3D-TOF Magnetic Resonance Angiography Research Articles

Follow-up of coiled intracranial aneurysms: comparison of 3D time-of-flight and contrast-enhanced magnetic resonance angiography at 3T in a large, prospective series

To compare 3D-TOF magnetic resonance angiography (MRA) and contrast-enhanced MRA (CE-MRA) sequences at 3T in the follow-up of coiled aneurysms with digital subtracted angiography (DSA) as the gold standard. DSA, 3D-TOF and CE-MRA were performed in a prospective series of 126 aneurysms in 96 patients (57 female, 39 male; age: 25-75years, mean: 51.3 ± 11.3years). The quality of aneurysm occlusion was assessed independently and anonymously by a core laboratory. Using DSA (gold standard technique), total occlusion was depicted in 57 aneurysms (45.2%), neck remnant in 34 aneurysms (27.0%) and aneurysm remnant in 35 aneurysms (27.8%). Sensitivity, specificity, positive predictive value and negative predictive value were very similar with 3D-TOF and CE-MRA. Visibility of coils was much better with 3D-TOF (95.2%) than with CE-MRA (23.0%) (P < 0.001). Also, substantial artefacts were less frequent with 3D-TOF (4.0%) than with CE-MRA (11.9%; P = 0.012). In this large prospective series of patients with coiled aneurysms, at 3T 3D-TOF MRA was equivalent to CE-MRA for the evaluation of aneurysm occlusion, but coil visibility was superior at 3D-TOF. Thus the use of 3D-TOF at 3T is recommended for the follow-up of coiled intracranial aneurysms. • Different Magnetic Resonance (MR) imaging techniques are used to evaluate intracranial aneurysms. • At 3T MR, 3D-TOF and CE-MRA appear equivalent for evaluating coiled aneurysms.. • Coils are better visualised on 3D-TOF than on CE-MRA. • Combined analysis of 3D-TOF and CE-MRA does not seem helpful. • At 3T, 3D-TOF techniques are recommended for monitoring patients with coiled aneurysms.

High-resolution magnetic resonance angiography of digital arteries in SSc patients on 3 Tesla: preliminary study

We sought to evaluate the use of high-resolution three-dimensional time of flight (3D TOF) magnetic resonance angiography (MRA) at 3 Tesla in the visualization of digital arteries in SSc patients. A total of 33 patients with SSc [32 females and 1 male; mean (s.d.) age 37.0 (10.2) years; median number of years since onset of RP 3.4 (2.8) years] and 7 healthy controls [6 females and 1 male; mean (s.d.) age 30.7 (3.5) years] were examined on a 3T MR system. A modified high spatial resolution (voxel size = 0.35 × 0.35 × 0.5 mm(3)) 3D TOF MRA (repetition time/echo time = 19/4.4 ms, flip angle = 15°, slice thickness = 1 mm) was performed during a total scan time of 8 min 22 s. The source images and maximum intensity projection reconstruction were studied; the digital arteries count and lumen area of the selective section of the vessel were measured independently by two experienced radiologists and compared with that of the control ones; and a four-level grading system was made according to the severity. Statistical analysis was performed with t-test and P < 0.05 was used as the criterion. We detected the eight digital arteries in the four fingers (without the thumb) of each case and got a 47.58% presentation in general in the SSc group, and artery No. 5 had the highest presentation rate (70.97%). Statistics showed that the digital arteries No. 1 (P = 0.058) and No. 3 (P = 0.093) had no difference in the lumen area (P > 0.05). We finally got 3 cases in Grade 1, 14 cases in Grade 2, 9 cases in Grade 3 and 5 cases in Grade 4. MRA of the digital arteries in the described technique is a promising method for us to judge the severity of microvascular involvement in finger vessels of SSc patients.

Incidental Findings of Persistent Primitive Trigeminal Artery on 3-Dimensional Time-of-Flight Magnetic Resonance Angiography at 3.0 T: An Analysis of 25 Cases

Currently, the presence of persistent primitive trigeminal artery (PPTA) is detected by digital subtraction angiography (DSA); most publications on this cerebrovascular variation have been individual case reports. This study is to evaluate the efficacy of 3-dimensional time-of-flight magnetic resonance angiography (3D-TOF MRA) at 3.0 T for the detection and classification of PPTA based on a large case series. Between June 2007 and October 2008, 4,650 patients underwent magnetic resonance angiography (MRA) examination at 3.0 T in our hospital. MRA was performed using 3D-TOF with volume rendering (VR) and maximum intensity projection (MIP) technique. The PPTA was classified according to the Saltzman classification system. The occurrence of cerebral vascular diseases accompanying PPTA was studied. Among the 4,650 patients with MRA examined, 25 were identified as having PPTA; the prevalence of PPTA was .54%. The Saltzman classification of PPTAs was as follows: type I, 24%; type II, 16%; type III, 60%. Sixteen percent of the cases with PPTA were accompanied with intracranial aneurysm. A 3D-TOF MRA at 3.0 T can be used for the detection of PPTA and making a classification of PPTA indirectly. The incidence of PPTA with type III was greater than that of other types of PPTA. Intracranial aneurysm appeared to be associated with PPTA.

Accurate assessment of carotid artery stenosis in atherosclerotic mice using accelerated high-resolution 3D magnetic resonance angiography

High-resolution magnetic resonance angiography (MRA) enables non-invasive detection and longitudinal monitoring of atherosclerosis in mouse models of human disease. However, MRA is hampered by long acquisition times putting high demands on the physiological stability of the animal. Therefore, we evaluated the feasibility of accelerated MRA using the parallel imaging technique SENSE with regard to both lesion detection and quantification. MRA acquisitions of supra-aortic vessels were performed in ApoE (-/-) mice that have been shown to develop atherosclerotic plaques. Findings obtained from accelerated data sets were compared to fully sampled reference data sets and histology. Our results revealed only minor differences in detecting vascular lesions for data collections accelerated by factors of up to 3.3 using a four-element coil array. For vessels with a mean lumen diameter of 500 μm, morphometry of stenotic lesions revealed no substantial deviations from reference (fully sampled) data for all investigated acceleration factors. For the highest acceleration factor of 3.3, an average deviation of the degree of stenosis of 4.9 ± 3.6% was found. Common carotid stenoses assessed by in vivo MRA displayed a good correlation with histological analyses (slope of linear regression = 0.97, R (2) = 0.98). According to the results of this work, we have demonstrated the feasibility and accuracy of accelerated high-resolution 3D ToF MRA in mice suitable for detailed depiction of mouse supra-aortic vessels and amenable to non-invasive quantification of small atherosclerotic lesions.

High signal intensity in the dural sinuses on 3D-TOF MR angiography at 3.0 T

Purpose The objective of this study was to examine the frequency of high signal intensity in the dural sinuses of normal subjects upon magnetic resonance (MR) angiography using 3.0-T scanners. Methods A total of 748 consecutive healthy subjects underwent three-dimensional time-of-flight MR angiography at 3.0 T. Sixteen subjects were excluded. MR angiographic source images were retrospectively reviewed for the presence of high signal intensity in the inferior petrosal sinus, pterygoid sinus, or sigmoid sinus. Results Of the 732 examinations, 10 (1.3%) showed high signal intensity in the dural sinuses (left inferior petrosal sinus, n=4; left pterygoid sinus, n=3; left sigmoid sinus, n=6). High signal intensity in the dural sinuses was observed only on the left side. The minimum diameter of the left brachiocephalic vein was significantly smaller in subjects with high signal intensity than in the control group. Conclusion In our study with healthy subjects at 3.0 T, the frequency of high signal intensity in the dural sinuses is as low as 1.3%. Retrograde flow due to physiological stenosis of the left brachiocephalic vein may be one of the causes of this phenomenon.

Case control MR‐CISS and 3D TOF MRA imaging study of medullary compression and hypertension in hemifacial spasm

The association between ventro-lateral medulla (VLM) compression and hypertension has not been compared between hemifacial spasm (HFS) and healthy controls using advanced magnetic resonance imaging (MRI) techniques specific for detecting neurovascular compression. We conducted a MR-constructive interference in a steady state (CISS) and Magnetic Resonance Angiography (MRA) imaging study of VLM compression in hypertensive HFS patients and hypertensive controls compared with healthy controls without hypertension. A total of 125 subjects, including 45 HFS, 51 healthy controls, and 29 hypertensive controls were included. When compared with healthy controls, there was a higher prevalence of VLM compression in hypertensive HFS (82.2% vs. 41.2%, P < 0.001, odds ratio = 6.61, 95% CI 2.37-19.48), and hypertensive controls (72.4% vs. 41.2%, P = 0.007, odds ratio = 3.75, 95% CI 1.42-9.89). Although the prevalence in hypertensive HFS was higher compared to controls with hypertension, this was not significant (82.2% vs. 72.4%). Compared to healthy controls, there was an increasing proportion of higher compression scores on the right (P = 0.001) and left (P = 0.038) (chi square for trend) in hypertensive HFS and hypertensive controls. Kruskal-Wallis test revealed that the mean right compression score on the right (P = 0.003), left (P = 0.026) and the mean bilateral compression score (P < 0.0001) was higher in hypertensive HFS and hypertensive controls compared to healthy controls. MR-CISS and MRA imaging revealed a greater likelihood of VLM compression in hypertensive HFS and hypertensive controls compared to healthy controls. Our case control study provides further support that VLM compression is associated with hypertension in HFS.

3D TOF MRA of Intracranial Aneurysms at 1.5 T and 3 T: Influence of Matrix, Parallel Imaging, and Acquisition Time on Image Quality–A Vascular Phantom Study

A 3-T magnetic resonance imaging system provides a better signal-to-noise ratio and inflow effect than 1.5 T in three-dimensional time-of-flight (3D TOF) magnetic resonance angiography (MRA). The purpose of this study is to analyze the influence of matrix, parallel imaging, and acquisition time on image quality of 3D TOF MRA at 1.5 and 3 T, and to illustrate whether the combination of larger matrixes with parallel imaging technique is feasible, by evaluating the visualization of simulated intracranial aneurysms and aneurysmal blebs using a vascular phantom with pulsatile flow. An anthropomorphic vascular phantom was designed to simulate the various intracranial aneurysms with aneurysmal bleb. The vascular phantom was connected to an electromagnetic flow pump with pulsatile flow, and we obtained 1.5- and 3-T MRAs altering the parameters of 3D TOF sequences, including acquisition time. Two radiologists evaluated the depiction of simulated aneurysms and aneurysmal blebs. The aneurysmal blebs were not sufficiently visualized on the high-spatial resolution 1.5-T MRA (matrix size of 384 x 256 or 512 x 256), even with longer acquisition time (9 or 18 min). At 3 T with acquisition time of 4.5 min using parallel imaging technique, however, the depiction of aneurysmal blebs was significantly better for the high-spatial resolution sequence than for the standard resolution sequence. For the high-spatial resolution sequence, the longer acquisition times did not improve the depiction of aneurysmal blebs in comparison with 4.5 min at 3 T. For 3D TOF MRA, the combination of the large matrix with parallel imaging technique is feasible at 3 T, but not at 1.5 T.

Fusion of Magnetic Resonance Angiography and Magnetic Resonance Imaging for Surgical Planning for Meningioma -Technical Note-

A fusion technique for magnetic resonance (MR) angiography and MR imaging was developed to help assess the peritumoral angioarchitecture during surgical planning for meningioma. Three-dimensional time-of-flight (3D-TOF) and 3D-spoiled gradient recalled (SPGR) datasets were obtained from 10 patients with intracranial meningioma, and fused using newly developed volume registration and visualization software. Maximum intensity projection (MIP) images from 3D-TOF MR angiography and axial SPGR MR imaging were displayed at the same time on the monitor. Selecting a vessel on the real-time MIP image indicated the corresponding points on the axial image automatically. Fusion images showed displacement of the anterior cerebral or middle cerebral artery in 7 patients and encasement of the anterior cerebral arteries in 1 patient, with no relationship between the main arterial trunk and tumor in 2 patients. Fusion of MR angiography and MR imaging can clarify relationships between the intracranial vasculature and meningioma, and may be helpful for surgical planning for meningioma.

Clinical Study and Comparison of Magnetic Resonance Angiography (MRA) and Angiography Diagnosis of Blunt Vertebral Artery Injury

Two-dimensional time-of-flight (2D TOF) magnetic resonance angiography (MRA) is the major method for detecting vertebral artery injury (VAI). But there is still controversy over MRA's accuracy in detecting VAI of varying degrees, a technique for which there are no animal studies found in the literature. The purpose of this study was to evaluate the value of MRA for detecting vertebral artery injury in cervical spinal trauma patients and to conduct a comparative study of MRA and angiography of blunt vertebral artery injury in an animal experiment. In clinical study, 319 patients with close cervical spinal trauma underwent 2D TOF MRA prospective examination. The strike-induced flexion injury model of the cervical spine was constructed based on animal experiment with 14 adult dogs. X-ray studies were performed immediately after injury. 2D TOF MRA and angiography were formed within 24 to 36 hours. Vertebral artery injury was detected by 2D TOF MRA in 52 of the 319 patients. Of the 52 patients, there were 51 unilateral vertebral artery injuries, including 22 injuries on the left vertebral artery and 29 on the right vertebral artery. One patient sustained bilateral vertebral artery injury. Seven dogs had unilateral VAI (5 on the left, 2 on the right), and two dogs had narrower-than-normal left vertebral arteries on MRA examination. Angiography showed occlusion exactly in seven dogs with unilateral vertebral artery injury detected by MRA and no abnormal findings were detected in five dogs without vertebral artery injury on MRA. In two dogs with incomplete left vertebral artery flow-related enhancement on MRA, angiography showed occlusion in one dog and no vertebral injury with normal image in the other. 2D TOF MRA is an effective detection method of blunt vertebral artery injury but it might not be able to differentiate spasm, a small disruption of intima, from others under certain conditions.

MR angiographic evaluation is limited in intracranial aneurysms embolized with Nexus coils

Nexus coils are a type of bioactive coil used to embolize intracranial aneurysms. The purpose of this study was to test the feasibility of the noninvasive follow-up of aneurysms treated with Nexus coils by means of magnetic resonance angiography (MRA). Three-dimensional (3D) time-of-flight (TOF) MRA images of patients treated with Nexus coils (the Nexus coil group) or bare platinum coils (the control group) were compared for the severity and frequency of artifacts. The reviewers were unaware of the coil types used. In the Nexus coil group, 17 MRA examinations were performed in 14 patients harboring 15 aneurysms treated with Nexus coils using 3-T (n = 11) and 1.5-T (n = 6) MR units. The findings of these examinations were compared to those of 28 MRA studies conducted on 24 control patients (bare platinum coils). Conventional angiograms, maximum intensity projections, and source data of 3D-TOF MRA were reviewed in terms of residual flow within aneurysms and parent arterial patencies. The qualities of the MRA images were rated from grade 0 (no significant signal loss) to grade 2 (complete segmental signal loss of the parent artery). The normalized ratio, defined as the diameter of signal loss on MRA axial source images (in mm) divided by that of coil mass on plain radiographs (in mm), was calculated to compare the sizes of coil-related artifacts in the two groups. The quality of the MRA image for the Nexus coil group was significantly poorer than that for the control group (p < 0.0001) due to signal loss caused by the presence of artifacts in the former. In particular, the interpretation of aneurysmal status was impossible in all cases of coiled aneurysms due to segmental signal loss. The sizes of the MRA artifacts were also significantly larger in the Nexus coil group (normalized ratio 1.61 +/- 0.22 vs. 1.15 +/- 0.20; p < 0.0001). Follow-up evaluations by 3D-TOF MRA of aneurysms treated with Nexus coils are severely limited.

Retrograde flow in the dural sinuses detected by three-dimensional time-of-flight MR angiography

Retrograde flow in the left dural sinuses is sometimes detected by three-dimensional time-of-flight (3D-TOF) magnetic resonance (MR) angiography. The purpose of this study was to evaluate the incidence of this phenomenon and its characteristic features on 3D-TOF MR angiograms. We retrospectively reviewed cranial MR angiography images of 1,078 patients examined at our institution. All images were obtained by the 3D-TOF technique with one of two 1.5-T scanners. Maximum intensity projection (MIP) images in the horizontal rotation view were displayed stereoscopically. We reviewed the source images, inferosuperior MIP images, and horizontal MIP images and identified retrograde flow in the dural sinuses. We found retrograde flow in the dural sinuses of 67 patients on the source images from 3D-TOF MR angiography; the incidence was 6.2%. In 47 of the 67 patients, retrograde flow was identified in the left inferior petrosal sinus, in 13, it was seen in the left sigmoid sinus, and in 6, it was seen in the left inferior petrosal and left sigmoid sinuses. The remaining patient had retrograde flow in the left inferior petrosal and left and right sigmoid sinuses. The mean age of the patients with retrograde flow was slightly greater than that of the patients without this phenomenon (70 years vs 63 years). Retrograde flow in the dural sinuses frequently occurs on the left side in middle-aged and elderly patients during 3D-TOF MR angiography performed with the patient in the supine position. This phenomenon should not be misdiagnosed as a dural arteriovenous fistula.

Comparison of intracranial 3D-ToF-MRA with and without parallel acquisition techniques at 1.5T and 3.0T

Purpose: To evaluate the performance of four 3D-ToF Magnetic Resonance Angiography (MRA) sequences with and without integrated parallel acquisition techniques (iPAT) at 1.5T and 3.0T in imaging of intracranial vessels.

The value of MR angiography techniques in the detection of head and neck paragangliomas

Objective: The objective of this study was to compare three-dimensional phase-contrast angiography (3D PCA), 2D time-of-flight (2D TOF), and 3D TOF magnetic resonance (MR) angiography and a proton density weighted technique in terms of their ability to detect head and neck paragangliomas. Materials and methods: 14 patients with 29 paragangliomas were examined at 1.5 T. Three MR angiography sequences (3D PCA, 2D TOF, and multi-slab 3D TOF) and a proton density (PD) weighted sequence were reviewed by four neuroradiologists. The gold standard was digital subtraction angiography. Presence of tumor was assessed in five grades of confidence. Sensitivity and specificity were calculated after dichotomizing the results. Data was analyzed using the logistic regression method. Results: Mean sensitivity and specificity for the four observers were for PD: 72%/97%, for 3D PCA: 75%/90%, for 2D TOF: 66%/93%, and for 3D TOF: 90%/92%. Sensitivity was significantly better for 3D TOF MRA ( P<0.001). No substantial between-observer variation for tumor detection was present. Conclusion: Our results demonstrate that, using 3D TOF MRA, paragangliomas in the head and neck region can be detected with high sensitivity and specificity. Further investigation is necessary to judge the value of 3D TOF MR angiography against fat suppressed contrast enhanced T1 weighted and fat suppressed T2 weighted MR sequences to find the optimal imaging sequence for paragangliomas.

Overestimation of carotid artery stenosis with magnetic resonance angiography compared with digital subtraction angiography

Three-dimensional time-of-flight (3D TOF) magnetic resonance angiography (MRA) is generally considered to overestimate the degree of stenosis in the internal carotid artery (ICA) in comparison with the reference standard intraarterial digital subtraction angiography (DSA). We evaluated whether the degree of stenosis was more accurately assessed with 3D TOF MRA if corresponding projections on MRA and DSA were compared instead of comparison of maximal stenosis at MRA with maximal stenosis at DSA. From February 1997 to December 1999, we included 186 symptomatic and 17 asymptomatic consecutive patients suspected of having carotid artery stenosis on the basis of clinical presentation and screening with duplex ultrasound scan examination. All patients subsequently underwent DSA and MRA imaging. From each ICA, 12 maximum intensity projections with 3D TOF MRA and two or three projections with DSA were obtained. First, we compared the maximal stenosis at MRA with the maximal stenosis at DSA. Subsequently, we used the stenosis at MRA measured on the projection corresponding with the DSA projection that showed the maximal stenosis. For both strategies, the mean differences in stenosis and sensitivity and specificity for assessment of severe stenosis (70% to 99%) were calculated and compared. The MRA and DSA images of 354 ICAs could be compared. The sensitivity and specificity of MRA with the projection that showed the maximal stenosis were 92.6% (95% CI, 85.3% to 97.0%) and 82.7% (95% CI, 78.1% to 87.3%), respectively. The sensitivity and specificity with the MRA projection, corresponding with the DSA projection showing the maximal stenosis, were 88.3% (95% CI, 81.8% to 94.8%) and 89.6% (95% CI, 85.9% to 93.3%), respectively. The mean difference between maximal stenosis at MRA and DSA was 7.5% (95% CI, 5.2% to 9.9%). The mean difference between stenosis at MRA and DSA in corresponding projections was 0.4% (95% CI, -2.0% to 2.7%). If corresponding MRA and intraarterial DSA projections are compared, 3D TOF MRA does not overestimate carotid stenosis.

Gadolinium-enhanced Breathhold Three-dimensional Time-of-Flight Renal MR Angiography in the Evaluation of Potential Renal Donors

To evaluate the utility of gadolinium-enhanced three-dimensional (3D) time-of-flight (TOF) magnetic resonance angiography (MRA) of the renal arteries in the evaluation of potential renal donors. Fifty consecutive patients underwent gadolinium-enhanced 3D-TOF MRA of the renal arteries as part of their evaluation as possible renal donors. All imaging was performed on a 1.5-T system with use of a torso phased-array coil. Conventional T1-weighted axial spin-echo and T2-weighted axial fast spin-echo imaging was performed to evaluate the renal parenchyma. Coronal dynamic MRA was performed during bolus injection of 40 mL of gadolinium with use of a 3D-TOF sequence requiring a breathhold of approximately 30 seconds. Maximum-intensity-projection reconstructions were obtained of the renal arterial and venous anatomy. All studies were prospectively evaluated by a single radiologist experienced with body MRA. Intraoperative findings were used as the reference standard in 35 patients. To evaluate interobserver variability, each examination was evaluated for image quality, renal artery number, and anatomy by two radiologists experienced with MRA and blinded to the other's interpretations and surgical results. Ninety-eight percent of all MRAs were graded as diagnostic quality (Kappa value = 0.38; P < .05). Multiple renal arteries were identified in 29 (29%) of 100 kidneys. Four of 50 patients studied (8%) had renal parenchymal abnormalities identified with MR imaging. Sensitivity and specificity for accessory renal artery detection was 71% and 95%, respectively. Overall, accuracy for MRA in determining renal artery number was 90%. Gadolinium-enhanced breathhold 3D-TOF renal MRA is sufficient to assess the renal arteries in potential donors.

Role of 3D-TOF magnetic resonance angiography for intracranial meningioma

Three-dimensional (3D) time of flight (TOF) magnetic resonance angiography (MRA) was performed in 13 patients with intracranial meningioma. 3D-TOF unenhanced MRA depicted arterial displacement by tumour, and poorly demonstrated the sinuses, veins and tumour mass. The direct visualization of the venous abnormalities on 3D-TOF MRA was improved by the administration of contrast material. 3D-TOF enhanced MRA simultaneously depicted tumour enhancement, arterial and/or venous displacement, and dural sinus involvement by the tumour, all of which were in good agreement with findings on conventional cerebral angiography. However, MRA tended to poorly demonstrate the feeding arteries as compared to conventional angiography. Our results indicate that multiview 3D-TOF enhanced MRA non-invasively provides important information about the topographic relationship between tumour mass and the surrounding vasculature.

Intracranial black-blood MR angiography with high-resolution 3D fast spin echo.

Three-dimensional fast spin-echo (3DFSE) techniques are promising for black-blood imaging of cerebral vessels. In this study, flow-related signal dephasing was demonstrated as the primary mechanism for blood signal attenuation. Parameter optimization of TR (1500 to 3000 ms), receiver bandwidth (25 to 31.25 kHz), effective TE (25.7 to 30.1 ms), and ETL (7 to 8) was accomplished by making measurements of vessel-to-tissue contrast-to-noise ratios on vessels. A comparison of high-resolution 3DFSE and 3DTOF magnetic resonance angiography demonstrated that 3DFSE can generate images with equivalent or better small vessel detail than conventional techniques. 3DFSE black-blood techniques may provide improved sensitivity of small arteries and veins with slow or in-plane flow and immunity to flow-related distortions. Future studies with optimized parameters will determine the clinical efficacy of this technique.

2D-TOF MRA Follow-up Study of Percutaneous Transluminal Angioplasty for Severely Stenotic Cervical Internal Carotid Artery

Percutaneous transluminal angioplasty (PTA) for severe arteriosclerotic stenosis in the cervical internal carotid artery (ICA) was successfully carried out in 23 cases between December 1994 and August 1996. In order to analyze the condition of the cervical ICA in the early stage after PTA, 12 stenotic lesions of 11 cases were exposed to follow-up study of stenotic cervical ICA after PTA with magnetic resonance angiography (MRA) 1 to 150 days postoperatively. In six lesions, the diameter of the cervical ICA was dilated sequentially. In another four lesions, the diameter of the cervical ICA was decreased in the first three weeks and dilated over the next three weeks. Angiographically, these lesions had a small intimal flap at the balloon dilated portion, which was speculated to cause the turbulent flow in the first stage. In the remaining 2 lesions, restenotic changes in cervical ICAs were observed within three weeks after PTA. Follow-up angiography was performed over three months after PTA in five cases of this series and compared with MRA. Consequently, the diameters of the cervical ICA between angiography and MRA were closely correlated. The evaluation of the lesion after PTA of the cervical ICA demonstrated that MRA is beneficial, but within three weeks after PTA, caution should be paid for underestimation of the small intimal flap on MRA.

Magnetic Resonance Angiography of Hemodialysis Fistulas and Grafts

This chapter describes the use of magnetic resonance (MR) angiography for the evaluation of hemodialysis shunts. The specific sequences and results with this technique are described herein. The author states that a single contrast 3D-TOF MR angiography may be sufficient to depict and grade lesions on dialysis fistulas, and may be used for tests for shunt dysfunction.

Evaluation of the effects of intravascular MR contrast media (gadolinium dendrimer) on 3D time of flight magnetic resonance angiography of the body.

The aims of this preliminary study were to establish the efficacy and minimum effective dose of TG(5)(FdDO3A)(52) gadolinium dendrimer for contrast-enhanced, three-dimensional (3D) time of flight (TOF) magnetic resonance angiography (MRA) of the body. In a dose ranging study in eight rabbits (Group A), each of two animals received 0.03; 0.02; 0.01; or 0.005 mmol/kg of the agent for 3D-TOF MRA of the pelvic circulation in the axial and coronal planes. An additional nine animals (Group B) received a dose of 0.02 mmol/kg for 3D-TOF MRA of the mediastinum, abdomen or of the lower limbs. Quantitative and qualitative analyses of the images from Group A demonstrated a dose-related reduction in saturation effects and improved visualization of vascular structures, with maximal augmentation of the contrast-to-noise ratio (CNR) at 0.03 mmol/kg. The dose of 0.02 mmol/kg was found to be the minimal effective dose at the three vascular regions.