TOF Magnetic Resonance Angiography Research Articles

Assessment of large-scale imaging practices in patients with acute brain hemorrhage in French emergency departments: Emergency imaging practices in hemorrhagic stroke

ObjectiveIntracerebral hemorrhage (ICH) is a life-threatening condition, where imaging plays a crucial role but remains poorly standardized. Our main objective was to analyze the imaging protocols used during the acute phase of ICH and ascertain the proportion of patients diagnosed with secondary hemorrhage. Patients and methodsA multicenter retrospective observational study was conducted across over 100 French hospitals affiliated with a national tele-imaging network dedicated to emergency imaging. Among patients managed in the “Stroke Alert” pathway for suspected acute stroke from March 2021 to April 2023, those with ICH diagnosed within 24 h of symptoms onset were identified. Their imaging reports were reviewed to identify the imaging modality used and protocols performed and investigate whether a secondary cause was identified. ResultsOf the 18,356 patients included in the ”Stroke Alert” pathway, 662 cerebral hemorrhages were identified (3.6 %). Computed tomography (CT) was the most widely used imaging modality in the acute phase (71.8 % of examinations). Vascular imaging was performed in 78 % of patients with cerebral hemorrhage, most often CT angiography or TOF magnetic resonance angiography. A secondary cause was identified in 8.2 % (54/662) of cerebral hemorrhages, including vascular imaging in the vast majority of cases (92.6 %). ConclusionOptimization and standardization of imaging protocols in the acute phase of ICH is essential to improve the detection of its secondary causes, particularly vascular, requiring urgent treatment. Vascular imaging improves their early detection.

Usefulness of silent magnetic resonance angiography (MRA) for the diagnosis of atherosclerosis of the internal carotid artery siphon in comparison with time-of-flight MRA

Background and purposeFlow visualization in 3D time-of-flight MRA (3D-TOF MRA) may be limited for internal carotid artery siphon owing to turbulent artifact. The purpose of this study was to compare the usefulness of Silent MRA and 3D-TOF MRA to assess atherosclerosis of the internal carotid artery siphon.Material and methodsA total of 106 patients with suspected cerebrovascular disease were included. All patients were scanned with Silent MRA and 3D-TOF MRA sequences and also underwent DSA examination. Two observers independently assessed the TOF MRA and Silent MRA images of atherosclerosis of the internal carotid artery siphon. The diagnostic efficacy of two MRA methods in evaluating atherosclerosis of the carotid siphon was performed by using receiver operating characteristic (ROC) curve analysis. Interobserver reliability was also assessed using weighted kappa statistics.ResultsImage of Silent MRA sequence had higher subjective evaluation scores and significantly high CNR between the carotid siphon and the background tissues than the image of 3D-TOF MRA sequence (P < 0.05). The AUC was 0.928 (95% CI 0.909–0.986) for Silent MRA, which was significantly higher than that of 3D-TOF MRA (0.671, 95% CI 0.610–0.801, P < 0.05). Silent MRA had high sensitivity, specificity and accuracy than 3D-TOF MRA for visualization of the carotid siphon.ConclusionsSilent MRA as a new angiographic modality is superior to 3D-TOF MRA for visualization of the carotid siphon, and maybe an alternative to 3D-TOF MRA in the diagnosis of atherosclerosis of the carotid siphon.

Improved detection and characterization of arterial occlusion in acute ischemic stroke using contrast enhanced MRA

Background and purposeTo compare the accuracy and utility of contrast enhanced magnetic resonance angiography (MRA) (CEMRA) to Time of Flight MRA (TOF MRA) during detection and evaluation of occlusions on patients diagnosed with acute ischemic stroke (AIS). MethodsThis single-center study was approved by our local institutional research ethics board. From August 2014 to July 2016, 131 consecutive adult patients with confirmed AIS were included. Detection of an arterial occlusion and its characterization were evaluated independently with CEMRA or TOF MRA by two blinded neuroradiologists, then by consensus using all available MR sequences. A Cohen's Kappa coefficient (κ) and intra-class correlation coefficients (ICC) were used to compare the two techniques. ResultsThere was substantial concordance in the detection of arterial occlusion between CEMRA and TOF MRA (κ = 0.75). TOF MRA was more likely to show an arterial occlusion than CEMRA (63 versus 52 patients respectively). There were 13 and 1 false positive arterial occlusion with TOF MRA and CEMRA respectively, and 1 false negative with TOF MRA. There was excellent concordance between the location of arterial occlusions and CEMRA and TOF MRA [κ = 0.89 (0.72–0.97)]. CEMRA was significantly more likely to allow measurement of the thrombus than was TOF MRA [38 (75%) versus 14 (22%)] (P < 0.0001). ConclusionsOur study showed that CEMRA imaging detected arterial occlusions better than TOF MRA in AIS patients and more precisely such that thrombus length and location could be known, which improves the patient's management and care.

Magnetic Resonance Angiography in the Diagnosis of Cerebral Arteriovenous Malformation and Dural Arteriovenous Fistulas: Comparison of Time-Resolved Magnetic Resonance Angiography and Three Dimensional Time-of-Flight Magnetic Resonance Angiography.

BackgroundTraditional digital subtraction angiography (DSA) is currently the gold standard diagnostic method for the diagnosis and evaluation of cerebral arteriovenous malformation (AVM) and dural arteriovenous fistulas (dAVF).ObjectivesThe aim of this study was to analyze different less invasive magnetic resonance angiography (MRA) images, time-resolved MRA (TR-MRA) and three-dimensional time-of-flight MRA (3D TOF MRA) to identify their diagnostic accuracy and to determine which approach is most similar to DSA.Patients and MethodsA total of 41 patients with AVM and dAVF at their initial evaluation or follow-up after treatment were recruited in this study. We applied time-resolved angiography using keyhole (4D-TRAK) MRA to perform TR-MRA and 3D TOF MRA examinations simultaneously followed by DSA, which was considered as a standard reference. Two experienced neuroradiologists reviewed the images to compare the diagnostic accuracy, arterial feeder and venous drainage between these two MRA images. Inter-observer agreement for different MRA images was assessed by Kappa coefficient and the differences of diagnostic accuracy between MRA images were evaluated by the Wilcoxon rank sum test.ResultsAlmost all vascular lesions (92.68%) were correctly diagnosed using 4D-TRAK MRA. However, 3D TOF MRA only diagnosed 26 patients (63.41%) accurately. There were statistically significant differences regarding lesion diagnostic accuracy (P = 0.008) and venous drainage identification (P < 0.0001) between 4D-TRAK MRA and 3D TOF MRA. The results indicate that 4D-TRAK MRA is superior to 3D TOF MRA in the assessment of lesions.ConclusionCompared with 3D TOF MRA, 4D-TRAK MRA proved to be a more reliable screening modality and follow-up method for the diagnosis of cerebral AVM and dAVF.

Serbian

Intracranial aneurysm is a focal, abnormal dilation of an artery of the brain. Magnetic resonance angiography (MRA) is a non-invasive technique for vascular imaging and is thus widely used for screening for intracranial vascular lesions. The aim of the study was to show the diagnostic accuracy of 3D Time-of-Flight (3D TOF) MRA in the detection of unruptured cerebral aneurysms with the use of digital subtraction angiography (DSA) as the gold standard. A total of 2.612 consecutive patients underwent 3DTOF MRA. It showed unruptured aneurysms in 94 (3.6%) patients. They included 68 women and 26 men ranging in age from 29 to 76 years (mean, 52.5 years). Twenty-six of them, 20 women and 6 men, underwent DSA. The Mann-Whitney U test was used for the correlation of size. Fisher’s test was used for the correlation of location. The statistical level of significance was set at p 0.05) of aneurysms between TOF MRA and DSA. MRA is an accurate and non-invasive method for diagnosis of unruptured intracranial aneurysms. The results of study show the compatibility of MRA findings, the location and the size of an aneurysm in comparison with the “gold standard” cerebral DSA. Acta Medica Medianae 2015;54(3):12-18.

Image quality improvement in three-dimensional time-of-flight magnetic resonance angiography using the subtraction method for brain and temporal bone diseases

BackgroundTime-of-flight (TOF) magnetic resonance (MR) angiography is based on flow-related enhancement using the T1-weighted spoiled gradient echo, or the fast low-angle shot gradient echo sequence. However, materials with short T1 relaxation times may show hyperintensity signals and contaminate the TOF images. The objective of our study was to determine whether subtraction three-dimensional (3D) TOF MR angiography improves image quality in brain and temporal bone diseases with unwanted contaminations with short T1 relaxation times. MethodsDuring the 12-month study period, patients who had masses with short T1 relaxation times noted on precontrast T1-weighted brain MR images and 24 healthy volunteers were scanned using conventional and subtraction 3D TOF MR angiography. The qualitative evaluation of each MR angiogram was based on signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and scores in three categories, namely, (1) presence of misregistration artifacts, (2) ability to display arterial anatomy selectively (without contamination by materials with short T1 relaxation times), and (3) arterial flow-related enhancement. ResultsWe included 12 patients with intracranial hematomas, brain tumors, or middle-ear cholesterol granulomas. Subtraction 3D TOF MR angiography yielded higher CNRs between the area of the basilar artery (BA) and normal-appearing parenchyma of the brain and lower SNRs in the area of the BA compared with the conventional technique (147.7 ± 77.6 vs. 130.6 ± 54.2, p < 0.003 and 162.5 ± 79.9 vs. 194.3 ± 62.3, p < 0.001, respectively) in all 36 cases. The 3D subtraction angiography did not deteriorate image quality with misregistration artifacts and showed a better selective display of arteries (p < 0.0001) and arterial flow-related enhancement (p < 0.044) than the conventional method. ConclusionSubtraction 3D TOF MR angiography is more appropriate than the conventional method in improving the image quality in brain and temporal bone diseases with unwanted contaminations with short T1 relaxation times.

Non-contrast 3D time-of-flight magnetic resonance angiography for visualization of intracranial aneurysms in patients with absolute contraindications to CT or MRI contrast

The preoperative evaluation of patients with intracranial aneurysms typically includes a contrast-enhanced vascular study, such as computed tomography angiography (CTA), magnetic resonance angiography (MRA), or digital subtraction angiography. However, there are numerous absolute and relative contraindications to the administration of imaging contrast agents, including pregnancy, severe contrast allergy, and renal insufficiency. Evaluation of patients with contrast contraindications thus presents a unique challenge. We identified three patients with absolute contrast contraindications who presented with intracranial aneurysms. One patient was pregnant, while the other two had previous severe anaphylactic reactions to iodinated contrast. Because of these contraindications to intravenous contrast, we performed non-contrast time-of-flight MRA with 3D reconstruction (TOF MRA with 3DR) with maximum intensity projections and volume renderings as part of the preoperative evaluation prior to successful open surgical clipping of the aneurysms. In the case of one paraclinoid aneurysm, a high-resolution non-contrast CT scan was also performed to assess the relationship of the aneurysm to the anterior clinoid process. TOF MRA with 3DR successfully identified the intracranial aneurysms and adequately depicted the surrounding microanatomy. Intraoperative findings were as predicted by the preoperative imaging studies. The aneurysms were successfully clip-obliterated, and the patients had uneventful post-operative courses. These cases demonstrate that non-contrast imaging is a viable modality to assess intracranial aneurysms as part of the surgical planning process in patients with contrast contraindications. TOF MRA with 3DR, in conjunction with high-resolution non-contrast CT when indicated, provides adequate visualization of the microanatomy of the aneurysm and surrounding structures.

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.

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.

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.

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.

Impact of Mouse Strain Differences in Innate Hindlimb Collateral Vasculature

To assess the importance of genetic background for collateral artery development. C57BL/6, BALB/c and 129S2/Sv mice were studied after femoral artery ligation by laser Doppler imaging, visible light oximetry, time-of-flight-magnetic resonance imaging, and treadmill testing; C57BL/6 and BALB/c also underwent electron paramagnetic resonance (EPR) oximetry, x-ray angiography, and histology. C57BL/6 had the least initial distal ischemia and most complete recovery. BALB/c had the most severe initial ischemia and poorest recovery. BALB/c had some vasodilatory reserve in their ligated limbs not seen in the other strains at 3 weeks. By in vivo TOF-magnetic resonance angiography, C57BL/6 had larger preexistent and developed collaterals. By x-ray angiography, C57BL/6 had a higher collateral-dependent filling score and number of visible collaterals immediately after femoral ligation and a higher number of visible collaterals at 1 week but not at 4 weeks. EPR oximetry and histology revealed hypoxia and tissue damage in regions of collateral growth of BALB/c but not C57BL/6 mice. In C57BL/6 BrdUrd uptake in the thigh was limited to larger vessels and isolated perivascular cells. Proliferative activity in collateral arterioles was similar in both strains. Genetic differences in preexistent collateral vasculature can profoundly affect outcome and milieu for compensatory collateral artery growth after femoral artery occlusion.

MR angiography of the intracranial vessels: technical aspects and clinical applications

Evaluation of the intracranial circulation provides valuable information in the diagnosis and prognosis of various intracranial abnormalities and may influence patient management. Technical advances in magnetic resonance angiography (MRA) have improved the accuracy of this technique in various clinical situations, such as aneurysms, arterial and venous steno-occlusive diseases, vascular malformations, inflammatory arterial diseases, preoperative assessment of the patency of dural sinuses, and congenital vascular abnormalities. In many centers, MRA has replaced conventional digital subtraction angiography in screening for intracranial vascular disease, because of its non-invasive and non-ionizing character. Several MRA techniques have been developed for the imaging of the intracranial vascular system, such as time-of-flight MRA (TOF MRA), phase-contrast MRA (PC MRA), and more recently contrast-enhanced MRA (CE MRA). In the evaluation of steno-occlusive disease, the three-dimensional (3D) TOF-MRA technique is recommended for arterial evaluation, and the 2D TOF or 2D PC-MRA technique for venous evaluation. For the evaluation of aneurysms and arteriovenous malformations (AVMs), we recommend the 3D CE-MRA technique, especially dynamic sequences in case of AVM. In this review, the technical aspects, limitations, and optimization of these MRA techniques will be discussed together with their indications in intracranial disease.

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.

Pilot study of noninvasive detection of venous occlusions from central venous access devices in children treated for acute lymphoblastic leukemia.

Survivors of childhood acute lymphocytic leukemia (ALL) are at risk of venous occlusion induced by central venous access devices (CVADs). A sensitive, noninvasive screening technique to identify the magnitude of this problem is needed. Ultrasound (US) cannot always adequately image the innominate veins or the superior vena cava. Magnetic resonance angiography (MRA) can be noninvasive and may be useful for screening these patients. We examined the suitability of US and MRA to identify venous occlusion. We used MRA and ultrasound to examine 11 pediatric patients previously treated for ALL. CVADs had been in place a median of 2.5 years (range, 0.4-2.8 years) and removed a median of 2.1 years (range, 0.6-2.9 years) previously. We also performed 2D time-of-flight magnetic resonance angiography (TOF MRA) on two healthy young adult women with no history of venous abnormality or CVAD use. MRA suggested central venous abnormalities in 8 of the 11 ALL survivors and in both healthy control subjects. US results were negative in all 11 survivors. Further investigation is warranted to develop a sensitive and specific noninvasive method for identifying venous occlusion caused by prior CVAD use. Such a method would allow prospective studies of this complication in pediatric ALL survivors.

MR angiography and MR imaging of symptomatic vascular malformations

Purpose: To define the appearance of peripheral vascular malformations at magnetic resonance angiography (MRA) and assess the role of magnetic resonance imaging (MRI) and MRA in the investigation of these lesions. Patients and methods: Fourteen patients (aged 8–51 years) with clinical evidence of a vascular malformation were referred for MRI and MRA, performed on a 0.5 T GE Vectra superconducting system (International General Electric, Slough, UK). Multisection T1-weighted spin-echo and T2-weighted fast spin-echo pulse sequences were performed, with an inversion recovery fast spin-echo sequence in two cases. Two-dimensional time of flight (2-D TOF) and/or 2-D phase contrast (PC) MRA was performed in 13 cases. Eleven patients had digital subtraction angiography (DSA) using a Phillips Integris V3000 digital angiographic unit. The findings at MRA and MRI were compared with the catheter angiograms, and the effective diagnostic input of MRA and MRI was determined. Results: MRA demonstrated major feeding vessels and multiple intra-lesional vessels in relation to the high flow lesions, features absent in the low flow lesions. However, small feeding vessels to the AVMs were not clearly identified. MRI gave a clear demonstration of the anatomical extent of all lesions. AVMs ( n = 6) and venous malformations ( n = 6) were reliably distinguished, the former containing multiple serpentine signal voids on T1- and T2-weighted imaging, the latter being hyperintense to fat on T2-weighted images. Two other high-flow lesions diagnosed clinically as vascular malformations appeared solid on MRI, and were diagnosed histologically as a carotid body tumour and an angiomyolipoma. Conclusion: Although 2-D TOF MRA can distinguish AVMs from venous malformations, the technique adds little extra practical information to the diagnostic process, and cannot compete with catheter angiography for the detailed demonstration of AVM feeding vessels. These lesions can also be characterized using spin-echo sequences, though the primary role of MRI is to demonstrate their anatomical extent.

Experience of 3D TOF Magnetic Resonance Angiography in India .

The morbidity and discomfort following catheter insertion and contrast medium injection during invasive angiogram led to the use of an alternative noninvasive angiographic technique. This article reviews the initial results and applications of three-dimensional time of flight (3D TOF) singal volume MR imaging of the blood vessels of the head and neck regions. By using the (3D TOF)single volume technique, the MR angiograms were acquired in 10 min and portrayed blood flow in all majorarteries and veins. Arterlovenous malformations, aneurysms, obstructed cerebral vessels and the patency of a highly stenotic internal carotoid artery were demonstrated.

3D TOF MRA: role in evaluation of intracranial aneurysms following embolization with platinum coils

Several patients with intracranial aneurysms at our hospital have recently been treated with embolization of the aneurysm itself with detachable platinum coils. This has been done as part of a multicenter trial of GDC platinum coils. We report our experience in the follow-up of these patients with magnetic resonance (MR) after the embolization procedure. We present several illustrative cases and discuss the information that can be gained from the spin-echo images, the magnetic resonance angiography (MRA) source data, and the maximum intensity projection (MIP) reconstructions. We also examine the relative merits and limitations of MR in this role including thrombus formation, susceptibility artifact, and estimation of size and morphology of the aneurysms. We discuss the role of MRA in the planning of the embolization procedure.