脑血管疾病TOF法磁共振血流成像的初步探讨

笔者搜集了７０例诊断明确的脑血管疾病ＭＲＡ资料进行分析。其中２２例经Ｘ线脑血管造影证实。所有患者均进行了三维ＴＯＦ法ＭＲＡ扫描。结果表明，三维ＴＯＦ法能清楚地显示出脑动脉瘤、血管畸形、大动脉的狭窄和阻塞等血管病变，但由于饱和作用的影响，不能显示小动脉分支和静脉血管，并且在血管狭窄的显示方面存在着夸张作用和假象。与Ｘ线血管造影相比，ＭＲＡ虽具有成像迅速、无创伤等优点，但在小血管病变及血管狭窄的显示方面仍有不足。     

Cerebrovascular pathology. Comparison of magnetic resonance and magnetic resonance angiography]

After making the visualization of the intracranial circulation possible without contrast media, the radiologist is now evaluating the diagnostic role of the different techniques of MRA. Attempts are also being made to characterize the main patterns of intracranial vascular diseases. The authors examined, with 3D TOF MRA, 40 patients presenting with 50 vascular lesions on MRI scans. Twenty of 40 patients were also studied with angiography. Seventeen aneurysms were detected, together with 3 stenoses of the cerebral arteries, 13 arteriovenous malformations, 12 dolichobasilar arteries, 3 postoperative and 2 post-embolization controls. MRI was performed with a superconductive magnet (1.5 T), a dedicated coil and gradient-echo 3D TOF FT sequences. The refocused sequence for flux, FISP 3DFT, required the following parameters: TR = 0.04 s, TE = 10 ms, flip angle = 15 degrees, 256 x 256 matrix, 1 acquisition. The 64-80 mm volume along the axial plane was divided so that an actual 1-mm thickness was excited. In post-processing, the maximum-intensity projection was employed on the axial plane 0 degrees-90 degrees (15 degrees interval). In the various conditions, the results obtained with MRA were correlated and compared with MRI findings. MRA provided useful additional information in 27.4% of cases in the study of aneurysms, arteriovenous malformations, vascular occlusion and dolichobasilar arteries, as well as in the follow-up of these lesions. MRA is currently suggested in the evaluation of cerebral circulation and is considered a complementary technique to MRI. MRA is also to be used preliminary to angiography.     

The application of i.v. digital subtraction angiography to cranial disease in children

All intracranial IV digital subtraction angiographic examinations performed over the past 2 years were reviewed retrospectively to ascertain the uses and limitations of this technique for the evaluation of pediatric intracranial disease. Of the various abnormalities studied, this imaging technique was particularly useful in diagnosing venous and dural sinus abnormalities; in screening for suspected large aneurysms, vascular malformations, and major arterial occlusive disease; and in preoperative vascular mapping. IV digital subtraction angiography has selected usefulness in confirming brain death, in evaluating cerebral ischemia, in identifying vascular abnormalities underlying intracranial hemorrhage, and in evaluating vascularity and sinus extension of masses. The IV route for digital subtraction angiography is not useful in diagnosing segmental arterial occlusive or small-vessel disease, nor is it useful in preoperative localization of specific arterial supply to arterial venous malformations, aneurysms, or neoplasms. IV digital subtraction angiography can be performed successfully in children of all ages with minimal patient morbidity. For most patients, the diagnostic information obtained was adequate without the need for standard cerebral arteriography.     

Intracranial Magnetic Resonance Angiography

Intraarterial angiography remains the "gold standard" for the evaluation of the intracranial vasculature, but it carries with it the risks of local vascular damage, systemic reactions, transient neurologic deficits, permanent neurologic compromise, and even death. To date, magnetic resonance angiography (MRA) has been applied to a variety of different manifestations of intracranial vascular disease. Presently, MRA studies and flow measurement techniques serve to compliment the more traditional spin-echo evaluation of patients with small aneurysms, arterial and venous occlusions, vascular malformations, and in some cases of neoplastic vascular invasion. Practically, the limitations of these techniques must be taken into account such that the appropriate method is applied to answer a specific clinical question and the acquisition parameters are chosen to maximize the sensitivity and specificity of the study. The intent of this review is to summarize the technical approaches, clinical role, pitfalls, and potential improvements in the MRA techniques as they apply to the intracranial circulation.     

Contrast-enhanced three-dimensional MR angiography in the assessment of subclavian artery diseases

The purpose of this prospective study was to determine the potential diagnostic value of 3D breath-hold contrast-enhanced MRA (CEMRA) in the evaluation of subclavian artery pathology, and to compare CEMRA and digital subtraction angiography (DSA) findings. The study group included 50 patients with suspicion of subclavian artery pathology: 40 suspected steno-occlusive disease and 10 different vascular anomalies. The MRA examinations were performed on a 1.5-T system using fast 3D sequences. A fixed dose of 40 ml Gd-DTPA was administered at 2 ml/s after previous bolus tracking. Images were analyzed to assess: subclavian depiction; luminal changes; collateral branches; and feeders of arterial venous malformations (AVM). A multireader blinded fashion was used. The CEMRA revealed an optimal agreement with DSA findings in the different types of diseases. Sensitivity and specificity were 90 and 95 %, respectively, in detecting steno-occlusive disease (including functional and arteritic stenoses), and 100 and 100 %, respectively, in cases of vascular anomalies (dilation, kinking, anomalous origin and AVM). Contrast-enhanced MRA can be proposed as a non-invasive, robust technique for imaging subclavian pathologies with high diagnostic performance. Received: 18 May 1999; Revised: 5 January 2000; Accepted: 27 March 2000     

Characterisation of intracranial aneurysms with MR angiography

The purpose of this study was to compare the accuracy of 3D time-of-flight (TOF) acquisitions in the characterisation of intracranial aneurysms. Fourteen patients with aneurysms proven on intra-arterial angiography were first studied with a 3D TOF acquisition. When the aneurysms were incompletely demonstrated, additional MR angiography (MRA) acquisitions were performed, including black-blood MRA, 2D TOF, phase-contrast and contrast-enhanced TOF. 3D TOF MRA was sufficient for detection of the aneurysm in 13 of 14 cases and characterisation of the aneurysm was possible in 6. All the initial shortcomings of the TOF technique could be analysed and explained by means of additional MRA techniques. This study suggests that the combination of different MRA techniques offers new possibilities for noninvasive investigation of intracranial aneurysms.     

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。     

磁共振脑血管造影与数字减影血管造影的比较

通过对５５例脑血管磁共振血管造影（ＭＲＡ）和动脉数字减影血管造影（ＩＡ－ＤＳＡ）的对比分析，探讨了ＭＲＡ在颅内血管病变诊断中的可靠性。结果表明，ＭＲＡ可以对４８例患者做出正确诊断，结合常规ＭＲＩ和ＭＲＡ原始切层图像，其敏感性为９０．９％。对动脉瘤的敏感性为８７．５％，动静脉畸形为７８．６％。３例血管狭窄闭塞性病变和１例脑膜瘤患者的血管改变也与ＤＳＡ完全符合。可以认为，作为一种常规筛选工具，ＭＲＡ用于脑血管病变的检查和诊断，具有安全、可靠和方便的优点。     

PCA技术在颅内血管成像中的临床应用

目的扩大相位对比血管成像(PCA)技术在颅内血管成像中的临床应用,并与流人(Inflow)技术比较。方法46例颅内血管异常患(男34例,女12例,年龄3～60岁,平均年龄41．3岁)于临床症状出现后均经PCA与Inflow两种方法检查。本研究全部MR成像均采用PHILIPS GYROSCAN NT 1．0磁共振超导扫描机进行。两种成像方法的后处理均采用MIP重建。结果在46例颅内血管异常患中,PCA测出动静脉畸形20例,动脉瘤15例,海绵状血管瘤6例,单纯静脉瘤1例,以及静脉窦栓塞2例,只有2例海绵状血管瘤未测出,而Inflow相应地测出动静脉畸形18例,动脉瘤15例,海绵状血管瘤8例但静脉系血管畸形未测出1例。PCA与Infolw的检出率分别为95．6％(44／46)和86．9％(40／46)。结论虽然Inflow显示颅内血管异常与PCA有些相似,但它未能显示静脉系血管异常。相比之下,PCA能显示各种颅内血管异常,值得临床广泛应用。     

Diagnostic accuracy of 3D time-of-flight MR angiography compared with digital subtraction angiography for follow-up of coiled intracranial aneurysms: influence of aneurysm size

BACKGROUND AND PURPOSE: 3D time-of-flight MR angiography (3D TOF MRA) may be used as noninvasive alternative to digital subtraction angiography (DSA) for the follow-up of patients with intracranial aneurysms treated with Guglielmi detachable coils (GDCs). We aimed to determine the influence of aneurysm size and location on diagnostic accuracy of 3D TOF MRA for follow-up of intracranial aneurysms treated with GDCs. MATERIALS AND METHODS: Two hundred and one 3D TOF MRAs in 127 consecutive patients with 136 aneurysms were compared with DSA as standard of reference. Sensitivity and specificity of 3D TOF MRA for detection of residual or reperfusion of the aneurysms was calculated with regard to aneurysm size and location. RESULTS: Overall sensitivity and specificity of MRA was 88.5% and 92.9%, respectively. Sensitivity was lower for aneurysms 相似文献   

MR angiography in carotid stenosis: A comparison of three techniques

Purpose: To compare the accuracy of three different magnetic resonance angiography (MRA) techniques for studying steno-occlusive disease of carotid arteries. Methods: 64 patients were evaluated with three MRA techniques- three-dimensional (3D) time-of-flight (TOF), two-dimensional (2D) TOF, and 3D Phase-Contrast (PC); the acquisition was in the axial plane, the volume included the carotid bifurcation. Digital subtraction angiography (DSA) was considered the `gold standard'. The MRA images were reprojected with a maximum intensity pixel ray-tracing (MIP) algorithm. The three MRA techniques were blindly graded as normal, mildly stenotic (0–29%), moderately stenotic (30–49%), severely stenotic (70–99%), or occluded. Results: DSA provided 128 diagnostic judgments: 92 were negatives and 36 positives. 2D TOF was in agreement with angiography in 116 of 128 cases (90%), but overestimated the results in seven cases and underestimated in five cases. 3D TOF agreed with angiography in 125 of 128 cases (97%), with one overestimation and two under estimations. 3D PC was concordant in 116 of 128 cases (90%), overestimating in six cases, underestimating in six cases. The sensitivity, specificity and diagnostic accuracy for 2D TOF was, respectively 84%, 94%, and 92%, while for 3D TOF was 94%, 100%, and 98%, and for 3D PC 86%, 98%, and 95%. The comparison of the three different MRA techniques provided no statistically significant difference (Friedman test P<0.05). Conclusion: The high degree of diagnostic accuracy of MRA found in the study of the steno-occlusive disease of the carotid arteries confirms the high degree of reliability of this methodology carried out with the 3D TOF technique, compared to 2D TOF and 3D PC.     

Intracranial vascular malformations

Many efforts and much research have been dedicated to the field of non-invasive angiographic techniques in the past few years. Thanks first to magnetic resonance angiography (MRA) and subsequently to computed tomographic angiography (CTA), very interesting results have been obtained in the diagnosis of cerebrovascular diseases. Neck vessels are most successfully evaluated by both MRA and CTA, and the need for digital subtraction angiography (DSA) examinations in patients at risk for vascular occlusions has significantly decreased. The role and the diagnostic accuracy of these non-invasive modalities in intracranial vascular pathology is still under investigation, and several studies have been and are being performed. Both techniques have a better spatial resolution and sensitivity in detecting cerebrovascular malformations than DSA. In the diagnosis of cerebral aneurysms, both MRA and CTA – due to their high sensitivity – have become screening techniques in the population at risk for subarachnoid hemorrhage, these techniques may become basic diagnostic modalities in treatment planning. The results are less satisfying in the evaluation of brain arteriovenous malformations and in the different steps of pre- and post-therapeutic evaluation. Received 9 February 1998; Accepted 13 February 1998     

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

RATIONALE AND OBJECTIVES: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.     

Intracranial vascular stenosis and occlusion: comparison of 3D time-of-flight and 3D phase-contrast MR angiography

We compared the value of 3D time-of-flight (TOF) and phase-contrast (PC) MR angiography (MRA) for detection and grading of intracranial vascular steno-occlusive disease. Unenhanced 3D-TOF MRA and 3D-PC MRA (30–60 cm/s velocity encoding) were performed at the level of the circle of Willis in 18 patients, mean age 56 ± 10 years. Postprocessed images using a maximum-intensity projection reconstruction with multiple targetted projections were analysed. A total of 126 vessels was assessed by PC MRA and 143 by TOF MRA, with digital subtraction angiography (DSA) in 15 patients and/or transcranial Doppler sonography (TCD) in 18 as a standard. Two blinded readers reviewed the MRA, DSA and TCD examinations retrospectively. On DSA and/or TCD the two observers found 32 and 28 steno-occlusive lesions. 3D-TOF MRA was more sensitive than 3D-PC MRA (87 % and 86 % vs. 65 % and 60 %) and had a higher negative predictive value (96 % vs. 89 %). Correct grading of stenoses was achieved in 78 % by 3D-TOF and 65 % by 3D-PC MRA. Received: 24 September 1997 Accepted: 27 February 1998     

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     

磁共振脑静脉系血管成像技术及其临床应用

目的探讨磁共振脑静脉系血管成像的技术方法和最佳扫描方案，评价磁共振静脉系血管成像技术(MR venography，MRV)对静脉系疾病的诊断价值及临床意义。方法采用二维时间飞跃法MR血管造影(2D-TOF-MRA)、二维相位对比血管造影(2D-PCA)和三维对比增强MR血管造影(3D-CE-MRA)3种血管成像技术分别对20例健康志愿者和20例临床或MRI疑有静脉系疾病的患者行MRV成像，并采用最大强度投影(MIP)、多平面或曲面重建(MPR)及数字减影MRA(DSMRA)技术对图像进行后处理，观察脑静脉系在MRV中的显示情况及脑静脉系疾病在MRV中表现形式，制定脑静脉系成像的最佳方案。结果本组经3D-CE-MRA静脉系成像诊断为13例颅内静脉窦血栓形成(CVST)及7例颅内肿瘤累及静脉系的阳性显示率为100％，均经临床治疗复诊及手术证实。2D-PCA及2D-TOF-MRA对细小引流静脉显示欠佳，且2D-TOF-MRA对复杂区域内静脉血管亦显示欠佳。结论3D-CE-MRA结合2D-PCA及2D-TOF-MRA静脉成像技术形成全脑静脉系成像，为脑静脉系的最佳成像方案，对临床术前评估和指导治疗有极其重要的意义。     

3D time-of-flight MR angiography of the intracranial vessels: optimization of the technique with water excitation, parallel acquisition, eight-channel phased-array head coil and low-dose contrast administration

The aim of this study is three folds: to compare the eight-channel phased-array and standard circularly polarized (CP) head coils in visualiazation of the intracranial vessels, to compare the three-dimentional (3D) time-of-flight (TOF) MR angiography (MRA) techniques, and to define the effects of parallel imaging in 3D TOF MRA. Fifteen healthy volunteers underwent 3D TOF MRA of the intracranial vessels using eight-channel phased-array and CP standard head coils. The following MRA techniques were obtained on each volunteer: (1) conventional 3D TOF MRA with magnetization transfer; (2) 3D TOF MRA with water excitation for background suppression; and (3) low-dose (0.5 ml) gadolinium-enhanced 3D TOF MRA with water excitation. Results are demonstrating that water excitation is a valuable background suppression technique, especially when applied with an eight-channel phased-array head coil. For central and proximal portions of the intracranial arteries, unenhanced TOF MRA with water excitation was the best technique. Low-dose contrast enhanced TOF MRA using an eight-channel phased-array head coil is superior in the evaluation of distal branches over the standard CP head coil. Parallel imaging with an accelaration factor of two allows an important time gain without a significant decrease in vessel evaluation. Water excitation allows better background suppression, especially around the orbits and at the periphery, when compared to conventional acquisitions.     

Three-dimensional time-of-flight MR angiography in the evaluation of cerebral aneurysms

We review our preliminary experience with the use of three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography (MRA) in the assessment of intra- and extracranial aneurysms. Six patients were examined: Five had intracranial aneurysms and one had a cervical carotid pseudoaneurysm. A 3D rephased gradient recalled echo pulse sequence and maximum intensity projection (MIP) reconstruction algorithm were used. Magnetic resonance angiography, spin echo MR, and conventional angiography were retrospectively reviewed with specific regard to individual vessel visualization, aneurysm depiction, and presence of artifact related to acquisition techniques or MIP reconstruction. All aneurysms were detected on MRA, and anatomical correlation with conventional angiography was excellent. Significant problems included loss of visualization of small vessels, intraluminal signal loss in large vessels, subacute thrombus simulating flow on MIP reconstructions, and limited projections obtainable with MIP techniques. Adequate MRA assessment of aneurysms can be obtained using a combination of T1-weighted spin echo images and 3D TOF MRA. Review of all components of the MRA is required. MRA may be useful in screening asymptomatic patients for intracranial aneurysms as well as in the follow-up of patients treated with balloon occlusion.     

Magnetic resonance angiography of giant intracranial aneurysms

3D time-of-flight magnetic resonance angiography (3D TOF MRA) and 2D MRA with presaturation were evaluated in 18 patients with 21 giant intracranial aneurysms. 3D TOF MRA gave optimal images of proximal unruptured and nonthrombosed aneurysms. 2D MRA with presaturation was more informative in cases of distal, haemorrhagic or thrombosed aneurysms and in assessment of their components (thrombus, haemorrhage, patent residual lumen).     

Detection of intracranial aneurysms by three-dimensional time-of-flight magnetic resonance angiography

The purpose of this study was to investigate the reliability of magnetic resonance angiography (MRA) for detection of intracranial aneurysms. Ninety-six consecutive patients who underwent both MRA using the three-dimensional time-of-flight technique (3D TOF) with the rephase/dephase subtraction method and conventional angiography were reviewed. MRA showed 22 aneurysms in 19 patients, and conventional angiography 28 aneurysms in 23 patients. The sensitivity of MRA was thus 79% for aneurysms in 83% of patients. MRA showed no aneurysm in 67 of 73 patients without aneurysms; its specificity was therefore 92%. The 6 false positive interpretations were suspected internal carotid artery aneurysms.