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.

Feasibility and Diagnostic Accuracy of Whole Heart Coronary MR Angiography Using Free-Breathing 3D Balanced Turbo-Field-Echo with SENSE and the Half-Fourier Acquisition Technique

OBJECTIVE: We wanted to assess the feasibility and diagnostic accuracy of whole heart coronary magnetic resonance angiography (MRA) with using 3D balanced turbo-field-echo (b-TFE) with SENSE and the half-Fourier acquisition technique for identifying stenoses of the coronary artery. MATERIALS AND METHODS: Twenty-one patients who underwent both whole heart coronary MRA examinations and conventional catheter coronary angiography examinations were enrolled in the study. The whole heart coronary MRA images were acquired using a navigator gated 3D b-TFE sequence with SENSE and the half-Fourier acquisition technique to reduce the acquisition time. The imaging slab covered the whole heart (80 contiguous slices with a reconstructed slice thickness of 1.5 mm) along the transverse axis. The quality of the images was evaluated by using a 5-point scale (0 - uninterpretable, 1 - poor, 2 - fair, 3 - good, 4 - excellent). Ten coronary segments of the heart were evaluated in each case; the left main coronary artery (LM), and the proximal, middle and distal segments of the left anterior descending (LAD), the left circumflex (LCX) and the right coronary artery (RCA). The diagnostic accuracy of whole heart coronary MRA for detecting significant coronary artery stenosis was determined on the segment-by-segment basis, and it was compared with the results obtained by conventional catheter angiography, which is the gold standard. RESULTS: The mean image quality was 3.7 in the LM, 3.2 in the LAD, 2.5 in the LCX, and 3.3 in the RCA, respectively (the overall image quality was 3.0+/-0.1). 168 (84%) of the 201 segments had an acceptable image quality (> or = grade 2). The sensitivity, specificity, accuracy, negative predictive value and positive predictive value of the whole heart coronary MRA images for detecting significant stenosis were 81.3%, 92.1%, 91.1%, 97.9%, and 52.0%, respectively. The mean coronary MRA acquisition time was 9 min 22 sec (+/-125 sec). CONCLUSION: Whole heart coronary MRA is a feasible technique, and it has good potential to evaluate the major portions of the coronary arteries with an acceptable image quality within a reasonable scan time.

Traumatic Carotid-cavernous Fistula with Contralateral Proptosis: Case Report

Traumatic carotid-cavernous fistula frequently results in proptosis on the side of the fistula by retrograde drainage from the cavernous sinus to the superior ophthalmic vein. The involvement of the opposite orbit is due to the presence of connections between the cavernous sinuses on both sides, but exclusive contralateral orbit involvement is rare. We report a case in which the CCF with a contralateral proptosis developed in a 63 year-old man after a motor vehicle accident. MR angiography depicted the markedly dilated left cavernous sinus and left superior ophthalmic vein, sparing the right side. However, angiography showed a direct fistula between the right internal carotid artery and cavernous sinus with exclusive contralateral venous drainage via the intercavernous sinus. A detachable balloon was used to occlude the fistula, and the contralateral orbital symptom regressed.

Sinus Pericranii in an Infant: MR Imaging and Angiographic Findings

Sinus pericranii is a rare vascular anomaly involving abnormal communication between the intracranial and extracranial venous circulations. Although the condition can be diagnosed clinically, imaging is required to distinguish it from other entities and to identify the connection between the extracranial and intracranial dural venous sinus. We report the characteristic MR imaging and angiographic findings of a case of sinus pericranii.

Usefulness of PC Based 3D Volume Rendering Technique in the Evaluation of Suspected Aneurysm on Brain MRA

PURPOSE: To evaluate usefulness of volume rendering technique using 3D visualization software on PC in patients with suspected intracranial aneurysm on brain MRA. MATERIALS AND METHODS: We analyzed prospectively 21 patients with suspected aneurysms on the routine MIP images which were obtained 15 degree increment along axial and sagittal plane, among 135 patients in whom brain MRA was done due to stroke symptoms for recent 5 months. The locations were the anterior communicating artery (A-com) in 8 patients, the posterior communicating artery (P-com) in 3, the ICA bifurcation in 5, the MCA bifurcation in 4, and the basilar tip in one. Male to female ratio was 14:7 and mean age was 62 years. MRA source images were sent to PC through LAN, and the existence of aneurysm was evaluated with volume rendering technique using 3D visualization software on PC. The presence or absence of aneurysm on MIP and volume rendering images was decided by the consensus of two radiologists. RESULTS: We found the aneurysms with volume rendering technique, from 1 patient among 8 patients with suspected aneurysm at A-com and also 1 patient among 3 patients with suspected aneurysm at P-com on routine MIP images. Confirmative angiography and interventional procedures were done in these 2 patients. The causes for mimicking the aneurysm on MIP were flow displacement artifact in 9, normal P-com infundibulum in 2, and overlapped or narrowed vessels in 8 patients, and among them confirmative angiography was done in 2 patients. CONCLUSION: Volume rendering technique using visualization software on PC is useful to scrutinize the suspected aneurysm on routine MIP images and to avoid further invasive angiography.

Usefulness of Digital Subtraction Technique in the Contrast-enhanced Multi-phasic Abdominal MR angiography

PURPOSE: To assess the usefulness of digital subtraction contrast-enhanced multi-phase magnetic resonance angiography (MRA) for evaluation of the vessels of the gastrointestinal system. MATERIALS AND METHODS: Twenty-five patients who underwent abdominal MRA for evaluation of the vessels of the gastrointestinal system were included in this study. MRA was performed using a 1.5-T scanner and the 3-D turbo-FLASH sequence. Subtraction images of the arterial and portal venous phases were obtained by subtracting arterial phase images from mask images and portal venous phase images from arterial phase images, respectively. Each set of images was processed using a maximum-intensity projection (MIP) algorithm to produce three-dimensional angiograms. We compared overall image quality and the visibility of normal and abnormal vessels between subtraction and non-subtraction MRA. RESULTS: In terms of subjective image quality, subtraction and non-subtraction MRA was similar both the arterial and portal venous phases (p>0.05). During the arterial phase, subtraction MRA visualized more peripheral branches of the left gastric and superior mesenteric arteries than non-subtraction MRA (p<0.05), and during the portal venous phase, subtraction MRA demonstrated more peripheral branches of the superior mesenteric (p<0.01), splenic (p<0.05) and left portal vein (p<0.05) than non-subtraction MRA. In addition, overall visibility of the arterial and portal venous branches was superior with subtraction MRAs than with non-subtraction MRA. Both of these detected all anomalous arterial branching (n=5) and abnormal (encased or obstructed) portal veins (n=5). Subtraction MRA visualized 17 portal venous collaterals in six patients, whereas non-subtraction MRA visualized only seven collateral veins. CONCLUSION: In contrast-enhanced abdominal MRA, the digital subtraction technique permits visualization of more distal branches of the vessels of both the arterial and portal venous systems without significant degradation of image quality. The technique is particularly useful for the detection of portal venous collaterals in patients with portal hypertension.

Contrast-Enhanced Magnetic Resonance Angiography: Dose the Test Dose Bolus Represent the Main Dose Bolus Accurately?

OBJECTIVE: To determine whether the time-intensity curves acquired by test and main dose contrast injections for MR angiography are similar. MATERIALS AND METHODS: In 11 patients, repeated contrast-enhanced 2D-turbo-FLASH scans with 1-sec interval were obtained. Both test and main dose time-intensity curves were acquired from the abdominal aorta, and the parameters of time-intensity curves for the test and main boluses were compared. The parame-ters used were arterial and venous enhancement times, arterial peak enhance-ment time, arteriovenous circulation time, enhancement duration and enhance-ment expansion ratio. RESULTS: Between the main and test boluses, arterial and venous enhance-ment times and arteriovenous circulation time showed statistically significant correlation (p < 0.01), with correlation coefficients of 0.95, 0.92 and 0.98 respectively. Although the enhancement duration was definitely greater than infusion time, reasonable measurement of the end enhancement point in the main bolus was impossible. CONCLUSION: Only arterial and venous enhancement times and arteriovenous circulation time of the main bolus could be predicted from the test-bolus results. The use of these reliable parameters would lead to improvements in the scan timing method for MR angiography.

Contrast-Enhanced Magnetic Resonance Angiography: Dose the Test Dose Bolus Represent the Main Dose Bolus Accurately?

OBJECTIVE: To determine whether the time-intensity curves acquired by test and main dose contrast injections for MR angiography are similar. MATERIALS AND METHODS: In 11 patients, repeated contrast-enhanced 2D-turbo-FLASH scans with 1-sec interval were obtained. Both test and main dose time-intensity curves were acquired from the abdominal aorta, and the parameters of time-intensity curves for the test and main boluses were compared. The parame-ters used were arterial and venous enhancement times, arterial peak enhance-ment time, arteriovenous circulation time, enhancement duration and enhance-ment expansion ratio. RESULTS: Between the main and test boluses, arterial and venous enhance-ment times and arteriovenous circulation time showed statistically significant correlation (p < 0.01), with correlation coefficients of 0.95, 0.92 and 0.98 respectively. Although the enhancement duration was definitely greater than infusion time, reasonable measurement of the end enhancement point in the main bolus was impossible. CONCLUSION: Only arterial and venous enhancement times and arteriovenous circulation time of the main bolus could be predicted from the test-bolus results. The use of these reliable parameters would lead to improvements in the scan timing method for MR angiography.

The Optimization of Scan Timing for Contrast-Enhanced Magnetic Resonance Angiography

OBJECTIVE: To determine the optimal scan timing for contrast-enhanced magnetic resonance angiography and to evaluate a new timing method based on the arteriovenous circulation time. MATERIALS AND METHODS: Eighty-nine contrast-enhanced magnetic resonance angiographic examinations were performed mainly in the extremities. A 1.5T scanner with a 3-D turbo-FLASH sequence was used, and during each study, two consecutive arterial phases and one venous phase were acquired. Scan delay time was calculated from the time-intensity curve by the traditional (n = 48) and/or the new (n = 41) method. This latter was based on arteriovenous circulation time rather than peak arterial enhancement time, as used in the traditional method. The numbers of first-phase images showing a properly enhanced arterial phase were compared between the two methods. RESULTS: Mean scan delay time was 5.4 sec longer with the new method than with the traditional. Properly enhanced first-phase images were found in 65% of cases (31/48) using the traditional timing method, and 95% (39/41) using the new method. When cases in which there was mismatch between the target vessel and the time-intensity curve acquisition site are excluded, erroneous acquisition occurred in seven cases with the traditional method, but in none with the new method. CONCLUSION: The calculation of scan delay time on the basis of arteriovenous circulation time provides better timing for arterial phase acquisition than the traditional method.

Low-dose Contrast-enhanced Magnetic Resonance Angiography with Less than the Standard Dose of Gadolinium Chelate: Comparison with Conventional Digital Subtraction Angiography

PURPOSE: To evaluate the effectiveness of contrast-enhanced MR angiography (CEM-RA)using gadolinium chelate at less than the standard dose. MATERIALS AND METHODS: Eight patients with occlusive arterial disease underwent 16 CEMRA scans of the lower extremities following bolus injection of 0.075 mmol/kg gadolinium, using a 1.5T scanner and 3D-turbo-FLASH sequence. The arterial phase was compared with that obtained by digital subtraction angiography (DSA). After grouping arteries according to their diameter, arterial detectability (AD), stenosis grad-ing (SG), and the detectability of significant stenosis (SD) were compared. RESULTS: The AD of CEMRA showed high specificity (Sp, 98%-100%) in all groups, and sensitivity (Sn) was high (>90%) in groups I, II, and III. SG showed a correlation coefficient of 0.65* and 0.60* in groups I and II, though CEMRA tended to overesti-mate. SD was high (Sn,100%) in all groups, but Sp was low(<70%). CONCLUSION: Low-dose CEMRA is an excellent way to exclude significant arterial ob-struction in the lower extremities, even in small arteries. Stenosis grading was possible in large arteries but consideration must be paid to the technique 's overestimating characteristic.