to evaluate the usefulness of FLAIR(Fluid Attenuated Inversion Recovery) MR imaging in childhood adrenoleukodystrophy by comparing with those of T2-weighted FSE imaging, and to correlate MRI findings with clinical manifestations. Axial FLAIR images(TR/TE/TI=10004/123/2200) and T2-weighted FSE images(TR/TE=4000/104) of brain in six male patients(age range : 6-17 years, mean age : 10.2 years) with biochemically confirmed adrenoleukodystrophy were compared visually by two radiologists for detection, conspicuity, and the extent of lesion. Quantitatively, we compared lesion/CSF contrast, lesion/CSF contrast to noise ratio(CNR), lesion/white matter(WM) contrast, and lesion/WM CNR between FLAIR and T2 weighted image. We correlated MR findings with clinical manifestations of neurologic symptoms and evaluated whether MRI could detect white matter lesions in neurologically asymptomatic patients. Visual detection of lesions was better with FLAIR images in 2 of the 6 cases and it was equal in the remainders. Visual conspicuity and detection of the extent of lesion were superior on FLAIR images than T2-weighted images in all 6 cases. In the quantitative assessment of lesions, FLAIR was superior to T2-weighted image for lesion/CSF contrast and lesion/CSF CNR, but was inferior to T2 weighted image for lesion/WM contrast and lesion/WM CNR. In one case, FLAIR images distinguished the portion of encephalomalacic change from lesions. MR findings of adrenoleukodystrophy were correlated with clinical manifestations in symptomatic 4 cases, and also detected white matter lesions in asymptomatic 2 cases. MR imaging with FLAIR sequence provided images that were equal or superior to T2-weighted images in the evaluation of childhood adrenoleukodystrophy. MRI findings were well correlated with clinical manifestations and could detect white matter lesions in neurologically asymptomatic adrenoleukodystrophy patients.
Improved differentiation between MS and vascular brain lesions using FLAIR* at 7 Tesla
Energy Technology Data Exchange (ETDEWEB)
Kilsdonk, Iris D.; Wattjes, Mike P.; Lopez-Soriano, Alexandra; Jong, Marcus C. de; Graaf, Wolter L. de; Conijn, Mandy M.A.; Barkhof, Frederik [VU University Medical Center, Department of Radiology, De Boelelaan 1118, HZ, Amsterdam (Netherlands); Kuijer, Joost P.A. [VU University Medical Center, Department of Physics and Medical Technology, Amsterdam (Netherlands); Polman, Chris H. [VU University Medical Center, Department of Neurology, Amsterdam (Netherlands); Luijten, Peter R. [University Medical Center, Department of Radiology, Utrecht (Netherlands); Geurts, Jeroen J.G. [VU University, Department of Anatomy and Neurosciences, Amsterdam (Netherlands); Geerlings, Mirjam I. [University Medical Center, Julius Center for Health Sciences and Primary Care, Utrecht (Netherlands)
2014-04-15
To investigate whether a new magnetic resonance image (MRI) technique called T2*-weighted fluid attenuation inversion recovery (FLAIR*) can differentiate between multiple sclerosis (MS) and vascular brain lesions, at 7 Tesla (T). We examined 16 MS patients and 16 age-matched patients with (risk factors for) vascular disease. 3D-FLAIR and T2*-weighted images were combined into FLAIR* images. Lesion type and intensity, perivascular orientation and presence of a hypointense rim were analysed. In total, 433 cerebral lesions were detected in MS patients versus 86 lesions in vascular patients. Lesions in MS patients were significantly more often orientated in a perivascular manner: 74 % vs. 47 % (P < 0.001). Ten MS lesions (2.3 %) were surrounded by a hypointense rim on FLAIR*, and 24 MS lesions (5.5 %) were hypointense on T2*. No lesions in vascular patients showed any rim or hypointensity. Specificity of differentiating MS from vascular lesions on 7-T FLAIR* increased when the presence of a central vessel was taken into account (from 63 % to 88 %), most obviously for deep white matter lesions (from 69 % to 94 %). High sensitivity remained (81 %). 7-T FLAIR* improves differentiation between MS and vascular lesions based on lesion location, perivascular orientation and presence of hypointense (rims around) lesions. circle A new MRI technique T2*-weighted fluid attenuation inversion recovery (FLAIR*) was investigated. circle FLAIR* at 7-T MRI combines FLAIR and T2* images into a single image. circle FLAIR* at 7 T does not require enhancement with contrast agents. (orig.)
Clinical usefulness of FLAIR MR sequence in the diagnosis of cerebral disease
Energy Technology Data Exchange (ETDEWEB)
Lee, Sang Hyun; Chang, Kee Hyun; Park, Hong Suk; Sim, Jung Suk; Cho, Seong Whi; Yu, In Kyu; Han, Moon Hee [Seoul National Univ. College of Medicine, Seoul (Korea, Republic of)
1997-07-01
To evaluate the clinical usefulness and limitation of FLAIR(fluid attenuated inversion recovery) MR sequence in various intracranial pathologic conditions. In prospective fashion, we used a 1.0T MR unit to obtain FLAIR sequence MR images, together with T1-weighted (T1WI), proton-density weighted (PDWI), and T2-weighted spin echo images (T2WI) in 24 patients with various intracranial diseases. Forty-two lesions in 24 patients were classified into three categories : nonhemorrhagic noncavitary lesions (n=20), hemorrhagic lesions (n=10), and cavitary lesions (n=12). Hemorrhagic lesion was divided into two types; type 1 showed high signal intensity on both T1WI and T2WI and type 2 showed marked low signal intensity on T2WI such as hemosiderin. Cavitary lesion was defined as one with signal intensity which paralleled CSF on all pulse sequences. Visually, we compared the lesion conspicuity on FLAIR with that on T2WI. Quantitatively, we also compared lesion/white matter (WM) contrast, lesion/WM contrast to noise ratio(CNR), lesion/CSF contrast, and lesion/CSF CNR on FLAIR with those on T2WI. For visual conspicuity of nonhemorrhagic noncavitary lesions and type 1 hemorrhagic lesions, FLAIR was superior to PDWI and T2WI, but for type 2 hemorrhangic lesions, PDWI and T2WI were superior to FLAIR. For cavitary lesions, there was no significant difference between T2WI and FLAIR. In the quantitative assessment of nonhemorrhagic noncavitary lesions, FLAIR was superior to PDWI for lesion/CSF cnotrast, and CNR, and lesion/WM contrast, but for lesion/WM CNR FLAIR was inferior to PDWI. For lesion/CSF contrast in cavitary lesions, FLAIR was superior to PDWI. There was no significant difference between PDWI and FLAIR for hemorrhagic lesions types 1 and 2. In assessing nonhemorrhagic noncavitary lesions, FLAIR was superior to T2WI for lesion/CSF contrast, but for lesion/WM CNR, FLAIR was inferior to T2WI. In cavitary lesions, T2WI was superior to FLAIR for lesion/WM contrast and CNR. In
Fast spine echo and fast fluid attenuated inversion recovery sequences in multiple sclerosis
International Nuclear Information System (INIS)
Paolillo, Andrea; Giugni, Elisabetta; Bozzao, Alessandro; Bastianello, Stefano
1997-01-01
Fast spin echo (FSE) and fast fluid attenuated inversion recovery (fast-FLAIR) sequences, were compared with conventional spin echo (CSE) in quantitating multiple sclerosis (MS) lesion burden. For each sequence, the total number and volume of MS lesions were calculated in 38 remitting multiple sclerosis patients using a semiautomated lesion detection program. Conventional spin echo, fast spin echo, and fast fluid attenuated inversion recovery image were reported on randomly and at different times by two expert observers. Interobserver differences, the time needed to quantitative multiple sclerosis lesions and lesion signal intensity (contrast-to-noise ratio and overall contrast) were considered. The lesions were classified by site into infratentorial, white matter and cortical/subcortical. A total of 2970 lesions with a volume of 961.7 cm 3 was calculated on conventional spin echo images. Fast spin echo images depicted fewer (16.6%; p < .005) and smaller (24.9%; p < .0001) lesions and the differences were statistically significant. Despite an overall nonsignificant reduction for fast-FLAIR images (-5% and 4.8% for lesion number and volume, respectively), significantly lower values (lesion number: p < 0.1; volume: p < .04)were observed for infratentorial lesions, while significantly higher values were seen for cortical/subcortical lesions (lesion number: p < .01; volume: p < .02). A higher lesion/white matter contrast (p < .002), a significant time saving for lesion burden quantitation (p < .05) and very low interobserver variability were found in favor of fast-FLAIR. Our data suggest that, despite the limitations regarding infratentorial lesions, fast-FLAIR sequences are indicated in R studies because of their good identification of cortical/subcortical lesions, almost complete interobserver agreement, higher contrast-to-noise ratio and limited time needed for semiautomated quantitation
Hoy, Andrew R; Kecskemeti, Steven R; Alexander, Andrew L
2015-12-01
White matter tractography reconstructions using conventional diffusion tensor imaging (DTI) near cerebrospinal fluid (CSF) spaces are often adversely affected by CSF partial volume effects (PVEs). This study evaluates the ability of free water elimination (FWE) DTI methods to minimize the PVE of CSF for deterministic tractography applications. Ten healthy individuals were scanned with "traditional," FLAIR (fluid-attenuated inversion recovery), and FWE DTI scans. The fornix, corpus callosum, and cingulum bundles were reconstructed using deterministic tractography. The FWE DTI scan was performed twice to separately match total acquisition time (long FWE) and number of measurements (encoding directions, short FWE) to the FLAIR and "traditional" DTI scans. PVE resolution was determined based on reconstructed tract volume. All reconstructions underwent blinded review for anatomical correctness, symmetry, and completeness. Reconstructions of the fornix demonstrated that the FWE and FLAIR scans produce more complete, anatomically plausible reconstructions than "traditional" DTI. Additionally, the tract reconstructions using FWE-DTI were significantly larger than when FLAIR was used with DTI (P acquisitions did not significantly (P ≥ 0.31) differ from one another for any of the reconstructed tracts. The FWE diffusion model overcomes CSF PVE without the time, SNR, and volumetric coverage penalties inherent to FLAIR DTI. © 2015 Wiley Periodicals, Inc.
Payabvash, Seyedmehdi; Taleb, Shayandokht; Benson, John C; Rykken, Jeffrey B; Oswood, Mark C; McKinney, Alexander M; Hoffman, Benjamin
2017-07-01
The lack of fluid-attenuated inversion-recovery (FLAIR) hyperintensity in areas of diffusion-weighted imaging (DWI) high signal, or DWI-FLAIR mismatch, is a potential imaging biomarker for timing of stroke onset. We aimed to determine the effects of DWI infarct lesion volume on DWI-FLAIR mismatch and its accuracy for identification of strokes within intravenous (IV) the thrombolytic therapy window. Acute ischemic stroke patients with magnetic resonance imaging scan within 12 hours of witnessed stroke were included. Two neuroradiologists independently reviewed DWI and FLAIR sequences for DWI-FLAIR mismatch in areas of restricted diffusion compared to the contralateral normal side. DWI-FLAIR mismatch was identified in 21/82 (26%) patients. Infarct lesions with DWI-FLAIR mismatch were scanned earlier (3.8 ± .3 vs. 7.5 ± .3 hours from onset, P mismatch. Multivariate regression analysis showed a significant interaction between lesion volume and time-from-onset in relationship with the presence of DWI-FLAIR mismatch (P = .045). The presence of DWI-FLAIR mismatch had 56% sensitivity, 83% specificity, 48% positive predictive value (PPV), and 87% negative predictive value (NPV) for identification of infarction within 4.5 hours of symptom onset; while for infarct lesions >15 mL, the DWI-FLAIR mismatch had 100% specificity and PPV for acute infarcts within 4.5 hours of onset. The effects of stroke onset-to-scan time gap on DWI-FLAIR mismatch are not the same for different DWI lesion volumes. At DWI lesion volumes >15 mL, the DWI-FLAIR mismatch is highly specific for acute infarcts within IV thrombolytic therapy time, and can identify wake-up stroke patients eligible for treatment. Copyright © 2016 by the American Society of Neuroimaging.
An Inversion Recovery NMR Kinetics Experiment
Williams, Travis J.; Kershaw, Allan D.; Li, Vincent; Wu, Xinping
2011-01-01
A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this article will enable instructors to use inversion recovery as a laboratory activity in applied NMR classes and provide research students with a conveni...
Inverse regression for ridge recovery II: Numerics
Glaws, Andrew; Constantine, Paul G.; Cook, R. Dennis
2018-01-01
We investigate the application of sufficient dimension reduction (SDR) to a noiseless data set derived from a deterministic function of several variables. In this context, SDR provides a framework for ridge recovery. In this second part, we explore the numerical subtleties associated with using two inverse regression methods---sliced inverse regression (SIR) and sliced average variance estimation (SAVE)---for ridge recovery. This includes a detailed numerical analysis of the eigenvalues of th...
Contrast-enhanced flair imaging in the evaluation of infectious leptomeningeal diseases
International Nuclear Information System (INIS)
Parmar, Hemant; Sitoh, Y.-Y.; Anand, Pooja; Chua, Violet; Hui, Francis
2006-01-01
Purpose: The purpose of our study was to compare contrast-enhanced fluid-attenuated inversion recovery (FLAIR) images with contrast-enhanced T1 weighted images for infectious leptomeningitis. Materials and methods: We studied twenty-four patients with a clinical suspicion of infectious meningitis with unenhanced FLAIR, contrast-enhanced T1 weighted and contrast-enhanced FLAIR MR sequences. Twelve patients had cytologic and biochemical diagnosis of meningitis on cerebrospinal fluid (CSF) examination obtained 48 h before or after the MR study. Sequences were considered positive if abnormal signal was seen in the subarachnoid space (cistern or sulci) or along pial surface. Results: Twenty-seven examinations in 24 patients were performed. Of the 12 patients (thirteen studies) in whom cytology was positive, unenhanced FLAIR images were positive in six cases (sensitivity 46%), contrast-enhanced FLAIR images were positive in 11 (sensitivity 85%), and contrast-enhanced T1 weighted MR images were positive in 11 patients (sensitivity 85%). Of the 12 patients (14 studies) in whom cerebrospinal fluid study was negative, unenhanced FLAIR images were negative in 13, contrast-enhanced FLAIR images were negative in 11, and contrast-enhanced T1 weighted MR images were negative in eight. Thus, the specificity of unenhanced FLAIR, contrast-enhanced FLAIR and contrast-enhanced T1 weighted images was 93, 79 and 57%, respectively. Conclusion: Our results suggest that post-contrast FLAIR images have similar sensitivity but a higher specificity compared to contrast-enhanced T1 weighted images for detection of leptomeningeal enhancement. It can be a useful adjunct to post-contrast T1 weighted images in evaluation of infectious leptomeningitis
Contrast-enhanced flair imaging in the evaluation of infectious leptomeningeal diseases
Energy Technology Data Exchange (ETDEWEB)
Parmar, Hemant [Department of Neuroradiology, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433 (Singapore) and Department of Diagnostic Imaging, Hospital for Sick Children, Toronto (Canada)]. E-mail: parurad@hotmail.com; Sitoh, Y.-Y. [Department of Neuroradiology, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433 (Singapore); Anand, Pooja [Department of Neurology, National Neuroscience Institute, 11 Jalan Tan Tock Seng (Singapore); Chua, Violet [Department of Neuroradiology, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433 (Singapore); Hui, Francis [Department of Neuroradiology, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433 (Singapore)
2006-04-15
Purpose: The purpose of our study was to compare contrast-enhanced fluid-attenuated inversion recovery (FLAIR) images with contrast-enhanced T1 weighted images for infectious leptomeningitis. Materials and methods: We studied twenty-four patients with a clinical suspicion of infectious meningitis with unenhanced FLAIR, contrast-enhanced T1 weighted and contrast-enhanced FLAIR MR sequences. Twelve patients had cytologic and biochemical diagnosis of meningitis on cerebrospinal fluid (CSF) examination obtained 48 h before or after the MR study. Sequences were considered positive if abnormal signal was seen in the subarachnoid space (cistern or sulci) or along pial surface. Results: Twenty-seven examinations in 24 patients were performed. Of the 12 patients (thirteen studies) in whom cytology was positive, unenhanced FLAIR images were positive in six cases (sensitivity 46%), contrast-enhanced FLAIR images were positive in 11 (sensitivity 85%), and contrast-enhanced T1 weighted MR images were positive in 11 patients (sensitivity 85%). Of the 12 patients (14 studies) in whom cerebrospinal fluid study was negative, unenhanced FLAIR images were negative in 13, contrast-enhanced FLAIR images were negative in 11, and contrast-enhanced T1 weighted MR images were negative in eight. Thus, the specificity of unenhanced FLAIR, contrast-enhanced FLAIR and contrast-enhanced T1 weighted images was 93, 79 and 57%, respectively. Conclusion: Our results suggest that post-contrast FLAIR images have similar sensitivity but a higher specificity compared to contrast-enhanced T1 weighted images for detection of leptomeningeal enhancement. It can be a useful adjunct to post-contrast T1 weighted images in evaluation of infectious leptomeningitis.
Pre- and postcontrast FLAIR MR imaging in the diagnosis of intracranial meningeal pathology
International Nuclear Information System (INIS)
Tsuchiya, Kazuhiro; Katase, Shichiro; Yoshino, Ayako; Hachiya, Junichi
2000-01-01
Few reports address the use of fluid-attenuated inversion-recovery (FLAIR) images of the brain in the diagnosis of extraaxial lesions. Our purpose was to assess the value of FLAIR images, including postcontrast ones, in the diagnosis of intracranial meningeal diseases. We reviewed precontrast (n=24) and postcontrast (n=20) FLAIR images obtained from 25 patients with infectious meningitis (n=13), carcinomatous meningitis or dissemination of primary brain tumor (n=7), dural metastasis (n=3), and others (n=2) in comparison with fast spin-echo T2-weighted and postcontrast T1-weighted images. In lesion detectability, precontrast FLAIR images were significantly superior to fast spin-echo T2-weighted images but inferior to postcontrast T1-weighted images. There was no significant difference between postcontrast T1-weighted and FLAIR images. Precontrast FLAIR images can substitute for conventional fast spin-echo T2-weighted images. Postcontrast FLAIR images have diagnostic potential equivalent to conventional postcontrast T1-weighted images. (author)
Energy Technology Data Exchange (ETDEWEB)
Liao, Wen-Huei [School of Medicine, National Yang Ming University, Taipei, 11221, Taiwan (China); Department of Otolaryngology, Taipei Veterans General Hospital, Taipei, 11217, Taiwan (China); Wu, Hsiu-Mei [School of Medicine, National Yang Ming University, Taipei, 11221, Taiwan (China); Department of Radiology, Taipei Veterans General Hospital, Taipei, 11217, Taiwan (China); Wu, Hung-Yi [Department of Radiology, Taipei Veterans General Hospital, Taipei, 11217, Taiwan (China); Tu, Tzong-Yang; Shiao, An-Suey [School of Medicine, National Yang Ming University, Taipei, 11221, Taiwan (China); Department of Otolaryngology, Taipei Veterans General Hospital, Taipei, 11217, Taiwan (China); Castillo, Mauricio [Department of Radiology, University of North Carolina, Chapel Hill, NC, 27599-7510 (United States); Hung, Sheng-Che, E-mail: hsz829@gmail.com [School of Medicine, National Yang Ming University, Taipei, 11221, Taiwan (China); Department of Radiology, Taipei Veterans General Hospital, Taipei, 11217, Taiwan (China); Department of Biomedical Imaging and Radiological Sciences, National Yang Ming University, Taipei, 11221, Taiwan (China)
2016-12-15
Background and purpose: Three-dimensional fluid attenuation inversion recovery (3D FLAIR) may demonstrate high signal in the inner ears of patients with idiopathic sudden sensorineural hearing loss (ISSNHL), but the correlations of this finding with outcomes are still controversial. Here we compared 4 3D MRI sequences with the outcomes of patients with ISSNHL. Materials and methods: 77 adult patients with ISSNHL underwent MRI with pre contrast FLAIR, fast imaging employing steady-state acquisition images (FIESTA-C), post contrast T1WI and post contrast FLAIR. The extent and degree of high signal in both cochleas were evaluated in all patients, and asymmetry ratios between the affected ears and the normal ones were calculated. The relationships among MRI findings, including extent and asymmetry of abnormal cochlear high signals, degree of FLAIR enhancement, and clinical information, including age, vestibular symptoms, baseline hearing loss, and final hearing outcomes were analyzed. Results: 54 patients (28 men; age, 52.1 ± 15.5 years) were included in our study. Asymmetric cochlear signal intensities were more frequently observed in pre contrast and post contrast FLAIR (79.6% and 68.5%) than in FIESTA-C (61.1%) and T1WI (51.9%) (p < 0.001). Age, baseline hearing loss, extent of high signal and asymmetry ratios of pre contrast and post contrast FLAIR were all correlated with final hearing outcomes. In multivariate analysis, age and the extent of high signals were the most significant predictors of final hearing outcomes. Conclusion: 3D FLAIR provides a higher sensitivity in detecting the asymmetric cochlear signal abnormality. The more asymmetric FLAIR signals and presence of high signals beyond cochlea indicated a poorer prognosis.
Energy Technology Data Exchange (ETDEWEB)
Azad, Rajiv; Tayal, Mohit; Azad, Sheenam; Sharma, Garima; Srivastava, Rajendra Kumar [SGRR Institute of Medical and Health Sciences, Patel Nagar, Dehradun (India)
2017-11-15
To compare the contrast-enhanced fluid-attenuated inversion recovery (CE-FLAIR), the CE T1-weighted (CE-T1W) sequence with fat suppression (FS) and magnetization transfer (MT) for early detection and characterization of infectious meningitis. Fifty patients and 10 control subjects were evaluated with the CE-FLAIR and the CE-T1W sequences with FS and MT. Qualitative assessment was done by two observers for presence and grading of abnormal leptomeningeal enhancement. Quantitative assessment included computation of net meningeal enhancement, using single pixel signal intensity software. A newly devised FLAIR based scoring system, based on certain imaging features including ventricular dilatation, ependymal enhancement, infarcts and subdural effusions was used to indicate the etiology. Data were analysed using the Student's t test, Cohen's Kappa coefficient, Pearson's correlation coefficient, the intraclass correlation coefficient, one way analysis of variance, and Fisher's exact test with Bonferroni correction as the post hoc test. The CE-FLAIR sequence demonstrated a better sensitivity (100%), diagnostic accuracy (95%), and a stronger correlation with the cerebrospinal fluid, total leukocyte count (r = 0.75), protein (r = 0.77), adenosine deaminase (r = 0.81) and blood glucose (r = -0.6) values compared to the CE-T1W sequences. Qualitative grades and quantitative meningeal enhancement on the CE-FLAIR sequence were also significantly greater than those on the other sequences. The FLAIR based scoring system yielded a diagnostic accuracy of 91.6% and a sensitivity of 96%. A strong inverse Pearson's correlation (r = -0.95) was found between the assigned score and patient's Glasgow Coma Scale at the time of admission. The CE-FLAIR sequence is better suited for evaluating infectious meningitis and could be included as a part of the routine MR imaging protocol.
International Nuclear Information System (INIS)
Azad, Rajiv; Tayal, Mohit; Azad, Sheenam; Sharma, Garima; Srivastava, Rajendra Kumar
2017-01-01
To compare the contrast-enhanced fluid-attenuated inversion recovery (CE-FLAIR), the CE T1-weighted (CE-T1W) sequence with fat suppression (FS) and magnetization transfer (MT) for early detection and characterization of infectious meningitis. Fifty patients and 10 control subjects were evaluated with the CE-FLAIR and the CE-T1W sequences with FS and MT. Qualitative assessment was done by two observers for presence and grading of abnormal leptomeningeal enhancement. Quantitative assessment included computation of net meningeal enhancement, using single pixel signal intensity software. A newly devised FLAIR based scoring system, based on certain imaging features including ventricular dilatation, ependymal enhancement, infarcts and subdural effusions was used to indicate the etiology. Data were analysed using the Student's t test, Cohen's Kappa coefficient, Pearson's correlation coefficient, the intraclass correlation coefficient, one way analysis of variance, and Fisher's exact test with Bonferroni correction as the post hoc test. The CE-FLAIR sequence demonstrated a better sensitivity (100%), diagnostic accuracy (95%), and a stronger correlation with the cerebrospinal fluid, total leukocyte count (r = 0.75), protein (r = 0.77), adenosine deaminase (r = 0.81) and blood glucose (r = -0.6) values compared to the CE-T1W sequences. Qualitative grades and quantitative meningeal enhancement on the CE-FLAIR sequence were also significantly greater than those on the other sequences. The FLAIR based scoring system yielded a diagnostic accuracy of 91.6% and a sensitivity of 96%. A strong inverse Pearson's correlation (r = -0.95) was found between the assigned score and patient's Glasgow Coma Scale at the time of admission. The CE-FLAIR sequence is better suited for evaluating infectious meningitis and could be included as a part of the routine MR imaging protocol
Thomalla, Götz; Boutitie, Florent; Fiebach, Jochen B; Simonsen, Claus Z; Pedraza, Salvador; Lemmens, Robin; Nighoghossian, Norbert; Roy, Pascal; Muir, Keith W; Ebinger, Martin; Ford, Ian; Cheng, Bastian; Galinovic, Ivana; Cho, Tae-Hee; Puig, Josep; Thijs, Vincent; Endres, Matthias; Fiehler, Jens; Gerloff, Christian
2018-01-01
Background Diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) mismatch was suggested to identify stroke patients with unknown time of symptom onset likely to be within the time window for thrombolysis. Aims We aimed to study clinical characteristics associated with DWI-FLAIR mismatch in patients with unknown onset stroke. Methods We analyzed baseline MRI and clinical data from patients with acute ischemic stroke proven by DWI from WAKE-UP, an investigator-initiated, randomized, placebo-controlled trial of MRI-based thrombolysis in stroke patients with unknown time of symptom onset. Clinical characteristics were compared between patients with and without DWI-FLAIR mismatch. Results Of 699 patients included, 418 (59.8%) presented with DWI-FLAIR mismatch. A shorter delay between last seen well and symptom recognition (p = 0.0063), a shorter delay between symptom recognition and arrival at hospital (p = 0.0025), and history of atrial fibrillation (p = 0.19) were predictors of DWI-FLAIR mismatch in multivariate analysis. All other characteristics were comparable between groups. Conclusions There are only minor differences in measured clinical characteristics between unknown symptom onset stroke patients with and without DWI-FLAIR mismatch. DWI-FLAIR mismatch as an indicator of stroke onset within 4.5 h shows no relevant association with commonly collected clinical characteristics of stroke patients. Clinical Trial Registration URL: http://www.clinicaltrials.gov . Unique identifier: NCT01525290; URL: https://www.clinicaltrialsregister.eu . Unique identifier: 2011-005906-32.
Energy Technology Data Exchange (ETDEWEB)
Heo, Young Jin [University of Ulsan College of Medicine, Asan Medical Center, Department of Radiology, Research Institute of Radiology, Seoul (Korea, Republic of); Inje University, Department of Radiology, Busan Paik Hospital, Busan (Korea, Republic of); Kim, Sang Joon; Kim, Ho Sung; Choi, Choong Gon; Jung, Seung Chai [University of Ulsan College of Medicine, Asan Medical Center, Department of Radiology, Research Institute of Radiology, Seoul (Korea, Republic of); Lee, Jung Kyo [University of Ulsan College of Medicine, Asan Medical Center, Department of Neurosurgery, Seoul (Korea, Republic of); Lee, Chong Sik; Chung, Sun J. [University of Ulsan College of Medicine, Asan Medical Center, Department of Neurology, Seoul (Korea, Republic of); Cho, So Hyun [Department of Radiology, Busan (Korea, Republic of); Lee, Gyoung Ro [Philips HealthCare Korea, Seoul (Korea, Republic of)
2015-09-15
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an accepted treatment for advanced Parkinson's disease (PD). However, targeting the STN is difficult due to its relatively small size and variable location. The purpose of this study was to assess which of the following sequences obtained with the 3.0 T MR system can accurately delineate the STN: coronal 3D fluid-attenuated inversion recovery (FLAIR), 2D T2*-weighted fast-field echo (T2*-FFE) and 2D T2-weighted turbo spin-echo (TSE) sequences. We included 20 consecutive patients with PD who underwent 3.0 T MR for DBS targeting. 3D FLAIR, 2D T2*-FFE and T2-TSE images were obtained for all study patients. Image quality and demarcation of the STN were analysed using 4-point scales, and contrast ratio (CR) of the STN and normal white matter was calculated. The Friedman test was used to compare the three sequences. In qualitative analysis, the 2D T2*-FFE image showed more artefacts than 3D FLAIR or 2D T2-TSE, but the difference did not reach statistical significance. 3D FLAIR images showed significantly superior demarcation of the STN compared with 2D T2*-FFE and T2-TSE images (P < 0.001, respectively). The CR of 3D FLAIR was significantly higher than that of 2D T2*-FFE or T2-TSE images in multiple comparison correction (P < 0.001), but there was no significant difference in the CR between 2D T2*-FFE and T2-TSE images. Coronal 3D FLAIR images showed the most accurate demarcation of the STN for DBS targeting among coronal 3D FLAIR, 2D T2*-FFE and T2-TSE images. (orig.)
International Nuclear Information System (INIS)
Heo, Young Jin; Kim, Sang Joon; Kim, Ho Sung; Choi, Choong Gon; Jung, Seung Chai; Lee, Jung Kyo; Lee, Chong Sik; Chung, Sun J.; Cho, So Hyun; Lee, Gyoung Ro
2015-01-01
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an accepted treatment for advanced Parkinson's disease (PD). However, targeting the STN is difficult due to its relatively small size and variable location. The purpose of this study was to assess which of the following sequences obtained with the 3.0 T MR system can accurately delineate the STN: coronal 3D fluid-attenuated inversion recovery (FLAIR), 2D T2*-weighted fast-field echo (T2*-FFE) and 2D T2-weighted turbo spin-echo (TSE) sequences. We included 20 consecutive patients with PD who underwent 3.0 T MR for DBS targeting. 3D FLAIR, 2D T2*-FFE and T2-TSE images were obtained for all study patients. Image quality and demarcation of the STN were analysed using 4-point scales, and contrast ratio (CR) of the STN and normal white matter was calculated. The Friedman test was used to compare the three sequences. In qualitative analysis, the 2D T2*-FFE image showed more artefacts than 3D FLAIR or 2D T2-TSE, but the difference did not reach statistical significance. 3D FLAIR images showed significantly superior demarcation of the STN compared with 2D T2*-FFE and T2-TSE images (P < 0.001, respectively). The CR of 3D FLAIR was significantly higher than that of 2D T2*-FFE or T2-TSE images in multiple comparison correction (P < 0.001), but there was no significant difference in the CR between 2D T2*-FFE and T2-TSE images. Coronal 3D FLAIR images showed the most accurate demarcation of the STN for DBS targeting among coronal 3D FLAIR, 2D T2*-FFE and T2-TSE images. (orig.)
International Nuclear Information System (INIS)
Maeda, M.; Sakuma, H.; Takeda, K.; Yagishita, A.; Yamamoto, T.
2003-01-01
A variety of central nervous system (CNS) diseases are associated with abnormal hyperintensity within the subarachnoid space (SAS) by fluid-attenuated inversion-recovery (FLAIR) MR imaging. Careful attention to the SAS can provide additional useful information that may not be available with conventional MR sequences. The purpose of this article is to provide a pictorial essay about CNS diseases and FLAIR images with abnormal hyperintensity within the SAS. We present several CNS diseases including subarachnoid hemorrhage, meningitis, leptomeningeal metastases, acute infarction, and severe arterial occlusive diseases such as moya-moya disease. We also review miscellaneous diseases or normal conditions that may exhibit cerebrospinal fluid hyperintensity on FLAIR images. Although the detection of abnormal hyperintensity suggests the underlying CNS diseases and narrows differential diagnoses, FLAIR imaging sometimes presents artifactual hyperintensity within the SAS that can cause the misinterpretation of normal SAS as pathologic conditions; therefore, radiologists should be familiar with such artifactual conditions as well as pathologic conditions shown as hyperintensity by FLAIR images. This knowledge is helpful in establishing the correct diagnosis. (orig.)
Jafari-Khouzani, Kourosh; Loebel, Franziska; Bogner, Wolfgang; Rapalino, Otto; Gonzalez, Gilberto R; Gerstner, Elizabeth; Chi, Andrew S; Batchelor, Tracy T; Rosen, Bruce R; Unkelbach, Jan; Shih, Helen A; Cahill, Daniel P; Andronesi, Ovidiu C
2016-11-01
Gliomas with mutant isocitrate dehydrogenase (IDH) produce high levels of 2-hydroxyglutarate (2HG) that can be quantitatively measured by 3D magnetic resonance spectroscopic imaging (MRSI). Current glioma MRI primarily relies upon fluid-attenuated inversion recovery (FLAIR) hyperintensity for treatment planning, although this lacks specificity for tumor cells. Here, we investigated the relationship between 2HG and FLAIR in mutant IDH glioma patients to determine whether 2HG mapping is valuable for radiotherapy planning. Seventeen patients with mutant IDH1 gliomas were imaged by 3 T MRI. A 3D MRSI sequence was employed to specifically image 2HG. FLAIR imaging was performed using standard clinical protocol. Regions of interest (ROIs) were determined for FLAIR and optimally thresholded 2HG hyperintensities. The overlap, displacement, and volumes of 2HG and FLAIR ROIs were calculated. In 8 of 17 (47%) patients, the 2HG volume was larger than FLAIR volume. Across the entire cohort, the mean volume of 2HG was 35.3 cc (range, 5.3-92.7 cc), while the mean volume of FLAIR was 35.8 cc (range, 6.3-140.8 cc). FLAIR and 2HG ROIs had mean overlap of 0.28 (Dice coefficients range, 0.03-0.57) and mean displacement of 12.2 mm (range, 3.2-23.5 mm) between their centers of mass. Our results indicate that for a substantial number of patients, the 2HG volumetric assessment of tumor burden is more extensive than FLAIR volume. In addition, there is only partial overlap and asymmetric displacement between the centers of FLAIR and 2HG ROIs. These results may have important implications for radiotherapy planning of IDH mutant glioma. © The Author(s) 2016. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Contrast-enhanced FLAIR in the early diagnosis of infectious meningitis
Energy Technology Data Exchange (ETDEWEB)
Splendiani, Alesssandra; Puglielli, Edoardo; Amicis, Rosanna De; Masciocchi, Carlo; Gallucci, Massimo [University of L' Aquila, Department of Radiology, L' Aquila (Italy); Necozione, Stefano [University of L' Aquila, Department of Statistic, L' Aquila (Italy)
2005-08-01
We investigated the accuracy of MRI in the early diagnosis of infectious meningitis with emphasis on the value of gadolinium-enhanced fluid-attenuated inversion recovery (FLAIR) sequence. Twenty-seven patients with clinical suspicion of infectious meningitis were included. MRI was performed within 3 h of clinical evaluation. For all patients, T1-weighted spin-echo, dual-echo T2-weighted fast-spin-echo and FLAIR sequences were performed, followed by gadolinium-enhanced T1-weighted spin-echo and FLAIR sequences. Final diagnosis was based on the clinical findings and the analysis of cerebrospinal fluid, obtained by lumbar puncture after the MRI. Infectious meningitis was confirmed in 12 patients. In all of these patients of the plain studies, FLAIR was positive in only four patients. MRI gadolinium-enhanced FLAIR showed abnormal meningeal enhancement in all 12 patients, while gadolinium-enhanced T1-weighted spin-echo was positive only in six cases. There were no false-positive or false-negative results. It is concluded that MRI could have an important role in the early screening for infectious meningitis, provided a gadolinium-enhanced FLAIR sequence is used. (orig.)
Contrast-enhanced FLAIR in the early diagnosis of infectious meningitis
International Nuclear Information System (INIS)
Splendiani, Alesssandra; Puglielli, Edoardo; Amicis, Rosanna De; Masciocchi, Carlo; Gallucci, Massimo; Necozione, Stefano
2005-01-01
We investigated the accuracy of MRI in the early diagnosis of infectious meningitis with emphasis on the value of gadolinium-enhanced fluid-attenuated inversion recovery (FLAIR) sequence. Twenty-seven patients with clinical suspicion of infectious meningitis were included. MRI was performed within 3 h of clinical evaluation. For all patients, T1-weighted spin-echo, dual-echo T2-weighted fast-spin-echo and FLAIR sequences were performed, followed by gadolinium-enhanced T1-weighted spin-echo and FLAIR sequences. Final diagnosis was based on the clinical findings and the analysis of cerebrospinal fluid, obtained by lumbar puncture after the MRI. Infectious meningitis was confirmed in 12 patients. In all of these patients of the plain studies, FLAIR was positive in only four patients. MRI gadolinium-enhanced FLAIR showed abnormal meningeal enhancement in all 12 patients, while gadolinium-enhanced T1-weighted spin-echo was positive only in six cases. There were no false-positive or false-negative results. It is concluded that MRI could have an important role in the early screening for infectious meningitis, provided a gadolinium-enhanced FLAIR sequence is used. (orig.)
International Nuclear Information System (INIS)
Riney, Catherine J.; Chong, William K.; Clark, Chris A.; Cross, J. Helen
2012-01-01
Purpose: Magnetic resonance imaging (MRI), in particular fluid-attenuated inversion-recovery (FLAIR), has transformed the delineation of structural brain pathology associated with focal epilepsy. However, to date there is no literature on voxel based morphometry (VBM) of FLAIR in children with epilepsy. The aim of this study was to explore the role of visual and VBM assessment of FLAIR in pre-operative investigation of children with intractable focal epilepsy. Methods: Children with intractable epilepsy due to focal cortical dysplasia (FCD) and children with intractable cryptogenic focal epilepsy (CFE) were investigated. FLAIR and T1-weighted MRI were acquired on a 1.5T MRI scanner (Siemens, Erlangen, Germany). VBM was performed using SPM5 (Wellcome Institute of Cognitive Neuroscience, London). Results: Eight children with FCD (M = 5, age 7.9–17.3 years) and 14 children with CFE (M = 8, 7.8–16.8 years) were enrolled. VBM of FLAIR detected 7/8 (88%) of FCD whilst VBM of T1-weighted MRI detected only 3/8 (38%) FCD. VBM of FLAIR detected abnormality in 4/14 children with CFE, in 2/14 (14%) the abnormality was concordant with other data on the epileptogenic zone and with visible abnormality on repeat visual inspection of MR data. VBM of T1-weighed MRI detected abnormality in 2/14 children with CFE, none of which correlated with visible abnormality. Discussion: This study highlights the important role that FLAIR imaging has in the pre-operative assessment of children with intractable epilepsy. VBM of FLAIR may provide important information allowing selection of children with intractable CFE who are likely to benefit from further neuroradiological or neurophysiological evaluation.
Energy Technology Data Exchange (ETDEWEB)
Lavdas, Eleftherios; Vlychou, Marianna; Arikidis, Nikos; Kapsalaki, Eftychia; Roka, Violetta; Fezoulidis, Ioannis V. (Dept. of Radiology, Univ. Hospital of Larissa, Medical School of Thessaly, Mezourlo (Greece)), e-mail: mvlychou@med.uth.gr
2010-04-15
Background: T1-weighted fluid-attenuated inversion recovery (FLAIR) sequence has been reported to provide improved contrast between lesions and normal anatomical structures compared to T1-weighted fast spin-echo (FSE) imaging at 1.5T regarding imaging of the lumbar spine. Purpose: To compare T1-weighted FSE and fast T1-weighted FLAIR imaging in normal anatomic structures and degenerative and metastatic lesions of the lumbar spine at 3.0T. Material and Methods: Thirty-two consecutive patients (19 females, 13 males; mean age 44 years, range 30-67 years) with lesions of the lumbar spine were prospectively evaluated. Sagittal images of the lumbar spine were obtained using T1-weighted FSE and fast T1-weighted FLAIR sequences. Both qualitative and quantitative analyses measuring the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and relative contrast (ReCon) between degenerative and metastatic lesions and normal anatomic structures were conducted, comparing these sequences. Results: On quantitative evaluation, SNRs of cerebrospinal fluid (CSF), nerve root, and fat around the root of fast T1-weighted FLAIR imaging were significantly lower than those of T1-weighted FSE images (P<0.001). CNRs of normal spinal cord/CSF and disc herniation/ CSF for fast T1-weighted FLAIR images were significantly higher than those for T1-weighted FSE images (P<0.001). ReCon of normal spinal cord/CSF, disc herniation/CSF, and vertebral lesions/CSF for fast T1-weighted FLAIR images were significantly higher than those for T1-weighted FSE images (P<0.001). On qualitative evaluation, it was found that CSF nulling and contrast at the spinal cord (cauda equina)/CSF interface for T1-weighted FLAIR images were significantly superior compared to those for T1-weighted FSE images (P<0.001), and the disc/spinal cord (cauda equina) interface was better for T1-weighted FLAIR images (P<0.05). Conclusion: The T1-weighted FLAIR sequence may be considered as the preferred lumbar spine imaging
FLAIR images of mild head trauma with transient amnesia
Energy Technology Data Exchange (ETDEWEB)
Wakamoto, Hirooki; Miyazaki, Hiromichi; Inaba, Makoto; Ishiyama, Naomi [Hiratsuka City Hospital, Kanagawa (Japan); Kawase, Takeshi
1998-11-01
A newly advanced MRI pulse sequence, the FLAIR (fluid-attenuated inversion recovery) imaging, in which a long TE spin echo sequence is used with suppression of the CSF with an inversion pulse, displays the CSF space as a no signal intensity area. We examined 45 cases of mild head trauma with posttraumatic amnesia by FLAIR images and could detect some findings which could not be detected by CT scan and conventional MR images. These findings could be detected in many patients with long posttraumatic amnesia (over 2 hours), but they could not be detected in patients with short posttraumatic amnesia (within 30 mins). These findings existed surrounding lateral ventricles and we classified them into 3 types: type 1 is anterior horn of lateral ventricle, type 2 is the base of frontal lobe, and type 3 is cerebral deep white matter. Some of them were examined again by FLAIR images a month later, and these findings had disappeared. We suspect that these lesions were brain edema or mild contusion without hemorrhage. (author)
FLAIR images of mild head trauma with transient amnesia
International Nuclear Information System (INIS)
Wakamoto, Hirooki; Miyazaki, Hiromichi; Inaba, Makoto; Ishiyama, Naomi; Kawase, Takeshi
1998-01-01
A newly advanced MRI pulse sequence, the FLAIR (fluid-attenuated inversion recovery) imaging, in which a long TE spin echo sequence is used with suppression of the CSF with an inversion pulse, displays the CSF space as a no signal intensity area. We examined 45 cases of mild head trauma with posttraumatic amnesia by FLAIR images and could detect some findings which could not be detected by CT scan and conventional MR images. These findings could be detected in many patients with long posttraumatic amnesia (over 2 hours), but they could not be detected in patients with short posttraumatic amnesia (within 30 mins). These findings existed surrounding lateral ventricles and we classified them into 3 types: type 1 is anterior horn of lateral ventricle, type 2 is the base of frontal lobe, and type 3 is cerebral deep white matter. Some of them were examined again by FLAIR images a month later, and these findings had disappeared. We suspect that these lesions were brain edema or mild contusion without hemorrhage. (author)
Energy Technology Data Exchange (ETDEWEB)
Wan, Chih-Cheng; Chen, David Yen-Ting; Tseng, Ying-Chi; Lee, Kun-Yu; Chiang, Chen-Hua; Chen, Chi-Jen [Taipei Medical University, Department of Radiology, Shuang-Ho Hospital, New Taipei City (China); Taipei Medical University, School of Medicine, College of Medicine, Taipei (China); Yan, Feng-Xian [Taipei Medical University, Department of Radiology, Shuang-Ho Hospital, New Taipei City (China)
2017-08-15
No reliable imaging sign predicting cerebral hyperperfusion after intracranial arterial stenting (IAS) had been described in the literature. This study evaluated the effect of fluid-attenuated inversion recovery vascular hyperintensities (FVHs), also called hyperintense vessel sign on T2-weighted fluid-attenuated inversion recovery (T2-FLAIR) MR images, in predicting significant increase in cerebral blood flow (CBF) defined by arterial spin labeling (ASL) after IAS. We reviewed ASL CBF images and T2-FLAIR MR images before (D0), 1 day after (D1), and 3 days after (D3) IAS of 16 patients. T1-weighted MR images were used as cerebral maps for calculating CBF. The changes in CBF values after IAS were calculated in and compared among stenting and nonstenting vascular territories. An increase more than 50% of CBF was considered as hyperperfusion. The effect of FVHs in predicting hyperperfusion was calculated. The D1 CBF value was significantly higher than the D0 CBF value in stenting vascular, contralateral anterior cerebral artery, contralateral middle cerebral artery, and contralateral posterior cerebral artery (PCA) territories (all P <.05). The D1 and D3 CBF values were significantly higher than the D0 CBF value in overall vascular (P <.001), overall nonstenting vascular (P <.001), and ipsilateral PCA (P <.05) territories. The rate of more than 50% increases in CBF was significantly higher in patients who exhibited asymmetric FVHs than in those who did not exhibit these findings. FVHs could be a critical predictor of a significant increase in CBF after IAS. (orig.)
3D-Flair sequence at 3T in cochlear otosclerosis
Energy Technology Data Exchange (ETDEWEB)
Lombardo, Francesco; De Cori, Sara; Aghakhanyan, Gayane; Montanaro, Domenico; De Marchi, Daniele; Frijia, Francesca; Canapicchi, Raffaello [Fondazione CNR Regione Toscana ' ' G. Monasterio' ' , Neuroradiology Unit, Pisa (Italy); Fortunato, Susanna; Forli, Francesca; Berrettini, Stefano [University of Pisa, ENT Audiology Phoniatry Unit, Department of Neuroscience, Pisa (Italy); Chiappino, Dante [Fondazione CNR Regione Toscana ' ' G. Monasterio' ' , Department of Radiology, Massa (Italy)
2016-10-15
To assess the capability of three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) sequences in detecting signal alterations of the endolabyrinthine fluid in patients with otosclerosis. 3D-FLAIR before and after (-/+) gadolinium (Gd) administration was added to the standard MR protocol and acquired in 13 patients with a clinical/audiological diagnosis of severe/profound hearing loss in otosclerosis who were candidates for cochlear implantation and in 11 control subjects using 3-T magnetic resonance imaging (MRI) equipment. The MRI signal of the fluid-filled cochlea was assessed both visually and calculating the signal intensity ratio (SIR = signal intensity cochlea/brainstem). We revealed no endocochlear signal abnormalities on T1-weighted -/+ Gd images for either group, while on 3D-FLAIR we found bilateral hyperintensity with enhancement after Gd administration in eight patients and bilateral hyperintensity without enhancement in one patient. No endocochlear signal abnormalities were detected in other patients or the control group. Using 3-T MRI equipment, the 3D-FLAIR -/+ Gd sequence is able to detect the blood-labyrinth barrier (BLB) breakdown responsible for alterations of the endolabyrinthine fluid in patients with cochlear otosclerosis. We believe that 3D-FLAIR +/- Gd is an excellent imaging modality to assess the intra-cochlear damage in otosclerosis patients. (orig.)
3D-FLAIR MRI in facial nerve paralysis with and without audio-vestibular disorder.
Nakata, Seiichi; Mizuno, Terukazu; Naganawa, Shinji; Sugiura, Makoto; Yoshida, Tadao; Teranishi, Masaaki; Sone, Michihiko; Nakashima, Tsutomu
2010-05-01
Among patients with facial nerve paralysis, significant difference was observed on three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging (3D-FLAIR MRI) between those with and without audio-vestibular disturbance. This MRI technique may contribute to elucidation of the pathology of Ramsay Hunt syndrome and Bell's palsy. To evaluate the 3D-FLAIR MRI findings in patients who have facial nerve paralysis with and without audio-vestibular disturbance. 3D-FLAIR MRI was performed with and without gadolinium enhancement in 15 patients (5 men and 10 women) with unilateral facial nerve paralysis: 3 patients with Ramsay Hunt syndrome, 3 patients having facial nerve paralysis with hearing loss or vertigo without vesicles, and 9 patients with Bell's palsy. Five of the six patients with audio-vestibular disturbance showed high signals in the inner ear on precontrast 3D-FLAIR. In comparison, among nine patients with Bell's palsy, only one patient showed high signals in the inner ear on precontrast 3D-FLAIR (p < 0.05).
International Nuclear Information System (INIS)
Ogami, Ryo; Nakahara, Toshinori; Hamasaki, Osamu; Araki, Hayato; Kurisu, Kaoru
2011-01-01
Purpose: A rare complication of carotid artery stenting (CAS), prolonged reversible neurological symptoms with delayed cerebrospinal fluid (CSF) space enhancement on fluid attenuated inversion recovery (FLAIR) images, is associated with blood–brain barrier (BBB) disruption. We prospectively identified patients who showed CSF space enhancement on FLAIR images. Methods: Nineteen patients—5 acute-phase and 14 scheduled—underwent 21 CAS procedures. Balloon catheters were navigated across stenoses, angioplasty was performed using a neuroprotective balloon, and stents were placed with after dilation under distal balloon protection. CSF space hyperintensity or obscuration on FLAIR after versus before CAS indicated CSF space enhancement. Correlations with clinical factors were examined. Results: CSF space was enhanced on FLAIR in 12 (57.1%) cases. Postprocedural CSF space enhancement was significantly related to age, stenosis rate, acute-stage procedure, and total occlusion time. All acute-stage CAS patients showed delayed enhancement. Only age was associated with delayed CSF space enhancement in scheduled CAS patients. Conclusions: Ischemic intolerance for severe carotid artery stenosis and temporary neuroprotective balloon occlusion, causing reperfusion injury, seem to be the main factors that underlie BBB disruption with delayed CSF space enhancement shortly after CAS, rather than sudden poststenting hemodynamic change. Our results suggest that factors related to hemodynamic instability or ischemic intolerance seem to be associated with post-CAS BBB vulnerability. Patients at risk for hemodynamic instability or with ischemic intolerance, which decrease BBB integrity, require careful management to prevent intracranial hemorrhagic and other post-CAS complications.
Association between the perfusion/diffusion and diffusion/FLAIR mismatch: data from the AXIS2 trial.
Wouters, Anke; Dupont, Patrick; Ringelstein, Erich B; Norrving, Bo; Chamorro, Angel; Grond, Martin; Laage, Rico; Schneider, Armin; Wilms, Guido; Thomalla, Götz; Lemmens, Robin; Thijs, Vincent N
2015-10-01
The perfusion-/diffusion-weighted imaging (PWI/DWI) mismatch and the diffusion/fluid attenuated inversion recovery (DWI/FLAIR) mismatch are magnetic resonance imaging (MRI) markers of evolving brain ischemia. We examined whether the DWI/FLAIR mismatch was independently associated with the PWI/DWI mismatch. Furthermore, we determined whether the presence of the DWI/FLAIR mismatch in patients with the PWI/DWI mismatch would provide additional information regarding last seen normal time (LTM). We used data from the 'AX200 for ischemic stroke' trial (AXIS 2 study NCT00927836). We studied the association between the presence of the DWI/FLAIR and PWI/DWI mismatch, baseline National Institute of Health Stroke Scale (NIHSS), age, ischemic-core volume, gender, intravenous (IV) tissue plasminogen activator (tPA), and perfusion-mismatch volume in univariate analysis. Significant variables (Pmismatch. Patients with the double mismatch pattern had a shorter LTM than patients with the PWI/DWI mismatch alone (Median difference 90 minutes, Pmismatch patterns (odds ratio (OR) 2.6, 95% confidence interval (CI) 1.2 to 5.4). Our study implies that the DWI/FLAIR mismatch and PWI/DWI mismatch are strongly associated, independent from LTM. Furthermore, in the presence of the PWI/DWI mismatch, the DWI/FLAIR pattern indicates a shorter LTM. This could have implications in selecting patients for reperfusion therapy.
MRI diagnosis of traumatic fornical injury. Investigation utilizing FLAIR Technique
International Nuclear Information System (INIS)
Asai, Toshiharu; Kataoka, Kazuo; Uejima, Toshifumi; Maruyama, Jiro; Sakata, Ikuhiro; Taneda, Mamoru
1996-01-01
We studied traumatic fornix injuries by using the fluid attenuated inversion recovery (FLAIR) technique which provides T 2 -weighted images without the unwanted influence of cerebrospinal fluid (CSF) signals. 5-21 days (average: 10.3) after injury, we performed MRI on 14 patients (mean age: 22.6 years) who were clinically diagnosed as having diffuse axonal injury (DAI). The mid-sagittal FLAIR images in seven of the 14 patients clearly revealed T 2 -prolonged fornix lesions and the concurrent corpus callosum lesions. The same fornix lesions, as detected by the spin echo technique, were blurred by the partial volume effects and motion artifacts derived from the surrounding CSF signals. The accompanying callosal lesions were mainly in the splenium. Of the seven patients with fornix injuries, three had T 2 -prolonged lesions in the septum pellucidum. With respect to the outcome, there was no difference between patients with and without fornix injury. In conclusion, the FLAIR technique is appropriate for detecting fornix injuries adjacent to the CSF space. (author)
MRI diagnosis of traumatic fornical injury. Investigation utilizing FLAIR Technique
Energy Technology Data Exchange (ETDEWEB)
Asai, Toshiharu; Kataoka, Kazuo; Uejima, Toshifumi; Maruyama, Jiro; Sakata, Ikuhiro; Taneda, Mamoru [Kinki Univ., Sayama, Osaka (Japan) School of Medicine
1996-06-01
We studied traumatic fornix injuries by using the fluid attenuated inversion recovery (FLAIR) technique which provides T{sub 2}-weighted images without the unwanted influence of cerebrospinal fluid (CSF) signals. 5-21 days (average: 10.3) after injury, we performed MRI on 14 patients (mean age: 22.6 years) who were clinically diagnosed as having diffuse axonal injury (DAI). The mid-sagittal FLAIR images in seven of the 14 patients clearly revealed T{sub 2}-prolonged fornix lesions and the concurrent corpus callosum lesions. The same fornix lesions, as detected by the spin echo technique, were blurred by the partial volume effects and motion artifacts derived from the surrounding CSF signals. The accompanying callosal lesions were mainly in the splenium. Of the seven patients with fornix injuries, three had T{sub 2}-prolonged lesions in the septum pellucidum. With respect to the outcome, there was no difference between patients with and without fornix injury. In conclusion, the FLAIR technique is appropriate for detecting fornix injuries adjacent to the CSF space. (author)
Ganesan, K; Bydder, G M
2014-09-01
This study compared T1 fluid attenuation inversion recovery (FLAIR) and T1 turbo spin echo (TSE) sequences for evaluation of cervical spine degenerative disease at 3 T. 72 patients (44 males and 28 females; mean age of 39 years; age range, 27-75 years) with suspected cervical spine degenerative disease were prospectively evaluated. Sagittal images of the spine were obtained using T1 FLAIR and T1 TSE sequences. Two experienced neuroradiologists compared the sequences qualitatively and quantitatively. On qualitative evaluation, cerebrospinal fluid (CSF) nulling and contrast at cord-CSF, disc-CSF and disc-cord interfaces were significantly higher on fast T1 FLAIR images than on T1 TSE images (p degenerative disease, owing to higher cord-CSF, disc-cord and disc-CSF contrast. However, intrinsic cord contrast is low on T1 FLAIR images. T1 FLAIR is more promising and sensitive than T1 TSE for evaluation of degenerative spondyloarthropathy and may provide a foundation for development of MR protocols for early detection of degenerative and neoplastic diseases.
Kokkinos, Vasileios; Kallifatidis, Alexandros; Kapsalaki, Eftychia Z; Papanikolaou, Nikolaos; Garganis, Kyriakos
2017-05-01
The transmantle sign is a distinctive imaging marker of focal cortical dysplasia (FCD) type II in frontal lobe epilepsy (FLE), which is revealed predominantly by fluid-attenuation inversion recovery (FLAIR) sequences. Although the transmantle sign detection yield is high by routine imaging protocols for epilepsy at 3T, most centers around the world have access to 1.5T MR technology and FLE patients often receive negative imaging reports. This study investigates the optimization of transmantle detection yield at 1.5T by introducing a 3D thin-slice isotropic FLAIR sequence in the epilepsy imaging protocol. Twenty FLE patients underwent diagnostic imaging for epilepsy with typical 2D thick-slice (3.0mm) coronal FLAIR sequences and a 3D thin-slice (1.0mm) isotropic FLAIR sequences at 1.5T, and transmantle sign detection yields and thickness measurements were derived. The 2D thick-slice FLAIR detected a transmantle sign in seven (35.0%) patients. The 3D isotropic thin-slice FLAIR detected a transmantle sign in eleven (55.0%) patients, thereby increasing the transmantle sign detection yield by 57.4%. The mean transmantle sign thickness by thick images was 12.3mm, by thin images was 8.9mm, and in the patients undetected by thick FLAIR was 3.5mm. This study showed that the extratemporal transmantle sign in FLE patients can be thin enough to be missed by thick-slice FLAIR sequences at 1.5T. By introducing 3D thin-slice isotropic FLAIR, false-negative reports can be reduced without reference for higher MR field structural scanning or other modalities, and more FLE patients can benefit from epilepsy surgery candidacy. Copyright © 2017 Elsevier B.V. All rights reserved.
FLAIR lesion segmentation: Application in patients with brain tumors and acute ischemic stroke
Energy Technology Data Exchange (ETDEWEB)
Artzi, Moran, E-mail: artzimy@gmail.com [The Functional Brain Center, The Wohl Institute for Advanced Imaging, Tel Aviv Sourasky Medical Center, Tel Aviv (Israel); Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv (Israel); Aizenstein, Orna, E-mail: ornaaize@gmail.com [The Functional Brain Center, The Wohl Institute for Advanced Imaging, Tel Aviv Sourasky Medical Center, Tel Aviv (Israel); Jonas-Kimchi, Tali, E-mail: talijk@tlvmc.gov.il [Radiology Department, Tel Aviv Sourasky Medical Center, Tel Aviv (Israel); Myers, Vicki, E-mail: vicki_myers@hotmail.com [The Functional Brain Center, The Wohl Institute for Advanced Imaging, Tel Aviv Sourasky Medical Center, Tel Aviv (Israel); Hallevi, Hen, E-mail: hen.hallevi@gmail.com [Neurology Department, Tel Aviv Sourasky Medical Center, Tel Aviv (Israel); Ben Bashat, Dafna, E-mail: dafnab@tlvmc.gov.il [The Functional Brain Center, The Wohl Institute for Advanced Imaging, Tel Aviv Sourasky Medical Center, Tel Aviv (Israel); Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv (Israel)
2013-09-15
Background: Lesion size in fluid attenuation inversion recovery (FLAIR) images is an important clinical parameter for patient assessment and follow-up. Although manual delineation of lesion areas considered as ground truth, it is time-consuming, highly user-dependent and difficult to perform in areas of indistinct borders. In this study, an automatic methodology for FLAIR lesion segmentation is proposed, and its application in patients with brain tumors undergoing therapy; and in patients following stroke is demonstrated. Materials and methods: FLAIR lesion segmentation was performed in 57 magnetic resonance imaging (MRI) data sets obtained from 44 patients: 28 patients with primary brain tumors; 5 patients with recurrent-progressive glioblastoma (rGB) who were scanned longitudinally during anti-angiogenic therapy (18 MRI scans); and 11 patients following ischemic stroke. Results: FLAIR lesion segmentation was obtained in all patients. When compared to manual delineation, a high visual similarity was observed, with an absolute relative volume difference of 16.80% and 20.96% and a volumetric overlap error of 24.87% and 27.50% obtained for two raters: accepted values for automatic methods. Quantitative measurements of the segmented lesion volumes were in line with qualitative radiological assessment in four patients who received anti-anogiogenic drugs. In stroke patients the proposed methodology enabled identification of the ischemic lesion and differentiation from other FLAIR hyperintense areas, such as pre-existing disease. Conclusion: This study proposed a replicable methodology for FLAIR lesion detection and quantification and for discrimination between lesion of interest and pre-existing disease. Results from this study show the wide clinical applications of this methodology in research and clinical practice.
FLAIR lesion segmentation: Application in patients with brain tumors and acute ischemic stroke
International Nuclear Information System (INIS)
Artzi, Moran; Aizenstein, Orna; Jonas-Kimchi, Tali; Myers, Vicki; Hallevi, Hen; Ben Bashat, Dafna
2013-01-01
Background: Lesion size in fluid attenuation inversion recovery (FLAIR) images is an important clinical parameter for patient assessment and follow-up. Although manual delineation of lesion areas considered as ground truth, it is time-consuming, highly user-dependent and difficult to perform in areas of indistinct borders. In this study, an automatic methodology for FLAIR lesion segmentation is proposed, and its application in patients with brain tumors undergoing therapy; and in patients following stroke is demonstrated. Materials and methods: FLAIR lesion segmentation was performed in 57 magnetic resonance imaging (MRI) data sets obtained from 44 patients: 28 patients with primary brain tumors; 5 patients with recurrent-progressive glioblastoma (rGB) who were scanned longitudinally during anti-angiogenic therapy (18 MRI scans); and 11 patients following ischemic stroke. Results: FLAIR lesion segmentation was obtained in all patients. When compared to manual delineation, a high visual similarity was observed, with an absolute relative volume difference of 16.80% and 20.96% and a volumetric overlap error of 24.87% and 27.50% obtained for two raters: accepted values for automatic methods. Quantitative measurements of the segmented lesion volumes were in line with qualitative radiological assessment in four patients who received anti-anogiogenic drugs. In stroke patients the proposed methodology enabled identification of the ischemic lesion and differentiation from other FLAIR hyperintense areas, such as pre-existing disease. Conclusion: This study proposed a replicable methodology for FLAIR lesion detection and quantification and for discrimination between lesion of interest and pre-existing disease. Results from this study show the wide clinical applications of this methodology in research and clinical practice
Directory of Open Access Journals (Sweden)
Marcos Alberto da Costa Machado Júnior
2001-06-01
Full Text Available O objetivo deste estudo é analisar as alterações morfológicas e de intensidade de sinal das regiões hipocampais em pacientes, com epilepsia temporal fármaco-resistente. Para tal, estudamos 8 pacientes com esclerose mesial temporal, utilizando aparelhagem de RM de 1,5T, com sequências Spin Eco - SE, Fast Spin Eco - FSE, Fluid Atenuation Inversion Recovery, com Eco Planar Imaging - FLAIR-EPI. Observamos a superioridade da sequência FLAIR na detecção do aumento da intensidade de sinal da região hipocampal, particularmente com cortes coronais, em relação às sequências SE e FSE, com a vantagem de ser uma técnica de rápida execução. A sequência STIR evidenciou adelgaçamento da cortical do hipocampo, na metade dos casos que apresentavam alteração de sinal.The purpose of this study is to evaluate morpholologycal and signal intensity changes in the hippocampus in patients with medically intractable temporal lobe epilepsy. We studied 8 patients with mesial temporal sclerosis using a 1.5 -T MR and the following sequences Spin Eco- SE, Fast Spin Echo- FSE, Fluid Atenuation Inversion Recovery Echo Planar Imaging - FLAIR-EPI. We noticed a sensitive increase signal intensity on FLAIR- EPI sequences, particularly, in coronal images, than on SE and FSE sequences. The STIR sequence showed a cortical hippocampus atrophy in half of the cases, in whom signal abnormalities were present.
Rauf, N.; Alam, D. Y.; Jamaluddin, M.; Samad, B. A.
2018-03-01
The Magnetic Resonance Imaging (MRI) is a medical imaging technique that uses the interaction between the magnetic field and the nuclear spins. MRI can be used to show disparity of pathology by transversal relaxation time (T2) weighted images. Some techniques for producing T2-weighted images are Periodically Rotated Overlapping Parallel Lines with Enhanced Reconstruction (PROPELLER) and Fluid Attenuated Inversion Recovery (FLAIR). A comparison of T2 PROPELLER and T2 FLAIR parameters in MRI image has been conducted. And improve Image Quality the image by using RadiAnt DICOM Viewer and ENVI software with method of image segmentation and Region of Interest (ROI). Brain images were randomly selected. The result of research showed that Time Repetition (TR) and Time Echo (TE) values in all types of images were not influenced by age. T2 FLAIR images had longer TR value (9000 ms), meanwhile T2 PROPELLER images had longer TE value (100.75 - 102.1 ms). Furthermore, areas with low and medium signal intensity appeared clearer by using T2 PROPELLER images (average coefficients of variation for low and medium signal intensity were 0.0431 and 0.0705, respectively). As for areas with high signal intensity appeared clearer by using T2 FLAIR images (average coefficient of variation was 0.0637).
Energy Technology Data Exchange (ETDEWEB)
Min, Soo Hyun; Kim, Soo Youn; Lee, Ghi Jai; Shim, Jae Chan; Oh, Tae Kyung; Kim, Ho Kyun [College of Medicine, Jnje University, Seoul (Korea, Republic of)
2000-03-01
To compare the findings of fluid-attenuated inversion recovery (FLAIR) MR imaging in the detection of subarachnoid hemorrhage (SAH), with those of precontrast CT and T1-weighted MR imaging. In 13 patients (14 cases) with SAH, FLAIR MR images were retrospectively analyzed and compared with CT (10 patients, 11 cases) and T1-weighted MR images (9 cases). SAH was confirmed on the basis of high density along the subarachnoid space, as seen on precontrast CT, or lumbar puncture. MR imaging was performed on a 1.0T unit. FLAIR MR and CT images were obtained during the acute stage(less than 3 days after ictus) in 10 and 9 cases, respectively, during the subacute stage (4-14 days after ictus) in two cases and one, respectively, and during the chronic stage (more than 15 days after ictus) in two cases and one, respectively. CT was performed before FLAIR MR imaging, and the interval between CT and FLAIR ranged from 24 hours (6 cases) to 2-3 (2 cases) or 4-7 days (3 cases). In each study, the conspicuity of visualization of SAH was graded as excellent, good, fair, or negative at five locations (sylvian fissure, cortical sulci, anterior basal cistern, posterior basal cistern, and perimesencephalic cistern). In all cases, subarachnoid hemorrhages were demonstrated as high signal intensity areas on FLAIR images. The detection rates for SAH on CT and T1-weighted MR images were 100% (11/11) and 89% (8/9), respectively. FLAIR was superior to T1-weighted imaging in the detection of SAH at all sites except the anterior basal cistern (p less than 0.05) and superior to CT in the detection of SAH at the cortical sulci (p less than 0.05). On FLAIR MR images, subarachnoid hemorrhages at all stages are demonstrated as high signal intensity areas; the FLAIR MR sequence is thus considered useful in the detection of SAH. In particular FLAIR is more sensitive than CT for the detection of SAH in the cortical sulci. (author)
International Nuclear Information System (INIS)
Carrete Junior, Henrique; Abdala, Nitamar; Szjenfeld, Jacob; Nogueira, Roberto Gomes; Lin, Katia; Caboclo, Luis Otavio; Centeno, Ricardo Silva; Sakamoto, Americo Ceiki; Yacubian, Elza Marcia Targas
2007-01-01
Objective: To determine the frequency and regional involvement of temporal pole signal abnormality (TPA) in patients with hippocampal sclerosis (HS) using fluid-attenuated inversion-recovery (FLAIR) MR imaging, and to correlate this feature with history. Method: Coronal FLAIR images of the temporal pole were assessed in 120 patients with HS and in 30 normal subjects, to evaluate gray-white matter demarcation. Results: Ninety (75%) of 120 patients had associated TPA. The HS side made difference regarding the presence of TPA, with a left side prevalence (p=0.04, χ 2 test). The anteromedial zone of temporal pole was affected in 27 (30%) out of 90 patients. In 63 (70%) patients the lateral zone were also affected. Patients with TPA were younger at seizure onset (p=0.018), but without association with duration of epilepsy. Conclusion: Our FLAIR study show temporal pole signal abnormality in 3/4 of patients with HS, mainly seen on the anteromedial region, with a larger prevalence when the left hippocampus was involved. (author)
Carrete, Henrique; Abdala, Nitamar; Lin, Kátia; Caboclo, Luís Otávio; Centeno, Ricardo Silva; Sakamoto, Américo Ceiki; Szjenfeld, Jacob; Nogueira, Roberto Gomes; Yacubian, Elza Márcia Targas
2007-09-01
To determine the frequency and regional involvement of temporal pole signal abnormality (TPA) in patients with hippocampal sclerosis (HS) using fluid-attenuated inversion-recovery (FLAIR) MR imaging, and to correlate this feature with history. Coronal FLAIR images of the temporal pole were assessed in 120 patients with HS and in 30 normal subjects, to evaluate gray-white matter demarcation. Ninety (75%) of 120 patients had associated TPA. The HS side made difference regarding the presence of TPA, with a left side prevalence (p=0.04, chi2 test). The anteromedial zone of temporal pole was affected in 27 (30%) out of 90 patients. In 63 (70%) patients the lateral zone were also affected. Patients with TPA were younger at seizure onset (p=0.018), but without association with duration of epilepsy. Our FLAIR study show temporal pole signal abnormality in 3/4 of patients with HS, mainly seen on the anteromedial region, with a larger prevalence when the left hippocampus was involved.
International Nuclear Information System (INIS)
Oppenheim, C.; Dormont, D.; Lehericy, S.; Marsault, C.; Hasboun, D.; Bazin, B.; Samson, S.; Baulac, M.
1999-01-01
We report a retrospective analysis of MRI in 206 patients with intractable seizures and describe the findings in bilateral mesial temporal sclerosis (MTS) on fast spin-echo (FSE) and fast fluid-attenuated inversion-recovery (fFLAIR) sequences. Criteria for MTS were atrophy, signal change and loss of the digitations of the head of the hippocampus. In patients with bilateral MRI signs of MTS, correlation with clinical electro, volumetric MRI data and neuropsychological tests, when available, was performed. Bilateral MTS was observed in seven patients. Bilateral loss of the digitations and signal change of fFLAIR was seen in all seven. In three, bilateral atrophy was obvious. In two patients, mild bilateral atrophy was observed and in two others, the hippocampi were: asymmetrical, with obvious atrophy on only one side. Volumetric data confirmed bilateral symmetrical atrophy in five patients, and volumes were at the lowest of the normal range in other two. The EEG showed temporal abnormalities in all patients, unilateral in five and bilateral in two. All patients had memory impairment and neuropsychological data confirmed visual and verbal memory deficits; two patients failed the Wada test on both sides. High-resolution T2-weighted FSE and fFLAIR sequences allow diagnosis of bilateral MTS, which has important therapeutic and prognostic implications. (orig.)
International Nuclear Information System (INIS)
Erdem, L. Oktay; Erdem, C. Zuhal; Acikgoz, Bektas; Gundogdu, Sadi
2005-01-01
Objective: To compare fast T1-weighted fluid-attenuated inversion recovery (FLAIR) and T1-weighted turbo spin-echo (TSE) imaging of the degenerative disc disease of the lumbar spine. Materials and methods: Thirty-five consecutive patients (19 females, 16 males; mean age 41 years, range 31-67 years) with suspected degenerative disc disease of the lumbar spine were prospectively evaluated. Sagittal images of the lumbar spine were obtained using T1-weighted TSE and fast T1-weighted FLAIR sequences. Two radiologists compared these sequences both qualitatively and quantitatively. Results: On qualitative evaluation, CSF nulling, contrast at the disc-CSF interface, the disc-spinal cord (cauda equina) interface, and the spinal cord (cauda equina)-CSF interface of fast T1-weighted FLAIR images were significantly higher than those for T1-weighted TSE images (P < 0.001). On quantitative evaluation of the first 15 patients, signal-to-noise ratios of cerebrospinal fluid of fast T1-weighted FLAIR imaging were significantly lower than those for T1-weighted TSE images (P < 0.05). Contrast-to-noise ratios of spinal cord/CSF and normal bone marrow/disc for fast T1-weighted FLAIR images were significantly higher than those for T1-weighted TSE images (P < 0.05). Conclusion: Results in our study have shown that fast T1-weighted FLAIR imaging may be a valuable imaging modality in the armamentarium of lumbar spinal T1-weighted MR imaging, because the former technique has definite superior advantages such as CSF nulling, conspicuousness of the normal anatomic structures and changes in the lumbar spinal discogenic disease and image contrast and also almost equally acquisition times
Inverse regression for ridge recovery I: Theory
Glaws, Andrew T.; Constantine, Paul G.; Cook, R. Dennis
2017-01-01
We investigate the application of sufficient dimension reduction (SDR) to a deterministic function of several variables. In this context, SDR provides a framework for ridge recovery. A ridge function is a function of a few linear combinations of the variables---i.e., a composition of a nonlinear function with a low-dimensional linear transformation. We connect the key feature of SDR---the dimension reduction subspace---to ridge structure in functions, which provides a subspace-based perspecti...
International Nuclear Information System (INIS)
Moon, Won Jin; Roh, Hong Gee; Choi, Jin Woo; Kim, Hee Jin; Han, Seol Heui
2012-01-01
We hypothesized that prominent pulvinar hypointensity in brain MRI represents the disease process due to iron accumulation in Alzheimer disease (AD). We aimed to determine whether or not the pulvinar signal intensity (SI) on the fluid-attenuated inversion recovery (FLAIR) sequences at 3.0T MRI differs between AD patients and normal subjects, and also whether the pulvinar SI is correlated with the T2 map, an imaging marker for tissue iron, and a cognitive scale. Twenty one consecutive patients with AD and 21 age-matched control subjects were prospectively included in this study. The pulvinar SI was assessed on the FLAIR image. We measured the relative SI ratio of the pulvinar to the corpus callosum. The T2 values were calculated from the T2 relaxometry map. The differences between the two groups were analyzed, by using a Student t test. The correlation between the measurements was assessed by the Pearson's correlation test. As compared to the normal white matter, the FLAIR signal intensity of the pulvinar nucleus was significantly more hypointense in the AD patients than in the control subjects (p < 0.01). The pulvinar T2 was shorter in the AD patients than in the control subjects (51.5 ± 4.95 ms vs. 56.5 ± 5.49 ms, respectively, p = 0.003). The pulvinar SI ratio was strongly correlated with the pulvinar T2 (r = 0.745, p < 0.001). When controlling for age, only the pulvinar-to-CC SI ratio was positively correlated with that of the Mini-Mental State Examination (MMSE) score (r = 0.303, p < 0.050). Conversely, the pulvinar T2 was not correlated with the MMSE score (r = 0.277, p = 0.080). The FLAIR hypointensity of the pulvinar nucleus represents an abnormal iron accumulation in AD and may be used as an adjunctive finding for evaluating AD.
Maturation of the limbic system revealed by MR FLAIR imaging
Energy Technology Data Exchange (ETDEWEB)
Schneider, Jacques F.; Vergesslich, Klara [University Children' s Hospital UKBB, Department of Paediatric Radiology, Basel (Switzerland)
2007-04-15
Cortical signal intensity (SI) of the limbic system in adults is known to be higher than in neocortical structures, but time-related changes in SI during childhood have not been described. To detect maturation-related SI changes within the limbic system using a fluid-attenuated inversion recovery (FLAIR) MR sequence. Twenty children (10 boys, 10 girls; age 3.5-18 years, mean 11.2 years) with no neurological abnormality and normal MR imaging examination were retrospectively selected. On two coronal FLAIR slices, ten regions of interest (ROI) with a constant area of 10 mm{sup 2} were manually placed in the archeocortex (hippocampus), periarcheocortex (parahippocampal gyrus, subcallosal area, cingulate gyrus) and in the neocortex at the level of the superior frontal gyrus on both sides. Significant SI gradients were observed with a higher intensity in the archeocortex, intermediate intensity in the periarcheocortex and low intensity in the neocortex. Significant higher SI values in hippocampal and parahippocampal structures were detected in children up to 10 years of age. These differences mainly reflected differences in cortical structure and myelination state. Archeocortical structures especially showed significant age-related intensity progression suggesting ongoing organization and/or myelination until early adolescence. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Im, SungWoon; Ashikaga, Ryuichiro; Yagyu, Yukinobu; Hyodo, Tomoko; Imaoka, Izumi; Kumano, Seishi; Ishii, Kazunari; Murakami, Takamichi [Kinki University Faculty of Medicine, Department of Radiology, Osaka-Sayama, Osaka (Japan); Wakayama, Tetsuya; Miyoshi, Mitsuharu [GE Healthcare Japan, MR Applications and Workflow, Asia Pacific, Hino, Tokyo (Japan)
2015-11-15
The purpose of this study was to investigate the usefulness of T1W black-blood Cube (BB Cube) and T1W BB Cube fluid-attenuated inversion recovery (BB Cube-FLAIR) sequences for contrast-enhanced brain imaging, by evaluating flow-related artefacts, detectability, and contrast ratio (CR) of intracranial lesions among these sequences and T1W-SE. Phantom studies were performed to determine the optimal parameters of BB Cube and BB Cube-FLAIR. A clinical study in 23 patients with intracranial lesions was performed to evaluate the usefulness of these two sequences for the diagnosis of intracranial lesions compared with the conventional 2D T1W-SE sequence. The phantom study revealed that the optimal parameters for contrast-enhanced T1W imaging were TR/TE = 500 ms/minimum in BB Cube and TR/TE/TI = 600 ms/minimum/300 ms in BB Cube-FLAIR imaging. In the clinical study, the degree of flow-related artefacts was significantly lower in BB Cube and BB Cube-FLAIR than in T1W-SE. Regarding tumour detection, BB Cube showed the best detectability; however, there were no significant differences in CR among the sequences. At 1.5 T, contrast-enhanced BB Cube was a better imaging sequence for detecting brain lesions than T1W-SE or BB Cube-FLAIR. (orig.)
Ivy signs on FLAIR images before and after STA-MCA anastomosis in patients with Moyamoya disease
International Nuclear Information System (INIS)
Ideguchi, Reiko; Enokizono, Mikako; Uetani, Masataka; Morikawa, Minoru; Ogawa, Yoji; Nagata, Izumi
2011-01-01
Background: Leptomeningeal high signal intensity (ivy sign) on fluid-attenuated inversion-recovery (FLAIR) MR imaging is one of the features of Moyamoya disease. However, the correlation between ivy sign and cerebral perfusion status has not been fully evaluated. Purpose: To characterize ivy sign on FLAIR images in Moyamoya disease and compare this finding with hemodynamic alterations on perfusion single-photon emission CT (SPECT) obtained before and after bypass surgery. Material and Methods: Sixteen patients with angiographically confirmed Moyamoya disease who underwent superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis were included in the study. The presence of ivy sign on FLAIR images was classified as 'negative', 'minimal' and 'positive'. We evaluated the relationship between ivy sign and findings of SPECT, including cerebral vascular reserve (CVR) before and after surgery. Results: Minimal or positive ivy sign was seen in 13 (81%) of 16 patients, and 21 (66%) of 32 hemispheres. CVR in the areas with positive or minimal ivy sign was lower than that in the areas with negative ivy sign. After STA-MCA anastomosis, ivy sign disappeared or decreased in all 21 hemispheres demonstrating ivy sign. SPECT demonstrated apparent hemodynamic improvement in areas demonstrating disappearance or decrease of ivy sign. Conclusion: Ivy sign on FLAIR image is seen in areas with decreased cerebral perfusion. The sign is useful for non-invasive assessment of cerebral hemodynamic status before and after surgery
International Nuclear Information System (INIS)
Bozzao, Alessandro; Floris, Roberto; Fasoli, Fabrizio; Simonetti, Giovanni; Fantozzi, Luigi Maria; Colonnese, Claudio
2003-01-01
Fluid-attenuated inversion recovery (FLAIR) sequence is currently used in clinical practice. Some reports emphasize the possibility that, in pathologic conditions, intravenous injection of gadolinium chelates may lead to an increased signal inside the cerebrospinal fluid (CSF). The aim of this study was to evaluate the presence of CSF signal changes in pathologic conditions causing blood-brain barrier disruption or neovascularization when imaging is performed after intravenous injection of gadolinium. We obtained FLAIR sequences after gadolinium injection from 33 patients affected by different intracranial pathologies and 10 control subjects. Patients were affected by ischemic stroke in the subacute phase, from 2 to 7 days from onset of symptoms (12 patients), meningiomas (8 patients), high-grade gliomas (5 patients), previous surgical procedures for intra-axial neoplasms (5 patients), and multiple sclerosis with active plaques (3 patients). Magnetic resonance imaging was performed in patients and controls using a 1.5-T magnet, using T2- and T1-weighted FLAIR sequences. The FLAIR sequence was acquired before and 1-3 h after injection of a standard dose of gadolinium. In those patients affected by ischemic lesions, FLAIR sequences were repeated the next days and 3-4 days later. The CSF signal was visually evaluated by two readers and scored from 0 to 3 depending by the degree of enhancement. The location of CSF signal changes (close to the lesion, hemispheric, or diffuse) was also considered. The CSF signal was markedly increased after 3 h from intravenous injection of gadolinium in all the patients with stroke, in those with previous surgery, and in those with high-grade gliomas whose neoplasm's surface was in contact with the subarachnoid spaces (SAS) or ventricles; a strong enhancement was also evident inside the necrotic component of the tumor. The CSF changes were more evident close to the pathology and/or in the hemisphere involved by the pathology. Moderate
Directory of Open Access Journals (Sweden)
Juliana Avila Duarte
2016-08-01
Full Text Available A 61-year-old woman arrived at the emergency department of the Hospital Nossa Senhora das Graças, Canoas, southern Brazil, with suspected ischemic stroke. After clinical and laboratory examination, the clinical diagnosis of ischemic stroke was made, without fulfilling criteria for thrombolysis. The patient had no history of renal failure. Three days later, she performed a magnetic resonance imaging (MRI examination that confirmed the suspected diagnosis. This examination was performed without sedation or supplemental oxygen. Brain MRI was performed after gadolinium injection, using fluid-attenuated inversion recovery (FLAIR imaging, T1-weighted image, diffusion-weighted imaging, and T2-weighted image sequences that revealed signs of subacute watershed stroke in the left cerebral hemisphere (Figures 1, 2 and 3. There was a hyperintense cerebrospinal fluid (CSF in the subarachnoid space (SAS on FLAIR imaging, a finding that has been reported in many pathologic conditions1 such as superior sagittal thrombosis, subarachnoid hemorrhage², meningitis, meningeal carcinomatosis, next to tumors, status epilepticus and stroke.3-7 It has also been reported in otherwise healthy patients undergoing anesthesia with supplemental oxygen.8 The exact mechanism by which CSF diffuses into the SAS in patients with or without renal insufficiency is not completely explained. Some authores have suggested that in patients with renal failure, the gadolinium may shift across an osmotic gradient at the circumventricular organs in the setting of proctracted elevation of plasma concentrations.9 We believe that the cause of this imaging phenomenon of hyperintense signal of the CSF in the SAS which has already been noted in patients with compromised cerebral perfusion, including cases of acute ischemic stroke, was due to the recent stroke.10-11 Keywords: Flair hyperintensity, MRI, stroke, Gadolinium
Spinal cord imaging using averaged magnetization inversion recovery acquisitions.
Weigel, Matthias; Bieri, Oliver
2018-04-01
To establish a novel approach for fast high-resolution spinal cord (SC) imaging using averaged magnetization inversion recovery acquisitions (AMIRA). The AMIRA concept is based on an inversion recovery (IR) prepared, segmented, and time-limited cine balanced steady state free precession sequence. Typically, for the fastest SC imaging without any signal averaging, eight consecutive images in time with an in-plane resolution of 0.67 × 0.67 mm 2 and 6 mm to 8 mm slice thickness are acquired in 51 s. AMIRA does not require parallel acquisition techniques. AMIRA measures eight images of remarkable tissue contrast variation between spinal cord gray (GM) and white matter (WM) and cerebrospinal fluid (CSF). Following the AMIRA concept, averaging the first IR contrast images not only improves the signal-to-noise ratio but also offers a surprising enhancement of the contrast-to-noise ratio between GM and WM, whereas averaging the last images considerably improves the contrast-to-noise ratio between WM and CSF. These observations are supported by quantitative data. The AMIRA concept provides 2D spinal cord imaging with multiple tissue contrasts and enhanced contrast-to-noise ratios with a typical 0.67 × 0.67 mm 2 in-plane resolution and a slice thickness between 4 mm and 8 mm acquired in only 1 to 2 min per slice. Magn Reson Med 79:1870-1881, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.
International Nuclear Information System (INIS)
Sener, R.N.
2000-01-01
A patient is reported with diffuse leukoencephalopathy associated with cystic degeneration of the white matter of the brain (van der Knaap syndrome). The changes were studied by fluid attenuated inversion recovery (FLAIR), and diffusion-weighted MR imaging. The FLAIR sequence revealed suppressed signal of the cysts, and widespread high-signal white matter changes associated with thinned cortices. On diffusion-weighted MR imaging, apparent diffusion coefficient (ADC) values ranged from 3.0 x 10 -3 to 2.7 x 10 -3 mm 2 /s in the temporal cysts, similar to that of CSF. The ADC values within the parenchyma ranged between 2 x 10 -3 and 2.1 x 10 -3 mm 2 /s, a value falling between normal parenchyma and cerebrospinal fluid, compared with a control group of three healthy subjects. The changes were also evaluated by proton MR spectroscopy, and were compared with a control group of 12 cases. Magnetic resonance spectroscopy revealed apparently increased NAA/Cr ratios in most parts of the brain. The NAA/Cho ratios were either high or low, and the Cho/Cr ratios were increased or normal in different regions. (orig.)
International Nuclear Information System (INIS)
Liu Wenhua; Yin Qin; Yao Lingling; Zhu Shuanggen; Xu Gelin; Zhang Renliang; Ke Kaifu; Liu Xinfeng
2012-01-01
Background and purpose: Hyperintense vessels (HV) on fluid-attenuated inversion recovery (FLAIR) images were assumed to be explained by slow antegrade or retrograde leptomeningeal collateral flow related to extracranial or intracranial artery steno-occlusion. The aim of this study was to investigate the effect of recanalization after endovascular therapy of symptomatic internal carotid artery (ICA) occlusion on the presence of HV. Methods: Eleven patients with symptomatic ICA occlusion were retrospectively enrolled. Changes in the HV on FLAIR images were examined in affected hemisphere of each patient after successful treatment with endovascular recanalization (angioplasty, n = 3; stent-assisted angioplasty, n = 8). The relationship between postoperative changes in the HV and Thrombolysis In Cerebral Ischemia (TICI) scale (I-III) was assessed. Results: After operation, HV of the 11 affected hemispheres were showed to be decreased (n = 3) or disappeared (n = 8) in treated side. The median interval between pre- and postoperative MRI examinations was 97.0 h (range, from 69. to 48.7 h). Of the 8 patients with disappeared HV, 7 achieved high TICI grade flow (III) and 1 had relatively low TICI grade flow (IIc) in treated side. However, all the 3 patients with decreased HV were found to be relatively low TICI grade flow (IIc). Conclusion: Our data indicate that endovascular recanalization of ICA occlusion was effective for decreasing HV. Postoperative decrease in HV can be considered as a marker for hemodynamic improvement.
Zhu, Honglei; Ou, Yongkang; Fu, Jia; Zhang, Ya; Xiong, Hao; Xu, Yaodong
2015-10-01
It has been reported that about half of patients with sudden sensorineural hearing loss (SSNHL) show high signals in the affected inner ear on three-dimensional, fluid-attenuated inversion recovery magnetic resonance imaging (3D-FLAIR MRI). These signals may reflect minor hemorrhage or an increased concentration of protein in the inner ear, which has passed through blood vessels with increased permeability. Our objective was to compare the positive ratio of the high signal in affected inner ears at different time points to determine the suitable imaging time point for 3D-FLAIR MRI in SSNHL. 3D-FLAIR MRI images were taken at three times, precontrast and approximately 10 min and 4 h after intravenous injection of a single dose of gadodiamide (Gd) (0.1 mmol/kg), in 46 patients with SNHL. We compared the positive findings of the high signals in the inner ear of patients with SNHL as well as the signal intensity ratio (SIR) between the affected cochleae and unaffected cochleae at three time points. The positive ratios of the high signals in the affected inner ear at the time points of precontrast and 10 min and 4 h after the intravenous Gd injection were 26.1, 32.6, and 41.3%, respectively. The high signal intensity ratios of affected inner ears at the three time points were 1.28, 1.31, and 1.48, respectively. The difference between the positive ratios precontrast and at 10 min after the intravenous Gd injection was statistically significant (P = 0.006); the differences between the positive ratios at 4 h after the intravenous Gd injection and precontrast and between the ratios at 4 h and 10 min after the intravenous Gd injection were not statistically significant. The time effects of the median value of SIR were not significant (P = 0.064). We do not recommend 4 h after intravenous Gd injection as a time point to image the inner ear in SNHL. We believe that imaging precontrast and at 10 min after the intravenous Gd injection are suitable time points.
Mahdjoub, E; Turc, G; Legrand, L; Benzakoun, J; Edjlali, M; Seners, P; Charron, S; Ben Hassen, W; Naggara, O; Meder, J-F; Mas, J-L; Baron, J-C; Oppenheim, C
2018-01-01
In acute ischemic stroke, whether FLAIR vascular hyperintensities represent good or poor collaterals remains controversial. We hypothesized that extensive FLAIR vascular hyperintensities correspond to good collaterals, as indirectly assessed by the hypoperfusion intensity ratio. We included 244 consecutive patients eligible for reperfusion therapy with MCA stroke and pretreatment MR imaging with both FLAIR and PWI. The FLAIR vascular hyperintensity score was based on ASPECTS, ranging from 0 (no FLAIR vascular hyperintensity) to 7 (FLAIR vascular hyperintensities abutting all ASPECTS cortical areas). The hypoperfusion intensity ratio was defined as the ratio of the time-to-maximum >10-second over time-to-maximum >6-second lesion volumes. The median hypoperfusion intensity ratio was used to dichotomize good (low hypoperfusion intensity ratio) versus poor (high hypoperfusion intensity ratio) collaterals. We then studied the association between FLAIR vascular hyperintensity extent and hypoperfusion intensity ratio. Hypoperfusion was present in all patients, with a median hypoperfusion intensity ratio of 0.35 (interquartile range, 0.19-0.48). The median FLAIR vascular hyperintensity score was 4 (interquartile range, 3-5). The FLAIR vascular hyperintensities were more extensive in patients with good collaterals (hypoperfusion intensity ratio ≤0.35) than with poor collaterals (hypoperfusion intensity ratio >0.35; P for Trend = .016). The FLAIR vascular hyperintensity score was independently associated with good collaterals ( P for Trend = .002). In patients eligible for reperfusion therapy, FLAIR vascular hyperintensity extent was associated with good collaterals, as assessed by the pretreatment hypoperfusion intensity ratio. The ASPECTS assessment of FLAIR vascular hyperintensities could be used to rapidly identify patients more likely to benefit from reperfusion therapy. © 2018 by American Journal of Neuroradiology.
Detection and characterization with short TI inversion recovery MR imaging
International Nuclear Information System (INIS)
Komata, Kaori
1994-01-01
Short TI inversion recovery magnetic resonance imaging (STIR-MRI) with spin echo (SE) T1- and T2-weighted images of the pelvis was investigated to evaluate its usefulness in detecting and characterizing endometriosis. Thirty-one women suspected of having the disease were studied in detail. MR findings with and without STIR-MRI were correlated with the results of laparotomy (27 women) and laparoscopy (4 women). Surgery revealed endometriosis in 29 women (17 ovarian chocolate cysts, 22 intestinal adhesions, 14 cul-de-sac obliterations and 12 adenomyosis). The other two women did not have endometriosis (uterine prolapse in one and submucosal leiomyoma in one). An ovarian chocolate cyst was diagnosed when a T1-elongated lesion showed shading, loculus or a low intensity rim on SE MR images, and a low intensity rim on STIR-MRI. Only 12 of the 17 chocolate cysts and neither of the two hemorrhagic corpus lutein cysts were correctly diagnosed on SE MR images, whereas 18 of these 19 cysts were correctly diagnosed because of the low intensity rim on STIR-MRI. In the pathological analysis, the rim was found to be a fibrous capsule and there were many macrophages which phagocytized hemosiderin. For the assessment of ovarian chocolate cysts, accuracy improved from 63.2% to 94.7%. As for the adhesion between the intestine and the uterus, specificity improved from 61.9% to 90.5% and accuracy improved from 67.7% to 93.5% when STRI-MRI was used. For the assessment of the cul-de-sac obliteration, accuracy improved from 67.7% to 83.8% although χ 2 analysis showed no significance. The major factors for the improved accuracy with STIR-MRI are the decrease of the motion artifact owing to the suppression of the fat signal, decreased chemical shift artifact and accurate differentiation of fat from hemorrhagic component. Therefore, STIR-MRI is a useful and reliable procedure and should be used together with SE T1-, T2-weighted images for the assessment of endometriosis. (author)
Detection and characterization with short TI inversion recovery MR imaging
Energy Technology Data Exchange (ETDEWEB)
Komata, Kaori (Nippon Medical School, Tokyo (Japan))
1994-10-01
Short TI inversion recovery magnetic resonance imaging (STIR-MRI) with spin echo (SE) T1- and T2-weighted images of the pelvis was investigated to evaluate its usefulness in detecting and characterizing endometriosis. Thirty-one women suspected of having the disease were studied in detail. MR findings with and without STIR-MRI were correlated with the results of laparotomy (27 women) and laparoscopy (4 women). Surgery revealed endometriosis in 29 women (17 ovarian chocolate cysts, 22 intestinal adhesions, 14 cul-de-sac obliterations and 12 adenomyosis). The other two women did not have endometriosis (uterine prolapse in one and submucosal leiomyoma in one). An ovarian chocolate cyst was diagnosed when a T1-elongated lesion showed shading, loculus or a low intensity rim on SE MR images, and a low intensity rim on STIR-MRI. Only 12 of the 17 chocolate cysts and neither of the two hemorrhagic corpus lutein cysts were correctly diagnosed on SE MR images, whereas 18 of these 19 cysts were correctly diagnosed because of the low intensity rim on STIR-MRI. In the pathological analysis, the rim was found to be a fibrous capsule and there were many macrophages which phagocytized hemosiderin. For the assessment of ovarian chocolate cysts, accuracy improved from 63.2% to 94.7%. As for the adhesion between the intestine and the uterus, specificity improved from 61.9% to 90.5% and accuracy improved from 67.7% to 93.5% when STRI-MRI was used. For the assessment of the cul-de-sac obliteration, accuracy improved from 67.7% to 83.8% although [chi][sup 2] analysis showed no significance. The major factors for the improved accuracy with STIR-MRI are the decrease of the motion artifact owing to the suppression of the fat signal, decreased chemical shift artifact and accurate differentiation of fat from hemorrhagic component. Therefore, STIR-MRI is a useful and reliable procedure and should be used together with SE T1-, T2-weighted images for the assessment of endometriosis. (author).
Quantitative Magnetization Transfer Imaging in Human Brain at 3 T via Selective Inversion Recovery
Dortch, Richard D.; Li, Ke; Gochberg, Daniel F.; Welch, E. Brian; Dula, Adrienne N.; Tamhane, Ashish A.; Gore, John C.; Smith, Seth A.
2011-01-01
Quantitative magnetization transfer imaging yields indices describing the interactions between free water protons and immobile, macromolecular protons—including the macromolecular to free pool size ratio (PSR) and the rate of magnetization transfer between pools kmf. This study describes the first implementation of the selective inversion recovery quantitative magnetization transfer method on a clinical 3.0-T scanner in human brain in vivo. Selective inversion recovery data were acquired at 1...
Byun, Hayoung; Chung, Jae Ho; Lee, Seung Hwan; Park, Chul Won; Park, Dong Woo; Kim, Tae Yoon
2018-01-13
To investigate the clinical significance of 4-hour delayed-enhanced 3.0 Tesla three-dimensional (3D) fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) imaging in acute vestibular neuritis. A prospective observational study. Twenty-nine vestibular neuritis patients were enrolled between January 2017 and June 2017. Vestibular function tests, comprising the caloric and video head impulse tests and vestibular-evoked myogenic potential measurements, were performed. Precontrast, 10-minute, and 4-hour delayed-enhanced 3D-FLAIR MR images using double-dose IV gadolinium were obtained. After laterality and extent of inner ear enhancement were defined, the patients were divided into groups based on the patterns of enhancement, and clinical parameters were analyzed according to the groups. Twenty patients (20 of 29, 69.0%) had obviously asymmetric enhancement of the affected inner ear structures on 4-hour delayed images, whereas only three patients (10.3%) had marked enhancement on 10-minute delayed images. The duration of spontaneous nystagmus (DurSN) was significantly longer in the patients with enhancement, especially with enhancement of the whole inner ear, including the vestibule and semicircular canals (P vestibular function tests did not reveal any significant associations with MR enhancement. Contrast enhancement of the vestibular nerve and inner ear structures can be identified on 4-hour delayed-enhanced 3T 3D-FLAIR MR images in acute vestibular neuritis. The extent of inner ear enhancement may be associated with the DurSN. IV. Laryngoscope, 2017. © 2018 The American Laryngological, Rhinological and Otological Society, Inc.
Im, SungWoon; Ashikaga, Ryuichiro; Yagyu, Yukinobu; Wakayama, Tetsuya; Miyoshi, Mitsuharu; Hyodo, Tomoko; Imaoka, Izumi; Kumano, Seishi; Ishii, Kazunari; Murakami, Takamichi
2015-11-01
The purpose of this study was to investigate the usefulness of T1W black-blood Cube (BB Cube) and T1W BB Cube fluid-attenuated inversion recovery (BB Cube-FLAIR) sequences for contrast-enhanced brain imaging, by evaluating flow-related artefacts, detectability, and contrast ratio (CR) of intracranial lesions among these sequences and T1W-SE. Phantom studies were performed to determine the optimal parameters of BB Cube and BB Cube-FLAIR. A clinical study in 23 patients with intracranial lesions was performed to evaluate the usefulness of these two sequences for the diagnosis of intracranial lesions compared with the conventional 2D T1W-SE sequence. The phantom study revealed that the optimal parameters for contrast-enhanced T1W imaging were TR/TE = 500 ms/minimum in BB Cube and TR/TE/TI = 600 ms/minimum/300 ms in BB Cube-FLAIR imaging. In the clinical study, the degree of flow-related artefacts was significantly lower in BB Cube and BB Cube-FLAIR than in T1W-SE. Regarding tumour detection, BB Cube showed the best detectability; however, there were no significant differences in CR among the sequences. At 1.5 T, contrast-enhanced BB Cube was a better imaging sequence for detecting brain lesions than T1W-SE or BB Cube-FLAIR. • Cube is a single-slab 3D FSE imaging sequence. • We applied a black-blood (BB) imaging technique to T1W Cube. • At 1.5 T, contrast-enhanced T1W BB Cube was valuable for detecting brain lesions.
Hyperintense vessels on FLAIR: A useful non-invasive method for assessing intracerebral collaterals
International Nuclear Information System (INIS)
Liu Wenhua; Xu Gelin; Yue Xuanye; Wang Xiaoliang; Ma Minmin; Zhang Renliang; Wang Handong; Zhou Changsheng; Liu Xinfeng
2011-01-01
Objective: This study was aimed to evaluate relationship between hyperintense vessels (HV) on fluid-attenuated inversion recovery (FLAIR) and artery steno-occlusion related intracerebral collaterals. Materials and methods: A total of 233 patients with 260 atherosclerotic lesions in the M1 segment of the middle cerebral artery (MCA) were examined with FLAIR and digital subtraction angiography (DSA). HV were graded as 0, 1, 2 and 3 by its distributions in the MCA territory. Grade 0 indicated no HV; Grade 1 indicated the HV limited in Sylvian fissure; Grade 2 indicated the HV limited in Sylvian fissure and the temporal-occipital junction; Grade 3 indicated the HV extended to frontal-parietal lobes. Collateral blood flows were classified by DSA results. The relationship between HV grades and patterns of collateral flows was analyzed. Results: HV were observed in 76 out of 260 hemispheres. For patients with Grade 1 HV, most of their collateral flows (80.8%) were antegrade; for patients with Grade 2, the retrograde leptomeningeal flows were commonly manifested as anterior cerebral artery to MCA (75%); for patients with Grade 3 HV, most of the retrograde leptomeningeal flows were manifested as posterior cerebral artery to MCA (81.8%). As the grade HV increased, the frequency of retrograde leptomeningeal collateral from ACA to MCA decreased (100% to 75% and to 18.2%), and increased (0% to 25% and to 81.8%) for the retrograde leptomeningeal collateral via PCA to MCA (P < 0.001). Conclusions: The HV could assess non-invasively intracerebral collaterals in patients with steno-occlusive lesions of M1 segment of MCA.
Hill, Jason E.; Matlock, Kevin; Pal, Ranadip; Nutter, Brian; Mitra, Sunanda
2016-03-01
Magnetic Resonance Imaging (MRI) is a vital tool in the diagnosis and characterization of multiple sclerosis (MS). MS lesions can be imaged with relatively high contrast using either Fluid Attenuated Inversion Recovery (FLAIR) or Double Inversion Recovery (DIR). Automated segmentation and accurate tracking of MS lesions from MRI remains a challenging problem. Here, an information theoretic approach to cluster the voxels in pseudo-colorized multispectral MR data (FLAIR, DIR, T2-weighted) is utilized to automatically segment MS lesions of various sizes and noise levels. The Improved Jump Method (IJM) clustering, assisted by edge suppression, is applied to the segmentation of white matter (WM), gray matter (GM), cerebrospinal fluid (CSF) and MS lesions, if present, into a subset of slices determined to be the best MS lesion candidates via Otsu's method. From this preliminary clustering, the modal data values for the tissues can be determined. A Euclidean distance is then used to estimate the fuzzy memberships of each brain voxel for all tissue types and their 50/50 partial volumes. From these estimates, binary discrete and fuzzy MS lesion masks are constructed. Validation is provided by using three synthetic MS lesions brains (mild, moderate and severe) with labeled ground truths. The MS lesions of mild, moderate and severe designations were detected with a sensitivity of 83.2%, and 88.5%, and 94.5%, and with the corresponding Dice similarity coefficient (DSC) of 0.7098, 0.8739, and 0.8266, respectively. The effect of MRI noise is also examined by simulated noise and the application of a bilateral filter in preprocessing.
Consensus recommendations for MS cortical lesion scoring using double inversion recovery MRI
DEFF Research Database (Denmark)
Geurts, J J G; Roosendaal, S D; Calabrese, M
2011-01-01
Different double inversion recovery (DIR) sequences are currently used in multiple sclerosis (MS) research centers to visualize cortical lesions, making it difficult to compare published data. This study aimed to formulate consensus recommendations for scoring cortical lesions in patients with MS...
Energy Technology Data Exchange (ETDEWEB)
Lee, Eun Kyoung; Lee, Eun Ja; Kim, Sung Won; Lee, Yong Seok [Dept. of Radiology, Dongguk University Ilsan Hospital, Goyang(Korea, Republic of)
2016-02-15
Intracranial lesions may show contrast enhancement through various mechanisms that are closely associated with the disease process. The preferred magnetic resonance sequence in contrast imaging is T1-weighted imaging (T1WI) at most institutions. However, lesion enhancement is occasionally inconspicuous on T1WI. Although fluid-attenuated inversion recovery (FLAIR) sequences are commonly considered as T2-weighted imaging with dark cerebrospinal fluid, they also show mild T1-weighted contrast, which is responsible for the contrast enhancement. For several years, FLAIR imaging has been successfully incorporated as a routine sequence at our institution for contrast-enhanced (CE) brain imaging in detecting various intracranial diseases. In this pictorial essay, we describe and illustrate the diagnostic importance of CE-FLAIR imaging in various intracranial pathologic conditions.
Wang, Feng; Lyu, Huiying; Zhao, Menglong; Sha, Yan; Zhang, Fang; Cheng, Yushu; Huang, Wenhu; Tang, Wenlin; Xie, Youzhou; Lu, Ping
2017-04-01
We assessed whether the three-dimensional fluid-attenuated inversion-recovery (3-D FLAIR) and three-dimensional inversion-recovery with real reconstruction (3-D real IR) sequences can be used to detect cochlea endolymphatic hydrops (EHs) in guinea pigs using 3 Tesla magnetic resonance imaging (3T MRI). The results of 3-D real IR imaging were compared with histopathological outcomes. Fourteen healthy men and women albino guinea pigs were used in this study. Their right ears received procedures that promoted EHs, and their left ears were used as untreated controls. High-resolution 3T MRI, combined with the intratympanic injection of gadolinium (Gd) in both ears, was performed 8 to 12 weeks after surgery. Both sides of the cochlea midmodiolar sections were observed under a light microscope and saved as the histopathological images. The signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) between the T2-weighted 3-D FLAIR and T2-weighted 3-D real IR sequences were compared. The appearance of EHs in the basal, second, third, and apical turns of the cochlea was further evaluated using 3-D FLAIR, 3-D real IR, and the histopathological images. Moreover, the maximum scala media area ratios (SMRs) on the histopathological sections were compared with the grading of the EHs on the 3-D real IR sequence with regard to each turn of the cochlea. Significant differences were found between the 3-D FLAIR and 3-D-real IR sequences with regard to the SNRs and CNRs (p IR sequence (SNRROI: 86.71 ± 30.11; SNRB: 11.11 ± 3.45), whereas the 3-D real IR sequence showed higher CNRs (2.78 ± 0.58) compared with the 3-D FLAIR sequence (2.18 ± 0.55). Various degrees of EHs were observed in each turn of the cochlea in the experimental ears on the basis of the histopathological images. Thirteen, 10, 4, and 0 EHs were observed in the basal, second, third, and apical turns of the cochlear using 3-D FLAIR images, respectively, whereas 14, 14, 14, and 13 EHs were
Amano, Yasuo; Tajika, Kenji; Uchiyama, Nachiko; Takahama, Katsuya; Dan, Kazuo; Kumazaki, Tatsuo
2003-04-01
The purpose of this study was to assess the usefulness of three-station black-blood fast short-inversion time inversion recovery (STIR) imaging in detecting and staging malignant lymphoma. Seventeen patients with malignant lymphoma were examined with a 1.5T imager. The findings and stagings determined with three-station black-blood fast STIR imaging were compared with reference standards (e.g., computed tomography [CT] findings and clinical stagings). Three-station black-blood fast STIR imaging provided a fat-suppressed T2-weighted imaging contrast with fewer flow artifacts and revealed nodal involvement as well as bone marrow and spleen involvement to an extent comparable with CT. Especially notable was the excellent specificity (94%) of this imaging technique. Regarding disease staging, significant agreement was observed between clinical staging (k=0.60) and staging as evaluated by three-station black-blood fast STIR, although the detection of lymphadenopathy in the thorax was relatively poor. The average time required for this imaging was approximately 30 min. Three-station black-blood fast STIR MR imaging may be useful as a staging tool for malignant lymphoma because this imaging technique reveals lymphoma lesions, which determine the staging, without radiation exposure or the use of contrast agents.
MRI of the brain stem using fluid attenuated inversion recivery pulse sequences
International Nuclear Information System (INIS)
De Coene, B.; Hajnal, J.V.; Pennock, J.M.; Bydder, G.M.
1993-01-01
Heavily T2-weighted fluid-attenuated inversion recovery (FLAIR) sequences with inversion times of 2000-2500 ms and echo times of 130-200 ms were used to image the brain stem of a normal adult and five patients. These sequences produce high signal from many white matter tracts and display high lesion contrast. The corticospinal and parietopontine tracts, lateral and medial lemnisci, superior and inferior cerebellar peduncles, medial longitudinal fasciculi, thalamo-olivary tracts the cuneate and gracile fasiculi gave high signal and were directly visualised. The oculomotor and trigeminal nerves were demonstrated within the brain stem. Lesions not seen with conventional T2-weighted spin echo sequences were seen with high contrast in patients with infarction, multiple sclerosis, sarcoidosis, chunt obstruction and metastatic tumour. The anatomical detail and high lesion contrast given by the FLAIR pulse sequence appear likely to be of value in diagnosis of disease in the brain stem. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Varga-Szemes, Akos; Schoepf, U.J.; De Cecco, Carlo N.; Fuller, Stephen R.; Suranyi, Pal [Medical University of South Carolina, Division of Cardiovascular Imaging, Department of Radiology and Radiological Science, Charleston, SC (United States); Geest, Rob J. van der [Leiden University Medical Center, Department of Radiology, Leiden (Netherlands); Spottiswoode, Bruce S. [Siemens Medical Solutions, Chicago, IL (United States); Muscogiuri, Giuseppe [Medical University of South Carolina, Division of Cardiovascular Imaging, Department of Radiology and Radiological Science, Charleston, SC (United States); Bambino Gesu Children' s Hospital IRCCS, Department of Imaging, Rome (Italy); Wichmann, Julian L. [Medical University of South Carolina, Division of Cardiovascular Imaging, Department of Radiology and Radiological Science, Charleston, SC (United States); University Hospital Frankfurt, Department of Diagnostic and Interventional Radiology, Frankfurt (Germany); Mangold, Stefanie [Medical University of South Carolina, Division of Cardiovascular Imaging, Department of Radiology and Radiological Science, Charleston, SC (United States); Eberhard-Karls University Tuebingen, Department of Diagnostic and Interventional Radiology, Tuebingen (Germany); Maurovich-Horvat, Pal; Merkely, Bela [Semmelweis University, MTA-SE Cardiovascular Imaging Research Group, Heart and Vascular Center, Budapest (Hungary); Litwin, Sheldon E. [Medical University of South Carolina, Division of Cardiology, Department of Medicine, Charleston, SC (United States); Vliegenthart, Rozemarijn [Medical University of South Carolina, Division of Cardiovascular Imaging, Department of Radiology and Radiological Science, Charleston, SC (United States); University of Groningen, University Medical Center Groningen, Center for Medical Imaging-North East Netherlands, Department of Radiology, Groningen (Netherlands)
2017-08-15
To evaluate the influence of inversion time (TI) on the precision of myocardial late gadolinium enhancement (LGE) quantification using synthetic inversion recovery (IR) imaging in patients with myocardial infarction (MI). Fifty-three patients with suspected prior MI underwent 1.5-T cardiac MRI with conventional magnitude (MagIR) and phase-sensitive IR (PSIR) LGE imaging and T1 mapping at 15 min post-contrast. T1-based synthetic MagIR and PSIR images were calculated with a TI ranging from -100 to +150 ms at 5-ms intervals relative to the optimal TI (TI{sub 0}). LGE was quantified using a five standard deviation (5SD) and full width at half-maximum (FWHM) thresholds. Measurements were compared using one-way analysis of variance. The MagIR{sub sy} technique provided precise assessment of LGE area at TIs ≥ TI{sub 0}, while precision was decreased below TI{sub 0}. The LGE area showed significant differences at ≤ -25 ms compared to TI{sub 0} using 5SD (P < 0.001) and at ≤ -65 ms using the FWHM approach (P < 0.001). LGE measurements did not show significant difference over the analysed TI range in the PSIR{sub sy} images using either of the quantification methods. T1 map-based PSIR{sub sy} images provide precise quantification of MI independent of TI at the investigated time point post-contrast. MagIR{sub sy}-based MI quantification is precise at TI{sub 0} and at longer TIs while showing decreased precision at TI values below TI{sub 0}. (orig.)
Comparison of 3D cube FLAIR with 2D FLAIR for multiple sclerosis imaging at 3 tesla
Energy Technology Data Exchange (ETDEWEB)
Patzig, M.; Brueckmann, H.; Fesl, G. [Muenchen Univ. (Germany). Dept. of Neuroradiology; Burke, M. [GE Healthcare, Solingen (Germany)
2014-05-15
Purpose: Three-dimensional (3 D) MRI sequences allow improved spatial resolution with good signal and contrast properties as well as multiplanar reconstruction. We sought to compare Cube, a 3 D FLAIR sequence, to a standard 2 D FLAIR sequence in multiple sclerosis (MS) imaging. Materials and Methods: Examinations were performed in the clinical routine on a 3.0 Tesla scanner. 12 patients with definite MS were included. Lesions with MS-typical properties on the images of Cube FLAIR and 2 D FLAIR sequences were counted and allocated to different brain regions. Signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were calculated. Results: With 384 the overall number of lesions found with Cube FLAIR was significantly higher than with 2 D FLAIR (N = 221). The difference was mostly accounted for by supratentorial lesions (N = 372 vs. N = 216) while the infratentorial lesion counts were low in both sequences. SNRs and CNRs were significantly higher in CUBE FLAIR with the exception of the CNR of lesion to gray matter, which was not significantly different. Conclusion: Cube FLAIR showed a higher sensitivity for MS lesions compared to a 2 D FLAIR sequence. 3 D FLAIR might replace 2 D FLAIR sequences in MS imaging in the future. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Hamcan, Salih; Battal, Bilal; Akgun, Veysel; Sari, Sebahattin; Tasar, Mustafa [Gulhane Military Medical School, Department of Radiology, Etlik, Ankara (Turkey); Oz, Oguzhan; Tasdemir, Serdar [Gulhane Military Medical School, Department of Neurology, Ankara (Turkey); Bozkurt, Yalcin [Golcuk Military Hospital, Department of Radiology, Kocaeli (Turkey)
2017-02-15
To assess the usefulness of the visual assessment and to determine diagnostic value of the lesion-to-cerebral cortex signal ratio (LCSR) measurement in the differentiation of demyelinating plaques and non-specific T2 hyperintensities on double inversion recovery (DIR) sequence. DIR and fluid-attenuated inversion recovery (FLAIR) sequences of 25 clinically diagnosed multiple sclerosis (MS) patients and 25 non-MS patients with non-specific T2-hyperintense lesions were evaluated visually and LCSRs were measured by two observers independently. On DIR sequence, the calculated mean LCSR ± SD for demyelinating plaques and non-specific T2-hyperintense lesions were 1.60 ± 0.26 and 0.75 ± 0.19 for observer1, and 1.61 ± 0.27 and 0.74 ± 0.19 for observer2. LCSRs of demyelinating plaques were significantly higher than other non-specific T2-hyperintense lesions on DIR sequence. By using the visual assessment demyelinating plaques were differentiated from non-specific T2-hyperintensities with 92.8 % sensitivity, 97.5 % specificity and 95.1 % accuracy for observer1 and 92.8 % sensitivity, 95 % specificity and 93.9 % accuracy for observer2. Visual assessment and LCSR measurement on DIR sequence seems to be useful for differentiating demyelinating MS plaques from supratentorial non-specific T2 hyperintensities. This feature can be used for diagnosis of MS particularly in patients with only supratentorial T2-hyperintense lesions who are categorized as radiologically possible MS. (orig.)
Dortch, Richard D; Bagnato, Francesca; Gochberg, Daniel F; Gore, John C; Smith, Seth A
2018-03-24
To optimize a selective inversion recovery (SIR) sequence for macromolecular content mapping in the human brain at 3.0T. SIR is a quantitative method for measuring magnetization transfer (qMT) that uses a low-power, on-resonance inversion pulse. This results in a biexponential recovery of free water signal that can be sampled at various inversion/predelay times (t I/ t D ) to estimate a subset of qMT parameters, including the macromolecular-to-free pool-size-ratio (PSR), the R 1 of free water (R 1f ), and the rate of MT exchange (k mf ). The adoption of SIR has been limited by long acquisition times (≈4 min/slice). Here, we use Cramér-Rao lower bound theory and data reduction strategies to select optimal t I /t D combinations to reduce imaging times. The schemes were experimentally validated in phantoms, and tested in healthy volunteers (N = 4) and a multiple sclerosis patient. Two optimal sampling schemes were determined: (i) a 5-point scheme (k mf estimated) and (ii) a 4-point scheme (k mf assumed). In phantoms, the 5/4-point schemes yielded parameter estimates with similar SNRs as our previous 16-point scheme, but with 4.1/6.1-fold shorter scan times. Pair-wise comparisons between schemes did not detect significant differences for any scheme/parameter. In humans, parameter values were consistent with published values, and similar levels of precision were obtained from all schemes. Furthermore, fixing k mf reduced the sensitivity of PSR to partial-volume averaging, yielding more consistent estimates throughout the brain. qMT parameters can be robustly estimated in ≤1 min/slice (without independent measures of ΔB 0 , B1+, and T 1 ) when optimized t I -t D combinations are selected. © 2018 International Society for Magnetic Resonance in Medicine.
Nazem-Zadeh, Mohammad-Reza; Schwalb, Jason M; Elisevich, Kost V; Bagher-Ebadian, Hassan; Hamidian, Hajar; Akhondi-Asl, Ali-Reza; Jafari-Khouzani, Kourosh; Soltanian-Zadeh, Hamid
2014-07-15
To analyze the utility of a quantitative uncertainty analysis approach for evaluation and comparison of various MRI findings for the lateralization of epileptogenicity in mesial temporal lobe epilepsy (mTLE), including novel diffusion-based analyses. We estimated the hemispheric variation uncertainty (HVU) of hippocampal T1 volumetry and FLAIR (Fluid Attenuated Inversion Recovery) intensity. Using diffusion tensor images of 23 nonepileptic subjects, we estimated the HVU levels of mean diffusivity (MD) in the hippocampus, and fractional anisotropy (FA) in the posteroinferior cingulum and crus of fornix. Imaging from a retrospective cohort of 20 TLE patients who had undergone surgical resection with Engel class I outcomes was analyzed to determine whether asymmetry of preoperative volumetrics, FLAIR intensities, and MD values in hippocampi, as well as FA values in posteroinferior cingula and fornix crura correctly predicted laterality of seizure onset. Ten of the cohort had pathologically proven mesial temporal sclerosis (MTS). Seven of these patients had undergone extraoperative electrocorticography (ECoG) for lateralization or to rule out extra-temporal foci. HVU was estimated to be 3.1×10(-5) for hippocampal MD, 0.027 for FA in posteroinferior cingulum, 0.018 for FA in crus of fornix, 0.069 for hippocampal normalized volume, and 0.099 for hippocampal normalized FLAIR intensity. Using HVU analysis, a higher hippocampal MD value, lower FA within the posteroinferior cingulum and crus of fornix, shrinkage in hippocampal volume, and higher hippocampal FLAIR intensity were observed beyond uncertainty on the side ipsilateral to seizure onset for 10, 10, 9, 9, and 10 out of 10 pathology-proven MTS patients, respectively. Considering all 20 TLE patients, these numbers were 18, 15, 14, 13, and 16, respectively. However, consolidating the lateralization results of HVU analysis on these quantities by majority voting has detected the epileptogenic side for 19 out of 20 cases
Gradient echo single scan inversion recovery: application to proton and fluorine relaxation studies.
Pavuluri, KowsalyaDevi; Ramanathan, K V
2016-02-01
Single scan longitudinal relaxation measurement experiments enable rapid estimation of the spin-lattice relaxation time (T1 ) as the time series of spin relaxation is encoded spatially in the sample at different slices resulting in an order of magnitude saving in time. We consider here a single scan inversion recovery pulse sequence that incorporates a gradient echo sequence. The proposed pulse sequence provides spectra with significantly enhanced signal to noise ratio leading to an accurate estimation of T1 values. The method is applicable for measuring a range of T1 values, thus indicating the possibility of routine use of the method for several systems. A comparative study of different single scan methods currently available is presented, and the advantage of the proposed sequence is highlighted. The possibility of the use of the method for the study of cross-correlation effects for the case of fluorine in a single shot is also demonstrated. Copyright © 2015 John Wiley & Sons, Ltd.
Low-energy antiprotons physics and the FLAIR facility
International Nuclear Information System (INIS)
Widmann, E
2015-01-01
FLAIR, the Facility for low-energy antiproton and ion research has been proposed in 2004 as an extension of the planned FAIR facility at Darmstadt, Germany. FLAIR was not included into the modularized start version of FAIR, but the recent installation of the CRYRING storage ring at GSI Darmstadt has opened new perspectives for physics with low-energy antiprotons at FAIR. (paper)
Tissue Border Enhancement by inversion recovery MRI at 7.0 Tesla
International Nuclear Information System (INIS)
Costagli, Mauro; Tiberi, Gianluigi; Kelley, Douglas A.C.; Symms, Mark R.; Biagi, Laura; Tosetti, Michela; Stara, Riccardo; Cosottini, Mirco; Maggioni, Eleonora; Barba, Carmen; Guerrini, Renzo
2014-01-01
This contribution presents a magnetic resonance imaging (MRI) acquisition technique named Tissue Border Enhancement (TBE), whose purpose is to produce images with enhanced visualization of borders between two tissues of interest without any post-processing. The technique is based on an inversion recovery sequence that employs an appropriate inversion time to produce images where the interface between two tissues of interest is hypo-intense; therefore, tissue borders are clearly represented by dark lines. This effect is achieved by setting imaging parameters such that two neighboring tissues of interest have magnetization with equal magnitude but opposite sign; therefore, the voxels containing a mixture of each tissue (that is, the tissue interface) possess minimal net signal. The technique was implemented on a 7.0 T MRI system. This approach can assist the definition of tissue borders, such as that between cortical gray matter and white matter; therefore, it could facilitate segmentation procedures, which are often challenging on ultra-high-field systems due to inhomogeneous radiofrequency distribution. TBE allows delineating the contours of structural abnormalities, and its capabilities were demonstrated with patients with focal cortical dysplasia, gray matter heterotopia, and polymicrogyria. This technique provides a new type of image contrast and has several possible applications in basic neuroscience, neurogenetic research, and clinical practice, as it could improve the detection power of MRI in the characterization of cortical malformations, enhance the contour of small anatomical structures of interest, and facilitate cortical segmentation. (orig.)
International Nuclear Information System (INIS)
Foerster, Alex; Wenz, Holger; Kerl, Hans Ulrich; Al-Zghloul, Mansour; Habich, Sonia; Groden, Christoph
2014-01-01
The objectives of this paper are to assess collateral blood flow in posterior circulation occlusion by MRI-based approaches (fluid-attenuated inversion recovery (FLAIR) vascular hyperintensities (FVHs), collateralization on dynamic 4D angiograms) and investigate its relation to ischemic lesion size and growth. In 28 patients with posterior cerebral artery (PCA) and 10 patients with basilar artery (BA) occlusion, MRI findings were analyzed, with emphasis on distal FVH and collateralization on dynamic 4D angiograms. In PCA occlusion, distal FVH was observed in 18/29 (62.1 %), in BA occlusion, in 8/10 (80 %) cases. Collateralization on dynamic 4D angiograms was graded 1 in 8 (27.6 %) patients, 2 in 1 (3.4 %) patient, 3 in 12 (41.4 %) patients, and 4 in 8 (27.6 %) patients with PCA occlusion and 0 in 1 (10 %) patient, 2 in 3 (30 %) patients, 3 in 1 (10 %) patient, and 4 in 5 (50 %) patients with BA occlusion. FVH grade showed neither correlation with initial or follow-up diffusion-weighted image (DWI) lesion size nor DWI-perfusion-weighted imaging (PWI) mismatch ratio. Collateralization on dynamic 4D angiograms correlated inversely with initial DWI lesion size and moderately with the DWI-(PWI) mismatch ratio. The combination of distal FVH and collateralization grade on dynamic 4D angiograms correlated inversely with initial as well as follow-up DWI lesion size and highly with the DWI-PWI mismatch ratio. In posterior circulation occlusion, FVH is a frequent finding, but its prognostic value is limited. Dynamic 4D angiograms are advantageous to examine and graduate collateral blood flow. The combination of both parameters results in an improved characterization of collateral blood flow and might have prognostic relevance. (orig.)
Freire, Paulo G L; Ferrari, Ricardo J
2016-06-01
Multiple sclerosis (MS) is a demyelinating autoimmune disease that attacks the central nervous system (CNS) and affects more than 2 million people worldwide. The segmentation of MS lesions in magnetic resonance imaging (MRI) is a very important task to assess how a patient is responding to treatment and how the disease is progressing. Computational approaches have been proposed over the years to segment MS lesions and reduce the amount of time spent on manual delineation and inter- and intra-rater variability and bias. However, fully-automatic segmentation of MS lesions still remains an open problem. In this work, we propose an iterative approach using Student's t mixture models and probabilistic anatomical atlases to automatically segment MS lesions in Fluid Attenuated Inversion Recovery (FLAIR) images. Our technique resembles a refinement approach by iteratively segmenting brain tissues into smaller classes until MS lesions are grouped as the most hyperintense one. To validate our technique we used 21 clinical images from the 2015 Longitudinal Multiple Sclerosis Lesion Segmentation Challenge dataset. Evaluation using Dice Similarity Coefficient (DSC), True Positive Ratio (TPR), False Positive Ratio (FPR), Volume Difference (VD) and Pearson's r coefficient shows that our technique has a good spatial and volumetric agreement with raters' manual delineations. Also, a comparison between our proposal and the state-of-the-art shows that our technique is comparable and, in some cases, better than some approaches, thus being a viable alternative for automatic MS lesion segmentation in MRI. Copyright © 2016 Elsevier Ltd. All rights reserved.
Rapid T1 quantification based on 3D phase sensitive inversion recovery
International Nuclear Information System (INIS)
Warntjes, Marcel JB; Kihlberg, Johan; Engvall, Jan
2010-01-01
In Contrast Enhanced Magnetic Resonance Imaging fibrotic myocardium can be distinguished from healthy tissue using the difference in the longitudinal T 1 relaxation after administration of Gadolinium, the so-called Late Gd Enhancement. The purpose of this work was to measure the myocardial absolute T 1 post-Gd from a single breath-hold 3D Phase Sensitivity Inversion Recovery sequence (PSIR). Equations were derived to take the acquisition and saturation effects on the magnetization into account. The accuracy of the method was investigated on phantoms and using simulations. The method was applied to a group of patients with suspected myocardial infarction where the absolute difference in relaxation of healthy and fibrotic myocardium was measured at about 15 minutes post-contrast. The evolution of the absolute R 1 relaxation rate (1/T 1 ) over time after contrast injection was followed for one patient and compared to T 1 mapping using Look-Locker. Based on the T 1 maps synthetic LGE images were reconstructed and compared to the conventional LGE images. The fitting algorithm is robust against variation in acquisition flip angle, the inversion delay time and cardiac arrhythmia. The observed relaxation rate of the myocardium is 1.2 s -1 , increasing to 6 - 7 s -1 after contrast injection and decreasing to 2 - 2.5 s -1 for healthy myocardium and to 3.5 - 4 s -1 for fibrotic myocardium. Synthesized images based on the T 1 maps correspond very well to actual LGE images. The method provides a robust quantification of post-Gd T 1 relaxation for a complete cardiac volume within a single breath-hold
Rapid T1 quantification based on 3D phase sensitive inversion recovery
Directory of Open Access Journals (Sweden)
Warntjes Marcel JB
2010-08-01
Full Text Available Abstract Background In Contrast Enhanced Magnetic Resonance Imaging fibrotic myocardium can be distinguished from healthy tissue using the difference in the longitudinal T1 relaxation after administration of Gadolinium, the so-called Late Gd Enhancement. The purpose of this work was to measure the myocardial absolute T1 post-Gd from a single breath-hold 3D Phase Sensitivity Inversion Recovery sequence (PSIR. Equations were derived to take the acquisition and saturation effects on the magnetization into account. Methods The accuracy of the method was investigated on phantoms and using simulations. The method was applied to a group of patients with suspected myocardial infarction where the absolute difference in relaxation of healthy and fibrotic myocardium was measured at about 15 minutes post-contrast. The evolution of the absolute R1 relaxation rate (1/T1 over time after contrast injection was followed for one patient and compared to T1 mapping using Look-Locker. Based on the T1 maps synthetic LGE images were reconstructed and compared to the conventional LGE images. Results The fitting algorithm is robust against variation in acquisition flip angle, the inversion delay time and cardiac arrhythmia. The observed relaxation rate of the myocardium is 1.2 s-1, increasing to 6 - 7 s-1 after contrast injection and decreasing to 2 - 2.5 s-1 for healthy myocardium and to 3.5 - 4 s-1 for fibrotic myocardium. Synthesized images based on the T1 maps correspond very well to actual LGE images. Conclusions The method provides a robust quantification of post-Gd T1 relaxation for a complete cardiac volume within a single breath-hold.
Inversion recovery single-shot TurboFLASH for assessment of myocardial infarction at 3 Tesla.
Bauner, Kerstin U; Muehling, Olaf; Wintersperger, Bernd J; Winnik, Eva; Reiser, Maximilian F; Huber, Armin
2007-06-01
The aim of the study was to assess the diagnostic accuracy of imaging myocardial infarction with a single-shot inversion recovery turbofast low-angle shot (SS IR turboFLASH) sequence at 3.0 Tesla in comparison with an established segmented inversion recovery turboFLASH sequence at 1.5 Tesla. Fifteen patients with myocardial infarction were examined at a 1.5 Tesla magnetic resonance (MR) System (Avanto, Siemens, Medical Solutions) and at a 3.0 Tesla MR system (TIM Trio, Siemens, Medical Solutions). Imaging delayed enhancement was started 15 minutes after application of contrast material. A SS IR turboFLASH was performed at 3.0 Tesla and compared with a segmented IR turboFLASH sequence at 1.5 and at 3.0 Tesla. The IR turboFLASH sequence at 1.5 Tesla served as reference method. Infarct volumes, contrast/noise ratio (CNR) of infarcted and normal myocardium were compared with the reference method. The Single-Shot IR turboFLASH technique allows imaging 9 slices during a single breath-hold. The CNR between infarction and normal myocardium of the reference method was 6.4 at 1.5 Tesla. The mean value of CNR of the IR turboFLASH sequence was 7.3 at 3.0 Tesla for the single-shot technique and 14.1 at 3.0 Tesla for the segmented technique. No significant difference was found for the CNR values of the reference technique at 1.5 Tesla and the single-shot technique at 3.0 Tesla, however for the comparison of the segmented technique at 1.5 and at 3 Tesla (P = 0.0001). The correlation coefficients of the infarct volumes, determined with the Single-Shot IR turboFLASH and the segmented IR turboFLASH technique at 3.0 compared with the reference method, were r = 0.95 (P < 0.0001) and r = 0.95 (P < 0.0001). The loss of CNR, which is caused by replacement of the segmented technique by the single-shot technique, is completely compensated by the approximately 2-fold CNR increase at the higher field strength. The IR turboFLASH technique at 3.0 Tesla IR can be used as a single-shot technique
Energy Technology Data Exchange (ETDEWEB)
Daldrup, H.E.; Schuierer, G.; Link, T.M.; Moeller, H.; Bick, U.; Peters, P.E. [Institute of Clinical Radiology, Westfaelische Wilhelms Universitaet, D-48149 Muenster (Germany); Kurlemann, G. [Department of Pediatrics, Westfaelische Wilhelms Universitaet, D-48149 Muenster (Germany)
1997-12-01
The aim of our work was to determine the efficacy of turbo inversion recovery spin echo (TIRSE) pulse sequences in differentiating patients with normal and abnormal myelination. Twenty neurological normal children (aged 5 months to 12 years) as well as 65 children presenting clinically with neurologic developmental deficits (aged 2 months to 10 years) were examined using TIRSE, T1-weighted SE, and T2-weighted turbo SE pulse sequences. Contrast-to-noise-ratio (CNR) between myelinated white and gray matter was compared for the different pulse sequences. In addition, two readers analyzed all images qualitatively by consensus. The CNR values were significantly higher on TIRSE images as compared with conventional images (p < 0.05). Forty-two neurologically abnormal patients displayed a normal myelination on all sequences, whereas 23 showed an abnormal myelination. The TIRSE sequence provided a sensitive and specific depiction of an abnormal myelination in all of these patients. The TIRSE sequence provided additional information to conventional pulse sequences in determining myelination disorders in children, especially in children older than 2 years. (orig.) With 9 figs., 25 refs.
International Nuclear Information System (INIS)
Oppenheim, C.; Dormont, D.; Lehericy, S.; Marsault, C.; Logak, M.; Manai, R.; Samson, Y.; Rancurel, G.
2000-01-01
We evaluated the feasibility and use of diffusion-weighted and fluid-attenuated inversion-recovery pulse sequences performed as an emergency for patients with acute ischaemic stroke. A 5-min MRI session was designed as an emergency diagnostic procedure for patients admitted with suspected acute ischaemic stroke. We reviewed routine clinical implementation of the procedure, and its sensitivity and specificity for acute ischaemic stroke over the first 8 months. We imaged 91 patients (80 min to 48 h following the onset of stroke). Clinical deficit had resolved in less than 3 h in 15 patients, and the remaining 76 were classified as stroke (59) or stroke-like (17) after hospital discharge. Sensitivity of MRI for acute ischaemic stroke was 98 %, specificity 100 %. MRI provided an immediate and accurate picture of the number, site, size and age of ischaemic lesions in stroke and simplified diagnosis in stroke-like episodes. The feasibility and high diagnostic accuracy of emergency MRI in acute stroke strongly support its routine use in a stroke centre. (orig.)
International Nuclear Information System (INIS)
Bink, Andrea; Gaa, Jochen; Lanfermann, Heinrich; Zanella, Friedhelm E.; Schmitt, Melanie; Mugler, John P.
2006-01-01
The aim of this study was to compare conventional 2D FLAIR and single-slab 3D FLAIR sequences in the detection of lesions in patients with multiple sclerosis. Eight patients with MS were examined at 3.0 T by using a 2D FLAIR sequence and a single-slab 3D FLAIR sequence. A comparison of lesion detectability was performed for the following regions: periventricular, nonperiventricular/juxtacortical and infratentorial. The contrast-to-noise ratios (CNRs) between lesions and brain tissue and CSF were calculated for each sequence. A total of 424 lesions were found using the 2D FLAIR sequence, while with the 3D FLAIR sequence 719 lesions were found. With the 2D FLAIR sequence, 41% fewer lesions were detected than with the 3D FLAIR sequence. Further, 40% fewer supratentorial and 62.5% fewer infratentorial lesions were found with the 2D FLAIR sequence. In images acquired with the 3D FLAIR sequence, the lesions had significantly higher CNRs than in images acquired with the 2D FLAIR sequence. These are the first results using a single-slab 3D FLAIR sequence at 3.0 T for detection of lesions in patients with MS. With the 3D FLAIR sequence significantly higher CNRs were achieved and significantly more lesions in patients with MS were detected. (orig.)
Subcallosal Striations: the Role of FLAIR MR Imaging in Detecting ...
African Journals Online (AJOL)
FLAIR) in detection of subcallosal striations in clinical Multiple sclerosis (MS) patients and determine its role as a good noninvasive tool for the diagnosis of this disease. Material and Method: Forty patients with clinically proved MS were examined ...
Energy Technology Data Exchange (ETDEWEB)
Panara, V.; Navarra, R; Caulo, M. [University ' ' G. d' Annunzio' ' , Department of Neuroscience, Imaging and Clinical Sciences, Chieti (Italy); University ' ' G. d' Annunzio' ' , ITAB Institute of Advanced Biomedical Technologies, Chieti (Italy); Mattei, P.A. [University ' ' G. d' Annunzio' ' , ITAB Institute of Advanced Biomedical Technologies, Chieti (Italy); University ' ' G. d' Annunzio' ' , Department of Medicine and Science of Aging, Ophthalmology Clinic, Chieti (Italy); Piccirilli, E. [University ' ' G. d' Annunzio' ' , ITAB Institute of Advanced Biomedical Technologies, Chieti (Italy); Cotroneo, A.R.; Uncini, A. [University ' ' G. d' Annunzio' ' , Department of Neuroscience, Imaging and Clinical Sciences, Chieti (Italy); Papinutto, N.; Henry, R.G. [University of California, San Francisco, Department of Neurology, San Francisco, CA (United States)
2017-08-15
The aim of this prospective study was to determine the feasibility in terms of repeatability and reproducibility of diffusional kurtosis imaging (DKI) for microstructural assessment of the normal cervical spinal cord (cSC) using a phase-sensitive inversion recovery (PSIR) sequence as the anatomical reference for accurately defining white-matter (WM) and gray-matter (GM) regions of interests (ROIs). Thirteen young healthy subjects were enrolled to undergo DKI and PSIR sequences in the cSC. The repeatability and reproducibility of kurtosis metrics and fractional anisotropy (FA) were calculated in GM, WM, and cerebral-spinal-fluid (CSF) ROIs drawn by two independent readers on PSIR images of three different levels (C1-C4). The presence of statistically significant differences in DKI metrics for levels, ROIs (GM, WM, and CSF) repeatability, reproducibility, and inter-reader agreement was evaluated. Intra-class correlation coefficients between the two readers ranged from good to excellent (0.75 to 0.90). The inferior level consistently had the highest concordance. The lower values of scan-rescan variability for all DKI parameters were found for the inferior level. Statistically significant differences in kurtosis values were not found in the lateral white-matter bundles of the spinal cord. The integration of DKI and PSIR sequences in a clinical MR acquisition to explore the regional microstructure of the cSC in healthy subjects is feasible, and the results obtainable are reproducible. Further investigation will be required to verify the possibility to translate this method to a clinical setting to study patients with SC involvement especially in the absence of MRI abnormalities on standard sequences. (orig.)
Quantitative magnetization transfer imaging of rodent glioma using selective inversion recovery.
Xu, Junzhong; Li, Ke; Zu, Zhongliang; Li, Xia; Gochberg, Daniel F; Gore, John C
2014-03-01
Magnetization transfer (MT) provides an indirect means to detect noninvasively variations in macromolecular contents in biological tissues, but, so far, there have been only a few quantitative MT (qMT) studies reported in cancer, all of which used off-resonance pulsed saturation methods. This article describes the first implementation of a different qMT approach, selective inversion recovery (SIR), for the characterization of tumor in vivo using a rodent glioma model. The SIR method is an on-resonance method capable of fitting qMT parameters and T1 relaxation time simultaneously without mapping B0 and B1 , which is very suitable for high-field qMT measurements because of the lower saturation absorption rate. The results show that the average pool size ratio (PSR, the macromolecular pool versus the free water pool) in rat 9 L glioma (5.7%) is significantly lower than that in normal rat gray matter (9.2%) and white matter (17.4%), which suggests that PSR is potentially a sensitive imaging biomarker for the assessment of brain tumor. Despite being less robust, the estimated MT exchange rates also show clear differences from normal tissues (19.7 Hz for tumors versus 14.8 and 10.2 Hz for gray and white mater, respectively). In addition, the influence of confounding effects, e.g. B1 inhomogeneity, on qMT parameter estimates is investigated with numerical simulations. These findings not only help to better understand the changes in the macromolecular contents of tumors, but are also important for the interpretation of other imaging contrasts, such as chemical exchange saturation transfer of tumors. Copyright © 2013 John Wiley & Sons, Ltd.
Santucci, Domiziana; Lee, Sheila S.; Hartman, Heidi; Walgampaya, Shyama; AlObaidy, Mamdoh; Ramalho, Miguel; Dale, Brian M.; Semelka, Richard C.
2017-01-01
Abstract Objective: The purpose of this study was to compare two short-tau inversion recovery (STIR) sequences, Cartesian and radial (BLADE) acquisitions, for breast magnetic resonance imaging (MRI) examinations. Materials and Methods: Ninety-six women underwent 1.5 T breast MRI exam (48 Cartesian and 48 BLADE). Qualitative analysis including image artifacts, image quality, fat-suppression, chest-wall depiction, lesion detection, lymph node depiction and overall impression were evaluated by...
Chen, Liwen; Xu, Qiang
2018-02-01
This paper proposes new iterative algorithms for the unknown input and state recovery from the system outputs using an approximate inverse of the strictly proper linear time-invariant (LTI) multivariable system. One of the unique advantages from previous system inverse algorithms is that the output differentiation is not required. The approximate system inverse is stable due to the systematic optimal design of a dummy feedthrough D matrix in the state-space model via the feedback stabilization. The optimal design procedure avoids trial and error to identify such a D matrix which saves tremendous amount of efforts. From the derived and proved convergence criteria, such an optimal D matrix also guarantees the convergence of algorithms. Illustrative examples show significant improvement of the reference input signal tracking by the algorithms and optimal D design over non-iterative counterparts on controllable or stabilizable LTI systems, respectively. Case studies of two Boeing-767 aircraft aerodynamic models further demonstrate the capability of the proposed methods.
International Nuclear Information System (INIS)
Kazama, Toshiki; Nasu, Katsuhiro; Kuroki, Yoshifumi; Nawano, Shigeru; Ito, Hisao
2009-01-01
Fat suppression is essential for diffusion-weighted imaging (DWI) in the body. However, the chemical shift selective (CHESS) pulse often fails to suppress fat signals in the breast. The purpose of this study was to compare DWI using CHESS and DWI using short inversion time inversion recovery (STIR) in terms of fat suppression and the apparent diffusion coefficient (ADC) value. DWI using STIR, DWI using CHESS, and contrast-enhanced T1-weighted images were obtained in 32 patients with breast carcinoma. Uniformity of fat suppression, ADC, signal intensity, and visualization of the breast tumors were evaluated. In 44% (14/32) of patients there was insufficient fat suppression in the breasts on DWI using CHESS, whereas 0% was observed on DWI using STIR (P<0.0001). The ADCs obtained for DWI using STIR were 4.3% lower than those obtained for DWI using CHESS (P<0.02); there was a strong correlation of the ADC measurement (r=0.93, P<0.001). DWI using STIR may be excellent for fat suppression; and the ADC obtained in this sequence was well correlated with that obtained with DWI using CHESS. DWI using STIR may be useful when the fat suppression technique in DWI using CHESS does not work well. (author)
Energy Technology Data Exchange (ETDEWEB)
Saeki, N.; Kansaku, K.; Higuchi, Y.; Yamaura, A. [Dept. of Neurological Surgery, Chiba University School of Medicine (Japan); Kawano, K.; Iijima, T. [Electrotechnical Lab., Tsukuba (Japan); Inoue, N. [GE Yokagawa Medical Systems, Tokyo (Japan)
2001-07-01
Short-inversion time inversion-recovery (STIR) imaging using a 3 tesla system was assessed to reveal the postcommissural fibres (PF) of the fornix, which have rarely been highlighted neuroradiologically in the clinical setting. We studied 27 normal subjects. Sequence parameters were TR/TE/TI 8000/52/150 ms. STIR was expected to take advantage of the high signal-to-noise ratio of a high-field system, due to the long repetition time. PF were identifiable in axial and coronal slices in all cases. They were bordered anteriorly and superiorly by the anterior commissure and posteriorly and inferiorly by the mamillary body. Behind the anterior commissure, they ran in an arch-shaped posterior and inferior course in the hypothalamic nuclei and joined the mamillary body anterolaterally. They usually extended through three 3-mm slices (with 1 mm interslice gap) in anteroposterior and vertical dimensions. Little variation was observed in their course or size. Demonstration of the PF would provide a more detailed correlation of human neuroanatomy to hypothalamic function and individualised understanding of hypothalamic pathology and influence therapy. (orig.)
Yoshida, Tsukasa; Urikura, Atsushi; Shirata, Kensei; Nakaya, Yoshihiro; Endo, Masahiro; Terashima, Shingo; Hosokawa, Yoichiro
2018-04-01
This study aimed to compare the signal-to-noise ratios (SNRs) and apparent diffusion coefficients (ADCs) obtained using two fat suppression techniques in breast diffusion-weighted imaging (DWI) of a phantom. The breast phantom comprised agar gels with four different concentrations of granulated sugar (samples 1, 2, 3, and 4). DWI with short tau inversion recovery (STIR-DWI) and that with spectral attenuated inversion recovery (SPAIR-DWI) were performed using 3.0-T magnetic resonance imaging, and the obtained SNRs and ADCs were compared. ADCs were also compared between the right and left breast phantoms. For samples 3 and 4, SNRs obtained using STIR-DWI were lower than those obtained using SPAIR-DWI. For samples 2, 3, and 4, overall ADCs obtained using STIR-DWI were significantly higher than those obtained using SPAIR-DWI (p phantoms than SPAIR-DWI. SNRs and ADCs obtained using STIR-DWI are influenced by the T 1 value; a shorter T 1 value decreases SNRs, overestimates ADCs, and induces the measurement error in ADCs. STIR-DWI showed a larger difference in ADCs between the right and left phantoms than SPAIR-DWI.
Recovery of material parameters of soft hyperelastic tissue by an inverse spectral technique
Gou, Kun
2012-07-01
An inverse spectral method is developed for recovering a spatially inhomogeneous shear modulus for soft tissue. The study is motivated by a novel use of the intravascular ultrasound technique to image arteries. The arterial wall is idealized as a nonlinear isotropic cylindrical hyperelastic body. A boundary value problem is formulated for the response of the arterial wall within a specific class of quasistatic deformations reflective of the response due to imposed blood pressure. Subsequently, a boundary value problem is developed via an asymptotic construction modeling intravascular ultrasound interrogation which generates small amplitude, high frequency time harmonic vibrations superimposed on the static finite deformation. This leads to a system of second order ordinary Sturm-Liouville boundary value problems that are then employed to reconstruct the shear modulus through a nonlinear inverse spectral technique. Numerical examples are demonstrated to show the viability of the method. © 2012 Elsevier Ltd. All rights reserved.
On an inverse source problem for enhanced oil recovery by wave motion maximization in reservoirs
Karve, Pranav M.
2014-12-28
© 2014, Springer International Publishing Switzerland. We discuss an optimization methodology for focusing wave energy to subterranean formations using strong motion actuators placed on the ground surface. The motivation stems from the desire to increase the mobility of otherwise entrapped oil. The goal is to arrive at the spatial and temporal description of surface sources that are capable of maximizing mobility in the target reservoir. The focusing problem is posed as an inverse source problem. The underlying wave propagation problems are abstracted in two spatial dimensions, and the semi-infinite extent of the physical domain is negotiated by a buffer of perfectly-matched-layers (PMLs) placed at the domain’s truncation boundary. We discuss two possible numerical implementations: Their utility for deciding the tempo-spatial characteristics of optimal wave sources is shown via numerical experiments. Overall, the simulations demonstrate the inverse source method’s ability to simultaneously optimize load locations and time signals leading to the maximization of energy delivery to a target formation.
Energy Technology Data Exchange (ETDEWEB)
Kido, Tomoyuki, E-mail: tomozo0421@gmail.com [Department of Radiology, Ehime University Graduate School of Medicine (Japan); Kido, Teruhito; Nakamura, Masashi; Kawaguchi, Naoto; Nishiyama, Yoshiko [Department of Radiology, Ehime University Graduate School of Medicine (Japan); Ogimoto, Akiyoshi [Department of Cardiovascular Internal Medicine, Ehime University Graduate School of Medicine (Japan); Miyagawa, Masao; Mochizuki, Teruhito [Department of Radiology, Ehime University Graduate School of Medicine (Japan)
2014-12-15
Highlights: • We evaluate 3D PSIR compared with 3D IR for the detection of myocardial scars. • In image quality, there was no significant difference between IR and PSIR. • A quantitative analysis of LGE volume shows a strong correlation between PSIR and IR. • PSIR detected greater LGE volume in non-ischemic cardiomyopathy patients than IR. • PSIR may have a specific role in scar evaluation of non-ischemic cardiomyopathy. - Abstract: Background: Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) is a useful technique for detecting myocardial fibrosis. LGE images are typically acquired using the inversion recovery (IR) method. Recently, phase-sensitive inversion recovery (PSIR) technology has been developed. The purpose of this study was to evaluate free-breathing 3D PSIR sequencing in comparison with breath-held 3D IR sequencing for the detection of myocardial fibrosis. Methods: One hundred twenty-three patients with suspected ischemic cardiac disease (n = 27) or non-ischemic cardiomyopathy (hypertrophic cardiomyopathy, n = 29; dilated cardiomyopathy, n = 22; sarcoidosis, n = 21; arrhythmia, n = 9; myocarditis, n = 4; amyloidosis, n = 3; and others, n = 8) were evaluated by LGE–MRI, which was performed first with the IR sequence and then with the PSIR sequence, using a 3 T MRI scanner. Image quality was scored by two independent readers using a four-point scale. The 3D LGE volume was analyzed quantitatively and compared between both sequencing methods. Results: There was no significant difference in overall image quality (p = 0.19). LGE was detected in 73 patients, who were evaluated visually. Ultimately, 58 patients with acceptable image quality were enrolled in further quantitative analyses (volume assessment). Although quantification of LGE volume revealed a strong correlation between both methods, larger LGE volumes were detected with PSIR compared to IR in patients suspected of non-ischemic cardiomyopathy (39.5 ± 25.9 cm{sup 3} for
International Nuclear Information System (INIS)
Kato, Joji; Kawamura, Yoshihiko
1999-01-01
To examine the effects of removing the gastrointestinal signal in MRCP, investigations were carried out on the combined use of intestine-positive contrast medium FerriSeltz with Ferric ammonium citrate as the main component and high-speed imaging using fast inversion recovery. The contrast effect was significantly elevated to 9.90±1.77 after administration, compared with 5.3±2.45 before administration (p<0.001). The enhancement effect also was significantly elevated to 14.45±3.18 after administration, compared with 3.50±3.10 before administration (p<0.001). These results were obtained because the null point of FerriSeltz aqueous solution (5.97 mmol/1) was in the range of about 150-200 ms. With the present method, adequate suppression of the signal intensity of the digestive tract was obtained relatively easily on MRCP, and the technique was found to be effective. (author)
Energy Technology Data Exchange (ETDEWEB)
Tortora, Fabio; Belfiore, Maria Paola; Romano, Francesco; Cappabianca, Salvatore; Cirillo, Sossio [' ' F. Magrassi-A. Lanzara' ' Second University, Naples (Italy). Dept. of Clinical and Experimental Medicine and Surgery; Prudente, Mariaevelina [Second University, Naples (Italy). Medicine Dept.; Vita Salute San Raffaele Univ., Milan (Italy). Dept. of Neuroradiology; Cirillo, Mario [Second University, Naples (Italy). Neuroradiological Services; Elefante, Andrea [Federic II Univ., Naples (Italy). Neuroradilogical Dept.; Carella, Carlo [Polidiagnostic Center Check-Up, Salerno (Italy)
2014-05-15
In Graves' Ophthalmopathy, it is important to distinguish active inflammatory phase, responsive to immunosuppressive treatment, from fibrotic unresponsive inactive one. The purpose of this study is, first, to identify the relevant orbital magnetic resonance imaging signal intensities before treatment, so to classify patients according to their clinical activity score (CAS), discriminating inactive (CAS < 3) from active Graves' Ophthalmopathy (GO) (CAS > 3) subjects and, second, to follow post-steroid treatment disease. An observational study was executed on 32 GO consecutive patients in different phases of disease, based on clinical and orbital Magnetic Resonance Imaging parameters, compared to 32 healthy volunteers. Orbital Magnetic Resonance Imaging was performed on a 1.5 tesla Magnetic Resonance Unit by an experienced neuroradiologist blinded to the clinical examinations. In pre-therapy patients, compared to controls, a medial rectus muscle statistically significant signal intensity ratio (SIR) in short-time inversion recovery (STIR) (long TR/TE) sequence was found, as well as when comparing patients before and after treatment, both medial and inferior rectus muscle SIR resulted significantly statistically different in STIR. These increased outcomes explain the inflammation oedematous phase of disease, moreover after steroid administration, compared to controls; patients presented lack of that statistically significant difference, thus suggesting treatment effectiveness. In our study, we proved STIR signal intensities increase in inflammation oedematous phase, confirming STIR sequence to define active phase of disease with more sensibility and reproducibility than CAS alone and to evaluate post-therapy involvement. (orig.)
Tortora, Fabio; Prudente, Mariaevelina; Cirillo, Mario; Elefante, Andrea; Belfiore, Maria Paola; Romano, Francesco; Cappabianca, Salvatore; Carella, Carlo; Cirillo, Sossio
2014-05-01
In Graves' Ophthalmopathy, it is important to distinguish active inflammatory phase, responsive to immunosuppressive treatment, from fibrotic unresponsive inactive one. The purpose of this study is, first, to identify the relevant orbital magnetic resonance imaging signal intensities before treatment, so to classify patients according to their clinical activity score (CAS), discriminating inactive (CAS 3) subjects and, second, to follow post-steroid treatment disease. An observational study was executed on 32 GO consecutive patients in different phases of disease, based on clinical and orbital Magnetic Resonance Imaging parameters, compared to 32 healthy volunteers. Orbital Magnetic Resonance Imaging was performed on a 1.5 tesla Magnetic Resonance Unit by an experienced neuroradiologist blinded to the clinical examinations. In pre-therapy patients, compared to controls, a medial rectus muscle statistically significant signal intensity ratio (SIR) in short-time inversion recovery (STIR) (long TR/TE) sequence was found, as well as when comparing patients before and after treatment, both medial and inferior rectus muscle SIR resulted significantly statistically different in STIR. These increased outcomes explain the inflammation oedematous phase of disease, moreover after steroid administration, compared to controls; patients presented lack of that statistically significant difference, thus suggesting treatment effectiveness. In our study, we proved STIR signal intensities increase in inflammation oedematous phase, confirming STIR sequence to define active phase of disease with more sensibility and reproducibility than CAS alone and to evaluate post-therapy involvement.
International Nuclear Information System (INIS)
Tortora, Fabio; Belfiore, Maria Paola; Romano, Francesco; Cappabianca, Salvatore; Cirillo, Sossio
2014-01-01
In Graves' Ophthalmopathy, it is important to distinguish active inflammatory phase, responsive to immunosuppressive treatment, from fibrotic unresponsive inactive one. The purpose of this study is, first, to identify the relevant orbital magnetic resonance imaging signal intensities before treatment, so to classify patients according to their clinical activity score (CAS), discriminating inactive (CAS 3) subjects and, second, to follow post-steroid treatment disease. An observational study was executed on 32 GO consecutive patients in different phases of disease, based on clinical and orbital Magnetic Resonance Imaging parameters, compared to 32 healthy volunteers. Orbital Magnetic Resonance Imaging was performed on a 1.5 tesla Magnetic Resonance Unit by an experienced neuroradiologist blinded to the clinical examinations. In pre-therapy patients, compared to controls, a medial rectus muscle statistically significant signal intensity ratio (SIR) in short-time inversion recovery (STIR) (long TR/TE) sequence was found, as well as when comparing patients before and after treatment, both medial and inferior rectus muscle SIR resulted significantly statistically different in STIR. These increased outcomes explain the inflammation oedematous phase of disease, moreover after steroid administration, compared to controls; patients presented lack of that statistically significant difference, thus suggesting treatment effectiveness. In our study, we proved STIR signal intensities increase in inflammation oedematous phase, confirming STIR sequence to define active phase of disease with more sensibility and reproducibility than CAS alone and to evaluate post-therapy involvement. (orig.)
Yasokawa, Kazuya; Ito, Katsuyoshi; Tamada, Tsutomu; Yamamoto, Akira; Hayashida, Minoru; Tanimoto, Daigo; Higaki, Atsushi; Noda, Yasufumi; Kido, Ayumu
2015-11-01
To investigate the feasibility of noncontrast-enhanced cine dynamic magnetic resonance cholangiopancreatography (MRCP) with a spatially selective inversion-recovery (IR) pulse for evaluating exocrine pancreatic function in comparison with the N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BT-PABA) test as a pancreatic exocrine function test. Twenty subjects with or without chronic pancreatitis were included. MRCP with a spatially selective IR pulse was repeated every 15 seconds for 5 minutes to acquire a total of 20 images (cine-dynamic MRCP). The median and mean frequency of the observation (the number of times) and the moving distance (mean secretion grading scores) of pancreatic juice inflow on cine-dynamic MRCP were compared with a BT-PABA test. The urinary PABA excretion rate (%) had significant positive correlations with both the mean secretion grade (r = 0.66, P = 0.002) and frequency of secretory inflow (r = 0.62, P = 0.004) in cine dynamic MRCP. Both the mean frequency of observations of pancreatic secretory inflow (1.4 ± 1.6 times vs. 14.3 ± 4.2 times, P Cine dynamic MRCP with a spatially selective IR pulse may have potential for estimating the pancreatic exocrine function noninvasively as a substitute for the BT-PABA test. © 2015 Wiley Periodicals, Inc.
Energy Technology Data Exchange (ETDEWEB)
Ogura, Akio; Hayakawa, Katsumi; Maeda, Fumie; Saeki, Fumito; Syukutani, Ai; Shibutani, Sachiko; Kuroda, Emi (Dept. of Radiology, Kyoto City Hospital, Kyoto (Japan)), email: a-ogura@mbox.kyoto-inet.or.jp
2012-05-15
Background: Magnetic resonance imaging (MRI) is highly useful for detecting diseases of the bone marrow. The sensitivity for detecting compression fracture is very high, but specificity is low for differential diagnosis between malignant and benign cases. Purpose: To evaluate the usefulness of in-phase/opposed-phase and short TI inversion recovery (STIR) magnetic resonance imaging (MRI) of bone marrow for differentiation between benign and malignant vertebral compression fractures. Material and Methods: A retrospective review of 66 patients with 70 vertebral compression fractures was performed. The signal intensity ratio (SIR) defined as SIR (opposed/in) was calculated from in-phase/opposed-phase MR images, and the signal intensity ratio as SIR (STIR) was calculated from STIR MR images. The relationships between values of SIR (opposed/in) and SIR (STIR) and the differential diagnosis of malignant vs. benign fractures were considered. Results: When SIR (opposed/in) was less than 1.0, bone marrow was benign. The bone marrow was malignant when both SIR (opposed/in) was greater than 1.0 and SIR (STIR) was less than 2.0. Conclusion: In cases of acute compression fracture, malignant bone marrow showed SIR(STIR) values less than 2.0 and SIR (in/opposed) greater than 1.0. In contrast, benign bone marrow showed SIR (STIR) values greater than 2.5. For chronic compression fracture, malignant bone marrow showed SIR (in/opposed) greater than 1.0. Bone marrow was benign in all cases with SIR (in/opposed) less than 1.0
Directory of Open Access Journals (Sweden)
Domiziana Santucci
Full Text Available Abstract Objective: The purpose of this study was to compare two short-tau inversion recovery (STIR sequences, Cartesian and radial (BLADE acquisitions, for breast magnetic resonance imaging (MRI examinations. Materials and Methods: Ninety-six women underwent 1.5 T breast MRI exam (48 Cartesian and 48 BLADE. Qualitative analysis including image artifacts, image quality, fat-suppression, chest-wall depiction, lesion detection, lymph node depiction and overall impression were evaluated by three blinded readers. Signal to noise ratios (SNRs were calculated. Cronbach's alpha test was used to assess inter-observer agreement. Subanalyses of image quality, chest-wall depiction and overall impression in 15 patients with implants and image quality in 31 patients with clips were correlated using Pearson test. Wilcoxon rank sum test and t-test were performed. Results: Motion artifacts were present in 100% and in 0% of the Cartesian and the BLADE exams, respectively. Chemical-shift artifacts were present in 8% of the Cartesian exams. Flow artifacts were more frequent on BLADE. BLADE sequence was statistically superior to Cartesian for all qualitative features (p < 0.05 except for fat-suppression (p = 0.054. In the subanalysis, BLADE was superior for implants and clips (p < 0.05. SNR was statistically greater for BLADE (48.35 vs. 16.17. Cronbach ranged from 0.502 to 0.813. Conclusion: BLADE appears to be superior to Cartesian acquisition of STIR imaging as measured by improved image quality, fewer artifacts, and improved chest wall and lymph node depiction.
James, LM; Iannone, R; Palcza, J; Renger, JJ; Calder, N; Cerchio, K; Gottesdiener, K; Hargreaves, R; Murphy, MG; Boyle, J; Dijk, DJ
2011-01-01
Rationale Histamine and dopamine contribute to the maintenance of wakefulness. Objective This study aims to conduct an exploratory analysis of the effects of 10 and 50 mg of MK-0249, a novel histamine subtype-3 receptor inverse agonist, and 200 mg of modafinil, a presumed dopaminergic compound, on EEG power spectra during sleep deprivation and subsequent recovery sleep. Methods A total of 25 healthy men were recruited to a double-blind, placebo-controlled cross-over design. EEG power spectra,...
Triple-layer appearance of Brodmann area 4 at thin-section double inversion-recovery MR imaging.
Kim, Eung Yeop; Kim, Dong-Hyun; Chang, Jong-Hee; Yoo, Eunhye; Lee, Jae-Wook; Park, Hae-Jeong
2009-02-01
To investigate whether thin-section axial double inversion-recovery (DIR) brain magnetic resonance (MR) imaging at 3.0 T can help distinguish the primary motor cortex (PMC), or Brodmann area 4, from other selected cortical regions, including the primary sensory cortex (PSC), or Brodmann areas 1-3, on the basis of the presence of a "triple-layer" appearance. This prospective study was approved by the institutional review board; informed consent was obtained from patients. This study included 191 patients (94 female, age range, 5-80 years; 97 male, age range, 5-76 years) with normal findings at 3.0-T MR imaging. The presence or absence of a triple-layer appearance within selected cortical regions on DIR images was graded independently by two neuroradiologists as definitely present (grade 2), probably present (grade 1), or definitely absent (grade 0). Ten additional patients with tumors underwent DIR imaging and intraoperative cortical mapping for further validation of the PMC. A myelin-stained brain specimen image in a patient not imaged with DIR was correlated with a representative set of DIR images. A triple-layer appearance was found in the PMC bilaterally in 184 of 191 patients; grade 0 was assigned in only seven patients, who were all younger than 10 years. Grades were significantly lower in patients younger than 10 years than in others (P .0018). Interobserver agreement was excellent (weighted kappa = 0.843). The PMC determined on DIR images was confirmed with cortical mapping in all 10 patients with tumors. Triple-layer appearance was not present in the other cortical regions examined, including the PSC (P < .01). The triple-layer appearance on DIR images corresponded to the myelin band within the PMC present on the myelin-stained specimen image. A triple-layer appearance was found in the PMC at thin-section 3.0-T DIR imaging but not in other examined brain regions and therefore might be useful as an adjunct sign for identification of motor regions.
Han, S. C.; Tangdamrongsub, N.; Razeghi, S. M.
2017-12-01
We present a methodology to invert a regional set of vertical displacement data from Global Positioning System (GPS) to determine surface mass redistribution. It is assumed that GPS deformation is a result of the Earth's elastic response to the surface mass load of hydrology, atmosphere, and ocean. The identical assumption is made when global geopotential change data from Gravity Recovery And Climate Experiment (GRACE) are used to determine surface mass changes. We developed an algorithm to estimate the spectral information of displacements from "regional" GPS data through regional spherical (Slepian) basis functions and apply the load Love numbers to estimate the mass load. We rigorously examine all systematic errors caused by various truncations (spherical harmonic series and Slepian series) and the smoothing constraint applied to the GPS-only inversion. We demonstrate the technique by processing 16 years of daily vertical motions determined from 114 GPS stations in Australia. The GPS inverted surface mass changes are validated against GRACE data, atmosphere and ocean models, and a land surface model. Seasonal and inter-annual terrestrial mass variations from GPS are in good agreement with GRACE data and the water storage models. The GPS recovery compares better with the water storage model around the smaller coastal basins of Australia than two different GRACE solutions. The sub-monthly mass changes from GPS provide meaningful results agreeing with atmospheric mass changes in central Australia. Finally, we integrate GPS data from different continents with GRACE in the least-square normal equations and solve for the global surface mass changes by jointly inverting GPS and GRACE data. We present the results of surface mass changes from the GPS-only inversion and from the joint GPS-GRACE inversion.
Directory of Open Access Journals (Sweden)
Greiser Andreas
2010-11-01
Full Text Available Abstract Background T1 mapping allows direct in-vivo quantitation of microscopic changes in the myocardium, providing new diagnostic insights into cardiac disease. Existing methods require long breath holds that are demanding for many cardiac patients. In this work we propose and validate a novel, clinically applicable, pulse sequence for myocardial T1-mapping that is compatible with typical limits for end-expiration breath-holding in patients. Materials and methods The Shortened MOdified Look-Locker Inversion recovery (ShMOLLI method uses sequential inversion recovery measurements within a single short breath-hold. Full recovery of the longitudinal magnetisation between sequential inversion pulses is not achieved, but conditional interpretation of samples for reconstruction of T1-maps is used to yield accurate measurements, and this algorithm is implemented directly on the scanner. We performed computer simulations for 100 msIn-vivo myocardial T1-mapping using this method and the previous gold-standard (MOLLI was performed in 10 healthy volunteers at 1.5T and 3T, 4 volunteers with contrast injection at 1.5T, and 4 patients with recent myocardial infarction (MI at 3T. Results We found good agreement between the average ShMOLLI and MOLLI estimates for T1 In-vivo, ShMOLLI measurements required 9.0 ± 1.1 s (MOLLI = 17.6 ± 2.9 s. Average healthy myocardial T1 s by ShMOLLI at 1.5T were 966 ± 48 ms (mean ± SD and 1166 ± 60 ms at 3T. In MI patients, the T1 in unaffected myocardium (1216 ± 42 ms was similar to controls at 3T. Ischemically injured myocardium showed increased T1 = 1432 ± 33 ms (p in-vivo variability within ShMOLLI T1-maps was only 14% (1.5T or 18% (3T higher than the MOLLI maps, but the MOLLI acquisitions were twice longer than ShMOLLI acquisitions. Conclusion ShMOLLI is an efficient method that generates immediate, high-resolution myocardial T1-maps in a short breath-hold with high precision. This technique provides a valuable
Energy Technology Data Exchange (ETDEWEB)
Witkowski, Grzegorz; Sienkiewicz-Jarosz, Halina [Institute of Psychiatry and Neurology, 1st Department of Neurology, Warsaw (Poland); Piliszek, Agnieszka; Ryglewicz, Danuta [Central Clinical Hospital of the Ministry of Interior, Department of Radiology, Warsaw (Poland); Skierczynska, Agnieszka; Poniatowska, Renata [Institute of Psychiatry and Neurology, Department of Radiology, Warsaw (Poland); Dorobek, Malgorzata; Filipek-Gliszczynska, Anna [Central Clinical Hospital of the Ministry of Interior, Department of Neurology, Warsaw (Poland); Walecki, Jerzy [Polish Academy of Science, Mossakowski Medical Research Centre, Warsaw (Poland)
2014-10-15
The DWI/FLAIR mismatch is a potential radiological marker for the timing of stroke onset. The aim of the study was to assess if the DWI/FLAIR mismatch can help to identify patients with both lacunar and nonlacunar acute ischemic stroke within 4.5 h of onset. A retrospective study was performed in which the authors analysed data from 86 ischemic lacunar and nonlacunar stroke patients with a known time of symptom onset, imaged within the first 24 h from stroke onset (36 patients <4.5 h, 14 patients 4.5-6 h, 15 patients 6-12 h, and 21 patients 12-24 h). Patients underwent the admission CT and MR scan. The presence of lesions was assessed in correlation with the duration of the stroke. The time from stroke onset to neuroimaging was significantly shorter in patients with an ischemic lesion visible only in the DWI (mean 2.78 h, n = 24) as compared to patients with signs of ischemia also in other modalities (mean 8.6 h, n = 62) (p = 0.0001, Kruskal-Wallis ANOVA). The DWI/FLAIR mismatch was characterised by a global sensitivity of 58 %, specificity 94 %, PPV 87.5 %, and NPV 76 % in identifying patients in the 4.5 h thrombolysis time window. For lacunar strokes (n = 20), these parameters were as follows: sensitivity 50 %, specificity 92.8 %, PPV 75 %, and NPV 81.2 %. The presence of acute ischemic lesions only in DWI can help to identify both lacunar and nonlacunar stroke patients who are in the 4.5 h time window for intravenous thrombolysis with high specificity. (orig.)
Toledano-Massiah, S; Sayadi, A; de Boer, R; Gelderblom, J; Mahdjoub, R; Gerber, S; Zuber, M; Zins, M; Hodel, J
2018-01-18
The use of 3D FLAIR improves the detection of brain lesions in MS patients, but requires long acquisition times. Compressed sensing reduces acquisition time by using the sparsity of MR images to randomly undersample the k-space. Our aim was to compare the image quality and diagnostic performance of 3D-FLAIR with and without compressed sensing for the detection of multiple sclerosis lesions at 3T. Twenty-three patients with relapsing-remitting MS underwent both conventional 3D-FLAIR and compressed sensing 3D-FLAIR on a 3T scanner (reduction in scan time 1 minute 25 seconds, 27%; compressed sensing factor of 1.3). Two blinded readers independently evaluated both conventional and compressed sensing FLAIR for image quality (SNR and contrast-to-noise ratio) and the number of MS lesions visible in the periventricular, intra-juxtacortical, infratentorial, and optic nerve regions. The volume of white matter lesions was measured with automatic postprocessing segmentation software for each FLAIR sequence. Image quality and the number of MS lesions detected by the readers were similar between the 2 FLAIR acquisitions ( P = .74 and P = .094, respectively). Almost perfect agreement was found between both FLAIR acquisitions for total MS lesion count (Lin concordance correlation coefficient = 0.99). Agreement between conventional and compressed sensing FLAIR was almost perfect for periventricular and infratentorial lesions and substantial for intrajuxtacortical and optic nerve lesions. Postprocessing with the segmentation software did not reveal a significant difference between conventional and compressed sensing FLAIR in total MS lesion volume ( P = .63) or the number of MS lesions ( P = .15). With a compressed sensing factor of 1.3, 3D-FLAIR is 27% faster and preserves diagnostic performance for the detection of MS plaques at 3T. © 2018 by American Journal of Neuroradiology.
International Nuclear Information System (INIS)
Dietemann, J.L.; Thibaut-Menard, A.; Neugroschl, C.; Gillis, C.; Abu Eid, M.; Bogorin, A.; Warter, J.M.; Tranchant, C.
2000-01-01
We compared the sensitivity of T2-weighted spin-echo (FSE) and fast short-tau inversion-recovery (fSTIR) sequences in detection of multiple sclerosis of the spinal cord in 100 consecutive patients with clinically confirmed multiple sclerosis (MS); 86 patients underwent also brain MRI. In all, 310 focal lesions were detected on fSTIR and 212 on T2-weighted FSE, spinal cord lesions were seen better on fSTIR images, with a higher contrast between the lesion and the normal spinal cord. In 24 patients in whom cord plaques were shown with both sequences, the cranial study was normal or inconclusive. Assessment of spinal plaques can be particularly important when MRI of the brain is inconclusive, and in there situations fSTIR can be helpful. (orig.)
International Nuclear Information System (INIS)
Yamashita, Eijiro; Kanasaki, Yoshiko; Fujii, Shinya; Ogawa, Toshihide; Tanaka, Takuro; Hirata, Yoshiharu
2011-01-01
Background Increased venous contrast in ischemic stroke using susceptibility-weighted imaging has been widely reported, although few reports have compared increased venous contrast areas with perfusion change areas. Purpose To compare venous contrast on phase-sensitive MR images (PSI) with perfusion change on flow-sensitive alternating inversion recovery (FAIR) images, and to discuss the clinical use of PSI in ischemic stroke. Material and Methods Thirty patients with clinically suspected acute infarction of the middle cerebral artery (MCA) territory within 7 days of onset were evaluated. Phase-sensitive imaging (PSI), flow-sensitive alternating inversion recovery (FAIR), diffusion-weighted imaging (DWI) and magnetic resonance angiography (MRA) were obtained using 3 Tesla scanner. Two neuroradiologists independently reviewed the MR images, as well as the PSI, DWI, and FAIR images. They were blinded to the clinical data and to each other's findings. The abnormal area of each image was ultimately identified after both neuroradiologists reached consensus. We analyzed areas of increased venous contrast on PSI, perfusion changes on FAIR images and signal changes on DWI for each case. Results Venous contrast increased on PSI and hypoperfusion was evident on FAIR images from 22 of the 30 patients (73%). The distribution of the increased venous contrast was the same as that of the hypoperfused areas on FAIR images in 16 of these 22. The extent of these lesions was larger than that of lesions visualized by on DWI in 18 of the 22 patients. Hypointense signals reflecting hemorrhage and no increased venous contrast on PSI and hyperperfusion on FAIR images were found in six of the remaining eight patients (20%). Findings on PSI were normal and hypoperfusion areas were absent on FAIR images of two patients (7%). Conclusion Increased venous contrast on PSI might serve as an index of misery perfusion and provide useful information
Directory of Open Access Journals (Sweden)
Herlihy Amy H
2008-01-01
Full Text Available Abstract Purpose To demonstrate the feasibility of using an inversion recovery pulse sequence and to define the optimal inversion time (TI to assess myocardial infarction in mice by late gadolinium enhancement (LGE MRI at 9.4T, and to obtain the maximal contrast between the infarcted and the viable myocardium. Methods MRI was performed at 9.4T in mice, two days after induction of myocardial infarction (n = 4. For cardiovascular MR imaging, a segmented magnetization-prepared fast low angle shot (MP-FLASH sequence was used with varied TIs ranging from 40 to 420 ms following administration of gadolinium-DTPA at 0.6 mmol/kg. Contrast-to-noise (CNR and signal-to-noise ratio (SNR were measured and compared for each myocardial region of interest (ROI. Results The optimal TI, which corresponded to a minimum SNR in the normal myocardium, was 268 ms ± 27.3. The SNR in the viable myocardium was significantly different from that found in the infarcted myocardium (17.2 ± 2.4 vs 82.1 ± 10.8; p = 0.006 leading to a maximal relative SI (Signal Intensity between those two areas (344.9 ± 60.4. Conclusion Despite the rapid heart rate in mice, our study demonstrates that LGE MRI can be performed at 9.4T using a protocol similar to the one used for clinical MR diagnosis of myocardial infarction.
International Nuclear Information System (INIS)
Shimada, Kazuki; Nagasaka, Tatsuo; Shidahara, Miho; Machida, Yoshio; Tamura, Hajime
2012-01-01
Accurate longitudinal relaxation time (T 1 ) of arterial blood is important in evaluating blood flow in tissue by arterial spin labeling magnetic resonance (MR) imaging. Few studies have reported the T 1 of human arterial blood in vivo, especially using 3-tesla MR imaging. T 1 values of human venous blood in vivo have been reported, but they differ from those measured in vitro. We aimed to evaluate the accurate T 1 of human arterial blood in vivo. We measured T 1 values of blood in 10 healthy volunteers in vivo using an inversion-recovery fast gradient-echo sequence and 3-tesla MR imaging unit. We also measured hematocrit (Hct) values of venous blood samples. After nonselective application of the inversion pulse using a body coil, we obtained MR imaging signals of arterial blood in the abdominal aorta. Similarly, we measured the signals of venous blood in the internal jugular vein. Inversion times varied between 200 and 5000 ms for imaging of the abdominal aorta and 200 and 2500 ms for imaging of the jugular vein. We also acquired signals without the inversion pulse. We estimated T 1 values from the data by nonlinear least squares fitting of a 3-parameter model. The T 1 value (mean±standard deviation) of arterial blood was 1779±80 ms and of venous blood, 1694±77 ms. The average Hct value was 0.47. The R 1 (=1/T 1 ) of arterial blood was related to the Hct value as: R 1 =(0.59±0.16)Hct + (0.29±0.07) (mean±standard error) s -1 . For the venous blood, R 1 =(0.70±0.11)Hct + (0.27±0.05) s -1 . We observed a T 1 of human arterial blood in vivo of 1779±80 ms at a mean hematocrit value of 0.47 as determined by 3T MR imaging; an even longer T 1 value is expected with a hematocrit value less than 0.47. (author)
Comparison of T2 and FLAIR imaging for target delineation in high grade gliomas
International Nuclear Information System (INIS)
Stall, Bronwyn; Zach, Leor; Ning, Holly; Ondos, John; Arora, Barbara; Shankavaram, Uma; Miller, Robert W; Citrin, Deborah; Camphausen, Kevin
2010-01-01
FLAIR and T2 weighted MRIs are used based on institutional preference to delineate high grade gliomas and surrounding edema for radiation treatment planning. Although these sequences have inherent physical differences there is limited data on the clinical and dosimetric impact of using either or both sequences. 40 patients with high grade gliomas consecutively treated between 2002 and 2008 of which 32 had pretreatment MRIs with T1, T2 and FLAIR available for review were selected for this study. These MRIs were fused with the treatment planning CT. Normal structures, clinical tumor volume (CTV) and planning tumor volume (PTV) were then defined on the T2 and FLAIR sequences. A Venn diagram analysis was performed for each pair of tumor volumes as well as a fractional component analysis to assess the contribution of each sequence to the union volume. For each patient the tumor volumes were compared in terms of total volume in cubic centimeters as well as anatomic location using a discordance index. The overlap of the tumor volumes with critical structures was calculated as a measure of predicted toxicity. For patients with MRI documented failures, the tumor volumes obtained using the different sequences were compared with the recurrent gross tumor volume (rGTV). The FLAIR CTVs and PTVs were significantly larger than the T2 CTVs and PTVs (p < 0.0001 and p = 0.0001 respectively). Based on the discordance index, the abnormality identified using the different sequences also differed in location. Fractional component analysis showed that the intersection of the tumor volumes as defined on both T2 and FLAIR defined the majority of the union volume contributing 63.6% to the CTV union and 82.1% to the PTV union. T2 alone uniquely identified 12.9% and 5.2% of the CTV and PTV unions respectively while FLAIR alone uniquely identified 25.7% and 12% of the CTV and PTV unions respectively. There was no difference in predicted toxicity to normal structures using T2 or FLAIR. At the
Comparison of T2 and FLAIR imaging for target delineation in high grade gliomas
Directory of Open Access Journals (Sweden)
Miller Robert W
2010-01-01
Full Text Available Abstract Background FLAIR and T2 weighted MRIs are used based on institutional preference to delineate high grade gliomas and surrounding edema for radiation treatment planning. Although these sequences have inherent physical differences there is limited data on the clinical and dosimetric impact of using either or both sequences. Methods 40 patients with high grade gliomas consecutively treated between 2002 and 2008 of which 32 had pretreatment MRIs with T1, T2 and FLAIR available for review were selected for this study. These MRIs were fused with the treatment planning CT. Normal structures, clinical tumor volume (CTV and planning tumor volume (PTV were then defined on the T2 and FLAIR sequences. A Venn diagram analysis was performed for each pair of tumor volumes as well as a fractional component analysis to assess the contribution of each sequence to the union volume. For each patient the tumor volumes were compared in terms of total volume in cubic centimeters as well as anatomic location using a discordance index. The overlap of the tumor volumes with critical structures was calculated as a measure of predicted toxicity. For patients with MRI documented failures, the tumor volumes obtained using the different sequences were compared with the recurrent gross tumor volume (rGTV. Results The FLAIR CTVs and PTVs were significantly larger than the T2 CTVs and PTVs (p Conclusions Although both T2 and FLAIR MRI sequences are used to define high grade glial neoplasm and surrounding edema, our results show that the volumes generated using these techniques are different and not interchangeable. These differences have bearing on the use of intensity modulated radiation therapy (IMRT and highly conformal treatment as well as on future clinical trials where the bias of using one technique over the other may influence the study outcome.
International Nuclear Information System (INIS)
Shimada, Kotaro; Isoda, Hiroyoshi; Okada, Tomohisa; Kamae, Toshikazu; Arizono, Shigeki; Hirokawa, Yuusuke; Shibata, Toshiya; Togashi, Kaori
2011-01-01
Objective: To study whether shortening the acquisition time for selective hepatic artery visualization is feasible without image quality deterioration by adopting two-dimensional (2D) parallel imaging (PI) and short tau inversion recovery (STIR) methods. Materials and methods: Twenty-four healthy volunteers were enrolled. 3D true steady-state free-precession imaging with a time spatial labeling inversion pulse was conducted using 1D or 2D-PI and fat suppression by chemical shift selective (CHESS) or STIR methods. Three groups of different scan conditions were assigned and compared: group A (1D-PI factor 2 and CHESS), group B (2D-PI factor 2 x 2 and CHESS), and group C (2D-PI factor 2 x 2 and STIR). The artery-to-liver contrast was quantified, and the quality of artery visualization and overall image quality were scored. Results: The mean scan time was 9.5 ± 1.0 min (mean ± standard deviation), 5.9 ± 0.8 min, and 5.8 ± 0.5 min in groups A, B, and C, respectively, and was significantly shorter in groups B and C than in group A (P < 0.01). The artery-to-liver contrast was significantly better in group C than in groups A and B (P < 0.01). The scores for artery visualization and overall image quality were worse in group B than in groups A and C. The differences were statistically significant (P < 0.05) regarding the arterial branches of segments 4 and 8. Between group A and group C, which had similar scores, there were no statistically significant differences. Conclusion: Shortening the acquisition time for selective hepatic artery visualization was feasible without deterioration of the image quality by the combination of 2D-PI and STIR methods. It will facilitate using non-contrast-enhanced MRA in clinical practice.
James, Lynette M; Iannone, Robert; Palcza, John; Renger, John J; Calder, Nicole; Cerchio, Kristine; Gottesdiener, Keith; Hargreaves, Richard; Murphy, M Gail; Boyle, Julia; Dijk, Derk-Jan
2011-06-01
Histamine and dopamine contribute to the maintenance of wakefulness. This study aims to conduct an exploratory analysis of the effects of 10 and 50 mg of MK-0249, a novel histamine subtype-3 receptor inverse agonist, and 200 mg of modafinil, a presumed dopaminergic compound, on EEG power spectra during sleep deprivation and subsequent recovery sleep. A total of 25 healthy men were recruited to a double-blind, placebo-controlled cross-over design. EEG power spectra, an electrophysiological marker of changes in sleepiness and vigilance, were obtained at the beginning of wake maintenance tests at two-hourly intervals throughout a night and day of sleep deprivation, which is an established model of excessive sleepiness. After placebo, sleep deprivation was associated with enhancements in delta and theta and reductions in alpha and beta activity. Following dosing at 02:00 h, MK-0249 and modafinil reduced delta and theta activity and enhanced alpha and beta activity, compared to placebo. During recovery sleep initiated at 21:00 h, latency to sleep onset and number of awakenings were not different from placebo for any of the active treatments. Wake after sleep onset and stage 1% was increased and total sleep time, SWS% and REM% were reduced after both doses of MK-0249. Compared to placebo, MK-0249, the 50-mg dose in particular, reduced activity in some delta and theta/alpha frequencies and enhanced beta activity during NREM sleep and REM sleep. After modafinil, no changes were observed for power spectra during sleep. Both MK-0249 and modafinil exert effects on the EEG which are consistent with wake promotion.
Energy Technology Data Exchange (ETDEWEB)
Yasokawa, Kazuya; Ito, Katsuyoshi; Tamada, Tsutomu; Yamamoto, Akira; Hayashida, Minoru; Torigoe, Teruyuki; Tanimoto, Daigo; Higaki, Atsushi; Noda, Yasufumi; Kido, Ayumu [Kawasaki Medical School, Department of Diagnostic Radiology, Kurashiki, Okayama (Japan)
2016-12-15
To evaluate the influence of oral ingestion on the secretory flow dynamics of physiological pancreatic juice within the main pancreatic duct in healthy subjects by using cine-dynamic MRCP with spatially-selective inversion-recovery (IR) pulse non-invasively. Thirty-eight healthy subjects were investigated. MRCP with spatially-selective IR pulse was repeated every 15 s for 5 min to acquire a total of 20 images (cine-dynamic MRCP). A set of 20 MRCP images was repeatedly obtained before and after liquid oral ingestion every 7 min (including 2-min interval) for 40 min (a total of seven sets). Secretion grade of pancreatic juice on cine-dynamic MRCP was compared before and after oral ingestion using the nonparametric Wilcoxon signed-rank test. Median secretion grades of pancreatic juice at 5 min (score = 2.15), 12 min (score = 1.95) and 19 min (score = 2.05) after ingestion were significantly higher than that before ingestion (score = 1.40) (P = 0.004, P = 0.032, P = 0.045, respectively). Secretion grade of pancreatic juice showed a maximum peak of 2.15 at 5 min after ingestion. Thereafter, the secretion grade of pancreatic juice tended to gradually decline. Non-invasive cine-dynamic MRCP using spatially-selective IR pulse showed potential for evaluating postprandial changes in the secretory flow dynamics of pancreatic juice as a physiological reaction. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Klang, Eyal; Aharoni, Dvora; Rimon, Uri; Eshed, Iris [Tel Aviv University, Department of Diagnostic Imaging, Sheba Medical Center, Tel Aviv (Israel); Hermann, Kay-Geert [Department of Radiology, Charite University Hospital, Berlin (Germany); Herman, Amir [Sheba Medical Center, Department of Orthopedic Surgery, Tel-Hashomer (Israel); Tel Aviv University, The Sackler School of Medicine, Tel Aviv (Israel); Shazar, Nachshon [Sheba Medical Center, Department of Orthopedic Surgery, Tel-Hashomer (Israel)
2014-04-15
To assess the contribution of contrast material in detecting and evaluating enthesitis of pelvic entheses by MRI. Sixty-seven hip or pelvic 1.5-T MRIs (30:37 male:female, mean age: 53 years) were retrospectively evaluated for the presence of hamstring and gluteus medius (GM) enthesitis by two readers (a resident and an experienced radiologist). Short tau inversion recovery (STIR) and T1-weighted pre- and post-contrast (T1+Gd) images were evaluated by each reader at two sessions. A consensus reading of two senior radiologists was regarded as the gold standard. Clinical data was retrieved from patients' referral form and medical files. Cohen's kappa was used for intra- and inter-observer agreement calculation. Diagnostic properties were calculated against the gold standard reading. A total of 228 entheses were evaluated. Gold standard analysis diagnosed 83 (36 %) enthesitis lesions. Intra-reader reliability for the experienced reader was significantly (p = 0.0001) higher in the T1+Gd images compared to the STIR images (hamstring: k = 0.84/0.45, GM: k = 0.84/0.47). Sensitivity and specificity increased from 0.74/0.8 to 0.87/0.9 in the STIR images and T1+Gd sequences. Intra-reader reliability for the inexperienced reader was lower (p > 0.05). Evidence showing that contrast material improves the reliability, sensitivity, and specificity of detecting enthesitis supports its use in this setting. (orig.)
Directory of Open Access Journals (Sweden)
Yelong Shen
2017-12-01
Full Text Available Diabetes has been reported to affect the microvasculature and lead to cerebral small vessel disease (SVD. Past studies using arterial spin labeling (ASL at single post-labeling delay reported reduced cerebral blood flow (CBF in patients with type 2 diabetes. The purpose of this study was to characterize cerebral hemodynamic changes of type 2 diabetes using a multi-inversion-time 3D GRASE pulsed ASL (PASL sequence to simultaneously measure CBF and bolus arrival time (BAT. Thirty-six patients with type 2 diabetes (43–71 years, 17 male and 36 gender- and age-matched control subjects underwent MRI scans at 3 T. Mean CBF/BAT values were computed for gray and white matter (GM and WM of each subject, while a voxel-wise analysis was performed for comparison of regional CBF and BAT between the two groups. In addition, white matter hyperintensities (WMHs were detected by a double inversion recovery (DIR sequence with relatively high sensitivity and spatial resolution. Mean CBF of the WM, but not GM, of the diabetes group was significantly lower than that of the control group (p < 0.0001. Regional CBF decreases were detected in the left middle occipital gyrus (p = 0.0075, but failed to reach significance after correction of partial volume effects. BAT increases were observed in the right calcarine fissure (p < 0.0001, left middle occipital gyrus (p < 0.0001, and right middle occipital gyrus (p = 0.0011. Within the group of diabetic patients, BAT in the right middle occipital gyrus was positively correlated with the disease duration (r = 0.501, p = 0.002, BAT in the left middle occipital gyrus was negatively correlated with the binocular visual acuity (r = −0.408, p = 0.014. Diabetic patients also had more WMHs than the control group (p = 0.0039. Significant differences in CBF, BAT, and more WMHs were observed in patients with diabetes, which may be related to impaired vision and risk of SVD of type 2 diabetes.
An energy minimization method for MS lesion segmentation from T1-w and FLAIR images.
Zhao, Yue; Guo, Shuxu; Luo, Min; Liu, Yu; Bilello, Michel; Li, Chunming
2017-06-01
In this paper, we extend the multiplicative intrinsic component optimization (MICO) algorithm to multichannel MR image segmentation, with focus on segmentation of multiple sclerosis (MS) lesions. The MICO algorithm was originally proposed by Li et al. in Ref. [1] for normal brain tissue segmentation and intensity inhomogeneity correction of a single channel MR image, which exhibits desirable advantages over other methods for MR image segmentation and intensity inhomogeneity correction in terms of segmentation accuracy and robustness. In this paper, we extend the MICO algorithm to multi-channel MR image segmentation and enable the segmentation of MS lesions. We assign different weights for different channels to control the impact of each channel. The weighted channels allow the enhancement of the impact of the FLAIR image on the segmentation of MS lesions by assigning a larger weight to the FLAIR image channel than the other channels. With the inherent mechanism of estimation of the bias field, our method is able to deal with the intensity inhomogeneity in the input multi-channel MR images. In the application of our method, we only use T1-w and FLAIR images as the input two channel MR images. Experimental results show promising result of our method. Copyright © 2016 Elsevier Inc. All rights reserved.
Legrand, Laurence; Tisserand, Marie; Turc, Guillaume; Edjlali, Myriam; Calvet, David; Trystram, Denis; Roca, Pauline; Naggara, Olivier; Mas, Jean-Louis; Méder, Jean-Francois; Baron, Jean-Claude; Oppenheim, Catherine
2016-02-01
Fluid-attenuated inversion recovery vascular hyperintensities (FVH) beyond the boundaries of diffusion-weighted imaging (DWI) lesion (FVH-DWI mismatch) have been proposed as an alternative to perfusion-weighted imaging (PWI)-DWI mismatch. We aimed to establish whether FVH-DWI mismatch can identify patients most likely to benefit from recanalization. FVH-DWI mismatch was assessed in 164 patients with proximal middle cerebral artery occlusion before intravenous thrombolysis. PWI-DWI mismatch (PWITmax>6sec/DWI>1.8) was assessed in the 104 patients with available PWI data. We tested the associations between 24-hours complete recanalization on magnetic resonance angiography and 3-month favorable outcome (modified Rankin Scale score ≤2), stratified on FVH-DWI (or PWI-DWI) status. FVH-DWI mismatch was present in 121/164 (74%) patients and recanalization in 50/164 (30%) patients. The odds ratio for favorable outcome with recanalization was 16.2 (95% confidence interval, 5.7-46.5; Pmismatch and 2.6 (95% confidence interval, 0.6-12.1; P=0.22) in those without FVH-DWI mismatch (P=0.048 for interaction). Recanalization was associated with favorable outcome in patients with PWI-DWI mismatch (odds ratios, 9.9; 95% confidence interval, 3.1-31.3; P=0.0001) and in patients without PWI-DWI mismatch (odds ratios, 7.0; 95% confidence interval, 1.1-44.1; P=0.047), P=0.76 for interaction. The FVH-DWI mismatch may rapidly identify patients with proximal occlusion most likely to benefit from recanalization. © 2016 American Heart Association, Inc.
Morimoto, Emiko; Okada, Tomohisa; Kanagaki, Mitsunori; Yamamoto, Akira; Fushimi, Yasutaka; Matsumoto, Riki; Takaya, Shigetoshi; Ikeda, Akio; Kunieda, Takeharu; Kikuchi, Takayuki; Paul, Dominik; Miyamoto, Susumu; Takahashi, Ryosuke; Togashi, Kaori
2013-12-01
To quantitatively compare the diagnostic capability of double inversion-recovery (DIR) with F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) for detection of seizure focus laterality in temporal lobe epilepsy (TLE). This study was approved by the institutional review board, and written informed consent was obtained. Fifteen patients with TLE and 38 healthy volunteers were enrolled. All magnetic resonance (MR) images were acquired using a 3T-MRI system. Voxel-based analysis (VBA) was conducted for FDG-PET images and white matter segments of DIR images (DIR-WM) focused on the whole temporal lobe (TL) and the anterior part of the temporal lobe (ATL). Distribution of hypometabolic areas on FDG-PET and increased signal intensity areas on DIR-WM were evaluated, and their laterality was compared with clinically determined seizure focus laterality. Correct diagnostic rates of laterality were evaluated, and agreement between DIR-WM and FDG-PET was assessed using κ statistics. Increased signal intensity areas on DIR-WM were located at the vicinity of the hypometabolic areas on FDG-PET, especially in the ATL. Correct diagnostic rates of seizure focus laterality for DIR-WM (0.80 and 0.67 for the TL and the ATL, respectively) were slightly higher than those for FDG-PET (0.67 and 0.60 for the TL and the ATL, respectively). Agreement of laterality between DIR-WM and FDG-PET was substantial for the TL and almost perfect for the ATL (κ = 0.67 and 0.86, respectively). High agreement in localization between DIR-WM and FDG-PET and nearly equivalent detectability of them show us an additional role of MRI in TLE. Wiley Periodicals, Inc. © 2013 International League Against Epilepsy.
Energy Technology Data Exchange (ETDEWEB)
Bao, Yi-Fang; Tang, Wei-Jun; Li, Yu-Xin; Geng, Dao-Ying [Fudan University, Department of Radiology, Huashan Hospital, Shanghai (China); Zhu, Dong-Qing; Chen, Xiang-Jun [Fudan University, Department of Neurology, Huashan Hospital, Shanghai (China); Zee, Chi-Shing [University of Southern California Keck School of Medicine, Department of Radiology, Los Angeles, CA (United States)
2013-01-15
Sensory neuronopathy (SNN) is a distinctive subtype of peripheral neuropathies, specifically targeting dorsal root ganglion (DRG). We utilized MRI to demonstrate the imaging characteristics of DRG, spinal cord (SC), and brachial plexus at C7 level in SNN. We attempted multiple-echo data image combination (MEDIC) and turbo inversion recovery magnitude (TIRM) methods in nine patients with sensory neuronopathy and compared with those in 16 disease controls and 20 healthy volunteers. All participants underwent MRI for the measurement of DRG, posterior column (PC), lateral column, and spinal cord area (SCA) at C7 level. DRG diameters were obtained through its largest cross section, standardized by dividing sagittal diameter of mid-C7 vertebral canal. We also made comparisons of standardized anteroposterior diameter (APD) and left-right diameters of SC and PC in these groups. Signal intensity and diameter of C7 spinal nerve were assessed on TIRM. Compared to control groups, signal intensities of DRG and PC were higher in SNN patients when using MEDIC, but the standardized diameters were shorter in either DRG or PC. Abnormal PC signal intensities were identified in eight out of nine SNN patients (89 %) with MEDIC and five out of nine (56 %) with T2-weighted images. SCA, assessed with MEDIC, was smaller in SNN patients than in the other groups, with significant reduction of its standardized APD. C7 nerve root diameters, assessed with TIRM, were decreased in SNN patients. MEDIC and TIRM sequences demonstrate increased signal intensities and decreased area of DRG and PC, and decreased diameter of nerve roots in patients with SNN, which can play a significant role in early diagnosis. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Yoon, Jeong Hee [Seoul National University Hospital, Department of Radiology, Seoul (Korea, Republic of); Lee, Jeong Min; Han, Joon Koo; Choi, Byung Ihn [Seoul National University Hospital, Department of Radiology, Seoul (Korea, Republic of); Seoul National University College of Medicine, Institute of Radiation Medicine, Jongno-gu, Seoul (Korea, Republic of); Paek, Munyoung [Siemens Healthcare, Seoul (Korea, Republic of)
2016-06-15
To determine whether multislice T1 mapping of the liver using a modified look-locker inversion recovery (MOLLI) sequence on gadoxetic acid-enhanced magnetic resonance imaging (MRI) can be used as a quantitative tool to estimate liver function and predict the presence of oesophageal or gastric varices. Phantoms filled with gadoxetic acid were scanned three times using MOLLI sequence to test repeatability. Patients with chronic liver disease or liver cirrhosis who underwent gadoxetic acid-enhanced liver MRI including MOLLI sequence at 3 T were included (n = 343). Pre- and postcontrast T1 relaxation times of the liver (T1liver), changes between pre- and postcontrast T1liver (ΔT1liver), and adjusted postcontrast T1liver (postcontrast T1liver-T1spleen/T1spleen) were compared among Child-Pugh classes. In 62 patients who underwent endoscopy, all T1 parameters and spleen sizes were correlated with varices. Phantom study showed excellent repeatability of MOLLI sequence. As Child-Pugh scores increased, pre- and postcontrast T1liver were significantly prolonged (P < 0.001), and ΔT1liver and adjusted postcontrast T1liver decreased (P< 0.001). Adjusted postcontrast T1liver and spleen size were independently associated with varices (R{sup 2} = 0.29, P < 0.001). T1 mapping of the liver using MOLLI sequence on gadoxetic acid-enhanced MRI demonstrated potential in quantitatively estimating liver function, and adjusted postcontrast T1liver was significantly associated with varices. (orig.)
Yasokawa, Kazuya; Ito, Katsuyoshi; Tamada, Tsutomu; Yamamoto, Akira; Hayashida, Minoru; Torigoe, Teruyuki; Tanimoto, Daigo; Higaki, Atsushi; Noda, Yasufumi; Kido, Ayumu
2016-12-01
To evaluate the influence of oral ingestion on the secretory flow dynamics of physiological pancreatic juice within the main pancreatic duct in healthy subjects by using cine-dynamic MRCP with spatially-selective inversion-recovery (IR) pulse non-invasively. Thirty-eight healthy subjects were investigated. MRCP with spatially-selective IR pulse was repeated every 15 s for 5 min to acquire a total of 20 images (cine-dynamic MRCP). A set of 20 MRCP images was repeatedly obtained before and after liquid oral ingestion every 7 min (including 2-min interval) for 40 min (a total of seven sets). Secretion grade of pancreatic juice on cine-dynamic MRCP was compared before and after oral ingestion using the nonparametric Wilcoxon signed-rank test. Median secretion grades of pancreatic juice at 5 min (score = 2.15), 12 min (score = 1.95) and 19 min (score = 2.05) after ingestion were significantly higher than that before ingestion (score = 1.40) (P = 0.004, P = 0.032, P = 0.045, respectively). Secretion grade of pancreatic juice showed a maximum peak of 2.15 at 5 min after ingestion. Thereafter, the secretion grade of pancreatic juice tended to gradually decline. Non-invasive cine-dynamic MRCP using spatially-selective IR pulse showed potential for evaluating postprandial changes in the secretory flow dynamics of pancreatic juice as a physiological reaction. • Secretion grade of pancreatic juice at cine-dynamic MRCP after ingestion was evaluated. • Secretion grade was significantly increased within 19 min after liquid meal ingestion. • Secretion grade showed maximum peak of 2.15 at 5 min after ingestion. • Postprandial changes in pancreatic juice flow can be assessed by cine-dynamic MRCP.
Bauman, Grzegorz; Pusterla, Orso; Santini, Francesco; Bieri, Oliver
2018-02-01
To demonstrate the feasibility of oxygen-dependent relaxometry in human lung using an inversion recovery ultra-fast steady-state free precession (IR-ufSSFP) technique. Electrocardiogram-triggered pulmonary relaxometry with IR-ufSSFP was performed in 7 healthy human subjects at 1.5 T. The data were acquired under both normoxic and hyperoxic conditions. In a single breath-hold of less than 9 seconds, 30 transient state IR-ufSSFP images were acquired, yielding longitudinal (T1) and transversal (T2) relaxometry parameter maps using voxel-wise nonlinear fitting. Possible spatial misalignments between consecutive IR-ufSSFP parameter maps were corrected using elastic image registration. Furthermore, dynamic relaxometry oxygen wash-in and wash-out scans were performed in one volunteer. From this, T 1 -related wash-in and wash-out time constants (τ wi , τ wo ) were calculated voxel-wise on registered maps using an exponential fitting model. For healthy lung, observed T1 values were 1399 ± 77 and 1290 ± 76 ms under normoxic and hyperoxic conditions, respectively. Oxygen-related reduction of T1 was statistically significant in every volunteer. No statistically significant change, however, was observed in T2, with normoxic and hyperoxic T2 values of 55 ± 16 and 56 ± 17 ms, respectively. The observed average τ wi was 87.0 ± 28.7 seconds, whereas the average τ wo was 73.5 ± 21.6 seconds. IR-ufSSFP allows fast, steady-state, and dynamic oxygen-dependent relaxometry of the human lung. Magn Reson Med 79:839-845, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.
Directory of Open Access Journals (Sweden)
Matthias Gawlitza
Full Text Available To assess FLAIR vascular hyperintensities (FVH and dynamic (4D angiograms derived from perfusion raw data as proposed magnetic resonance (MR imaging markers of leptomeningeal collateral circulation in patients with ischemia in the territory of the anterior cerebral artery (ACA.Forty patients from two tertiary care university hospitals were included. Infarct volumes and perfusion deficits were manually measured on DWI images and TTP maps, respectively. FVH and collateral flow on 4D MR angiograms were assessed and graded as previously specified.Forty-one hemispheres were affected. Mean DWI lesion volume was 8.2 (± 13.9; range 0-76.9 ml, mean TTP lesion volume was 24.5 (± 17.2, range 0-76.7 ml. FVH were observed in 26/41 (63.4% hemispheres. Significant correlations were detected between FVH and TTP lesion volume (ρ = 0.4; P<0.01 absolute (ρ = 0.37; P<0.05 and relative mismatch volume (ρ = 0.35; P<0.05. The modified ASITN/SIR score correlated inversely with DWI lesion volume (ρ = -0.58; P<0.01 and positively with relative mismatch (ρ = 0.29; P< 0.05. ANOVA of the ASITN/SIR score revealed significant inter-group differences for DWI (P<0.001 and TTP lesion volumes (P<0.05. No correlation was observed between FVH scores and modified ASITH/SIR scores (ρ = -0.16; P = 0.32.FVH and flow patterns on 4D MR angiograms are markers of perfusion deficits and tissue at risk. As both methods did not show a correlation between each other, they seem to provide complimentary instead of redundant information. Previously shown evidence for the meaning of these specific MR signs in internal carotid and middle cerebral artery stroke seems to be transferrable to ischemic stroke in the ACA territory.
International Nuclear Information System (INIS)
Stehling, C.; Niederstadt, T.; Kraemer, S.; Kugel, H.; Schwindt, W.; Heindel, W.; Bachmann, R.
2005-01-01
Purpose: The increased T1 relaxation times at 3.0 Tesla lead to a reduced T1 contrast, requiring adaptation of imaging protocols for high magnetic fields. This prospective study assesses the performance of three techniques for T1-weighted imaging (T1w) at 3.0 T with regard to gray-white differentiation and contrast-to-noise-ratio (CNR). Materials and Methods: Thirty-one patients were examined at a 3.0 T system with axial T1 w inversion recovery (IR), spin-echo (SE) and gradient echo (GE) sequences and after contrast enhancement (CE) with CE-SE and CE-GE sequences. For qualitative analysis, the images were ranked with regard to artifacts, gray-white differentiation, image noise and overall diagnostic quality. For quantitative analysis, the CNR was calculated, and cortex and basal ganglia were compared with the white matter. Results: In the qualitative analysis, IR was judged superior to SE and GE for gray-white differentiation, image noise and overall diagnostic quality, but inferior to the GE sequence with regard to artifacts. CE-GE proved superior to CE-SE in all categories. In the quantitative analysis, CNR of the based ganglia was highest for IR, followed by GE and SE. For the CNR of the cortex, no significant difference was found between IR (16.9) and GE (15.4) but both were superior to the SE (9.4). The CNR of the cortex was significantly higher for CE-GE compared to CE-SE (12.7 vs. 7.6, p<0.001), but the CNR of the basal ganglia was not significantly different. Conclusion: For unenhanced T1w imaging at 3.0 T, the IR technique is, despite increased artifacts, the method of choice due to its superior gray-white differentiation and best overall image quality. For CE-studies, GE sequences are recommended. For cerebral imaging, SE sequences give unsatisfactory results at 3.0 T. (orig.)
International Nuclear Information System (INIS)
Campion, T.; Turner, B.P.; Schmierer, K.; Smith, R.J.P.; Altmann, D.R.; Brito, G.C.; Evanson, J.; George, I.C.; Sati, P.; Reich, D.S.; Miquel, M.E.
2017-01-01
To explore the potential of a post-processing technique combining FLAIR and T 2 * (FLAIR*) to distinguish between lesions caused by multiple sclerosis (MS) from cerebral small vessel disease (SVD) in a clinical setting. FLAIR and T 2 * head datasets acquired at 3T of 25 people with relapsing MS (pwRMS) and ten with pwSVD were used. After post-processing, FLAIR* maps were used to determine the proportion of white matter lesions (WML) showing the 'vein in lesion' sign (VIL), a characteristic histopathological feature of MS plaques. Sensitivity and specificity of MS diagnosis were examined on the basis of >45% VIL + and >60% VIL + WML, and compared with current dissemination in space (DIS) MRI criteria. All pwRMS had >45% VIL + WML (range 58-100%) whilst in pwSVD the proportion of VIL + WML was significantly lower (0-64%; mean 32±20%). Sensitivity based on >45% VIL + was 100% and specificity 80% whilst with >60% VIL + as the criterion, sensitivity was 96% and specificity 90%. DIS criteria had 96% sensitivity and 40% specificity. FLAIR* enables VIL + WML detection in a clinical setting, facilitating differentiation of MS from SVD based on brain MRI. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Campion, T.; Turner, B.P.; Schmierer, K. [Queen Mary University of London, Blizard Institute (Neuroscience), London (United Kingdom); Barts Health NHS Trust, Emergency Care and Acute Medicine Clinical Academic Group Neuroscience, The Royal London Hospital, London (United Kingdom); Smith, R.J.P. [Queen Mary University of London, Blizard Institute (Neuroscience), London (United Kingdom); Gloucestershire Hospitals NHS Trust, Cheltenham (United Kingdom); Altmann, D.R. [London School of Hygiene and Tropical Medicine, Department of Medical Statistics, London (United Kingdom); Brito, G.C. [Queen Mary University of London, Blizard Institute (Neuroscience), London (United Kingdom); Evanson, J. [Barts Health NHS Trust, Emergency Care and Acute Medicine Clinical Academic Group Neuroscience, The Royal London Hospital, London (United Kingdom); George, I.C. [NIH, Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, Bethesda, MD (United States); Yale School of Medicine, Department of Neurology, New Haven, CT (United States); Sati, P.; Reich, D.S. [NIH, Translational Neuroradiology Section, National Institute of Neurological Disorders and Stroke, Bethesda, MD (United States); Miquel, M.E. [Barts Health NHS Trust, Emergency Care and Acute Medicine Clinical Academic Group Neuroscience, The Royal London Hospital, London (United Kingdom); Queen Mary University of London, William Harvey Research Institute (Cardiovascular Biomedical Research Unit), London (United Kingdom)
2017-10-15
To explore the potential of a post-processing technique combining FLAIR and T{sub 2}* (FLAIR*) to distinguish between lesions caused by multiple sclerosis (MS) from cerebral small vessel disease (SVD) in a clinical setting. FLAIR and T{sub 2}* head datasets acquired at 3T of 25 people with relapsing MS (pwRMS) and ten with pwSVD were used. After post-processing, FLAIR* maps were used to determine the proportion of white matter lesions (WML) showing the 'vein in lesion' sign (VIL), a characteristic histopathological feature of MS plaques. Sensitivity and specificity of MS diagnosis were examined on the basis of >45% VIL{sup +} and >60% VIL{sup +} WML, and compared with current dissemination in space (DIS) MRI criteria. All pwRMS had >45% VIL{sup +} WML (range 58-100%) whilst in pwSVD the proportion of VIL{sup +} WML was significantly lower (0-64%; mean 32±20%). Sensitivity based on >45% VIL{sup +} was 100% and specificity 80% whilst with >60% VIL{sup +} as the criterion, sensitivity was 96% and specificity 90%. DIS criteria had 96% sensitivity and 40% specificity. FLAIR* enables VIL{sup +} WML detection in a clinical setting, facilitating differentiation of MS from SVD based on brain MRI. (orig.)
Directory of Open Access Journals (Sweden)
Roberto Viviani
2017-05-01
Full Text Available While widely in use in automated segmentation approaches for the detection of group differences or of changes associated with continuous predictors in gray matter volume, T1-weighted images are known to represent dura and cortical vessels with signal intensities similar to those of gray matter. By considering multiple signal sources at once, multimodal segmentation approaches may be able to resolve these different tissue classes and address this potential confound. We explored here the simultaneous use of FLAIR and apparent transverse relaxation rates (a signal related to T2* relaxation maps and having similar contrast with T1-weighted images. Relative to T1-weighted images alone, multimodal segmentation had marked positive effects on 1. the separation of gray matter from dura, 2. the exclusion of vessels from the gray matter compartment, and 3. the contrast with extracerebral connective tissue. While obtainable together with the T1-weighted images without increasing scanning times, apparent transverse relaxation rates were less effective than added FLAIR images in providing the above mentioned advantages. FLAIR images also improved the detection of cortical matter in areas prone to susceptibility artifacts in standard MPRAGE T1-weighted images, while the addition of transverse relaxation maps exacerbated the effect of these artifacts on segmentation. Our results confirm that standard MPRAGE segmentation may overestimate gray matter volume by wrongly assigning vessels and dura to this compartment and show that multimodal approaches may greatly improve the specificity of cortical segmentation. Since multimodal segmentation is easily implemented, these benefits are immediately available to studies focusing on translational applications of structural imaging.
Baños, Rocío; Sokoli, Stavroula
2015-01-01
The purpose of this paper is to present the rationale and outcomes of ClipFlair, a European-funded project aimed at countering the factors that discourage Foreign Language Learning (FLL) by providing a motivating, easily accessible online platform to learn a foreign language through revoicing (e.g. dubbing) and captioning (e.g. subtitling). This…
Zerroug, A; Gabrillargues, J; Coll, G; Vassal, F; Jean, B; Chabert, E; Claise, B; Khalil, T; Sakka, L; Feschet, F; Durif, F; Boyer, L; Coste, J; Lemaire, J-J
2016-08-01
Deep brain mapping has been proposed for direct targeting in stereotactic functional surgery, aiming to personalize electrode implantation according to individual MRI anatomy without atlas or statistical template. We report our clinical experience of direct targeting in a series of 156 patients operated on using a dedicated Inversion Recovery Turbo Spin Echo sequence at 1.5-tesla, called White Matter Attenuated Inversion Recovery (WAIR). After manual contouring of all pertinent structures and 3D planning of trajectories, 312 DBS electrodes were implanted. Detailed anatomy of close neighbouring structures, whether gray nuclei or white matter regions, was identified during each planning procedure. We gathered the experience of these 312 deep brain mappings and elaborated consistent procedures of anatomical MRI mapping for pallidal, subthalamic and ventral thalamic regions. We studied the number of times the central track anatomically optimized was selected for implantation of definitive electrodes. WAIR sequence provided high-quality images of most common functional targets, successfully used for pure direct stereotactic targeting: the central track corresponding to the optimized primary anatomical trajectory was chosen for implantation of definitive electrodes in 90.38%. WAIR sequence is anatomically reliable, enabling precise deep brain mapping and direct stereotactic targeting under routine clinical conditions. Copyright © 2016 Elsevier Masson SAS. All rights reserved.
Lee, J I; Yoon, R G; Lee, J H; Park, J W; Yoo, M H; Ahn, J H; Chung, J W; Park, H J
2016-12-01
According to recent research, modern MR imaging can detect the presense of abnormalities on labyrinthine. Our aim was to report the patterns and prognostic role of abnormal findings on labyrinthine imaging in patients with sudden sensorineural hearing loss. This study comprised 113 patients who were diagnosed with unilateral sudden sensorineural hearing loss and underwent 3T MR imaging, including pre-/postcontrast 3D fluid-attenuated inversion recovery and T1-weighted imaging. We analyzed abnormalities on MR imaging and correlated them with audiometric results. Thirty-one (27%) patients showed abnormal findings on labyrinthine MR imaging in the affected ear. The initial/final hearing levels of the MRI+ group (91 ± 25/73 ± 27 dB hearing loss) were significantly worse than those of the MRI- group (69 ± 30/48 ± 24 dB hearing loss). The incidence of abnormalities on labyrinthine MR imaging was significantly lower (3 of 40, 8%) in 40 patients with initial mild-to-moderate hearing loss than in those with profound hearing loss (16 of 34, 47%). Considering hearing improvement by the Siegel criteria, the rate of complete or partial recovery was significantly higher in the MRI- group (34%) than in the MRI+ group (10%). In patients with initial severe or profound hearing loss, the MRI- group showed greater hearing improvement (38 ± 21 dB) than the MRI+ group (23 ± 22 dB). Abnormalities on labyrinthine MR imaging were found in 27% of patients with sudden sensorineural hearing loss. The initial hearing loss was worse in the MRI+ group than in the MRI- group. In patients with initial severe and profound hearing loss, the presence of abnormalities on labyrinthine MR imaging indicated a poor prognosis. © 2016 by American Journal of Neuroradiology.
International Nuclear Information System (INIS)
Namatame, Hirofumi; Taniguchi, Masaki
1994-01-01
Photoelectron spectroscopy is regarded as the most powerful means since it can measure almost perfectly the occupied electron state. On the other hand, inverse photoelectron spectroscopy is the technique for measuring unoccupied electron state by using the inverse process of photoelectron spectroscopy, and in principle, the similar experiment to photoelectron spectroscopy becomes feasible. The development of the experimental technology for inverse photoelectron spectroscopy has been carried out energetically by many research groups so far. At present, the heightening of resolution of inverse photoelectron spectroscopy, the development of inverse photoelectron spectroscope in which light energy is variable and so on are carried out. But the inverse photoelectron spectroscope for vacuum ultraviolet region is not on the market. In this report, the principle of inverse photoelectron spectroscopy and the present state of the spectroscope are described, and the direction of the development hereafter is groped. As the experimental equipment, electron guns, light detectors and so on are explained. As the examples of the experiment, the inverse photoelectron spectroscopy of semimagnetic semiconductors and resonance inverse photoelectron spectroscopy are reported. (K.I.)
DEFF Research Database (Denmark)
Nordlund, David; Heiberg, Einar; Carlsson, Marcus
2016-01-01
Background - Contrast-enhanced steady state free precession (CE-SSFP) and T2-weighted short tau inversion recovery (T2-STIR) have been clinically validated to estimate myocardium at risk (MaR) by cardiovascular magnetic resonance while using myocardial perfusion single-photon emission computed...... tomography as reference standard. Myocardial perfusion single-photon emission computed tomography has been used to describe the coronary perfusion territories during myocardial ischemia. Compared with myocardial perfusion single-photon emission computed tomography, cardiovascular magnetic resonance offers...... superior image quality and practical advantages. Therefore, the aim was to describe the main coronary perfusion territories using CE-SSFP and T2-STIR cardiovascular magnetic resonance data in patients after acute ST-segment-elevation myocardial infarction. Methods and Results - CE-SSFP and T2-STIR data...
Ingram, WT
2012-01-01
Inverse limits provide a powerful tool for constructing complicated spaces from simple ones. They also turn the study of a dynamical system consisting of a space and a self-map into a study of a (likely more complicated) space and a self-homeomorphism. In four chapters along with an appendix containing background material the authors develop the theory of inverse limits. The book begins with an introduction through inverse limits on [0,1] before moving to a general treatment of the subject. Special topics in continuum theory complete the book. Although it is not a book on dynamics, the influen
Vos, Sjoerd B; Micallef, Caroline; Barkhof, Frederik; Hill, Andrea; Winston, Gavin P; Ourselin, Sebastien; Duncan, John S
2018-03-02
T2-FLAIR is the single most sensitive MRI contrast to detect lesions underlying focal epilepsies but 3D sequences used to obtain isotropic high-resolution images are susceptible to motion artefacts. Prospective motion correction (PMC) - demonstrated to improve 3D-T1 image quality in a pediatric population - was applied to high-resolution 3D-T2-FLAIR scans in adult epilepsy patients to evaluate its clinical benefit. Coronal 3D-T2-FLAIR scans were acquired with a 1mm isotropic resolution on a 3T MRI scanner. Two expert neuroradiologists reviewed 40 scans without PMC and 40 with navigator-based PMC. Visual assessment addressed six criteria of image quality (resolution, SNR, WM-GM contrast, intensity homogeneity, lesion conspicuity, diagnostic confidence) on a seven-point Likert scale (from non-diagnostic to outstanding). SNR was also objectively quantified within the white matter. PMC scans had near-identical scores on the criteria of image quality to non-PMC scans, with the notable exception that intensity homogeneity was generally worse. Using PMC, the percentage of scans with bad image quality was substantially lower than without PMC (3.25% vs. 12.5%) on the other five criteria. Quantitative SNR estimates revealed that PMC and non-PMC had no significant difference in SNR (p=0.07). Application of prospective motion correction to 3D-T2-FLAIR sequences decreased the percentage of low-quality scans, reducing the number of scans that need to be repeated to obtain clinically useful data. Copyright © 2018. Published by Elsevier Masson SAS.
Directory of Open Access Journals (Sweden)
Kevin H. Boegel
Full Text Available Background and purpose: Evaluating chronic sequelae of optic neuritis, such as optic neuropathy with or without optic nerve atrophy, can be challenging on whole brain MRI. This study evaluated the utility of dedicated coronal contrast-enhanced fat-suppressed FLAIR (CE-FS-FLAIR MR imaging to detect optic neuropathy and optic nerve atrophy. Materials and methods: Over 4.5 years, a 3Â mm coronal CE-FS-FLAIR sequence at 1.5T was added to the routine brain MRIs of 124 consecutive patients, 102 of whom had suspected or known demyelinating disease. Retrospective record reviews confirmed that 28 of these 102 had documented onset of optic neuritis >4 weeks prior to the brain MRI. These 28 were compared to the other 22 (âcontrolsâ of the 124 patients who lacked a history of demyelinating disease or visual symptoms. Using coronal CE-FS-FLAIR, two neuroradiologists separately graded each optic nerve (nÂ =Â 50 patients, 100 total nerves as either negative, equivocal, or positive for optic neuropathy or atrophy. The scoring was later repeated. Results: The mean time from acute optic neuritis onset to MRI was 4.1Â Â±Â 4.6Â years (range 34Â days-17.4 years. Per individual nerve grading, the range of sensitivity, specificity, and accuracy of coronal CE-FS-FLAIR in detecting optic neuropathy was 71.4â77.1%, 93.8â95.4%, and 85.5â89.0%, respectively, with strong interobserver (kÂ =Â 0.667Â âÂ 0.678, pÂ <Â 0.0001, and intraobserver (kÂ =Â 0.706Â âÂ 0.763, pÂ <Â 0.0001 agreement. For optic atrophy, interobserver agreement was moderate (kÂ =Â 0.437Â âÂ 0.484, pÂ <Â 0.0001, while intraobserver agreement was moderate-strong (kÂ =Â 0.491Â âÂ 0.596, pÂ <Â 0.0001. Conclusion: Coronal CE-FS-FLAIR is quite specific in detecting optic neuropathy years after the onset of acute optic neuritis, but is less useful in detecting optic nerve atrophy. Keywords: Optic
Sasaki, M; Igarashi, K; Suzuki, S; Saito, K
1999-07-01
We report a patient of atypical type of Sturge-Weber syndrome who demonstrated a reversible change by MRI FLAIR method in ictus and postictal state. A 5-year-old boy was admitted to our hospital because of severe headache, vomiting and loss of consciousness with his eyes conjugated to left for a few minutes. He had no facial nevus and other abnormal findings in physical examination. CT scan showed two small calcifications in the right occipital lobe. Postcontrast T 1-weighted image of MRI demonstrated a right parieto-occipital leptomeningeal enhancement. We diagnosed this case as an atypical type of Sturge-Weber syndrome. Although, on admission, FLAIR method showed the area of high signal intensity, after anticonvulsant therapy, those abnormal area disappeared. It is presumably detected by FLAIR method slight extravasation of plasma element in the surface of the brain due to regional hyperperfusion in ictus.
Patel, Sohil H; Poisson, Laila M; Brat, Daniel J; Zhou, Yueren; Cooper, Lee; Snuderl, Matija; Thomas, Cheddhi; Franceschi, Ana M; Griffith, Brent; Flanders, Adam E; Golfinos, John G; Chi, Andrew S; Jain, Rajan
2017-10-15
Purpose: Lower-grade gliomas (WHO grade II/III) have been classified into clinically relevant molecular subtypes based on IDH and 1p/19q mutation status. The purpose was to investigate whether T2/FLAIR MRI features could distinguish between lower-grade glioma molecular subtypes. Experimental Design: MRI scans from the TCGA/TCIA lower grade glioma database ( n = 125) were evaluated by two independent neuroradiologists to assess (i) presence/absence of homogenous signal on T2WI; (ii) presence/absence of "T2-FLAIR mismatch" sign; (iii) sharp or indistinct lesion margins; and (iv) presence/absence of peritumoral edema. Metrics with moderate-substantial agreement underwent consensus review and were correlated with glioma molecular subtypes. Somatic mutation, DNA copy number, DNA methylation, gene expression, and protein array data from the TCGA lower-grade glioma database were analyzed for molecular-radiographic associations. A separate institutional cohort ( n = 82) was analyzed to validate the T2-FLAIR mismatch sign. Results: Among TCGA/TCIA cases, interreader agreement was calculated for lesion homogeneity [ κ = 0.234 (0.111-0.358)], T2-FLAIR mismatch sign [ κ = 0.728 (0.538-0.918)], lesion margins [ κ = 0.292 (0.135-0.449)], and peritumoral edema [ κ = 0.173 (0.096-0.250)]. All 15 cases that were positive for the T2-FLAIR mismatch sign were IDH -mutant, 1p/19q non-codeleted tumors ( P mismatch sign [ κ = 0.747 (0.536-0.958)]; all 10 cases positive for the T2-FLAIR mismatch sign were IDH -mutant, 1p/19q non-codeleted tumors ( P mismatch sign represents a highly specific imaging biomarker for the IDH -mutant, 1p/19q non-codeleted molecular subtype. Clin Cancer Res; 23(20); 6078-85. ©2017 AACR . ©2017 American Association for Cancer Research.
International Nuclear Information System (INIS)
Del C Valdes Hernandez, Maria; Ferguson, Karen J.; Chappell, Francesca M.; Wardlaw, Joanna M.
2010-01-01
Brain tissue segmentation by conventional threshold-based techniques may have limited accuracy and repeatability in older subjects. We present a new multispectral magnetic resonance (MR) image analysis approach for segmenting normal and abnormal brain tissue, including white matter lesions (WMLs). We modulated two 1.5T MR sequences in the red/green colour space and calculated the tissue volumes using minimum variance quantisation. We tested it on 14 subjects, mean age 73.3 ± 10 years, representing the full range of WMLs and atrophy. We compared the results of WML segmentation with those using FLAIR-derived thresholds, examined the effect of sampling location, WML amount and field inhomogeneities, and tested observer reliability and accuracy. FLAIR-derived thresholds were significantly affected by the location used to derive the threshold (P = 0.0004) and by WML volume (P = 0.0003), and had higher intra-rater variability than the multispectral technique (mean difference ± SD: 759 ± 733 versus 69 ± 326 voxels respectively). The multispectral technique misclassified 16 times fewer WMLs. Initial testing suggests that the multispectral technique is highly reproducible and accurate with the potential to be applied to routinely collected clinical MRI data. (orig.)
Yao, Xiu-Zhong; Yun, Hong; Zeng, Meng-Su; Wang, He; Sun, Fei; Rao, Sheng-Xiang; Ji, Yuan
2013-05-01
The objective of this paper was to investigate the value of apparent diffusion coefficients (ADCs) for differential diagnosis among solid pancreatic masses using respiratory triggered diffusion-weighted MR imaging with inversion-recovery fat-suppression technique (RT-IR-DWI) at 3.0 T. 20 normal volunteers and 72 patients (Pancreatic ductal adenocarcinoma [PDCA, n=30], mass-forming pancreatitis [MFP, n=15], solid pseudopapillary neoplasm [SPN, n=12], and pancreatic neuroendocrine tumor[PNET, n=15]) underwent RT-IR-DWI (b values: 0 and 600 s/mm(2)) at 3.0 T. Results were correlated with histopathologic data and follow-up imaging. ADC values among different types of pancreatic tissue were statistically analyzed and compared. Statistical difference was noticed in ADC values among normal pancreas, MFP, PDCA, SPN and PNET by ANOVA (pPDCA, MFP and SPN. There was noticeable statistical difference in ADC values among PDCA, MFP and normal pancreas by Least Significant Difference (LSD) (pPDCA (p=0.0300×10(-4)) and normal pancreas (p=0.0007×10(-4)). ADC of PNET was statistically lower than that of normal pancreas (p=0.0360) and higher than that of MFP (p=9.3000×10(-4)). ADC measurements using RT-IR-DWI at 3.0T may aid to disclose the histopathological pattern of normal pancreas and solid pancreatic masses, which may be helpful in characterizing solid pancreatic lesions. Copyright © 2013 Elsevier Inc. All rights reserved.
Hara, Naoyuki; Yunoki, Taijun; Kubo, Satoshi; Fujii, Hiroki; Takamatu, Kazuhiro; Tanaka, Akio; Kuriyama, Masaru
2015-01-01
A 66-year-old man was admitted to our hospital because of unconsciousness. He was diagnosed with pneumococcal meningitis and treated with a combination of antibiotics (meropenem hydrate), dexamethasone, and intravenous immunoglobulin. Although he gradually regained consciousness, he started showing signs of hearing disturbance. Measurement of auditory brainstem response revealed severe sensorineural hearing loss. The patient then underwent three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging, which revealed increased signals in the cochlea and the vestibuum, and their enhancement after gadolinium administration. This enhancement was still observed on images of the inner ear acquired on the 52nd hospital day. These findings suggested that the change of content in the lymph and the damage to the blood-labyrinth barrier was caused and aggravated by an immune response. Recent studies have shown that an MyD88-dependent immune response contributes to hearing loss in an experimental mouse model of pneumococcal meningitis. The patient was administered steroid pulse and hyperbaric oxygen therapies for improving the hearing deficit, but these therapies were discontinued because of the aggravation of hepatitis B and diabetes mellitus, which he had developed previously.
Lindig, Tobias; Kotikalapudi, Raviteja; Schweikardt, Daniel; Martin, Pascal; Bender, Friedemann; Klose, Uwe; Ernemann, Ulrike; Focke, Niels K; Bender, Benjamin
2018-04-15
Voxel-based morphometry is still mainly based on T1-weighted MRI scans. Misclassification of vessels and dura mater as gray matter has been previously reported. Goal of the present work was to evaluate the effect of multimodal segmentation methods available in SPM12, and their influence on identification of age related atrophy and lesion detection in epilepsy patients. 3D T1-, T2- and FLAIR-images of 77 healthy adults (mean age 35.8 years, 19-66 years, 45 females), 7 patients with malformation of cortical development (MCD) (mean age 28.1 years,19-40 years, 3 females), and 5 patients with left hippocampal sclerosis (LHS) (mean age 49.0 years, 25-67 years, 3 females) from a 3T scanner were evaluated. Segmentation based on T1-only, T1+T2, T1+FLAIR, T2+FLAIR, and T1+T2+FLAIR were compared in the healthy subjects. Clinical VBM results based on the different segmentation approaches for MCD and for LHS were compared. T1-only segmentation overestimated total intracranial volume by about 80ml compared to the other segmentation methods. This was due to misclassification of dura mater and vessels as GM and CSF. Significant differences were found for several anatomical regions: the occipital lobe, the basal ganglia/thalamus, the pre- and postcentral gyrus, the cerebellum, and the brainstem. None of the segmentation methods yielded completely satisfying results for the basal ganglia/thalamus and the brainstem. The best correlation with age could be found for the multimodal T1+T2+FLAIR segmentation. Highest T-scores for identification of LHS were found for T1+T2 segmentation, while highest T-scores for MCD were dependent on lesion and anatomical location. Multimodal segmentation is superior to T1-only segmentation and reduces the misclassification of dura mater and vessels as GM and CSF. Depending on the anatomical region and the pathology of interest (atrophy, lesion detection, etc.), different combinations of T1, T2 and FLAIR yield optimal results. Copyright © 2017 Elsevier
Inverse problems of geophysics
International Nuclear Information System (INIS)
Yanovskaya, T.B.
2003-07-01
This report gives an overview and the mathematical formulation of geophysical inverse problems. General principles of statistical estimation are explained. The maximum likelihood and least square fit methods, the Backus-Gilbert method and general approaches for solving inverse problems are discussed. General formulations of linearized inverse problems, singular value decomposition and properties of pseudo-inverse solutions are given
Directory of Open Access Journals (Sweden)
Halis Aygün
2008-01-01
Full Text Available We introduce definitions of fuzzy inverse compactness, fuzzy inverse countable compactness, and fuzzy inverse Lindelöfness on arbitrary -fuzzy sets in -fuzzy topological spaces. We prove that the proposed definitions are good extensions of the corresponding concepts in ordinary topology and obtain different characterizations of fuzzy inverse compactness.
Gawlitza, Matthias; Gragert, Jasmin; Quäschling, Ulf; Hoffmann, Karl Titus
2014-10-01
To investigate the relation between DWI-PWI mismatch and FLAIR-hyperintense vessel (FHV) sign and their influence on the prediction of the infarct growth in stroke patients without vessel recanalising therapy. Thirty-three patients with non-lacunar acute stroke and not eligible for recanalisation therapy received cerebral MRI at the day of admission and after 7±1 days. DWI and PWI lesion volumes, DWI-PWI mismatch volumes, infarct growth, relative mismatch and relative infarct growth were assessed. FHV sign was subdivided into (i) proximal or (ii) distal, the latter graded as either (i) prominent or (ii) subtle. FHV sign did not predict absolute or relative infarct growth. Significantly larger DWI lesions, PWI lesions and mismatch volumes were observed in FHV-positive infarcts. There were significant correlations between the degree of FHV sign and PWI lesion volume (r=0.52; Pmismatch volume (r=0.49; Pmismatch and relative infarct growth (r=0.91; Pmismatch volumes and infarct growth was evident (r=0.18, P=0.35). The FHV sign is associated with larger PWI lesion volumes and DWI-to-PWI mismatch volumes in acute stroke and thus seems to be an indicator of collateral flow. However, it is unsuitable to predict infarct growth. The latter occurred when DWI-to-PWI mismatches were present with bigger relative mismatch volumes making subsequent infarct growth more likely. Copyright © 2014 Elsevier Masson SAS. All rights reserved.
White, Carla Sabatino
2005-01-01
In the art lesson described in this article, students explore the arts of architecture, design, painting, and sculpture within four time periods: early colonial (1500-1700), late colonial (1700-1776), the quest for independence (1776-1860), and industrialization and growth (1860-1900). Through class discussion, readings, and slide presentations,…
Inverse Kinematics using Quaternions
DEFF Research Database (Denmark)
Henriksen, Knud; Erleben, Kenny; Engell-Nørregård, Morten
In this project I describe the status of inverse kinematics research, with the focus firmly on the methods that solve the core problem. An overview of the different methods are presented Three common methods used in inverse kinematics computation have been chosen as subject for closer inspection....
Inverse logarithmic potential problem
Cherednichenko, V G
1996-01-01
The Inverse and Ill-Posed Problems Series is a series of monographs publishing postgraduate level information on inverse and ill-posed problems for an international readership of professional scientists and researchers. The series aims to publish works which involve both theory and applications in, e.g., physics, medicine, geophysics, acoustics, electrodynamics, tomography, and ecology.
Inverse osmotic process for radioactive laundry waste
International Nuclear Information System (INIS)
Ebara, Katsuya; Takahashi, Sankichi; Sugimoto, Yoshikazu; Yusa, Hideo; Hyakutake, Hiroshi.
1977-01-01
Purpose: To effectively recover the processing amount reduced in a continuous treatment. Method: Laundry waste containing radioactive substances discharged from a nuclear power plant is processed in an inverse osmotic process while adding starch digesting enzymes such as amylase and takadiastase, as well as soft spherical bodies such as sponge balls of a particle diameter capable of flowing in the flow of the liquid wastes along the inverse osmotic membrane pipe and having such a softness and roundness as not to damage the inverse osmotic membrane. This process can remove the floating materials such as thread dusts or hairs deposited on the membrane surface by the action of the soft elastic balls and remove paste or the like through decomposition by the digesting enzymes. Consequently, effective recovery can be attained for the reduced processing amount. (Furukawa, Y.)
Disaster Debris Recovery Database - Recovery
U.S. Environmental Protection Agency — The US EPA Disaster Debris Recovery Database (DDRD) promotes the proper recovery, recycling, and disposal of disaster debris for emergency responders at the federal,...
International Nuclear Information System (INIS)
Burkhard, N.R.
1979-01-01
The gravity inversion code applies stabilized linear inverse theory to determine the topography of a subsurface density anomaly from Bouguer gravity data. The gravity inversion program consists of four source codes: SEARCH, TREND, INVERT, and AVERAGE. TREND and INVERT are used iteratively to converge on a solution. SEARCH forms the input gravity data files for Nevada Test Site data. AVERAGE performs a covariance analysis on the solution. This document describes the necessary input files and the proper operation of the code. 2 figures, 2 tables
Pakdaman, M N; Ishiyama, G; Ishiyama, A; Peng, K A; Kim, H J; Pope, W B; Sepahdari, A R
2016-06-02
Menière disease and idiopathic sudden sensorineural hearing loss can have overlapping clinical presentation and may have similar pathophysiology. Prior studies using postcontrast 3D-FLAIR MR imaging suggest abnormal blood-labyrinth barrier permeability in both conditions, but the 2 diseases have not been directly compared by using the same imaging techniques. We hypothesized that delayed postcontrast 3D-FLAIR MR imaging would show differences in blood-labyrinth barrier permeability between Menière disease and idiopathic sudden sensorineural hearing loss. Patients with unilateral Menière disease (n = 32) and unilateral idiopathic sudden sensorineural hearing loss (n = 11) imaged with delayed postcontrast 3D-FLAIR MR imaging were retrospectively studied. Signal intensities of the medulla and perilymph of the cochlear basal turns of both ears in each patient were measured in a blinded fashion. Cochlea/medulla ratios were calculated for each ear as a surrogate for blood-labyrinth barrier permeability. The ears were segregated by clinical diagnosis. Cochlea/medulla ratio was higher in symptomatic ears of patients with Menière disease (12.6 ± 7.4) than in patients with idiopathic sudden sensorineural hearing loss (5.7 ± 2.0) and asymptomatic ears of patients with Menière disease (8.0 ± 3.1), indicating increased blood-labyrinth barrier permeability in Menière disease ears. The differences in cochlea/medulla ratio between symptomatic and asymptomatic ears were significantly higher in Menière disease than in idiopathic sudden sensorineural hearing loss. Asymptomatic ears in patients with Menière disease showed higher cochlea/medulla ratio than symptomatic and asymptomatic ears in patients with idiopathic sudden sensorineural hearing loss. Increased cochlea/medulla ratio indicates increased blood-labyrinth barrier permeability in Menière disease compared with idiopathic sudden sensorineural hearing loss. Increased cochlea/medulla ratio in asymptomatic ears of
Sharp spatially constrained inversion
DEFF Research Database (Denmark)
Vignoli, Giulio G.; Fiandaca, Gianluca G.; Christiansen, Anders Vest C A.V.C.
2013-01-01
We present sharp reconstruction of multi-layer models using a spatially constrained inversion with minimum gradient support regularization. In particular, its application to airborne electromagnetic data is discussed. Airborne surveys produce extremely large datasets, traditionally inverted...... by using smoothly varying 1D models. Smoothness is a result of the regularization constraints applied to address the inversion ill-posedness. The standard Occam-type regularized multi-layer inversion produces results where boundaries between layers are smeared. The sharp regularization overcomes...... inversions are compared against classical smooth results and available boreholes. With the focusing approach, the obtained blocky results agree with the underlying geology and allow for easier interpretation by the end-user....
International Nuclear Information System (INIS)
Rosenwald, J.-C.
2008-01-01
The lecture addressed the following topics: Optimizing radiotherapy dose distribution; IMRT contributes to optimization of energy deposition; Inverse vs direct planning; Main steps of IMRT; Background of inverse planning; General principle of inverse planning; The 3 main components of IMRT inverse planning; The simplest cost function (deviation from prescribed dose); The driving variable : the beamlet intensity; Minimizing a 'cost function' (or 'objective function') - the walker (or skier) analogy; Application to IMRT optimization (the gradient method); The gradient method - discussion; The simulated annealing method; The optimization criteria - discussion; Hard and soft constraints; Dose volume constraints; Typical user interface for definition of optimization criteria; Biological constraints (Equivalent Uniform Dose); The result of the optimization process; Semi-automatic solutions for IMRT; Generalisation of the optimization problem; Driving and driven variables used in RT optimization; Towards multi-criteria optimization; and Conclusions for the optimization phase. (P.A.)
Submucous Myoma Induces Uterine Inversion
Directory of Open Access Journals (Sweden)
Yu-Li Chen
2006-06-01
Conclusion: Nonpuerperal inversion of the uterus is rarely encountered by gynecologists. Diagnosis of uterine inversion is often not easy and imaging studies might be helpful. Surgical treatment is the method of choice in nonpuerperal uterine inversion.
Postmortem verification of MS cortical lesion detection with 3D DIR
Seewann, A.M.; Kooi, E.J.; Roosendaal, S.D.; Pouwels, P.J.W.; Wattjes, M.P.; van der Valk, P.; Barkhof, F.; Polman, C.H.; Geurts, J.J.G.
2012-01-01
Objective: To assess the sensitivity and specificity of 3D double inversion recovery (DIR) MRI for detecting multiple sclerosis (MS) cortical lesions (CLs) using a direct postmortem MRI to histopathology comparison. Methods: Single-slab 3D DIR and 3D fluid-attenuated inversion recovery (FLAIR)
DEFF Research Database (Denmark)
Skov Jensen, Christian; Lando, David; Heje Pedersen, Lasse
of Ross (2015). Our characterization is simple and intuitive, linking recovery to the relation between the number of time periods on the number of states. When recovery is feasible, our model is easy to implement, allowing a closed-form linearized solution. We implement our model empirically, testing...... the predictive power of the recovered expected return, crash risk, and other recovered statistics....
Preston, W
2009-01-01
Packed with practical, freely available backup and recovery solutions for Unix, Linux, Windows, and Mac OS X systems -- as well as various databases -- this new guide is a complete overhaul of Unix Backup & Recovery by the same author, now revised and expanded with over 75% new material.
Inverse scale space decomposition
DEFF Research Database (Denmark)
Schmidt, Marie Foged; Benning, Martin; Schönlieb, Carola-Bibiane
2018-01-01
We investigate the inverse scale space flow as a decomposition method for decomposing data into generalised singular vectors. We show that the inverse scale space flow, based on convex and even and positively one-homogeneous regularisation functionals, can decompose data represented...... by the application of a forward operator to a linear combination of generalised singular vectors into its individual singular vectors. We verify that for this decomposition to hold true, two additional conditions on the singular vectors are sufficient: orthogonality in the data space and inclusion of partial sums...... of the subgradients of the singular vectors in the subdifferential of the regularisation functional at zero. We also address the converse question of when the inverse scale space flow returns a generalised singular vector given that the initial data is arbitrary (and therefore not necessarily in the range...
Inversion assuming weak scattering
DEFF Research Database (Denmark)
Xenaki, Angeliki; Gerstoft, Peter; Mosegaard, Klaus
2013-01-01
due to the complex nature of the field. A method based on linear inversion is employed to infer information about the statistical properties of the scattering field from the obtained cross-spectral matrix. A synthetic example based on an active high-frequency sonar demonstrates that the proposed...
Broekhuis, H.
2005-01-01
This article aims at reformulating in more current terms Hoekstra and Mulder’s (1990) analysis of the Locative Inversion (LI) construction. The new proposal is crucially based on the assumption that Small Clause (SC) predicates agree with their external argument in phi-features, which may be
Bayesian seismic AVO inversion
Energy Technology Data Exchange (ETDEWEB)
Buland, Arild
2002-07-01
A new linearized AVO inversion technique is developed in a Bayesian framework. The objective is to obtain posterior distributions for P-wave velocity, S-wave velocity and density. Distributions for other elastic parameters can also be assessed, for example acoustic impedance, shear impedance and P-wave to S-wave velocity ratio. The inversion algorithm is based on the convolutional model and a linearized weak contrast approximation of the Zoeppritz equation. The solution is represented by a Gaussian posterior distribution with explicit expressions for the posterior expectation and covariance, hence exact prediction intervals for the inverted parameters can be computed under the specified model. The explicit analytical form of the posterior distribution provides a computationally fast inversion method. Tests on synthetic data show that all inverted parameters were almost perfectly retrieved when the noise approached zero. With realistic noise levels, acoustic impedance was the best determined parameter, while the inversion provided practically no information about the density. The inversion algorithm has also been tested on a real 3-D dataset from the Sleipner Field. The results show good agreement with well logs but the uncertainty is high. The stochastic model includes uncertainties of both the elastic parameters, the wavelet and the seismic and well log data. The posterior distribution is explored by Markov chain Monte Carlo simulation using the Gibbs sampler algorithm. The inversion algorithm has been tested on a seismic line from the Heidrun Field with two wells located on the line. The uncertainty of the estimated wavelet is low. In the Heidrun examples the effect of including uncertainty of the wavelet and the noise level was marginal with respect to the AVO inversion results. We have developed a 3-D linearized AVO inversion method with spatially coupled model parameters where the objective is to obtain posterior distributions for P-wave velocity, S
Energy Technology Data Exchange (ETDEWEB)
Shin, Chang Soo; Park, Keun Pil [Korea Inst. of Geology Mining and Materials, Taejon (Korea, Republic of); Suh, Jung Hee; Hyun, Byung Koo; Shin, Sung Ryul [Seoul National University, Seoul (Korea, Republic of)
1995-12-01
The seismic reflection exploration technique which is one of the geophysical methods for oil exploration became effectively to image the subsurface structure with rapid development of computer. However, the imagining of subsurface based on the conventional data processing is almost impossible to obtain the information on physical properties of the subsurface such as velocity and density. Since seismic data are implicitly function of velocities of subsurface, it is necessary to develop the inversion method that can delineate the velocity structure using seismic topography and waveform inversion. As a tool to perform seismic inversion, seismic forward modeling program using ray tracing should be developed. In this study, we have developed the algorithm that calculate the travel time of the complex geologic structure using shooting ray tracing by subdividing the geologic model into blocky structure having the constant velocity. With the travel time calculation, the partial derivatives of travel time can be calculated efficiently without difficulties. Since the current ray tracing technique has a limitation to calculate the travel times for extremely complex geologic model, our aim in the future is to develop the powerful ray tracer using the finite element technique. After applying the pseudo waveform inversion to the seismic data of Korea offshore, we can obtain the subsurface velocity model and use the result in bring up the quality of the seismic data processing. If conventional seismic data processing and seismic interpretation are linked with this inversion technique, the high quality of seismic data processing can be expected to image the structure of the subsurface. Future research area is to develop the powerful ray tracer of ray tracing which can calculate the travel times for the extremely complex geologic model. (author). 39 refs., 32 figs., 2 tabs.
Calculation of the inverse data space via sparse inversion
Saragiotis, Christos
2011-01-01
The inverse data space provides a natural separation of primaries and surface-related multiples, as the surface multiples map onto the area around the origin while the primaries map elsewhere. However, the calculation of the inverse data is far from trivial as theory requires infinite time and offset recording. Furthermore regularization issues arise during inversion. We perform the inversion by minimizing the least-squares norm of the misfit function by constraining the $ell_1$ norm of the solution, being the inverse data space. In this way a sparse inversion approach is obtained. We show results on field data with an application to surface multiple removal.
Directory of Open Access Journals (Sweden)
Verscheure M.
2012-06-01
Full Text Available For oil recovery or CO2 storage, “reservoirs” are commonly used to designate geological structures where oil can be found or CO2 can be stored. All reservoirs present a heterogeneity in terms of rock type and properties (such as porosity and permeability. In addition, some of these reservoirs present fractures and faults. Fractured reservoirs are an important part of the oil reserves in the world (Middle East, Gulf of Mexico, etc. and some of them are important reservoirs in terms of oil volume and productivity in spite of the fractures. In addition, studies of reservoirs for geologic storage of CO2 have shown the existence of diffuse fractures and faults and their strong impacts on flow. A key point in fractured reservoirs is to understand the geometry and hydraulic conductivity of the network formed by the fractures. This requires the construction of a reservoir model that integrates all available conceptual knowledge and quantitative data. The topic of the present paper deals with a new methodology able to perform the history matching of a fractured reservoir model by adapting the sub-seismic fault properties and positions. The main difficulty of this work is to generate a sub-seismic fault network whose fault positions can be easily modified while respecting the statistical fault model. The sub-seismic fault model we have chosen allows us to obtain a sub-seismic fault network that is consistent with the seismic fault network and that succeeds in capturing the specific spatial organization of the faults. In a first step, the geometry of the seismic fault network is characterized using fractal methods. Sub-seismic faults are then generated according to a stochastic algorithm. Finally, the geometry of this discrete fracture network is optimized in order to match the hydrodynamic data about the reservoir. The optimization algorithm modifies the sub-seismic fault positions, leading to the history matching of the reservoir model. Fractal
Energy Technology Data Exchange (ETDEWEB)
Pichler, Josef, E-mail: josef.pichler@gespag.at [Wagner Jauregg Weg 15, 4020 Linz, Landesnervenklinik Linz (Austria); Pachinger, Corinna, E-mail: pachingercorinna@gmx.at [Wagner Jauregg Weg 15, 4020 Linz, Landesnervenklinik Linz (Austria); Pelz, Manuela, E-mail: mauela.pelz@gespag.at [Wagner Jauregg Weg 15, 4020 Linz, Landesnervenklinik Linz (Austria); Kleiser, Raimund, E-mail: raimund.kleiser@gespag.at [Wagner Jauregg Weg 15, 4020 Linz, Landesnervenklinik Linz (Austria)
2013-05-15
Purpose: To develop a magnetic resonance imaging (MRI) metric that is useful for therapy monitoring in patients with relapsed glioblastoma (GBM) during treatment with the antiangiogenic monoclonal antibody bevacizumab (Bev). We evaluated the feasibility of tumour volume measurement with our software tool in clinical routine and tried to establish reproducible and quantitative parameters for surveillance of patients on treatment with antiangiogenic drugs. Materials and methods: In this retrospective institutional pilot study, 18 patients (11 men, 7 women; mean age 53.5) with recurrent GBM received bevacizumab and irinotecan every two weeks as second line therapy. Follow up scans were assessed every two to four months. Data were collected on a 1.5 T MR System (Siemens, Symphony) with the standard head coil using our standardized tumour protocol. Volumetric measurement was performed with a commercial available software stroketool in FLAIR and T1-c imaging with following procedure: Pre-processing involved cutting noise and electing a Gaussian of 3 × 3 to smooth images, selecting a ROI (region of interest) in healthy brain area of the contra lateral side with quantifying the intensity value, adding 20% to this value to define the threshold level. Only values above this threshold are left corresponding to the tumour lesion. For the volumetric measurement the detected tumour area was circuited in all slices and finally summing up all values and multiplied by slice thickness to get the whole volume. Results: With McDonalds criteria progression was indicated in 14 out of 18 patients. In contrast, volumetric measurement showed an increase of contrast enhancement of >25%, defined as threshold for progression, in 11 patients (78%) and in 12 patients (85%) in FLAIR volume, respectively. 6 patients revealed that volumes in MRI increased earlier than the last scan, which was primarily defined as the date of progression with McDonald criteria, changing PFS after re-evaluation of
Electrochemically driven emulsion inversion
International Nuclear Information System (INIS)
Johans, Christoffer; Kontturi, Kyoesti
2007-01-01
It is shown that emulsions stabilized by ionic surfactants can be inverted by controlling the electrical potential across the oil-water interface. The potential dependent partitioning of sodium dodecyl sulfate (SDS) was studied by cyclic voltammetry at the 1,2-dichlorobenzene|water interface. In the emulsion the potential control was achieved by using a potential-determining salt. The inversion of a 1,2-dichlorobenzene-in-water (O/W) emulsion stabilized by SDS was followed by conductometry as a function of added tetrapropylammonium chloride. A sudden drop in conductivity was observed, indicating the change of the continuous phase from water to 1,2-dichlorobenzene, i.e. a water-in-1,2-dichlorobenzene emulsion was formed. The inversion potential is well in accordance with that predicted by the hydrophilic-lipophilic deviation if the interfacial potential is appropriately accounted for
DEFF Research Database (Denmark)
Gale, A.S.; Surlyk, Finn; Anderskouv, Kresten
2013-01-01
Evidence from regional stratigraphical patterns in Santonian−Campanian chalk is used to infer the presence of a very broad channel system (5 km across) with a depth of at least 50 m, running NNW−SSE across the eastern Isle of Wight; only the western part of the channel wall and fill is exposed. W......−Campanian chalks in the eastern Isle of Wight, involving penecontemporaneous tectonic inversion of the underlying basement structure, are rejected....
Intersections, ideals, and inversion
International Nuclear Information System (INIS)
Vasco, D.W.
1998-01-01
Techniques from computational algebra provide a framework for treating large classes of inverse problems. In particular, the discretization of many types of integral equations and of partial differential equations with undetermined coefficients lead to systems of polynomial equations. The structure of the solution set of such equations may be examined using algebraic techniques.. For example, the existence and dimensionality of the solution set may be determined. Furthermore, it is possible to bound the total number of solutions. The approach is illustrated by a numerical application to the inverse problem associated with the Helmholtz equation. The algebraic methods are used in the inversion of a set of transverse electric (TE) mode magnetotelluric data from Antarctica. The existence of solutions is demonstrated and the number of solutions is found to be finite, bounded from above at 50. The best fitting structure is dominantly one dimensional with a low crustal resistivity of about 2 ohm-m. Such a low value is compatible with studies suggesting lower surface wave velocities than found in typical stable cratons
Intersections, ideals, and inversion
Energy Technology Data Exchange (ETDEWEB)
Vasco, D.W.
1998-10-01
Techniques from computational algebra provide a framework for treating large classes of inverse problems. In particular, the discretization of many types of integral equations and of partial differential equations with undetermined coefficients lead to systems of polynomial equations. The structure of the solution set of such equations may be examined using algebraic techniques.. For example, the existence and dimensionality of the solution set may be determined. Furthermore, it is possible to bound the total number of solutions. The approach is illustrated by a numerical application to the inverse problem associated with the Helmholtz equation. The algebraic methods are used in the inversion of a set of transverse electric (TE) mode magnetotelluric data from Antarctica. The existence of solutions is demonstrated and the number of solutions is found to be finite, bounded from above at 50. The best fitting structure is dominantly onedimensional with a low crustal resistivity of about 2 ohm-m. Such a low value is compatible with studies suggesting lower surface wave velocities than found in typical stable cratons.
International Nuclear Information System (INIS)
Steinhauer, L.C.; Romea, R.D.; Kimura, W.D.
1997-01-01
A new method for laser acceleration is proposed based upon the inverse process of transition radiation. The laser beam intersects an electron-beam traveling between two thin foils. The principle of this acceleration method is explored in terms of its classical and quantum bases and its inverse process. A closely related concept based on the inverse of diffraction radiation is also presented: this concept has the significant advantage that apertures are used to allow free passage of the electron beam. These concepts can produce net acceleration because they do not satisfy the conditions in which the Lawson-Woodward theorem applies (no net acceleration in an unbounded vacuum). Finally, practical aspects such as damage limits at optics are employed to find an optimized set of parameters. For reasonable assumptions an acceleration gradient of 200 MeV/m requiring a laser power of less than 1 GW is projected. An interesting approach to multi-staging the acceleration sections is also presented. copyright 1997 American Institute of Physics
Reginold, William; Luedke, Angela C.; Tam, Angela; Itorralba, Justine; Fernandez-Ruiz, Juan; Reginold, Jennifer; Islam, Omar; Garcia, Angeles
2015-01-01
Background/Aims: This study used 3-Tesla magnetic resonance imaging (MRI) tractography to determine if there was an association between tracts crossing white matter hyperintensities (WMH) and cognitive function in elderly persons. Methods: Brain T2-weighted fluid-attenuated inversion recovery (FLAIR) and diffusion tensor MRI scans were acquired in participants above the age of 60 years. Twenty-six persons had WMH identified on T2 FLAIR scans. They completed a battery of neuropsychological tes...
Directory of Open Access Journals (Sweden)
Ernest Kurtz
2015-01-01
Full Text Available There is growing interest in Alcoholics Anonymous (A.A. and other secular, spiritual, and religious frameworks of long-term addiction recovery. The present paper explores the varieties of spiritual experience within A.A., with particular reference to the growth of a wing of recovery spirituality promoted within A.A. It is suggested that the essence of secular spirituality is reflected in the experience of beyond (horizontal and vertical transcendence and between (connection and mutuality and in six facets of spirituality (Release, Gratitude, Humility, Tolerance, Forgiveness, and a Sense of Being-at-home shared across religious, spiritual, and secular pathways of addiction recovery. The growing varieties of A.A. spirituality (spanning the “Christianizers” and “Seculizers” reflect A.A.’s adaptation to the larger diversification of religious experience and the growing secularization of spirituality across the cultural contexts within which A.A. is nested.
Directory of Open Access Journals (Sweden)
Lupe Romero
2016-01-01
Full Text Available Abstract – The purpose of this paper is to present the Clipflair project, a web platform for foreign language learning (FLL through revoicing and captioning of clips. Using audiovisual material in the language classroom is a common resource for teachers since it introduces variety, provides exposure to nonverbal cultural elements and, most importantly, presents linguistic and cultural aspects of communication in their context. However, teachers using this resource face the difficulty of finding active tasks that will engage learners and discourage passive viewing. ClipFlair proposes working with AV material productively while also motivating learners by getting them to revoice or caption a clip. Revoicing is a term used to refer to (rerecording voice onto a clip, as in dubbing, free commentary, audio description and karaoke singing. The term captioning refers to adding written text to a clip, such as standard subtitles, annotations and intertitles. Clips can be short video or audio files, including documentaries, film scenes, news pieces, animations and songs. ClipFlair develops materials that enable foreign language learners to practice all four standard CEFR skills: writing, speaking, listening and reading. Within the project’s scope, more than 350 ready-made activities, which involve captioning and/or revoicing of clips, has been created. These activities has been created for more than 16 languages including English, Spanish and Italian, but focus is placed on less widely taught languages, namely Estonian, Greek, Romanian and Polish, as well as minority languages, i.e. Basque, Catalan and Irish. Non-European languages, namely Arabic, Chinese, Japanese, Russian and Ukrainian are also included. The platform has three different areas: The Gallery offers the materials and the activities; the Studio area, offers a captioning and revoicing tools, in order to create or practice and learn languages by using the activities; the Social Network area
DEFF Research Database (Denmark)
Skov Jensen, Christian; Lando, David; Heje Pedersen, Lasse
We characterize when physical probabilities, marginal utilities, and the discount rate can be recovered from observed state prices for several future time periods. Our characterization makes no assumptions of the probability distribution, thus generalizing the time-homogeneous stationary model...... of Ross (2015). Our characterization is simple and intuitive, linking recovery to the relation between the number of time periods and the number of states. When recovery is feasible, our model is easy to implement, allowing a closed-form linearized solution. We implement our model empirically, testing...
DEFF Research Database (Denmark)
Jensen, Christian Skov; Lando, David; Pedersen, Lasse Heje
We characterize when physical probabilities, marginal utilities, and the discount rate can be recovered from observed state prices for several future time periods. Our characterization makes no assumptions of the probability distribution, thus generalizing the time-homogeneous stationary model...... of Ross (2015). Our characterization is simple and intuitive, linking recovery to the relation between the number of time periods on the number of states. When recovery is feasible, our model is easy to implement, allowing a closed-form linearized solution. We implement our model empirically, testing...
DEFF Research Database (Denmark)
Jensen, Christian Skov; Lando, David; Pedersen, Lasse Heje
We characterize when physical probabilities, marginal utilities, and the discount rate can be recovered from observed state prices for several future time periods. We make no assumptions of the probability distribution, thus generalizing the time-homogeneous stationary model of Ross (2015......). Recovery is feasible when the number of maturities with observable prices is higher than the number of states of the economy (or the number of parameters characterizing the pricing kernel). When recovery is feasible, our model is easy to implement, allowing a closed-form linearized solution. We implement...... our model empirically, testing the predictive power of the recovered expected return and other recovered statistics....
DEFF Research Database (Denmark)
Mosegaard, Klaus
2012-01-01
For non-linear inverse problems, the mathematical structure of the mapping from model parameters to data is usually unknown or partly unknown. Absence of information about the mathematical structure of this function prevents us from presenting an analytical solution, so our solution depends on our...... ability to produce efficient search algorithms. Such algorithms may be completely problem-independent (which is the case for the so-called 'meta-heuristics' or 'blind-search' algorithms), or they may be designed with the structure of the concrete problem in mind. We show that pure meta...
International Nuclear Information System (INIS)
Hicks, H.R.; Dory, R.A.; Holmes, J.A.
1983-01-01
We illustrate in some detail a 2D inverse-equilibrium solver that was constructed to analyze tokamak configurations and stellarators (the latter in the context of the average method). To ensure that the method is suitable not only to determine equilibria, but also to provide appropriately represented data for existing stability codes, it is important to be able to control the Jacobian, tilde J is identical to delta(R,Z)/delta(rho, theta). The form chosen is tilde J = J 0 (rho)R/sup l/rho where rho is a flux surface label, and l is an integer. The initial implementation is for a fixed conducting-wall boundary, but the technique can be extended to a free-boundary model
A passive inverse filter for Green's function retrieval.
Gallot, Thomas; Catheline, Stefan; Roux, Philippe; Campillo, Michel
2012-01-01
Passive methods for the recovery of Green's functions from ambient noise require strong hypotheses, including isotropic distribution of the noise sources. Very often, this distribution is nonisotropic, which introduces bias in the Green's function reconstruction. To minimize this bias, a spatiotemporal inverse filter is proposed. The method is tested on a directive noise field computed from an experimental active seismic data set. The results indicate that the passive inverse filter allows the manipulation of the spatiotemporal degrees of freedom of a complex wave field, and it can efficiently compensate for the noise wavefield directivity. © 2012 Acoustical Society of America.
Holocaust inversion and contemporary antisemitism.
Klaff, Lesley D
2014-01-01
One of the cruellest aspects of the new antisemitism is its perverse use of the Holocaust as a stick to beat 'the Jews'. This article explains the phenomenon of 'Holocaust Inversion', which involves an 'inversion of reality' (the Israelis are cast as the 'new' Nazis and the Palestinians as the 'new' Jews) and an 'inversion of morality' (the Holocaust is presented as a moral lesson for, or even a moral indictment of, 'the Jews'). Holocaust inversion is a form of soft-core Holocaust denial, yet...
Inverse feasibility problems of the inverse maximum flow problems
Indian Academy of Sciences (India)
A linear time method to decide if any inverse maximum ﬂow (denoted General Inverse Maximum Flow problems (IMFG)) problem has solution is deduced. If IMFG does not have solution, methods to transform IMFG into a feasible problem are presented. The methods consist of modifying as little as possible the restrictions to ...
Inverse feasibility problems of the inverse maximum flow problems
Indian Academy of Sciences (India)
199–209. c Indian Academy of Sciences. Inverse feasibility problems of the inverse maximum flow problems. ADRIAN DEACONU. ∗ and ELEONOR CIUREA. Department of Mathematics and Computer Science, Faculty of Mathematics and Informatics, Transilvania University of Brasov, Brasov, Iuliu Maniu st. 50,. Romania.
Inverse problem in hydrogeology
Carrera, Jesús; Alcolea, Andrés; Medina, Agustín; Hidalgo, Juan; Slooten, Luit J.
2005-03-01
The state of the groundwater inverse problem is synthesized. Emphasis is placed on aquifer characterization, where modelers have to deal with conceptual model uncertainty (notably spatial and temporal variability), scale dependence, many types of unknown parameters (transmissivity, recharge, boundary conditions, etc.), nonlinearity, and often low sensitivity of state variables (typically heads and concentrations) to aquifer properties. Because of these difficulties, calibration cannot be separated from the modeling process, as it is sometimes done in other fields. Instead, it should be viewed as one step in the process of understanding aquifer behavior. In fact, it is shown that actual parameter estimation methods do not differ from each other in the essence, though they may differ in the computational details. It is argued that there is ample room for improvement in groundwater inversion: development of user-friendly codes, accommodation of variability through geostatistics, incorporation of geological information and different types of data (temperature, occurrence and concentration of isotopes, age, etc.), proper accounting of uncertainty, etc. Despite this, even with existing codes, automatic calibration facilitates enormously the task of modeling. Therefore, it is contended that its use should become standard practice. L'état du problème inverse des eaux souterraines est synthétisé. L'accent est placé sur la caractérisation de l'aquifère, où les modélisateurs doivent jouer avec l'incertitude des modèles conceptuels (notamment la variabilité spatiale et temporelle), les facteurs d'échelle, plusieurs inconnues sur différents paramètres (transmissivité, recharge, conditions aux limites, etc.), la non linéarité, et souvent la sensibilité de plusieurs variables d'état (charges hydrauliques, concentrations) des propriétés de l'aquifère. A cause de ces difficultés, le calibrage ne peut êtreséparé du processus de modélisation, comme c'est le
Face inversion increases attractiveness.
Leder, Helmut; Goller, Juergen; Forster, Michael; Schlageter, Lena; Paul, Matthew A
2017-07-01
Assessing facial attractiveness is a ubiquitous, inherent, and hard-wired phenomenon in everyday interactions. As such, it has highly adapted to the default way that faces are typically processed: viewing faces in upright orientation. By inverting faces, we can disrupt this default mode, and study how facial attractiveness is assessed. Faces, rotated at 90 (tilting to either side) and 180°, were rated on attractiveness and distinctiveness scales. For both orientations, we found that faces were rated more attractive and less distinctive than upright faces. Importantly, these effects were more pronounced for faces rated low in upright orientation, and smaller for highly attractive faces. In other words, the less attractive a face was, the more it gained in attractiveness by inversion or rotation. Based on these findings, we argue that facial attractiveness assessments might not rely on the presence of attractive facial characteristics, but on the absence of distinctive, unattractive characteristics. These unattractive characteristics are potentially weighed against an individual, attractive prototype in assessing facial attractiveness. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.
Zhang, Dongliang
2013-01-01
To increase the illumination of the subsurface and to eliminate the dependency of FWI on the source wavelet, we propose multiples waveform inversion (MWI) that transforms each hydrophone into a virtual point source with a time history equal to that of the recorded data. These virtual sources are used to numerically generate downgoing wavefields that are correlated with the backprojected surface-related multiples to give the migration image. Since the recorded data are treated as the virtual sources, knowledge of the source wavelet is not required, and the subsurface illumination is greatly enhanced because the entire free surface acts as an extended source compared to the radiation pattern of a traditional point source. Numerical tests on the Marmousi2 model show that the convergence rate and the spatial resolution of MWI is, respectively, faster and more accurate then FWI. The potential pitfall with this method is that the multiples undergo more than one roundtrip to the surface, which increases attenuation and reduces spatial resolution. This can lead to less resolved tomograms compared to conventional FWI. The possible solution is to combine both FWI and MWI in inverting for the subsurface velocity distribution.
Coin tossing and Laplace inversion
Indian Academy of Sciences (India)
MS received 5 May 1999; revised 3 April 2000. Abstract. An analysis of exchangeable sequences of coin tossings leads to inversion formulae for Laplace transforms of probability measures. Keywords. Laplace inversion; moment problem; exchangeable probabilities. 1. Introduction. There is an intimate relationship between ...
Inverse problems for Maxwell's equations
Romanov, V G
1994-01-01
The Inverse and Ill-Posed Problems Series is a series of monographs publishing postgraduate level information on inverse and ill-posed problems for an international readership of professional scientists and researchers. The series aims to publish works which involve both theory and applications in, e.g., physics, medicine, geophysics, acoustics, electrodynamics, tomography, and ecology.
Algebraic properties of generalized inverses
Cvetković‐Ilić, Dragana S
2017-01-01
This book addresses selected topics in the theory of generalized inverses. Following a discussion of the “reverse order law” problem and certain problems involving completions of operator matrices, it subsequently presents a specific approach to solving the problem of the reverse order law for {1} -generalized inverses. Particular emphasis is placed on the existence of Drazin invertible completions of an upper triangular operator matrix; on the invertibility and different types of generalized invertibility of a linear combination of operators on Hilbert spaces and Banach algebra elements; on the problem of finding representations of the Drazin inverse of a 2x2 block matrix; and on selected additive results and algebraic properties for the Drazin inverse. In addition to the clarity of its content, the book discusses the relevant open problems for each topic discussed. Comments on the latest references on generalized inverses are also included. Accordingly, the book will be useful for graduate students, Ph...
Directory of Open Access Journals (Sweden)
Calvez V.
2010-12-01
Full Text Available We consider the radiative transfer equation (RTE with reflection in a three-dimensional domain, infinite in two dimensions, and prove an existence result. Then, we study the inverse problem of retrieving the optical parameters from boundary measurements, with help of existing results by Choulli and Stefanov. This theoretical analysis is the framework of an attempt to model the color of the skin. For this purpose, a code has been developed to solve the RTE and to study the sensitivity of the measurements made by biophysicists with respect to the physiological parameters responsible for the optical properties of this complex, multi-layered material. On étudie l’équation du transfert radiatif (ETR dans un domaine tridimensionnel infini dans deux directions, et on prouve un résultat d’existence. On s’intéresse ensuite à la reconstruction des paramètres optiques à partir de mesures faites au bord, en s’appuyant sur des résultats de Choulli et Stefanov. Cette analyse sert de cadre théorique à un travail de modélisation de la couleur de la peau. Dans cette perspective, un code à été développé pour résoudre l’ETR et étudier la sensibilité des mesures effectuées par les biophysiciens par rapport aux paramètres physiologiques tenus pour responsables des propriétés optiques de ce complexe matériau multicouche.
Bayesian Approach to Inverse Problems
2008-01-01
Many scientific, medical or engineering problems raise the issue of recovering some physical quantities from indirect measurements; for instance, detecting or quantifying flaws or cracks within a material from acoustic or electromagnetic measurements at its surface is an essential problem of non-destructive evaluation. The concept of inverse problems precisely originates from the idea of inverting the laws of physics to recover a quantity of interest from measurable data.Unfortunately, most inverse problems are ill-posed, which means that precise and stable solutions are not easy to devise. Regularization is the key concept to solve inverse problems.The goal of this book is to deal with inverse problems and regularized solutions using the Bayesian statistical tools, with a particular view to signal and image estimation
Testing earthquake source inversion methodologies
Page, Morgan T.
2011-01-01
Source Inversion Validation Workshop; Palm Springs, California, 11-12 September 2010; Nowadays earthquake source inversions are routinely performed after large earthquakes and represent a key connection between recorded seismic and geodetic data and the complex rupture process at depth. The resulting earthquake source models quantify the spatiotemporal evolution of ruptures. They are also used to provide a rapid assessment of the severity of an earthquake and to estimate losses. However, because of uncertainties in the data, assumed fault geometry and velocity structure, and chosen rupture parameterization, it is not clear which features of these source models are robust. Improved understanding of the uncertainty and reliability of earthquake source inversions will allow the scientific community to use the robust features of kinematic inversions to more thoroughly investigate the complexity of the rupture process and to better constrain other earthquakerelated computations, such as ground motion simulations and static stress change calculations.
Parameter estimation and inverse problems
Aster, Richard C; Thurber, Clifford H
2005-01-01
Parameter Estimation and Inverse Problems primarily serves as a textbook for advanced undergraduate and introductory graduate courses. Class notes have been developed and reside on the World Wide Web for faciliting use and feedback by teaching colleagues. The authors'' treatment promotes an understanding of fundamental and practical issus associated with parameter fitting and inverse problems including basic theory of inverse problems, statistical issues, computational issues, and an understanding of how to analyze the success and limitations of solutions to these probles. The text is also a practical resource for general students and professional researchers, where techniques and concepts can be readily picked up on a chapter-by-chapter basis.Parameter Estimation and Inverse Problems is structured around a course at New Mexico Tech and is designed to be accessible to typical graduate students in the physical sciences who may not have an extensive mathematical background. It is accompanied by a Web site that...
Statistical perspectives on inverse problems
DEFF Research Database (Denmark)
Andersen, Kim Emil
of the interior of an object from electrical boundary measurements. One part of this thesis concerns statistical approaches for solving, possibly non-linear, inverse problems. Thus inverse problems are recasted in a form suitable for statistical inference. In particular, a Bayesian approach for regularisation...... problem is given in terms of probability distributions. Posterior inference is obtained by Markov chain Monte Carlo methods and new, powerful simulation techniques based on e.g. coupled Markov chains and simulated tempering is developed to improve the computational efficiency of the overall simulation......Inverse problems arise in many scientific disciplines and pertain to situations where inference is to be made about a particular phenomenon from indirect measurements. A typical example, arising in diffusion tomography, is the inverse boundary value problem for non-invasive reconstruction...
Computation of inverse magnetic cascades
International Nuclear Information System (INIS)
Montgomery, D.
1981-10-01
Inverse cascades of magnetic quantities for turbulent incompressible magnetohydrodynamics are reviewed, for two and three dimensions. The theory is extended to the Strauss equations, a description intermediate between two and three dimensions appropriate to tokamak magnetofluids. Consideration of the absolute equilibrium Gibbs ensemble for the system leads to a prediction of an inverse cascade of magnetic helicity, which may manifest itself as a major disruption. An agenda for computational investigation of this conjecture is proposed
Thermal measurements and inverse techniques
Orlande, Helcio RB; Maillet, Denis; Cotta, Renato M
2011-01-01
With its uncommon presentation of instructional material regarding mathematical modeling, measurements, and solution of inverse problems, Thermal Measurements and Inverse Techniques is a one-stop reference for those dealing with various aspects of heat transfer. Progress in mathematical modeling of complex industrial and environmental systems has enabled numerical simulations of most physical phenomena. In addition, recent advances in thermal instrumentation and heat transfer modeling have improved experimental procedures and indirect measurements for heat transfer research of both natural phe
Coin tossing and Laplace inversion
Indian Academy of Sciences (India)
of a probability measure " on Е0Y 1К via the obvious change of variables e└t И xX An inversion formula for " in terms of its moments yields an inversion formula for # in terms of the values of its Laplace transform at n И 0Y 1Y 2Y ... and vice versa. In our discussion we allow " (respectively #) to have positive mass at 0 ...
An inverse problem approach to pattern recognition in industry
Directory of Open Access Journals (Sweden)
Ali Sever
2015-01-01
Full Text Available Many works have shown strong connections between learning and regularization techniques for ill-posed inverse problems. A careful analysis shows that a rigorous connection between learning and regularization for inverse problem is not straightforward. In this study, pattern recognition will be viewed as an ill-posed inverse problem and applications of methods from the theory of inverse problems to pattern recognition are studied. A new learning algorithm derived from a well-known regularization model is generated and applied to the task of reconstruction of an inhomogeneous object as pattern recognition. Particularly, it is demonstrated that pattern recognition can be reformulated in terms of inverse problems defined by a Riesz-type kernel. This reformulation can be employed to design a learning algorithm based on a numerical solution of a system of linear equations. Finally, numerical experiments have been carried out with synthetic experimental data considering a reasonable level of noise. Good recoveries have been achieved with this methodology, and the results of these simulations are compatible with the existing methods. The comparison results show that the Regularization-based learning algorithm (RBA obtains a promising performance on the majority of the test problems. In prospects, this method can be used for the creation of automated systems for diagnostics, testing, and control in various fields of scientific and applied research, as well as in industry.
EDITORIAL: Inverse Problems in Engineering
West, Robert M.; Lesnic, Daniel
2007-01-01
Presented here are 11 noteworthy papers selected from the Fifth International Conference on Inverse Problems in Engineering: Theory and Practice held in Cambridge, UK during 11-15 July 2005. The papers have been peer-reviewed to the usual high standards of this journal and the contributions of reviewers are much appreciated. The conference featured a good balance of the fundamental mathematical concepts of inverse problems with a diverse range of important and interesting applications, which are represented here by the selected papers. Aspects of finite-element modelling and the performance of inverse algorithms are investigated by Autrique et al and Leduc et al. Statistical aspects are considered by Emery et al and Watzenig et al with regard to Bayesian parameter estimation and inversion using particle filters. Electrostatic applications are demonstrated by van Berkel and Lionheart and also Nakatani et al. Contributions to the applications of electrical techniques and specifically electrical tomographies are provided by Wakatsuki and Kagawa, Kim et al and Kortschak et al. Aspects of inversion in optical tomography are investigated by Wright et al and Douiri et al. The authors are representative of the worldwide interest in inverse problems relating to engineering applications and their efforts in producing these excellent papers will be appreciated by many readers of this journal.
Chromatid Painting for Chromosomal Inversion Detection Project
National Aeronautics and Space Administration — We propose a novel approach to the detection of chromosomal inversions. Transmissible chromosome aberrations (translocations and inversions) have profound genetic...
Magnetic Resonance Imaging in Breath-Hold Divers with Cerebral Decompression Sickness
Directory of Open Access Journals (Sweden)
Ryu Matsuo
2014-01-01
Full Text Available The mechanism of cerebral decompression sickness (DCS is still unclear. We report 2 cases of breath-hold divers with cerebral DCS in whom magnetic resonance imaging (MRI demonstrated distinctive characteristics. One case presented right hemiparesthesia, diplopia, and gait disturbance after breath-hold diving into the sea at a depth of 20 m. Brain MRI with fluid-attenuated inversion recovery (FLAIR sequence revealed multiple hyperintense lesions in the right frontal lobe, bilateral thalamus, pons, and right cerebellar hemisphere. The second case presented visual and gait disturbance after repetitive breath-hold diving into the sea. FLAIR imaging showed hyperintense areas in the bilateral occipito-parietal lobes. In both cases, diffusion-weighted imaging and apparent diffusion coefficient mapping revealed hyperintense areas in the lesions identified by FLAIR. Moreover, follow-up MRI showed attenuation of the FLAIR signal abnormalities. These findings are suggestive of transient hyperpermeability in the microvasculature as a possible cause of cerebral DCS.
Inverse comptonization vs. thermal synchrotron
International Nuclear Information System (INIS)
Fenimore, E.E.; Klebesadel, R.W.; Laros, J.G.
1983-01-01
There are currently two radiation mechanisms being considered for gamma-ray bursts: thermal synchrotron and inverse comptonization. They are mutually exclusive since thermal synchrotron requires a magnetic field of approx. 10 12 Gauss whereas inverse comptonization cannot produce a monotonic spectrum if the field is larger than 10 11 and is too inefficient relative to thermal synchrotron unless the field is less than 10 9 Gauss. Neither mechanism can explain completely the observed characteristics of gamma-ray bursts. However, we conclude that thermal synchrotron is more consistent with the observations if the sources are approx. 40 kpc away whereas inverse comptonization is more consistent if they are approx. 300 pc away. Unfortunately, the source distance is still not known and, thus, the radiation mechanism is still uncertain
Inverse comorbidity in multiple sclerosis
DEFF Research Database (Denmark)
Thormann, Anja; Koch-Henriksen, Nils; Laursen, Bjarne
2016-01-01
discovery rate and investigated each of eight pre-specified comorbidity categories: psychiatric, cerebrovascular, cardiovascular, lung, and autoimmune comorbidities, diabetes, cancer, and Parkinson's disease. Results A total of 8947 MS-cases and 44,735 controls were eligible for inclusion. We found...... This study showed a decreased risk of cancers and pulmonary diseases after onset of MS. Identification of inverse comorbidity and of its underlying mechanisms may provide important new entry points into the understanding of MS.......Background Inverse comorbidity is disease occurring at lower rates than expected among persons with a given index disease. The objective was to identify inverse comorbidity in MS. Methods We performed a combined case-control and cohort study in a total nationwide cohort of cases with clinical onset...
Inverse photoemission of uranium oxides
International Nuclear Information System (INIS)
Roussel, P.; Morrall, P.; Tull, S.J.
2009-01-01
Understanding the itinerant-localised bonding role of the 5f electrons in the light actinides will afford an insight into their unusual physical and chemical properties. In recent years, the combination of core and valance band electron spectroscopies with theoretic modelling have already made significant progress in this area. However, information of the unoccupied density of states is still scarce. When compared to the forward photoemission techniques, measurements of the unoccupied states suffer from significantly less sensitivity and lower resolution. In this paper, we report on our experimental apparatus, which is designed to measure the inverse photoemission spectra of the light actinides. Inverse photoemission spectra of UO 2 and UO 2.2 along with the corresponding core and valance electron spectra are presented in this paper. UO 2 has been reported previously, although through its inclusion here it allows us to compare and contrast results from our experimental apparatus to the previous Bremsstrahlung Isochromat Spectroscopy and Inverse Photoemission Spectroscopy investigations
Inverse source problems in elastodynamics
Bao, Gang; Hu, Guanghui; Kian, Yavar; Yin, Tao
2018-04-01
We are concerned with time-dependent inverse source problems in elastodynamics. The source term is supposed to be the product of a spatial function and a temporal function with compact support. We present frequency-domain and time-domain approaches to show uniqueness in determining the spatial function from wave fields on a large sphere over a finite time interval. The stability estimate of the temporal function from the data of one receiver and the uniqueness result using partial boundary data are proved. Our arguments rely heavily on the use of the Fourier transform, which motivates inversion schemes that can be easily implemented. A Landweber iterative algorithm for recovering the spatial function and a non-iterative inversion scheme based on the uniqueness proof for recovering the temporal function are proposed. Numerical examples are demonstrated in both two and three dimensions.
Optimization for nonlinear inverse problem
International Nuclear Information System (INIS)
Boyadzhiev, G.; Brandmayr, E.; Pinat, T.; Panza, G.F.
2007-06-01
The nonlinear inversion of geophysical data in general does not yield a unique solution, but a single model, representing the investigated field, is preferred for an easy geological interpretation of the observations. The analyzed region is constituted by a number of sub-regions where the multi-valued nonlinear inversion is applied, which leads to a multi-valued solution. Therefore, combining the values of the solution in each sub-region, many acceptable models are obtained for the entire region and this complicates the geological interpretation of geophysical investigations. In this paper are presented new methodologies, capable to select one model, among all acceptable ones, that satisfies different criteria of smoothness in the explored space of solutions. In this work we focus on the non-linear inversion of surface waves dispersion curves, which gives structural models of shear-wave velocity versus depth, but the basic concepts have a general validity. (author)
SVD analysis in application to full waveform inversion of multicomponent seismic data
International Nuclear Information System (INIS)
Silvestrov, Ilya; Tcheverda, Vladimir
2011-01-01
An inverse problem of recovery the Earth's interior by multi-shot/multi-offset multicomponent seismic data is considered in this work. This problem may be considered as a nonlinear operational equation, and local derivative-based techniques are commonly used for its solution. Such method is known in seismic precessing as 'full-waveform inversion'. The major properties of the inversion process are governed by a Frechet derivative of the forward map. We show and study these properties by means of singular value decomposition (SVD) truncation. This decomposition depends strongly on the acquisition system and on the parameterization of the problem. We show, that it is very important to study the inverse problem in each particular case, otherwise unreliable results may be obtained. Surface and cross-well acquisition systems are considered in this work. Appropriate parameterizations for them are determined, and typical behavior of the inverse problem solution is studied.
Inverse methods in hydrologic optics
Directory of Open Access Journals (Sweden)
Howard R. Gordon
2002-03-01
Full Text Available Methods for solving the hydrologic-optics inverse problem, i.e., estimating the inherent optical properties of a water body based solely on measurements of the apparent optical properties, are reviewed in detail. A new method is developed for the inverse problem in water bodies in which fluorescence is important. It is shown that in principle, given profiles of the spectra of up- and downwelling irradiance, estimation of the coefficient of inelastic scattering from any wave band to any other wave band can be effected.
Inverse Interval Matrix: A Survey
Czech Academy of Sciences Publication Activity Database
Rohn, Jiří; Farhadsefat, R.
2011-01-01
Roč. 22, - (2011), s. 704-719 E-ISSN 1081-3810 R&D Projects: GA ČR GA201/09/1957; GA ČR GC201/08/J020 Institutional research plan: CEZ:AV0Z10300504 Keywords : interval matrix * inverse interval matrix * NP-hardness * enclosure * unit midpoint * inverse sign stability * nonnegative invertibility * absolute value equation * algorithm Subject RIV: BA - General Mathematics Impact factor: 0.808, year: 2010 http://www.math.technion.ac.il/iic/ela/ela-articles/articles/vol22_pp704-719.pdf
Size Estimates in Inverse Problems
Di Cristo, Michele
2014-01-06
Detection of inclusions or obstacles inside a body by boundary measurements is an inverse problems very useful in practical applications. When only finite numbers of measurements are available, we try to detect some information on the embedded object such as its size. In this talk we review some recent results on several inverse problems. The idea is to provide constructive upper and lower estimates of the area/volume of the unknown defect in terms of a quantity related to the work that can be expressed with the available boundary data.
-Dimensional Fractional Lagrange's Inversion Theorem
Directory of Open Access Journals (Sweden)
F. A. Abd El-Salam
2013-01-01
Full Text Available Using Riemann-Liouville fractional differential operator, a fractional extension of the Lagrange inversion theorem and related formulas are developed. The required basic definitions, lemmas, and theorems in the fractional calculus are presented. A fractional form of Lagrange's expansion for one implicitly defined independent variable is obtained. Then, a fractional version of Lagrange's expansion in more than one unknown function is generalized. For extending the treatment in higher dimensions, some relevant vectors and tensors definitions and notations are presented. A fractional Taylor expansion of a function of -dimensional polyadics is derived. A fractional -dimensional Lagrange inversion theorem is proved.
DEFF Research Database (Denmark)
Jensen, Morten B; Guldberg, Trine L; Harbøll, Anja
2017-01-01
BACKGROUND: The clinical target volume (CTV) in radiotherapy is routinely based on gadolinium contrast enhanced T1 weighted (T1w + Gd) and T2 weighted fluid attenuated inversion recovery (T2w FLAIR) magnetic resonance imaging (MRI) sequences which have been shown to over- or underestimate...
The reliability of magnetic resonance imaging in traumatic brain injury lesion detection
Geurts, B.H.J.; Andriessen, T.M.J.C.; Goraj, B.M.; Vos, P.E.
2012-01-01
Objective: This study compares inter-rater-reliability, lesion detection and clinical relevance of T2-weighted imaging (T2WI), Fluid Attenuated Inversion Recovery (FLAIR), T2*-gradient recalled echo (T2*-GRE) and Susceptibility Weighted Imaging (SWI) in Traumatic Brain Injury (TBI). Methods: Three
Bilinear Inverse Problems: Theory, Algorithms, and Applications
Ling, Shuyang
We will discuss how several important real-world signal processing problems, such as self-calibration and blind deconvolution, can be modeled as bilinear inverse problems and solved by convex and nonconvex optimization approaches. In Chapter 2, we bring together three seemingly unrelated concepts, self-calibration, compressive sensing and biconvex optimization. We show how several self-calibration problems can be treated efficiently within the framework of biconvex compressive sensing via a new method called SparseLift. More specifically, we consider a linear system of equations y = DAx, where the diagonal matrix D (which models the calibration error) is unknown and x is an unknown sparse signal. By "lifting" this biconvex inverse problem and exploiting sparsity in this model, we derive explicit theoretical guarantees under which both x and D can be recovered exactly, robustly, and numerically efficiently. In Chapter 3, we study the question of the joint blind deconvolution and blind demixing, i.e., extracting a sequence of functions [special characters omitted] from observing only the sum of their convolutions [special characters omitted]. In particular, for the special case s = 1, it becomes the well-known blind deconvolution problem. We present a non-convex algorithm which guarantees exact recovery under conditions that are competitive with convex optimization methods, with the additional advantage of being computationally much more efficient. We discuss several applications of the proposed framework in image processing and wireless communications in connection with the Internet-of-Things. In Chapter 4, we consider three different self-calibration models of practical relevance. We show how their corresponding bilinear inverse problems can be solved by both the simple linear least squares approach and the SVD-based approach. As a consequence, the proposed algorithms are numerically extremely efficient, thus allowing for real-time deployment. Explicit theoretical
Superconductivity in Pb inverse opal
International Nuclear Information System (INIS)
Aliev, Ali E.; Lee, Sergey B.; Zakhidov, Anvar A.; Baughman, Ray H.
2007-01-01
Type-II superconducting behavior was observed in highly periodic three-dimensional lead inverse opal prepared by infiltration of melted Pb in blue (D = 160 nm), green (D = 220 nm) and red (D = 300 nm) opals and followed by the extraction of the SiO 2 spheres by chemical etching. The onset of a broad phase transition (ΔT = 0.3 K) was shifted from T c = 7.196 K for bulk Pb to T c = 7.325 K. The upper critical field H c2 (3150 Oe) measured from high-field hysteresis loops exceeds the critical field for bulk lead (803 Oe) fourfold. Two well resolved peaks observed in the hysteresis loops were ascribed to flux penetration into the cylindrical void space that can be found in inverse opal structure and into the periodic structure of Pb nanoparticles. The red inverse opal shows pronounced oscillations of magnetic moment in the mixed state at low temperatures, T 0.9T c has been observed for all of the samples studied. The magnetic field periodicity of resistivity modulation is in good agreement with the lattice parameter of the inverse opal structure. We attribute the failure to observe pronounced modulation in magneto-resistive measurement to difficulties in the precision orientation of the sample along the magnetic field
Statistical and Computational Inverse Problems
Kaipio, Jari
2005-01-01
Develops the statistical approach to inverse problems with an emphasis on modeling and computations. The book discusses the measurement noise modeling and Bayesian estimation, and uses Markov Chain Monte Carlo methods to explore the probability distributions. It is for researchers and advanced students in applied mathematics.
Coin Tossing and Laplace Inversion
Indian Academy of Sciences (India)
An analysis of exchangeable sequences of coin tossings leads to inversion formulae for Laplace transforms of probability measures. Author Affiliations. J C Gupta1 2. Indian Statistical Institute, New Delhi 110 016, India; 32, Mirdha Tola, Budaun 243 601, India. Dates. Manuscript received: 5 May 1999; Manuscript revised: 3 ...
Givental Graphs and Inversion Symmetry
Dunin-Barkovskiy, P.; Shadrin, S.; Spitz, L.
2013-01-01
Inversion symmetry is a very non-trivial discrete symmetry of Frobenius manifolds. It was obtained by Dubrovin from one of the elementary Schlesinger transformations of a special ODE associated to a Frobenius manifold. In this paper, we review the Givental group action on Frobenius manifolds in
Wave-equation dispersion inversion
Li, Jing
2016-12-08
We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.
Adjoint modeling for acoustic inversion
Hursky, Paul; Porter, Michael B.; Cornuelle, B. D.; Hodgkiss, W. S.; Kuperman, W. A.
2004-02-01
The use of adjoint modeling for acoustic inversion is investigated. An adjoint model is derived from a linearized forward propagation model to propagate data-model misfit at the observation points back through the medium to the medium perturbations not being accounted for in the model. This adjoint model can be used to aid in inverting for these unaccounted medium perturbations. Adjoint methods are being applied to a variety of inversion problems, but have not drawn much attention from the underwater acoustic community. This paper presents an application of adjoint methods to acoustic inversion. Inversions are demonstrated in simulation for both range-independent and range-dependent sound speed profiles using the adjoint of a parabolic equation model. Sensitivity and error analyses are discussed showing how the adjoint model enables calculations to be performed in the space of observations, rather than the often much larger space of model parameters. Using an adjoint model enables directions of steepest descent in the model parameters (what we invert for) to be calculated using far fewer modeling runs than if a forward model only were used.
Workflows for Full Waveform Inversions
Boehm, Christian; Krischer, Lion; Afanasiev, Michael; van Driel, Martin; May, Dave A.; Rietmann, Max; Fichtner, Andreas
2017-04-01
Despite many theoretical advances and the increasing availability of high-performance computing clusters, full seismic waveform inversions still face considerable challenges regarding data and workflow management. While the community has access to solvers which can harness modern heterogeneous computing architectures, the computational bottleneck has fallen to these often manpower-bounded issues that need to be overcome to facilitate further progress. Modern inversions involve huge amounts of data and require a tight integration between numerical PDE solvers, data acquisition and processing systems, nonlinear optimization libraries, and job orchestration frameworks. To this end we created a set of libraries and applications revolving around Salvus (http://salvus.io), a novel software package designed to solve large-scale full waveform inverse problems. This presentation focuses on solving passive source seismic full waveform inversions from local to global scales with Salvus. We discuss (i) design choices for the aforementioned components required for full waveform modeling and inversion, (ii) their implementation in the Salvus framework, and (iii) how it is all tied together by a usable workflow system. We combine state-of-the-art algorithms ranging from high-order finite-element solutions of the wave equation to quasi-Newton optimization algorithms using trust-region methods that can handle inexact derivatives. All is steered by an automated interactive graph-based workflow framework capable of orchestrating all necessary pieces. This naturally facilitates the creation of new Earth models and hopefully sparks new scientific insights. Additionally, and even more importantly, it enhances reproducibility and reliability of the final results.
Application of the kernel method to the inverse geosounding problem.
Hidalgo, Hugo; Sosa León, Sonia; Gómez-Treviño, Enrique
2003-01-01
Determining the layered structure of the earth demands the solution of a variety of inverse problems; in the case of electromagnetic soundings at low induction numbers, the problem is linear, for the measurements may be represented as a linear functional of the electrical conductivity distribution. In this paper, an application of the support vector (SV) regression technique to the inversion of electromagnetic data is presented. We take advantage of the regularizing properties of the SV learning algorithm and use it as a modeling technique with synthetic and field data. The SV method presents better recovery of synthetic models than Tikhonov's regularization. As the SV formulation is solved in the space of the data, which has a small dimension in this application, a smaller problem than that considered with Tikhonov's regularization is produced. For field data, the SV formulation develops models similar to those obtained via linear programming techniques, but with the added characteristic of robustness.
Seven-Tesla Magnetization Transfer Imaging to Detect Multiple Sclerosis White Matter Lesions.
Chou, I-Jun; Lim, Su-Yin; Tanasescu, Radu; Al-Radaideh, Ali; Mougin, Olivier E; Tench, Christopher R; Whitehouse, William P; Gowland, Penny A; Constantinescu, Cris S
2018-03-01
Fluid-attenuated inversion recovery (FLAIR) imaging at 3 Tesla (T) field strength is the most sensitive modality for detecting white matter lesions in multiple sclerosis. While 7T FLAIR is effective in detecting cortical lesions, it has not been fully optimized for visualization of white matter lesions and thus has not been used for delineating lesions in quantitative magnetic resonance imaging (MRI) studies of the normal appearing white matter in multiple sclerosis. Therefore, we aimed to evaluate the sensitivity of 7T magnetization-transfer-weighted (MT w ) images in the detection of white matter lesions compared with 3T-FLAIR. Fifteen patients with clinically isolated syndrome, 6 with multiple sclerosis, and 10 healthy participants were scanned with 7T 3-dimensional (D) MT w and 3T-2D-FLAIR sequences on the same day. White matter lesions visible on either sequence were delineated. Of 662 lesions identified on 3T-2D-FLAIR images, 652 were detected on 7T-3D-MT w images (sensitivity, 98%; 95% confidence interval, 97% to 99%). The Spearman correlation coefficient between lesion loads estimated by the two sequences was .910. The intrarater and interrater reliability for 7T-3D-MT w images was good with an intraclass correlation coefficient (ICC) of 98.4% and 81.8%, which is similar to that for 3T-2D-FLAIR images (ICC 96.1% and 96.7%). Seven-Tesla MT w sequences detected most of the white matter lesions identified by FLAIR at 3T. This suggests that 7T-MT w imaging is a robust alternative for detecting demyelinating lesions in addition to 3T-FLAIR. Future studies need to compare the roles of optimized 7T-FLAIR and of 7T-MT w imaging. © 2017 The Authors. Journal of Neuroimaging published by Wiley Periodicals, Inc. on behalf of American Society of Neuroimaging.
Three-dimensional inverse scattering: High-frequency analysis of Newton's Marchenko equation
International Nuclear Information System (INIS)
Cheney, M.; Rose, J.H.
1985-01-01
We obtain a high-frequency asymptotic expansion of Newton's Marchenko equation for three-dimensional inverse scattering. We find that the inhomogeneous term contains the same high-frequency information as does the Born approximation. We show that recovery of the potential via Newton's Marchenko equation plus the ''miracle'' depends on low-frequency information
Hedland, D. A.; Degonia, P. K.
1974-01-01
The RAE-1 spacecraft inversion performed October 31, 1972 is described based upon the in-orbit dynamical data in conjunction with results obtained from previously developed computer simulation models. The computer simulations used are predictive of the satellite dynamics, including boom flexing, and are applicable during boom deployment and retraction, inter-phase coast periods, and post-deployment operations. Attitude data, as well as boom tip data, were analyzed in order to obtain a detailed description of the dynamical behavior of the spacecraft during and after the inversion. Runs were made using the computer model and the results were analyzed and compared with the real time data. Close agreement between the actual recorded spacecraft attitude and the computer simulation results was obtained.
Validation of OSIRIS Ozone Inversions
Gudnason, P.; Evans, W. F.; von Savigny, C.; Sioris, C.; Halley, C.; Degenstein, D.; Llewellyn, E. J.; Petelina, S.; Gattinger, R. L.; Odin Team
2002-12-01
The OSIRIS instrument onboard the Odin satellite, that was launched on February 20, 2001, is a combined optical spectrograph and infrared imager that obtains profil sets of atmospheric spectra from 280 to 800 nm when Odin scans the terrestrial limb. It has been possible to make a preliminary analysis of the ozone profiles using the Chappuis absorption feature. Three algorithms have been developed for ozone profile inversions from these limb spectra sets. We have dubbed these the Gattinger, Von Savigny-Flittner and DOAS methods. These are being evaluated against POAM and other satellite data. Based on performance, one of these will be selected for the operational algorithm. The infrared imager data have been used by Degenstein with the tomographic inversion procedure to derive ozone concentrations above 60 km. This paper will present some of these initial observations and indicate the best algorithm potential of OSIRIS to make spectacular advances in the study of terrestrial ozone.
National Aeronautics and Space Administration — The AES Water Recovery Project (WRP) is advancing environmental control and life support systems water recovery technologies to support human exploration beyond low...
U.S. Environmental Protection Agency — The EPA Recovery Mapper is an Internet interactive mapping application that allows users to discover information about every American Recovery and Reinvestment Act...
Inverse problem in transformation optics
Novitsky, Andrey V.
2011-01-01
The straightforward method of transformation optics implies that one starts from the coordinate transformation and determines the Jacobian matrix, the fields and material parameters of the cloak. However, the coordinate transformation appears as an optional function: it is not necessary to know it. We offer the solution of some sort of inverse problem: starting from the fields in the invisibility cloak we directly derive the permittivity and permeability tensors of the cloaking shell. This ap...
Fourier reconstruction with sparse inversions
Zwartjes, P.M.
2005-01-01
In seismic exploration an image of the subsurface is generated from seismic data through various data processing algorithms. When the data is not acquired on an equidistantly spaced grid, artifacts may result in the final image. Fourier reconstruction is an interpolation technique that can reduce these artifacts by generating uniformly sampled data from such non-uniformly sampled data. The method works by estimating via least-squares inversion the Fourier coefficients that describe the non-un...
The Inverse of Banded Matrices
2013-01-01
for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite ...numbers of summed or subtracted terms in computing the inverse of a term of an upper (lower) triangular matrix are the generalized order-k Fibonacci ... Fibonacci numbers are the usual Fibonacci numbers, that is, f 2m = Fm (mth Fibonacci number). When also k = 3, c1 = c2 = c3 = 1, then the generalized order-3
Inverse-magnetron mass spectrometer
International Nuclear Information System (INIS)
Pakulin, V.N.
1979-01-01
Considered is the operation of a typical magnetron mass spectrometer with an internal ion source and that of an inverse magnetron mass spectrometer with an external ion source. It is found that for discrimination of the same mass using the inverse design of mass spectrometers it is possible to employ either r 2 /r 1 times lesser magnetic fields at equal accelerating source-collector voltages, or r 2 /r 1 higher accelerating voltages at equal magnetic fields, as compared to the typical design (r 1 and r 2 being radii of the internal and external electrodes of the analyser, respectively). The design of an inverse-magnetron mass spectrometer is described. The mass analyzer is formed by a cylindrical electrode of 3 mm diameter and a coaxial tubular cylinder of 55 mm diameter. External to the analyzer is an ionizing chamber at the pressure of up to 5x10 -6 torr. The magnetic field along the chamber axis produced by a solenoid was 300 Oe. At the accelerating voltage of 100 V and mass 28, the spectrometer has a resolution of 30 at a half-peak height
Spatially Dispersed Employee Recovery
DEFF Research Database (Denmark)
Hvass, Kristian Anders; Torfadóttir, Embla
2014-01-01
personnel achieve service recovery. Employee recovery within service research often focuses on front-line employees that work in a fixed location, however a contribution to the field is made by investigating the recovery of spatially dispersed personnel, such as operational personnel in the transport sector...
DEFF Research Database (Denmark)
Petersen, Kirsten Schultz; Friis, Vivi Soegaard; Haxholm, Birthe Lodahl
2015-01-01
Mental health services strive to implement a recovery-oriented approach to rehabilitation. Little is known about service users' perception of the recovery approach. The aim is to explore the service user's perspectives on facilitators and barriers associated with recovery. Twelve residents living...
Inverse problems for difference equations with quadratic ...
African Journals Online (AJOL)
Inverse problems for difference equations with quadratic Eigenparameter dependent boundary conditions. Sonja Currie, Anne D. Love. Abstract. This paper inductively investigates an inverse problem for difference boundary value problems with boundary conditions that depend quadratically on the eigenparameter.
Fast computation of the inverse CMH model
Patel, Umesh D.; Della Torre, Edward
2001-12-01
A fast computational method based on differential equation approach for inverse Della Torre, Oti, Kádár (DOK) model has been extended for the inverse Complete Moving Hysteresis (CMH) model. A cobweb technique for calculating the inverse CMH model is also presented. The two techniques differ from the point of view of flexibility, accuracy, and computation time. Simulation results of the inverse computation for both methods are presented.
LA INVERSION INMOBILIARIA INDIRECTA EN ESPANA.
Joan MONTLLOR-SERRATS; Anna M. PANOSA-GUBAU
2013-01-01
En este articulo se revisan los instrumentos de inversion indirecta inmobiliaria en Espana, desde la creacion en 1992 de los Fondos y Sociedades de Inversion inmobiliaria (FII y SII) hasta la creacion de la primera Sociedad de inversion del mercado inmobiliario (SOCIMI) en 2013. Se analizan las caracteristicas de los mismos y asimismo los motivos por los cuales estas figuras de inversion no han tenido mucha demanda hasta el momento, en comparacion con los REITs (Real Estate Investment Trusts)...
Codimension zero laminations are inverse limits
Lozano Rojo, Álvaro
2013-01-01
The aim of the paper is to investigate the relation between inverse limit of branched manifolds and codimension zero laminations. We give necessary and sufficient conditions for such an inverse limit to be a lamination. We also show that codimension zero laminations are inverse limits of branched manifolds. The inverse limit structure allows us to show that equicontinuous codimension zero laminations preserves a distance function on transversals.
Inversion: A Most Useful Kind of Transformation.
Dubrovsky, Vladimir
1992-01-01
The transformation assigning to every point its inverse with respect to a circle with given radius and center is called an inversion. Discusses inversion with respect to points, circles, angles, distances, space, and the parallel postulate. Exercises related to these topics are included. (MDH)
Battleground Energy Recovery Project
Energy Technology Data Exchange (ETDEWEB)
Bullock, Daniel [USDOE Gulf Coast Clean Energy Application Center, Woodlands, TX (United States)
2011-12-31
In October 2009, the project partners began a 36-month effort to develop an innovative, commercial-scale demonstration project incorporating state-of-the-art waste heat recovery technology at Clean Harbors, Inc., a large hazardous waste incinerator site located in Deer Park, Texas. With financial support provided by the U.S. Department of Energy, the Battleground Energy Recovery Project was launched to advance waste heat recovery solutions into the hazardous waste incineration market, an area that has seen little adoption of heat recovery in the United States. The goal of the project was to accelerate the use of energy-efficient, waste heat recovery technology as an alternative means to produce steam for industrial processes. The project had three main engineering and business objectives: Prove Feasibility of Waste Heat Recovery Technology at a Hazardous Waste Incinerator Complex; Provide Low-cost Steam to a Major Polypropylene Plant Using Waste Heat; and Create a Showcase Waste Heat Recovery Demonstration Project.
Inversion of GPS meteorology data
Directory of Open Access Journals (Sweden)
K. Hocke
Full Text Available The GPS meteorology (GPS/MET experiment, led by the Universities Corporation for Atmospheric Research (UCAR, consists of a GPS receiver aboard a low earth orbit (LEO satellite which was launched on 3 April 1995. During a radio occultation the LEO satellite rises or sets relative to one of the 24 GPS satellites at the Earth's horizon. Thereby the atmospheric layers are successively sounded by radio waves which propagate from the GPS satellite to the LEO satellite. From the observed phase path increases, which are due to refraction of the radio waves by the ionosphere and the neutral atmosphere, the atmospheric parameter refractivity, density, pressure and temperature are calculated with high accuracy and resolution (0.5–1.5 km. In the present study, practical aspects of the GPS/MET data analysis are discussed. The retrieval is based on the Abelian integral inversion of the atmospheric bending angle profile into the refractivity index profile. The problem of the upper boundary condition of the Abelian integral is described by examples. The statistical optimization approach which is applied to the data above 40 km and the use of topside bending angle profiles from model atmospheres stabilize the inversion. The retrieved temperature profiles are compared with corresponding profiles which have already been calculated by scientists of UCAR and Jet Propulsion Laboratory (JPL, using Abelian integral inversion too. The comparison shows that in some cases large differences occur (5 K and more. This is probably due to different treatment of the upper boundary condition, data runaways and noise. Several temperature profiles with wavelike structures at tropospheric and stratospheric heights are shown. While the periodic structures at upper stratospheric heights could be caused by residual errors of the ionospheric correction method, the periodic temperature fluctuations at heights below 30 km are most likely caused by atmospheric waves (vertically
Inverse problem in transformation optics
DEFF Research Database (Denmark)
Novitsky, Andrey
2011-01-01
. We offer the solution of some sort of inverse problem: starting from the fields in the invisibility cloak we directly derive the permittivity and permeability tensors of the cloaking shell. This approach can be useful for finding material parameters for the specified electromagnetic fields......The straightforward method of transformation optics implies that one starts from the coordinate transformation and determines the Jacobian matrix, the fields and material parameters of the cloak. However, the coordinate transformation appears as an optional function: it is not necessary to know it...... in the cloaking shell without knowing the coordinate transformation....
Iterative optimization in inverse problems
Byrne, Charles L
2014-01-01
Iterative Optimization in Inverse Problems brings together a number of important iterative algorithms for medical imaging, optimization, and statistical estimation. It incorporates recent work that has not appeared in other books and draws on the author's considerable research in the field, including his recently developed class of SUMMA algorithms. Related to sequential unconstrained minimization methods, the SUMMA class includes a wide range of iterative algorithms well known to researchers in various areas, such as statistics and image processing. Organizing the topics from general to more
Planetary radar data inversion techniques improvement
Picardi, G.; Masdea, A.; Mastrogiuseppe, M.; Restano, M.; Seu, R.
2012-04-01
The planetary radar (e.g. MARSIS) data inversion is based on the selection of groups of stationary frames, within the area under investigation, that shall be statistically analyzed after suitable correction. The selection step includes the recovery of bad/poor data and the estimation of the geometrical surface and subsurface features; these feature shall be utilized in order to obtain data that are only dependent by the material nature of the inclusion, within the layer, and of the interface. This paper is addressed to the techniques used for the frames selection, recovery and their geometric estimation content. As first step, frames have been selected in Mars areas where the surface and subsurface have a physical optics behavior (i.e. quite flat); the surface flatness has been estimated according to a simulator based on MOLA (Mars Orbiter Laser Altimeter) data while the subsurface has been estimated taking into account the Doppler filters content (i.e. filter 0, +1, -1). Being the surface and subsurface quite flat only small geometric contribution have been estimated and used for correction of the received echoes. To perform this task surface and subsurface models have been developed, under the Kirchhoff approximation hypothesis, to be compared with the experimental data. A figure showing the different material nature of different areas of the Mars South Pole has been drawn. The discovery of areas with an high dielectric constant led geologists to analyze those areas with other instrument to confirm the results obtained by MARSIS. This paper outlines also the way out for future works in order to analyze more complex surface and subsurface scenarios where conditions for geometric optics or fractal can be present. In this case, it will be mandatory to develop a clutter cancellation technique to avoid the presence of false subsurface echoes generated by surface and subsurface features not immediately below the nadir direction of observation. It will be also necessary
Inverse design of multicomponent assemblies
Piñeros, William D.; Lindquist, Beth A.; Jadrich, Ryan B.; Truskett, Thomas M.
2018-03-01
Inverse design can be a useful strategy for discovering interactions that drive particles to spontaneously self-assemble into a desired structure. Here, we extend an inverse design methodology—relative entropy optimization—to determine isotropic interactions that promote assembly of targeted multicomponent phases, and we apply this extension to design interactions for a variety of binary crystals ranging from compact triangular and square architectures to highly open structures with dodecagonal and octadecagonal motifs. We compare the resulting optimized (self- and cross) interactions for the binary assemblies to those obtained from optimization of analogous single-component systems. This comparison reveals that self-interactions act as a "primer" to position particles at approximately correct coordination shell distances, while cross interactions act as the "binder" that refines and locks the system into the desired configuration. For simpler binary targets, it is possible to successfully design self-assembling systems while restricting one of these interaction types to be a hard-core-like potential. However, optimization of both self- and cross interaction types appears necessary to design for assembly of more complex or open structures.
LHC Report: 2 inverse femtobarns!
Mike Lamont for the LHC Team
2011-01-01
The LHC is enjoying a confluence of twos. This morning (Friday 5 August) we passed 2 inverse femtobarns delivered in 2011; the peak luminosity is now just over 2 x1033 cm-2s-1; and recently fill 2000 was in for nearly 22 hours and delivered around 90 inverse picobarns, almost twice 2010's total. In order to increase the luminosity we can increase of number of bunches, increase the number of particles per bunch, or decrease the transverse beam size at the interaction point. The beam size can be tackled in two ways: either reduce the size of the injected bunches or squeeze harder with the quadrupole magnets situated on either side of the experiments. Having increased the number of bunches to 1380, the maximum possible with a 50 ns bunch spacing, a one day meeting in Crozet decided to explore the other possibilities. The size of the beams coming from the injectors has been reduced to the minimum possible. This has brought an increase in the peak luminosity of about 50% and the 2 x 1033 cm...
Inverse problems in systems biology
International Nuclear Information System (INIS)
Engl, Heinz W; Lu, James; Müller, Stefan; Flamm, Christoph; Schuster, Peter; Kügler, Philipp
2009-01-01
Systems biology is a new discipline built upon the premise that an understanding of how cells and organisms carry out their functions cannot be gained by looking at cellular components in isolation. Instead, consideration of the interplay between the parts of systems is indispensable for analyzing, modeling, and predicting systems' behavior. Studying biological processes under this premise, systems biology combines experimental techniques and computational methods in order to construct predictive models. Both in building and utilizing models of biological systems, inverse problems arise at several occasions, for example, (i) when experimental time series and steady state data are used to construct biochemical reaction networks, (ii) when model parameters are identified that capture underlying mechanisms or (iii) when desired qualitative behavior such as bistability or limit cycle oscillations is engineered by proper choices of parameter combinations. In this paper we review principles of the modeling process in systems biology and illustrate the ill-posedness and regularization of parameter identification problems in that context. Furthermore, we discuss the methodology of qualitative inverse problems and demonstrate how sparsity enforcing regularization allows the determination of key reaction mechanisms underlying the qualitative behavior. (topical review)
Inverse problems and inverse scattering of plane waves
Ghosh Roy, Dilip N
2001-01-01
The purpose of this text is to present the theory and mathematics of inverse scattering, in a simple way, to the many researchers and professionals who use it in their everyday research. While applications range across a broad spectrum of disciplines, examples in this text will focus primarly, but not exclusively, on acoustics. The text will be especially valuable for those applied workers who would like to delve more deeply into the fundamentally mathematical character of the subject matter.Practitioners in this field comprise applied physicists, engineers, and technologists, whereas the theory is almost entirely in the domain of abstract mathematics. This gulf between the two, if bridged, can only lead to improvement in the level of scholarship in this highly important discipline. This is the book''s primary focus.
Comparison of MR sequences in early cerebral infarction at 0.5 T
Energy Technology Data Exchange (ETDEWEB)
Saatci, I.; Baskan, O.; Cekirge, H.S.; Besim, A. [Hacettepe Univ. Hospital, Ankara (Turkey). Radiology Dept.
2000-11-01
To compare the diagnostic values of fluid-attenuated inversion recovery (FLAIR) and gradient spin-echo (GRASE) with those of conventional spin-echo (SE) and fast SE T2-weighted sequences in the evaluation of acute cerebrovascular lesions at 0.5 T. Material and Methods: Twenty-two consecutive patients with the clinical diagnosis of acute cerebrovascular accident were examined by MR imaging within the first 48 h of ictus. MR examination included 5-mm axial conventional SE and turbo SE (TSE) T2-weighted, dual-echo GRASE and FLAIR sequences. The patients also had pre- and postcontrast T1-weighted axial images. Two examiners evaluated the images and scored the conspicuity of the acute lesions. Results: Regardless of location, FLAIR provided the best lesion conspicuity in the detection of acute infarcts, followed by the GRASE sequence. In the posterior fossa, TSE and SE demonstrated the lesions better than GRASE and FLAIR techniques. In the detection of hemorrhagic elements within the ischemic region, TSE demonstrated statistically significant superiority over other sequences. Conclusion: In the detection of acute ischemic lesions in locations other than the posterior fossa, FLAIR provided the best lesion conspicuity among four T2-weighted sequences, including SE, TSE, GRASE and FLAIR. However, for the posterior fossa examination, preference of SE or TSE T2-weighted sequences is suggested.
Comparison of MR sequences in early cerebral infarction at 0.5 T
International Nuclear Information System (INIS)
Saatci, I.; Baskan, O.; Cekirge, H.S.; Besim, A.
2000-01-01
To compare the diagnostic values of fluid-attenuated inversion recovery (FLAIR) and gradient spin-echo (GRASE) with those of conventional spin-echo (SE) and fast SE T2-weighted sequences in the evaluation of acute cerebrovascular lesions at 0.5 T. Material and Methods: Twenty-two consecutive patients with the clinical diagnosis of acute cerebrovascular accident were examined by MR imaging within the first 48 h of ictus. MR examination included 5-mm axial conventional SE and turbo SE (TSE) T2-weighted, dual-echo GRASE and FLAIR sequences. The patients also had pre- and postcontrast T1-weighted axial images. Two examiners evaluated the images and scored the conspicuity of the acute lesions. Results: Regardless of location, FLAIR provided the best lesion conspicuity in the detection of acute infarcts, followed by the GRASE sequence. In the posterior fossa, TSE and SE demonstrated the lesions better than GRASE and FLAIR techniques. In the detection of hemorrhagic elements within the ischemic region, TSE demonstrated statistically significant superiority over other sequences. Conclusion: In the detection of acute ischemic lesions in locations other than the posterior fossa, FLAIR provided the best lesion conspicuity among four T2-weighted sequences, including SE, TSE, GRASE and FLAIR. However, for the posterior fossa examination, preference of SE or TSE T2-weighted sequences is suggested
Econometric Information Recovery in Behavioral Networks
Directory of Open Access Journals (Sweden)
George Judge
2016-09-01
Full Text Available In this paper, we suggest an approach to recovering behavior-related, preference-choice network information from observational data. We model the process as a self-organized behavior based random exponential network-graph system. To address the unknown nature of the sampling model in recovering behavior related network information, we use the Cressie-Read (CR family of divergence measures and the corresponding information theoretic entropy basis, for estimation, inference, model evaluation, and prediction. Examples are included to clarify how entropy based information theoretic methods are directly applicable to recovering the behavioral network probabilities in this fundamentally underdetermined ill posed inverse recovery problem.
Recovery and money management.
Rowe, Michael; Serowik, Kristin L; Ablondi, Karen; Wilber, Charles; Rosen, Marc I
2013-06-01
Social recovery and external money management are important approaches in contemporary mental health care, but little research has been done on the relationship between the two or on application of recovery principles to money management for people at risk of being assigned a representative payee or conservator. Out of 49 total qualitative interviews, 25 transcripts with persons receiving Social Security insurance or Social Security disability insurance who were at risk of being assigned a money manager were analyzed to assess the presence of recognized recovery themes. The recovery principles of self-direction and responsibility were strong themes in participant comments related to money management. Money management interventions should incorporate peoples' recovery-related motivations to acquire financial management skills as a means to direct and assume responsibility for one's finances. Staff involved in money management should receive training to support client's recovery-related goals. (PsycINFO Database Record (c) 2013 APA, all rights reserved).
Statistical Inversion of Seismic Noise Inversion statistique du bruit sismique
Directory of Open Access Journals (Sweden)
Adler P. M.
2006-11-01
Full Text Available A systematic investigation of wave propagation in random media is presented. Spectral analysis, inversion of codas and attenuation of the direct wave front are studied for synthetic data obtained in isotropic or anisotropic, 2D or 3D media. A coda inversion process is developed and checked on two sets of real data. In both cases, it is possible to compare the correlation lengths obtained by inversion to characteristic lengths measured on seismic logs, for the full scale seismic survey, or on a thin section, for the laboratory experiment. These two experiments prove the feasibility and the efficiency of the statistical inversion of codas. Correct characteristic lengths can be obtained which cannot be determined by another method. Le problème de la géophysique est la recherche d'informations concernant le sous-sol, dans des signaux sismiques enregistrés en surface ou dans des puits. Ces informations sont habituellement recherchées sous forme déterministe, c'est-à-dire sous la forme de la donnée en chaque point d'une valeur du paramètre étudié. Notre point de vue est différent puisque notre objectif est de déduire certaines propriétés statistiques du milieu, supposé hétérogène, à partir des sismogrammes enregistrés après propagation. Il apparaît alors deux moyens de remplir l'objectif fixé. Le premier est l'analyse spectrale des codas ; cette analyse permet de déterminer les tailles moyennes des hétérogénéités du sous-sol. La deuxième possibilité est l'étude de l'atténuation du front direct de l'onde, qui conduit aussi à la connaissance des longueurs caractéristiques du sous-sol ; contrairement à la première méthode, elle ne semble pas pouvoir être transposée efficacement à des cas réels. Dans la première partie, on teste numériquement la proportionnalité entre le facteur de rétrodiffraction, relié aux propriétés statistiques du milieu, et le spectre des codas. Les distributions de vitesse, à valeur
Solution for Ill-Posed Inverse Kinematics of Robot Arm by Network Inversion
Directory of Open Access Journals (Sweden)
Takehiko Ogawa
2010-01-01
Full Text Available In the context of controlling a robot arm with multiple joints, the method of estimating the joint angles from the given end-effector coordinates is called inverse kinematics, which is a type of inverse problems. Network inversion has been proposed as a method for solving inverse problems by using a multilayer neural network. In this paper, network inversion is introduced as a method to solve the inverse kinematics problem of a robot arm with multiple joints, where the joint angles are estimated from the given end-effector coordinates. In general, inverse problems are affected by ill-posedness, which implies that the existence, uniqueness, and stability of their solutions are not guaranteed. In this paper, we show the effectiveness of applying network inversion with regularization, by which ill-posedness can be reduced, to the ill-posed inverse kinematics of an actual robot arm with multiple joints.
Inverse problem in neutron reflection
International Nuclear Information System (INIS)
Zhou, Xiao-Lin; Felcher, G.P.; Chen, Sow-Hsin
1991-05-01
Reflectance and transmittance of neutrons from a thin film deposited on a bulk substrate are derived from solution of Schroedinger wave equation in the material medium with an optical potential. A closed-form solution for the complex reflectance and transmittance is obtained in an approximation where the curvature of the scattering length density profile in the film is small. This closed-form solution reduces to all the known approximations in various limiting cases and is shown to be more accurate than the existing approximations. The closed-form solution of the reflectance is used as a starting point for an inversion algorithm whereby the reflectance data are inverted by a matrix iteration scheme to obtain the scattering length density distribution in the film. A preliminary test showed that the inverted profile is accurate for the linear scattering length density distribution but falls short in the case of an exponential distribution. 30 refs., 7 figs., 1 tab
Wake Vortex Inverse Model User's Guide
Lai, David; Delisi, Donald
2008-01-01
NorthWest Research Associates (NWRA) has developed an inverse model for inverting landing aircraft vortex data. The data used for the inversion are the time evolution of the lateral transport position and vertical position of both the port and starboard vortices. The inverse model performs iterative forward model runs using various estimates of vortex parameters, vertical crosswind profiles, and vortex circulation as a function of wake age. Forward model predictions of lateral transport and altitude are then compared with the observed data. Differences between the data and model predictions guide the choice of vortex parameter values, crosswind profile and circulation evolution in the next iteration. Iterations are performed until a user-defined criterion is satisfied. Currently, the inverse model is set to stop when the improvement in the rms deviation between the data and model predictions is less than 1 percent for two consecutive iterations. The forward model used in this inverse model is a modified version of the Shear-APA model. A detailed description of this forward model, the inverse model, and its validation are presented in a different report (Lai, Mellman, Robins, and Delisi, 2007). This document is a User's Guide for the Wake Vortex Inverse Model. Section 2 presents an overview of the inverse model program. Execution of the inverse model is described in Section 3. When executing the inverse model, a user is requested to provide the name of an input file which contains the inverse model parameters, the various datasets, and directories needed for the inversion. A detailed description of the list of parameters in the inversion input file is presented in Section 4. A user has an option to save the inversion results of each lidar track in a mat-file (a condensed data file in Matlab format). These saved mat-files can be used for post-inversion analysis. A description of the contents of the saved files is given in Section 5. An example of an inversion input
Accommodating chromosome inversions in linkage analysis.
Chen, Gary K; Slaten, Erin; Ophoff, Roel A; Lange, Kenneth
2006-08-01
This work develops a population-genetics model for polymorphic chromosome inversions. The model precisely describes how an inversion changes the nature of and approach to linkage equilibrium. The work also describes algorithms and software for allele-frequency estimation and linkage analysis in the presence of an inversion. The linkage algorithms implemented in the software package Mendel estimate recombination parameters and calculate the posterior probability that each pedigree member carries the inversion. Application of Mendel to eight Centre d'Etude du Polymorphisme Humain pedigrees in a region containing a common inversion on 8p23 illustrates its potential for providing more-precise estimates of the location of an unmapped marker or trait gene. Our expanded cytogenetic analysis of these families further identifies inversion carriers and increases the evidence of linkage.
Optimization and inverse problems in electromagnetism
Wiak, Sławomir
2003-01-01
From 12 to 14 September 2002, the Academy of Humanities and Economics (AHE) hosted the workshop "Optimization and Inverse Problems in Electromagnetism". After this bi-annual event, a large number of papers were assembled and combined in this book. During the workshop recent developments and applications in optimization and inverse methodologies for electromagnetic fields were discussed. The contributions selected for the present volume cover a wide spectrum of inverse and optimal electromagnetic methodologies, ranging from theoretical to practical applications. A number of new optimal and inverse methodologies were proposed. There are contributions related to dedicated software. Optimization and Inverse Problems in Electromagnetism consists of three thematic chapters, covering: -General papers (survey of specific aspects of optimization and inverse problems in electromagnetism), -Methodologies, -Industrial Applications. The book can be useful to students of electrical and electronics engineering, computer sci...
Identifiability Scaling Laws in Bilinear Inverse Problems
Choudhary, Sunav; Mitra, Urbashi
2014-01-01
A number of ill-posed inverse problems in signal processing, like blind deconvolution, matrix factorization, dictionary learning and blind source separation share the common characteristic of being bilinear inverse problems (BIPs), i.e. the observation model is a function of two variables and conditioned on one variable being known, the observation is a linear function of the other variable. A key issue that arises for such inverse problems is that of identifiability, i.e. whether the observa...
Lectures on the inverse scattering method
International Nuclear Information System (INIS)
Zakharov, V.E.
1983-06-01
In a series of six lectures an elementary introduction to the theory of inverse scattering is given. The first four lectures contain a detailed theory of solitons in the framework of the KdV equation, together with the inverse scattering theory of the one-dimensional Schroedinger equation. In the fifth lecture the dressing method is described, while the sixth lecture gives a brief review of the equations soluble by the inverse scattering method. (author)
Inverse kinematics of OWI-535 robotic arm
DEBENEC, PRIMOŽ
2015-01-01
The thesis aims to calculate the inverse kinematics for the OWI-535 robotic arm. The calculation of the inverse kinematics determines the joint parameters that provide the right pose of the end effector. The pose consists of the position and orientation, however, we will focus only on the second one. Due to arm limitations, we have created our own type of the calculation of the inverse kinematics. At first we have derived it only theoretically, and then we have transferred the derivation into...
Automatic Flight Controller With Model Inversion
Meyer, George; Smith, G. Allan
1992-01-01
Automatic digital electronic control system based on inverse-model-follower concept being developed for proposed vertical-attitude-takeoff-and-landing airplane. Inverse-model-follower control places inverse mathematical model of dynamics of controlled plant in series with control actuators of controlled plant so response of combination of model and plant to command is unity. System includes feedback to compensate for uncertainties in mathematical model and disturbances imposed from without.
Rapstine, Thomas D.
Gravity gradiometry has been used as a geophysical tool to image salt structure in hydrocarbon exploration. The knowledge of the location, orientation, and spatial extent of salt bodies helps characterize possible petroleum prospects. Imaging around and underneath salt bodies can be challenging given the petrophysical properties and complicated geometry of salt. Methods for imaging beneath salt using seismic data exist but are often iterative and expensive, requiring a refinement of a velocity model at each iteration. Fortunately, the relatively strong density contrast between salt and background density structure pro- vides the opportunity for gravity gradiometry to be useful in exploration, especially when integrated with other geophysical data such as seismic. Quantitatively integrating multiple geophysical data is not trivial, but can improve the recovery of salt body geometry and petrophysical composition using inversion. This thesis provides two options for quantitatively integrating seismic, AGG, and petrophysical data that may aid the imaging of salt bodies. Both methods leverage and expand upon previously developed deterministic inversion methods. The inversion methods leverage seismically derived information, such as horizon slope and salt body interpretation, to constrain the inversion of airborne gravity gradiometry data (AGG) to arrive at a density contrast model. The first method involves constraining a top of salt inversion using slope in a seismic image. The second method expands fuzzy c-means (FCM) clustering inversion to include spatial control on clustering based on a seismically derived salt body interpretation. The effective- ness of the methods are illustrated on a 2D synthetic earth model derived from the SEAM Phase 1 salt model. Both methods show that constraining the inversion of AGG data using information derived from seismic images can improve the recovery of salt.
Time-reversal and Bayesian inversion
Debski, Wojciech
2017-04-01
Probabilistic inversion technique is superior to the classical optimization-based approach in all but one aspects. It requires quite exhaustive computations which prohibit its use in huge size inverse problems like global seismic tomography or waveform inversion to name a few. The advantages of the approach are, however, so appealing that there is an ongoing continuous afford to make the large inverse task as mentioned above manageable with the probabilistic inverse approach. One of the perspective possibility to achieve this goal relays on exploring the internal symmetry of the seismological modeling problems in hand - a time reversal and reciprocity invariance. This two basic properties of the elastic wave equation when incorporating into the probabilistic inversion schemata open a new horizons for Bayesian inversion. In this presentation we discuss the time reversal symmetry property, its mathematical aspects and propose how to combine it with the probabilistic inverse theory into a compact, fast inversion algorithm. We illustrate the proposed idea with the newly developed location algorithm TRMLOC and discuss its efficiency when applied to mining induced seismic data.
Chromatid Painting for Chromosomal Inversion Detection Project
National Aeronautics and Space Administration — We propose the continued development of a novel approach to the detection of chromosomal inversions. Transmissible chromosome aberrations (translocations and...
Research on Stochastic Resonance Signal’s Recovery
Directory of Open Access Journals (Sweden)
Hao Wang
2013-01-01
Full Text Available Using stochastic resonance to detect weak periodic signals has been widely used in various fields of science, which attracts much attention of researchers due to its advantages of revealing recessive periodic laws. This paper utilized this method to seek the underlying rule of setting weather index, so we can find that how to obtain the accurate expression of original periodic law by further investigation. This paper deals with the noise-contained signal restoring on the basis of the established system coupling the inversion system and bistable system. The simulation shows that this signal recovery method inversion effect is better and the application range is wider.
Young, Benjamin D; Mankin, Joseph M; Griffin, John F; Fosgate, Geoffrey T; Fowler, Jennifer L; Levine, Jonathan M
2015-01-01
T2-weighted (T2w) sequences are commonly relied upon in magnetic resonance imaging protocols for the detection of brain lesions in dogs. Previously, the effect of fluid suppression via fluid-attenuated inversion recovery (FLAIR) has been compared to T2-weighting with mixed results. Short tau inversion recovery (STIR) has been reported to increase the detection of some CNS lesions in people. The purpose of the current study was to evaluate the effect of fat suppression on brain parenchymal contrast resolution and lesion detection in dogs. We compared three sequences: T2w images, STIR, and T2w FLAIR with chemical fat suppression (T2-FLAIR-FS) in dogs with meningoencephalitis. Dogs with meningoencephalitis and dogs with idiopathic epilepsy were retrospectively identified and anonymized. Evaluators recorded the presence or absence of lesions within 12 predetermined brain regions on randomized sequences, viewing and scoring each sequence individually. Additionally, signal-to-noise ratios, contrast-to-noise ratios, and relative contrast (RC) were measured in a reference population. Short tau inversion recovery sequences had the highest RC between gray and white matter. While descriptively more lesions were identified by evaluators on T2-FLAIR-FS images, there was no statistical difference in the relative sensitivity of lesion detection between the sequences. Nor was there a statistical difference in false lesion detection within our reference population. Short tau inversion recovery may be favored for enhanced anatomic contrast depiction in brain imaging. No benefit of the inclusion of a fat-suppressed T2-FLAIR sequence was found. © 2014 American College of Veterinary Radiology.
Laterally constrained inversion for CSAMT data interpretation
Wang, Ruo; Yin, Changchun; Wang, Miaoyue; Di, Qingyun
2015-10-01
Laterally constrained inversion (LCI) has been successfully applied to the inversion of dc resistivity, TEM and airborne EM data. However, it hasn't been yet applied to the interpretation of controlled-source audio-frequency magnetotelluric (CSAMT) data. In this paper, we apply the LCI method for CSAMT data inversion by preconditioning the Jacobian matrix. We apply a weighting matrix to Jacobian to balance the sensitivity of model parameters, so that the resolution with respect to different model parameters becomes more uniform. Numerical experiments confirm that this can improve the convergence of the inversion. We first invert a synthetic dataset with and without noise to investigate the effect of LCI applications to CSAMT data, for the noise free data, the results show that the LCI method can recover the true model better compared to the traditional single-station inversion; and for the noisy data, the true model is recovered even with a noise level of 8%, indicating that LCI inversions are to some extent noise insensitive. Then, we re-invert two CSAMT datasets collected respectively in a watershed and a coal mine area in Northern China and compare our results with those from previous inversions. The comparison with the previous inversion in a coal mine shows that LCI method delivers smoother layer interfaces that well correlate to seismic data, while comparison with a global searching algorithm of simulated annealing (SA) in a watershed shows that though both methods deliver very similar good results, however, LCI algorithm presented in this paper runs much faster. The inversion results for the coal mine CSAMT survey show that a conductive water-bearing zone that was not revealed by the previous inversions has been identified by the LCI. This further demonstrates that the method presented in this paper works for CSAMT data inversion.
Directory of Open Access Journals (Sweden)
M. A. Elshafey
2014-01-01
Full Text Available This paper presents a method of error-correcting coding of digital information. Feature of this method is the treatment of cases of inversion and skip bits caused by a violation of the synchronization of the receiving and transmitting device or other factors. The article gives a brief overview of the features, characteristics, and modern methods of construction LDPC and convolutional codes, as well as considers a general model of the communication channel, taking into account the probability of bits inversion, deletion and insertion. The proposed coding scheme is based on a combination of LDPC coding and convolution coding. A comparative analysis of the proposed combined coding scheme and a coding scheme containing only LDPC coder is performed. Both of the two schemes have the same coding rate. Experiments were carried out on two models of communication channels at different probability values of bit inversion and deletion. The first model allows only random bit inversion, while the other allows both random bit inversion and deletion. In the experiments research and analysis of the delay decoding of convolutional coder is performed and the results of these experimental studies demonstrate the feasibility of planted coding scheme to improve the efficiency of data recovery that is transmitted over a communication channel with noises which allow random bit inversion and deletion without decreasing the coding rate.
Acoustic 2D full waveform inversion to solve gas cloud challenges
Directory of Open Access Journals (Sweden)
Srichand Prajapati
2015-09-01
Full Text Available The existing conventional inversion algorithm does not provide satisfactory results due to the complexity of propagated wavefield though the gas cloud. Acoustic full waveform inversion has been developed and applied to a realistic synthetic offshore shallow gas cloud feature with Student-t approach, with and without simultaneous sources encoding. As a modeling operator, we implemented the grid based finite-difference method in frequency domain using second order elastic wave equation. Jacobin operator and its adjoint provide a necessary platform for solving full waveform inversion problem in a reduced Hessian matrix. We invert gas cloud model in 5 frequency band selected from 1 to 12 Hz, each band contains 3 frequencies. The inversion results are highly sensitive to the misfit. The model allows better convergence and recovery of amplitude losses. This approach gives better resolution then the existing least-squares approach. In this paper, we implement the full waveform inversion for low frequency model with minimum number of iteration providing a better resolution of inversion results.
Inverse problems and uncertainty quantification
Litvinenko, Alexander
2013-12-18
In a Bayesian setting, inverse problems and uncertainty quantification (UQ)— the propagation of uncertainty through a computational (forward) model—are strongly connected. In the form of conditional expectation the Bayesian update becomes computationally attractive. This is especially the case as together with a functional or spectral approach for the forward UQ there is no need for time- consuming and slowly convergent Monte Carlo sampling. The developed sampling- free non-linear Bayesian update is derived from the variational problem associated with conditional expectation. This formulation in general calls for further discretisa- tion to make the computation possible, and we choose a polynomial approximation. After giving details on the actual computation in the framework of functional or spectral approximations, we demonstrate the workings of the algorithm on a number of examples of increasing complexity. At last, we compare the linear and quadratic Bayesian update on the small but taxing example of the chaotic Lorenz 84 model, where we experiment with the influence of different observation or measurement operators on the update.
Package inspection using inverse diffraction
McAulay, Alastair D.
2008-08-01
More efficient cost-effective hand-held methods of inspecting packages without opening them are in demand for security. Recent new work in TeraHertz sources,1 millimeter waves, presents new possibilities. Millimeter waves pass through cardboard and styrofoam, common packing materials, and also pass through most materials except those with high conductivity like metals which block light and are easily spotted. Estimating refractive index along the path of the beam through the package from observations of the beam passing out of the package provides the necessary information to inspect the package and is a nonlinear problem. So we use a generalized linear inverse technique that we first developed for finding oil by reflection in geophysics.2 The computation assumes parallel slices in the packet of homogeneous material for which the refractive index is estimated. A beam is propagated through this model in a forward computation. The output is compared with the actual observations for the package and an update computed for the refractive indices. The loop is repeated until convergence. The approach can be modified for a reflection system or to include estimation of absorption.
MODEL SELECTION FOR SPECTROPOLARIMETRIC INVERSIONS
International Nuclear Information System (INIS)
Asensio Ramos, A.; Manso Sainz, R.; Martínez González, M. J.; Socas-Navarro, H.; Viticchié, B.; Orozco Suárez, D.
2012-01-01
Inferring magnetic and thermodynamic information from spectropolarimetric observations relies on the assumption of a parameterized model atmosphere whose parameters are tuned by comparison with observations. Often, the choice of the underlying atmospheric model is based on subjective reasons. In other cases, complex models are chosen based on objective reasons (for instance, the necessity to explain asymmetries in the Stokes profiles) but it is not clear what degree of complexity is needed. The lack of an objective way of comparing models has, sometimes, led to opposing views of the solar magnetism because the inferred physical scenarios are essentially different. We present the first quantitative model comparison based on the computation of the Bayesian evidence ratios for spectropolarimetric observations. Our results show that there is not a single model appropriate for all profiles simultaneously. Data with moderate signal-to-noise ratios (S/Ns) favor models without gradients along the line of sight. If the observations show clear circular and linear polarization signals above the noise level, models with gradients along the line are preferred. As a general rule, observations with large S/Ns favor more complex models. We demonstrate that the evidence ratios correlate well with simple proxies. Therefore, we propose to calculate these proxies when carrying out standard least-squares inversions to allow for model comparison in the future.
Inverse Problems and Uncertainty Quantification
Litvinenko, Alexander
2014-01-06
In a Bayesian setting, inverse problems and uncertainty quantification (UQ) - the propagation of uncertainty through a computational (forward) modelare strongly connected. In the form of conditional expectation the Bayesian update becomes computationally attractive. This is especially the case as together with a functional or spectral approach for the forward UQ there is no need for time- consuming and slowly convergent Monte Carlo sampling. The developed sampling- free non-linear Bayesian update is derived from the variational problem associated with conditional expectation. This formulation in general calls for further discretisa- tion to make the computation possible, and we choose a polynomial approximation. After giving details on the actual computation in the framework of functional or spectral approximations, we demonstrate the workings of the algorithm on a number of examples of increasing complexity. At last, we compare the linear and quadratic Bayesian update on the small but taxing example of the chaotic Lorenz 84 model, where we experiment with the influence of different observation or measurement operators on the update.
Inverse problem in radionuclide transport
International Nuclear Information System (INIS)
Yu, C.
1988-01-01
The disposal of radioactive waste must comply with the performance objectives set forth in 10 CFR 61 for low-level waste (LLW) and 10 CFR 60 for high-level waste (HLW). To determine probable compliance, the proposed disposal system can be modeled to predict its performance. One of the difficulties encountered in such a study is modeling the migration of radionuclides through a complex geologic medium for the long term. Although many radionuclide transport models exist in the literature, the accuracy of the model prediction is highly dependent on the model parameters used. The problem of using known parameters in a radionuclide transport model to predict radionuclide concentrations is a direct problem (DP); whereas the reverse of DP, i.e., the parameter identification problem of determining model parameters from known radionuclide concentrations, is called the inverse problem (IP). In this study, a procedure to solve IP is tested, using the regression technique. Several nonlinear regression programs are examined, and the best one is recommended. 13 refs., 1 tab
Reverse Universal Resolving Algorithm and inverse driving
DEFF Research Database (Denmark)
Pécseli, Thomas
2012-01-01
Inverse interpretation is a semantics based, non-standard interpretation of programs. Given a program and a value, an inverse interpreter finds all or one of the inputs, that would yield the given value as output with normal forward evaluation. The Reverse Universal Resolving Algorithm is a new v...
Third Harmonic Imaging using a Pulse Inversion
DEFF Research Database (Denmark)
Rasmussen, Joachim; Du, Yigang; Jensen, Jørgen Arendt
2011-01-01
The pulse inversion (PI) technique can be utilized to separate and enhance harmonic components of a waveform for tissue harmonic imaging. While most ultrasound systems can perform pulse inversion, only few image the 3rd harmonic component. PI pulse subtraction can isolate and enhance the 3rd...
Metaheuristic optimization of acoustic inverse problems.
van Leijen, A.V.; Rothkrantz, L.; Groen, F.
2011-01-01
Swift solving of geoacoustic inverse problems strongly depends on the application of a global optimization scheme. Given a particular inverse problem, this work aims to answer the questions how to select an appropriate metaheuristic search strategy, and how to configure it for optimal performance.
Inverse Filtering Techniques in Speech Analysis | Nwachuku ...
African Journals Online (AJOL)
inverse filtering' has been applied. The unifying features of these techniques are presented, namely: 1. a basis in the source-filter theory of speech production, 2. the use of a network whose transfer function is the inverse of the transfer function of ...
Energy Technology Data Exchange (ETDEWEB)
Paffhausen, M.W.; Smith, D.L.; Ugaki, S.N.
1990-09-01
This report describes Phase I of the Solvent Recycle/Recovery Task of the DOE Chlorinated Solvent Substitution Program for the US Air Force by the Idaho National Engineering Laboratory, EG G Idaho, Inc., through the US Department of Energy, Idaho Operations Office. The purpose of the task is to identify and test recovery and recycling technologies for proposed substitution solvents identified by the Biodegradable Solvent Substitution Program and the Alternative Solvents/Technologies for Paint Stripping Program with the overall objective of minimizing hazardous wastes. A literature search to identify recycle/recovery technologies and initial distillation studies has been conducted. 4 refs.
Inverse m-matrices and ultrametric matrices
Dellacherie, Claude; San Martin, Jaime
2014-01-01
The study of M-matrices, their inverses and discrete potential theory is now a well-established part of linear algebra and the theory of Markov chains. The main focus of this monograph is the so-called inverse M-matrix problem, which asks for a characterization of nonnegative matrices whose inverses are M-matrices. We present an answer in terms of discrete potential theory based on the Choquet-Deny Theorem. A distinguished subclass of inverse M-matrices is ultrametric matrices, which are important in applications such as taxonomy. Ultrametricity is revealed to be a relevant concept in linear algebra and discrete potential theory because of its relation with trees in graph theory and mean expected value matrices in probability theory. Remarkable properties of Hadamard functions and products for the class of inverse M-matrices are developed and probabilistic insights are provided throughout the monograph.
Fast wavelet based sparse approximate inverse preconditioner
Energy Technology Data Exchange (ETDEWEB)
Wan, W.L. [Univ. of California, Los Angeles, CA (United States)
1996-12-31
Incomplete LU factorization is a robust preconditioner for both general and PDE problems but unfortunately not easy to parallelize. Recent study of Huckle and Grote and Chow and Saad showed that sparse approximate inverse could be a potential alternative while readily parallelizable. However, for special class of matrix A that comes from elliptic PDE problems, their preconditioners are not optimal in the sense that independent of mesh size. A reason may be that no good sparse approximate inverse exists for the dense inverse matrix. Our observation is that for this kind of matrices, its inverse entries typically have piecewise smooth changes. We can take advantage of this fact and use wavelet compression techniques to construct a better sparse approximate inverse preconditioner. We shall show numerically that our approach is effective for this kind of matrices.
Solving inverse problems of optical microlithography
Granik, Yuri
2005-05-01
The direct problem of microlithography is to simulate printing features on the wafer under given mask, imaging system, and process characteristics. The goal of inverse problems is to find the best mask and/or imaging system and/or process to print the given wafer features. In this study we will describe and compare solutions of inverse mask problems. Pixel-based inverse problem of mask optimization (or "layout inversion") is harder than inverse source problem, especially for partially-coherent systems. It can be stated as a non-linear constrained minimization problem over complex domain, with large number of variables. We compare method of Nashold projections, variations of Fienap phase-retrieval algorithms, coherent approximation with deconvolution, local variations, and descent searches. We propose electrical field caching technique to substantially speedup the searching algorithms. We demonstrate applications of phase-shifted masks, assist features, and maskless printing.
Recurrent Neural Network for Computing Outer Inverse.
Živković, Ivan S; Stanimirović, Predrag S; Wei, Yimin
2016-05-01
Two linear recurrent neural networks for generating outer inverses with prescribed range and null space are defined. Each of the proposed recurrent neural networks is based on the matrix-valued differential equation, a generalization of dynamic equations proposed earlier for the nonsingular matrix inversion, the Moore-Penrose inversion, as well as the Drazin inversion, under the condition of zero initial state. The application of the first approach is conditioned by the properties of the spectrum of a certain matrix; the second approach eliminates this drawback, though at the cost of increasing the number of matrix operations. The cases corresponding to the most common generalized inverses are defined. The conditions that ensure stability of the proposed neural network are presented. Illustrative examples present the results of numerical simulations.
Forward modeling. Route to electromagnetic inversion
Energy Technology Data Exchange (ETDEWEB)
Groom, R.; Walker, P. [PetRos EiKon Incorporated, Ontario (Canada)
1996-05-01
Inversion of electromagnetic data is a topical subject in the literature, and much time has been devoted to understanding the convergence properties of various inverse methods. The relative lack of success of electromagnetic inversion techniques is partly attributable to the difficulties in the kernel forward modeling software. These difficulties come in two broad classes: (1) Completeness and robustness, and (2) convergence, execution time and model simplicity. If such problems exist in the forward modeling kernel, it was demonstrated that inversion can fail to generate reasonable results. It was suggested that classical inversion techniques, which are based on minimizing a norm of the error between data and the simulated data, will only be successful when these difficulties in forward modeling kernels are properly dealt with. 4 refs., 5 figs.
Stochastic Gabor reflectivity and acoustic impedance inversion
Hariri Naghadeh, Diako; Morley, Christopher Keith; Ferguson, Angus John
2018-02-01
To delineate subsurface lithology to estimate petrophysical properties of a reservoir, it is possible to use acoustic impedance (AI) which is the result of seismic inversion. To change amplitude to AI, removal of wavelet effects from the seismic signal in order to get a reflection series, and subsequently transforming those reflections to AI, is vital. To carry out seismic inversion correctly it is important to not assume that the seismic signal is stationary. However, all stationary deconvolution methods are designed following that assumption. To increase temporal resolution and interpretation ability, amplitude compensation and phase correction are inevitable. Those are pitfalls of stationary reflectivity inversion. Although stationary reflectivity inversion methods are trying to estimate reflectivity series, because of incorrect assumptions their estimations will not be correct, but may be useful. Trying to convert those reflection series to AI, also merging with the low frequency initial model, can help us. The aim of this study was to apply non-stationary deconvolution to eliminate time variant wavelet effects from the signal and to convert the estimated reflection series to the absolute AI by getting bias from well logs. To carry out this aim, stochastic Gabor inversion in the time domain was used. The Gabor transform derived the signal’s time–frequency analysis and estimated wavelet properties from different windows. Dealing with different time windows gave an ability to create a time-variant kernel matrix, which was used to remove matrix effects from seismic data. The result was a reflection series that does not follow the stationary assumption. The subsequent step was to convert those reflections to AI using well information. Synthetic and real data sets were used to show the ability of the introduced method. The results highlight that the time cost to get seismic inversion is negligible related to general Gabor inversion in the frequency domain. Also
NON-INVASIVE INVERSE PROBLEM IN CIVIL ENGINEERING
Directory of Open Access Journals (Sweden)
Jan Havelka
2017-11-01
Full Text Available In this contribution we focus on recovery of spatial distribution of material parameters utilizing only non-invasive boundary measurements. Such methods has gained its importance as imaging techniques in medicine, geophysics or archaeology. We apply similar principles for non-stationary heat transfer in civil engineering. In oppose to standard technique which rely on external loading devices, we assume the natural fluctuation of temperature throughout day and night can provide sufficient information to recover the underlying material parameters. The inverse problem was solved by a modified regularised Gauss-Newton iterative scheme and the underlying forward problem is solved with a finite element space-time discretisation. We show a successful reconstruction of material parameters on a synthetic example with real measurements. The virtual experiment also reveals the insensitivity to practical precision of sensor measurements.
Lalov, E.; Linde, N.; Vrugt, J.A.
2012-01-01
Time-lapse geophysical measurements are widely used to monitor the movement of water and solutes through the subsurface. Yet commonly used deterministic least squares inversions typically suffer from relatively poor mass recovery, spread overestimation, and limited ability to appropriately estimate
Role of Diffusion-Weighted Magnetic Resonance Imaging in Diffuse Axonal Injury
Energy Technology Data Exchange (ETDEWEB)
Ezaki, Y.; Tsutsumi, K.; Morikawa, M.; Nagata, I. [Nagasaki Univ., Graduate School of Medicine (Japan). Depts. of Neurosurgery and Radiology
2006-09-15
Purpose: To determine whether the signal changes on magnetic resonance imaging (MRI), including fluid attenuated inversion recovery (FLAIR), T2*-weighted gradient echo (GE) imaging, and diffusion-weighted imaging (DWI) in diffuse axonal injury (DAI) patients correlate with the clinical outcome. Material and Methods: We diagnosed patients with DAI based on the following criteria: 1) a loss of consciousness from the time of injury that persisted beyond 6 h; 2) no apparent hemorrhagic contusion on computed tomography (CT); 3) the presence of white matter injury on MRI. Twenty-one DAI patients were analyzed (19 M, 2 F, mean age 34 years) with MRI (FLAIR, T2*-weighted GE imaging, and DWI). Results: 325 abnormalities were detected by MRI within a week after injury. The T2*-weighted GE imaging was significantly more sensitive than FLAIR and DWI in diagnosing DAI. DWI detected only 32% of all lesions, but could depict additional shearing injuries not visible on either T2*-weighted GE imaging or FLAIR. The mean number of lesions in brainstem detected by DWI in the favorable group (good recovery/moderately disabled) was significantly smaller than in the unfavorable group (severely disabled/vegetative survival/death). This trend was not observed on the T2*-weighted GE imaging and FLAIR findings. Conclusion: DWI cannot detect all DAI-related lesions, but is a potentially useful imaging modality for both diagnosing and assessing patients with DAI.
Predicting functional recovery after acute ankle sprain.
Directory of Open Access Journals (Sweden)
Sean R O'Connor
Full Text Available Ankle sprains are among the most common acute musculoskeletal conditions presenting to primary care. Their clinical course is variable but there are limited recommendations on prognostic factors. Our primary aim was to identify clinical predictors of short and medium term functional recovery after ankle sprain.A secondary analysis of data from adult participants (N = 85 with an acute ankle sprain, enrolled in a randomized controlled trial was undertaken. The predictive value of variables (age, BMI, gender, injury mechanism, previous injury, weight-bearing status, medial joint line pain, pain during weight-bearing dorsiflexion and lateral hop test recorded at baseline and at 4 weeks post injury were investigated for their prognostic ability. Recovery was determined from measures of subjective ankle function at short (4 weeks and medium term (4 months follow ups. Multivariate stepwise linear regression analyses were undertaken to evaluate the association between the aforementioned variables and functional recovery.Greater age, greater injury grade and weight-bearing status at baseline were associated with lower function at 4 weeks post injury (p<0.01; adjusted R square=0.34. Greater age, weight-bearing status at baseline and non-inversion injury mechanisms were associated with lower function at 4 months (p<0.01; adjusted R square=0.20. Pain on medial palpation and pain on dorsiflexion at 4 weeks were the most valuable prognostic indicators of function at 4 months (p< 0.01; adjusted R square=0.49.The results of the present study provide further evidence that ankle sprains have a variable clinical course. Age, injury grade, mechanism and weight-bearing status at baseline provide some prognostic information for short and medium term recovery. Clinical assessment variables at 4 weeks were the strongest predictors of recovery, explaining 50% of the variance in ankle function at 4 months. Further prospective research is required to highlight the factors
Developments in inverse photoemission spectroscopy
International Nuclear Information System (INIS)
Sheils, W.; Leckey, R.C.G.; Riley, J.D.
1996-01-01
In the 1950's and 1960's, Photoemission Spectroscopy (PES) established itself as the major technique for the study of the occupied electronic energy levels of solids. During this period the field divided into two branches: X-ray Photoemission Spectroscopy (XPS) for photon energies greater than ∼l000eV, and Ultra-violet Photoemission Spectroscopy (UPS) for photon energies below ∼100eV. By the 1970's XPS and UPS had become mature techniques. Like XPS, BIS (at x-ray energies) does not have the momentum-resolving ability of UPS that has contributed much to the understanding of the occupied band structures of solids. BIS moved into a new energy regime in 1977 when Dose employed a Geiger-Mueller tube to obtain density of unoccupied states data from a tantalum sample at a photon energy of ∼9.7eV. At similar energies, the technique has since become known as Inverse Photoemission Spectroscopy (IPS), in acknowledgment of its complementary relationship to UPS and to distinguish it from the higher energy BIS. Drawing on decades of UPS expertise, IPS has quickly moved into areas of interest where UPS has been applied; metals, semiconductors, layer compounds, adsorbates, ferromagnets, and superconductors. At La Trobe University an IPS facility has been constructed. This presentation reports on developments in the experimental and analytical techniques of IPS that have been made there. The results of a study of the unoccupied bulk and surface bands of GaAs are presented
Energy Technology Data Exchange (ETDEWEB)
Oh, Jong Kap [Dept. of Radiology, Cheomdan Medical Center, Gwangju (Korea, Republic of); Im, Jung Yeol [Dept. of Digital Management Information Graduate School of Nambu Univesity, Gwangju (Korea, Republic of)
2009-09-15
Diffusion-weighted imaging (DWI) has been demonstrated to be a practical method for the diagnosis of various brain diseases such as acute infarction, brain tumor, and white matter disease. In this study, we used two techniques to examine the average signal intensity (SI) and apparent diffusion coefficient (ADC) of the brains of patients who ranged in age from 10 to 60 years. Our results indicated that the average SI was the highest in amygdala (as derived from DWI), whereas that in the cerebrospinal fluid was the lowest. The average ADC was the highest in the cerebrospinal fluid, whereas the lowest measurement was derived from the pons. The average SI and ADC were higher in T{sub 2}-DW-EPI than in FLAIR-DW-EPI. The higher the b-value, the smaller the average difference in both imaging techniques; the lower the b-value, the greater the average difference. Also, comparative analysis of the brains of patients who had experienced cerebral infarction showed no distinct lesion in the general MR image over time. However, there was a high SI in apparent weighted images. Analysis of other brain diseases (e.g., bleeding, acute, subacute, chronic infarction) indicated SI variance in accordance with characteristics of the two techniques. The higher the SI, the lower the ADC. Taken together, the value of SI and ADC in accordance with frequently occurring areas and various brain disease varies based on the b-value and imaging technique. Because they provide additional useful information in the diagnosis and treatment of patients with various brain diseases through signal recognition, the proper imaging technique and b-value are important for the detection and interpretation of subacute stroke and other brain diseases.
FEMA Disaster Recovery Centers
Department of Homeland Security — This is a search site for FEMA's Disaster Recovery Centers (DRC). A DRC is a readily accessible facility or mobile office set up by FEMA where applicants may go for...
U.S. Department of Health & Human Services — The Recovery Audit Programs mission is to identify and correct Medicare improper payments through the efficient detection and collection of overpayments made on...
National Oceanic and Atmospheric Administration, Department of Commerce — The Recovery Action Mapping Tool is a web map that allows users to visually interact with and query actions that were developed to recover species listed under the...
Mercury's Internal Magnetic Field: Modeling Core Fields with Smooth Inversions
Uno, H.; Johnson, C. L.; Anderson, B. J.; Korth, H.; Purucker, M. E.; Solomon, S. C.
2008-12-01
MESSENGER's second flyby (M2) of Mercury on 6 October 2008 will provide significantly improved geographical sampling of the planet's internal magnetic field over previous measurements. Latitudinal coverage and spacecraft altitudes will be similar to those during MESSENGER's first encounter (M1), but the spacecraft trajectory will be displaced by about 180° in longitude, yielding the first magnetic measurements in the western hemisphere. We investigate spatial structure in Mercury's internal magnetic field by applying methods from inverse theory to construct low-degree-and-order spherical harmonic models. External fields predicted by a parameterized magnetospheric model are subtracted from the vector field observations. The approach takes into account noise contributions from long-wavelength uncertainties in the external field models, unexplained short-wavelength features, and spacecraft attitude errors. We investigate the effect of different regularization (smoothness) constraints on our inversions. Analyses of data from M1 and the two Mariner 10 flybys that penetrated the magnetosphere yield a preferred spherical harmonic solution to degree and order eight with the centered, axial dipole term g10 dominating. The model shows structure at low and mid-latitude regions near the flybys. Terms predicted by an analytical model for long- wavelength crustal fields - namely g10, g30 and g32 - are present, but their relative amplitudes are not consistent with such a field. We conclude that structure in our models is dominated by core, rather than by crustal, fields. We also investigate, through simulations, field morphologies that are recoverable while the spacecraft is in orbit about Mercury, under the assumption that the long-wavelength contributions from external sources can be accurately modeled and removed. Although the elliptical orbit of MESSENGER will impede the recovery of southern hemisphere structure, we obtain excellent recovery of the dipole field and of
Determination of transient fluid temperature using the inverse method
Directory of Open Access Journals (Sweden)
Jaremkiewicz Magdalena
2014-03-01
Full Text Available This paper proposes an inverse method to obtain accurate measurements of the transient temperature of fluid. A method for unit step and linear rise of temperature is presented. For this purpose, the thermometer housing is modelled as a full cylindrical element (with no inner hole, divided into four control volumes. Using the control volume method, the heat balance equations can be written for each of the nodes for each of the control volumes. Thus, for a known temperature in the middle of the cylindrical element, the distribution of temperature in three nodes and heat flux at the outer surface were obtained. For a known value of the heat transfer coefficient the temperature of the fluid can be calculated using the boundary condition. Additionally, results of experimental research are presented. The research was carried out during the start-up of an experimental installation, which comprises: a steam generator unit, an installation for boiler feed water treatment, a tray-type deaerator, a blow down flashvessel for heat recovery, a steam pressure reduction station, a boiler control system and a steam header made of martensitic high alloy P91 steel. Based on temperature measurements made in the steam header using the inverse method, accurate measurements of the transient temperature of the steam were obtained. The results of the calculations are compared with the real temperature of the steam, which can be determined for a known pressure and enthalpy.
Synthetic inversions for density using seismic and gravity data
Blom, Nienke; Boehm, Christian; Fichtner, Andreas
2017-05-01
Density variations drive mass transport in the Earth from plate tectonics to convection in the mantle and core. Nevertheless, density remains poorly known because most geophysical measurements used to probe the Earth's interior either have little sensitivity to density, suffer from trade-offs or from non-uniqueness. With the ongoing expansion of computational power, it has become possible to accurately model complete seismic wavefields in a 3-D heterogeneous Earth, and to develop waveform inversion techniques that account for complicated wavefield effects. This may help to improve resolution of density. Here, we present a pilot study where we explore the extent to which waveform inversion may be used to better recover density as a separate, independent parameter. We perform numerical simulations in 2-D to investigate under which conditions, and to what extent density anomalies may be recovered in the Earth's mantle. We conclude that density can indeed be constrained by seismic waveforms, mainly as a result of scattering effects at density contrasts. As a consequence, the low-frequency part of the wavefield is the most important for constraining the actual extent of anomalies. While the impact of density heterogeneities on the wavefield is small compared to the effects of velocity variations, it is likely to be detectable in modern regional- to global-scale measurements. We also conclude that the use of gravity data as additional information does not help to further improve the recovery of density anomalies unless strong a priori constraints on the geometry of density variations are applied. This is a result of the inherent physical non-uniqueness of potential-field inverse problems. Finally, in the limited numerical setup that we employ, we find that the initially supplied anomalies in S- and P-velocity models are of minor importance.
Convex blind image deconvolution with inverse filtering
Lv, Xiao-Guang; Li, Fang; Zeng, Tieyong
2018-03-01
Blind image deconvolution is the process of estimating both the original image and the blur kernel from the degraded image with only partial or no information about degradation and the imaging system. It is a bilinear ill-posed inverse problem corresponding to the direct problem of convolution. Regularization methods are used to handle the ill-posedness of blind deconvolution and get meaningful solutions. In this paper, we investigate a convex regularized inverse filtering method for blind deconvolution of images. We assume that the support region of the blur object is known, as has been done in a few existing works. By studying the inverse filters of signal and image restoration problems, we observe the oscillation structure of the inverse filters. Inspired by the oscillation structure of the inverse filters, we propose to use the star norm to regularize the inverse filter. Meanwhile, we use the total variation to regularize the resulting image obtained by convolving the inverse filter with the degraded image. The proposed minimization model is shown to be convex. We employ the first-order primal-dual method for the solution of the proposed minimization model. Numerical examples for blind image restoration are given to show that the proposed method outperforms some existing methods in terms of peak signal-to-noise ratio (PSNR), structural similarity (SSIM), visual quality and time consumption.
DEFF Research Database (Denmark)
Kellman, Peter; Bandettini, W Patricia; Mancini, Christine
2015-01-01
BACKGROUND: Quantitative measurement of T1 in the myocardium may be used to detect both focal and diffuse disease processes such as interstitial fibrosis or edema. A partial volume problem exists when a voxel in the myocardium also contains fat. Partial volume with fat occurs at tissue boundaries...... imaging protocols using balanced steady state free precession are considered. In-vivo imaging with T1-mapping, water/fat separated imaging, and late enhancement imaging was performed on subjects with chronic myocardial infarction. RESULTS: In n = 17 subjects with chronic myocardial infarction, lipomatous...... agreement with simulation of the specific imaging protocols. CONCLUSIONS: Measurement of the myocardial T1 by widely used balanced steady state free precession mapping methods is subject to bias when there is a mixture of water and fat in the myocardium. Intramyocardial fat is frequently present...
A posteriori error estimates in voice source recovery
Leonov, A. S.; Sorokin, V. N.
2017-12-01
The inverse problem of voice source pulse recovery from a segment of a speech signal is under consideration. A special mathematical model is used for the solution that relates these quantities. A variational method of solving inverse problem of voice source recovery for a new parametric class of sources, that is for piecewise-linear sources (PWL-sources), is proposed. Also, a technique for a posteriori numerical error estimation for obtained solutions is presented. A computer study of the adequacy of adopted speech production model with PWL-sources is performed in solving the inverse problems for various types of voice signals, as well as corresponding study of a posteriori error estimates. Numerical experiments for speech signals show satisfactory properties of proposed a posteriori error estimates, which represent the upper bounds of possible errors in solving the inverse problem. The estimate of the most probable error in determining the source-pulse shapes is about 7-8% for the investigated speech material. It is noted that a posteriori error estimates can be used as a criterion of the quality for obtained voice source pulses in application to speaker recognition.
3rd Annual Workshop on Inverse Problem
2015-01-01
This proceeding volume is based on papers presented on the Third Annual Workshop on Inverse Problems which was organized by the Department of Mathematical Sciences, Chalmers University of Technology and University of Gothenburg, and took place in May 2013 in Stockholm. The purpose of this workshop was to present new analytical developments and numerical techniques for solution of inverse problems for a wide range of applications in acoustics, electromagnetics, optical fibers, medical imaging, geophysics, etc. The contributions in this volume reflect these themes and will be beneficial to researchers who are working in the area of applied inverse problems.
Inverse Raman effect: applications and detection techniques
International Nuclear Information System (INIS)
Hughes, L.J. Jr.
1980-08-01
The processes underlying the inverse Raman effect are qualitatively described by comparing it to the more familiar phenomena of conventional and stimulated Raman scattering. An experession is derived for the inverse Raman absorption coefficient, and its relationship to the stimulated Raman gain is obtained. The power requirements of the two fields are examined qualitatively and quantitatively. The assumption that the inverse Raman absorption coefficient is constant over the interaction length is examined. Advantages of the technique are discussed and a brief survey of reported studies is presented
Inverse Raman effect: applications and detection techniques
Energy Technology Data Exchange (ETDEWEB)
Hughes, L.J. Jr.
1980-08-01
The processes underlying the inverse Raman effect are qualitatively described by comparing it to the more familiar phenomena of conventional and stimulated Raman scattering. An experession is derived for the inverse Raman absorption coefficient, and its relationship to the stimulated Raman gain is obtained. The power requirements of the two fields are examined qualitatively and quantitatively. The assumption that the inverse Raman absorption coefficient is constant over the interaction length is examined. Advantages of the technique are discussed and a brief survey of reported studies is presented.
Multiparameter Optimization for Electromagnetic Inversion Problem
Directory of Open Access Journals (Sweden)
M. Elkattan
2017-10-01
Full Text Available Electromagnetic (EM methods have been extensively used in geophysical investigations such as mineral and hydrocarbon exploration as well as in geological mapping and structural studies. In this paper, we developed an inversion methodology for Electromagnetic data to determine physical parameters of a set of horizontal layers. We conducted Forward model using transmission line method. In the inversion part, we solved multi parameter optimization problem where, the parameters are conductivity, dielectric constant, and permeability of each layer. The optimization problem was solved by simulated annealing approach. The inversion methodology was tested using a set of models representing common geological formations.
Population inversion in a stationary recombining plasma
International Nuclear Information System (INIS)
Otsuka, M.
1980-01-01
Population inversion, which occurs in a recombining plasma when a stationary He plasma is brought into contact with a neutral gas, is examined. With hydrogen as a contact gas, noticeable inversion between low-lying levels of H as been found. The overpopulation density is of the order of 10 8 cm -3 , which is much higher then that (approx. =10 5 cm -3 ) obtained previously with He as a contact gas. Relations between these experimental results and the conditions for population inversion are discussed with the CR model
Inverse design methods for radiative transfer systems
International Nuclear Information System (INIS)
Daun, K.J.; Howell, J.R.
2005-01-01
Radiant enclosures used in industrial processes have traditionally been designed by trial-and-error, a technique that usually demands considerable time to find a solution of limited quality. As an alternative, designers have recently adopted optimization and inverse methodologies to solve design problems involving radiative transfer; the optimization methodology solves the inverse problem implicitly by transforming it into a multivariable minimization problem, while the inverse design methodology solves the problem explicitly using regularization. This paper presents the details of both methodologies, and demonstrates them by solving for the optimal heater settings in an industrially relevant radiant enclosure design problem
The factorization method for inverse problems
Kirsch, Andreas
2008-01-01
The factorization method is a relatively new method for solving certain types of inverse scattering problems and problems in tomography. Aimed at students and researchers in Applied Mathematics, Physics and Engineering, this text introduces the reader to this promising approach for solving important classes of inverse problems. The wide applicability of this method is discussed by choosing typical examples, such as inverse scattering problems for the scalar Helmholtz equation, ascattering problem for Maxwell's equation, and a problem in impedance and optical tomography. The last section of the
Geoacoustic inversion using combustive sound source signals.
Potty, Gopu R; Miller, James H; Wilson, Preston S; Lynch, James F; Newhall, Arthur
2008-09-01
Combustive sound source (CSS) data collected on single hydrophone receiving units, in water depths ranging from 65 to 110 m, during the Shallow Water 2006 experiment clearly show modal dispersion effects and are suitable for modal geoacoustic inversions. CSS shots were set off at 26 m depth in 100 m of water. The inversions performed are based on an iterative scheme using dispersion-based short time Fourier transform in which each time-frequency tiling is adaptively rotated in the time-frequency plane, depending on the local wave dispersion. Results of the inversions are found to compare favorably to local core data.
BOOK REVIEW: Inverse Problems. Activities for Undergraduates
Yamamoto, Masahiro
2003-06-01
This book is a valuable introduction to inverse problems. In particular, from the educational point of view, the author addresses the questions of what constitutes an inverse problem and how and why we should study them. Such an approach has been eagerly awaited for a long time. Professor Groetsch, of the University of Cincinnati, is a world-renowned specialist in inverse problems, in particular the theory of regularization. Moreover, he has made a remarkable contribution to educational activities in the field of inverse problems, which was the subject of his previous book (Groetsch C W 1993 Inverse Problems in the Mathematical Sciences (Braunschweig: Vieweg)). For this reason, he is one of the most qualified to write an introductory book on inverse problems. Without question, inverse problems are important, necessary and appear in various aspects. So it is crucial to introduce students to exercises in inverse problems. However, there are not many introductory books which are directly accessible by students in the first two undergraduate years. As a consequence, students often encounter diverse concrete inverse problems before becoming aware of their general principles. The main purpose of this book is to present activities to allow first-year undergraduates to learn inverse theory. To my knowledge, this book is a rare attempt to do this and, in my opinion, a great success. The author emphasizes that it is very important to teach inverse theory in the early years. He writes; `If students consider only the direct problem, they are not looking at the problem from all sides .... The habit of always looking at problems from the direct point of view is intellectually limiting ...' (page 21). The book is very carefully organized so that teachers will be able to use it as a textbook. After an introduction in chapter 1, sucessive chapters deal with inverse problems in precalculus, calculus, differential equations and linear algebra. In order to let one gain some insight
Sensitivity analyses of acoustic impedance inversion with full-waveform inversion
Yao, Gang; da Silva, Nuno V.; Wu, Di
2018-04-01
Acoustic impedance estimation has a significant importance to seismic exploration. In this paper, we use full-waveform inversion to recover the impedance from seismic data, and analyze the sensitivity of the acoustic impedance with respect to the source-receiver offset of seismic data and to the initial velocity model. We parameterize the acoustic wave equation with velocity and impedance, and demonstrate three key aspects of acoustic impedance inversion. First, short-offset data are most suitable for acoustic impedance inversion. Second, acoustic impedance inversion is more compatible with the data generated by density contrasts than velocity contrasts. Finally, acoustic impedance inversion requires the starting velocity model to be very accurate for achieving a high-quality inversion. Based upon these observations, we propose a workflow for acoustic impedance inversion as: (1) building a background velocity model with travel-time tomography or reflection waveform inversion; (2) recovering the intermediate wavelength components of the velocity model with full-waveform inversion constrained by Gardner’s relation; (3) inverting the high-resolution acoustic impedance model with short-offset data through full-waveform inversion. We verify this workflow by the synthetic tests based on the Marmousi model.
Full traveltime inversion in source domain
Liu, Lu
2017-06-01
This paper presents a new method of source-domain full traveltime inversion (FTI). The objective of this study is automatically building near-surface velocity using the early arrivals of seismic data. This method can generate the inverted velocity that can kinetically best match the reconstructed plane-wave source of early arrivals with true source in source domain. It does not require picking first arrivals for tomography, which is one of the most challenging aspects of ray-based tomographic inversion. Besides, this method does not need estimate the source wavelet, which is a necessity for receiver-domain wave-equation velocity inversion. Furthermore, we applied our method on one synthetic dataset; the results show our method could generate a reasonable background velocity even when shingling first arrivals exist and could provide a good initial velocity for the conventional full waveform inversion (FWI).
n-Colour self-inverse compositions
Indian Academy of Sciences (India)
colour self-inverse composition. This introduces four new sequences which satisfy the same recurrence relation with different initial conditions like the famous Fibonacci and Lucas sequences. For these new sequences explicit formulas, recurrence ...
Inverse Doppler Effects in Broadband Acoustic Metamaterials.
Zhai, S L; Zhao, X P; Liu, S; Shen, F L; Li, L L; Luo, C R
2016-08-31
The Doppler effect refers to the change in frequency of a wave source as a consequence of the relative motion between the source and an observer. Veselago theoretically predicted that materials with negative refractions can induce inverse Doppler effects. With the development of metamaterials, inverse Doppler effects have been extensively investigated. However, the ideal material parameters prescribed by these metamaterial design approaches are complex and also challenging to obtain experimentally. Here, we demonstrated a method of designing and experimentally characterising arbitrary broadband acoustic metamaterials. These omni-directional, double-negative, acoustic metamaterials are constructed with 'flute-like' acoustic meta-cluster sets with seven double meta-molecules; these metamaterials also overcome the limitations of broadband negative bulk modulus and mass density to provide a region of negative refraction and inverse Doppler effects. It was also shown that inverse Doppler effects can be detected in a flute, which has been popular for thousands of years in Asia and Europe.
n-Colour self-inverse compositions
Indian Academy of Sciences (India)
inverse composition. This introduces four new sequences which satisfy the same recurrence relation with different initial conditions like the famous Fibonacci and Lucas sequences. For these new sequences explicit formulas, recurrence relations ...
Parametric optimization of inverse trapezoid oleophobic surfaces
DEFF Research Database (Denmark)
Cavalli, Andrea; Bøggild, Peter; Okkels, Fridolin
2012-01-01
In this paper, we introduce a comprehensive and versatile approach to the parametric shape optimization of oleophobic surfaces. We evaluate the performance of inverse trapezoid microstructures in terms of three objective parameters: apparent contact angle, maximum sustainable hydrostatic pressure...
An inverse method for radiation transport
Energy Technology Data Exchange (ETDEWEB)
Favorite, J. A. (Jeffrey A.); Sanchez, R. (Richard)
2004-01-01
Adjoint functions have been used with forward functions to compute gradients in implicit (iterative) solution methods for inverse problems in optical tomography, geoscience, thermal science, and other fields, but only once has this approach been used for inverse solutions to the Boltzmann transport equation. In this paper, this approach is used to develop an inverse method that requires only angle-independent flux measurements, rather than angle-dependent measurements as was done previously. The method is applied to a simplified form of the transport equation that does not include scattering. The resulting procedure uses measured values of gamma-ray fluxes of discrete, characteristic energies to determine interface locations in a multilayer shield. The method was implemented with a Newton-Raphson optimization algorithm, and it worked very well in numerical one-dimensional spherical test cases. A more sophisticated optimization method would better exploit the potential of the inverse method.
The inverse square law of gravitation
International Nuclear Information System (INIS)
Cook, A.H.
1987-01-01
The inverse square law of gravitation is very well established over the distances of celestial mechanics, while in electrostatics the law has been shown to be followed to very high precision. However, it is only within the last century that any laboratory experiments have been made to test the inverse square law for gravitation, and all but one has been carried out in the last ten years. At the same time, there has been considerable interest in the possibility of deviations from the inverse square law, either because of a possible bearing on unified theories of forces, including gravitation or, most recently, because of a possible additional fifth force of nature. In this article the various lines of evidence for the inverse square law are summarized, with emphasis upon the recent laboratory experiments. (author)
Bayesian inversion of refraction seismic traveltime data
Ryberg, T.; Haberland, Ch
2018-03-01
We apply a Bayesian Markov chain Monte Carlo (McMC) formalism to the inversion of refraction seismic, traveltime data sets to derive 2-D velocity models below linear arrays (i.e. profiles) of sources and seismic receivers. Typical refraction data sets, especially when using the far-offset observations, are known as having experimental geometries which are very poor, highly ill-posed and far from being ideal. As a consequence, the structural resolution quickly degrades with depth. Conventional inversion techniques, based on regularization, potentially suffer from the choice of appropriate inversion parameters (i.e. number and distribution of cells, starting velocity models, damping and smoothing constraints, data noise level, etc.) and only local model space exploration. McMC techniques are used for exhaustive sampling of the model space without the need of prior knowledge (or assumptions) of inversion parameters, resulting in a large number of models fitting the observations. Statistical analysis of these models allows to derive an average (reference) solution and its standard deviation, thus providing uncertainty estimates of the inversion result. The highly non-linear character of the inversion problem, mainly caused by the experiment geometry, does not allow to derive a reference solution and error map by a simply averaging procedure. We present a modified averaging technique, which excludes parts of the prior distribution in the posterior values due to poor ray coverage, thus providing reliable estimates of inversion model properties even in those parts of the models. The model is discretized by a set of Voronoi polygons (with constant slowness cells) or a triangulated mesh (with interpolation within the triangles). Forward traveltime calculations are performed by a fast, finite-difference-based eikonal solver. The method is applied to a data set from a refraction seismic survey from Northern Namibia and compared to conventional tomography. An inversion test
Population inversion in recombining hydrogen plasma
International Nuclear Information System (INIS)
Furukane, Utaro; Yokota, Toshiaki; Oda, Toshiatsu.
1978-11-01
The collisional-radiative model is applied to a recombining hydrogen plasma in order to investigate the plasma condition in which the population inversion between the energy levels of hydrogen can be generated. The population inversion is expected in a plasma where the three body recombination has a large contribution to the recombining processes and the effective recombination rate is beyond a certain value for a given electron density and temperature. Calculated results are presented in figures and tables. (author)
Approximation of Bayesian Inverse Problems for PDEs
Cotter, S. L.; Dashti, M.; Stuart, A. M.
2010-01-01
Inverse problems are often ill posed, with solutions that depend sensitively on data.n any numerical approach to the solution of such problems, regularization of some form is needed to counteract the resulting instability. This paper is based on an approach to regularization, employing a Bayesian formulation of the problem, which leads to a notion of well posedness for inverse problems, at the level of probability measures. The stability which results from this well posedness may be used as t...
On the Inversion of the Lidar Equation
1984-11-01
sectitns briefly review the major inversion methods to date and a fourth section describes the development of the modified inversion method. All four...can be seeu when It is understood ’in terms of its ,physical significance. Equation 17 states that the normalized integrated backscatter has a limit. In...still give significant errors. 4.0 VALIDATION OF AGILE In this chapter, evidence of the success of AGILE will be reviewed and compared with Klett’s
Porosity Estimation By Artificial Neural Networks Inversion . Application to Algerian South Field
Eladj, Said; Aliouane, Leila; Ouadfeul, Sid-Ali
2017-04-01
One of the main geophysicist's current challenge is the discovery and the study of stratigraphic traps, this last is a difficult task and requires a very fine analysis of the seismic data. The seismic data inversion allows obtaining lithological and stratigraphic information for the reservoir characterization . However, when solving the inverse problem we encounter difficult problems such as: Non-existence and non-uniqueness of the solution add to this the instability of the processing algorithm. Therefore, uncertainties in the data and the non-linearity of the relationship between the data and the parameters must be taken seriously. In this case, the artificial intelligence techniques such as Artificial Neural Networks(ANN) is used to resolve this ambiguity, this can be done by integrating different physical properties data which requires a supervised learning methods. In this work, we invert the acoustic impedance 3D seismic cube using the colored inversion method, then, the introduction of the acoustic impedance volume resulting from the first step as an input of based model inversion method allows to calculate the Porosity volume using the Multilayer Perceptron Artificial Neural Network. Application to an Algerian South hydrocarbon field clearly demonstrate the power of the proposed processing technique to predict the porosity for seismic data, obtained results can be used for reserves estimation, permeability prediction, recovery factor and reservoir monitoring. Keywords: Artificial Neural Networks, inversion, non-uniqueness , nonlinear, 3D porosity volume, reservoir characterization .
Fast nonlinear susceptibility inversion with variational regularization.
Milovic, Carlos; Bilgic, Berkin; Zhao, Bo; Acosta-Cabronero, Julio; Tejos, Cristian
2018-01-10
Quantitative susceptibility mapping can be performed through the minimization of a function consisting of data fidelity and regularization terms. For data consistency, a Gaussian-phase noise distribution is often assumed, which breaks down when the signal-to-noise ratio is low. A previously proposed alternative is to use a nonlinear data fidelity term, which reduces streaking artifacts, mitigates noise amplification, and results in more accurate susceptibility estimates. We hereby present a novel algorithm that solves the nonlinear functional while achieving computation speeds comparable to those for a linear formulation. We developed a nonlinear quantitative susceptibility mapping algorithm (fast nonlinear susceptibility inversion) based on the variable splitting and alternating direction method of multipliers, in which the problem is split into simpler subproblems with closed-form solutions and a decoupled nonlinear inversion hereby solved with a Newton-Raphson iterative procedure. Fast nonlinear susceptibility inversion performance was assessed using numerical phantom and in vivo experiments, and was compared against the nonlinear morphology-enabled dipole inversion method. Fast nonlinear susceptibility inversion achieves similar accuracy to nonlinear morphology-enabled dipole inversion but with significantly improved computational efficiency. The proposed method enables accurate reconstructions in a fraction of the time required by state-of-the-art quantitative susceptibility mapping methods. Magn Reson Med, 2018. © 2018 International Society for Magnetic Resonance in Medicine. © 2018 International Society for Magnetic Resonance in Medicine.
Atmospheric inverse modeling via sparse reconstruction
Directory of Open Access Journals (Sweden)
N. Hase
2017-10-01
Full Text Available Many applications in atmospheric science involve ill-posed inverse problems. A crucial component of many inverse problems is the proper formulation of a priori knowledge about the unknown parameters. In most cases, this knowledge is expressed as a Gaussian prior. This formulation often performs well at capturing smoothed, large-scale processes but is often ill equipped to capture localized structures like large point sources or localized hot spots. Over the last decade, scientists from a diverse array of applied mathematics and engineering fields have developed sparse reconstruction techniques to identify localized structures. In this study, we present a new regularization approach for ill-posed inverse problems in atmospheric science. It is based on Tikhonov regularization with sparsity constraint and allows bounds on the parameters. We enforce sparsity using a dictionary representation system. We analyze its performance in an atmospheric inverse modeling scenario by estimating anthropogenic US methane (CH4 emissions from simulated atmospheric measurements. Different measures indicate that our sparse reconstruction approach is better able to capture large point sources or localized hot spots than other methods commonly used in atmospheric inversions. It captures the overall signal equally well but adds details on the grid scale. This feature can be of value for any inverse problem with point or spatially discrete sources. We show an example for source estimation of synthetic methane emissions from the Barnett shale formation.
Atmospheric inverse modeling via sparse reconstruction
Hase, Nils; Miller, Scot M.; Maaß, Peter; Notholt, Justus; Palm, Mathias; Warneke, Thorsten
2017-10-01
Many applications in atmospheric science involve ill-posed inverse problems. A crucial component of many inverse problems is the proper formulation of a priori knowledge about the unknown parameters. In most cases, this knowledge is expressed as a Gaussian prior. This formulation often performs well at capturing smoothed, large-scale processes but is often ill equipped to capture localized structures like large point sources or localized hot spots. Over the last decade, scientists from a diverse array of applied mathematics and engineering fields have developed sparse reconstruction techniques to identify localized structures. In this study, we present a new regularization approach for ill-posed inverse problems in atmospheric science. It is based on Tikhonov regularization with sparsity constraint and allows bounds on the parameters. We enforce sparsity using a dictionary representation system. We analyze its performance in an atmospheric inverse modeling scenario by estimating anthropogenic US methane (CH4) emissions from simulated atmospheric measurements. Different measures indicate that our sparse reconstruction approach is better able to capture large point sources or localized hot spots than other methods commonly used in atmospheric inversions. It captures the overall signal equally well but adds details on the grid scale. This feature can be of value for any inverse problem with point or spatially discrete sources. We show an example for source estimation of synthetic methane emissions from the Barnett shale formation.
International Nuclear Information System (INIS)
Terai, Fujio; Furuya, Masaaki; Ugai, Masaru.
1992-01-01
The device of the present invention comprises a fiber scope for taking a recovery operation portion and an obstacle into a field of vision and photographing the state of the operation in the recovery operation portion and a display section for displaying the photographed image at a remote place. Concretely, the monitor of a remote operation section displays an image photographed by the fiber scope. A operation unit attached with a forceps and a fiber scope are brought closer, for example, to a fuel assembly in a reactor in the recovery operation portion. Then, the obstacle intruded into a minute space between fuels is recovered by the forceps while displaying state of the operation on the monitor of the remote operation section. Such a device certainly recover and remove a minute obstacle present in such a circumstance that a man's hand can not access, by the operation conducted under visual confirmation. (I.S.)
Iosa, Marco; Guariglia, Cecilia; Matano, Alessandro; Paolucci, Stefano; Pizzamiglio, Luigi
2016-12-01
Extrapersonal unilateral spatial neglect after stroke is associated to a poor rehabilitation outcome. Minor attention has been paid to the recovery of personal neglect, to its relationship with the recovery of extrapersonal neglect and of independency in activities of daily living. The present study aims at evaluating whether there is an association between recovery of extrapersonal and personal neglect. The secondary aim was to investigate if personal neglect may affect the effectiveness of neurorehabilitation in patients with subacute stroke. Observational study. Neurorehabilitation Hospital in Rome, Italy, inpatients. A sample of 49 patients with unilateral spatial neglect resulting from right ischemic cerebral infarction was enrolled in this study, divided into three subgroups according to the presence and the degree of personal neglect, and evaluated pre and postneurorehabilitation. Personal neglect was evaluated using Zoccolotti and Judica's Scale, extrapersonal neglect using Letter Cancellation Test, Barrage Test, Sentence Reading Test and Wundt-Jastrow Area Illusion Test. Barthel Index (BI), Rivermead Mobility Index, and Canadian Neurological Scale were also administered. Results showed the following: 1) recovery of personal neglect was not significantly correlated with that of extrapersonal neglect, despite both the disorders were ameliorated after a "non-specific" rehabilitation treatment; 2) personal neglect per se was not an additional negative prognostic factor in the rehabilitation findings. Our results suggested that the recoveries of the two types of neglect are independent from each other, and that the presence of personal neglect does not imply significant additional problems to the functional outcomes. Our study highlighted the need of novel tools to assess the presence and to improve the recovery of personal neglect.
An application of sparse inversion on the calculation of the inverse data space of geophysical data
Saragiotis, Christos
2011-07-01
Multiple reflections as observed in seismic reflection measurements often hide arrivals from the deeper target reflectors and need to be removed. The inverse data space provides a natural separation of primaries and surface-related multiples, as the surface multiples map onto the area around the origin while the primaries map elsewhere. However, the calculation of the inverse data is far from trivial as theory requires infinite time and offset recording. Furthermore regularization issues arise during inversion. We perform the inversion by minimizing the least-squares norm of the misfit function and by constraining the 1 norm of the solution, being the inverse data space. In this way a sparse inversion approach is obtained. We show results on field data with an application to surface multiple removal. © 2011 IEEE.
International Nuclear Information System (INIS)
A. Hutton; D. Arenius; J. Benesch; S. Chattopadhyay; E. F. Daly; O. Garza; R. Kazimi; R. Lauzi; L. Merminga; W. Merz; R. Nelson; W. Oren; M. Poelker; P. Powers; J. Preble; V. Ganni; C. R. Reece; R. Rimmer; M. Spata; S. Suhring
2004-01-01
Hurricane Isabel, originally a Category 5 storm, arrived at Jefferson Lab on September 18, 2003 with winds of only 75 mph, creating little direct damage to the infrastructure. However, electric power was lost for four days allowing the superconducting cryomodules to warm up and causing a total loss of the liquid helium. The subsequent recovery of the cryomodules and the impact of the considerable amount of opportunistic preventive maintenance provides important lessons for all accelerator complexes, not only those with superconducting elements. The details of how the recovery process was structured and the resulting improvement in accelerator availability will be discussed in detail
Ventilation with heat recovery
DEFF Research Database (Denmark)
Tommerup, Henrik M.; Svendsen, Svend
2005-01-01
This paper presents the experiences from the use of ventilation with heat recovery in several experimental single-family houses developed and built within the last four years to meet the new Danish energy requirements of 2005. Included are descriptions of the ventilation system components...... and the main functional demands as well as measurements of the thermal efficiency, electricity consumptions and building air tightness. The paper addresses the aspects of minimizing the heat loss from the duct system and the heat recovery unit (when placed in an unheated attic space) in order to obtain...
Chromatid Painting for Chromosomal Inversion Detection, Phase I
National Aeronautics and Space Administration — We propose a novel approach to the detection of chromosomal inversions. Transmissible chromosome aberrations (translocations and inversions) have profound genetic...
Recovery of SIMS depth profiles with account for nonstationary effects
International Nuclear Information System (INIS)
Yunin, Pavel Andreevich; Drozdov, Yurii Nikolaevich; Drozdov, Mikhail Nikolaevich; Yurasov, Dmitry Vladimirovich
2014-01-01
In this work we consider a method of accounting for the nonstationary effects in recovery of SIMS depth profiles. The depth resolution function (DRF) is described by Hofmann's nonstationary MRI (mixing-roughness-information depth) model using the depth-dependent parameters. The effects in question include the nonstationary atomic mixing and development of surface roughness. A mathematical description of the nonstationary depth profiling process by the Fredholm integral equation of the first kind is proposed. The inverse problem is solved using an algorithm based on the Tikhonov regularization method. The proposed nonstationary recovery method is tested on both model and real structures. The development of surface roughness in SIMS depth profiling of the real structure was observed. Grazing incidence x-ray reflectometry (XRR) technique was used to verify the results of SIMS profiles restoration for periodic structure containing thin Ge layers in the Si matrix. The advantages of the proposed recovery algorithm to allow for the nonstationary effects are shown.
International Nuclear Information System (INIS)
Mojisola, A.
2002-01-01
Improved reservoir characterization has been a major factor in the worldwide gain in oil recovery efficiencies over the last decades. This is because inadequate reservoir characterization, usually due to lack of appropriate tools can cause significant errors in petroleum reservoir performance prediction thereby preventing the full potential of a reservoir from being achieved. This work employs the use of wireline logs and the seismic inversion process to characterize the reservoirs in the Lancelot field. An initial reservoir analysis was carried out using the wireline evaluation. Five potential reservoirs were delineated. Thereafter reservoir parameters such as porosity, water saturation, water saturation, net-to-gross ratio of the delineated reservoirs were estimated. The seismic inversion process depends on four factors; the wavelet, the tie between the well logs and the seismic, the inversion algorithm employed and the initial model. Therefore before the main inversion, parameter tests were carried out to determine the best wavelet extraction algorithm and best inversion algorithm suited for he available data. A wavelet with a length of 70ms and a taper length of 20ms gave a close approximation of a zero phase wavelet with a stable spectrum and high dominant frequency. Based on quantitative assessment of the available inversion algorithms, the constrained blocky inversion produced the best result. Acoustic impedance, velocity and porosity sections were produced from the inverted input seismic. By incorporating geological and wireline evaluation results as constraints, the output from the inversion process were analysed. The result shows lateral variation in the reservoirs qualities of the delineated reservoirs. The seismic inversion process confirmed the Rotliegend sandstone as a prospect with a range of porosity predicted from the inversion
Cost Recovery Through Depreciation.
Forrester, Robert T.; Wesolowski, Leonard V.
1983-01-01
The approach of adopting depreciation rather than use allowance in order to recover more accurately the cost of college buildings and equipment used on federal projects is considered. It is suggested that depreciation will offer most colleges and universities a higher annual recovery rate, and an opportunity for better facilities planning. For…
Harris, Kitty S.; Kimball, Thomas G.; Casiraghi, Ann M.; Maison, Sara J.
2014-01-01
More than ever, people are seeking substance use disorder treatment during the adolescent and young adult stages of development. Developmentally, many of these young adults new to recovery are in the process of making career decisions that may require attendance at a college or university. However, the collegiate environment is not conducive to a…
DEFF Research Database (Denmark)
Jørgensen, Christoffer C; Kehlet, Henrik
2014-01-01
We read with great interest the special article by Smart and Daniels discussing several important topics of perioperative care, especially regarding lack of consensus on the definition of "postoperative recovery", and need for further understanding of the pathogenic mechanisms. However, we disagree...
Difficulty of MRI based identification of lesion age by acute infra-tentorial ischemic stroke.
Directory of Open Access Journals (Sweden)
Florian Grosse-Dresselhaus
Full Text Available Systemic thrombolysis in acute ischemic stroke is restricted to the 4.5 h time window. Many patients are excluded from this treatment because symptom onset is unknown. Magnetic resonance imaging (MRI studies have shown that stroke patients presenting with acute supra-tentorial diffusion-weighted imaging (DWI lesions that do not have matching lesions on fluid attenuated inversion recovery (FLAIR are likely to be within a 4.5 hour time window. This study examines the DWI-FLAIR mismatch in infra-tentorial stroke.This was a retrospectively conducted substudy of the "1000+" study; a prospective, single-center observational study (http://clinicaltrials.gov; NCT00715533. Fifty-six patients with infra-tentorial stroke confirmed by MRI and known symptom onset who underwent the scan within 24 h after symptom onset were analysed. Two neurologists blinded to clinical information separately rated the DWI lesion visibility on FLAIR. Lesion volume, relative signal intensities of DWI and relative apparent diffusion coefficient values were determined.Regarding baseline characteristics our study population had a median age of 66 years, a median time from symptom onset to MRI of 616.5 minutes, a median NIHSS of 3 and a median DWI lesion volume of 0.26 ml. A negative FLAIR allocated patients to a time window under 4.5 h correctly with a sensitivity of 55% and a specificity of 61%, a positive predictive value of 44% and a negative predictive value of 71%. FLAIR positivity decreased with age (p = 0.018, and showed no significant correlation to lesion volume (p = 0.145.In our study the DWI-FLAIR-Mismatch does not help to reliably identify patients within 4.5 h of symptom onset in acute ischemic infra-tentorial stroke. Thus therapeutical decisions based on the DWI-FLAIR mismatch estimation of time from onset cannot be recommended in patients with infra-tentorial stroke.
QCD-instantons and conformal inversion symmetry
International Nuclear Information System (INIS)
Klammer, D.
2006-07-01
Instantons are an essential and non-perturbative part of Quantum Chromodynamics, the theory of strong interactions. One of the most relevant quantities in the instanton calculus is the instanton-size distribution, which can be described on the one hand within the framework of instanton perturbation theory and on the other hand investigated numerically by means of lattice computations. A rapid onset of a drastic discrepancy between these respective results indicates that the underlying physics is not yet well understood. In this work we investigate the appealing possibility of a symmetry under conformal inversion of space-time leading to this deviation. The motivation being that the lattice data seem to be invariant under an inversion of the instanton size. Since the instanton solution of a given size turns into an anti-instanton solution having an inverted size under conformal inversion of space-time, we ask in a first investigation, whether this property is transferred to the quantum level. In order to introduce a new scale, which is indicated by the lattice data and corresponds to the average instanton size as inversion radius, we project the instanton calculus onto the four-dimensional surface of a five-dimensional sphere via stereographic projection. The radius of this sphere is associated with the average instanton size. The result for the instanton size-distribution projected onto the sphere agrees surprisingly well with the lattice data at qualitative level. The resulting symmetry under an inversion of the instanton size is almost perfect. (orig.)
QCD-instantons and conformal inversion symmetry
Energy Technology Data Exchange (ETDEWEB)
Klammer, D.
2006-07-15
Instantons are an essential and non-perturbative part of Quantum Chromodynamics, the theory of strong interactions. One of the most relevant quantities in the instanton calculus is the instanton-size distribution, which can be described on the one hand within the framework of instanton perturbation theory and on the other hand investigated numerically by means of lattice computations. A rapid onset of a drastic discrepancy between these respective results indicates that the underlying physics is not yet well understood. In this work we investigate the appealing possibility of a symmetry under conformal inversion of space-time leading to this deviation. The motivation being that the lattice data seem to be invariant under an inversion of the instanton size. Since the instanton solution of a given size turns into an anti-instanton solution having an inverted size under conformal inversion of space-time, we ask in a first investigation, whether this property is transferred to the quantum level. In order to introduce a new scale, which is indicated by the lattice data and corresponds to the average instanton size as inversion radius, we project the instanton calculus onto the four-dimensional surface of a five-dimensional sphere via stereographic projection. The radius of this sphere is associated with the average instanton size. The result for the instanton size-distribution projected onto the sphere agrees surprisingly well with the lattice data at qualitative level. The resulting symmetry under an inversion of the instanton size is almost perfect. (orig.)
Unwrapped phase inversion with an exponential damping
Choi, Yun Seok
2015-07-28
Full-waveform inversion (FWI) suffers from the phase wrapping (cycle skipping) problem when the frequency of data is not low enough. Unless we obtain a good initial velocity model, the phase wrapping problem in FWI causes a result corresponding to a local minimum, usually far away from the true solution, especially at depth. Thus, we have developed an inversion algorithm based on a space-domain unwrapped phase, and we also used exponential damping to mitigate the nonlinearity associated with the reflections. We construct the 2D phase residual map, which usually contains the wrapping discontinuities, especially if the model is complex and the frequency is high. We then unwrap the phase map and remove these cycle-based jumps. However, if the phase map has several residues, the unwrapping process becomes very complicated. We apply a strong exponential damping to the wavefield to eliminate much of the residues in the phase map, thus making the unwrapping process simple. We finally invert the unwrapped phases using the back-propagation algorithm to calculate the gradient. We progressively reduce the damping factor to obtain a high-resolution image. Numerical examples determined that the unwrapped phase inversion with a strong exponential damping generated convergent long-wavelength updates without low-frequency information. This model can be used as a good starting model for a subsequent inversion with a reduced damping, eventually leading to conventional waveform inversion.
RUMBLE Technical Report on Inversion Models
Simons, Dick G.; Ainslie, Michael A.; Muller, Simonette H. E.; Boek, Wilco
2002-06-01
The performance of long range low frequency active sonar (LFAS) systems in shallow water is very sensitive to the properties of the sea bed, because of the impact of these on propagation, reverberation and (to a lesser extent) ambient noise. Direct measurement of sea bed parameters using cores or grab samples is impractical for covering a wide area, and instead we consider the possibility of using the LFAS system itself to measure its operating environment. The advantages of this approach are that it exploits existing (or planned) equipment and potentially offers a wide coverage. Geo-acoustic inversion methods are reviewed, with particular consideration for the problems associated with inversion of reverberation data. Three global optimisation methods are described, known as "simulated annealing", "genetic algorithms" and "differential evolution". The Levenberg-Marquardt and downhill simplex local methods are also described. The advantages and disadvantages of each individual method, as well as some hybrid combinations, are discussed in the context of geo-acoustic inversion. A new inversion method has been developed that exploits both the shape and height of the reverberation vs time curve to obtain information about the sea bed reflection loss and scattering strength separately. Tests on synthetic reverberation data show that the inversion method is able to extract parameters representing reflection loss and scattering strength, but cannot always unambiguously separate the effects of sediment sound speed and attenuation. The method is robust to small mismatches in water depth, sonar depth, sediment sound speed gradient and wind speed.
Full wave-field reflection coefficient inversion.
Dettmer, Jan; Dosso, Stan E; Holland, Charles W
2007-12-01
This paper develops a Bayesian inversion for recovering multilayer geoacoustic (velocity, density, attenuation) profiles from a full wave-field (spherical-wave) seabed reflection response. The reflection data originate from acoustic time series windowed for a single bottom interaction, which are processed to yield reflection coefficient data as a function of frequency and angle. Replica data for inversion are computed using a wave number-integration model to calculate the full complex acoustic pressure field, which is processed to produce a commensurate seabed response function. To address the high computational cost of calculating short range acoustic fields, the inversion algorithms are parallelized and frequency averaging is replaced by range averaging in the forward model. The posterior probability density is interpreted in terms of optimal parameter estimates, marginal distributions, and credibility intervals. Inversion results for the full wave-field seabed response are compared to those obtained using plane-wave reflection coefficients. A realistic synthetic study indicates that the plane-wave assumption can fail, producing erroneous results with misleading uncertainty bounds, whereas excellent results are obtained with the full-wave reflection inversion.
Multiscattering inversion for low-model wavenumbers
Alkhalifah, Tariq Ali
2016-09-21
A successful full-waveform inversion implementation updates the low-wavenumber model components first for a proper description of the wavefield propagation and slowly adds the high wavenumber potentially scattering parts of the model. The low-wavenumber components can be extracted from the transmission parts of the recorded wavefield emanating directly from the source or the transmission parts from the single- or double-scattered wavefield computed from a predicted scatter field acting as secondary sources.We use a combined inversion of data modeled from the source and those corresponding to single and double scattering to update the velocity model and the component of the velocity (perturbation) responsible for the single and double scattering. The combined inversion helps us access most of the potential model wavenumber information that may be embedded in the data. A scattering-angle filter is used to divide the gradient of the combined inversion, so initially the high-wavenumber (low-scattering-angle) components of the gradient are directed to the perturbation model and the low-wavenumber (highscattering- angle) components are directed to the velocity model. As our background velocity matures, the scatteringangle divide is slowly lowered to allow for more of the higher wavenumbers to contribute the velocity model. Synthetic examples including the Marmousi model are used to demonstrate the additional illumination and improved velocity inversion obtained when including multiscattered energy. © 2016 Society of Exploration Geophysicists.
Alternating minimisation for glottal inverse filtering
Rodrigo Bleyer, Ismael; Lybeck, Lasse; Auvinen, Harri; Airaksinen, Manu; Alku, Paavo; Siltanen, Samuli
2017-06-01
A new method is proposed for solving the glottal inverse filtering (GIF) problem. The goal of GIF is to separate an acoustical speech signal into two parts: the glottal airflow excitation and the vocal tract filter. To recover such information one has to deal with a blind deconvolution problem. This ill-posed inverse problem is solved under a deterministic setting, considering unknowns on both sides of the underlying operator equation. A stable reconstruction is obtained using a double regularization strategy, alternating between fixing either the glottal source signal or the vocal tract filter. This enables not only splitting the nonlinear and nonconvex problem into two linear and convex problems, but also allows the use of the best parameters and constraints to recover each variable at a time. This new technique, called alternating minimization glottal inverse filtering (AM-GIF), is compared with two other approaches: Markov chain Monte Carlo glottal inverse filtering (MCMC-GIF), and iterative adaptive inverse filtering (IAIF), using synthetic speech signals. The recent MCMC-GIF has good reconstruction quality but high computational cost. The state-of-the-art IAIF method is computationally fast but its accuracy deteriorates, particularly for speech signals of high fundamental frequency (F0). The results show the competitive performance of the new method: With high F0, the reconstruction quality is better than that of IAIF and close to MCMC-GIF while reducing the computational complexity by two orders of magnitude.
Speaker independent acoustic-to-articulatory inversion
Ji, An
Acoustic-to-articulatory inversion, the determination of articulatory parameters from acoustic signals, is a difficult but important problem for many speech processing applications, such as automatic speech recognition (ASR) and computer aided pronunciation training (CAPT). In recent years, several approaches have been successfully implemented for speaker dependent models with parallel acoustic and kinematic training data. However, in many practical applications inversion is needed for new speakers for whom no articulatory data is available. In order to address this problem, this dissertation introduces a novel speaker adaptation approach called Parallel Reference Speaker Weighting (PRSW), based on parallel acoustic and articulatory Hidden Markov Models (HMM). This approach uses a robust normalized articulatory space and palate referenced articulatory features combined with speaker-weighted adaptation to form an inversion mapping for new speakers that can accurately estimate articulatory trajectories. The proposed PRSW method is evaluated on the newly collected Marquette electromagnetic articulography -- Mandarin Accented English (EMA-MAE) corpus using 20 native English speakers. Cross-speaker inversion results show that given a good selection of reference speakers with consistent acoustic and articulatory patterns, the PRSW approach gives good speaker independent inversion performance even without kinematic training data.
Backup and recovery of Oracle Database using Recovery Manager
Hubáček, Filip
2009-01-01
The bachelor's thesis discusses the implementation of backup and recovery of Oracle database using Recovery Manager. There are described individual backup types available in Oracle database environment and recovery types. Author introduces the benefits of using Recovery Manager, as the main backup tool in comparison to other methods of performing backup / restore.The reader is acquaint with the results of tests of the possible backup types. The tested features are speed of backup operation, t...
Ramig, Keith; Subramaniam, Gopal; Karimi, Sasan; Szalda, David J; Ko, Allen; Lam, Aaron; Li, Jeffrey; Coaderaj, Ani; Cavdar, Leyla; Bogdan, Lukasz; Kwon, Kitae; Greer, Edyta M
2016-04-15
A series of 2,4-disubstituted 1H-1-benzazepines, 2a-d, 4, and 6, were studied, varying both the substituents at C2 and C4 and at the nitrogen atom. The conformational inversion (ring-flip) and nitrogen-atom inversion (N-inversion) energetics were studied by variable-temperature NMR spectroscopy and computations. The steric bulk of the nitrogen-atom substituent was found to affect both the conformation of the azepine ring and the geometry around the nitrogen atom. Also affected were the Gibbs free energy barriers for the ring-flip and the N-inversion. When the nitrogen-atom substituent was alkyl, as in 2a-c, the geometry of the nitrogen atom was nearly planar and the azepine ring was highly puckered; the result was a relatively high-energy barrier to ring-flip and a low barrier to N-inversion. Conversely, when the nitrogen-atom substituent was a hydrogen atom, as in 2d, 4, and 6, the nitrogen atom was significantly pyramidalized and the azepine ring was less puckered; the result here was a relatively high energy barrier to N-inversion and a low barrier to ring-flip. In these N-unsubstituted compounds, it was found computationally that the lowest-energy stereodynamic process was ring-flip coupled with N-inversion, as N-inversion alone had a much higher energy barrier.
Recovery capital pathways: Modelling the components of recovery wellbeing.
Cano, Ivan; Best, David; Edwards, Michael; Lehman, John
2017-12-01
In recent years, there has been recognition that recovery is a journey that involves the growth of recovery capital. Thus, recovery capital has become a commonly used term in addiction treatment and research yet its operationalization and measurement has been limited. Due to these limitations, there is little understanding of long-term recovery pathways and their clinical application. We used the data of 546 participants from eight different recovery residences spread across Florida, USA. We calculated internal consistency for recovery capital and wellbeing, then assessed their factor structure via confirmatory factor analysis. The relationships between time, recovery barriers and strengths, wellbeing and recovery capital, as well as the moderating effect of gender, were estimated using structural equations modelling. The proposed model obtained an acceptable fit (χ 2 (141, N=546)=533.642, pwellbeing. Gender differences were observed. We tested the pathways to recovery for residents in the recovery housing population. Our results have implications not only for retention as a predictor of sustained recovery and wellbeing but also for the importance of meaningful activities in promoting recovery capital and wellbeing. Copyright © 2017 Elsevier B.V. All rights reserved.
Introducing Recovery Style for Modeling and Analyzing System Recovery
Sözer, Hasan; Tekinerdogan, B.; Kruchten, P.; Garlan, D.; Woods, E.
An analysis of the existing approaches for representing architectural views reveals that they focus mainly on functional concerns and are limited when considering quality concerns. We introduce the recovery style for modeling the structure of the system related to the recovery concern. The recovery
Oil core microcapsules by inverse gelation technique.
Martins, Evandro; Renard, Denis; Davy, Joëlle; Marquis, Mélanie; Poncelet, Denis
2015-01-01
A promising technique for oil encapsulation in Ca-alginate capsules by inverse gelation was proposed by Abang et al. This method consists of emulsifying calcium chloride solution in oil and then adding it dropwise in an alginate solution to produce Ca-alginate capsules. Spherical capsules with diameters around 3 mm were produced by this technique, however the production of smaller capsules was not demonstrated. The objective of this study is to propose a new method of oil encapsulation in a Ca-alginate membrane by inverse gelation. The optimisation of the method leads to microcapsules with diameters around 500 μm. In a search of microcapsules with improved diffusion characteristics, the size reduction is an essential factor to broaden the applications in food, cosmetics and pharmaceuticals areas. This work contributes to a better understanding of the inverse gelation technique and allows the production of microcapsules with a well-defined shell-core structure.
Fuzzy logic guided inverse treatment planning
International Nuclear Information System (INIS)
Yan Hui; Yin Fangfang; Guan Huaiqun; Kim, Jae Ho
2003-01-01
A fuzzy logic technique was applied to optimize the weighting factors in the objective function of an inverse treatment planning system for intensity-modulated radiation therapy (IMRT). Based on this technique, the optimization of weighting factors is guided by the fuzzy rules while the intensity spectrum is optimized by a fast-monotonic-descent method. The resultant fuzzy logic guided inverse planning system is capable of finding the optimal combination of weighting factors for different anatomical structures involved in treatment planning. This system was tested using one simulated (but clinically relevant) case and one clinical case. The results indicate that the optimal balance between the target dose and the critical organ dose is achieved by a refined combination of weighting factors. With the help of fuzzy inference, the efficiency and effectiveness of inverse planning for IMRT are substantially improved
Surface Vibration Reconstruction using Inverse Numerical Acoustics
Directory of Open Access Journals (Sweden)
F. Martinus
2003-05-01
Full Text Available This paper explores the use of inverse numerical acoustics to reconstruct the surface vibration of a noise source. Inverse numerical acoustics is mainly used for source identification. This approach uses the measured sound pressure at a set of field points and the Helmholtz integral equation to reconstruct the normal surface velocity. The number of sound pressure measurements is considerably less than the number of surface vibration nodes. An overview of inverse numerical acoustics is presented and compared with other holography techniques such as nearfield acoustical holography and the Helmholtz equation least squares method. In order to obtain an acceptable reproduction of the surface vibration, several critical factors such as the field point selection and the effect of experimental errors have to be handled properly. Other practical considerations such as the use of few measured velocities and regularization techniques will also be presented. Examples will include a diesel engine, a transmission housing and an engine cover.
Inverse problems in linear transport theory
International Nuclear Information System (INIS)
Dressler, K.
1988-01-01
Inverse problems for a class of linear kinetic equations are investigated. The aim is to identify the scattering kernel of a transport equation (corresponding to the structure of a background medium) by observing the 'albedo' part of the solution operator for the corresponding direct initial boundary value problem. This means to get information on some integral operator in an integrodifferential equation through on overdetermined boundary value problem. We first derive a constructive method for solving direct halfspace problems and prove a new factorization theorem for the solutions. Using this result we investigate stationary inverse problems with respect to well posedness (e.g. reduce them to classical ill-posed problems, such as integral equations of first kind). In the time-dependent case we show that a quite general inverse problem is well posed and solve it constructively. (orig.)
FAST INVERSION OF SOLAR Ca II SPECTRA
International Nuclear Information System (INIS)
Beck, C.; Choudhary, D. P.; Rezaei, R.; Louis, R. E.
2015-01-01
We present a fast (<<1 s per profile) inversion code for solar Ca II lines. The code uses an archive of spectra that are synthesized prior to the inversion under the assumption of local thermodynamic equilibrium (LTE). We show that it can be successfully applied to spectrograph data or more sparsely sampled spectra from two-dimensional spectrometers. From a comparison to a non-LTE inversion of the same set of spectra, we derive a first-order non-LTE correction to the temperature stratifications derived in the LTE approach. The correction factor is close to unity up to log τ ∼ –3 and increases to values of 2.5 and 4 at log τ = –6 in the quiet Sun and the umbra, respectively
Applications of inverse and algebraic scattering theories
International Nuclear Information System (INIS)
Amos, K.
1997-01-01
Inverse scattering theories, algebraic scattering theory and exactly solvable scattering potentials are diverse ways by which scattering potentials can be defined from S-functions specified by fits to fixed energy, quantal scattering data. Applications have been made in nuclear (heavy ion and nucleon-nucleus scattering), atomic and molecular (electron scattering from simple molecules) systems. Three inverse scattering approaches are considered in detail; the semiclassical WKB and fully quantal Lipperheide-Fiedeldey method, than algebraic scattering theory is applied to heavy ion scattering and finally the exactly solvable Ginocchio potentials. Some nuclear results are ambiguous but the atomic and molecular inversion potentials are in good agreement with postulated forms. 21 refs., 12 figs
Probabilistic inversion for chicken processing lines
Energy Technology Data Exchange (ETDEWEB)
Cooke, Roger M. [Department of Mathematics, Delft University of Technology, Delft (Netherlands)]. E-mail: r.m.cooke@ewi.tudelft.nl; Nauta, Maarten [Microbiological Laboratory for Health Protection RIVM, Bilthoven (Netherlands); Havelaar, Arie H. [Microbiological Laboratory for Health Protection RIVM, Bilthoven (Netherlands); Fels, Ine van der [Microbiological Laboratory for Health Protection RIVM, Bilthoven (Netherlands)
2006-10-15
We discuss an application of probabilistic inversion techniques to a model of campylobacter transmission in chicken processing lines. Such techniques are indicated when we wish to quantify a model which is new and perhaps unfamiliar to the expert community. In this case there are no measurements for estimating model parameters, and experts are typically unable to give a considered judgment. In such cases, experts are asked to quantify their uncertainty regarding variables which can be predicted by the model. The experts' distributions (after combination) are then pulled back onto the parameter space of the model, a process termed 'probabilistic inversion'. This study illustrates two such techniques, iterative proportional fitting (IPF) and PARmeter fitting for uncertain models (PARFUM). In addition, we illustrate how expert judgement on predicted observable quantities in combination with probabilistic inversion may be used for model validation and/or model criticism.
Probabilistic inversion for chicken processing lines
International Nuclear Information System (INIS)
Cooke, Roger M.; Nauta, Maarten; Havelaar, Arie H.; Fels, Ine van der
2006-01-01
We discuss an application of probabilistic inversion techniques to a model of campylobacter transmission in chicken processing lines. Such techniques are indicated when we wish to quantify a model which is new and perhaps unfamiliar to the expert community. In this case there are no measurements for estimating model parameters, and experts are typically unable to give a considered judgment. In such cases, experts are asked to quantify their uncertainty regarding variables which can be predicted by the model. The experts' distributions (after combination) are then pulled back onto the parameter space of the model, a process termed 'probabilistic inversion'. This study illustrates two such techniques, iterative proportional fitting (IPF) and PARmeter fitting for uncertain models (PARFUM). In addition, we illustrate how expert judgement on predicted observable quantities in combination with probabilistic inversion may be used for model validation and/or model criticism
Inverse Kinematic Analysis Of A Quadruped Robot
Directory of Open Access Journals (Sweden)
Muhammed Arif Sen
2017-09-01
Full Text Available This paper presents an inverse kinematics program of a quadruped robot. The kinematics analysis is main problem in the manipulators and robots. Dynamic and kinematic structures of quadruped robots are very complex compared to industrial and wheeled robots. In this study inverse kinematics solutions for a quadruped robot with 3 degrees of freedom on each leg are presented. Denavit-Hartenberg D-H method are used for the forward kinematic. The inverse kinematic equations obtained by the geometrical and mathematical methods are coded in MATLAB. And thus a program is obtained that calculate the legs joint angles corresponding to desired various orientations of robot and endpoints of legs. Also the program provides the body orientations of robot in graphical form. The angular positions of joints obtained corresponding to desired different orientations of robot and endpoints of legs are given in this study.
Recovery of Phenotypes Obtained by Adaptive Evolution through Inverse Metabolic Engineering
DEFF Research Database (Denmark)
Hong, Kuk-Ki; Nielsen, Jens
2012-01-01
In a previous study, system level analysis of adaptively evolved yeast mutants showing improved galactose utilization revealed relevant mutations. The governing mutations were suggested to be in the Ras/PKA signaling pathway and ergosterol metabolism. Here, site-directed mutants having one...... of the mutations RAS2Lys77, RAS2Tyr112, and ERG5Pro370 were constructed and evaluated. The mutants were also combined with overexpression of PGM2, earlier proved as a beneficial target for galactose utilization. The constructed strains were analyzed for their gross phenotype, transcriptome and targeted metabolites......, and the results were compared to those obtained from reference strains and the evolved strains. The RAS2Lys77 mutation resulted in the highest specific galactose uptake rate among all of the strains with an increased maximum specific growth rate on galactose. The RAS2Tyr112 mutation also improved the specific...
Heriyanto, M.; Srigutomo, W.
2017-07-01
Exploration of natural or energy resources requires geophysical survey to determine the subsurface structure, such as DC resistivity method. In this research, field and synthetic data were used using Schlumberger configuration. One-dimensional (1-D) DC resistivity inversion was carried out using Singular Value Decomposition (SVD) and Levenberg-Marquardt (LM) techniques to obtain layered resistivity structure. We have developed software to perform both inversion methods accompanied by a user-friendly interface. Both of the methods were compared one another to determine the number of iteration, robust to noise, elapsed time of computation, and inversion results. SVD inversion generated faster process and better results than LM did. The inversion showed both of these methods were appropriate to interpret subsurface resistivity structure.
Post-disturbance sediment recovery: Implications for watershed resilience
Rathburn, Sara L.; Shahverdian, Scott M.; Ryan, Sandra E.
2018-03-01
Sediment recovery following disturbances is a measure of the time required to attain pre-disturbance sediment fluxes. Insight into the controls on recovery processes and pathways builds understanding of geomorphic resilience. We assess post-disturbance sediment recovery in three small (1.5-100 km2), largely unaltered watersheds within the northern Colorado Rocky Mountains affected by wildfires, floods, and debris flows. Disturbance regimes span 102 (floods, debris flows) to 103 years (wildfires). For all case studies, event sediment recovery followed a nonlinear pattern: initial high sediment flux during single precipitation events or high annual snowmelt runoff followed by decreasing sediment fluxes over time. Disturbance interactions were evaluated after a high-severity fire within the South Fork Cache la Poudre basin was followed by an extreme flood one year post-fire. This compound disturbance hastened suspended sediment recovery to pre-fire concentrations 3 years after the fire. Wildfires over the last 1900 YBP in the South Fork basin indicate fire recurrence intervals of 600 years. Debris flows within the upper Colorado River basin over the last two centuries have shifted the baseline of sediment recovery caused by anthropogenic activities that increased debris flow frequency. An extreme flood on North St. Vrain Creek with an impounding reservoir resulted in extreme sedimentation that led to a physical state change. We introduce an index of resilience as sediment recovery/disturbance recurrence interval, providing a relative comparison between sites. Sediment recovery and channel form resilience may be inversely related because of high or low physical complexity in streams. We propose management guidelines to enhance geomorphic resilience by promoting natural processes that maintain physical complexity. Finally, sediment connectivity within watersheds is an additional factor to consider when establishing restoration treatment priorities.
Variability in surface inversion characteristics over India in winter ...
Indian Academy of Sciences (India)
Home; Journals; Journal of Earth System Science; Volume 120; Issue 1. Variability in surface inversion ... Decadal variations in inversion strength show weak inversion frequencies decreasing from the 1st to the 3rd decade while moderate/strong inversions occur more frequently at most stations. Frequencies of very strong ...
Trimming and procrastination as inversion techniques
Backus, George E.
1996-12-01
By examining the processes of truncating and approximating the model space (trimming it), and by committing to neither the objectivist nor the subjectivist interpretation of probability (procrastinating), we construct a formal scheme for solving linear and non-linear geophysical inverse problems. The necessary prior information about the correct model xE can be either a collection of inequalities or a probability measure describing where xE was likely to be in the model space X before the data vector y0 was measured. The results of the inversion are (1) a vector z0 that estimates some numerical properties zE of xE; (2) an estimate of the error δz = z0 - zE. As y0 is finite dimensional, so is z0, and hence in principle inversion cannot describe all of xE. The error δz is studied under successively more specialized assumptions about the inverse problem, culminating in a complete analysis of the linear inverse problem with a prior quadratic bound on xE. Our formalism appears to encompass and provide error estimates for many of the inversion schemes current in geomagnetism, and would be equally applicable in geodesy and seismology if adequate prior information were available there. As an idealized example we study the magnetic field at the core-mantle boundary, using satellite measurements of field elements at sites assumed to be almost uniformly distributed on a single spherical surface. Magnetospheric currents are neglected and the crustal field is idealized as a random process with rotationally invariant statistics. We find that an appropriate data compression diagonalizes the variance matrix of the crustal signal and permits an analytic trimming of the idealized problem.
Mesoscale inversion of carbon sources and sinks
International Nuclear Information System (INIS)
Lauvaux, T.
2008-01-01
Inverse methods at large scales are used to infer the spatial variability of carbon sources and sinks over the continents but their uncertainties remain large. Atmospheric concentrations integrate the surface flux variability but atmospheric transport models at low resolution are not able to simulate properly the local atmospheric dynamics at the measurement sites. However, the inverse estimates are more representative of the large spatial heterogeneity of the ecosystems compared to direct flux measurements. Top-down and bottom-up methods that aim at quantifying the carbon exchanges between the surface and the atmosphere correspond to different scales and are not easily comparable. During this phD, a mesoscale inverse system was developed to correct carbon fluxes at 8 km resolution. The high resolution transport model MesoNH was used to simulate accurately the variability of the atmospheric concentrations, which allowed us to reduce the uncertainty of the retrieved fluxes. All the measurements used here were observed during the intensive regional campaign CERES of May and June 2005, during which several instrumented towers measured CO 2 concentrations and fluxes in the South West of France. Airborne measurements allowed us to observe concentrations at high altitude but also CO 2 surface fluxes over large parts of the domain. First, the capacity of the inverse system to correct the CO 2 fluxes was estimated using pseudo-data experiments. The largest fraction of the concentration variability was attributed to regional surface fluxes over an area of about 300 km around the site locations depending on the meteorological conditions. Second, an ensemble of simulations allowed us to define the spatial and temporal structures of the transport errors. Finally, the inverse fluxes at 8 km resolution were compared to direct flux measurements. The inverse system has been validated in space and time and showed an improvement of the first guess fluxes from a vegetation model
Disaster Debris Recovery Database - Landfills
U.S. Environmental Protection Agency — The US EPA Disaster Debris Recovery Database (DDRD) promotes the proper recovery, recycling, and disposal of disaster debris for emergency responders at the federal,...
Brine Recovery in Containment (BRIC)
National Aeronautics and Space Administration — The Brine Residual in Containment (BRIC) system is a technology that enables recovery of water from concentrated brine wastewater. Recovery of water from...
Vector continued fractions using a generalized inverse
International Nuclear Information System (INIS)
Haydock, Roger; Nex, C M M; Wexler, Geoffrey
2004-01-01
A real vector space combined with an inverse (involution) for vectors is sufficient to define a vector continued fraction whose parameters consist of vector shifts and changes of scale. The choice of sign for different components of the vector inverse permits construction of vector analogues of the Jacobi continued fraction. These vector Jacobi fractions are related to vector and scalar-valued polynomial functions of the vectors, which satisfy recurrence relations similar to those of orthogonal polynomials. The vector Jacobi fraction has strong convergence properties which are demonstrated analytically, and illustrated numerically
Direct and Inverse problems in Electrocardiography
Boulakia, M.; Fernández, M. A.; Gerbeau, J. F.; Zemzemi, N.
2008-09-01
We present numerical results related to the direct and the inverse problems in electrocardiography. The electrical activity of the heart is described by the bidomain equations. The electrocardiograms (ECGs) recorded in different points on the body surface are obtained by coupling the bidomain equation to a Laplace equation in the torso. The simulated ECGs are quite satisfactory. As regards the inverse problem, our goal is to estimate the parameters of the bidomain-torso model. Here we present some preliminary results of a parameter estimation for the torso model.
Kinetic equation solution by inverse kinetic method
International Nuclear Information System (INIS)
Salas, G.
1983-01-01
We propose a computer program (CAMU) which permits to solve the inverse kinetic equation. The CAMU code is written in HPL language for a HP 982 A microcomputer with a peripheral interface HP 9876 A ''thermal graphic printer''. The CAMU code solves the inverse kinetic equation by taking as data entry the output of the ionization chambers and integrating the equation with the help of the Simpson method. With this program we calculate the evolution of the reactivity in time for a given disturbance
Inverse statistical approach in heartbeat time series
International Nuclear Information System (INIS)
Ebadi, H; Shirazi, A H; Mani, Ali R; Jafari, G R
2011-01-01
We present an investigation on heart cycle time series, using inverse statistical analysis, a concept borrowed from studying turbulence. Using this approach, we studied the distribution of the exit times needed to achieve a predefined level of heart rate alteration. Such analysis uncovers the most likely waiting time needed to reach a certain change in the rate of heart beat. This analysis showed a significant difference between the raw data and shuffled data, when the heart rate accelerates or decelerates to a rare event. We also report that inverse statistical analysis can distinguish between the electrocardiograms taken from healthy volunteers and patients with heart failure
Molecular seismology: an inverse problem in nanobiology.
Hinow, Peter; Boczko, Erik M
2007-05-07
The density profile of an elastic fiber like DNA will change in space and time as ligands associate with it. This observation affords a new direction in single molecule studies provided that density profiles can be measured in space and time. In fact, this is precisely the objective of seismology, where the mathematics of inverse problems have been employed with success. We argue that inverse problems in elastic media can be directly applied to biophysical problems of fiber-ligand association, and demonstrate that robust algorithms exist to perform density reconstruction in the condensed phase.
The Inverse Perspective in Byzantine Painting
Directory of Open Access Journals (Sweden)
Maria Urmă
2014-11-01
Full Text Available The inverse perspective is a method of representing spatial depth used only in Byzantine painting. It is different from Renaissance perspective (a method of realistic, conventional, subjective, subject to a single point of view. The inverse perspective, with two-dimensional axonometric representations, is more complex, offering multiple possibilities of symbolization. Various theories have considered either optical-geometric aspect or artistic-cultural aspect as the main factors that generated it. But they have not led to a unified conclusion. This study highlights the common elements of these theories, bringing together the two issues and providing a philosophical-religious interpretation.
Direct and inverse scattering for viscoelastic media
International Nuclear Information System (INIS)
Ammicht, E.; Corones, J.P.; Krueger, R.J.
1987-01-01
A time domain approach to direct and inverse scattering problems for one-dimensional viscoelastic media is presented. Such media can be characterized as having a constitutive relation between stress and strain which involves the past history of the strain through a memory function, the relaxation modulus. In the approach in this article, the relaxation modulus of a material is shown to be related to the reflection properties of the material. This relation provides a constructive algorithm for direct and inverse scattering problems. A numerical implementation of this algorithm is tested on several problems involving realistic relaxation moduli
Merminga, L
2005-01-01
Successfully operating, pioneering Energy Recovery Linac (ERL) – based Free Electron Lasers (FELs) have paved the way towards powerful and highly efficient accelerators based on the principle of energy recovery. Pursued and envisioned ERL applications worldwide include high brilliance light sources for the production of both spontaneous and FEL radiation, high-energy electron cooling devices, and electron-ion colliders. The required electron source parameters, average beam current and beam energy of the proposed applications are a significant extrapolation from demonstrated performance. We present an overview of the accelerator physics and technology challenges encountered in the design of the various ERL projects around the world, as well as progress and development plans to achieving the required performance.
DEFF Research Database (Denmark)
Gundlach, Carsten
2006-01-01
In the present thesis the development of a unique experimental method for volume characterisation of individual embedded crystallites down to a radius of 150 nm is presented. This method is applied to in-situ studies of recovery in aluminium. The method is an extension of 3DXRD microscopy, an X...... by the combined use of X-ray micro focusing optics, new scanning algorithms and the use of foils. The ratio of foil thickness to crystallite size should be at least 10 such that the central ones are situated in a bulk environment. To avoid thermal drifts, gold reference markers are deposited onto the sample...... are represented as strings. To identify the strings a combination of a 5D connected component type algorithm and multi-peak fitting was found to be superior. The first use of the method was a study of recovery of a deformed aluminium alloy (AA1050). The aluminium alloy was deformed by cold rolling to a thickness...
Illness management and recovery
DEFF Research Database (Denmark)
Dalum, Helle Stentoft; Waldemar, Anna Kristine; Korsbek, Lisa
2018-01-01
OBJECTIVE: Illness Management and Recovery (IMR) is a psychosocial intervention with a recovery-oriented approach. The program has been evaluated in different settings; however evidence for the effects of IMR is still deficient. The aim of this trial was to investigate the benefits and harms...... of the IMR program compared with treatment as usual in Danish patients with schizophrenia or bipolar disorder. METHOD: The trial was designed as a randomized, assessor-blinded, multi-center, clinical trial investigating the IMR program compared with usual treatment. 198 people diagnosed with schizophrenia...... or service utilization. CONCLUSION: This randomized trial contributes to the evidence base of IMR by providing a methodological solid base for its conclusions; however the trial has some important limitations. More research is needed to get a firm answer on the effectiveness of the IMR....
International Nuclear Information System (INIS)
Rowden, G.A.
1982-01-01
A process is provided for the recovery of uranium from an organic extractant phase containing an amine. The extractant phase is contacted in a number of mixing stages with an acidic aqueous stripping phase containing sulphate ions, and the phases are passed together through a series of mixing stages while maintaining a dispersion of droplets of one phase in the other. Uranium is precipitated from the final stage by raising the pH. An apparatus having several mixing chambers is described
International Nuclear Information System (INIS)
Marmo, A.R.
1979-01-01
An improved design of a sludge recovery apparatus used in the fabrication of nuclear fuel is described. This apparatus provides for automatic separation of sludge from the grinder coolant, drying of the sludge into a flowable powder and transfer of the dry powder to a salvage container. It can be constructed to comply with criticality-safe-geometry requirements and to obviate need for operating personnel in its immediate vicinity. (UK)
Directory of Open Access Journals (Sweden)
Mathew Carter
2013-11-01
Full Text Available Comorbidity among mood, anxiety, and alcohol disorders is common and burdensome, affecting individuals, families, and public health. A systematic and integrative review of the literature across disciplines and research methodologies was performed. Supradisciplinary approaches were applied to the review and the ensuing critical appraisal. Definitions, measurement, and estimation are controversial and inconstant. Recovery from comorbidity cannot be easily extricated from a sociocultural milieu. Methodological challenges in quantitative and qualitative research and across disciplines are many and are discussed. The evidence supporting current treatments is sparse and short-term, and modalities operating in isolation typically fail. People easily fall into the cracks between mental health and addiction services. Clinicians feel untrained and consumers bear the brunt of this: Judgmental and moralistic interactions persist and comorbidity is unrecognized in high-risk populations. Competing historical paradigms of mental illness and addiction present a barrier to progress and reductionism is an impediment to care and an obstacle to the integration and interpretation of research. What matters to consumers is challenging to quantify but worth considering: Finding employment, safe housing, and meaning are crucial to recovery. Complex social networks and peer support in recovery are important but poorly understood. The focus on modalities of limited evidence or generalizability persists in literature and practice. We need to consider different combinations of comorbidity, transitions as opposed to dichotomies of use or illness, and explore the long-term view and emic perspectives.
Sampling of finite elements for sparse recovery in large scale 3D electrical impedance tomography
International Nuclear Information System (INIS)
Javaherian, Ashkan; Moeller, Knut; Soleimani, Manuchehr
2015-01-01
This study proposes a method to improve performance of sparse recovery inverse solvers in 3D electrical impedance tomography (3D EIT), especially when the volume under study contains small-sized inclusions, e.g. 3D imaging of breast tumours. Initially, a quadratic regularized inverse solver is applied in a fast manner with a stopping threshold much greater than the optimum. Based on assuming a fixed level of sparsity for the conductivity field, finite elements are then sampled via applying a compressive sensing (CS) algorithm to the rough blurred estimation previously made by the quadratic solver. Finally, a sparse inverse solver is applied solely to the sampled finite elements, with the solution to the CS as its initial guess. The results show the great potential of the proposed CS-based sparse recovery in improving accuracy of sparse solution to the large-size 3D EIT. (paper)
Sampling of finite elements for sparse recovery in large scale 3D electrical impedance tomography.
Javaherian, Ashkan; Soleimani, Manuchehr; Moeller, Knut
2015-01-01
This study proposes a method to improve performance of sparse recovery inverse solvers in 3D electrical impedance tomography (3D EIT), especially when the volume under study contains small-sized inclusions, e.g. 3D imaging of breast tumours. Initially, a quadratic regularized inverse solver is applied in a fast manner with a stopping threshold much greater than the optimum. Based on assuming a fixed level of sparsity for the conductivity field, finite elements are then sampled via applying a compressive sensing (CS) algorithm to the rough blurred estimation previously made by the quadratic solver. Finally, a sparse inverse solver is applied solely to the sampled finite elements, with the solution to the CS as its initial guess. The results show the great potential of the proposed CS-based sparse recovery in improving accuracy of sparse solution to the large-size 3D EIT.
Anisotropic wave-equation traveltime and waveform inversion
Feng, Shihang
2016-09-06
The wave-equation traveltime and waveform inversion (WTW) methodology is developed to invert for anisotropic parameters in a vertical transverse isotropic (VTI) meidum. The simultaneous inversion of anisotropic parameters v0, ε and δ is initially performed using the wave-equation traveltime inversion (WT) method. The WT tomograms are then used as starting background models for VTI full waveform inversion. Preliminary numerical tests on synthetic data demonstrate the feasibility of this method for multi-parameter inversion.
Inverse and Ill-posed Problems Theory and Applications
Kabanikhin, S I
2011-01-01
The text demonstrates the methods for proving the existence (if et all) and finding of inverse and ill-posed problems solutions in linear algebra, integral and operator equations, integral geometry, spectral inverse problems, and inverse scattering problems. It is given comprehensive background material for linear ill-posed problems and for coefficient inverse problems for hyperbolic, parabolic, and elliptic equations. A lot of examples for inverse problems from physics, geophysics, biology, medicine, and other areas of application of mathematics are included.
Inverse Kinematics with Closed Form Solution for Denso Robot Manipulator
Prasetia, Ikhsan Eka; Agustinah, Trihastuti
2015-01-01
In this paper, the forward kinematics and inverse kinematics used on the Denso robot manipulator which has a 6-DOF. The forward kinematics will result in the desired position by end-effector, while inverse kinematics produce angel on each joint. Inverse kinematics problem are very difficult, therefor to obtain the solution of inverse kinematics using closed form solution with geometry approach. The simulation result obtained from forward kinematics and inverse kinematics is determining desire...
International Nuclear Information System (INIS)
Haider, E.; Raja, S.; Wali, W.; Tariq, M.
2013-01-01
A case of 50 years of age, male with sporadic Creutzfeldt Jakob Disease (sCJD) is reported. Patient had dementia, behavioural abnormalities, unsteady gait and myoclonic jerks. Magnetic resonance imaging (MRI) brain T2 weighted and Fluid Attenuated Inverse Recovery (FLAIR) images showed abnormally increased signal intensity in caudate nucleus and putamen. Scalp electroencephalogram (EEG) revealed periodic synchronous biphasic sharp wave complexes. On the basis of history, clinical findings, typical MRI brain and EEG changes, diagnosis of sporadic CJD was made. (author)
Introduction to inverse problems for differential equations
Hasanov Hasanoğlu, Alemdar
2017-01-01
This book presents a systematic exposition of the main ideas and methods in treating inverse problems for PDEs arising in basic mathematical models, though it makes no claim to being exhaustive. Mathematical models of most physical phenomena are governed by initial and boundary value problems for PDEs, and inverse problems governed by these equations arise naturally in nearly all branches of science and engineering. The book’s content, especially in the Introduction and Part I, is self-contained and is intended to also be accessible for beginning graduate students, whose mathematical background includes only basic courses in advanced calculus, PDEs and functional analysis. Further, the book can be used as the backbone for a lecture course on inverse and ill-posed problems for partial differential equations. In turn, the second part of the book consists of six nearly-independent chapters. The choice of these chapters was motivated by the fact that the inverse coefficient and source problems considered here a...
Seismic Waveform Inversion by Stochastic Optimization
Directory of Open Access Journals (Sweden)
Tristan van Leeuwen
2011-01-01
Full Text Available We explore the use of stochastic optimization methods for seismic waveform inversion. The basic principle of such methods is to randomly draw a batch of realizations of a given misfit function and goes back to the 1950s. The ultimate goal of such an approach is to dramatically reduce the computational cost involved in evaluating the misfit. Following earlier work, we introduce the stochasticity in waveform inversion problem in a rigorous way via a technique called randomized trace estimation. We then review theoretical results that underlie recent developments in the use of stochastic methods for waveform inversion. We present numerical experiments to illustrate the behavior of different types of stochastic optimization methods and investigate the sensitivity to the batch size and the noise level in the data. We find that it is possible to reproduce results that are qualitatively similar to the solution of the full problem with modest batch sizes, even on noisy data. Each iteration of the corresponding stochastic methods requires an order of magnitude fewer PDE solves than a comparable deterministic method applied to the full problem, which may lead to an order of magnitude speedup for waveform inversion in practice.
Modelling and inversion of local magnetic anomalies
International Nuclear Information System (INIS)
Quesnel, Y; Langlais, B; Sotin, C; Galdéano, A
2008-01-01
We present a method—named as MILMA for modelling and inversion of local magnetic anomalies—that combines forward and inverse modelling of aeromagnetic data to characterize both magnetization properties and location of unconstrained local sources. Parameters of simple-shape magnetized bodies (cylinder, prism or sphere) are first adjusted by trial and error to predict the signal. Their parameters provide a priori information for inversion of the measurements. Here, a generalized nonlinear approach with a least-squares criterion is adopted to seek the best parameters of the sphere (dipole). This inversion step allows the model to be more objectively adjusted to fit the magnetic signal. The validity of the MILMA method is demonstrated through synthetic and real cases using aeromagnetic measurements. Tests with synthetic data reveal accurate results in terms of depth source, whatever be the number of sources. The MILMA method is then used with real measurements to constrain the properties of the magnetized units of the Champtoceaux complex (France). The resulting parameters correlate with the crustal structure and properties revealed by other geological and geophysical surveys in the same area. The MILMA method can therefore be used to investigate the properties of poorly constrained lithospheric magnetized sources
Uterine inversion complicating traditional termination of pregnancy ...
African Journals Online (AJOL)
Abortion services remain cladenstine and unsafe in most parts of Africa. This is a case of a mid-trimester abortion induced by traditional methods which resulted in uterine inversion, a previously unreported complication of induced abortion. Until abortion services are accessible and safe on the continent, morbidity and ...
Homogeneity of common cosmopolitan inversion frequencies in ...
Indian Academy of Sciences (India)
Home; Journals; Journal of Genetics; Volume 84; Issue 2 ... Research Article Volume 84 Issue 2 August 2005 pp 173-178 ... To understand the genetic properties of Asian D. melanogaster populations, we initiated a population genetic study of chromosome inversion polymorphisms in hitherto unanalysed population ...
Improving Variational Autoencoders with Inverse Autoregressive Flow
Kingma, D.; Salimans, T.; Josefowicz, R.; Chen, X.; Sutskever, I.; Welling, M.; Lee, D.D.; von Luxburg, U.; Garnett, R.; Sugiyama, M.; Guyon, I.
2017-01-01
The framework of normalizing flows provides a general strategy for flexible variational inference of posteriors over latent variables. We propose a new type of normalizing flow, inverse autoregressive flow (IAF), that, in contrast to earlier published flows, scales well to high-dimensional latent
ILIGRA : An Efficient Inverse Line Graph Algorithm
Liu, D.; Trajanovski, S.; Van Mieghem, P.
2014-01-01
This paper presents a new and efficient algorithm, ILIGRA, for inverse line graph construction. Given a line graph H, ILIGRA constructs its root graph G with the time complexity being linear in the number of nodes in H. If ILIGRA does not know whether the given graph H is a line graph, it firstly
Solving Direct and Inverse Heat Conduction Problems
Taler, Jan
2006-01-01
Presents a solution for direct and inverse heat conduction problems. This work discusses the theoretical basis for the heat transfer process in the first part. It presents selected theoretical and numerical problems in the form of exercises with their subsequent solutions in the second part
Inverse scattering with supersymmetric quantum mechanics
International Nuclear Information System (INIS)
Baye, Daniel; Sparenberg, Jean-Marc
2004-01-01
The application of supersymmetric quantum mechanics to the inverse scattering problem is reviewed. The main difference with standard treatments of the inverse problem lies in the simple and natural extension to potentials with singularities at the origin and with a Coulomb behaviour at infinity. The most general form of potentials which are phase-equivalent to a given potential is discussed. The use of singular potentials allows adding or removing states from the bound spectrum without contradicting the Levinson theorem. Physical applications of phase-equivalent potentials in nuclear reactions and in three-body systems are described. Derivation of a potential from the phase shift at fixed orbital momentum can also be performed with the supersymmetric inversion by using a Bargmann-type approximation of the scattering matrix or phase shift. A unique singular potential without bound states can be obtained from any phase shift. A limited number of bound states depending on the singularity can then be added. This inversion procedure is illustrated with nucleon-nucleon scattering
Seismic processing in the inverse data space
Berkhout, A.J.
2006-01-01
Until now, seismic processing has been carried out by applying inverse filters in the forward data space. Because the acquired data of a seismic survey is always discrete, seismic measurements in the forward data space can be arranged conveniently in a data matrix (P). Each column in the data matrix
Inversion layer thermopower in high magnetic field
Energy Technology Data Exchange (ETDEWEB)
Girvin, S.M.; Jonson, M.
1982-11-20
The authors calculate the thermopower of an ideal two-dimensional electron gas (inversion layer) in a quantising magnetic field. They find that the thermopower is a universal function of the reduced temperature which has a novel dependence on the chemical potential.
Inverse Problem for a Curved Quantum Guide
Directory of Open Access Journals (Sweden)
Laure Cardoulis
2012-01-01
Full Text Available We consider the Dirichlet Laplacian operator −Δ on a curved quantum guide in ℝ n(n=2,3 with an asymptotically straight reference curve. We give uniqueness results for the inverse problem associated to the reconstruction of the curvature by using either observations of spectral data or a boot-strapping method.
Neural Network Learning as an Inverse Problem
Czech Academy of Sciences Publication Activity Database
Kůrková, Věra
2005-01-01
Roč. 13, č. 5 (2005), s. 551-559 ISSN 1367-0751 R&D Projects: GA AV ČR 1ET100300517 Institutional research plan: CEZ:AV0Z10300504 Keywords : learning from data * generalization * empirical error functional * inverse problem * evaluation operator * kernel methods Subject RIV: BA - General Mathematics Impact factor: 0.382, year: 2005
Nonlinear approximation with dictionaries. II. Inverse Estimates
DEFF Research Database (Denmark)
Gribonval, Rémi; Nielsen, Morten
2006-01-01
In this paper, which is the sequel to [16], we study inverse estimates of the Bernstein type for nonlinear approximation with structured redundant dictionaries in a Banach space. The main results are for blockwise incoherent dictionaries in Hilbert spaces, which generalize the notion of joint block...
Nonlinear approximation with dictionaries,.. II: Inverse estimates
DEFF Research Database (Denmark)
Gribonval, Rémi; Nielsen, Morten
In this paper we study inverse estimates of the Bernstein type for nonlinear approximation with structured redundant dictionaries in a Banach space. The main results are for separated decomposable dictionaries in Hilbert spaces, which generalize the notion of joint block-diagonal mutually...
Inverse acoustic problem of N homogeneous scatterers
DEFF Research Database (Denmark)
Berntsen, Svend
2002-01-01
The three-dimensional inverse acoustic medium problem of N homogeneous objects with known geometry and location is considered. It is proven that one scattering experiment is sufficient for the unique determination of the complex wavenumbers of the objects. The mapping from the scattered fields...
Probabilistic Geoacoustic Inversion in Complex Environments
2015-09-30
to capture seabed variability and uncertainties consistent with data resolution, and (2) improved numerical methods for parameter and uncertainty...advancing Bayesian inference applications. • Dettmer’s work at Australian National University in seismology is closely related to some of the methods ...long-range inversion methods can fail to provide sufficient resolution. For proper quantitative examination of variability, parameter uncertainty must
Multiscale Phase Inversion of Seismic Data
Fu, Lei
2017-12-02
We present a scheme for multiscale phase inversion (MPI) of seismic data that is less sensitive to the unmodeled physics of wave propagation and a poor starting model than standard full waveform inversion (FWI). To avoid cycle-skipping, the multiscale strategy temporally integrates the traces several times, i.e. high-order integration, to produce low-boost seismograms that are used as input data for the initial iterations of MPI. As the iterations proceed, higher frequencies in the data are boosted by using integrated traces of lower order as the input data. The input data are also filtered into different narrow frequency bands for the MPI implementation. At low frequencies, we show that MPI with windowed reflections approximates wave equation inversion of the reflection traveltimes, except no traveltime picking is needed. Numerical results with synthetic acoustic data show that MPI is more robust than conventional multiscale FWI when the initial model is far from the true model. Results from synthetic viscoacoustic and elastic data show that MPI is less sensitive than FWI to some of the unmodeled physics. Inversion of marine data shows that MPI is more robust and produces modestly more accurate results than FWI for this data set.
Tectonic inversion in the Wandel Sea Basin
DEFF Research Database (Denmark)
Svennevig, Kristian; Guarnieri, Pierpaolo; Stemmerik, Lars
2016-01-01
Sheet and an upper Hondal Elv Thrust Sheet separated by a subhorizontal fault: the Central Detachment. The style of deformation and the structures described are interpreted as the result of Paleocene-Eocene N-S directed compression resulting in basin inversion with strike-slip faults only having minor...
n-Colour self-inverse compositions
Indian Academy of Sciences (India)
functions and a summation formula are obtained. Two new binomial identities with combinatorial meaning are also given. Keywords. Compositions; n-colour compositions; self-inverse compositions; seq- uences; recurrence formulas; generating functions; binomial identities. 1. Introduction. In the classical theory of partitions, ...
Inverse problem in neutron transport and radiation
International Nuclear Information System (INIS)
Barichello, L.B.; Vilhena, M.T. de
1993-01-01
In this work the LTS N method is applied to solve a inverse problem which consists on the determination of the incident angular fluxes at the boundary from the known values of the scalar flux at interior points. Numerical simulations are presented. (author)
Swarm Level 2 Comprehensive Inversion, 2016 Production
DEFF Research Database (Denmark)
Tøffner-Clausen, Lars; Sabaka, Terence; Olsen, Nils
In the framework of the ESA Earth Observation Magnetic Mapping Mission Swarm, the Expert Support Laboratories (ESL) provides high quality Level 2 Products describing a.o. the magnetic fields of the Earth. This poster provides details of the Level 2 Products from the Comprehensive Inversion chain...
Modeling and Inversion of Scattered Surface waves
Riyanti, C.D.
2005-01-01
In this thesis, we present a modeling method based on a domain-type integral representation for waves propagating along the surface of the Earth which have been scattered in the vicinity of the source or the receivers. Using this model as starting point, we formulate an inversion scheme to estimate
Semi-Inversion of Functional Parameters
DEFF Research Database (Denmark)
Mogensen, Torben Ægidius
2008-01-01
Semi-invertering er en generalisering af invertering: Et programs semi-inverse tager nogle af dets inddata og nogen af dets uddata og returnerer de resterende ind- og uddata. Tidligere arbejder har beskrevet semi-invertering af et førsteordens funktionssprog. Vi udvider nu med funktionelle...
Normalized impedance function and the straightforward inversion ...
Indian Academy of Sciences (India)
The linear straightforward inversion scheme (SIS),developed by the authors employing the concept of equal penetration layers,has been used to validate the proposed apparent resistivity functions.For this purpose,several ... Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee, UA 247 667, India.
Air-induced inverse Chladni patterns
van Gerner, H.J.; van der Weele, J.P.; van der Hoef, Martin Anton; van der Meer, Roger M.
2011-01-01
When very light particles are sprinkled on a resonating horizontal plate, inverse Chladni patterns are formed. Instead of going to the nodal lines of the plate, where they would form a standard Chladni pattern, the particles are dragged to the antinodes by the air currents induced by the vibration
Homogeneity of common cosmopolitan inversion frequencies in ...
Indian Academy of Sciences (India)
Unknown
2Present address: Population Genomics and Evolution Laboratory, Department of Biology,. Poornaprajna Institute of Scientific Research, ... climatic variables, suggesting that natural selection is operating on inversions (Krimbas and .... ses of other genetic markers (preferably at the molecular level). However, although our ...
Rapid probabilistic source inversion using pattern recognition
Käufl, Paul J.
2015-01-01
Numerous problems in the field of seismology require the determination of parameters of a physical model that are compatible with a set of observations and prior assumptions. This type of problem is generally termed inverse problem. While, in many cases, we are able to predict observations, given a
Inversion of e-simple Block Matrices
Czech Academy of Sciences Publication Activity Database
Fiedler, Miroslav
2005-01-01
Roč. 400, - (2005), s. 231-241 ISSN 0024-3795 R&D Projects: GA AV ČR IAA1030302 Institutional research plan: CEZ:AV0Z10300504 Keywords : matrix inversion * M-matrix * unipathic graph * e-simple graph Subject RIV: BA - General Mathematics Impact factor: 0.590, year: 2005
Frnakenstein: multiple target inverse RNA folding
Directory of Open Access Journals (Sweden)
Lyngsø Rune B
2012-10-01
Full Text Available Abstract Background RNA secondary structure prediction, or folding, is a classic problem in bioinformatics: given a sequence of nucleotides, the aim is to predict the base pairs formed in its three dimensional conformation. The inverse problem of designing a sequence folding into a particular target structure has only more recently received notable interest. With a growing appreciation and understanding of the functional and structural properties of RNA motifs, and a growing interest in utilising biomolecules in nano-scale designs, the interest in the inverse RNA folding problem is bound to increase. However, whereas the RNA folding problem from an algorithmic viewpoint has an elegant and efficient solution, the inverse RNA folding problem appears to be hard. Results In this paper we present a genetic algorithm approach to solve the inverse folding problem. The main aims of the development was to address the hitherto mostly ignored extension of solving the inverse folding problem, the multi-target inverse folding problem, while simultaneously designing a method with superior performance when measured on the quality of designed sequences. The genetic algorithm has been implemented as a Python program called Frnakenstein. It was benchmarked against four existing methods and several data sets totalling 769 real and predicted single structure targets, and on 292 two structure targets. It performed as well as or better at finding sequences which folded in silico into the target structure than all existing methods, without the heavy bias towards CG base pairs that was observed for all other top performing methods. On the two structure targets it also performed well, generating a perfect design for about 80% of the targets. Conclusions Our method illustrates that successful designs for the inverse RNA folding problem does not necessarily have to rely on heavy biases in base pair and unpaired base distributions. The design problem seems to become more
Dynamic Inversion of Intraslab Intermediate Depth Earthquakes
Madariaga, R. I.; Ruiz, S.
2011-12-01
We perform kinematic and dynamic inversions of the 24 July 2008 (Mw=6.8) Iwate northern Japan and 16 December 2007 (Mw 6.8) Michilla, Chile earthquakes using near field strong motion digital data. The data were filtered between 0.02 - 1 Hz. The rupture process is simulated with elliptical patches because we are looking for the average properties of the seismic rupture. The direct dynamic simulation problem was solved by a combination of finite difference modeling on a 32 km3 grid with 200 m spacing, and propagation from source to recorders using the AXITRA spectral program. For both earthquakes we used layered models of the structure. The Neighborhood algorithm and Monte Carlo methods are used to obtain the best fitting solutions and to explore the solution space. The optimum solutions are found comparing observed and synthetic records using an L2 norm. Both kinematic and dynamic inversions fit the observed data with misfits lower than 0.3. For both earthquakes, kinematic inversion shows strong trade-off between rupture velocity and maximum slip although the seismic moment remains invariant. Rupture velocities vary between sub-shear speeds to almost Rayleigh wave speeds. In the dynamic inversions 10 seismic source parameters were inverted for the Michilla earthquake and 8 parameters for the Iwate event, among them stress, friction and geometrical parameters. For the Iwate event the properties of the initial asperity at the source were not inverted because they could not be resolved by the data. In the dynamic inversion we observed a strong trade off among the friction law parameters. The best dynamic models form a family of that shares similar values of seismic moment and kappa (the ratio of released strain energy to energy release rate for friction). Kinematic and dynamic inversions in the 0.02 - 1 Hz frequency range form a set of non-unique solutions controlled by specific combinations of seismic source parameters. We discuss the origin of the non-uniqueness of
Coherent source imaging and dynamic support tracking for inverse scattering using compressive MUSIC
Lee, Okkyun; Kim, Jong Min; Yoo, Jaejoon; Jin, Kyunghwan; Ye, Jong Chul
2011-09-01
The goal of this paper is to develop novel algorithms for inverse scattering problems such as EEG/MEG, microwave imaging, and/or diffuse optical tomograpahy, and etc. One of the main contributions of this paper is a class of novel non-iterative exact nonlinear inverse scattering theory for coherent source imaging and moving targets. Specifically, the new algorithms guarantee the exact recovery under a very relaxed constraint on the number of source and receivers, under which the conventional methods fail. Such breakthrough was possible thanks to the recent theory of compressive MUSIC and its extension using support correction criterion, where partial support are estimated using the conventional compressed sensing approaches, then the remaining supports are estimated using a novel generalized MUSIC criterion. Numerical results using coherent sources in EEG/MEG and dynamic targets confirm that the new algorithms outperform the conventional ones.
Dependence of paracentric inversion rate on tract length
DEFF Research Database (Denmark)
York, Thomas L; Durrett, Rick; Nielsen, Rasmus
2007-01-01
BACKGROUND: We develop a Bayesian method based on MCMC for estimating the relative rates of pericentric and paracentric inversions from marker data from two species. The method also allows estimation of the distribution of inversion tract lengths. RESULTS: We apply the method to data from...... Drosophila melanogaster and D. yakuba. We find that pericentric inversions occur at a much lower rate compared to paracentric inversions. The average paracentric inversion tract length is approx. 4.8 Mb with small inversions being more frequent than large inversions.If the two breakpoints defining...... a paracentric inversion tract are uniformly and independently distributed over chromosome arms there will be more short tract-length inversions than long; we find an even greater preponderance of short tract lengths than this would predict. Thus there appears to be a correlation between the positions...
Energy Technology Data Exchange (ETDEWEB)
Nikolitsa Merminga
2007-06-01
The success and continuing progress of the three operating FELs based on Energy Recovery Linacs (ERLs), the Jefferson Lab IR FEL Upgrade, the Japan Atomic Energy Agency (JAEA) FEL, and the Novosibirsk High Power THz FEL, have inspired multiple future applications of ERLs, which include higher power FELs, synchrotron radiation sources, electron cooling devices, and high luminosity electron-ion colliders. The benefits of using ERLs for these applications are presented. The key accelerator physics and technology challenges of realizing future ERL designs, and recent developments towards resolving these challenges are reviewed.
Verser, Dan W.; Eggeman, Timothy J.
2009-10-13
A method is disclosed for the recovery of an organic acid from a dilute salt solution in which the cation of the salt forms an insoluble carbonate salt. A tertiary amine and CO.sub.2 are introduced to the solution to form the insoluble carbonate salt and a complex between the acid and an amine. A water immiscible solvent, such as an alcohol, is added to extract the acid/amine complex from the dilute salt solution to a reaction phase. The reaction phase is continuously dried and a product between the acid and the solvent, such as an ester, is formed.
Pyrochemical recovery of actinides
International Nuclear Information System (INIS)
Laidler, J.J.
1993-01-01
This report discusses an important advantage of the Integral Fast Reactor (IFR) which is its ability to recycle fuel in the process of power generation, extending fuel resources by a considerable amount and assuring the continued viability of nuclear power stations by reducing dependence on external fuel supplies. Pyroprocessing is the means whereby the recycle process is accomplished. It can also be applied to the recovery of fuel constituents from spent fuel generated in the process of operation of conventional light water reactor power plants, offering the means to recover the valuable fuel resources remaining in that material
Verser, Dan W [Menlo Park, CA; Eggeman, Timothy J [Lakewood, CO
2011-11-01
A method is disclosed for the recovery of an organic acid from a dilute salt solution in which the cation of the salt forms an insoluble carbonate salt. A tertiary amine and CO.sub.2 are introduced to the solution to form the insoluble carbonate salt and a complex between the acid and an amine. A water immiscible solvent, such as an alcohol, is added to extract the acid/amine complex from the dilute salt solution to a reaction phase. The reaction phase is continuously dried and a product between the acid and the solvent, such as an ester, is formed.
International Nuclear Information System (INIS)
Phi Wah Tooi
2010-01-01
Full text: The Konzen in-house designed anaerobic digester system for the POME (Palm Oil Mill Effluent) treatment process is one of the registered Clean Development Mechanism (CDM) projects in Malaysia. It is an organic wastewater treatment process which achieves excellent co-benefits objectives through the prevention of water pollution and reduction of greenhouse gas emissions, which is estimated to be 40,000 to 50,000 t-CO 2 per year. The anaerobic digester was designed in mesophile mode with temperature ranging from 37 degree Celsius to 45 degree Celsius. A microorganisms growth is optimum under moderately warm temperature conditions. The operating temperature of the anaerobic digester needs to be maintained constantly. There are two waste heat recovery systems designed to make the treatment process self-sustaining. The heat recovered will be utilised as a clean energy source to heat up the anaerobic digester indirectly. The first design for the waste heat recovery system utilises heat generated from the flue gas of the biogas flaring system. A stainless steel water tank with an internal water layer is installed at the top level of the flare stack. The circulating water is heated by the methane enriched biogas combustion process. The second design utilizes heat generated during the compression process for the biogas compressor operation. The compressed biogas needs to be cooled before being recycled back into the digester tank for mixing purposes. Both the waste heat recovery systems use a design which applies a common water circulation loop and hot water tank to effectively become a closed loop. The hot water tank will perform both storage and temperature buffer functions. The hot water is then used to heat up recycled sludge from 30 degree Celsius to 45 degree Celsius with the maximum temperature setting at 50 degree Celsius. The recycled sludge line temperature will be measured and monitored by a temperature sensor and transmitter, which will activate the
Pyrolysis with staged recovery
Green, Norman W.; Duraiswamy, Kandaswamy; Lumpkin, Robert E.; Winter, Bruce L.
1979-03-20
In a continuous process for recovery of values contained in a solid carbonaceous material, the carbonaceous material is comminuted and then subjected to flash pyrolysis in the presence of a particulate heat source fed over an overflow weir to form a pyrolysis product stream containing a carbon containing solid residue and volatilized hydrocarbons. After the carbon containing solid residue is separated from the pyrolysis product stream, values are obtained by condensing volatilized hydrocarbons. The particulate source of heat is formed by oxidizing carbon in the solid residue.
SISYPHUS: A high performance seismic inversion factory
Gokhberg, Alexey; Simutė, Saulė; Boehm, Christian; Fichtner, Andreas
2016-04-01
In the recent years the massively parallel high performance computers became the standard instruments for solving the forward and inverse problems in seismology. The respective software packages dedicated to forward and inverse waveform modelling specially designed for such computers (SPECFEM3D, SES3D) became mature and widely available. These packages achieve significant computational performance and provide researchers with an opportunity to solve problems of bigger size at higher resolution within a shorter time. However, a typical seismic inversion process contains various activities that are beyond the common solver functionality. They include management of information on seismic events and stations, 3D models, observed and synthetic seismograms, pre-processing of the observed signals, computation of misfits and adjoint sources, minimization of misfits, and process workflow management. These activities are time consuming, seldom sufficiently automated, and therefore represent a bottleneck that can substantially offset performance benefits provided by even the most powerful modern supercomputers. Furthermore, a typical system architecture of modern supercomputing platforms is oriented towards the maximum computational performance and provides limited standard facilities for automation of the supporting activities. We present a prototype solution that automates all aspects of the seismic inversion process and is tuned for the modern massively parallel high performance computing systems. We address several major aspects of the solution architecture, which include (1) design of an inversion state database for tracing all relevant aspects of the entire solution process, (2) design of an extensible workflow management framework, (3) integration with wave propagation solvers, (4) integration with optimization packages, (5) computation of misfits and adjoint sources, and (6) process monitoring. The inversion state database represents a hierarchical structure with
Spheroidal Integral Equations for Geodetic Inversion of Geopotential Gradients
Novák, Pavel; Šprlák, Michal
2017-12-01
The static Earth's gravitational field has traditionally been described in geodesy and geophysics by the gravitational potential (geopotential for short), a scalar function of 3-D position. Although not directly observable, geopotential functionals such as its first- and second-order gradients are routinely measured by ground, airborne and/or satellite sensors. In geodesy, these observables are often used for recovery of the static geopotential at some simple reference surface approximating the actual Earth's surface. A generalized mathematical model is represented by a surface integral equation which originates in solving Dirichlet's boundary-value problem of the potential theory defined for the harmonic geopotential, spheroidal boundary and globally distributed gradient data. The mathematical model can be used for combining various geopotential gradients without necessity of their re-sampling or prior continuation in space. The model extends the apparatus of integral equations which results from solving boundary-value problems of the potential theory to all geopotential gradients observed by current ground, airborne and satellite sensors. Differences between spherical and spheroidal formulations of integral kernel functions of Green's kind are investigated. Estimated differences reach relative values at the level of 3% which demonstrates the significance of spheroidal approximation for flattened bodies such as the Earth. The observation model can be used for combined inversion of currently available geopotential gradients while exploring their spectral and stochastic characteristics. The model would be even more relevant to gravitational field modelling of other bodies in space with more pronounced spheroidal geometry than that of the Earth.
Spheroidal Integral Equations for Geodetic Inversion of Geopotential Gradients
Novák, Pavel; Šprlák, Michal
2018-03-01
The static Earth's gravitational field has traditionally been described in geodesy and geophysics by the gravitational potential (geopotential for short), a scalar function of 3-D position. Although not directly observable, geopotential functionals such as its first- and second-order gradients are routinely measured by ground, airborne and/or satellite sensors. In geodesy, these observables are often used for recovery of the static geopotential at some simple reference surface approximating the actual Earth's surface. A generalized mathematical model is represented by a surface integral equation which originates in solving Dirichlet's boundary-value problem of the potential theory defined for the harmonic geopotential, spheroidal boundary and globally distributed gradient data. The mathematical model can be used for combining various geopotential gradients without necessity of their re-sampling or prior continuation in space. The model extends the apparatus of integral equations which results from solving boundary-value problems of the potential theory to all geopotential gradients observed by current ground, airborne and satellite sensors. Differences between spherical and spheroidal formulations of integral kernel functions of Green's kind are investigated. Estimated differences reach relative values at the level of 3% which demonstrates the significance of spheroidal approximation for flattened bodies such as the Earth. The observation model can be used for combined inversion of currently available geopotential gradients while exploring their spectral and stochastic characteristics. The model would be even more relevant to gravitational field modelling of other bodies in space with more pronounced spheroidal geometry than that of the Earth.
Energy Technology Data Exchange (ETDEWEB)
Agullo, Y.
2005-09-15
This thesis present the extension of mono-component seismic pre-stack data stratigraphical inversion method to multicomponent data, with the objective of improving the determination of reservoir elastic parameters. In addiction to the PP pressure waves, the PS converted waves proved their interest for imaging under gas clouds; and their potential is highly significant for the characterization of lithologies, fluids, fractures... Nevertheless the simultaneous use ol PP and PS data remains problematic because of their different the time scales. To jointly use the information contained in PP and PS data, we propose a method in three steps first, mono-component stratigraphic inversions of PP then PS data; second, estimation of the PP to PS time conversion law; third, multicomponent stratigraphic inversion. For the second point, the estimation of the PP to PS conversion law is based on minimizing the difference between the S impedances obtained from PP and PS mono-component stratigraphic inversion. The pre-stack mono-component stratigraphic inversions was adapted to the case of multicomponent data by leaving each type of data in its own time scale in order to avoid the distortion of the seismic wavelet. The results obtained on a realistic synthetic PP-PS case show on one hand that determining PP to PS conversion law (from the mono-component inversion results) is feasible, and on the other hand that the joint inversion of PP and PS data with this conversion law improves the results compared to the mono-component inversion ones. Although this is presented within the framework of the PP and PS multi-component data, the developed methodology adapts directly to PP and SS data for example. (author)
Heriyanto, Mohammad; Srigutomo, Wahyu
2017-01-01
Exploration of natural or energy resources requires geophysical survey to determine the subsurface structure, such as DC resistivity method. In this research, field and synthetic data were used using Schlumberger configuration. One-dimensional (1-D) DC resistivity inversion was carried out using Singular Value Decomposition (SVD) and Levenberg-Marquardt (LM) techniques to obtain layered resistivity structure. We have developed software to perform both inversion met...
Energy Technology Data Exchange (ETDEWEB)
Lisin, E. A.; Lisina, I. I.; Vaulina, O. S.; Petrov, O. F. [Joint Institute for High Temperatures of the Russian Academy of Sciences, 13 bd.2 Izhorskaya St., Moscow 125412, Russia and Moscow Institute of Physics and Technology, 9 Institutskiy Per., Dolgoprudny, Moscow Region 141700 (Russian Federation)
2015-03-15
Solution of the inverse Langevin problem is presented for open dissipative systems with anisotropic interparticle interaction. Possibility of applying this solution for experimental determining the anisotropic interaction forces between dust particles in complex plasmas with ion flow is considered. For this purpose, we have tested the method on the results of numerical simulation of chain structures of particles with quasidipole-dipole interaction, similar to the one occurring due to effects of ion focusing in gas discharges. Influence of charge spatial inhomogeneity and fluctuations on the results of recovery is also discussed.
On the calibration process of film dosimetry: OLS inverse regression versus WLS inverse prediction
International Nuclear Information System (INIS)
Crop, F; Thierens, H; Rompaye, B Van; Paelinck, L; Vakaet, L; Wagter, C De
2008-01-01
The purpose of this study was both putting forward a statistically correct model for film calibration and the optimization of this process. A reliable calibration is needed in order to perform accurate reference dosimetry with radiographic (Gafchromic) film. Sometimes, an ordinary least squares simple linear (in the parameters) regression is applied to the dose-optical-density (OD) curve with the dose as a function of OD (inverse regression) or sometimes OD as a function of dose (inverse prediction). The application of a simple linear regression fit is an invalid method because heteroscedasticity of the data is not taken into account. This could lead to erroneous results originating from the calibration process itself and thus to a lower accuracy. In this work, we compare the ordinary least squares (OLS) inverse regression method with the correct weighted least squares (WLS) inverse prediction method to create calibration curves. We found that the OLS inverse regression method could lead to a prediction bias of up to 7.3 cGy at 300 cGy and total prediction errors of 3% or more for Gafchromic EBT film. Application of the WLS inverse prediction method resulted in a maximum prediction bias of 1.4 cGy and total prediction errors below 2% in a 0-400 cGy range. We developed a Monte-Carlo-based process to optimize calibrations, depending on the needs of the experiment. This type of thorough analysis can lead to a higher accuracy for film dosimetry
Facies Constrained Elastic Full Waveform Inversion
Zhang, Z.
2017-05-26
Current efforts to utilize full waveform inversion (FWI) as a tool beyond acoustic imaging applications, for example for reservoir analysis, face inherent limitations on resolution and also on the potential trade-off between elastic model parameters. Adding rock physics constraints does help to mitigate these issues. However, current approaches to add such constraints are based on averaged type rock physics regularization terms. Since the true earth model consists of different facies, averaging over those facies naturally leads to smoothed models. To overcome this, we propose a novel way to utilize facies based constraints in elastic FWI. A so-called confidence map is calculated and updated at each iteration of the inversion using both the inverted models and the prior information. The numerical example shows that the proposed method can reduce the cross-talks and also can improve the resolution of inverted elastic properties.
Application of inversions to lossless image compression
Arnavut, Ziya
1997-04-01
Linear prediction schemes, such as that of the Joint Photographic Experts Group (JPEG), are simple and normally produces a residual sequence with lower zero-order entry. Occasionally the entropy of the prediction error becomes greater than that of the original image. Such situations frequently occur when the image data have discrete gray levels located within certain intervals. To alleviate this problem, various authors have suggested different preprocessing methods. However, the techniques reported require two passes. We extend the definition of Lehmer-type inversions (Lehmer 1950 and 1964) from permutations to multiset permutations and present a one-pass algorithm based on inversions of a multiset permutation. We obtain comparable results when we apply JPEG and even better results when we apply some other linear prediction schemes on a preprocessed image, which is treated as multiset permutation.
Optical inverse-square displacement sensor
Howe, R.D.; Kychakoff, G.
1989-09-12
This invention comprises an optical displacement sensor that uses the inverse-square attenuation of light reflected from a diffused surface to calculate the distance from the sensor to the reflecting surface. Light emerging from an optical fiber or the like is directed onto the surface whose distance is to be measured. The intensity I of reflected light is angle dependent, but within a sufficiently small solid angle it falls off as the inverse square of the distance from the surface. At least a pair of optical detectors are mounted to detect the reflected light within the small solid angle, their ends being at different distances R and R + [Delta]R from the surface. The distance R can then be found in terms of the ratio of the intensity measurements and the separation length as given in an equation. 10 figs.
Function representation with circle inversion map systems
Boreland, Bryson; Kunze, Herb
2017-01-01
The fractals literature develops the now well-known concept of local iterated function systems (using affine maps) with grey-level maps (LIFSM) as an approach to function representation in terms of the associated fixed point of the so-called fractal transform. While originally explored as a method to achieve signal (and 2-D image) compression, more recent work has explored various aspects of signal and image processing using this machinery. In this paper, we develop a similar framework for function representation using circle inversion map systems. Given a circle C with centre õ and radius r, inversion with respect to C transforms the point p˜ to the point p˜', such that p˜ and p˜' lie on the same radial half-line from õ and d(õ, p˜)d(õ, p˜') = r2, where d is Euclidean distance. We demonstrate the results with an example.
Voxel inversion of airborne EM data
DEFF Research Database (Denmark)
Fiandaca, Gianluca G.; Auken, Esben; Christiansen, Anders Vest C A.V.C.
2013-01-01
of prior information. Inversion of geophysical data usually refers to a model space being linked to the actual observation points. For airborne surveys the spatial discretization of the model space reflects the flight lines. Often airborne surveys are carried out in areas where other ground-based...... geophysical data are available. The model space of geophysical inversions is usually referred to the positions of the measurements, and ground-based model positions do not generally coincide with the airborne model positions. Consequently, a model space based on the measuring points is not well suited...... for jointly inverting airborne and ground-based geophysical data. Furthermore, geological and groundwater models most often refer to a regular voxel grid not correlated to the geophysical model space, and incorporating the geophysical data into the geological/hydrological modelling grids is problematic. We...
Inverse Faraday effect with plasmon beams
International Nuclear Information System (INIS)
Ali, S; Mendonca, J T
2011-01-01
The angular momentum conservation equation is considered for an electron gas, in the presence of Laguerre-Gaussian (LG) plasmons propagating along the z-axis. The LG plasmons carry a finite orbital angular momentum despite longitudinal nature, which can be partly transfered to the electrons. For short timescales, such that ion motion can be neglected, plasmons primarily interact with the electrons, creating an azimuthal electric field and generating an axial magnetic field. This effect can be called an inverse Faraday effect due to plasmons. Numerically, it is found that the magnitude of the magnetic field enhances with the plasmon density or with the energy of the electron plasma waves. A comparison of the magnitudes of the axial magnetic field is made for the inverse Faraday effect excited by both plasmons and transverse photons.
Inverse Kinematics of Concentric Tube Steerable Needles.
Sears, Patrick; Dupont, Pierre E
2007-01-01
Prior papers have introduced steerable needles composed of precurved concentric tubes. The curvature and extent of these needles can be controlled by the relative rotation and translation of the individual tubes. Under certain assumptions on the geometry and design of these needles, the forward kinematics problem can be solved in closed form by means of algebraic equations. The inverse kinematics problem, however, is not as straightforward owing to the nonlinear map between relative tube displacements and needle tip configuration as well as to the multiplicity of solutions as the number of tubes increases. This paper presents a general approach to solving the inverse kinematics problem using a pseudoinverse solution together with gradients of nullspace potential functions to enforce geometric and mechanical constraints.
Analog fault diagnosis by inverse problem technique
Ahmed, Rania F.
2011-12-01
A novel algorithm for detecting soft faults in linear analog circuits based on the inverse problem concept is proposed. The proposed approach utilizes optimization techniques with the aid of sensitivity analysis. The main contribution of this work is to apply the inverse problem technique to estimate the actual parameter values of the tested circuit and so, to detect and diagnose single fault in analog circuits. The validation of the algorithm is illustrated through applying it to Sallen-Key second order band pass filter and the results show that the detecting percentage efficiency was 100% and also, the maximum error percentage of estimating the parameter values is 0.7%. This technique can be applied to any other linear circuit and it also can be extended to be applied to non-linear circuits. © 2011 IEEE.
Radon concentration inversions in the troposphere
International Nuclear Information System (INIS)
Pereira, E.B.
1987-07-01
Vertical concentrations of radon in the lower troposphere were obtained in Southern Brazil up to 7Km high and have shown unexpected inverted profiles. The presence of low pressure center systems southwest to the flight path suggested that inversions might have been originated by a vertical transport mechanism based on the large scale circulation of developing synoptic systems. A simple friction-driven circulation model was contructed and the transport equation was solved. (author) [pt
Inverse folding of RNA pseudoknot structures
Directory of Open Access Journals (Sweden)
Li Linda YM
2010-06-01
Full Text Available Abstract Background RNA exhibits a variety of structural configurations. Here we consider a structure to be tantamount to the noncrossing Watson-Crick and G-U-base pairings (secondary structure and additional cross-serial base pairs. These interactions are called pseudoknots and are observed across the whole spectrum of RNA functionalities. In the context of studying natural RNA structures, searching for new ribozymes and designing artificial RNA, it is of interest to find RNA sequences folding into a specific structure and to analyze their induced neutral networks. Since the established inverse folding algorithms, RNAinverse, RNA-SSD as well as INFO-RNA are limited to RNA secondary structures, we present in this paper the inverse folding algorithm Inv which can deal with 3-noncrossing, canonical pseudoknot structures. Results In this paper we present the inverse folding algorithm Inv. We give a detailed analysis of Inv, including pseudocodes. We show that Inv allows to design in particular 3-noncrossing nonplanar RNA pseudoknot 3-noncrossing RNA structures-a class which is difficult to construct via dynamic programming routines. Inv is freely available at http://www.combinatorics.cn/cbpc/inv.html. Conclusions The algorithm Inv extends inverse folding capabilities to RNA pseudoknot structures. In comparison with RNAinverse it uses new ideas, for instance by considering sets of competing structures. As a result, Inv is not only able to find novel sequences even for RNA secondary structures, it does so in the context of competing structures that potentially exhibit cross-serial interactions.
The solution of nitrogen inversion in amidases.
Syrén, Per-Olof
2013-07-01
An important mechanistic aspect of enzyme catalyzed amide bond hydrolysis is the specific orientation of the lone pair of the nitrogen of the scissile amide bond during catalysis. As discussed in the literature during the last decades, stereoelectronic effects cause the single lone pair in the formed tetrahedral intermediate to be situated in a non-productive conformation in the enzyme active site and hence nitrogen inversion or rotation is necessary. By discussing recent mechanistic findings in the literature relevant for the conformation of the lone pair of the reacting amide nitrogen atom, it will be demonstrated that nature has evolved at least two catalytic strategies to cope with the stereoelectronic constraints inherent to amide bond hydrolysis regardless of the fold or catalytic mechanism. One solution to the inversion problem is to stabilize the transition state of inversion by hydrogen bond formation; another is to introduce a concerted proton shuttle mechanism that avoids inversion and delivers a hydrogen to the lone pair. By using molecular modeling it is demonstrated that the H-bond strategy is general and can be expanded to include many amidases/proteases with important metabolic functions, including the proteasome. Some examples of the proton shuttle mechanism will also be mentioned. To complete the picture of efficient enzyme catalyzed amide bond hydrolysis, general interactions in the active site of these catalysts will be discussed. An expanded knowledge of the prerequisites of efficient amide bond hydrolysis beyond the oxyanion hole and the catalytic dyad/triad will be of importance for enzyme and drug design. © 2013 The Author Journal compilation © 2013 FEBS.
Approximate Inverse Preconditioners with Adaptive Dropping
Czech Academy of Sciences Publication Activity Database
Kopal, J.; Rozložník, Miroslav; Tůma, Miroslav
2015-01-01
Roč. 84, June (2015), s. 13-20 ISSN 0965-9978 R&D Projects: GA ČR(CZ) GAP108/11/0853; GA ČR GA13-06684S Institutional support: RVO:67985807 Keywords : approximate inverse * Gram-Schmidt orthogonalization * incomplete decomposition * preconditioned conjugate gradient method * algebraic preconditioning * pivoting Subject RIV: BA - General Mathematics Impact factor: 1.673, year: 2015
Robust inversion via semistochastic dimensionality reduction
Aravkin, Aleksandr; Friedlander, Michael P.; van Leeuwen, Tristan
2011-01-01
We consider a class of inverse problems where it is possible to aggregate the results of multiple experiments. This class includes problems where the forward model is the solution operator to linear ODEs or PDEs. The tremendous size of such problems motivates dimensionality reduction techniques based on randomly mixing experiments. These techniques break down, however, when robust data-fitting formulations are used, which are essential in cases of missing data, unusually large errors, and sys...
Elastic versus acoustic inversion for marine surveys
Mora, Peter
2018-04-24
Full Wavefield Inversion (FWI) is a powerful and elegant approach for seismic imaging that is on the way to becoming the method of choice when processing exploration or global seismic data. In the case of processing marine survey data, one may be tempted to assume acoustic FWI is sufficient given that only pressure waves exist in the water layer. In this paper, we pose the question as to whether or not in theory – at least for a hard water bottom case – it should be possible to resolve the shear modulus or S-wave velocity in a marine setting using large offset data. We therefore conduct numerical experiments with idealized marine data calculated with the elastic wave equation. We study two cases, FWI of data due to a diffractor model, and FWI of data due to a fault model. We find that at least in idealized situation, elastic FWI of hard waterbottom data is capable of resolving between the two Lamé parameters λ and μ. Another numerical experiment with a soft waterbottom layer gives the same result. In contrast, acoustic FWI of the synthetic elastic data results in a single image of the first Lamé parameter λ which contains severe artefacts for diffraction data and noticable artefacts for layer reflection data. Based on these results, it would appear that at least, inversions of large offset marine data should be fully elastic rather than acoustic unless it has been demonstrated that for the specific case in question (offsets, model and water depth, practical issues such as soft sediment attenuation of shear waves or computational time), that an acoustic only inversion provides a reasonably good quality of image comparable to that of an elastic inversion. Further research with real data is required to determine the degree to which practical issues such as shear wave attenuation in soft sediments may affect this result.
On some inverse problems in nuclear physics
Belashev, B. Z.; Suleymanov, M. K.
2001-01-01
Some inverse problems in high-energy physics, neutron diffraction and NMR spectroscopy are discussed. To solve them, the Fourier integrated transformation method and the Maximum Entropy Technique (MENT) were used. The integrated images of experimental distributions are shown to be informative when determining the space-time parameters of a particle generation zone and when analysing blurred spectra. The efficiency of the above methods was checked by comparing relevant results with the results...
Geoacoustic inversion using the vector field
Crocker, Steven E.
The main goal of this project was to study the use of the acoustic vector field, separately or in combination with the scalar field, to estimate the depth dependent geoacoustic properties of the seafloor via non-linear inversion. The study was performed in the context of the Sediment Acoustics Experiment 2004 (SAX04) conducted in the Northern Gulf of Mexico (GOM) where a small number of acoustic vector sensors were deployed in close proximity to the seafloor. A variety of acoustic waveforms were transmitted into the seafloor at normal incidence. The acoustic vector sensors were located both above and beneath the seafloor interface where they measured the acoustic pressure and the acoustic particle acceleration. Motion data provided by the buried vector sensors were affected by a suspension response that was sensitive to the mass properties of the sensor, the sediment density and sediment elasticity (e.g., shear wave speed). The suspension response for the buried vector sensors included a resonance within the analysis band of 0.4 to 2.0 kHz. The suspension resonance represented an unknown complex transfer function between the acoustic vector field in the seabed and data representing that field. Therefore, inverse methods developed for this study were required to 1) estimate dynamic properties of the sensor suspension resonance and 2) account for the associated corruption of vector field data. A method to account for the vector sensor suspense response function was integrated directly into the inversion methods such that vector channel data corruption was reduced and an estimate of the shear wave speed in the sediment was returned. Inversions of real and synthetic data sets indicated that information about sediment shear wave speed was carried by the suspension response of the buried sensors, as opposed to being contained inherently within the acoustic vector field.
Differential equations inverse and direct problems
Favini, Angelo
2006-01-01
DEGENERATE FIRST ORDER IDENTIFICATION PROBLEMS IN BANACH SPACES A NONISOTHERMAL DYNAMICAL GINZBURG-LANDAU MODEL OF SUPERCONDUCTIVITY. EXISTENCE AND UNIQUENESS THEOREMSSOME GLOBAL IN TIME RESULTS FOR INTEGRODIFFERENTIAL PARABOLIC INVERSE PROBLEMSFOURTH ORDER ORDINARY DIFFERENTIAL OPERATORS WITH GENERAL WENTZELL BOUNDARY CONDITIONSTUDY OF ELLIPTIC DIFFERENTIAL EQUATIONS IN UMD SPACESDEGENERATE INTEGRODIFFERENTIAL EQUATIONS OF PARABOLIC TYPE EXPONENTIAL ATTRACTORS FOR SEMICONDUCTOR EQUATIONSCONVERGENCE TO STATIONARY STATES OF SOLUTIONS TO THE SEMILINEAR EQUATION OF VISCOELASTICITY ASYMPTOTIC BEHA
Full-waveform inversion: Filling the gaps
Beydoun, Wafik B.
2015-09-01
After receiving an outstanding response to its inaugural workshop in 2013, SEG once again achieved great success with its 2015 SEG Middle East Workshop, “Full-waveform inversion: Filling the gaps,” which took place 30 March–1 April 2015 in Abu Dhabi, UAE. The workshop was organized by SEG, and its partner sponsors were Saudi Aramco (gold sponsor), ExxonMobil, and CGG. Read More: http://library.seg.org/doi/10.1190/tle34091106.1
Inverse Bremsstrahlung in Astrophysical Plasmas: The Absorption ...
Indian Academy of Sciences (India)
(λ, T ; Ne,Ni) = k q.c. i.b.. (λ, T ; Ne,Ni) · Gi.b.(λ, T ),. (2) where Gi.b.(λ, T ) is the sought Gaunt factor. The determination of such averaged. Gaunt factor as a function of λ and T was the object of investigation in majority of the previous papers devoted to the inverse Bremsstrahlung process. This is illustrated in Figure 1, where ...
Inverse Scattering in a Multipath Environment
Directory of Open Access Journals (Sweden)
A. Cuccaro
2016-09-01
Full Text Available In this contribution an inverse scattering problem is ad- dressed in a multipath environment. In particular, multipath is created by known ”extra” point-like scatterers (passive elements expressely deployed between the scene under in- vestigation and the source/measurement domains. Through a back-projection imaging scheme, the role of the passive elements on the achievable performance is shown and com- pared to the free-space case.
Classical geometry Euclidean, transformational, inversive, and projective
Leonard, I E; Liu, A C F; Tokarsky, G W
2014-01-01
Features the classical themes of geometry with plentiful applications in mathematics, education, engineering, and science Accessible and reader-friendly, Classical Geometry: Euclidean, Transformational, Inversive, and Projective introduces readers to a valuable discipline that is crucial to understanding bothspatial relationships and logical reasoning. Focusing on the development of geometric intuitionwhile avoiding the axiomatic method, a problem solving approach is encouraged throughout. The book is strategically divided into three sections: Part One focuses on Euclidean geometry, which p
Metric entropy in linear inverse scattering
Directory of Open Access Journals (Sweden)
M. A. Maisto
2016-09-01
Full Text Available The role of multiple views and/or multiple frequencies on the achievable performance in linear inverse scattering problems is addressed. To this end, the impact of views and frequencies on the Kolmogorov entropy measure is studied. This way the metric information that can be conveyed back from data to the unknown can be estimated. For the sake of simplicity, the study deals with strip scatterers and the cases of discrete angles of incidence and/or frequencies.
Bayesian Inversion of Seabed Scattering Data
2014-09-30
using global optimization and Markov-chain Monte Carlo ( MCMC ) sampling algorithms. One of the goals of this work is to carry out inversions trans...is based on formulating the posterior probability density (PPD) of the model parameters of interest, which combines both data and prior information... posterior parameter uncertainty distributions, which quantify the effective data information content. In particular, scattering/geoacoustic parameter
Factorized Approximate Inverses With Adaptive Dropping
Czech Academy of Sciences Publication Activity Database
Kopal, Jiří; Rozložník, Miroslav; Tůma, Miroslav
2016-01-01
Roč. 38, č. 3 (2016), A1807-A1820 ISSN 1064-8275 R&D Projects: GA ČR GA13-06684S Grant - others:GA MŠk(CZ) LL1202 Institutional support: RVO:67985807 Keywords : approximate inverses * incomplete factorization * Gram–Schmidt orthogonalization * preconditioned iterative methods Subject RIV: BA - General Mathematics Impact factor: 2.195, year: 2016
An inverse approach for elucidating dendritic function
Directory of Open Access Journals (Sweden)
Benjamin Torben-Nielsen
2010-09-01
Full Text Available We outline an inverse approach for investigating dendritic function-structure relationships by optimizing dendritic trees for a-priori chosen computational functions. The inverse approach can be applied in two different ways. First, we can use it as a `hypothesis generator' in which we optimize dendrites for a function of general interest. The optimization yields an artificial dendrite that is subsequently compared to real neurons. This comparison potentially allows us to propose hypotheses about the function of real neurons. In this way, we investigated dendrites that optimally perform input-order detection. Second, we can use it as a `function confirmation' by optimizing dendrites for functions hypothesized to be performed by classes of neurons. If the optimized, artificial, dendrites resemble the dendrites of real neurons the artificial dendrites corroborate the hypothesized function of the real neuron. Moreover, properties of the artificial dendrites can lead to predictions about yet unmeasured properties. In this way, we investigated wide-field motion integration performed by the VS cells of the fly visual system. In outlining the inverse approach and two applications, we also elaborate on the nature of dendritic function. We furthermore discuss the role of optimality in assigning functions to dendrites and point out interesting future directions.
Silicon MIS/inversion-layer solar cells
Olsen, L. C.
1982-10-01
Silicon Metal-Insulator-Semiconductor/Inversion-Layer (MIS-IL) solar cells were investigated as an approach to low cost terrestrial photovoltaics. Considerable progress was made concerning the development of procedures for SiO deposition for inversion-layer formation, the characterization of the fixed charge in deposited SiO layers, surface state density at the Si-SiO interface, fabrication and characterization of MIS-IL solar cells. Improvements were also made in the theory of MIS-IL solar cells, and utilized to calculate cell performance for a range of insulator charge and base resistivities. Inversion layer formation was studied in several ways. MOS devices was analyzed to determine the magnitude of the net positive charge, Q/sub POS/, vensus surface potential, Psi/sub S/. In situ sheet resistance measurements was made to determine the charge distribution within the deposited SiO layer. Finally, estimates of Q/sub POS/ obtained by comparing experimental results for MIS-IL cells and theory are compared with values of Q/sub POS/ determined for MOS structures fabricated simultaneously with the solar cells. Cell fabrication procedures emphasized low temperature processing.
Solar structure inversion with LOWL data
Basu, Sarbani; Christensen-Dalsgaard, Joergen; Schou, Jesper; Thompson, Michael J.; Tomczyk, Steven
1995-01-01
Inversion results for the radial hydrostatic structure of the Sun, using six months of oscillation data obtained with the LOWL instrument, are presented. Both low and intermediate degree modes are used, thus avoiding the systematic errors that might have occurred in previous inversions by merging more than one data set. Using modes of between 0 deg and 90 deg and frequencies of between 1.5 mHz and 3.5 mHz, the variations with depth of the speed of sound, the density and the pressure were inferred for radii of between 0.05 and 0.85 stellar radius. It was found that in this region, the sound speed was within 0.15% of that of a model constructed using an equation of state that incorporated helium diffusion. The density difference between the Sun and the model was less than 0.8%. Given the small error bars on the inversion results, these differences are considered as being significant.
TOPICAL REVIEW: Inverse problems in elasticity
Bonnet, Marc; Constantinescu, Andrei
2005-04-01
This review is devoted to some inverse problems arising in the context of linear elasticity, namely the identification of distributions of elastic moduli, model parameters or buried objects such as cracks. These inverse problems are considered mainly for three-dimensional elastic media under equilibrium or dynamical conditions, and also for thin elastic plates. The main goal is to overview some recent results, in an effort to bridge the gap between studies of a mathematical nature and problems defined from engineering practice. Accordingly, emphasis is given to formulations and solution techniques which are well suited to general-purpose numerical methods for solving elasticity problems on complex configurations, in particular the finite element method and the boundary element method. An underlying thread of the discussion is the fact that useful tools for the formulation, analysis and solution of inverse problems arising in linear elasticity, namely the reciprocity gap and the error in constitutive equation, stem from variational and virtual work principles, i.e., fundamental principles governing the mechanics of deformable solid continua. In addition, the virtual work principle is shown to be instrumental for establishing computationally efficient formulae for parameter or geometrical sensitivity, based on the adjoint solution method. Sensitivity formulae are presented for various situations, especially in connection with contact mechanics, cavity and crack shape perturbations, thus enriching the already extensive known repertoire of such results. Finally, the concept of topological derivative and its implementation for the identification of cavities or inclusions are expounded.
Are Pericentric Inversions Reorganizing Wedge Shell Genomes?
Directory of Open Access Journals (Sweden)
Daniel García-Souto
2017-12-01
Full Text Available Wedge shells belonging to the Donacidae family are the dominant bivalves in exposed beaches in almost all areas of the world. Typically, two or more sympatric species of wedge shells differentially occupy intertidal, sublittoral, and offshore coastal waters in any given locality. A molecular cytogenetic analysis of two sympatric and closely related wedge shell species, Donax trunculus and Donax vittatus, was performed. Results showed that the karyotypes of these two species were both strikingly different and closely alike; whilst metacentric and submetacentric chromosome pairs were the main components of the karyotype of D. trunculus, 10–11 of the 19 chromosome pairs were telocentric in D. vittatus, most likely as a result of different pericentric inversions. GC-rich heterochromatic bands were present in both species. Furthermore, they showed coincidental 45S ribosomal RNA (rRNA, 5S rRNA and H3 histone gene clusters at conserved chromosomal locations, although D. trunculus had an additional 45S rDNA cluster. Intraspecific pericentric inversions were also detected in both D. trunculus and D. vittatus. The close genetic similarity of these two species together with the high degree of conservation of the 45S rRNA, 5S rRNA and H3 histone gene clusters, and GC-rich heterochromatic bands indicate that pericentric inversions contribute to the karyotype divergence in wedge shells.
Elastic reflection waveform inversion with variable density
Li, Yuanyuan
2017-08-17
Elastic full waveform inversion (FWI) provides a better description of the subsurface than those given by the acoustic assumption. However it suffers from a more serious cycle skipping problem compared with the latter. Reflection waveform inversion (RWI) provides a method to build a good background model, which can serve as an initial model for elastic FWI. Therefore, we introduce the concept of RWI for elastic media, and propose elastic RWI with variable density. We apply Born modeling to generate the synthetic reflection data by using optimized perturbations of P- and S-wave velocities and density. The inversion for the perturbations in P- and S-wave velocities and density is similar to elastic least-squares reverse time migration (LSRTM). An incorrect initial model will lead to some misfits at the far offsets of reflections; thus, can be utilized to update the background velocity. We optimize the perturbation and background models in a nested approach. Numerical tests on the Marmousi model demonstrate that our method is able to build reasonably good background models for elastic FWI with absence of low frequencies, and it can deal with the variable density, which is needed in real cases.
Computationally efficient Bayesian inference for inverse problems.
Energy Technology Data Exchange (ETDEWEB)
Marzouk, Youssef M.; Najm, Habib N.; Rahn, Larry A.
2007-10-01
Bayesian statistics provides a foundation for inference from noisy and incomplete data, a natural mechanism for regularization in the form of prior information, and a quantitative assessment of uncertainty in the inferred results. Inverse problems - representing indirect estimation of model parameters, inputs, or structural components - can be fruitfully cast in this framework. Complex and computationally intensive forward models arising in physical applications, however, can render a Bayesian approach prohibitive. This difficulty is compounded by high-dimensional model spaces, as when the unknown is a spatiotemporal field. We present new algorithmic developments for Bayesian inference in this context, showing strong connections with the forward propagation of uncertainty. In particular, we introduce a stochastic spectral formulation that dramatically accelerates the Bayesian solution of inverse problems via rapid evaluation of a surrogate posterior. We also explore dimensionality reduction for the inference of spatiotemporal fields, using truncated spectral representations of Gaussian process priors. These new approaches are demonstrated on scalar transport problems arising in contaminant source inversion and in the inference of inhomogeneous material or transport properties. We also present a Bayesian framework for parameter estimation in stochastic models, where intrinsic stochasticity may be intermingled with observational noise. Evaluation of a likelihood function may not be analytically tractable in these cases, and thus several alternative Markov chain Monte Carlo (MCMC) schemes, operating on the product space of the observations and the parameters, are introduced.
Constraining inverse curvature gravity with supernovae
Energy Technology Data Exchange (ETDEWEB)
Mena, Olga; Santiago, Jose; /Fermilab; Weller, Jochen; /University Coll., London /Fermilab
2005-10-01
We show that the current accelerated expansion of the Universe can be explained without resorting to dark energy. Models of generalized modified gravity, with inverse powers of the curvature can have late time accelerating attractors without conflicting with solar system experiments. We have solved the Friedman equations for the full dynamical range of the evolution of the Universe. This allows us to perform a detailed analysis of Supernovae data in the context of such models that results in an excellent fit. Hence, inverse curvature gravity models represent an example of phenomenologically viable models in which the current acceleration of the Universe is driven by curvature instead of dark energy. If we further include constraints on the current expansion rate of the Universe from the Hubble Space Telescope and on the age of the Universe from globular clusters, we obtain that the matter content of the Universe is 0.07 {le} {omega}{sub m} {le} 0.21 (95% Confidence). Hence the inverse curvature gravity models considered can not explain the dynamics of the Universe just with a baryonic matter component.
Energy Technology Data Exchange (ETDEWEB)
Comini-Frota, E.R. [Unidade de Neurologia, Hospital Universitário, Universidade Federal de Minas Gerais, Belo Horizonte, MG (Brazil); Rodrigues, D.H. [Laboratório de Imunofarmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG (Brazil); Miranda, E.C. [Ecoar Diagnostic Center, Belo Horizonte, MG (Brazil); Brum, D.G. [Hospital das Clínicas,Faculdade de Medicina de Ribeirão Preto,Universidade de São Paulo, Ribeirão Preto, SP (Brazil); Kaimen-Maciel, D.R. [Unidade de Neurologia, Hospital Universitário, Universidade Estadual de Londrina, Londrina, PR (Brazil); Donadi, E.A. [Hospital das Clínicas,Faculdade de Medicina de Ribeirão Preto,Universidade de São Paulo, Ribeirão Preto, SP (Brazil); Teixeira, A.L. [Unidade de Neurologia, Hospital Universitário, Universidade Federal de Minas Gerais, Belo Horizonte, MG (Brazil); Laboratório de Imunofarmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG (Brazil)
2011-11-23
The objective of the present study was to determine if there is a relationship between serum levels of brain-derived neurotrophic factor (BDNF) and the number of T2/fluid-attenuated inversion recovery (T2/FLAIR) lesions in multiple sclerosis (MS). The use of magnetic resonance imaging (MRI) has revolutionized the study of MS. However, MRI has limitations and the use of other biomarkers such as BDNF may be useful for the clinical assessment and the study of the disease. Serum was obtained from 28 MS patients, 18-50 years old (median 38), 21 women, 0.5-10 years (median 5) of disease duration, EDSS 1-4 (median 1.5) and 28 healthy controls, 19-49 years old (median 33), 19 women. BDNF levels were measured by ELISA. T1, T2/FLAIR and gadolinium-enhanced lesions were measured by a trained radiologist. BDNF was reduced in MS patients (median [range] pg/mL; 1160 [352.6-2640]) compared to healthy controls (1640 [632.4-4268]; P = 0.03, Mann-Whitney test) and was negatively correlated (Spearman correlation test, r = -0.41; P = 0.02) with T2/FLAIR (11-81 lesions, median 42). We found that serum BDNF levels were inversely correlated with the number of T2/FLAIR lesions in patients with MS. BDNF may be a promising biomarker of MS.
Teaching recovery to medical students.
LENUS (Irish Health Repository)
Feeney, Larkin
2013-03-01
Community mental health services are evolving toward more holistic, patient-centered, recovery-based practices. This change necessitates an attitudinal shift from mental health workers, and training in recovery principles is helpful in achieving this change. Medical students often have narrow, doctor-centered concepts of mental health care. Traditional clinical placements in psychiatry do little to address this. We evaluated a recovery-focused teaching program for medical students in psychiatry.
Directory of Open Access Journals (Sweden)
Teresa De León Mendoza
2012-05-01
Full Text Available An activity required in the educational field is the vocational counseling, which is considered fundamental because of the importance on the future of the students. Nevertheless there are only a few researches that meassure the correlation between the dominant areas identified by the career adviser and with the professional career election taken by the student at the end of high scholl degree.The methodology used in this research allow the vocational counseling or career adviser to provide the student with information of the specific area attached to their interests and flairs. The results of this research work, demonstrate that there is a correlation between the interests, skills and specific areas identified in the student, with the race which elects the graduation of his high school.
Business recovery: an assessment framework.
Stevenson, Joanne R; Brown, Charlotte; Seville, Erica; Vargo, John
2017-11-06
This paper presents a Business Recovery Assessment Framework (BRAF) to help researchers and practitioners design robust, repeatable, and comparable studies of business recovery in various post-disruption contexts. Studies assessing business recovery without adequately considering the research aims, recovery definitions, and indicators can produce misleading findings. The BRAF is composed of a series of steps that guide the decisions that researchers need to make to ensure: (i) that recovery is indeed being measured; (ii) that the indicators of recovery that are selected align with the objectives of the study and the definition of recovery; and, where necessary, (iii) that appropriate comparative control variables are in place. The paper draws on a large dataset of business surveys collected following the earthquakes in Canterbury, New Zealand, on 4 September 2010 and 22 February 2011 to demonstrate the varied conclusions that different recovery indicators can produce and to justify the need for a systematic approach to business recovery assessments. © 2017 The Author(s). Disasters © Overseas Development Institute, 2017.
Full waveform inversion of repeating seismic events to estimate time-lapse velocity changes
Kamei, R.; Lumley, D.
2017-05-01
obtain a reasonably accurate baseline velocity model. Extensive synthetic tests using a realistic velocity model developed from a real project area demonstrate the potential of full waveform inversion to estimate velocity changes from dense surface arrays of seismic stations recording a small number of repeating events. Analysis of sensitivity kernels suggests that positioning sensors at large distances allows for a stable recovery of velocity changes near the event locations by illuminating the inversion area with a wide aperture of angles. We show how full waveform inversion maps the errors in the baseline velocity model and the non-repeatable noise into the estimates of time-lapse velocity changes. Among the three time-lapse inversion methods, parallel inversion is most affected by non-repeatability factors, and is thus the least robust and most contaminated by artefacts. In contrast, the double-difference and bootstrapping methods result in more accurate time-lapse inversions. As the non-repeatability of both sources and noise increases, the bootstrapping method provides more robust and accurate results than the double-difference method.
Approximate inverse preconditioning of iterative methods for nonsymmetric linear systems
Energy Technology Data Exchange (ETDEWEB)
Benzi, M. [Universita di Bologna (Italy); Tuma, M. [Inst. of Computer Sciences, Prague (Czech Republic)
1996-12-31
A method for computing an incomplete factorization of the inverse of a nonsymmetric matrix A is presented. The resulting factorized sparse approximate inverse is used as a preconditioner in the iterative solution of Ax = b by Krylov subspace methods.