Measuring Fractional Anisotropy of the Corpus Callosum Using Diffusion Tensor Imaging: Mid-Sagittal versus Axial Imaging Planes

김응엽,박해정,김동현,이승구,김진아 대한영상의학회 2008 Korean Journal of Radiology Vol.9 No.5

Objective: Many diffusion tensor imaging (DTI) studies of the corpus callosum (CC) have been performed with a relatively thick slice thickness in the axial plane, which may result in underestimating the fractional anisotropy (FA) of the CC due to a partial volume effect. We hypothesized that the FA of the CC can be more accurately measured by using mid-sagittal DTI. We compared the FA values of the CC between the axial and mid-sagittal DTI. Materials and Methods: Fourteen healthy volunteers underwent MRI at 3.0 T. DTI was performed in both the mid-sagittal and axial planes. One 5-mm mid-sagittal image and twenty-five 2-mm axial images were obtained for the CC. The five regions of interest (ROIs) that included the prefrontal (I), premotor and supplementary motor (II), motor (III), sensory (IV) and parietal, temporal and occipital regions (V) were drawn along the border of the CC on each sagittal FA map. The FA values obtained from each region were compared between the two sagittal maps. Results: The FA values of all the regions, except for region V, were significantly increased on the mid-sagittal imaging. The FA values in region IV were significantly underestimated on the mid-sagittal image from the axial imaging, compared with those in the regions I and V (p = 0.037 and p = 0.001, respectively). Conclusion: The FA values of the CC were significantly higher on the midsagittal DTI than those on the axial DTI in regions I-IV, and particularly in the region IV. Mid-sagittal DTI may provide more accurate FA values of the CC than can the axial DTI, and mid-sagittal DTI may be more desirable for studies that compare between patients and healthy subjects. Objective: Many diffusion tensor imaging (DTI) studies of the corpus callosum (CC) have been performed with a relatively thick slice thickness in the axial plane, which may result in underestimating the fractional anisotropy (FA) of the CC due to a partial volume effect. We hypothesized that the FA of the CC can be more accurately measured by using mid-sagittal DTI. We compared the FA values of the CC between the axial and mid-sagittal DTI. Materials and Methods: Fourteen healthy volunteers underwent MRI at 3.0 T. DTI was performed in both the mid-sagittal and axial planes. One 5-mm mid-sagittal image and twenty-five 2-mm axial images were obtained for the CC. The five regions of interest (ROIs) that included the prefrontal (I), premotor and supplementary motor (II), motor (III), sensory (IV) and parietal, temporal and occipital regions (V) were drawn along the border of the CC on each sagittal FA map. The FA values obtained from each region were compared between the two sagittal maps. Results: The FA values of all the regions, except for region V, were significantly increased on the mid-sagittal imaging. The FA values in region IV were significantly underestimated on the mid-sagittal image from the axial imaging, compared with those in the regions I and V (p = 0.037 and p = 0.001, respectively). Conclusion: The FA values of the CC were significantly higher on the midsagittal DTI than those on the axial DTI in regions I-IV, and particularly in the region IV. Mid-sagittal DTI may provide more accurate FA values of the CC than can the axial DTI, and mid-sagittal DTI may be more desirable for studies that compare between patients and healthy subjects.

원발성 비강 림프종의 CT및 MR영상 : 초기 진단 및 추적 검사 시 유용성

김응엽 대한영상의학회 1998 대한영상의학회지 Vol.39 No.5

Purpose : To describe CT and MR findings of Primary nasal NK/T-cell lymphoma and to evaluate the usefulness of CT and MR imaging for initial diagnosis and during follow-up. Materials and Methods : Thirteen patients with biopsy-proven primary nasal NK/T-cell lymphoma (M:8, F:5;age 30-78, mean:47.3 years) were included in this study. CT scans were obtained in seven patients and MR images in ten, and both CT and MR images in four. During follow-up, CT images were obtained in four patients, MR images in eight, and both types of image in two. Signal intensity or attenuation, location, and shape of the tumor were assessed on CT and MR images, which were also compared in terms of evaluation of the extent of the tumor and the assessment of residual tumor during follow-up.Results : Enhanced CT scans showed slightly lower(6/7) or iso-attenuation (1/7) or the tumor than of the wall of the nasal cavity. In all cases, the tumor was of slightly lower signal intensity on T2WI and gadolinium-enhancedT1WI than nasal cavity mucosa. Infiltrative wall thickening of the nasal cavity (13/13) and a polypoid mass (5/13) were demonstrated on CT and MR images. The tumor margin was partially indistinct (6/7) or distinct (1/7) on initial CT, but distinctly identified on initial MR images in all cases. During follow-up, MR was superior to CT for the assessment of residual tumor in two patients. Conclusion : Infiltrative wall thickening of the nasal cavity may be a characteristic feature of primary nasal NK/T-cell lymphoma, and MR images were superior to CT for the assessment of tumor extent and for the diagnosis of residual tumor during follow-up.

비전형적인 위치에 생긴 중추신경계 Langerhans 조직구 증식증: 증례 보고

김응엽,이재규,김찬교,이창현,강창호,정필욱,Kim, E. Yup,Lee, Jae-Kyu,Kim, Chan-Kyo,Lee, Chang-Hyun,Kang, Chang-Ho,Chung, Phil-Wook 대한영상의학회 2003 대한영상의학회지 Vol.48 No.3

중추신경계 Langerhans 조직구 증식증은 시상하부-뇌하수체 축을 주로 침범하고 자기공명 영상(MRI)T1 강조 영상에서 흔히 뇌하수체 후엽의 밝은 점이 보이지 않고, 누두부 비후 또 는 시상하부에 종괴가 보이는 것으로 알려져 있다. 저자들은 뇌하수체 후엽의 밝은 점이 보이지 않고 시상하부와 누두부에 이상 소견 없이 소뇌와 대뇌기저핵을 침범한 중추신경계 Langerhans 조직구 증식증 1예를 보고하고자 한다. Langerhans cell histiocytosis of the central nervous system (CNS) usually involves the hypothalamic-pituitary axis, and T1-weighted MR images normally demonstrate infundibular thickening and/or a mass lesion in the hypothalamus and the absence of a posterior pituitary "bright spot". We recently encountered a case of CNS Langerhans cell histiocytosis with no posterior pituitary "bright spot"and with lesions involving the cerebellum and basal ganglia but not the hypothalamic-pituitary axis.

Diagnosis of Early-Stage Idiopathic Parkinson’s Disease Using High-Resolution Quantitative Susceptibility Mapping Combined with Histogram Analysis in the Substantia Nigra at 3 T

김응엽,성영희,신형걸,노영,남윤호,이종호 대한신경과학회 2018 Journal of Clinical Neurology Vol.14 No.1

Background and Purpose To test whether nigrosome-1 imaging using high-resolution quantitative susceptibility mapping (QSM) combined with histogram analysis can improve the diagnostic accuracy in early-stage idiopathic Parkinson’s disease (IPD) patients. Methods Three-dimensional multiecho gradient-recalled echo images (0.5×0.5×1.0 mm3) were obtained at 3 T for QSM in 38 patients with IPD and 25 healthy subjects. To segment the substantia nigra (SN), regions of interest (ROIs) were semiautomatically drawn at the location below the red nucleus, and the normal-appearing nigrosome-1 was determined by manual correction. QSM histograms were obtained within the ROI. The segmented SN regions on the right and left that had higher mean susceptibility values and fewer voxels with susceptibility values lower than 60, 65, 70, 75, and 80 ppb were chosen for comparisons between the IPD patients and healthy subjects. These results were compared with those of the visual assessments of nigrosome-1 in susceptibility map-weighted imaging (SMWI) by analyzing receiver operating characteristics curves. Results The proportion of voxels with susceptibility values lower than 70 ppb showed the best diagnostic performance, with its value differing significantly between the IPD patients (median=0, interquartile range=0–0.23) and healthy subjects (median=10.67, interquartile range=5.98–21.57) (p<0.0001). The number of voxels with susceptibility values lower than 60, 65, 70, 75, and 80 ppb showed worse diagnostic performances but were still significantly better than that of the mean susceptibility value (p=0.0249, 0.0192, 0.0183, 0.0191, and 0.0186, respectively), which also differed significantly between the two groups: 125.81±16.27 ppb (mean±standard deviation) in IPD versus 98.41±11.70 ppb in healthy subjects (p<0.0001). Additionally, using the proportion of voxels with susceptibility values lower than 70 ppb provided significantly better diagnostic performance than did visual assessments of SMWI (p=0.0143). Conclusions High-spatial-resolution QSM combined with histogram analysis at 3 T can improve the diagnostic accuracy of early-stage IPD.

뇌졸중 최신지견: 2006년 뇌졸중의 신경영상의학의 중요 연구

김응엽 대한뇌졸중학회 2007 Journal of stroke Vol.9 No.1

Intracranial Dural Metastasis of Ewing’s Sarcoma: a Case Report

김응엽,Seung-Koo Lee,Dong Joon Kim,김진아,Kyu-Sung Lee,Woohee Jung,Dong Ik Kim 대한영상의학회 2008 Korean Journal of Radiology Vol.9 No.1

Although intracranial dural metastasis of Ewing's sarcoma is a very rare finding, its imaging characteristics are similar to those of its primary form in the central nervous system. Thus, this tumor must be considered in the differential diagnosis of extra-axial dural masses.

경사에코 MR영상에서 보이는 뇌의 미세 출혈에 의한 저신호 강도 병변에 대한 연구

김응엽 대한영상의학회 1998 대한영상의학회지 Vol.38 No.5

Purpose: To assess the relationship between low signal intensity lesions, as seen on gradient-echo MR, andclinical factors. Materials and Methods: In 269 patients with cerebral ischemic symptoms, we analysed the resultsof gradient-echo MR. One hundred and thirty-nine of the patients were male and 130 were female;their ages rangedfrom 40 to 88(mean, 64) years. Low signal intensity lesions were analyzed according to the dominant location;superficial (cortex and subcortical white matter) or deep (basal ganglia, thalamus, periventricular white matter,and cerebellum). We analyzed the relationship between low signal intensity lesions and clinical factors includinghypertension, diabetes mellitus (DM), and spontaneous intracerebral hemorrhage (ICH). Results: Low signalintensity lesions were found in 66 of 269 patients(25%); hypertension was present in 57 of the 66(86%, p < 0.05),DM in nine(14%, p > 0.05), and spontaneous ICH in 26 (39%, p < 0.05). The dominant location of these lesions wassuperficial (n=19), deep (n=45), or both (n=2). Hypertension was present in 13 (68%) of the patients in whom thelesion was superficial, and in 42 (93%) of those in whom it was deep. Hypertension was not present in nine of 66patients(14%) with low signal intensity lesions; in six of these(66%), low signal intensity lesions were presentmainly in the subcortical white matter or cortex and in four of the six, such lesions were found only insubcortical white matter or cortex. Conclusion: Cerebral low signal intensity lesions, as seen on gradient-echo MRimaging were associated with clinical factors such as hypertension and spontaneous ICH, and hypertension was morefrequently found in patients in whom the location of low signal intensity lesions was deep.

Assessment of Posterior Globe Flattening: Two-Dimensional versus Three-Dimensional T-Weighted Imaging

안준형,김응엽 대한자기공명의과학회 2015 Investigative Magnetic Resonance Imaging Vol.19 No.3

Purpose: To compare the frequency of posterior globe flattening between twodimensionalT2-weighted imaging (2D T2WI) and three-dimensional (3D T2WI). Materials and Methods: Sixty-nine patients (31 female; mean age, 44.4 years) whohad undergone both 5-mm axial T2WI and sagittal 3D 1-mm isovoxel T2WI of thewhole brain for evaluation of various diseases (headache [n = 30], large hemorrhage [n= 19], large tumor or leptomeningeal tumor spread [n = 15], large infarct [n = 3], andbacterial meningitis [n = 2]) were used in this study. Two radiologists independentlyreviewed both sets of images at separate sessions. Axial T2WI and multi-planarimaging of 3D T2WI were visually assessed for the presence of globe flattening. Theoptic nerve sheath diameter (ONSD) was measured at a location 4 mm posterior toeach globe on oblique coronal imaging reformatted from 3D T2WI. Results: There were significantly more globes showing posterior flattening on3D T2WI (105/138 [76.1%]) than on 2D T2WI (27/138 [19.6%], P = 0.001). Interobserveragreement was excellent for both 2D T2WI and 3D T2WI (Cohen’s kappa =0.928 and 0.962, respectively). Intra-class correlation coefficient for the ONSD wasalmost perfect (Cohen’s kappa = 0.839). The globes with posterior flattening hadsignificantly larger ONSD than those without on both 2D and 3D T2WI (P < 0.001;6.14 mm ± 0.44 vs. 5.74 mm ± 0.44 on 2D T2WI; 5.90 mm ± 0.47 vs. 5.56 mm ± 0.34on 3D T2WI). Optic nerve protrusion was significantly more frequent on reformatted1-mm 3D T2WI than on 5-mm 2D T2WI (8 out of 138 globes on 3D T2WI versus oneon 2D T2WI; P = 0.018). Conclusion: Posterior globe flattening is more frequently observed on 3D T2WI thanon 2D T2WI in patients suspected of having increased intracranial pressure. Theglobes with posterior flattening have significantly larger ONSD than those without.

Fast Motion Artifact Correction Using l1-norm

조상영,김응엽,김동현 대한자기공명의과학회 2009 Investigative Magnetic Resonance Imaging Vol.13 No.1

Purpose : Patient motion during magnetic resonance (MR) imaging is one of the major problems due to its long scan time. Entropy based post-processing motion correction techniques have been shown to correct motion artifact effectively. One of main limitations of these techniques however is its long processing time. In this study, we propose several methods to reduce this long processing time effectively. Materials and Methods : To reduce the long processing time, we used the separability property of two dimensional Fourier transform (2-D FT). Also, a computationally light metric (sum of all image pixel intensity) was used instead of the entropy criterion. Finally, partial Fourier reconstruction, in particular the projection onto convex set (POCS) method, was combined thereby reducing the size of the data which should be processed and corrected. Results : Time savings of each proposed method are presented with different data size of brain images. In vivo data were processed using the proposed method and showed similar image quality. The total processing time was reduced to 15% in two dimensional images and 30% in the three dimensional images. Conclusion : The proposed methods can be useful in reducing image motion artifacts when only post-processing motion correction algorithms are available. The proposed methods can also be combined with parallel imaging technique to further reduce the processing times.

High Resolution Time Resolved Contrast Enhanced MR Angiography Using k-t FOCUSS

정홍,김응엽,예종철 대한자기공명의과학회 2010 Investigative Magnetic Resonance Imaging Vol.14 No.1

Purpose : Recently, the Recon Challenge at the 2009 ISMRM workshop on Data Sampling and Image Reconstruction at Sedona, Arizona was held to evaluate feasibility of highly accelerated acquisition of time resolved contrast enhanced MR angiography. This paper provides the step-by-step description of the winning results of k-t FOCUSS in this competition. Materials and Methods : In previous works, we proved that k-t FOCUSS algorithm successfully solves the compressed sensing problem even for less sparse cardiac cine applications. Therefore, using k-t FOCUSS, very accurate time resolved contrast enhanced MR angiography can be reconstructed. Accelerated radial trajectory data were synthetized from X-ray cerebral angiography images and provided by the organizing committee, and radiologists double blindly evaluated each reconstruction result with respect to the ground-truth data. Results : The reconstructed results at various acceleration factors demonstrate that each components of compressed sensing, such as sparsifying transform and incoherent sampling patterns, etc can have profound effects on the final reconstruction results. Conclusion : From reconstructed results, we see that the compressed sensing dynamic MR imaging algorithm, k-t FOCUSS enables high resolution time resolved contrast enhanced MR angiography.