• Korean Journal of Radiology
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• v.2 no.4
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• pp.183-191
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• 2001

Objective: To document the signal characteristics of intracerebral hemorrhage (ICH) at evolving stages on diffusion-weighted images (DWI) by comparison with conventional MR images. Materials and Methods: In our retrospective study, 38 patients with ICH underwent a set of imaging sequences that included DWI, T1-and T2-weighted imaging, and fluid-attenuated inversion recovery (FLAIR). In 33 and 10 patients, respectively, conventional and echo-planar T2^* gradient-echo images were also obtained. According to the time interval between symptom onset and initial MRI, five stages were categorized: hyperacute (n=6); acute (n=7); early subacute (n=7); late subacute (n=10); and chronic (n=8). We investigated the signal intensity and apparent diffusion coefficient (ADC) of ICH and compared the signal intensities of hematomas at DWI and on conventional MR images. Results: DWI showed that hematomas were hyperintense at the hyperacute and late subacute stages, and hypointense at the acute, early subacute and chronic stages. Invariably, focal hypointensity was observed within a hyperacute hematoma. At the hyperacute, acute and early subacute stages, hyperintense rims that corresponded with edema surrounding the hematoma were present. The mean ADC ratio was 0.73 at the hyperacute stage, 0.72 at the acute stage, 0.70 at the early subacute stage, 0.72 at the late subacute stage, and 2.56 at the chronic stage. Conclusion: DWI showed that the signal intensity of an ICH may be related to both its ADC value and the magnetic susceptibility effect. In patients with acute stroke, an understanding of the characteristic features of ICH seen at DWI can be helpful in both the characterization of intracranial hemorrhagic lesions and the differentiation of hemorrhage from ischemia.

• Investigative Magnetic Resonance Imaging
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• v.6 no.2
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• pp.152-157
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• 2002

Purpose : The differential diagnosis between Modic type I degenerative spine and infectious spondylitis sometimes is difficult, because the affected bone marrows in both disease show similar signal intensity on conventional MR imaging. We evaluate the usefulness of diffusion-wighted MR imaging for differential diagnosis between Modic type I degenerative spine and infectious spondylitis. Materials and methods : The spin-echo and diffusion-weighted MR images of eight patients with Modic type I degenerative spines and 14 patients with infectious spondylitis diagnosed by clinical findings or CT-guided biopsies we re analyzed. The diffusion-weighted imaging sequence was based on reversed fast imaging with steady-state precession (PSIF). Signal intensity changes of the vertebral bone marrow on conventional spin-echo and diffusion-weighted MR imaging were compared between degenerative spine and infectious spondylitis. Results : On T1-weighte d images, the affeted bone marrow in both disease showed hypointense signals. On T 2-weighted images, all of type I degenerative spine and 11 of infectious spondylitis showed hyperintensity, and three of infectious spondylitis showed heterogeneo us mixed signal intensity. On diffusion-weighted MR images, all of type I degenerative spine were hypointense with peripheral high signal intensity to normal vertebral body, but infectious spondylitis was hyperintense (n = 11) and hypointense (n=3). Conclusion : Diffusion-weighted MR imaging is useful to differentiate Modic type I degenerative spine from infectious spondylitis. On diffusion-weighted images, the high singal intensity of bone marrow suggests infectious spondylitis, whereas the low signal intensity of bone marrow with peripheral focal high signal intensity suggests type I degenerative spine.

• Investigative Magnetic Resonance Imaging
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• v.26 no.2
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• pp.104-116
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• 2022

The purpose of this study is to systematically determine an optimal percentile cut-off in histogram analysis for calculating the mean parameters obtained from a non-Gaussian continuous-time random-walk (CTRW) diffusion model for differentiating individual glioma grades. This retrospective study included 90 patients with histopathologically proven gliomas (42 grade II, 19 grade III, and 29 grade IV). We performed diffusion-weighted imaging using 17 b-values (0-4000 s/mm²) at 3T, and analyzed the images with the CTRW model to produce an anomalous diffusion coefficient (D_m) along with temporal (𝛼) and spatial (𝛽) diffusion heterogeneity parameters. Given the tumor ROIs, we created a histogram of each parameter; computed the P-values (using a Student's t-test) for the statistical differences in the mean D_m, 𝛼, or 𝛽 for differentiating grade II vs. grade III gliomas and grade III vs. grade IV gliomas at different percentiles (1% to 100%); and selected the highest percentile with P < 0.05 as the optimal percentile. We used the mean parameter values calculated from the optimal percentile cut-offs to do a receiver operating characteristic (ROC) analysis based on individual parameters or their combinations. We compared the results with those obtained by averaging data over the entire region of interest (i.e., 100th percentile). We found the optimal percentiles for D_m, 𝛼, and 𝛽 to be 68%, 75%, and 100% for differentiating grade II vs. III and 58%, 19%, and 100% for differentiating grade III vs. IV gliomas, respectively. The optimal percentile cut-offs outperformed the entire-ROI-based analysis in sensitivity (0.761 vs. 0.690), specificity (0.578 vs. 0.526), accuracy (0.704 vs. 0.639), and AUC (0.671 vs. 0.599) for grade II vs. III differentiations and in sensitivity (0.789 vs. 0.578) and AUC (0.637 vs. 0.620) for grade III vs. IV differentiations, respectively. Percentile-based histogram analysis, coupled with the multi-parametric approach enabled by the CTRW diffusion model using high b-values, can improve glioma grading.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.5931-5936
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• 2012

This study was to evaluate the clinical usefulness of the PRESS technique based on the correlation between PRESS technique and biopsy results by applying 3.0T high magnetic field MRS technique for evaluation of non-alcoholic fatty liver disease patients. This experiment were carried out using a 3.0T magnetic resonance imaging equipment. The part data of each spectrum is taken by peak area integration. The part data of resonance peak was used to calculate relative ratio. MR spectral peak in patients with non-alcoholic fatty liver disease is from 0.9 to 1.6 ppm. According to MRS method study result, Patients with NAFLD were obtained with 94% sensitivity and 80% specificity(p=0.000). When compared to normal based on MRS and Biopsy results was valid correlation(r=0.79, p=0.04). Results for NAFLD(r=0.89, p=0.002) also showed a correlation. Therefore, PRESS technique to evaluate patients with non-alcoholic fatty liver disease, the distribution difference between normal liver and fatty liver part is significantly distinguished. Biopsy and MRS fatty liver peak ratio(%) proves high lipid over grade(r = 0.7).

• Investigative Magnetic Resonance Imaging
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• v.15 no.1
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• pp.22-31
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• 2011

Purpose : To compare free-breathing and respiratory-triggered diffusion-weighted imaging on 1.5-T MR system in the detection of hepatic lesions. Materials and Methods: This single-institution study was approved by our institutional review board. Forty-seven patients (mean 57.9 year; M:F = 25:22) underwent hepatic MR imaging on 1.5-T MR system using both free-breathing and respiratory-triggered diffusion-weighted imaging (DWI) at a single examination. Two radiologists retrospectively reviewed respiratory-triggered and free-breathing sets (B50, B400, B800 diffusion weighted images and ADC map) in random order with a time interval of 2 weeks. Liver SNR and lesion-to-liver CNR of DWI were calculated measuring ROI. Results : Total of 62 lesions (53 benign, 9 malignant) that included 32 cysts, 13 hemangiomas, 7 hepatocellular carcinomas (HCCs), 5 eosinophilic infiltration, 2 metastases, 1 eosinophilic abscess, focal nodular hyperplasia, and pseudolipoma of Glisson's capsule were reviewed by two reviewers. Though not reaching statistical significance, the overall lesion sensitivities were increased in respiratory-triggered DWI [reviewer1: reviewer2, 47/62(75.81%):45/62(72.58%)] than free-breathing DWI [44/62(70.97%):41/62(66.13%)]. Especially for smaller than 1 cm hepatic lesions, sensitivity of respiratory-triggered DWI [24/30(80%):21/30(70%)] was superior to free-breathing DWI [17/30(56.7%):15/30(50%)]. The diagnostic accuracy measuring the area under the ROC curve (Az value) of free-breathing and respiratory-triggered DWI was not statistically different. Liver SNR and lesion-to-liver CNR of respiratory-triggered DWI ($87.6{\pm}41.4$, $41.2{\pm}62.5$) were higher than free-breathing DWI ($38.8:{\pm}13.6$, $24.8{\pm}36.8$) (p value < 0.001, respectively). Conclusion: Respiratory-triggered diffusion-weighted MR imaging seemed to be better than free-breathing diffusion-weighted MR imaging on 1.5-T MR system for the detection of smaller than 1 cm lesions by providing high SNR and CNR.

• Journal of the Korean Magnetic Resonance Society
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• v.9 no.1
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• pp.29-37
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• 2005

Intra-cellular drug uptake in Xenopus laevis oocyte has been elucidated using localized MR spectroscopy (MRS) and PFG NMR techniques at a 600 $MH_z$(Bruker, 14.1 T) NMR spectrometer. The localized MRS has been done with a homemade probe, and shows the intra-cellular uptake of nicotinamide. The self-diffusion of the molecule in Xenopus oocyte was obtained by PFG NMR technique. The measured data are well fitted with a linear combination of two exponential functions, which shows that there are two types of drug molecules, intra-and extra-cellular molecules. Diffusion coefficients of intra- and extra-cellular drug molecules are 3.7 $\times$ $10^{-11}$ $\m^{2}/s$and 6.4 $\times$ $10^{-10}$ $\m^{2}/s$, respectively. In the weighting factors there is shown that about 5% of drug molecule is inside the cells. These techniques can be used for drug screening in molecule-, cell-, and tissue-based preclinical test.

• Investigative Magnetic Resonance Imaging
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• v.17 no.2
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• pp.123-132
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• 2013

Purpose : We report the results of the various parameters of diffusion tensor imaging (DTI) and CSF flow study of the cervical spinal cord using magnetic resonance (MR) imaging techniques. Materials and Methods: Intramedullary FA and MD were measured in the gray matter and posterior cord of the white matter and both lateral cords of the white matter at the C2-3, C4-5, C5-6 spinal levels. For the CSF flow study, velocity encoding was obtained at the C2-3, C4-5, C5-6 spinal levels. Results: There was a significant difference of the FA and MD between the white matter and gray matter (p < 0.05). The FA of the gray matter was significantly different according to the cervical spinal cord levels (p < 0.05). Otherwise, the FA and MD parameters were not significantly different (p > 0.05). The mean peak systolic velocity and mean peak diastolic velocity were $5.18{\pm}2.00cm/sec$ and $-7.32{\pm}3.18cm/sec$, respectively from C2 to C6 spinal cords. There was no significant difference in these velocities among the cervical spinal cord (p > 0.05). Conclusion: This basic information about DTI and CSF dynamics of the cervical spinal cord may be useful for assessing cervical spinal cord abnormalities using MR imaging.

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.24-24
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• 2003

Purpose： It is known that diffusion-weighted MR imaging (DWI) is helpful in the evaluation of malignancy grading in brain tumor. This study was to evaluate the DWls with different b-values of various brain tumors in order to determine optimal b-values on 3T MR unit. Method： On a 3T MR unit, DWls with b-values of 1, 000, 3, 000 and 5, 000 s/mm2 were obtained in 20 patients of pathologically-proven brain tumors (7 metastases, 4 high grade gliomas, 2 Iymphomas, 2 low grade gliomas, 2 germinomas, and one each of germinoma, meningioma, hemangioblastoma and central neurocytoma. The overall image quality, contrast between normal brain parenchyma and tumor and signal intensities of solid and cystic components were comparatively evaluated among DWls with different b-values by visual inspection.

• Biomedical Science Letters
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• v.11 no.3
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• pp.307-310
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• 2005

Cerebral ischemia results in neuronal changes in remote areas that have fiber connections with the ischemic area. The aim of this study was to investigate the nigral changes by examining the correlation between the apparent diffusion coefficient (ADC) and the tissue structure. Sprague-Dawley rats were subjected to middle cerebral artery occlusion. Four days after the occlusion, when T2-weighted images revealed the presence of an area of high signal intensity in the ipsilateral substantia nigra, and the ADCs were calculated and imaged. Histopathologic examination by both light and electron microscopy was performed on day 4 after surgery. This finding was consistent with the high signal intensity seen on T2-weighted and diffusion-weighted images, as well as with the ADC reduction, but we did not expect to observe uniform ADC reduction attributable mainly to astrocytic swelling in the perivascular end-feet.

• Investigative Magnetic Resonance Imaging
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• v.17 no.2
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• pp.101-109
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• 2013

Objective: To investigate roles of dynamic contrast enhanced magnetic resonance (DCE MR) and diffusion-weighted (DW) imaging in preoperative prediction of underestimation of ductal carcinoma in situ (DCIS) ${\geq}2cm$ on US guided core needle biopsy. Materials and Methods: Twenty two patients with DCIS on US-guided 14 gauge core needle biopsy were included. Patients were divided into a group with and without DCIS underestimation based on histopathology. MR images including DCE and DW imaging were obtained with a 3.0-T MR. The lesion type (mass or non-mass), enhancement pattern, peak enhancement, and apparent diffusion coefficient (ADC) values of proven malignant masses were generated using software of CADstream and compared between two groups using Fisher's exact test and Mann Whitney test. Results: Eight patients were in the group with underestimation and 14 patients were in the group without underestimation. The lesion type and enhancement pattern were not different between two groups (P values = 1.000 and 0.613, respectively). The median peak enhancement of lesions with underestimation was 159.5%, higher than 133.5% of those without underestimation, but not significant (P value = 0.413). The median ADC value of lesions with underestimation was $1.26{\times}10^{-3}mm^2/sec$, substantially lower than $1.35{\times}10^{-3}mm^2/sec$ of those without underestimation (P value = 0.094). Conclusion: ADC values had the potential to preoperatively predict DCIS underestimation on US-guided core needle biopsy, although a large prospective series study should be conducted to confirm these results.