Magnetic resonance angiography in patients with acute stroke treated by local thrombolysis

Although magnetic resonance angiography (MRA) is accepted for showing chronic intracranial stenotic or occlusive lesions, the method has not been practically examined in patients with acute cerebral ischaemia. We carried out three-dimensional time-of-flight MRA in six patients with acute ischaemia treated by local thrombolysis, and compared the findings with those of digital subtraction angiography (DSA). In all patients, MRA before thrombolysis clearly demonstrated the occluded arteries, which corresponded precisely to those shown by DSA. In four patients with complete recanalisation of the occluded vessels after thrombolysis, the recanalisation could be demonstrated by postoperative MRA. In one patient with reocclusion of the recanalised artery, repeat MRA also demonstrated the reocclusion, confirmed by DSA. These results suggest that MRA may be helpful for noninvasive investigation before and after thrombolysis. Received: 10 September 1997 Accepted: 17 January 1998     

MR angiography of steno-occlusive lesions of intracranial arteries: a comparative study between turbo MRA and conventional MRA]

PURPOSE: To compare the quality and diagnostic accuracy of images of intracranial steno-occlusive lesions obtained by conventional MRA and turbo MRA reconstructed using the zero-filled interpolation technique in the slice-select direction. MATERIALS AND METHODS: Eighteen patients with suspected steno-occlusive lesions of the intracranial arteries were studied with two types of three-dimensional time-of-flight angiography and conventional digital subtraction angiography. In total, 45 steno-occlusive lesions were quantitatively measured using calipers and correlated with DSA stenosis. A phantom that simulated vessels with stenosis was also imaged using the two types of MRA under the same conditions as those employed in the clinical study. RESULTS: Compared with conventional MRA, turbo MRA reduced the jaggedness of vessels and offered appearances more similar to those of DSA in the antero-posterior and lateral views. The severity of stenosis was classified into five grades based on the percentage of occlusion: not significant (0-24%), mild (25-49%), moderate (50-74%), severe (75-99%), and occlusive (100%). Neither turbo MRA nor conventional MRA showed any discrepancy from DSA above grade-1 stenosis. CONCLUSION: The advantage of turbo MRA is its ability to reduce the jaggedness of vessels on conventional MRA, and to simplify the recognition of vessel contours without prolonging acquisition time. Turbo MRA and conventional MRA have equally high diagnostic accuracy for steno-occlusive lesions.     

Magnetic resonance angiography of extracranial carotid and vertebral arteries,including their origins: comparison with digital subtraction angiography

Summary Although carotid bifurcation stenoses are not the only lesions of the extracranial cerebral arteries, magnetic resonance angiographic (MRA) studies to date have concentrated on the carotid bifurcation. We compared digital subtraction angiography of the extracranial portions of the cerebral arteries with MRA using an ordinary body coil, the time-of-flight method, and multiple transverse slabs which covered the arteries down to the aortic arch. Twenty-two patients (15 with arteriosclerotic diseases, 4 with aortitis, and 3 with tumours) had MRA using a 1.5 T magnet system with a three-dimensional fast imaging with steady state precession (FISP) technique. Thirty-nine carotid and 39 vertebral arteries were assessed by three radiologists with regard to stenoses or occlusions, graded as normal, mild (<30%), moderate (30–60%) or severe (>60%) stenosis, or occluded. Grading corresponded well in 81%; stenoses appeared more marked on MRA in 14% and were seen less clearly on MRA in 5%. When 26 carotid bifurcations were assessed separately, grading corresponded well in 95%. MRA is the only method which can display the whole course of the extracranial carotid and vertebral arteries non-invasively and satisfactorily.     

Accuracy of pre- and postcontrast 3D time-of-flight MR angiography in patients with acute ischemic stroke: correlation with catheter angiography

BACKGROUND AND PURPOSE: 3D time-of-flight (TOF) MR angiography (MRA) is insensitive to slow flow; however, the use of MR imaging contrast agents helps to visualize slow-flow vessels and avoids overestimation of vascular occlusion. The purpose of this study was to correlate pre- and postcontrast 3D TOF MRA with the results of conventional angiography during endovascular reperfusion therapy and to determine the accuracy of postcontrast 3D TOF MRA. MATERIALS AND METHODS: Thirteen patients who underwent endovascular reperfusion therapy for acute ischemic stroke were retrospectively analyzed. MR imaging techniques included single-slab 3D TOF MRA with and without contrast, as well as perfusion-weighted imaging. Angiography during reperfusion therapy was used as a standard of reference. Affected arteries were divided into segments either proximal or distal to the lesion, and pre- and postcontrast MRA signals were graded as absent, diminished or narrowed, or normal. RESULTS: In 2 of 5 patients with arterial stenosis and 6 of 8 patients with complete occlusion, MRA signal intensity proximal to each lesion was absent, indicating a proximal pseudo-occlusion on precontrast MRA. Postcontrast MRA demonstrated an arterial signal intensity proximal to the stenotic or occlusive lesions in all 13 patients. Arterial signal intensity distal to the occlusion was identified on postcontrast MRA in 7 of 8 patients having complete occlusion, and the extent of occlusion on postcontrast MRA was similar to results of conventional angiography. CONCLUSION: In this small series, postcontrast 3D TOF MRA more accurately delineated the extent of stenotic or occlusive arterial lesions than precontrast MRA.     

CT angiography in the assessment of carotid artery atherosclerosis

Objective: The aim of the study was to evaluate the ability of CT angiography (CTA) to detect atherosclerosis of the carotid arteries in comparison with 3D time-of-flight MR angiography (3D TOF MRA), using contrast angiography and intravascular ultrasound (IVUS) as a reference.Material and Methods: Contrast angiography and CTA were performed in 31 patients (mean age 65 years, range 45-79). The image quality was evaluated, atherosclerotic lesions were registered, and diameter stenosis degree was visually estimated from axial source images of CTA and 3D TOF MRA (21 patients), and results of interpretations were compared. The comparison of quantitative measurements was performed using IVUS as a reference.Results: Contrast angiography detected 51 lesions (mean diameter stenosis 50%, range 10-100%), and CTA detected all same lesions. CTA provided better image quality and consistency of image interpretation than 3D TOF MRA. IVUS verified 29 atherosclerotic lesions with a mean diameter stenosis of 35%, (range 4-40%). CTA yielded a sensitivity of 96% to 100% (≤10% or ≤20% diameter stenosis regarded as normal) for the detection of lesions with reference to IVUS.Conclusion: CTA seems feasible and accurate for the detection of atherosclerosis in carotid arteries.     

蛛网膜下腔出血患者的MRA和DSA的对照研究

目的：研究ＭＲ血管造影（ＭＲＡ）在蛛网膜下腔出血（ＳＡＨ）患者病因诊断中的应用准确性和可靠性。材料和方法：回顾性分析３３例ＳＡＨ患者的ＭＲＡ资料，并与ＤＳＡ作了对比分析，ＭＲＡ采用三维时间流逝（３Ｄ－ＴＯＦ）法。结果：ＭＲＡ上显示了２６例血管病变中的２２例，包括１５个动脉瘤中的１３个，８例动静脉畸形中的６例和３例血管狭窄闭塞性病变。１个完全血栓形成的右颈内动脉瘤ＭＲＡ上未显示。但常规ＭＲＩ和ＭＲＡ原始图像上显示，ＭＲＡ结合ＭＲＩ和ＭＲＡ原始图像可以对９１％的患者做出正确诊断和评价，动脉瘤和周围血管的关系及ＡＶＭ的供血动脉和畸形结节能在ＭＲＡ上被准确评价。结论：作为一种非损伤性的血管成像方法，ＭＲＡ具有安全、可靠和方便的优点，可以做为常规用于ＳＡＨ患者的筛选检查。     

Contrast-enhanced subtraction MR angiography in occlusive disease of the pelvic and lower limb arteries: results of a prospective intraindividual comparative study with digital subtraction angiography in 76 patients.

PURPOSE: The purpose of this work was to evaluate the feasibility and clinical use of MR angiography (MRA) for examining the pelvic and lower limb arteries in patients with arterial occlusive disease. METHOD: Seventy-six patients with clinical signs of peripheral arterial occlusive disease were included in the study. MRA was performed using a fast contrast-enhanced high-resolution 3D technique that covered the area from the distal abdominal aorta to the distal lower limbs in two examination steps. RESULTS: In all patients, diagnostic images comparable with those of conventional intraarterial digital subtraction angiography (DSA) could be obtained. No false-negative findings were seen in the iliac, femoral, or popliteal arteries. Ten to 16% of the mild stenoses and 6-14% of the severe stenoses, mainly in the crural vessels, were overgraded compared with intraarterial DSA. Particularly in patients with proximal severe obstructions or occlusions, the crural segments could be depicted more clearly due to decreased arterial runoff in conventional angiography. CONCLUSION: The consistency of the excellent depiction of the vascular territories of the distal aorta and the pelvic and lower limb arteries in a standardized setting suggests great potential for the use of MRA in the primary diagnosis of peripheral arterial occlusive disease.     

Intra-arterial MR angiography in the iliac system: initial clinical experience with 25 patients

The aim of this study was to evaluate intra-arterial magnetic resonance angiography (MRA) of the iliac arteries. Therefore, 25 consecutive patients (17 male, 8 female) suffering from symptomatic occlusive disease of the lower limbs were investigated prospectively. Catheter angiography was performed before MRA and served as the standard of reference. Contrast-enhanced intra-arterial MRA was performed using a 1.5 Tesla MRI system. Contrast agent (gadodiamide) was injected by a conventional pigtail-shaped angiography catheter placed in the abdominal aorta. Vascular lesions were assessed by four investigators. The degree of stenosis was compared with the findings of conventional catheter angiography. Additionally, the diagnostic quality of the MR angiograms was assessed by the investigators using a semi quantitative five-point scale. All lesions shown by catheter angiography were detected and correctly localized by intra-arterial MRA. MR angiograms exhibit a specificity of 95% and a sensitivity of 96% for stenoses of 50% or more. The diagnostic quality of the images was judged from good to excellent, on average. Intra-arterial MRA exhibits a specificity and sensitivity comparable with intravenous angiography. The image quality appears to be adequate for supporting MR-guided vascular intervention.     

下肢动脉慢性闭塞症的MRA诊断

目的：对ＭＲＡ在下肢动脉慢性闭塞症中的诊断价值作一初步评估。材料与方法：５４例下肢动脉慢性闭塞症患者，行二维时间飞跃法ＭＲＡ检查，范围包括主动脉下段、髂动脉、股动脉、动脉及其三分支。其中２１例同时行动脉造影，１８例手术探查。结果：２１例ＭＲＡ与动脉造影对照，可比动脉节段１６８个，其中正常或轻度狭窄４６个节段，中度狭窄２７段，重度狭窄４６段，闭塞４９段，两者符合率为９２．２６％（１５５／１６８）。１８例与手术对照，可比动脉节段８２个，符合率为９２．６８％（７６／８２）。同时进行的２３例双功能多普勒超声测定踝／肱指数显示，踝／肱指数＜０．５，ＭＲＡ显示血管为重度狭窄或闭塞。结论：下肢动脉ＭＲＡ与手术、动脉造影、踝／肱指数比较，具有很好的一致性，能比较准确地评价下肢动脉慢性闭塞性病变，尤其对重度狭窄和闭塞准确性较高。     

Magnetic resonance angiography of the carotid arteries using three different techniques: accuracy compared with intraarterial x-ray angiography and endarterectomy specimens

PURPOSE: To compare three different magnetic resonance angiography (MRA) techniques with x-ray angiography and endarterectomy specimens. MATERIALS AND METHODS: Twenty-one patients underwent x-ray angiography, three-dimensional time-of-flight (TOF) focusing on the carotid bifurcation, high-resolution (HR) contrast-enhanced (CE) MRA, and time-resolved CE MRA. Stenoses of internal carotid arteries were evaluated by three independent observers on identical projection of x-ray angiography and MRA. Maximum stenosis grades on MRA were assessed additionally and correlated with endarterectomy specimens in 12 cases. RESULTS: Sensitivity for the detection of severe stenoses was excellent (100%) for all MRA techniques, and specificity was superior for three-dimensional TOF (96.7%) compared with HR CE MRA (80.6%) and time-resolved CE MRA (83.9%). The correlation between x-ray angiography and MRA for all stenoses was slightly superior for three-dimensional TOF and HR CE MRA compared with the time-resolved technique (kappa = 0.87 and 0.86 vs. 0.84). The same trend was seen for the interobserver agreement and for the correlation with endarterectomy specimens. Eleven up to 17 stenoses (depending on the MRA technique) were graded higher using additional projections. CONCLUSION: Three-dimensional TOF MRA yielded even more accurate results than HR CE MRA in grading of stenoses near the carotid bifurcation. Therefore, a combination of both methods seems to be advantageous.     

Intraarterial versus IV gadolinium injections for MR angiography: quantitative and qualitative assessment of the infrainguinal arteries

OBJECTIVE: Our purpose was to quantitatively and qualitatively compare 3D intraarterial (IA) gadolinium-enhanced MR angiography (IA MRA) versus the standard of reference of MR angiography, 3D IV gadolinium-enhanced MR angiography (IV MRA), in patients with peripheral arterial occlusive disease (PAOD) for use during catheter-based MR-guided endovascular interventions. CONCLUSION: IA MRA provides image quality of the infrainguinal arteries in PAOD patients comparable to IV MRA with a significantly improved assessment of the infrapopliteal arteries due to reduced venous contamination. Further benefits of IA MRA include usage of only very low doses of gadolinium and simplified bolus timing.     

Comparative assessment of helical CT-angiography, 2D TOF MR-angiography and 3D gadolinium enhanced MRA in aorto-iliac occlusive disease

PURPOSE: To compare helical CT-angiography (CTA) and two techniques of MR angiography (MRA) to conventional angiography in aorto-iliac occlusive disease. MATERIALS AND METHODS: The abdominal aorta and iliac arteries in 22 patients (4 for preoperative assessment of abdominal aortic aneurysm and 18 for peripheral vascular disease) were imaged using four techniques: digital subtraction angiography ("gold standard"), 2D TOF MR angiography, 3D Gd-enhanced MR angiography and helical CT angiography. Source (CTA and 2D TOF MRA) and MIPed images (after subtraction measures before and after gadolinium injection for 3D Gd-MRA) were reviewed. RESULTS: Sensitivity, specificity and accuracy for the detection of significant (>50%) stenosis and occlusion of aorto-iliac arteries were respectively: 38%, 89%, 77% for 2D TOF MRA; 75%, 71%, 72% for 3D Gd-MRA and 95%, 90%, 92% for CTA. Excluding the internal iliac arteries, results were 54%, 96%, 88% for 2D TOF MRA; 96%, 80%, 83% for 3D Gd-MRA and 92%, 93%, 95% for CTA. CONCLUSION: 3D Gd-MRA, a technique with potential for further improvement, is superior to 2D TOF MRA for detecting significant stenosis and occlusion of aorto-iliac arteries. Results at Gd-MRA are nearly similar to those at CTA (after excluding internal iliac arteries). Results at Gd-MRA are not affected by calcified plaque.     

MR angiography of the foot and ankle

To better understand the use of magnetic resonance angiography (MRA) in evaluating peripheral vascular disease, the authors studied arteries in the foot and ankle. Twenty patients with arterial occlusive disease of the lower extremity were studied with two-dimensional time-of-flight MRA, and the results were compared with those of 10 conventional x-ray arteriograms, four digital subtraction arteriograms, and three intraoperative arteriograms. The studies were reviewed and rated by three radiologists blinded to the patients' clinical history. Also, the first 16 patients were examined with MRA before and after intravenous injection of gadopentetate dimeglumine. The mean confidence levels for the reviewers' interpretations of the MRA studies were significantly higher than those for the conventional arteriograms for the medial plantar, lateral plantar, and plantar arch arteries of the feet (P ≦ 0.005). Postcontrast MRA images were inferior to precontrast images because of overlapping of veins and arteries. Time-of-flight MRA without gadolinium can serve as a useful complementary study for evaluating patients with peripheral vascular disease in the foot and ankle.     

Willis环磁共振血管成像与血管造影对比研究

目的：对比分析Ｗｉｌｌｉｓ动脉环的ＭＲＡ和ＣＡ表现,探讨ＴＯＦ法ＭＲＡ评价Ｗｉｌｌｉｓ环解剖与功能的价值。材料与方法：选择４３例颅脑血管和肿瘤疾病的ＴＯＦ法ＭＲＡ和ＣＡ资料。ＭＲＡ应用１．０Ｔ超导ＭＲ系统的３Ｄ或２ＤＦＩＳＰ序列扫描,原始血管图像用ＭＩＰ重建。ＣＡ西门子１２５０ｍＡＤＳＡ系统和岛津１０００ｍＡ造影造系统,采用Ｓｅｌｄｉｎｇｅｒ技术导管法股脑血管造（至秒摄取双侧颈动脉和一侧椎动脉造有     

Non-invasive vascular imaging of peripheral vessels

The purpose of this review is to describe recent advances in non-invasive vascular imaging techniques and to discuss their current clinical applications for imaging of peripheral vessels. Principles for applying ultrasound, CT angiography (CTA), and magnetic resonance angiography (MRA) for non-invasive imaging of peripheral arteries and veins are presented. Clinical applications are reviewed for different vascular diseases, therapy planning, and follow-up studies. Conventional Doppler and color duplex sonography are the most cost-effective procedures to detect or rule out peripheral arterial occlusive disease (PAOD) and to provide specific recommendations for therapy. In the near future, contrast-enhanced MRA (CE MRA) with additional axial two-dimensional time-of-flight studies to search for non-anatomic runoff will replace diagnostic intra-arterial digital subtraction angiography (DSA) for planning of reconstructive surgery with acquisition slabs displaying projections similar to intra-arterial DSA. Color duplex sonography should also be the first non-invasive technique applied for the detection of peripheral aneurysms. Preoperative or preinterventional therapy planning of aneurysms may be performed by CTA or CE MRA. Compression ultrasound is the imaging procedure of choice in deep venous thrombosis (DVT). In the preoperative assessment of venous incompetence, color duplex sonography is the imaging technique which is sufficient in most cases. Received: 5 March 1998; Accepted: 16 March 1998     

MR Angiography of the Lower Extremities with a Moving-Bed Infusion-Tracking Technique

Purpose: To assess the value of MR angiography (MRA) with automatic table movement in a consecutive series of patients with peripheral arterial disease. Methods: Seventy-two patients underwent both conventional angiography (CA) and MRA for peripheral arterial occlusive disease. Both techniques were scored in a masked way. Consensus scoring for CA was compared with MRA scoring per observer. If there was a discrepancy in scoring of a segment on MRA and CA, the images were reviewed and a consensus arrived at. Results: Observer A found 7.4% and observer B found 6.5% of the segments could not be analyzed on MRA. Observer A scored 11.4% dissimilar on MRA and CA, observer B 15.2%. In the aortoiliac arteries, this was mainly caused by stents and overestimation of stenoses; in the crural arteries it resulted from underestimation of the stenoses on MRA. Overall sensitivity and specificity for the aortoiliac, femoropopliteal and crural vessels were respectively 90% and 91%, 90% and 96%, 59% and 96% for observer A, and 85% and 91%, 84% and 89%, 68% and 85% for observer B. Conclusion: Although MRA of the lower extremities is a promising technique, improvements still need to be made. In particular, MRA below the knee is suboptimal for clinical use.     

Application of magnetization transfer at 3.0 T in three-dimensional time-of-flight magnetic resonance angiography of the intracranial arteries

PURPOSE: To apply magnetization transfer (MT) at 3.0 T in three-dimensional time-of-flight magnetic resonance angiography of the intracranial arteries. MATERIALS AND METHODS: This study was performed on phantoms and seven volunteers to determine the effects of MT at 3.0 T. By using a modulated MT approach and an altered phase encode order, the specific absorption rate (SAR) was kept below 3 W/kg over any 8-second time period. RESULTS: For a 20-degree flip angle and 36 msec repetition time, the background suppression at 3.0 T was improved with MT by 52 +/- 5% for white matter and 40 +/- 8% for grey matter, making the distal intracranial vasculature significantly more discernible. CONCLUSIONS: MT at 3.0 T can significantly improve background suppression in 3D time-of-flight magnetic resonance angiography (MRA) of the intracranial arteries without exceeding SAR guidelines.     

Three-dimensional magnetization-prepared time-of-flight MR angiography of the carotid and vertebral arteries

Three-dimensional magnetization-prepared (MP) MR angiography (MRA) was applied to the carotid and vertebral arteries by using ECG triggering, a slab selective RF inversion pulse, centric phase encoding and acquisition during diastole. Both theoretically and experimentally, the MP MRA sequence was shown to perform well in cases where there was substantial blood replenishment during the inversion time Tl (>330 ms). In comparison with standard, ungated, steady-state 3D time-of-flight MRA in 13 consecutive volunteers, the MP MRA images demonstrated better background suppression with less artifact and generally had more uniform vessel depiction. The MP MRA sequence was generally superior for portraying vessels exhibiting high pulsatility such as the carotid siphon. However, in distal vessels with slow flow and incomplete blood replenishment, the MP MRA technique was inferior due to increased loss of vessel signal. The reasons for this increased signal loss are identified and improvements to the MP MRA sequence are suggested.     

Contrast enhanced MR angiography in the assessment of relevant stenoses in occlusive disease of the pelvic and lower limb arteries: diagnostic value of a two-step examination protocol in comparison to conventional DSA.

Introduction/objectives: Contrast-enhanced MRA (ce-MRA) has been claimed by many authors as a replacement of conventional angiography evaluating peripheral arterial occlusive disease. However, reliable detection of relevant stenoses (>70%) has to be provided for planning vascular interventions. Only few data in the literature focuses on this crucial problem. The purpose of this study was to evaluate this topic using a two-step body-coil-based MRA protocol. Methods and patients: Forty three patients presenting with 82 stenoses >/=50% and 61 stenoses >70% on conventional catheter angiogram received fast Gadolinium-DTPA-enhanced high resolution 3D MR angiography at 1.5 T covering the pelvic and peripheral vascular tree in two examination steps using the body-coil. The data were evaluated double-blinded by three readers distinguishing moderate (50-70%) from severe stenoses (>70%). Results: Overall sensitivity/specificity/accuracy was 84/60/70% evaluating 143 segments. Specificity was rather poor in the iliac (58%) and crural (50%) region and moderate in the femoral and popliteal level (73%). The negative predictive value ranged between 78 and 91%. The grade of stenosis tend to be overestimated rather than underestimated in all levels with positive predictive values between 55 and 78%. Discussions and conclusions: Body-coil-based contrast-enhanced MRA has limited potential in distinguishing moderate from severe stenoses in peripheral occlusive disease. Overestimations are more common than underestimations. Both occur mainly in small-sized crural arteries but also in larger iliac arteries where vessel course in partition direction may cause inadequacy between voxel size and lumen diameter in severe stenosis.     

Imaging of vascular pathology in hyperhomocysteinemic patients with digital subtraction angiography and magnetic resonance techniques

Mild hyperhomocysteinaemia (mHH) is an independent risk factor for premature arteriosclerosis. We investigated the accuracy in the detection of early arteriosclerotic lesions in such patients. The left and right wall of the abdominal aorta, the aortic bifurcation and both common iliac arteries were evaluated with gated T1-weighted magnetic resonance imaging (gT1 MRI) and gated two-dimensional (2D) time-of-flight magnetic resonance angiography (g2D-TOF MRA) and were compared with intra-arterial digital subtraction angiography (iaDSA) in 11 patients with arteriosclerosis and mHH. Six patients showed arteriosclerosis in one or more of the total number of 55 studied arterial segments with iaDSA. Thirty-two of 37 normal and 12 of 18 stenotic segments with gT1 MRI, and 29 normal and 6 stenotic segments with g2D-TOF MRA, were correctly classified. Sensitivity of gT1 MRI and g2D-TOF MRA versus iaDSA was 67 and 33 %, the specificity was 86 and 78 % and the accuracy was 80 and 64 %, respectively.We conclude that arteriosclerosis in patients with mHH is a regular finding, and gT1 MRI in such patients is an acceptable technique. Received 8 May 1996; Revision received 30 September 1996; Accepted 8 January 1997