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.     

Evaluation of prototype equipment for digital subtraction angiography in diagnosing intracranial lesions

Two prototype units for digital subtraction angiography have been developed by Japanese manufacturers. Their performance in demonstrating various intracranial lesions in 121 patients was evaluated. Comparison with conventional selective catheter angiography was possible in 77 patients. Digital subtraction angiography proved useful in preoperative evaluation of pituitary tumors when transsphenoidal surgery was being considered; demonstration of faint tumor stains which might be missed on conventional angiography; demonstration of larger aneurysms, arteriovenous malformations, and tumors as a screening technique; demonstration of abnormalities involving the dural sinuses; and follow-up of patients after surgery or embolization.     

MR angiography in children with cerebral neurovascular diseases: findings in 31 cases.

OBJECTIVE. We evaluated the suitability of MR angiography for routine use in children with suspected intracranial vascular disease. SUBJECTS AND METHODS. Thirty-one children, 6 months to 14 years old, with intracranial lesions or clinically suspected vascular malformations were studied prospectively with conventional MR imaging and time-of-flight MR angiography. In nine cases, MR angiographic findings were verified with digital subtraction angiography or conventional angiography. All MR studies were performed on a 1.5-T MR system using a circularly polarized head coil. RESULTS. Arterial MR angiography, performed in 24 cases, revealed congenital abnormalities of the arterial vessels in 20 cases. Vessel stenosis was observed in nine patients, and displacement of intracranial arteries due to tumors could be seen in 10 patients. Seven children had no abnormal findings. Venous MR angiography was performed in seven children, with depiction of sinus thrombosis in six cases. The comparative analysis of MR angiography and digital subtraction angiography showed equivalent results in nine patients; in one patient the degree of stenosis was overestimated with MR angiography. CONCLUSION. MR angiography, when combined with MR imaging, reveals information about soft-tissue and vascular structures in a single setting. At this point, MR angiography can replace invasive conventional angiography or digital subtraction angiography only in selected cases because of software and hardware limitations. Arterial or venous MR angiography can be helpful as an additional scan in MR examinations of children with suspected cerebral neurovascular diseases, and its noninvasive nature makes it well suited for routine use in children.     

First-line investigation of acute intracerebral hemorrhage using dynamic magnetic resonance angiography

Purpose: To report the initial experience of magnetic resonance (MR) digital subtraction angiography (MR-DSA) in the dynamic assessment of the cerebral circulation in acute non-traumatic intracerebral hemorrhage (ICH).

Material and Methods: Twelve patients with acute ICH were investigated within 6 days of the ictus using a dynamic contrast-enhanced 2-D MR angiogram that produces subtracted images with a temporal resolution of 1-2 frame/s. The MR-DSA examinations were assessed for evidence of an intracranial vascular abnormality and were compared with (i) the routine MR sequences, (ii) non-dynamic time-of-flight MR angiography, and (iii) catheter angiogram performed during the same admission.

Results: All 12 MR-DSA examinations were considered to be technically satisfactory. MR-DSA detected an intracranial vascular abnormality in 7 patients (3 arteriovenous malformations, 2 aneurysms, 1 dural arteriovenous fistula, and 1 venous thrombosis). All abnormalities were confirmed by catheter angiography with the exception of one patient with venous sinus thrombosis found on MR imaging that did not undergo catheter angiography. All four arteriovenous shunts were detected by MR-DSA by virtue of early venous filling.

Conclusion: MR-DSA can be performed satisfactorily in the setting of acute ICH and provides an alternative method to catheter angiography for identifying shunting vascular abnormalities such as arteriovenous malformations and fistulae, as well as large aneurysms and venous occlusions. MR-DSA is a contrast-medium-based technique that does not suffer from the T1 shortening effects of acute hemorrhage that can obscure abnormalities on conventional flow-based non-dynamic techniques.     

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。     

旋转数字减影脑血管造影每幅图像投照角度确定的临床研究

目的　探讨确定脑血管旋转DSA任意 1帧图像投照角度的可行性。方法　通过模型试验获得旋转血管造影数次旋转的有关数据 ,采用数据拟合方法得到描述X线机旋转规律近似的数学表达式。使用可编程手持器实现对 2 3例脑血管旋转DSA任意 1帧图像投照角度的实时计算。结果　所有 2 3例脑血管旋转DSA中 ,可编程手持计算器均可立即计算出每一个感兴趣图像的投照角度。其中颅内动脉瘤 14例 ,左前颅凹脑膜瘤 1例 ,颅内大脑动静脉畸形 8例。对比由计算器获得的图像与旋转DSA相对应的图像 ,两者在显示异常动脉的起源、形态、走行、分布以及病变的供血动脉和引流静脉等诸方面 ,具有较好的相似性。结论　实时确定脑血管旋转DSA任意图像的投照角度 ,对准确诊断与治疗颅内脑血管异常具有重要作用     

Rotational cerebral angiography: procedure and value

Rotational cerebral angiography provides continuously changing projections and correspondingly excellent visualization of aneurysms or other vascular malformations requiring special or oblique views. Rotation angiography as part of the routine angiography gives a three-dimensional impression with one injection and series of films. Although additional subtraction technique is not possible and the injection time has to be prolonged, the technique is nevertheless advantageous compared with magnification angiography and angiotomography in the preoperative evaluation of cerebral vascular malformations.     

Evaluation of the circle of Willis with three-dimensional CT angiography in patients with suspected intracranial aneurysms.

PURPOSETo determine the usefulness of CT angiography in the setting of suspected acute subarachnoid hemorrhage or intracranial aneurysm.METHODSWe prospectively studied 68 patients suspected of having subarachnoid hemorrhage or an intracranial aneurysm with noncontrast CT of the head followed immediately by contrast-enhanced helical CT of the circle of Willis with three-dimensional reconstruction. Twenty-seven patients with CT findings positive for subarachnoid hemorrhage or intracranial aneurysm were evaluated with digital subtraction angiography or MR angiography within 12 hours of CT angiography. Patients with negative CT/CT angiography findings were followed up with lumbar puncture.RESULTSCT angiography showed 23 of 24 aneurysms and 2 of 2 arteriovenous malformations (sensitivity, 96%; specificity, 100%). Aneurysm size ranged from 2 to 40 mm (mean, 7.9 mm). Interobserver variability was 10%. In the 23 cases of subarachnoid hemorrhage, cisternal blood did not limit the three-dimensional reconstruction. Two patients with aneurysms on CT angiography had normal noncontrast scans.CONCLUSIONSCT angiography of the circle of Willis is a useful technique for evaluation of suspected acute subarachnoid hemorrhage and intracranial aneurysm. It provides anatomic display of intracranial aneurysms, allowing for planning of conventional angiography and surgical approach. In selected cases, CT angiography may eliminate the need for preoperative conventional angiography.     

Preoperative embolization for meningeal tumors: evaluation of vascular supply with angio-CT

When evaluating vascular supply, a combined angiography and CT (angio-CT) system provides more accurate vascular anatomy than digital subtraction angiography. To the best of our knowledge, however, the application for intracranial tumors has not been described. We herein describe a technique of an angio-CT system for diagnosis of vascular anatomy of the feeding artery for preoperative embolization of meningeal tumors.     

旋转血管造影技术对颅内动脉瘤的诊断价值

目的探讨旋转血管造影技术对颅内动脉瘤的诊断价值。方法对21例蛛网膜下腔出血（subarachnoid hemorrhage，SAH）患者的脑血管造影检查资料进行回顾性分析，所有患者均行常规数字减影血管造影（digital subtraction angiography，DSA）及旋转DSA检查，比较DSA和旋转DSA对动脉瘤瘤体、瘤颈和载瘤血管的显示情况。结果④21例患者共发现动脉瘤23个，常规DSA仅清晰显示16个，旋转DSA清晰显示23个。②DSA清晰显示瘤颈4个，载瘤血管11个，旋转DSA清晰显示瘤颈17个，载瘤血管21个。经统计学处理，差异均具有显著性（P〈0．01）。结论旋转DSA比常规DSA更容易发现动脉瘤．能更清晰显示动脉瘤形态、位置以及与周围血管的关系，是常规DSA不可缺少的补充。     

Appearance and impact of post-operative intracranial clips and coils on whole-brain CT angiography and perfusion

Background

To evaluate the effect of vascular clips and endovascular coils placed for intracranial aneurysms and arteriovenous malformations on whole-brain computed tomography (CT) angiography and perfusion.

Methods

A 320-detector row dynamic volume CT system imaged 11 patients following surgical placement of vascular clips or endovascular coils. The extent of clip and coil subtraction by automated software was evaluated using CT digital subtraction angiography and CT perfusion. Impact on CT perfusion values by retained intracranial devices was compared to age- and gender-matched controls.

Results

Clip and coil subtraction on CT angiography was graded as good in 8 and moderate in 3 cases. A residual neck and additional aneurysm were noted in 1 of 11 patients. Post-procedural axial slice level CT perfusion values decreased in reliability with increasing proximity to the metallic devices secondary to beam hardening. However, the intracranial devices did not affect axial slice level CTP values of cerebral blood volume, cerebral blood flow and mean transit time outside of the level of the device. Time to peak values was globally decreased outside of the immediate vascular intervention region.

Conclusions

Advances in CT technology have provided clinically useful subtraction of intracranial clips and coils. While CT perfusion values were altered in device subtraction areas and within beam hardening artifact areas; they can provide valuable postoperative information on whole-brain hemodynamics. In selected cases, the combination of CT angiography and whole-brain CT perfusion can offer an alternative to conventional angiography that is a more invasive option.     

Rotational angiography assessment of cerebral aneurysms.

PURPOSETo compare rotational angiography with conventional digital subtraction angiography in the assessment of cerebral aneurysms.METHODSConventional digital subtraction angiography and rotational angiography were compared in 57 patients investigated for the preoperative diagnosis of subarachnoid hemorrhage and in 13 patients after surgery. Images were compared for location, visibility of the aneurysmal neck, vascular branch anatomy, projection, size, presence of spasm, and shape of the aneurysm.RESULTSRotational angiography was superior to the digital angiogram in assessing aneurysms and vascular anatomy in the following percentage of cases: 12% for location, 46% for the presence of a neck, 32% in the assessment of branch anatomy, 19% for projection, 12% for size, 3.5% for spasm, and 19% for shape. After surgery, rotational angiography more clearly demonstrated the presence or absence of a neck in 69% of the cases.CONCLUSIONSRotational angiography often allows better visualization of vascular anatomy and therefore improves the angiographic assessment of aneurysms when compared with conventional digital subtraction angiography, making it an excellent adjunct in the investigation of subarachnoid hemorrhage. The lack of subtraction artifacts from the surgical clips and multiple angles of view also allow better assessment of the presence or absence of a residual neck in postoperative cases.     

MSCT血管造影在颅内血管性疾病中的诊断价值

目的探讨16层螺旋CT血管造影(MSCTA)在颅内血管性疾病中的诊断价值。方法对339例患者行16排螺旋CT血管造影,同时采用容积重建(VR)、多平面重建(MPR)、最大密度投影(MIP)显示血管,其中45例动脉瘤、22例动静脉畸形、4例烟雾病和18例脑动脉狭窄随后进行了DSA检查或手术治疗。结果CTA诊断为动脉瘤的患者83例,动静脉畸形22例,静脉瘤2例,海绵状血管瘤3例,海绵窦动静脉瘘3例,单纯烟雾病3例,烟雾病合并动脉瘤1例,缺血性脑血管病22例,先天性变异等32例,正常病例186例,其中CTA诊断的45例动脉瘤、22例动静脉畸形、4例烟雾病和18例脑动脉狭窄与DSA检测结果及手术结果基本一致。结论MSCTA对头部血管性疾病的诊断,具有微创、快速、安全、准确性高的特点,可作为头部血管性疾病的首选影像学筛查。     

Occlusive vascular disease associated with cerebral arteriovenous malformations

Selective carotid angiography and computed tomography were used in a study of the association of occlusive vascular disease with cerebral arteriovenous malformations in 13 patients. The arterial occlusions ranged from focal stenosis in the major artery supplying the malformation to complete occlusion of the supraclinoid internal carotid artery with subsequent development of "moyamoya" collaterals. The majority of the arterial occlusions were proximal to the vascular malformation. Some, however, extended distal to the major branch supplying the arteriovenous malformation (AVM). Selective angiography with subtraction techniques defines the distinct angioarchitecture of these AVMs and the associated stenoses and collateral telangiectases.     

Intracranial intravenous digital subtraction angiography

Summary Intravenous digital subtraction angiography (iDSA) promises to significantly alter the use of conventional cerebral angiography in the workup of neurological patients. Understanding its diagnostic potential and its limitations are important in incorporating this new examination into the diagnostic thought process of neuroradiologic tests. Different image processing techniques such as integration of mask and contrast images promise to improve image quality for neuroradiologic application. At present, iDSA is suitable for the diagnosis and follow-up of vascular lesions (atherosclerosis, aneurysms, arteriovenous malformations, venous sinus occlusion), and tumor (meningioma). Although limited, the spatial resolution of iDSA studies is capable of demonstrating diffuse vascular disease such as arteritis and vasospasm after subarachnoid hemorrhage. In some patients in conjunction with the CT scan, iDSA may prove sufficient as the primary and only diagnostic angiographic test necessary, supplanting conventional angiography.Supported by NJH Contract 1 RO1HL 25905-O1A1     

Arterialization of cerebral veins on dynamic MDCT angiography: a possible sign of a dural arteriovenous fistula

OBJECTIVE: MDCT angiography allows fast imaging of the cerebral vessels, and its potential as a noninvasive technique to detect vascular abnormalities on the basis of morphologic changes is well established. We analyzed vascular enhancement patterns of cerebral venous structures on MDCT angiography, which enabled us to diagnose dural arteriovenous fistula. CONCLUSION: MDCT angiography performed during an early arterial phase showed asymmetrically higher contrast intensity in the transverse or sigmoid sinus, or both, in five patients. In all patients, digital subtraction angiography confirmed the presence of a dural arteriovenous fistula on the side on which the higher contrast intensity appeared. Radiologists should actively look for this sign in the imaging workup of patients presenting with nonspecific symptoms that might be related to a dural arteriovenous fistula.     

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     

Three-dimensional rotational spinal angiography in the evaluation and treatment of vascular malformations

BACKGROUND AND PURPOSE: Conventional spinal angiography, although useful in providing angioarchitectural details of spinal vascular disease, has limitations. The advent of 3D angiography has provided a better comprehension of angioarchitectural detail when evaluating the intracranial circulation. The purpose of this study was to evaluate the usefulness of 3D angiography in the diagnosis and treatment of vascular malformations of the spine. METHODS: This retrospective analysis included 17 3D spinal angiograms acquired in 14 consecutive patients examined at our institution for a spinal vascular lesion, which included nine spinal cord arteriovenous malformations (AVMs), one perimedullary arteriovenous fistula (AVF), three spinal dural AVFs, and one nerve root AVM. 3D angiography was obtained with apnea under general anesthesia by using a 14-second acquisition and 200 degrees rotation of the gantry during injection of 300 mg I/mL nonionic contrast material at a rate of 0.5-3.5 mL/s. Multiple reconstructed images were obtained with or without opacification of the surrounding structures. These images were then evaluated by the interventionalists at the time of the procedure and compared with findings obtained by conventional subtraction angiography. RESULTS: 3D angiography was useful in differentiating intramedullary lesions from perimedullary surface lesions; detecting arterial, nidal, or venous aneurysms; and evaluating the 3D structure of the lesion as well as the relationship between the malformation and its draining veins or surrounding bony structures. In specific situations, it obviated the need for contrast-enhanced conventional or 3D CT, as well as for lateral or oblique angiographic views, which are sometimes difficult to obtain with good quality. No 3D angiography-related complications were experienced. Some limitations in the definition of small vessel anatomy in the reconstructed images were noted. CONCLUSION: In this small series of patients, 3D angiography was safe and useful for evaluation of the 3D vascular anatomy of spinal vascular malformations.     

Two-dimensional thick-slice MR digital subtraction angiography for assessment of cerebrovascular occlusive diseases

Although spatial resolution of current MR angiography is excellent, temporal resolution has remained unsatisfactory. We evaluated clinical applicability of 2D thick-slice, contrast-enhanced subtraction MR angiography (2D-MR digital subtraction angiography) with sub-second temporal resolution in cerebrovascular occlusive diseases. Twenty-five patients with cerebrovascular occlusive diseases (8 moyamoya diseases, 10 proximal internal carotid occlusions, and 2 sinus thromboses ) were studied with a 1.5-T MR unit. The MR digital subtraction angiography (MRDSA) was performed per 0.97 s continuously just after a bolus injection of 15 ml of gadolinium chelates up to 40 s in sagittal (covering hemisphere) or coronal planes. Subtraction images were generated at a workstation. We evaluated imaging quality and hemodynamic information of MRDSA in comparison with those of routine MR imaging, non-contrast MR angiography, and X-ray intra-arterial DSA. Major cerebral arteries, all of the venous sinuses, and most tributaries were clearly visualized with 2D MRDSA. Also, pure arterial phases were obtained in all cases. The MRDSA technique demonstrated prolonged circulation in sinus thromboses, distal patent lumen of proximal occlusion, and some collateral circulation. Such hemodynamic information was comparable to that of intra-arterial DSA. Two-dimensional thick-slice MRDSA with high temporal resolution has a unique ability to demonstrate cerebral hemodynamics equivalent to that of intra-arterial DSA and may play an important role for evaluation of cerebrovascular occlusive diseases. Received: 16 November 1999; Revised: 27 June 2000; Accepted: 29 June 2000     

颅颈部血管多层螺旋减影CTA与DSA的比较研究

目的 评价减影CTA对检察颅颈部血管性病变的灵敏度和特异度及其临床应用价值.方法 对76例怀疑颅颈部血管疾病患者施行16层螺旋减影CTA检查,在保证增强前后所采集的数据参数一致的前提下用Neuro-DSA软件进行减影,其中30例与DSA作比较观察.减影CTA图像质量分为优良、一般、差;应用非参数统计检验、计算减影CTA显示病变的灵敏度和特异度.结果 以颈内动脉颅段、前后交通动脉、大脑前中后动脉近段、椎基动脉为观察对象,共观察血管段900段.减影CTA图像质量优良571段,为63.4%,一般有301段,为33.4%.但在显示颅颈部不同段血管的图像质量上有差异;减影CTA检出病变的灵敏度为84.4%,特异度为40%,检出动脉瘤的灵敏度和特异度均为100%.结论 16层螺旋减影CTA无创,快捷,简单易行,能提供较高分辨率的血管图像,可作为一种常规的方法应用于颅颈部血管疾病的筛查和诊断.