Evaluation of the Somatotopic Organization of Corticospinal Tracts in the Internal Capsule and Cerebral Peduncle: Results of Diffusion-Tensor MR Tractography

OBJECTIVE: We have used diffusion tensor tractography (DTT) for the evaluation of the somatotopic organization of corticospinal tracts (CSTs) in the posterior limb of the internal capsule (PLIC) and cerebral peduncle (CP). MATERIALS AND METHODS: We imaged the brains of nine healthy right-handed subjects. We used a spin-echo echo-planar imaging (EPI) sequence with 12 diffusion-sensitized directions. DTT was calculated with an angular threshold of 35 degrees and a fractional anistropy (FA) threshold of 0.25. We determined the location of the CSTs by using two regions of interest (ROI) at expected areas of the pons and expected areas of the lateral half of the PLIC, in the left hemisphere of the brain. Fiber tracts crossing these two ROIs and the precentral gyrus (PCG) were defined as CSTs. Four new ROIs were then defined for the PCG, from the medial to lateral direction, as ROI 1 (medial) to ROI 4 (lateral). Finally, we defined each fiber tract of the CSTs between the pons and each ROI in the PCG by using two ROIs methods. RESULTS: In all subjects, the CSTs were organized along the long axis of the PLIC, and the hand fibers were located anterior to the foot fibers. The CSTs showed transverse orientation in the CP, and the hand fibers were located usually medial to the foot fibers. CONCLUSION: Corticospinal tracts are organized along the long axis of the PLIC and the horizontal direction of the CP.

The Usefulness of the 3-D Overlapped Reconstruction MR Angiographic Technique in Patients with Hemifacial Spasm - A Preliminary Study

PURPOSE: To investigate the applicability of the new three-dimensional overlapped reconstruction MR angiography (3-D ORMRA) technique in patients with hemifacial spasm and to compare the new 3-D reconstruction images with conventional MRA source images. MATERIALS AND METHODS: The study group comprised 27 patients with surgically proven hemifacial spasm. In all patients, conventional MRA source images and 3-D fast imaging employing steady-state acquisition (FIESTA) images were obtained prospectively. After 3-D MR angiographic images were obtained, the 3-D MRA and FIESTA images were overlapped at the workstation by using GE A/W 4.2 add/sub software. We analyzed the relationship between the offending vessels and root exit zone of the facial nerve using both 3-D ORMRA images and conventional MRA source images. RESULTS: In 25 of 27 patients, the offending vessel at the REZ of the facial nerve could be correctly identified on conventional MRA source images. In all patients, the presumed offending vessels depicted by the overlapped 3-D reconstruction MRA image corresponded well with the intraoperative findings. The 3-D reconstruction image showed more clear visualization of the spatial relationship between the offending vessels and the root exit zone of the facial nerve. CONCLUSION: The overlapped 3-D reconstruction MR angiography technique is very useful and informative in patients with hemifacial spasm, as compared with conventional MRA angiography technique.

Perfusion Imaging of the Brain Using Z-Score and Dynamic Images Obtained by Subtracting Images from before and after Contrast Injection

OBJECTIVE: The aim of this study was to examine the feasibility of perfusion imaging of the brain using the Z-score and subtraction dynamic images obtained from susceptibility contrast MR images. MATERIALS AND METHODS: Five patients, each with a normal MRI, Moya-moya, a middle cerebral artery occlusion, post-trauma syndrome, and a metastatic brain tumor, were selected for a presentation. A susceptibility-contrast echo-planar image after a routine MRI was taken as the source image with a rapid manual injection of 0.1 mmol/kg of Gd-DTPA. The inflow and washout patterns were observed from the time-signal intensity curve of the serial scans using the standard program of an MRI machine. The repeated Z-score images of the peak and late phases were made using the threshold Z-score values between 1.4 and 2.0 in four to five studies of the pre-contrast, peak, and late phases. Dynamic subtraction images were produced by subtracting sequential post-contrast images from a pre-contrast image and coloring these images using a pseudocolor mapping method. RESULTS: In the diseases with perfusion abnormalities, the Z-score images revealed information about the degree of perfusion during the peak and late phases. However, the quality varied with the Z-score threshold and the studies selected in a group. The dynamic subtraction images were of sufficient quality with no background noise and more clearly illustrated the temporal changes in perfusion and delayed perfusion. CONCLUSION: The Z-scores and dynamic subtraction images illustrated the degree of perfusion and sequential changes in the pattern of perfusion, respectively. These images can be used as a new complimentary method for observing the perfusion patterns in brain diseases.

Postcontrast T1-weighted Brain Magnetic Resonance Imaging in Pediatric Patients: Comparison Between Postcontrast Fat-suppression Imaging and Conventional T1-weighted or Magnetization Transfer Imaging

PURPOSE: We wished to assess the merits and weaknesses of postcontrast fat-suppression (FS) brain MR imaging in children for the evaluation of various enhancing lesions as compared with postcontrast conventional T1-weighted or magnetization transfer (MT) imaging. MATERIALS AND METHODS: We reviewed the records of those patients with enhancing lesions on brain MR imaging who had undergone both FS imaging and one of the conventional T1-weighted or MT imaging as a postcontrast T1-weighted brain MR imaging. Thirty-one patients (21 male, 10 female; mean age, 8.7 years) with 38 enhancing lesions (18 intra-axial, 16 extra-axial and 4 orbital locations) were included in this study. There were 27 pairs of FS and conventional imagings, and 13 pairs of FS and MT imagings available for evaluation. Two radiologists visually assessed by consensus the lesions' conspicuity, and they also looked for the presence of flow or susceptibility artifacts in a total of 40 pairs of MR imagings. For 19 measurable lesions (14 pairs of FS and conventional T1-weighted imagings, 5 pairs of FS and MT imagings), the contrast ratios between the lesion and the normal brain ([SIlesion-SIwater]/[SInormal brain-SIwater]) were calculated and compared. RESULTS: Compared with conventional imaging, the lesion conspicuity on FS imaging was better in 10 cases (7 extra-axial lesions, 2 orbital lesions and 1 fat-containing intra-axial lesion), equal in 16 cases, and worse in one case. Compared with MT imaging, the lesion conspicuity on FS imaging was better in 3 cases (2 extra-axial lesions and 1 intra-axial lesion), equal in 8 cases, and worse in 2 cases. Image quality of FS imaging was compromised by flow or susceptibility artifacts for 7 patients. The contrast ratios for FS imaging were not significantly different from those for conventional imaging (2.2+/-0.7 vs. 2.2+/-0.6, respectively, p=0.914) and they were significantly lower than those for MT imaging (2.4+/-0.8 vs. 4.5+/-1.5, respectively, p=0.018). CONCLUSION:Postcontrast FS brain MR imaging appears to be better than the conventional T1-weighted imaging and comparable to MT imaging for the visual assessment of enhancing lesions. Especially, the FS imaging has the merit to delineate orbital and extra-axial enhancing lesions or fat-containing lesions, whereas it is disadvantageous when flow or susceptibility artifacts occur.

Oblique Coronal MRI in the Evaluation of Bony Stenosis of the Cervical Foramina: Objectiveness and Correlation with Radiograph

PURPOSE: To determine the utility of oblique coronal MR (OMR) imaging in the evaluation of bony foraminal narrowing of the cervical spine by comparison of its findings with those of combined axial and sagittal MR (CMR) imaging and correlation with the findings of oblique radiography. MATERIALS AND METHODS: One hundred and eight cervical neural foramina in 18 patients formed the basis of this study. Three radiologists working in a blind fashion independently graded the degree of bony narrowing of the foramina seen on OMR and CMR images and on oblique radiographs (0=none, 1=stenosis below 25% of AP dimension, 2=stenosis exceeding 25% of AP dimension). Inter-observer variance was measured for each modality, and for each of these and for each foramen, consensus was reached as to whether of CMR or OMR showed better correlation with radiographs. RESULTS: Inter-observer variance in OMR was less (kappa=0.88) than in CMR (kappa=0.41). Correlation between the findings of OMR and radiography was also better (kappa=0.63) than between those of CMR and radiography (kappa=0.41). CONCLUSION: OMR can be a useful supplement in evaluating foraminal stenosis, especially when oblique radiographs and CMR images show discrepancies.

The Usefulness of T2-weighted MR Urography and Contrast Enhanced MR Urography in the Evaluation of Obstructive Uropathy: Comparisonal Study with Antegrade Pyelography1

PURPOSE: To compare the efficacy of contrast-enhanced and T2-weighted magnetic resonance urography (MRU) for the depiction of obstruction and evaluation of the causes of obstructive uropathy with that of antegrade pyelography. MATERIALS AND METHODS: Twenty-five patients with obstructive uropathy who underwent percutaneous nephrostomy (PCN) and antegrade pyelography (AGP) were included in the study. We performed MR urography, comprising half-Fourier acquisition single-shot turbo spin-echo (HASTE) T2-weighted imaging and 3-D fast imaging with steady state precession (3-D FISP) T1-weighted imaging after gadolinium enhancement and compared the quality of the images of both the HASTE and 3-D FISP MRU techniques in terms of their depiction of the dilated pelvocalyceal system, and the level, type, and causes of obstruction. RESULTS: In terms of anatomical depiction of the pelvocalyceal system (p=0.002) and the causes of obstruction (p=0.003), T1-weighted MRU using 3D-FISP was significantly better than T2-weighted MRU using the HASTE sequence. Regarding level of obstruction, T2-weighted MRU using the HASTE sequence and contrastenhanced T1-weighted MRU using 3D-FISP showed an accuracy of 76% (19/25) and 84% (21/25), respectively. In terms of type of obstruction, the accuracy of T2-weighted MRU and T1-weighted CEMRU was 72%(18/25) and 88% (22/25), respectively. CONCLUSION: T2-weighted MRU and T1-weighted CEMRU provided both anatomical information and that relating to impaired renal function. The two modelities played a complementary role and their use could decrease the unnecessary use of invasive diagnostic examination for the evaluation of obstructive uropathy.

MR Findings of Acute Graft-versus-Host Disease Involving Gastrointestinal Tracts

PURPOSE: To evaluate the MR findings of gastrointestinal graft-versus-host disease (GVHD) after allogenic bone marrow transplantation. MATERIALS AND METHODS: Five patients (M:F=3:2, age range: 9-58 years) with suspected gastrointestinal GVHD underwent abdominal MRI, and the findings were evaluated. Because of acute myelocytic leukemia (n=4) or non-Hodgkin's lymphoma (n=1), all had undergone allogenic bone marrow transplantation 2-6 (mean, 3.5) weeks earlier. T2-weighted half-Fourier acquisition snapshot turbo spin-echo, T1-weighted spoiled gradientecho (SGE), and postcontrast T1-weighted SGE MR imaging, with and without fat-suppression, was performed. RESULTS: All five patients showed bowel wall thickening and marked contrast enhancement in the jejunum (n=5), ileum (n=4), duodenum (n=3), sigmoid colon (n=3), gastric antrum (n=2), and rectum (n=2). Bowel wall thickening showed a target appearance in the jejunum (n=2, 40.0%), ileum (n=1, 25.0%), sigmoid colon (n=1, 33.3%), and rectum (n=1, 50.0%), while the remaining cases showed diffuse wall thickening without layering. Small amount of ascites was noted in four patients (80%), and multiple small conglomerated retroperitoneal lymph nodes in three (60%). In all patients, a signal intensity of slightly enlarged liver due to iron overload secondary to multiple blood transfusions, gave rise to decreased signal intensity at both T1-and T2-weighted MR imaging. CONCLUSION: In patients with GVHD, the commonly noted MR findings were bowel wall thickening with contrast enhancement, ascites and retroperitoneal lymphadenopathy.

Drug-induced MR Urography: The effects of Furosemide and Intravenous Saline Injection on MR Urography of Obstructed and Non-obstructed Urinary Tract

PURPOSE: To determine the usefulness of MR urography technique for the evaluation of urinary systems in patients with obstructed urinary tract and normal volunteers with non-obstructed urinary tract after intravenous normal saline and diuretic injection. MATERIALS AND METHODS: Three normal volunteers and 12 patients with urinary tract obstruction [ureteral calculi(n=8), extraurinary mass(n=1), ureteral tumor invasion(n=3)] underwent MR urography using a 1.0T scanner and a 2D non-breath-hold heavily T2-weighted fast spin-echo sequence. These acquisition were postprocessed with a maximum intensity projection (MIP) algorithm. Two acquisitions were performed, the first prior to saline solution infusion following standard MR urography procedures, and the second, within 2-3 minutes of the infusion of 250 ml saline solution followed by 20 mg of Lasix administered intravenously. For this latter, drug-induced MR urography procedures were followed. RESULTS: In healthy volunteers (n=3) and those experiencing partial obstruction (n=4) by a urinary stone, drug-induced MR urography provided better images of the urinary tract than did standard MR urography. In those in whom a urinary stone or tumor had caused complete obstruction (n=8), standard MR urography provided good images, as did drug-induced MR urography. CONCLUSION: In patients with a partially or non-obstructed urinary tract, drug-induced MR urography provided better anatomic and functional details of the kidney and urinary tract than did standard MR urography. In those experiencing complete obstruction of the urinary tract, however, standard or drug-induced MR urography permitted very adequate evaluation of the tract, and drug-induced MR urography was unnecessary.

FLAIR MR Imaging in the Detection of Subarachnoid Hemorrhage: Comparison with CT and T1-Weighted MR Imaging

PURPOSE: 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. MATERIALS AND METHODS: 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 24hours(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). RESULTS: 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), re-spectively. FLAIR was superior to T1-weighted imaging in the detection of SAH at all sites except the anterior basal cistern (p<0.05) and superior to CT in the detection of SAH at the cortical sulci(p<0.05). CONCLUSION: 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.

Determination of Language Dominance Using Functional MRI in Patients with Intractable Seizure: Comparison with Wada Test

PURPOSE: To investigate the efficiency or potency of functional MRI (fMRI) for the determination of language dominance by comparing the results of fMRI with those of the Wada test. MATERIALS AND METHODS: Among 34 patients with intractable seizure who underwent both fMRI and the Wada test, we analyzed the results of 30 (men:women=19:11; mean age=29.7 years). Using echoplanar imaging and the blood oxygen level dependent technique, fMRI was performed using a 1.5 T MR imager with a standard head coil. The language task consisted of two parts: reading words and generating words. For fMRI, a multi-event multi-task paradigm consisting of two sets of activation, rest, and alternative periods was used. Image processing involved the use of the Z test (Z threshold = 1.0 -1.2). To determine the lateralization index, we calculated the activation pixels within the whole frontal cortex., and to ascertain the discrepancy between the two tasks, the clustering grade of activation pixels was measured. After the injection of thiopental, language dominance was determined by means of a modified Wada test. The results of this and the findings of fMRI were compared with the results of Fisher 's exact test (p 0.05). CONCLUSION: For the determinaton of language dominance, fMRI showed good correlation with the Wada test. The word generation task was more efficient than the reading task. fMRI which is non-invasive and repeatable, is therefore more efficient and useful than the invasive Wada test.

Usefulness of 3D CISS Sequence in MR Imaging of Cervical Spine

PURPOSE: To assess the value of 3D CISS (constructive interference in steady state) MR sequence in imaging the cervical spine. MATERIALS AND METHODS: MR images of cervical spine were prospectively obtained with both conventional (sagittal TSE and axial 2D FLASH) and CISS sequences in 20 patients suspected of having cervical spinal diseases. MR technique was performed on a 1.5T MR machine. Axial, oblique coronal, and curved coronal images were reformatted with the 3D raw datas of CISS sequence which were obtained in cornal plane. The findings of CISS sequence were compared with those of the conventional sequence in terms of visualization of the neural foramen and nerve roots, detection and differentiation of herniated disc, conspicuity of the intramedullary lesion, contrast between the CSF and spinal cord and between the gray and white matters within the cord. RESULTS: In 17 cases including traumatic root avulsions, 3D CISS sequence demonstrated the intradural nerve roots with excellent contrast especially in coronal plane. Reformatted oblique coronal images of CISS sequence offered better visualization of entire neural foramen beyond the region of interest. CISS sequence was superior to the conventional sequence in demonstration of disease extent and correlation to the clinical symptoms in 4.5 cases of foraminal stenosis and in contrast between the CSF and spinal cord (n=15). CISS sequence was almost equal to the conventional sequence in detection of herniated disc (n=15). CISS was inferior to the conventional sequence in differentiation of herniated disc (n=7), delineation of intramedullary lesion (n=4) and in contrast between the gray and white matter within the cord in all patients. CONCLUSION: The 3D CISS sequence gives better information than the conventional sequence especially in the evaluation of the nerve roots and neural foramens but worse contrast of intramedullary lesion. It may well be used as a supplementary sequence in assessment of foraminal stenosis and nerve root injury.

A Study on the Activation of Supplementary Motor Area in Functional Magnetic Resonance Imaging of the Brain

PURPOSE: To evaluate the activated zone of the supplementary motor area through motor and sensorystimula-tion of both hands by fMRI. MATERIALS AND METHODS: Twenty-four healthy volunteers, ranging in age from 20to 30 years, served as sub-jects. They were divided into four groups and performed one of the four activationtasks : complex movement, fine movement, touch sensation, heat sensation. Complex movement consisted of a fingertask in which sub-jects flexed and extended all fingers repeatedly in union, without the fingers touching eachother(group I). Fine movement involved a thumb task in which subjects flexed and extended the thumb repeatedlywithout touch-ing the other fingers(group II). Touch sensation consisted of a palm task in which another personrepeatedly drew a circle on the subject 's palm (group III), and heat sensation involved of a palm task in whichsubject 's palm was touched by another person with a 40 degreeC water-bag (group IV). F-MRI was conducted on acommer-cial 1.5-T scanner equipped with echo-planar imaging. After overlapping images were obtained using aZ-s-core, and the mean/curve in the MR devices was evaluated, the activated zone of the supplementary motor RESULTS: Thirty-two of 48 images(20 of the 24 men) revealed activated zones in the supplementary motor area. Ingroup I, activation was observed in five subjects, in three of whom it was bilateral (contralateral activation).In group II, activation was observed in five subjects, in one of whom it was bilateral. In group III, activationoccurred in five subjects(bilateral in four, and contralateral in three), and In group IV, activation was alsoob-served in five ; in three of these it was bilateral. CONCLUSION: Using fMRI, and in association with motor andsensory tasks, the supplementary motor area was activated in 66.7% of healthy volunteers (32/48).

MR Urography Using HASTE Imaging: Comparison with Intravenous Urography

PURPOSE: To evaluate the usefulness of MR urography(MRU) using Half-Fourier acquisition single-shot turbospin-echo(HASTE) sequence compared with conventional intravenous urography(IVU). MATERIALS AND METHODS: Thirtyfive lesions of 32 patients who underwent MRU because of delayed excretion or nonvisualization of the ureter wereincluded in this study. HASTE MR urography was performed with a 1.0 MR imaging unit. Coronal images includingthose of the kidney, ureter and bladder were obtained in every patient using the multislice technique, and werepostprocessed by means of the maximal intensity projection technique. Scan time was 17-19 seconds. We analyzed theresults of MRU, focusing on level of obstruction, incidence of stone, ureter dilatation, and motion artifact, andin each case compared MRU findings with those of IVU. RESULTS: In 12 of 35 lesions(34.2%), MRU more effectivelydiagnosed causes of obstruction than did IVU, while in seven lesions(20%), MRU and IVU were similar. In eightlesions(22.9%), all of which were caused by a stone, IVU was better than MRU, and in a further eight, neithermodality was able to diagnose the cause. For diagnosis of the level of obstruction, MRU was better than IVU in 20of 35 lesions(57.1%), and similar to IVU in seven(20%). In three lesions(8.6%), neither modality was able todetect the level of obstruction. Four lesions not related to obstruction were polycystic renal disease, cysticrenal change, vesicovaginal fistula and extra-renal pelvis. Dilatation of the ureter was seen in 23lesions(65.8%) on MRU and in seven lesions on IVU. Thus, MRU revealed dilatation of for the ureter more efectivelythan IVU. CONCLUSION: MRU using HASTE was valuable for the detection of underlying causes and levels ofobstruction in the urinary tract, and of abnormalities in surrounding structures in patients with non-visualization of the kidney or delayed contrast excretion of the ureter, as seen on delayed IVU urogram.

MR Imaging of Portal System: Comparison between True-Fast Imaging with Steady State Precession(FISP) and Enhanced Fast Low Angle Shot(FLASH) Imaging

PURPOSE: The purpose of this study was to compare true-fast imaging with steady state precession(t-FISP) with enhanced fast low-angle shot(e-FLASH) imaging of the abdomen in the assessment of the normal and abnormal portal venous(PV) system. MATERIALS AND METHODS: In order to evaluate the PV system, MR images using both t-FISP and e-FLASH sequences were obtained in 62 patients with hepatic mass. In 56 cases in which PV thrombosis was not demonstrated, images were evaluated for homogenity and artifacts within the lumen of the PV system and the margin of the main PV. In the other six cases of PV thrombosis, conspicuity and extent of the thrombus were also compared . RESULTS: For each vessel, the mean score for homogeneity and artifacts was significantly higher in t-FISP images than in e-FLASH images(P<.05), as were mean scores for the margin of the main PV (P < .05). In six patients with PV thrombosis, conspicuity of the thrombus as seen on t-FISP images was superior to that seen on e-FLASH images; similarly, the exact extent of the thrombus was more accurately defined on the former type of image. CONCLUSION: For evaluation of the PV system, t-FISP MRI provides better imaging quality and better conspicuity with regarded to the site and extent of PV thrombus, as compared with e-FLASH images.

MR Imaging of Portal System: Comparison between True-Fast Imaging with Steady State Precession(FISP) and Enhanced Fast Low Angle Shot(FLASH) Imaging

PURPOSE: The purpose of this study was to compare true-fast imaging with steady state precession(t-FISP) with enhanced fast low-angle shot(e-FLASH) imaging of the abdomen in the assessment of the normal and abnormal portal venous(PV) system. MATERIALS AND METHODS: In order to evaluate the PV system, MR images using both t-FISP and e-FLASH sequences were obtained in 62 patients with hepatic mass. In 56 cases in which PV thrombosis was not demonstrated, images were evaluated for homogenity and artifacts within the lumen of the PV system and the margin of the main PV. In the other six cases of PV thrombosis, conspicuity and extent of the thrombus were also compared . RESULTS: For each vessel, the mean score for homogeneity and artifacts was significantly higher in t-FISP images than in e-FLASH images(P<.05), as were mean scores for the margin of the main PV (P < .05). In six patients with PV thrombosis, conspicuity of the thrombus as seen on t-FISP images was superior to that seen on e-FLASH images; similarly, the exact extent of the thrombus was more accurately defined on the former type of image. CONCLUSION: For evaluation of the PV system, t-FISP MRI provides better imaging quality and better conspicuity with regarded to the site and extent of PV thrombus, as compared with e-FLASH images.

Comparison of ADC Map with Trace Map in the Normal and Infarct Areas of the Brains of Stro ke Patients

PURPOSE: To compare ADC mapping with trace mapping in normal and infarct areas of the brains of strokepatients. MATERIALS AND METHODS: Eighteen patients diagnosed on the basis of clinical and brain MRI examinationsas suffering from brain infarction were included in this study (hyperacute-1, acute-4, subacute-12, chronic-1).Diffusion weighted images of three orthogonal directions of a patient's brain were obtained by means of a singleshot EPI pulse sequence, using a diffusion gradient with four serial b-factors. Three ADC maps were thenreconstructed by post-image processing and were summed pixel by pixel to yield a trace map. ROIs were selected inthe normal areas of white matter, gray matter and CSF of one hemisphere, and other ROIs of the same size wereselected at the same site of the contralateral hemisphere. ADC and trace values were measured and right/leftratios of ADC and trace values were calculated. Using these values, we then compared the ADC map with the tracemap, and compared the degree of anisotropic diffusion between white matter, gray matter and CSF. Except for three,whose infarct lesions were small and lay over white and gray matter, patients were divided into two groups. Thosewith infarct in the white matter (n=10)were assigned to one group, and those with in-farct in the gray matter(n=5) to the other. ROIs were selected in the infarct area and other ROIs of the same size were selected at thesame site of the contralateral hemisphere. ADC and trace values were measured and infarct/contralateral ratioswere calculated. We then compared ADC ratio with trace ratio in white matter and gray matter infarct. RESULTS: Innormal white matter, the Dxx ratio was 0.980 +/-0.098, the Dyy ratio 1.019 +/-0.086, the Dzz ratio 0.999 +/-0.111,and the trace ratio 0.995 +/-0.031. In normal gray matter, the Dxx ratio was 1.001 +/-0 . 0 5 8 , the Dyy ratio0.996 +/-0.063, Dzz ratio 1.005 +/-0.070, and the trace ratio 1.001 +/-0.028. In CSF, the Dxx ratio was 1.002+/-0.064, the Dyy ratio 1.023 +/-0.055, the Dzz ratio 0.999 +/-0.060 and the trace ratio 1.007 +/-0 . 0 2 1. Becausethe standard deviation of trace ratios (0.05), the trace ratio is moreaccurate representative value. The standard deviation of white matter is greater than that of gray matter or CSF(p<0.05), the degree of anisotropic diffusion in white matter is therefore more severe than in gray matter andCSF. The difference between the ADC ratios and trace ratio is greater in an infarct involving white matter than inone involving gray matter (p<0.05). CONCLUSION: Because a trace map overcomes the anisotropic diffusions of ADCmaps, the former offers better post-image processing. The deviation of ADC ratios owing to the direction ofdiffusion gradient is greater in white matter than in gray matter, and the trace map is thus superior forevaluation of an infarct involving white matter.

CISS MR Imaging Findings of Epidermoid Tumor: Comparison with Spin-Echo Images

PURPOSE: To evaluate CISS MR imaging findings of epidermoid tumor in comparison with conventional spin-echoimages. MATERIALS AND METHODS: We studied 6 cases of epidermoid tumor in the subarachnoid space. We used a 1.5TMR unit to obtain CISS images(TR/TE/FA ; 12.3msec/5.9 msec/700) and T1- and T2-weighted spin-echo images. CISS MRimaging findings were evaluated with respect to tumor's signal intensity, contour, and relation with adjacentstructures. Conspicuity of the tumor was compared between CISS and spin-echo images. A quantitative analysis wasperformed by measuring tumor to CSF contrast. In qualitative analysis, three radiologists independently comparedCISS image and conventional spin-echo images for visibility of the tumor and graded them into three categories(poor, good, and excellent). RESULTS: Epidermoid tumors were located in the cerebellopontine angle in 4 cases, theprepontine cisstern in 1 case, and the cerebellopontine angle-prepontine cistern in 1 case. The tumors werehyperintense relative to brain parenchyma and hypointense relative to CSF on CISS images, were lobulated, encasedadjacent cranial nerve and vessels, and invaginated into brain parenchyma. In qualitative analysis, CISS imagesshowed clear demarcation between tumor and CSF, exact tumor extension, and tumor's relation with cranial nervesand vessels better than conventional spin-echo images. In quantitative analysis, the mean contrast values of tumorto CSF on T1-, T2-weighted images, and CISS images were 0.12, 0.06, and 0.52, respectively. The contrast value forCISS images was significantly higher than that for T1- and T2-weighted images (P<0.05) . CONCLUSIONS: Epidermoid tumors in the subarachnoid space are better demonstrated on CISS images than on conventional spin-echoimages. This special MR sequence can be added as a routine protocol in the diagnosis of subarachnoid epidermoidtumor.

Diagnostic Value of MR Imaging in Differentiation of Meniscal Tear Patterns

PURPOSE: To evaluate the diagnostic accuracy of magnetic resonance (MR) imaging in the differentiation ofmeniscal tear patterns of the knee. MATERIALS AND METHODS: MR images of 93 patients with meniscal tear wereincluded in this study. On the basis of arthroscopic findings, the configuration of meniscal tears was classifiedas horizontal (n=44), longitudinal (n=34), transverse (n=11), or oblique (n=5). Oblique sagittal and coronal MRimages were obtained and com-pared with the arthroscopic findings. RESULTS: Among 94 cases ofarthroscopically-proven meniscal tears, 35 of 44 horizontal and 27 of 34 longitudi-nal configurations werecorrectly interpreted on MR images. Sensitivity and specificity for horizontal configu-ration were 80 % and 80 %,respectively, while the corresponding values for longitudinal configuration were 79 % and 95 %. On MR images, tworadial configurations were correctly interpreted from 11 confirmed tears and only one oblique configuration fromfive confirmed tears. CONCLUSION: MR imaging was useful for the differentiation of horizontal and longitudinaltears, but inaccurate in cases involving radial or oblique tears.

Abdominal MR Imaging Using a HASTE Sequence: Image Comparison on the Different Echo Times

PURPOSE: To determine the optimal parameters of abdominal HASTE imaging by means of a comparison of intermediate and long TE (echo time). MATERIALS AND METHODS: We evaluated 30 consecutive patients who had undergone liver MR during a three-month period. Twelve patients were diagnosed as normal, four as having liver cirrhosis, and 14 were found to be suffering form hepatic hemangioma. On the basis of measured signal intensity of the liver, spleen, pancreas and gallbladder, and of fat, muscle, hemangioma, and background, we calculated the ratios of signal to noise (S/N), signal difference to noise (SD/N), and signal intensity (SI). Image quality was compared using these three ratios, and using two HASTE sequences with TEs of 90 msec and 134 msec, images were qualitatively evaluated. RESULTS: S/N ratio of the liver was higher when TE was 90 msec(p<.05), though S/N, SD/N and SI rations of the spleen, gallbladder, and pancreas -and of hemangiom- were higher when TE was 134 msec (p<.05). However, in muscle, all these three ratios were higher at a TE of 90 msec. SD/N ratio and SI of fat were higher at a TE of 134 msec. Overall image quality was better at a TE of 134mesc than at one of 90msec. CONCLUSION: A HASTE sequence with a TE of 134msec showed greater tissue contrast and stronger T2-weighted images than one with a TE of 90msec.

MR Imaging of Focal Hepatic Masses: Comparison between Half-Fourier Acquisition Single-shot TSE(HASTE) andSingle-shot Echo Planar Imaging

PURPOSE: We undertook this study to evaluate breath-hold Half-Fourier Acquisition Single-shot TSE(HASTE) andsingle-shot echo planar MR imaging for the detection of focal hepatic masses. MATERIALS AND METHODS: Using a 1.5Tsuperconductive system, HASTE, vascular dephasing inversion recovery spin echo EP(VDIR-SE-EP), inversion recoveryspin echo EP(IR-SE-EP), and free induction decay EP(FID-EP) were performed in 31 patients with 34 focal livermasses. Images were compared on the basis of detection sensitivity of focal hepatic masses, liver signal-to-noiseratio(S/N), lesion-to-liver contrast-to-noise ratio(C/N), and image quality. Images analysis was performed by tworadiologists, who reached a consensus. RESULT: The detection sensitivity of focal hepatic masses with HASTE was94.1%, with VDIR-SE-EP and IR-SE-EP, this was 91.2%, and with FID-EP, the figure was 88.2%. Liver S/Ns werehighest on HASTE images, which were significantly better(p<.05) than the three types of EP image. Overalllesion-to-liver C/Ns were highest on VDIR-SE-EP and IR-SE-EP(p<.05). Lesion-to-liver C/Ns were highest onVDIR-SE-EP and IR-SE-EP for solid lesions, but for non-solid lesions, were highest on HASTE (p<.05). Compared withHASTE images, EP images were poor. CONCLUSION: For the detection of focal hepatic masses, the sensitivity ofVDIR-SE-EP and IR-SE-EP was similar to that of HASTE. When using the former, acquisition time was substantiallyreduced but image quality was poor.