The Usefulness of 3T-TOF MR angiography in Patients with Cerebral Infarction

PURPOSE: This study was designed to evaluate the usefulness of 3T-TOF MR angiography (3T-TOF MRA) compared with transcranial Doppler sonography (TCD) and conventional angiography (CA) in patients with suspected cerebral infarction. MATERIALS AND METHODS: Fifty four patients with clinical symptoms of cerebral infarction were involved in this study, and had undergone 3T-TOF MRA and TCD, with CA in 11 patients. On the basis of divisions of the carotid artery, four groups were designated: group I, both vertebral arteries and basilar artery; group II, segment between 2 cm below bifurcation of common carotid artery and genu portion of internal carotid artery; group III, segment between petrous portion of internal carotid artery and bifurcation of anterior and middle cerebral artery; group IV, from bifurcation of anterior and middle cerebral artery to thier distal branches. Two radiologists retrospectively reviewed the vascular imaging and stenosis in 3T-TOF MRA, TCD, and CA. RESULTS: A total of 432 arteries, 108 in each group, were available. The assessment of vascular imaging quality in 3T-TOF MRA is scored 2.98, 2.96, 2.91, 2.88 in 4 groups, respectively. Agreement among 3TTOF MR angiography, TCD, and CA was high. CONCLUSION: 3T-TOF MR angiography may be useful method for the assessment of stenotic lesions of cranial vasculature in patients with cerebral infarction.

Contrast-Enhanced MR Angiography of Failing Hemodialysis Arteriovenous Fistulas and Grafts: A Preliminary Experience

PURPOSE: The purpose of this report is to evaluate the vascular stenosis for failing hemodialysis arteriovenous fistulas and grafts using contrast-enhanced MR imaging (CE-MRI) and to compare the results with digital subtraction angiography (DSA). MATERIALS AND METHODS: Nine patients (27 segmental vessels) with symptoms and signs of AVF stenosis or occlusion who presented to our medical department were recruited into this prospective comparative study. All of the patients with Brescia-Cimino arteriovenous fistula (AVF) or synthetic polytetrafluoroethylene (PTFE, Goretex(R)) loop graft underwent MRA and DSA of the fistula. MRA was performed with a 1.5-T system using VIBE sequence: TR/TE=3.5/1.5 msec, flip angle 20-25degrees, matrix 115x256, FOV 350x350, interpolated slice thickness 2.0 mm, fat suppression, scan time 13-18 sec and total time of 5 min. DSA was used as the reference standard for assessing the accuracy of MRA, and MRA was analyzed for the presence of stenosis or occlusion, a grading of stenosis, and the presence of collateral vessels. Two radiologists prospectively analyzed the MRAs by working in consensus. RESULTS: Regarding the stenotic grade, CE-MRA corresponded with the DSA in six patients (66.7%) and it overestimated the stenoses in three patients (33.3%). For the stenotic site, MRA had a sensitivity of 86.4%, a specificity of 40%, a positive predictive value of 32.1%, and a negative predictive value of 66.7%. CONCLUSION:Multiphase CE-MRA of the AVF noninvasively provided information comparable to that provided by DSA for the vascular stenosis regarding failing hemodialysis arteriovenous fistula.

Analysis of the Vertebral Venous System in Relation to Cerebral Venous Drainage on MR Angiography

PURPOSE: In the supine position, cerebral venous drainage occurs primarily through the internal jugular veins, as seen on venous phase cerebral angiography. However, in the erect position, the vertebral venous system represents the major alternative pathway of cerebral venous drainage, while outflow through the internal jugular veins is absent or negligible. The purpose of this study is to evaluate the vertebral venous system and its relationship between the surrounding venous structures using magnetic resonance angiography (MRA) in the case of subjects in the supine position. MATERIALS AND METHODS: We retrospectively reviewed the results of 65 patients (M:F=31:34, mean age: 61.6 years) who underwent multi-phase contrast-enhanced carotid MRA. The imaging studies were performed using a 3.0 T MR unit (TR: 5.2, TE: 1.1, FA: 20, 3.8 thickness, EC: 1). We analyzed the appearance and extent of the vertebral venous system (vertebral venous plexus and vertebral artery venous plexus) and the internal jugular vein on the venous phase images. We also evaluated the main drainage pattern of the cerebral venous drainage and the drainage pattern of the vertebral venous system. The visualized vertebral venous system was defined as either poor, vertebral venous plexus dominant, vertebral artery venous plexus dominant or mixed. RESULTS: In the vertebral venous system, the vertebral artery venous plexus was visualized in 54 cases (83%). The appearance of the visualized vertebral artery venous plexus was symmetrical in 39 cases (72%) and asymmetrical in 15 cases (28%). The extent of the visualized vertebral artery venous plexus was partial in 26 cases (48%) and complete in 28 cases (52 %). The vertebral venous plexus was visualized in 62 cases (95%). The appearance of the visualized vertebral artery venous plexus was symmetrical in 43 cases (69%) and asymmetrical in 19 cases (31%). The extent of the visualized vertebral artery venous plexus was partial in 35 cases (56%) and complete in 27 cases (44%). The appearance of the visualized internal jugular vein was asymmetrical in 44 cases (68%) and symmetrical in 21 cases (32%). Of these 44 asymmetrical cases, 4 demonstrated partial non-visualization of the internal jugular vein. In these 4 cases, the ipsilateral vertebral venous system was well visualized. The main cerebral venous drainage occurred through the internal jugular vein in 62 cases (97%) and the vertebral venous system in 2 cases (3%). The drainage pattern of the vertebral venous system was poor in 14 cases (21%), vertebral venous plexus dominant in 11 cases (17%), vertebral artery venous plexus dominant in 18 cases (28%) and mixed in 22 cases (34%). CONCLUSION: In the supine position, the vertebral venous system was well visualized. The vertebral venous system represented an alternative collateral pathway of the internal jugular vein in cerebral venous drainage. It may be that the vertebral venous system in used, or conversely the internal jugular vein, depending on the position of the subject.

Turnover in Intracranial Aneurysm Phantoms: Its Relation to Neck Size

PURPOSE: To evaluate the physiologic background of aneurysms poorly visualized during 3D-TOF MRA, contrast-enhanced MRA (CEMRA) and DSA due to hemodynamic isolation. MATERIALS AND METHODS: Using handmade elastic silicon phantoms to represent terminal basilar tip aneurysms, 3D-TOF MRA, CEMRA and DSA were used to determine blood turnover. Aneurysmal neck size was 2 mm and 10 mm, and the use of a pulsatile pump also helped recreate human physiologic parameters. We compared the results with those of computational fluid dynamics. RESULTS: DSA images of the narrow-necked aneurysm showed that a small volume of contrast medium washed into it during the systolic phase. As the width of its neck increased, the turnover volume of fragments of contrast bolus also increased. At CEMRA, the broad-necked aneurysm was visualized as the main bolus of Gd-DT PA passed through it, and at delayed CEMRA, the narrow-necked aneurysm was visualized faintly after the passage of bolus Gd-DT PA. The results correlated closely with those of 3DTOF MRA and computational fluid dynamics. CONCLUSION: The visualization of intracranial aneurysms at 3D-TOF MRA, CEMRA and DSA was greatly dependent upon blood turnover, which varied according to aneurismal neck size. A narrow-necked aneurysm might be missed at 3D-TOF MRA, CEMRA and DSA due to hemodynamic isolation.

Evaluation of the Pedal Artery: Comparison of Three-dimensional Gadolinium-Enhanced MR Angiography with Digital Subtraction Angiography

PURPOSE: To compare the three-dimensional gadolinium-enhanced MR angiography with digital subtraction angiography (DSA) for evaluation of the pedal artery. MATERIALS AND METHODS: In 12 extremities of 11 patients, both digital subtraction angiography (DSA) and contrast-enhanced MR angiography (CE-MR angiography) were performed during the same week. Among ten of the 11 patients, the following conditions were present: atherosclerosis (n=4), diabetic foot (n=3), Buerger's disease (n=1), calciphylactic arteriopathy (n=1) and arteriovenous malformation of the foot (n=1). The remaining patient underwent angiography prior to flap surgery. For MR angiography, a 1.5T system using an extremity or head coil was used. A three-dimensional FISP (fast imaging with steady state precession) sequence was obtained before enhancement, followed by four sequential acquisitions (scan time, 20 secs; scan interval time, 10 secs) 10 seconds after intravenous bolus injection of normal saline (total 10 cc), following intravenous adminstration of gadolinium (0.02 mmol/kg, 3 ml/sec). Arterial segments of the ankle and foot were classified as the anterior or posterior tibial artery, the distal peroneal artery, the medial or lateral plantar artery, the pedal arch, and the dorsalis pedis artery. Two radiologists independently analysed visualization of each arteraial segment and the mean of visible arterial segments in one extreminty using CE-MR angiography and DSA. RESULTS: Among 84 arterial segments, 16 were invisible at both CE-MR angiography and DSA, while 39 were demonstrated by both modalities. Twenty-six segments were visible only at CE-MR angiography and three only at DSA. CE-MR angiography displayed a higher number of arterial segments than DSA (mean, 5.42 vs. mean 3.50, respectively), a difference which was statistically significant (p<0.000). The difference between each arterial segment was not statistically significant, except for the dorsalis pedis artery (t test, p<0.000). CONCLUSION: In that it provides additional information for the planning of treatment of lower-extremity arterial disease, three-dimensional CE-MR angiography is superior to DSA for evaluation of the pedal artery.

Two-Dimensional Breath-Hold Coronary MR Angiography in Normal Adults

PURPOSE: To assess the efficacy of two-dimensional breath-hold coronary magnetic resonance angiography (coronary MRA) in normal rolunteers. MATERIALS AND METHODS: During a four-month period, 11 volunteers underwent MRA of the major coronary branches using a 2-D multiphase breath-hold spiral fast-gradient echo sequence. The proximal diameter of each visualized coronary artery was measured, and visibility and image quality were also determined. RESULTS: Adequate visualization was achieved in 82-100% of proximal coronary arterial branches and in 36-55% of the middle, distal branches. In general, the diameter of the proximal coronary artery correlated closely with that measured from conventional coronary angiography and using previous coronary MRA data. However, visibility and image quality in the left circumflex coronary artery were limited. CONCLUSION: In the majority of subjects, 2-D coronary MRA provides adequate visualization of the proximal segments of the major coronary arterial branches.

Usefulness of Three-dimensional Contrast-Enhanced MR Angiography in the Evaluation of Pelvic and Lower Extremity Arteries

PURPOSE: To evaluate the feasibility and clinical usefulness of three-dimensional contrast-enhanced MR angiography (3D-CE-MRA) as a screening test in the evaluation of pelvic and lower extremity arterial diseases. MATERIALS AND METHODS: Forty-four patients who underwent 3D-CE-MRA were included in this study. Coronal 3-dimensional gradient-echo, pre-and post contrast image were acquired with a dedicated peripheral vascular coil and moving-bed technique on a 1.5T MR system. Timing of start of data acquisition was determined by MR fluoroscopy technique, and 0.2mmol/kg Gd-DTPA was injected into an antecubital vein, at a rate of 1cc/sec with an autoinjector. For quantitative analysis, signal to noise ratio (SNR) and artery to soft tissue contrast to noise ratio (CNR) of lower extremities arterial system including lower abdominal aorta were calculated. For qualitative analysis, arterial systems were divided into six segments, and were evaluated in terms of conspicuity of arterial systems and the degree of venous enhancement by three- and four-point scale respectively. In eight patients who underwent both MR angiography and conventional angiography, the degree of the stenosis of MR angiography was compared with conventional angiography as standard reference. Imaging analysis was done by means of consensus between two experienced radiologists. RESULTS: The mean time for the examination was about 15min (+/-5 min). The mean SNR of arterial system was 26.5+/-11.6, and mean artery to soft tissue contrast to noise ratio (CNR) was 24.6+/-11.2. Among the total 525 arterial segments, 498 arterial segments (94.9%) could be demonstrated with good delineation of entire arterial tree. Good arterial imaging without or with minimal venous enhancement were demonstrated in 98.5% (260/264) in above knee and 89% (211/261) in below knee (p<0.01). Ten of 525 segments (1.9%) demonstrated severe venous overlapping and it mostly occurred in the calf region. In comparison with DSA, the sensitivity and the specificity for MR angiography for the detection of occlusions were 96% and 98,8%, respectively, and for the detection of more than 50% stenosis, 82.2% and 92.9%, respectively. CONCLUSION: 3D-CE-MRA provided adequate image for the evaluation of the lower extremity artery, and could be used as a screening test for arterial occlusive diseases.

Quantitatve Measurement of Total Cerebral Blood Flow Using 2D Phase-Contrast MRI and Doppler Ultrasound

PURPOSE: To compare of quantitative measurement of the total cerebral blood flow using two-dimensional phase-contrast MR imaging and Doppler ultrasound. MATERIALS AND METHODS: In 16 volunteers (mean age, 26 years; mean body weight, 66 kg) without abnormal medical histories, two-dimensional phase-contrast MR imaging was performed at the level of the C2-3 intervertebral disc for flow measurement of the internal carotid arteries and the vertebral arteries. Volume flow measurements using Doppler ultrasound were also performed at the internal carotid arteries 2 cm above the carotid bifurcation, and at the vertebral arteries at the level of the upper pole of the thyroid gland. Flows in the four vessels measured by the two methods were compared using Wilcoxon's correlation analysis and the median score. Total cerebral blood flows were calculated by summing these four vessel flows, and mean values for the 16 volunteers were calculated. RESULTS: Cerebral blood flows measured by 2-D phase-contrast MR imaging and Doppler ultrasounds were 233 and 239 ml/min in the right internal carotid artery, 250 and 248 ml/min in the left internal carotid artery, 62 and 56 ml/min in the right vertebral artery, and 83 and 68 ml/min in the left vertebral artery. Correlation coefficients of the blood flows determined by the two methods were 0.48, 0.54, 0.49, and 0.62 in each vessel, while total cerebral blood flows were 628+/-68 (range, 517 to 779) ml/min and 612+/-79 (range, 482 to 804)ml/min, respectively. CONCLUSION: Total cerebral blood flow was easily measured using 2-D phase-contrast MR imaging and Doppler ultrasound, and the two noninvasive methods can therefore be used clinically for the measurement of total cerebral blood flow.

The Usefulness of Three-Dimensional Gadolinium-Enhanced MR Venography for the Evaluation of Varices in Lower Extremities

PURPOSE: To assess the performance of contrast-enhanced three-dimensional(3-D) magnetic resonance venography (MRV) of the pelvis and lower extremities in patients with varicose veins. MATERIALS AND METHODS: Ascending and MR venography were performed in seven legs of seven patients, and duplex Doppler sonography and MR venography in 15 legs of 12 patients, all referred for evaluation of varicose veins. For analysis, the venous system as revealed by ascending and MR venographic images was divided into 13 segments. For detection of reflux to the great saphenous vein, duplex Doppler sonography and MRV were performed. RESULTS: In ascending venography and MRV, 91 venous segments were potentially visible; both modalities depicted 78 of these, but failed to detect four. Ascending venography and MRV detected 17 and 19 varices, respectively. When two tourniquets were placed around the ankle and knee using the Valsalva maneuver, MRV and duplex Doppler sonography detected reflux in 8 of 11 and 13 of 15 legs, respectively. CONCLUSION: Contrast-enhanced 3-D MRV comprehensively displays the venous system of the lower extremities and permits assessment of varicose veins. MRV using the Valsalva maneuver allows assessment of reflux to the great saphenous vein.

The Usefulness of Test Bolus Examination in Three-Dimensional Contrast-Enhanced MR Angiography of the Carotid Artery

PURPOSE: To compare the usefulness of test bolus examination in three-dimensional contrast enhanced MR angiography of the carotid artery with that of the fixed delay time method. MATERIALS AND METHODS: Sixty consecutive patients (mean age, 60.1 years) in whom carotid arterial disease was suspected and who were examined during a 17-month period were divided into two equal groups. For group A, a fixed delay time of 5 secs was used, while for group B, the delay time of the test bolus examination was calculated from the signal intensity versus time curve of the carotid artery, obtained after the test injection of 1 ml contrast material into the right brachal vein. Overall image quality, discrimination between the arterial and the venous phase, and the contrast-to-noise ratio(CNR) of the carotid artery were compared between the two groups. Overall image quality was classified as excellent, good, moderate or poor, and discrimination between the two phases was graded IV-I according to the degree of jugular venous enhancement. RESULTS: In group A, overall image quality of the carotid artery was classified as excellent or good in 13 (43.3%)and 9 (30.0%) cases, respectively, while in group B the corresponding figures were 23 (76.7%) and 5 (16.7%). The differences between the two groups were statistically significant (p<0.05). In terms of discrimination between the arterial and venous phase, 20 (66.7%) of the 30 cases in group A were assigned grade IV or III, while 28 (93.3%) of the 30 in group B were assigned these same grades (p<0.05). The CNR of the carotid artery was higher in group B(67.1 +/-16.1) than in group A(27.3 +/-17.8), with statistical significance(p<0.05). CONCLUSION: For examination of the carotid artery, contrast enhanced MR angiography using a test bolus is su-perior to the fixed delay time method.

The Usefulness of Enhanced 3D-TOF MR Angiography in the Patients with Cerebral Infarction: Comparison with Conventional Angiography

PURPOSE: The aim of this study was to compare the usefulness of enhanced 3D-TOF MR angiography with that of the conventional kind in patients with cerebral ischemic symptoms and to determine the difference between radiologists who have interpreted MR angiograms for less than one year and for more than five years. MATERIALS AND METHODS: Seventy-three patients with clinical symptoms of cerebral ischemic infarction who had undergone conventional angiography MR imaging and MR angiography were involved in this study. On the basis of divisions of the internal carotid artery, three groups were designated: Group I, from the bifurcation of the common carotid artery to the bifurcation of the internal carotid; Group II, from the bifurcation of the internal carotid to the bifurcation of the anterior and middle cerebral artery; Group III, the anterior and middle cerebral artery segments distal to their branching. Two radiologists, one who had interpreted MR angiographic findings for less than one year, and the other for more than 5 years, retrospectively reviewed the findings and graded them according to the degree of vascular stenosis. k statistics were used to measure agreement between the two readers and to compare their techniques. Sensitivity and specificity were calculated only if there were abnormal vascular findings. RESULTS: A total of 438 arteries, 146 in each group, were available. In Group I, agreement between CA and MRA was high; k was 0.538 in reader A and 0.687 in reader B and there was close agreement between the readers(K=0.621). For reader A, sensitivity was 82.4% and specificity was 77.7%, while for reader B, the figures were 88.2% and 87.2%, respectively. In Group II, agreement between CA and MRA was high; k was 0.508 for reader A and 0.566 for reader B and again there was close agreement between the two readers(k=0.622). Reader A showed a sensitivity of 88.2% and a specificity of 73.7%, while for reader B, the corresponding figures were 68.2% and 81.8%. In Group III, agreement between CA and MRA was high; k was 0.508 in reader A and 0.566 in reader B and there was close agreement between (k=0.622). For reader A, sensitivity was 50.0% and specificity was 77.6%, while for reader B, the corresponding figures were 40% and 89.7%. Overall, in total of 438 ar-teries, there was good agreement between each reader (k=0.662). Reader A showed a sensitivity of 81.1% and a specificity of 76.4%, and for reader B, the figures were 83.2% and 86.4%, respectively. CONCLUSIONS: For the evaluation of intracranial vascular disease, e3D-TOF MRA is faster and less invasive than conventional angiography. Regardless of the reader's experience, it shows high sensitivity and there is close agreement between the readers involved. It is thus a useful method for the evaluation of steno-occlusive lesions in patients with cerebral infarction.

Effect of Angulation between Aorta and Renal Artery on Signal Void of Proximal Renal Artery on MR Angiography:Phantom Study

PURPOSE: To determine the effect of anglulation between aorta the and renal artery on signal loss in theproximal renal artery, as seen on magnetic resonance angiography by phantom study using a pulsatile flow model. MATERIALS AND METHODS: Three phantoms of aorta and renal artery with angulation of 90 degree, 60 degree, and 30 degree wereobtained. Pulsatile recirculating flow (44%W/W glycerin, 60bpm) was used for MR angiography. First, axial 3D-TOFimages were obtained and reconstructed. MIP images were analyzed for the presence, area, and location of signalloss. 2D-PC images were obtained perpendicularly to the renal artery at a distance of 0, 4, 8 and 12mm from theostium. To calculate mean signal intensity of the renal artery, a ROI was drawn on 2D-PC images. To correlatesignal loss in 3D-TOF images with signal decrease in 2D-PC, we analyzed changes in signal intensity during onepulse cycle according to change of angulation and distance from the ostium of the renal artery by the calculatedvalues of relative signal decrease and ratio of signal decrease. RESULTS: A signal loss was observed up to 4mmfrom the ostium of the renal artery only in the case of the 90 degree phantom. Because the signal intensity measured inthe 2D-PC image of the 90 degree phantom was higher than that of the 60 degree phantom the signal loss observed in the3D-TOF images of the 90 degree phantom could not be explained by the magnitude of measured signal intensity alone.Relative signal decrease only at a distance of 0 and 4mm in the 90 degree phantom was evenly increased through a pulsecycle and the ratio of signal decrease at the same location was more than 50%. In contrast to the results of the90 degree phantom, those of 60 degree and 30 degree showed decreased of signal intensity mainly during the diastolic phase.CONCLUSION: Signal loss should become apparent at a certain angle between 60 degree and 90 degree. Decreased signalintensity causing signal loss in 3D-TOF was maintained throughout the systolic and diastolic phase of a pulsatilecycle and correlated with the ratio of signal decrease.

Usefulness of 2D PC MRA of the Circle of Willis in the Evaluation of Acute Cere b ral Infarction

PURPOSE: To evaluate the usefulness of axial 2-D PC MRA of the circle of Willis in the evaluation of acute cerebral infarction. MATERIALS AND METHODS: We evaluated 42 patients with acute cerebral infarction who had undergone T2 weighted and diffusion weighted MR imaging (T2WI, DWI) and 2-D PC MRA of the circle of Willis within 72 hours of the onset of symptoms. In conjunction with high-signal lesions on DWI, the findings of 2-D PC MRA were classified as normal, stenotic, or indicative of arterial occlusion; negative 2-D PC MRA was not considered useful. In addition, the signal intensity of T2WI and DWI was compared. RESULTS: (The findings of 2-D PC MRA showed that 15 cases (35.7%) were normal, 13(31%) were stenotic, and that in 14 (33.3 %), occlusion was present). Thus, 2-D PC MRA detected vascular abnormality in 27 cases (64.3 %). On T2WI, six cases (14.3 %) showed no signal change and 36 (85.7 %) showed high signal change. In six cases without signal change, MR images were obtained within 12 hours of ictus; in one of these patients MRA findings were normal, one had stenosis, and in four, occlusion was noted. CONCLUSION: 2-D PC MRA is a useful modality for the detection of vascular abnormality in patients with acute cerebral infarct.

What is the Cause of Signal Inhomogeneity at the Carotid Bifurcation During Contrast Enhanced Carotid MRA?: In Vivo and in Vitro Studies

PURPOSE: To evaluate the hemodynamic causes of signal inhomogeneity at the carotid bulb that might be misinterpreted as pathologic signal defect in carotid contrast enhanced MRA(CEMRA). MATERIALS AND METHODS: Both carotid CEMRA and fast digital subtraction angiography(DSA) were conducted on 15 patients (28 carotid arteries) and arterial phase CEMRA images were compared with fast DSA images of the same patients. A 1.5T MR imager was used. The Turbo-FLASH sequence emplayed was TR/TE/FA= 3 .2m s / 1.3m s / 35 degree. For experimental study, we utilized handmade silicon phantoms of the tortuous carotid bifurcation; these might be expected to clearly demonstrate turbulent flow at the carotid bulb. In a closed circulatory system, both CEMRA and fast DSA involved the use of these phantoms. RESULTS: During CEMRA, inhomogeneous signals of varying degrees were found at the carotid bulb in 12/28 carotid arteries. When compared with sequential DSA images, incomplete mixing of contrast agent due to turbulent flow at the carotid bulb might be responsible for this inhomogeneity. This hypothesis was reinforced by successfully reproducing signal defects at the carotid bulb from the experimental CEMRA study using carotid phantoms that showed marked turbulent flow in the same area during DSA. CONCLUSION: Incomplete mixing of contrast agent caused by turbulent flow at the carotid bulb might be responsible for the signal inhomogeneity seen on carotid CEMRA.

Value of a Bolus-Tagging Method on Contrast-Enhanced Abdominal MR Angiography

PURPOSE: To assess the value of the bolus-tagging method for improving the image quality of contrast-enhanced MR abdominal angiography, and to evaluate the relationship between peak arterial enhancement time and patients' age, weight and heart rate. MATERIALS AND METHODS: Contrast-enhanced 3D FISP abdominal MR angiography was performed in 81 patients during a four-month period. The bolus-tagging method was used in a study group comprising 33 patients, and to this end, 1 ml of Gd-DTPA (gadolinium-diethylenetriamine penta-acetic acid) was administered. thirty sequential images (1 image/sec) were then obtained using turbo-FLASH sequencing. After determining peak arterial enhancement time from the time-to-signal intensity curve, optimal scan delay time can be calculated according to the formula used in our patient series. The 48 patients in whom the bolus-tagging method was not used comprised the control group ; in the study group scanning commenced at the optimal scan delay time (and at 10 seconds in the control group) after the administration of 0.2 mM/kg Gd-DTPA using an automatic power injector. Using a three-point scale we evaluated and compared between the two groups the success with which arterial images were obtained. In addition, vascular visibility -an indication of the quality of arteries and veins-was determined using a four-point scale. In the study group, the relationship between peak arterial enhancement time and patients' age, weight heart rate was also assessed. RESULTS: Pure arterial images were successfully obtained in 32 patients (97%) in the study group and in 40 (83%) in the control group. This difference was not statistically significant (p>.05). With regard to vascular visibility, diagnostic arterial images were seen in 30 patients (91%) in the study group and in 33 patients (69%) in the control group; arterial visibility was significantly better in the study group (p=.0197). On the other hand, the diagnostic venous images were seen in 31 patients (94%) in the study group and in 36 (75%) in the control group; there was no significant difference between the two groups (p=.2367). Peak arterial enhancement time increased significantly with age (r=.443, p=.0098); no correlation,however was seen between peak arterial enhancement time and weight (p>.05) or heart rate (p>.05). CONCLUSION: Used with contrast-enhanced 3-D FISP MR abdominal angiography, the bolus-tagging method provides better arterial visibility. Peak arterial enhancement time increased significantly with age.

Value of a Bolus-Tagging Method on Contrast-Enhanced Abdominal MR Angiography

PURPOSE: To assess the value of the bolus-tagging method for improving the image quality of contrast-enhanced MR abdominal angiography, and to evaluate the relationship between peak arterial enhancement time and patients' age, weight and heart rate. MATERIALS AND METHODS: Contrast-enhanced 3D FISP abdominal MR angiography was performed in 81 patients during a four-month period. The bolus-tagging method was used in a study group comprising 33 patients, and to this end, 1 ml of Gd-DTPA (gadolinium-diethylenetriamine penta-acetic acid) was administered. thirty sequential images (1 image/sec) were then obtained using turbo-FLASH sequencing. After determining peak arterial enhancement time from the time-to-signal intensity curve, optimal scan delay time can be calculated according to the formula used in our patient series. The 48 patients in whom the bolus-tagging method was not used comprised the control group ; in the study group scanning commenced at the optimal scan delay time (and at 10 seconds in the control group) after the administration of 0.2 mM/kg Gd-DTPA using an automatic power injector. Using a three-point scale we evaluated and compared between the two groups the success with which arterial images were obtained. In addition, vascular visibility -an indication of the quality of arteries and veins-was determined using a four-point scale. In the study group, the relationship between peak arterial enhancement time and patients' age, weight heart rate was also assessed. RESULTS: Pure arterial images were successfully obtained in 32 patients (97%) in the study group and in 40 (83%) in the control group. This difference was not statistically significant (p>.05). With regard to vascular visibility, diagnostic arterial images were seen in 30 patients (91%) in the study group and in 33 patients (69%) in the control group; arterial visibility was significantly better in the study group (p=.0197). On the other hand, the diagnostic venous images were seen in 31 patients (94%) in the study group and in 36 (75%) in the control group; there was no significant difference between the two groups (p=.2367). Peak arterial enhancement time increased significantly with age (r=.443, p=.0098); no correlation,however was seen between peak arterial enhancement time and weight (p>.05) or heart rate (p>.05). CONCLUSION: Used with contrast-enhanced 3-D FISP MR abdominal angiography, the bolus-tagging method provides better arterial visibility. Peak arterial enhancement time increased significantly with age.

Collateral Vessels in Moyamoya Disease: Comparison of MR and MRA with Conventional Angiography

PURPOSE: To determine the value of magnetic resonance imaging(MR) and magnetic resonance angiography(MRA) inassessing collateral vessels of moyamoya disease. MATERIALS AND METHODS: Twenty-four patients with moyamoyadisease who underwent MR, 3D TOF MRA, and conventional angiography participated in this study. Two radiologistsworking independently and with no knowledge of the angiographic findings, interpreted the MR and MRA images. Todetermine the presence of parenchymal and leptomeningeal collaterals(48 hemispheres) and transdural collaterals(38hemispheres in 19 patients were depicted by angiography of the external carotid), the findings were compared withthose of angiography. RESULTS: Parenchymal, leptomeningeal, and transdural collaterals were depicted byconventional angiography in 34(71%), 32(67%), and 11(29%) hemispheres respectively. The sensitivity andspecificity of MR/MRA for collateral vessels were 79.1/ 88.1% for parenchymal collaterals, 72.1/ 88.1% forleptomeningeal collaterals, and 0.1/18.1% for transdural collaterals, respectively. Respective sensitivity andspecificity of MR/MRA were 88.94/94.1% for leptomeningeal collaterals, and 18.93/55.1% for transdural collaterals,when the prominent posterior cerebral and external carotid artery were regarded as secondary signs ofleptomeningeal and transdural collateral vessels. CONCLUSION: In moyamoya disease, MR and MRA are useful imagingmodalities for the assessment of collateral vessels. The prominent posterior cerebral artery and external carotidartery can be useful secondary signs of leptomeningeal and transdural collateral vessels.

Three-Dimensional Short-Range MR Angiography and Multiplanar Reconstruction Images in the Evaluation of Neurovascular Compression in Hemifacial Spasm

PURPOSE: To evaluate the diagnostic efficacy of three-dimensional(3D) short-range MR angiography(MRA) andmultiplanar reconstruction(MPR) imaging in hemifacial spasm(HS). MATERIALS AND METHODS: Two hundreds patientswith HS were studied using a 1.5T MRI system with a 3D time-of-flight(TOF) MRA sequence. To reconstructshort-range MRA, 6-10 source images near the 7-8th cranial nerve complex were processed using a maximum-intensityprojection technique. In addition, an MPR technique was used to investigate neurovascular compression. We observedthe relationship between the root-exit zone(REZ) of the 7th cranial nerve and compressive vessel, and identifiedthe compressive vessels on symptomatic sides. To investigate neurovascular contact, asymptomatic contralateralsides were also evaluated. RESULTS: MRI showed that in 197 of 200 patients there was vascular compression orcontact with the facial nerve REZ on symptomatic sides. One of the three remaining patients was suffering fromacoustic neurinoma on the symptomatic side, while in two patients there were no definite abnormal findings. Compressive vessels were demonstrated in all 197 patients; 80 cases involved the anterior inferior cerebellarartery(AICA), 74 the posterior cerebellar artery(PICA), 13 the vertebral artery(VA), 16 the VA and AICA, eight theVA and PICA, and six the AICA and PICA. In all 197 patients, compressive vessels were reconstructed on one 3Dshort-range MRA image without discontinuation from vertebral or basilar arteries. 3D MPR studies providedadditional information such as the direction of compression and course of the compressive vessel. In 31 patientsthere was neurovascular contact on the contralateral side at the 7-8th cranial nerve complex. CONCLUSION: Inpatients with HS, 3D short-range MRA and MPR images are excellent and very helpful for the investigation ofneurovascular compression and the identification of compressive vessels.

Human Brain Mapping of Language-Related Function on 1.5T Magnetic Resonance System: Focused on Motor Language Function

PURPOSE: To investigate the feasibility of functional MR imaging of motor language function and its usefulnessin the determination of hemispheric language dominance. MATERIALS AND METHODS: In order to activate the motorcenter of language, six subjects(5 right-handed, 1 left-handed; 3 males, 3 females) generated words. They wererequested to do this silently, without physical articulation, in response to English letters presented visually.Gradient-echo images (TR/TE/flip angle, 80/60/40o; 64x128 matrix; 10mm thickness) were obtained in three axialplanes including the inferior frontal gyrus. Functional maps were created by the postprocessing of gradient-echoimages, including subtraction and statistics. Areas of activation were topographically analyzed and numbers ofactivated pixels in each region were compared between right and left sides. The reproducibility of functional mapswas tested by repetition of functional imaging in the same subjects. RESULTS: Statistically significant activationsignals were demonstrated in five of six subjects, in whom the distribution of those signals was predominantly inboth frontal lobes. Hemispheric lateralization of activation, when activated pixels were compared between bothinferior frontal gyri, was in all cases on the left. In four subjects, functional maps were reproduced in asimilar fashion. CONCLUSION: Our results suggest that functional MR imaging can depict the activation of motorlanguage function in the brain and can be used as a useful non-invasive method for determining the hemisphericdominance of language.

Ultrafast Contrast-Enhanced MR Angiography of the Carotid Artery: Time Optimization for Discrimination of theArterial from the Venous Phase

PURPOSE: To investigate the optimal delay and acquisition time for discrimination of the arterial from thevenous phase in ultrafast 3D contrast-enhanced MR angiography of the carotid artery. MATERIALS AND METHODS: Wereviewed the MR angiographic findings of 233 patients in whom carotid stenosis and cerebrovascular disease weresuspected. On the basis of delay and acquisition time they were divided into four groups. In the first three,contrast material was injected manually, and after the optimal time, mechanical injection was used for the lastgroup. On the basis of signal intensity of the carotid artery, image quality was graded in four steps.Discrimination of the arterial from the venous phase was graded in three steps, based on the degree of venousenhancement. RESULTS: The best grade of image quality was 70% in the first group, 85% in the second, and 95% inthe third. In discrimination of the arterial-venous phase, the most definite grade was 50% in the first group, 62%in the second, and 75% in the third. Between manual and mechanical injection groups, there was no significantdifference in image quality and discrimination of the arterial-venous phase. CONCLUSION: These results suggestthat for ultrafast 3D contrast-enhanced MR angiography of the carotid artery, with manual injection of contrastmaterial, 8-second delay time and 7-second acqusistion time are optimal.