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Zdenek Kadanka - One of the best experts on this subject based on the ideXlab platform.
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magnetic resonance diffusion tensor imaging in patients with cervical spondylotic spinal cord Compression correlations between clinical and electrophysiological findings
Spine, 2012Co-Authors: Milos Kerkovský, Josef Bednarik, Ladislav Dusek, Andrea Sprlakovapukova, Igor Urbanek, Marek Mechl, Vlastimil Valek, Zdenek KadankaAbstract:Study design A prospective study evaluating a cohort of patients with spondylotic cervical spine Compression. Objective To analyze the potential of diffusion tensor imaging (DTI) of the cervical spinal cord in the detection of changes associated with spondylotic myelopathy, with particular reference to clinical and electrophysiological findings. Summary of background data Conventional magnetic resonance imaging (MRI) may provide confusing findings because of a frequent disproportion between the degree of the spinal cord Compression and clinical symptoms. The DTI is known to be more sensitive to subtle pathological changes of the spinal cord compared with conventional MRI. Methods The DTI of the cervical spinal cord was performed within a group of 52 patients with spondylotic spinal cord Compression and 13 healthy volunteers on a 1.5-T MRI scanner. All patients underwent clinical examination that differentiated between asymptomatic and symptomatic myelopathy subgroups, and 45 patients underwent electrophysiological examination. We measured the apparent diffusion coefficient and fractional anisotropy of the spinal cord at C2/C3 Level without Compression and at the maximal Compression Level (MCL). Sagittal spinal canal diameter, cross-sectional spinal cord area, and presence of T2 hyperintensity at the MCL were also recorded. Nonparametric statistical testing was used for comparison of controls with subgroups of patients. Results Significant differences in both the DTI parameters measured at the MCL, between patients with Compression and control group, were found, while no difference was observed at the nonCompression Level. Moreover, fractional anisotropy values were lower and apparent diffusion coefficient values were higher at the MCL in the symptomatic patients than in the asymptomatic patients. The DTI showed higher potential to discriminate between clinical subgroups in comparison with standard MRI parameters and electrophysiological findings. Conclusion The DTI appears to be a promising imaging modality in patients with spondylotic spinal cord Compression. It reflects the presence of symptomatic myelopathy and shows considerable potential for discriminating between symptomatic and asymptomatic patients.
Koji Matsumoto - One of the best experts on this subject based on the ideXlab platform.
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reduced field of view diffusion tensor imaging of the spinal cord shows motor dysfunction of the lower extremities in patients with cervical Compression myelopathy
Spine, 2018Co-Authors: Satoshi Maki, Kazuhisa Takahashi, Masao Koda, Mitsutoshi Ota, Yoshihiro Oikawa, Koshiro Kamiya, Taigo Inada, Takeo Furuya, Yoshitada Masuda, Koji MatsumotoAbstract:STUDY DESIGN A cross-sectional study. OBJECTIVE The aim of this study was to quantify spinal cord dysfunction at the tract Level in patients with cervical compressive myelopathy (CCM) using reduced field-of-view (rFOV) diffusion tensor imaging (DTI). SUMMARY OF BACKGROUND DATA Although magnetic resonance imaging (MRI) is the standard used for radiological evaluation of CCM, information acquired by MRI does not necessarily reflect the severity of spinal cord disorder. There is a growing interest in developing imaging methods to quantify spinal cord dysfunction. To acquire high-resolution DTI, a new scheme using rFOV has been proposed. METHODS We enrolled 10 healthy volunteers and 20 patients with CCM in this study. The participants were studied using a 3.0-T MRI system. For DTI acquisitions, diffusion-weighted spin-echo rFOV single-shot echo-planar imaging was used. Regions-of-interest (ROI) for the lateral column (LC) and posterior column (PC) tracts were determined on the basis of a map of fractional anisotropy (FA) of the spinal cord and FA values were measured. The FA of patients with CCM was compared with that of healthy controls and correlated with Japanese Orthopaedic Association (JOA) score. RESULTS In LC and PC tracts, FA values in patients with CCM were significantly lower than in healthy volunteers. Total JOA scores correlated moderately with FA in LC and PC tracts. JOA subscores for motor dysfunction of the lower extremities correlated strongly with FA in LC and PC tracts. CONCLUSION It is feasible to evaluate the cervical spinal cord at the tract Level using rFOV DTI. Although FA values at the maximum Compression Level were not well correlated with total JOA scores, they were strongly correlated with JOA subscores for motor dysfunction of the lower extremities. Our findings suggest that FA reflects white matter dysfunction below the maximum Compression Level and FA can be used as an imaging biomarker of spinal cord dysfunction. Level OF EVIDENCE 4.
Volkov, Valentyn S. - One of the best experts on this subject based on the ideXlab platform.
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Densification of single-walled carbon nanotube films
'AIP Publishing', 2021Co-Authors: Drozdov Grigorii, Ostanin Igor, Xu Hao, Wang Yuezhou, Dumitricǎ Traian, Grebenko Artem, Tsapenko, Alexey P., Gladush Yuriy, Ermolaev Georgy, Volkov, Valentyn S.Abstract:Nanometer-thin single-walled carbon nanotube (CNT) films collected from the aerosol chemical deposition reactors have gathered attention for their promising applications. Densification of these pristine films provides an important way to manipulate mechanical, electronic, and optical properties. To elucidate the underlying microstructural Level restructuring, which is ultimately responsible for the change in properties, we perform large scale vector-based mesoscopic distinct element method simulations in conjunction with electron microscopy and spectroscopic ellipsometry characterization of pristine and densified films by drop-cast volatile liquid processing. Matching with the microscopy observations, pristine CNT films with a finite thickness are modeled as self-assembled CNT networks comprising entangled dendritic bundles with branches extending down to individual CNTs. Simulations of these films under uniaxial Compression uncover a soft deformation regime extending up to an ∼75% strain. When removing the loads, the pre-compressed samples evolve into homogeneously densified films with thickness values depending on both the pre-Compression Level and the sample microstructure. The significant reduction in thickness is attributed to the underlying structural changes occurring at the 100 nm scale, including the zipping of the thinnest dendritic branches.Peer reviewe
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Densification of Single-Walled Carbon Nanotube Films: Mesoscopic Distinct Element Method Simulations and Experimental Validation
'AIP Publishing', 2020Co-Authors: Drozdov Grigorii, Ostanin Igor, Xu Hao, Wang Yuezhou, Dumitricǎ Traian, Grebenko Artem, Tsapenko, Alexey P., Gladush Yuriy, Ermolaev Georgy, Volkov, Valentyn S.Abstract:Nanometer-thin single-walled carbon nanotube (CNT) films collected from the aerosol chemical deposition reactors have gathered attention for their promising applications. Densification of these pristine films provides an important way to manipulate mechanical, electronic, and optical properties. To elucidate the underlying microstructural Level restructuring, which is ultimately responsible for the change in properties, we perform large scale vector-based mesoscopic distinct element method simulations in conjunction with electron microscopy and spectroscopic ellipsometry characterization of pristine and densified films by drop-cast volatile liquid processing. Matching with the microscopy observations, pristine CNT films with a finite thickness are modeled as self-assembled CNT networks comprising entangled dendritic bundles with branches extending down to individual CNTs. Simulations of these films under uniaxial Compression uncover a soft deformation regime extending up to an ∼75% strain. When removing the loads, the pre-compressed samples evolve into homogeneously densified films with thickness values depending on both the pre-Compression Level and the sample microstructure. The significant reduction in thickness is attributed to the underlying structural changes occurring at the 100 nm scale, including the zipping of the thinnest dendritic branches
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Densification of Single-Walled Carbon Nanotube Films: Mesoscopic Distinct Element Method Simulations and Experimental Validation
'AIP Publishing', 2020Co-Authors: Drozdov Grigorii, Ostanin Igor, Xu Hao, Wang Yuezhou, Dumitricǎ Traian, Grebenko Artem, Tsapenko, Alexey P., Gladush Yuriy, Ermolaev Georgy, Volkov, Valentyn S.Abstract:Nanometer thin single-walled carbon nanotube (CNT) films collected from the aerosol chemical deposition reactors have gathered attention for their promising applications. Densification of these pristine films provides an important way to manipulate the mechanical, electronic, and optical properties. To elucidate the underlying microstructural Level restructuring, which is ultimately responsible for the change in properties, we perform large scale vector-based mesoscopic distinct element method simulations in conjunction with electron microscopy and spectroscopic ellipsometry characterization of pristine and densified films by drop-cast volatile liquid processing. Matching the microscopy observations, pristine CNT films with finite thickness are modeled as self-assembled CNT networks comprising entangled dendritic bundles with branches extending down to individual CNTs. Simulations of the film under uniaxial Compression uncover an ultra-soft densification regime extending to a ~75% strain, which is likely accessible with the surface tensional forces arising from liquid surface tension during the evaporation. When removing the loads, the pre-compressed samples evolve into homogeneously densified films with thickness values depending on both the pre-Compression Level and the sample microstructure. The significant reduction in thickness, confirmed by our spectroscopic ellipsometry, is attributed to the underlying structural changes occurring at the 100 nm scale, including the zipping of the thinnest dendritic branches.Comment: 12 figure
Milos Kerkovský - One of the best experts on this subject based on the ideXlab platform.
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magnetic resonance diffusion tensor imaging in patients with cervical spondylotic spinal cord Compression correlations between clinical and electrophysiological findings
Spine, 2012Co-Authors: Milos Kerkovský, Josef Bednarik, Ladislav Dusek, Andrea Sprlakovapukova, Igor Urbanek, Marek Mechl, Vlastimil Valek, Zdenek KadankaAbstract:Study design A prospective study evaluating a cohort of patients with spondylotic cervical spine Compression. Objective To analyze the potential of diffusion tensor imaging (DTI) of the cervical spinal cord in the detection of changes associated with spondylotic myelopathy, with particular reference to clinical and electrophysiological findings. Summary of background data Conventional magnetic resonance imaging (MRI) may provide confusing findings because of a frequent disproportion between the degree of the spinal cord Compression and clinical symptoms. The DTI is known to be more sensitive to subtle pathological changes of the spinal cord compared with conventional MRI. Methods The DTI of the cervical spinal cord was performed within a group of 52 patients with spondylotic spinal cord Compression and 13 healthy volunteers on a 1.5-T MRI scanner. All patients underwent clinical examination that differentiated between asymptomatic and symptomatic myelopathy subgroups, and 45 patients underwent electrophysiological examination. We measured the apparent diffusion coefficient and fractional anisotropy of the spinal cord at C2/C3 Level without Compression and at the maximal Compression Level (MCL). Sagittal spinal canal diameter, cross-sectional spinal cord area, and presence of T2 hyperintensity at the MCL were also recorded. Nonparametric statistical testing was used for comparison of controls with subgroups of patients. Results Significant differences in both the DTI parameters measured at the MCL, between patients with Compression and control group, were found, while no difference was observed at the nonCompression Level. Moreover, fractional anisotropy values were lower and apparent diffusion coefficient values were higher at the MCL in the symptomatic patients than in the asymptomatic patients. The DTI showed higher potential to discriminate between clinical subgroups in comparison with standard MRI parameters and electrophysiological findings. Conclusion The DTI appears to be a promising imaging modality in patients with spondylotic spinal cord Compression. It reflects the presence of symptomatic myelopathy and shows considerable potential for discriminating between symptomatic and asymptomatic patients.
Young Hoon Kim - One of the best experts on this subject based on the ideXlab platform.
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jpeg2000 3d Compression vs 2d Compression an assessment of artifact amount and computing time in compressing thin section abdomen ct images
Medical Physics, 2009Co-Authors: Bohyoung Kim, Kil Joong Kim, Kyoung Ho Lee, Heung-sik Kang, Young Hoon Kim, Thomas Richter, So Yeon Kim, Jinwook SeoAbstract:To assess the advantages of the Joint Photographic Experts Group (JPEG)2000 3D (part 2) over JPEG2000 in compressing thin-section abdomen CT data sets, 60 thin-section (0.67 mm) scans from 35 males and 25 females, ranging from 23 to 95 years of age (mean, 58 years), were compressed reversibly (as a negative control) and irreversibly to 4:1, 6:1, 8:1, 10:1, and 12:1 using JPEG2000 3D and JPEG2000 algorithms. Encoding and decoding times and peak signal-to-noise ratios (PSNRs) were measured. For 60 (one image per scan) representative sections containing abnormalities, three radiologists independently compared original and compressed images and graded Compression artifacts as 0 (none, indistinguishable), 1 (barely perceptible), 2 (subtle), or 3 (significant). According to pooled radiologists' responses, the range of visually lossless threshold (VLT, the highest Compression ratio at which a compressed image is indistinguishable from its original) was determined as one of 12:1. Wilcoxon signed rank tests and exact tests for paired proportions were used for the comparisons between the two Compressions. At each irreversible Compression ratio, compared to JPEG2000, JPEG2000 3D required two- or threefold greater computing times (p < 0.001) and introduced less artifacts in terms of PSNR (p <0.001) and the grade (p < 0.02 at 6:1 or higher) and the presence of perceived artifacts (p <0.008, at 6:1 for all readers and at 8:1 for two readers). According to PSNR and readers' responses, 6:1 and 8:1 JPEG2000 3D Compressions showed more artifacts than 4:1 and 6:1 JPEG2000 Compressions, respectively, and 10:1 and 12:1 JPEG2000 3D Compressions showed similar artifacts to those of 8:1 and 10:1 JPEG2000 Compressions, respectively. The determined VLT range was higher for JPEG2000 3D than for JPEG2000 (p < 0.001): the 3D Compression showed the VLT ranges of 4:1-6:1, 6:1-8:1, and 8:1-10:1 for 24 (40%), 30 (50%), and 6 (10%) of the 60 original images, respectively, while the 2D Compression showed the VLT ranges of <4:1, 4:1-6:1, and 6:1-8:1 for 1 (1.7%), 40 (66.7%), and 19 (31.6%) images, respectively. Compared to JPEG2000, JPEG2000 3D increased the VLT range in 23 of the 60 original images by one (n=22) or two ranges (n=1), while the remaining 37 images had the same VLT range between the two Compressions. In conclusion, compared to JPEG2000 Compression, JPEG2000 3D Compression yields less artifacts in compressing thin-section abdomen CT images but requires significantly greater computing times. For the tested data set compressed to the range from 4:1 to 12:1, JPEG2000 3D could increase Compression Level reasonably (by 2 or less in terms of Compression ratio) compared to JPEG2000 for the same amount of artifacts.
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Regional difference in Compression artifacts in low-dose chest CT images: effects of mathematical and perceptual factors.
American Journal of Roentgenology, 2008Co-Authors: Kil Joong Kim, Bohyoung Kim, Kyoung Ho Lee, Tae Jung Kim, Rafal Mantiuk, Heung-sik Kang, Young Hoon KimAbstract:OBJECTIVE. The objective of our study was to investigate the difference of perceptible artifacts between the lungs and the chest wall and mediastinum in Joint Photographic Experts Group (JPEG) 2000–compressed low-dose chest CT images and to show that a perceptual image quality metric—the High–Dynamic Range Visual Difference Predictor (HDR-VDP)—can reproduce this regional difference.MATERIALS AND METHODS. Twenty images were compressed reversibly and irreversibly to 6:1–30:1. To analyze the two regions separately (lungs; and chest wall and mediastinum), the compressed pixels outside each tested region were replaced with the original pixels. By comparing the compressed and original images, three radiologists independently rated the Compression artifacts as grade 0, none, indistinguishable; 1, barely perceptible; 2, subtle; or 3, significant. At each Compression Level, the two regions were compared for the readers' responses, peak signal-to-noise ratio (PSNR), and HDR-VDP results. Wilcoxon's signed rank tests...