Invited. MRI and MR angiography in moyamoya disease

The role of radiological imaging in moyamoya disease includes screening of the disease based on clinical findings, evaluation of the changes in vasculature and brain parenchyma, and clinical follow-up. The imaging findings in moyamoya disease are classified as primary and secondary. The primary findings essentially consist of occlusion of the circle of Willis and collateral formation, including moyamoya vessel formation. The secondary findings include cerebral infarction, white matter lesions, atrophy, and hemorrhage. For the visualization of the primary and secondary findings as well as postoperative results, MRI and MR angiography are the most reliable methods and play important roles because of their excellent diagnostic yield and noninvasiveness.     

Intravenous angiography in brain death: report of 140 patients

We present our experience and discuss the value of cerebral intravenous digital subtraction angiography (IV DSA) in the diagnosis of brain death. A total of 140 patients presenting with clinical signs of brain death were studied by IV DSA. According to the angiographic appearance of the vertebrobasilar system, the patients were divided into four groups. Cessation of blood flow within the internal carotid arteries and their branches was consistently found. Attention is focused on 9 patients with persistent blood flow within the posterior fossa. In sedated patients in whom EEG and evoked brain-stem responses are non-diagnostic, or in order to shorten the observation time, transcranial Doppler should be performed to determine the appropriate moment for IV DSA, which is a reliable method of confirming brain death. Received: 14 February 1996 Accepted: 15 July 1996     

儿童大脑神经母细胞瘤MRI诊断分析

目的探讨儿童大脑神经母细胞瘤MRI的影像特点。方法对经手术及病理证实的3例儿童幕上大脑神经母细胞瘤患者的MRI资料进行回顾性分析。本组3例患儿均行颅脑MRI常规平扫加增强扫描。结果 3例患儿肿瘤均位于幕上,包括额叶1例,顶叶2例。病灶呈类圆形或分叶状,边界清楚。T1WI呈不均匀稍低或低信号,T2WI呈稍高或高信号。2例见大囊变合并出血,瘤周见轻度水肿。增强扫描3例均见明显强化。结论儿童大脑神经母细胞瘤MRI表现具有一定的特点,根据肿瘤部位、边界、信号、水肿、增强特点有助于该病的诊断和鉴别诊断。     

磁共振冠状动脉成像新技术及其临床应用

磁共振冠状动脉成像作为一项无创性检查冠状动脉的影像手段，近十年来，成像序列及方法不断突破和创新，正由研究阶段逐步进入临床应用。目前全球多中心研究的重点是如何消除心脏及呼吸运动伪影，增加信噪比和空间分辨力以及快速成像、缩短检查时间等，力求更精确显示冠状动脉及其狭窄以满足临床需要。     

Digital subtraction angiography (DSA) in the evaluation of brain death

Summary Demonstration that intracranial circulation has ceased is the ultimate proof of brain death. This study was performed to evaluate digital subtraction angiography (DSA) compared with conventional cerebral angiography in the diagnosis of brain death. Intravenous as well as intraarterial DSA was found suitable in the diagnosis of arrested intracranial circulation.     

Pancreatic adenocarcinoma: combination of MR imaging, MR angiography and MR cholangiopancreatography for the diagnosis and assessment of resectability

The purpose of this study was to determine the possibility of integrating MR cholangiopancreatography (MRCP) and MR angiography (MRA) to conventional MR images in the diagnosis and assessment of resectability of pancreatic adenocarcinoma. Twenty-three patients with pancreatic adenocarcinoma were prospectively examined with MR. Conventional MR images were acquired in all patients. Three-dimensional MRCP and MRA images were acquired in all patients with suspected biliary and vascular involvement. Acquisition time was less than 45 min in all cases. Images were independently evaluated by two radiologists, with final reading decided by consensus among readers. Diagnosis was confirmed with surgery in 16 patients and with percutaneous biopsy in 7. Concordance among readers was high with a kappa value of 0.83. Pancreatic adenocarcinoma was observed in all patients. Correct assessment of unresectability due to vascular involvement was found in 22 of 23 patients. Biliary obstruction was evident in 13 patients, involving the biliary and pancreatic ducts in 9 and the biliary ducts only in 4. Technical advances permit extensive use of MRI in the evaluation of abdominal pathologies. The combination of MR imaging, MRCP, and MRA can provide sufficient information for the diagnosis and assessment of resectability of pancreatic adenocarcinoma, which otherwise would require three different exams. Received 22 August 1996; Revision received 3 June 1997; Accepted 19 August 1997     

Striatocapsular infarction: MRI and MR angiography

We present a case of left striatocapsular infarction manifest clinically as a transient right hemiparesis. MRI showed a left striatocapsular infarct. Striatocapsular infarction, unlike lacunar infarction, is often associated with occlusive disease of the carotid artery. In order to screen the carotid vessels, cervical MR angiography (MRA) was performed during the same examination, demonstrating a left internal carotid artery occlusion, confirmed by contrast arteriography. MRA, a noninvasive modality, can be a useful adjunct to MRI, when diagnostic information concerning the cervical carotid artery is needed.     

Coarctation of the aorta: comparison of aortic dimensions between conventional MR imaging, 3D MR angiography,and conventional angiography

Magnetic resonance angiography is increasingly used as a non-invasive method in the evaluation of coarctation of the aorta. The aim of this study was to compare aortic dimensions calculated by MR angiography and those obtained by more conventional MR sequences and conventional angiography. Twenty-six consecutive patients with coarctation underwent three-dimensional MR angiography. Two independent observers retrospectively evaluated three aortic segments, site of coarctation, presence of aneurysm and existence of collateral circulation. Three aortic segments were also compared with those obtained on classical MR sequences and conventional angiography. The MR angiography was successfully performed in all showing 1 aneurysm and collateral circulation in 8 patients. Almost perfect intraobserver ( r(2)>0.91) and excellent interobserver ( r(2)>0.80) reliabilities were obtained for each aortic segment no matter which MR sequence was employed. Similarly, mainly excellent ( r(2)>0.80) concordance analysis was observed between MR angiography measurements and those calculated by either spin-echo/gradient-echo sequences or conventional angiography. This study demonstrates that MR angiography is a fast, accurate and reproducible method in the evaluation of coarctation of the aorta. It provides excellent anatomic information and reliably detects collateral vessels. Magnetic resonance angiography could probably replace the conventional angiography and will provide an additional diagnostic value in combination with turbo spin-echo sequence.     

Preoperative evaluation of gallbladder carcinoma: efficacy of combined use of MR imaging,MR cholangiography,and contrast-enhanced dual-phase three-dimensional MR angiography

PURPOSE: To determine the efficacy of the combined use of magnetic resonance (MR) imaging, MR cholangiography (MRC), and MR angiography (MRA) in the preoperative evaluation of gallbladder carcinoma. MATERIALS AND METHODS: During a 20-month period, 41 patients with proven gallbladder carcinomas were referred for MR examination, including MR imaging, MRC, and gadolinium-enhanced dual-phase MRA to determine the operability of their gallbladder carcinoma. Eighteen patients who underwent surgery within six days of the MR examination were included in this study. All MR images were analyzed in order to assess bile duct invasion, vascular invasion, hepatic invasion or metastasis, lymph node metastasis, and invasion into adjacent organs. RESULTS: Surgical and histopathologic findings revealed hepatic invasion in nine patients, bile duct invasion in nine, vascular invasion in three, and lymph node metastasis in 10. The sensitivity and specificity of MR examination were, respectively, 100% and 89% for bile duct invasion, 100% and 87% for vascular invasion, 67% and 89% for hepatic invasion, and 56% and 89% for lymph node metastasis. CONCLUSION: The "all-in-one" MR protocol, including MR imaging, MRC, and MRA, can be an effective diagnostic method in the preoperative work-up for gallbladder carcinoma.     

MR imaging and MR angiography in popliteal artery entrapment syndrome

Popliteal artery entrapment (PAE) syndrome is an uncommon congenital anomaly seen in young adults causing ischemic symptoms in the lower extremities. It is the result of various types of anomalous relationships between the popliteal artery and the neighboring muscular structures. The purpose of this study was to define the role of MR imaging combined with MR angiography in the diagnosis of PAE cases. Four cases with segmental occlusion and medial displacement of popliteal artery in digital subtraction angiography (DSA) examinations were diagnosed as PAE syndrome by MR imaging and MR angiography. The DSA and MRA images are compared. All of the cases showed various degrees of abnormal intercondylar insertion of the medial head of the gastrocnemius muscle. The MR images showed detailed anatomy of the region revealing the cause of the arterial entrapment. Subclassification of the cases were done and fat tissue filling the normal localization of the muscle was evaluated. The DSA and MRA images demonstrated the length and localization of the occluded segment and collateral vascular developments equally. It is concluded that angiographic evaluation alone in PAE syndrome might result in overlooking the underlying cause of the arterial occlusion, which in turn leads to unsuccessful therapy procedures such as balloon angioplasty. Magnetic resonance imaging combined with MR angiography demonstrates both the vascular anatomy and the variations in the muscular structures in the popliteal fossa successfully, and this combination seems to be the most effective way of evaluating young adults with ischemic symptoms suggesting PAE syndrome. Received 7 April 1997; Revision received 15 July 1997; Accepted 13 November 1997     

Contrast-enhanced MR 3D angiography in the assessment of brain AVMs

BACKGROUND AND PURPOSE: Digital subtraction angiography (DSA) is the current reference standard for the diagnosis, assessment, and management of brain arteriovenous malformations (AVMs). The purpose of this study was to compare the diagnostic utility of three-dimensional (3D) time-of-flight (TOF) magnetic resonance angiography (MRA) and contrast-enhanced 3D MRA in patients with intracranial arteriovenous malformations (AVMs) in different sizes and locations. The AVM diagnosis was proved via DSA and almost half of the patients had also hematoma. MATERIALS AND METHODS: Two radiologists, experienced on neurovascular imaging and independent from each other, retrospectively reviewed two MRA techniques and DSA with regard to the assessment of feeding arteries, AVM nidus, and venous drainage patterns on 20 patients with 23 examinations by scoring system. Disagreements were resolved by consensus. RESULTS: An excellent agreement between contrast-enhanced MRA and DSA was found in order to assess the numbers of arterial feeders and draining veins (Spearman r=0.913, P<0.001). The average scores in contrast-enhanced MRA for feeders, nidi, and drainers were respectively 2.26, 2.69, and 2.48, while in TOF-MRA they are 1.96, 1.35, and 0.89, respectively. CONCLUSION: Compared to TOF-MRA, 3D contrast-enhanced MRA is useful for visualization by subtraction technique of malformation components presented by hematoma or by haem product. On the other hand, for the cases presented by slow or complex flow that is especially in around or nidi or around the venous portion is also advantageous because of the independence from flow-related enhancement. Therapeutic effects were clearly demonstrated in three follow-up patients. A major limitation of this technique is the low spatial resolution. Since there is such a limitation, arterial feeder of a case with micro-AVM is not detected by contrast-enhanced MRA and nidus for the same case was observed retrospectively. In this respect, we believe that 3D contrast-enhanced MRA is a less invasive and inexpensive angiographic tool, but not a safe substitute for DSA. Yet, it can be a beneficial supplement to DSA in patients with cerebral AVMs at both initial diagnosis and at follow-up processes after therapy.     

3D MR angiography of intratumoral vasculature using a novel macromolecular MR contrast agent.

Noninvasive methods to visualize blood flow in the intratumoral vasculature have not previously been studied. In the present study, the use of a novel intravascular MR contrast agent with a generation-6 polyamidoamine dendrimer core (G6-(1B4M-Gd)192; MW: 175kD) was investigated, and the vasculature in experimental tumors was visualized using 3D MR angiography (MRA). Xenografted tumors in nude mice of two different histologies-KT005 (human osteogenic sarcoma) and LS180 (human colon carcinoma)-were used to obtain 3D MRA using G6-(1B4M-Gd)192 and Gd-DTPA. The contrast MR sectional images were correlated with the corresponding histological sections. The intratumoral vasculature in the KT005 tumor was clearly visualized by 3D MRA, which became more evident with the growth of the tumor xenograft. In contrast, the intratumoral vasculature in the LS180 tumor was sparser and much less developed than that in KT005 tumors. Blood vessels with a diameter as small as 100 microm based on histology were visualized using 0.033 mmol Gd/kg of G6-(1B4M-Gd)192. In conclusion, intratumoral vasculature with a 100-microm diameter was visualized better using 3D MRA with G6-(1B4M-Gd)192 than with Gd-DTPA.     

Confirmation of brain death in the emergency department

When a patient is brought to the emergency department with profound coma, absent brain stem reflexes, and apnea, the possibility of brain death should be considered. If this condition is irreversible, the patient meets the clinical criteria and may be declared dead. Prompt confirmation is important: valuable resources can be redirected to living patients, the decedent’s family can be given ministry, and transplantation of donor organs to needy patients can be facilitated. Although brain death is a clinical diagnosis, confirmation by additional testing is often required by local practice standards or local law. This article discusses the role of the radiologist in this situation and the examinations used for this purpose.     

三维增强MR血管成像诊断脑动静脉畸形的价值

目的 评价三维增强MR血管成像（3DCEMRA）及相关MRI对脑动静脉畸形（AVM）的诊断价值。方法 22例脑AVM患者行头颅MRI及3DCEMRA检查，17例同时行DSA检查。3DCEMRA原始图像减影后至工作站用实时三维容积显示技术进行三维重组。结果 22例中19例MRI显示脑AVM特征性流空血管影，3DCEMRA显示明确异常血管团、供血动脉及引流静脉。病灶均位于幕上，单叶13例，跨叶3例，大脑深部3例；单支供血动脉9例，联合供血10例；引流静脉人上矢状窦6例，至大脑深部8例，向脑表面及脑深部均有引流5例。14例3DCEMRA与DSA比较，DSA显示供血动脉37支，引流静脉25支。3DCEMRA结合MRI对异常血管团的定位及立体显示优于DSA，但在一些细节显示上不如DSA；3DCEMRA对供血动脉的显示率为78．4％（29／37），对引流静脉的显示率为84．0％（21／25）。另外，3例DSA发现〈1cm的微小异常血管，但3DCEMRA未见，MRI仅表现为脑内出血灶。结论 3DCEMRA结合MRI对脑AVM能无创性准确定位、定性，并可显示其结构组成，可作为临床高度怀疑脑AVM患者的首选影像检查方法。但在显示某些细节及〈1cm的微小AVM方面仍需DSA检查。     

脑肿瘤磁共振血管成像的初步研究

目的：应用ＴＯＦ法ＭＲＡ显示脑肿瘤的肿瘤血管、供血动脉、引流静脉和脑血管移位与侵犯等，以探讨ＭＲＡ无创性评价脑肿瘤的价值。材料与方法：对４３例脑肿瘤患者进行了ＴＯＦ法ＭＲＡ（ｎ＝４３）与脑血管造影（ｎ＝１５）和／或手术结果（ｍ＝４１）对比评价。采用１．０Ｔ超导ＭＲ系统，二维或三维ＦＩＳＰ扫描，用或不用预饱和技术和Ｇｄ－ＤＴＰＡ，ＭＩＰ重建获取ＭＲＡ图像。结果：ＭＲＡ准确了７６．２％的肿瘤富血管度，     

CE-MRA与BI-RADS分类在乳腺癌诊断中的应用

目的:评价联合使用乳腺血管数目及BI-RADS分类提高乳腺癌诊断特异度的价值。方法:对52例乳腺病变患者进行磁共振动态增强扫描。乳腺血管在增强磁共振血管造影像计数,计数评价从0～3级(按血管丰富程度)。所有病例按照MRI BI-RADS分类,分为Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ类。结果:52例患者中,24(42.2%)例为恶性病变,28(57.8%)例为良性病变。良恶性病变乳腺血管数有明显差别(P=0.000<0.05)。采用0～1级诊断为良性病灶,2～3级诊断为恶性病灶,诊断的特异度为78.6%,灵敏度为83.3%。按照BI-RADS分类诊断为:特异度71.4%灵敏度:87.5%。BI-RADS分类与血管数目结合后特异度为85.7%灵敏度:83.3%。结论:乳腺良恶性病变血管数目在磁共振血管造影上有明显的差异,结合MRI BI-RADS分类可以提高MRI诊断乳腺癌的特异度。     

MR angiography of run-off vessels

Magnetic resonance angiography has taken a huge step forward since the introduction of contrast-enhanced MR angiography using gadolinium chelates. The more conventional MR angiographic techniques, such as time-of-flight and phase-contrast MR angiography, have been ousted by contrast-enhanced MR angiography in most vascular areas. However, in imaging the lower extremities, the major obstacle is the length of the vascular tree. In order to cover the entire peripheral vasculature, at least two to three fields of view are required. Using contrast-enhanced MR angiography, the best results are obtained if the vessels of interest are imaged during passage of a bolus of contrast material. Vessel-to-background contrast in subsequent acquisitions using subsequent injections of contrast material is hampered by recirculation and leakage of previously injected gadolinium, enhancing both the venous system and surrounding tissue. To overcome this problem several research groups have come up with various solutions. The three main strategies employed can be classified as either bolus catch, bolus chase, or bolus track techniques. The purpose of this article is to explain working mechanisms of the three bolus imaging strategies for imaging both inflow and outflow vessels of the lower extremities, to show their advantages and disadvantages, and to review results described in the literature in imaging patients using these techniques.     

Comparison of phase-difference and complex-difference processing in phase-contrast MR angiography.

The two main phase-contrast reconstruction methods are phase difference and complex difference. The signal-to-noise ratio properties and relative advantages of the two techniques are discussed. It is argued that each processing method has applications in which it is superior, and guidelines are provided to determine those applications. It is demonstrated theoretically and experimentally that only the complex-difference method is well suited for processing phase-contrast slabs with use of a projection dephaser gradient.     

MR imaging and angiography in tuberculous meningitis

MRI was performed on 26 patients with tuberculous meningitis, with particular reference to document the cranial nerve abnormalitics. MR angiography (MRA) was performed in 20 of the patients. Meningeal enhancement in the basal cisterns or over the convexity of brain was seen in all patients; two show ependymal enhancement. Tuberculomas, single (3), multiple (12) or miliary (2) were detected in 17 patients. Of the 9 patients with cranial nerve palsies, 7 showed contrast enhancement with or without thickening of the involved nerve. Abnormality signal intensity of the involved nerve was seen on proton density and T₂-weighted images in one of these patients. MRA revealed focal arterial narrowing in 10 patients, the vessels commonly affected being the terminal segment of the internal carotid artery and the proximal segments of the middle and anterior cerebral arteries. One patient also had a small aneurysm of the proximal middle cerebral artery. Infarcts, haemorrhagic (8) or bland (6), were detected in 14 patients; most were the basal ganglia and internal capsules, large middle or anterior cerebral arterial territory infarcts being seen in only two cases.