Magnetic resonance applications in atherosclerotic vascular disease

Magnetic resonance imaging of the cardiovascular system offers great promise in the detection and characterization of the anatomic, physiologic, and biochemical consequences of atherosclerosis. This review will focus on the potential applications of MRI for evaluating atherosclerosis of the abdominal aorta and iliofemoral vessels.     

脑性瘫痪的MRI特征

目的:探讨脑性瘫痪(脑瘫)患儿的头颅MRI表现及其与脑瘫类型的关系。方法:回顾性分析81例脑瘫患儿的临床资料与MRI表现。结果:81例脑瘫患儿MRI异常率为85.2%,痉挛型双瘫、四肢瘫、偏瘫、不随意运动型脑瘫、共济失调型脑瘫、肌张力低下型脑瘫和混合型脑瘫MRI异常率分别为92.9%、100%、100%、60%、87.5%、50%和81.8%。各类型脑瘫的MRI异常表现不同,痉挛型双瘫以脑室周围白质软化(PRL)为主,偏瘫型突出表现为单侧脑损伤,四肢瘫表现为广泛、弥漫、双侧脑损伤,不随意运动型表现为基底节病变或PVL,共济失调型绝大部分存在先天性小脑发育不全。结论:MRI有助于评价各型脑瘫的病理特点,对脑瘫病因的推测有帮助。     

Magnetic resonance angiography in suspected cerebral vasculitis

The purpose of this study was to determine the technical capacity and diagnostic accuracy of 3D time-of-flight magnetic resonance angiography (MRA) in suspected cerebral vasculitis in a retrospective analysis of MRA and digital subtraction angiography (DSA) in 14 young patients with clinical and/or radiological suspicion of cerebral vasculitis. A total of nine arteries were evaluated in each patient. Consensus review of DSA by three observers was the reference standard. The sensitivity for detecting a stenosis varied from 62 to 79% for MRA and from 76 to 94% for DSA, depending on the observer. The specificity for detecting a stenosis varied from 83 to 87% for MRA and from 83 to 97% for DSA. Using the criterion more than two stenoses in at least two separate vascular distributions to consider the examination as being true positive, the false-positive rates for MRA and DSA were comparable. MRA plays a role as the first angiographical examination in the diagnostic work-up of suspected cerebral vasculitis. When more than two stenoses in at least two separate vascular distributions are depicted on MRA, DSA is not expected to add a significant diagnostic contribution in a patient with suspected cerebral vasculitis. DSA remains necessary when MRA is normal or when less than three stenoses are seen.     

Magnetic resonance imaging in acute head injury

Using cardiorespiratory monitoring and support equipment compatible with a low field (0.15 T) system, magnetic resonance imaging (MRI) of patients suffering acute head injuries proved to be both feasible and safe. An abnormality was demonstrated by magnetic resonance imaging in 46 of 50 patients examined within 7 days of head injury using T2 weighted (SE2200/80) and T1 weighted (IR2000/600/40) multislice sequences. IN contrast, computed tomography (CT) demonstrated abnormalities in only 31 of the 50 patients. Intracranial extracerebral space-occupying collections of blood were well shown by magnetic resonance imaging which provided especially clear definition in the posterior fossa, subtemporal and subfrontal regions. Magnetic resonance imaging was more sensitive to cerebral abnormalities associated with traumatic unconsciousness and detected parenchymal lesions both in patients in coma and in those who had lost consciousness for only a few minutes. Lesions seen with MRI but not with CT included non-haemorrhagic contusions and abnormalities thought to reflect shearing injuries of white matter and intracerebral vessels. Magnetic resonance imaging is an effective alternative to CT; the additional information it can provide should be valuable in increasing the understanding of the early effects and late consequences of a head injury.     

Magnetic resonance imaging of muscle injury

To further evaluate the role of magnetic resonance (MR) imaging in diagnosing and managing muscle injuries, eight patients with muscle pain or palpable masses were imaged. MR findings were correlated with clinical follow-up data. Increased signal was noted on T2-weighted images in torn and overused muscles. One extensively scarred muscle required surgical biopsy to exclude a fibrous tumor. Three partial muscle tears were treated conservatively. One complete musculotendinous junction tear required tendon transfer. MR studies noninvasively identified and staged various muscle injuries, thereby influencing management.     

Magnetic resonance perfusion imaging in proliferative cerebral angiopathy

Cerebral proliferative angiopathy (CPA) is an unusual type of vascular malformation with unique clinical and imaging characteristics that distinguish it from the classic arteriovenous malformations. The features of CPA include absence of dominant arterial feeders or flow-related aneurysms, capillary angioectasia without large draining veins, and presence of intermingled normal brain parenchyma that is hypoperfused. We describe the magnetic resonance imaging findings including perfusion in 3 patients with CPA.     

Magnetic resonance in the study of cerebral gliomas

Forty surgically proved gliomas have been studied by MR: 21 were low-grade gliomas and 19 were anaplastic astrocytomas and glioblastomas. The examination involved the use of T1-weighted (IR and/or SE, TR 500 ms, TE 50 ms) and T2-weighted scans (SE, TR 1000 ms, TE 50 with multiple echos). All patients underwent CT and surgical removal or stereotactic biopsy whose findings were retrospectively compared with those of MR. MR findings were similar in low-grade and anaplastic astrocytomas, but quite different from imaging of glioblastomas. Tumoral cyst and areas of necrosis were recognized on MR studies and confirmed by surgical findings. Differentiation between tumor and oedema was difficult. The MR images did not allow a more specific diagnosis of nature or of malignancy than available with CT up to now, but offer major advantages, such as a superior depiction of tumor extent and anatomic relationships.     

Magnetic resonance imaging of cerebral fat embolism

Summary The cerebral fat embolism is a potentially serious complication of fractures but clinical cases often go undiagnosed. Two cases of clinically diagnosed cerebral fat embolism are reported, and MR images of these patients are described. While brain CT revealed no abnormality, MR imaging showed relative low-intensity areas on T1-weighted images and high-intensity areas on T2-weighted images. In one patient follow-up MR showed nearly complete resolution of the abnormal signal. MR imaging appears to be valuable for detecting the lesions in these patients.     

Magnetic resonance imaging of the cerebral aqueduct

Summary 1.5 Tesla MRI examinations were evaluated for aqueductal configuration, hydrocephalus and flow-related signal void in 70 patients with juxtaaqueductal pathology and in 20 normal controls. In the 70 cases with pathology, the aqueduct was obliterated or distorted in 34, dilated in 3, normal in 29 and not evaluable in 4. A definite flow-related signal void indicated CSF movement within the aqueduct in all normal examinations. Flow-related signal void was absent in some, but not all, patients with aqueductal obliteration and distortion. CSF turbulence can create an intra-aqueductal signal void in the dilated proximal aqueduct, despite more distal obstruction. Thus hydrocephalus related to aqueductal obstruction is frequently, but not always, associated with absence of signal void.     

颅脑爆震伤后兔脑内代谢变化的磁共振波谱研究

目的 利用磁共振波谱技术探讨颅脑爆震伤后不同时间段脑局部代谢变化.方法 新西兰大白兔45只采用随机数字表法分为对照组(10只)和创伤组(35只),采用600 mgTNT当量纸雷管在创伤组兔脑上方约6.5 cm垂直距离爆炸,于伤后1,6,12,24 h、3,7,14 d用磁共振波谱技术观测动物存活情况,并检测脑损伤区病理及磁共振波谱表现,观察乙酰天门冬氨酸(N-acetylaspartate,NAA)/肌酸(creatine,Cr)、胆碱(choline,Cho)/Cr在爆震伤后随时间发展的演变过程.结果 创伤组兔存活时间在7 d以上,病理及常规MRI示脑挫伤病灶;NAA/Cr均值在损伤后1 h明显下降,持续至伤后24 h,24 h后义上升,7 d后再次下降.Cho/Cr均值在损伤1 h后即明显升高,12 h后下降,3 d后义逐渐升高.结论 磁共振波谱技术可反映兔颅脑爆炸伤不同时间段局部组织的代谢变化,为了解爆雀伤后局部组织变化情况及判断组织损伤类型提供理论依据.

Abstract：

Objective To evaluate the regional cerebral metabolic changes in different episodes by magnetic resonance spectroscopy (MRS) after explosive brain injury in rabbits. Methods Fortyfive New Zealand white rabbits were randomly divided into eight groups, ie, normal control group( 10 rabbits) and trauma group (35 rabbits). The explosive injury in trauma group was induced by explosion of 600 mg TNT equivalent of paper detonators at 6.5 cm above the rabbit brain. The rabbits in trauma group was divided into 1,6, 12, 24 hours, 3, 7, 14 days subgroups (6 rabbits per group). The survival rate was observed at different time points after explosive injury. The MRS was used to detect the regional cerebral metabolic changes including N-acetylaspartate (NAA)/creatine (Cr) ratio and choline(Cho)/Cr ratio as well as evolution of blast injuries over time. Results The rabbits survived for overseven days in the trauma groups, with typical brain contusion manifested by pathological and conventional MRI. Compared with the normal control group, the NAA/Cr ratio was markedly decreased at one hour after injury, slightly rose again at 24 hours and fell again after seven days. The Cho/Cr ratio was markedly increased at one hour after injury, slightly fell again at 12 hours and rose again at three days after injury.Conclusions MRS can manifest the regional cerebral metabolic changes of rabbits with explosive injury at different time points and hence provide a theoretical basis for understanding the local tissue changes and determining the type of tissue damage after blast injury.     

Magnetic resonance imaging of cerebral venous sinus thrombosis

Cerebral venous sinus thrombosis (CVST) represents a diagnostic challenge due to the diversity of clinical presentation. The radiologist should be aware of the common neurological features. Unenhanced CT may show the first indications of venous sinus occlusion. Confirmatory diagnostic imaging should be performed with magnetic resonance imaging (MRI) and magnetic resonance venography (MRV) or computed tomography (CT) venography. We illustrate the MRI and MRV features of the thrombosed venous sinus and venous oedema or infarction and discuss the diagnostic limitations of these techniques.     

Magnetic resonance imaging and histopathology of cerebral gliomas

Summary The correlation of magnetic resonance imaging (MRI) with histopathological findings was analysed in 26 patients with untreated cerebral gliomas. In low-grade gliomas, T2-weighted images demonstrated relatively homogeneous high-intensity lesions involving both the grey and the white matter. In high-grade gliomas, especially grade IV, T2-weighted images demonstrated prominent heterogeneity in signal intensity, which consisted of a hyperintense core, less hyperintense or normal intensity rim and surrounding finger-like areas of high intensity. Marked and irregular contrast enhancement was evident in all but one case of these high-grade gliomas in which gadolinium-DTPA was used. Histological examination revealed tumour cells extending as far as the borders of the high-intensity areas shown on T2-weighted images in both high-and low-grade gliomas, but in 5 of 8 low-grade and 4 of 18 high-grade gliomas, isolated tumour cells extended beyond the hyperintense areas shown on T2-weighted images.     

高原脑水肿的MRI诊断

目的:分析高原脑水肿(high altitude cerebra edema,HACE)的MRI表现,以提高对本病诊断的准确性。方法:对13例高原脑水肿患者行头颅MRI横断位SE序列(T1WI、T2WI)、水抑制(FLAIR)及矢状位SE序列(T1WI)扫描,对其MRI表现进行回顾性分析。结果:高原脑水肿MRI表现:T1WI为低信号,T2WI为高信号,信号较均匀,边缘不清,FLAIR为较均匀高信号。13例双侧大脑半球白质对称性水肿,5例大脑灰质水肿,12例胼胝体水肿,3例丘脑水肿,3例脑干水肿,9例小脑水肿,11例侧脑室变窄,12例脑沟变窄,5例脑裂变窄。结论:高原脑水肿于MRI呈弥漫性改变,大脑、胼胝体、丘脑、脑干、小脑均可受累,以胼胝体为中心,为多种类型并存的脑水肿,有一定的特征性。MRI能正确诊断高原脑水肿提供依据。     

Magnetic resonance imaging of acute spinal cord injury

Summary Magnetic resonance imaging of acute spinal cord injury is described. The traumatized cord segment was clearly shown as a hyperintensity in a T2-weighted image whereas it appeared as an isointensity in a moderately T1-weighted image. This different sensitivity may result from parenchymal hemorrhagic tissue and edematous changes due to direct trauma. Hyperintense tissue was also seen in the retro-pharyngeal and-tracheal spaces.     

儿童脑多形性黄色星形细胞瘤的MRI分析

目的 :分析儿童期脑多形性黄色星形细胞瘤 (PXA)的MRI表现。方法 :对经手术病理证实的 7例儿童期脑PXA的MRI资料进行回顾性分析 ,研究肿瘤的部位、形态和信号特征。结果 :7例肿瘤均呈囊实性 ,位于脑表浅部位 ,3例边界清楚 ,4例边界欠清楚。肿瘤实质与脑灰质比较在T1WI呈低信号 ,在T2 WI呈混合性高信号 ,增强后肿瘤实性部分和壁结节明显强化 ,3例囊性伴壁结节的肿瘤中 2例囊壁有强化 ,1例无强化。结论 :儿童期脑PXA多起源于脑表浅部位 ,颞叶为最常见部位 ,肿瘤常呈囊实性 ,增强后肿瘤实性部分和壁结节明显强化。