Functional MRI of Language: Difference of its Activated Areas and Lateralization according to the Input Modality

PURPOSE: To compare fMRIs of visual and auditory word generation tasks, and to evaluate the difference of its activated areas and lateralization according to the mode of stimuli. MATERIALS AND METHODS: Eight male normal volunteers were included and all were right handed. Functional maps were obtained during auditory and visual word generation tasks in all. Normalized group analysis were performed in each task and the threshold for significance was set at p<0.05. Activated areas in each task were compared visually and statistically. RESULTS: In both tasks, left dominant activations were demonstrated and were more lateralized in visual task. Both frontal lobes (Broca's area, premotor area, and SMA) and left posterior middle temporal gyrus were activated in both tasks. Extensive bilateral temporal activations were noted in auditory task. Both occipital and parietal activations were demonstrated in visual task. CONCLUSION: Modality independent areas could be interpreted as a core area of language function. Modality specific areas may be associated with processing of stimuli. Visual task induced more lateralized activation and could be a more useful in language study than auditory task.

The Comparison of Usefulness between MDCT Angiography and DSA in the Diagnosis of Intracranial Aneurysm / 의학물리

The purpose of this study was to compare the image between DSA and MDCT Angiography and to examine whether MDCT Angiography could be useful as a screening test for the diagnosis of cerebral aneurysm in patients who were diagnosed with cerebral aneurysm on DSA. Of patients who were diagnosed with cerebral aneurysm DSA at University Hospital, 194 patients who concomitantly underwent MDCT Angiography were enrolled in the current retrospective study. The methods for analyzing cerebral aneurysm were to analyze the presence of cerebral aneurysm on DSA and MDCT Angiography. In cases in which it exceeded 1, the corresponding cases were classified as narrow-neck aneurysms. In otherwise cases, they were classified as wide-neck aneurysms. Thus, a comparative analysis could be performed to ascertain if cases were narrow-neck or wide-neck aneurysms. As compared with DSA, the sensitivity of MDCT Angiography for cerebral aneurysm was measured to be 97.4%. The degree of consistency between narrow-neck and wide-neck aneurysms was 90.2% and the proportion of undetectable an at MDCT Angiography was 2.54%. mean size was 2.4 mm. It is expected that a non-invasive diagnostic modality for a screening test for cerebral aneurysm, MDCT Angiography might be a very useful regimen as compared with an invasive one, DSA.

Comparison of Diffusion Tensor Imaging in Attention Deficit Hyperactivity Disorder Boys with or without Comorbid Tic Disorders / 신경정신의학

OBJECTIVES: Diffuse tensor imaging (DTI) was applied to explore the difference in regional distribution and extent of white matter (WM) abnormalities in boys with Attention-deficit/hyperactivity disorder (ADHD) versus boys with comorbid ADHD and tic disorders. METHODS: Fifteen boys with ADHD (mean age 9.3+/-1.8), 24 ADHD boys with chronic tic disorder or Tourette's disorder (9.9+/-1.2) and 9 age-, gender-matched controls (9.2+/-1.8) received DTI assessments. Fractional Anisotropy (FA) maps of WM were compared between groups with a voxel-wise analysis after intersubject registration to MNI space. RESULTS: Both groups, ADHD group and ADHD with tic disorder group, commonly showed decreased FA than healthy control group in left cerebellar middle peduncle and right frontal lobe, increased FA in right middle occipital WM. In the common areas of left cerebellar middle peduncle and right middle occipital WM, comorbid group showed broader areas of significant FA. The comorbid group also showed increased FA in right cerebellar peduncle, additionally. CONCLUSION: The findings in ADHD group support previous ADHD hypothesis of the functional abnormalities in corticocerebellar circuit, and suggest that ADHD might have more complicated pathology of neuronal circuit including occipital visual system. The comorbid group showed common areas of overlapping but more extensive abnormalities and also had additional WM abnormalities. ADHD with chronic tic disorders may represent a severe form of ADHD with additional regions of abnormal connectivity.

Assessment of Non-permeability of Gd-DTPA for Dynamic Susceptibility Contrast in Human Brain: A Preliminary Study Using Non-linear Curve Fitting

To develop an advanced non-linear curve fitting (NLCF) algorithm for performing dynamic susceptibility contrast study of the brain. The first pass effects give rise to spuriously high estimates of Ktrans for the voxels that represent the large vascular components. An explicit threshold value was used to reject voxels. The blood perfusion and volume estimation were accurately evaluated in the T2*-weighted dynamic contrast enhanced (DCE)-MR images. From each of the recalculated parameters, a perfusion weighted image was outlined by using the modified non-linear curve fitting algorithm. The present study demonstrated an improvement of an estimation of the kinetic parameters from the DCE T2*-weighted magnetic resonance imaging data with using contrast agents.

Development of MRI Phantom for Assessing MR Image Quality

PURPOSE : To evaluate MR image qualities we developed a new MRI phantom with the fixation structures necessary to position it into coil firmly. MATERIALS AND METHODS : We designed MRI phantom for eight evaluation items such as slice thickness accuracy, high contrast spatial resolution, low contrast object detectability, geometry accuracy, slice position accuracy, image intensity uniformity, percent signal ghosting and signal to noise ratio. For the positioning of phantom at coils, the fixation structures were set up on the surface of phantom. Six different MRI units were used for test the possibility for the clinical application and their image qualities were evaluated. RESULTS : We acquired appropriate MR image qualities enough for the evaluation on all used MR units and confirmed that their evaluations were within reliable values compared to real ones for some items. The positioning of our phantom into head coils with fixation structures worked well for proper imaging. CONCLUSION : We found that our prototype of MRI phantom had the possibility of clinical application for MR image quality assessment.