Magnetic resonance of the brain: the optimal screening technique

Magnetic resonance (MR) images and computed tomograms of 25 patients with head trauma were compared. MR proved to be superior in many ways for demonstrating extracerebral as well as intracerebral traumatic lesions. Isodense subdural hematomas, which present a diagnostic dilemma on CT images were clearly seen on MR, regardless of their varying CT densities. In a case of epidural hematoma, the dura mater was shown directly as nearly devoid of signal on MR. Direct coronal images provided excellent visualization of extracerebral collections along the peritentorial space and subtemporal area. In a patient with intracerebral hematoma, CT failed to demonstrate residual parenchymal changes in a 3-month follow-up study, but MR clearly depicted the abnormalities. The superiority of MR over CT was also well illustrated in a patient with post-traumatic osteomyelitis of the calvarium.     

CNS complications of AIDS: CT and MR findings

AIDS is now a common disease, seen daily in large metropolitan medical centers. Neuroimaging techniques such as CT and MR are critical to the detection and diagnosis of CNS complications. Intracerebral infections are common. These infections frequently are caused by opportunistic organisms; less commonly, they are bacterial infections. The cranial imaging features on CT and MR are not pathognomonic, but their distribution or appearance (e.g., asymmetric target lesions of toxoplasmosis) may have predictive value in a known AIDS patient. The superior contrast resolution of MR makes it a more sensitive cross-sectional imaging tool for evaluating intracerebral abnormalities associated with a variety of infectious processes. Differential diagnoses still include metastatic disease, lymphoma, and infarcts. When MR is used as the initial cross-sectional imaging study, contrast-enhanced CT may still be necessary to further characterize a lesion. Currently, more experience exists with CT for follow-up of the AIDS patient with CNS manifestations. MR, particularly with gadolinium-DTPA as a contrast medium, will probably become the imaging method of choice.     

脑内型表皮样囊肿的CT和MRI诊断

目的探讨脑内型表皮样囊肿的CT和MRI影像表现特点,提高对脑内型表皮样囊肿影像诊断的准确性。资料与方法回顾性分析5例经手术病理证实的脑内型表皮样囊肿患者的CT和MRI影像资料。5例患者均行CT平扫检查,其中4例行CT增强检查。5例患者中4例行MRI平扫检查,其中2例行MRI增强检查。结果 5例中,3例位于小脑半球,1例位于基底节区,1例位于额叶。肿瘤呈不规则形或分叶状,与周围组织分界清晰。CT平扫为较均匀或轻度不均匀低密度,CT值-22～26 HU之间。MRI平扫T1WI上肿瘤呈不均匀低信号,内部可见散在絮状略高信号;T2WI及液体衰减反转恢复(FLAIR)图像上呈不均匀高信号。CT及MRI增强检查病灶均无明显强化。结论脑内型表皮样囊肿的CT、MRI表现较具有特征性,尤其是MRI对其诊断有重要价值。     

Vergleich der Wertigkeit der Computertomographie und der Magnetresonanztomographie in der Diagnostik der akuten intrazerebralen Blutung

BACKGROUND AND PURPOSE: Stroke symptoms are caused in 10 to 15% by intracerebral hemorrhage. From the clinical examination it is often impossible to differentiate intracerebral hemorrhage from cerebral ischemia. To exclude intracerebral hemorrhage as the cause of clinical symptoms a CT is usually performed. The aim of our study was a direct comparison of the sensitivity of Computed Tomography and MRI using different MR sequences for the detection of acute intracerebral hemorrhage. METHODS: In 8 male Wistar rats intracerebral hemorrhage was induced by infusion of collagenase into the caudate nucleus. After 1hour the brains were subsequently imaged with CT and MRI using T2- and T1-weighted Spin Echo sequences, diffusion-weighted sequences, T2*-weighted gradient echo sequences and FLAIR-sequences. Visibility of the intracerebral hemorrhage was examined using a scoring system from 1 = not visible to 5 = excellent visible. Finally, the intracerebral hemorrhage was verified by histological staining. RESULTS: In all animals, intracerebral hemorrhage was visible in T2*-weighted gradient echo and diffusion weighted MR images 1 h after infusion of collagenase. T2- and PD-weighted SE images were positive in 7/8 rats. T1-weighted images revealed signal changes in 5/8 rats, and FLAIR sequence was positive in 8/8 rats. In CT intracerebral hemorrhage was only visible in 3/8 rats. When measuring the increase of Hounsfield units within the suspected hemisphere we saw a mean increase of 7% compared to the normal hemisphere in 3/8 rats. CONCLUSIONS: In this animal model, T2*-weighted magnetic resonance imaging proved to be the most sensitive imaging modality in the detection of acute intracerebral hemorrhage and is by far more sensitive than CT.     

Rhinocerebral mucormycosis: MR manifestations

Magnetic resonance (MR) examinations of three patients with rhinocerebral mucormycosis are reviewed. The clinical course is outlined and the MR characteristics are analyzed in light of the known pathology. The major MR findings include sinus and orbital disease followed by deep facial extension. Involvement of basal portions of the hemispheres, brain stem, and hypothalamus occurred rapidly following ipsilateral facial or orbital invasion in all three cases. Regions of intracerebral inflammation were hyperintense compared with normal parenchyma on T2-weighted and proton density-weighted images. Septic cavernous sinus and internal carotid artery thrombosis was diagnosed by MR in one case. Magnetic resonance demonstrated partial resolution of intracerebral abnormalities that accompanied clinical improvement in the one surviving patient.     

Intracerebral hematoma developing during MR examination

We report a case of a 78-year-old woman with cerebellar infarction who developed intracerebral bleeding during the magnetic resonance (MR) examination. The intensity of the hematoma was heterogeneous corresponding to the heterogeneous density shown on CT study that immediately followed the MR examination.     

成人白血病中枢神经系统并发症的CT与MRI表现

目的 探讨成人白血病中枢神经系统并发症(CNSCL)的CT和MRI表现及其诊断价值.方法 回顾性分析18例经临床及手术病理证实的成人CNSCL的CT和MRI表现,其中急性淋巴细胞白血病7例,急性非淋巴细胞白血病10例,慢性粒单细胞白血病1例.CT平扫11例,其中增强1例;MR平扫16例,其中增强11例.结果 颅内受累14例:(1)颅内出血7例,其中脑内血肿4例,脑内血肿合并微出血1例,微出血2例.脑内血肿均为多发病灶.CT表现为团状高密度影;MRI表现为T1WI低信号或高低混杂信号,T2WI高信号或等高信号伴环状低信号环,病灶呈环形强化或无明显强化.脑微出血在磁敏感加权成像(SWI)上表现为多发斑点状及小条状低信号,其病灶检出率明显优于CT及MRI其他常规序列检查;7例中,伴脑梗死及蛛网膜下腔出血各1例.(2)颅内肿块5例:其中左额部内板下梭形病灶或跨颅板肿块2例,T1WI呈低信号,T2WI呈高低混杂信号,并有明显均匀强化,均见脑膜尾征;鞍区肿块1例,CT示鞍区高密度影,MRI示鞍区T1WI稍低信号,T2WI高信号,有不均匀强化;右侧脑室体旁肿块1例,T1WI、T2WI均呈等信号,有明显均匀强化.左额顶叶壁厚囊性肿块1例,呈环形强化.(3)梗阻性脑积水1例,表现为中脑导水管以上脑室系统扩张.(4)脑膜病变1例,MRI表现为广泛脑膜增厚伴明显均匀强化.椎管内病变4例:其中胸腰椎左侧椎旁软组织肿块2例,侵犯椎管内,伴邻近肋骨骨质破坏1例;椎管内肿块1例,表现为胸椎管后方梭形T1WI等高信号,T2WI等低信号灶,无明显强化;胸髓信号异常1例,表现为胸髓条状T2WI及液体衰减反转恢复(FLAIR)序列高信号影.结论 成人CNSCL影像表现多种多样,CT与MRI对该病的诊断价值相辅相成;白血病患者疑脑内病变者,建议常规使用SWI检查,以尽早发现脑微出血,降低脑内血肿发生的风险.

Abstract：

Objective To evaluate the CT and MRI findings and their diagnostic value of central nervous system complications of leukemia (CNSCL). Methods The CT and MRI findings of 18 adult patients with CNSCL proved by clinical features or pathology were retrospectively analyzed. Among 18 cases,7 were acute lymphocytic leukemia, 10 acute non-lymphocytic leukemia and 1 chronic myelomonocytic leukemia. Eleven cases underwent plain CT scan with one of them also receiving contrast-enhanced CT scan enhancement, 16 cases underwent plain MR scan with 11 of them receiving contrast-enhanced MR scan.Results Intracranial lesions in 14 cases: (1)intracranial hemorrhage was found in 7 cases, including intracerebral hematoma in 4 cases, micro-haemorrhage in 2 cases, and intracerebral hematoma accompanying by multiple intracerebral micro-haemorrhage foci in 1 case. All cases with intracerebral hematoma showed multiple lesions, which demonstrated high-density on CT images, and low or mixed signal on T1 WI, high- or intermediate signal with low-signal rim on T2 WI and ring enhancement or no evident enhancement. Microhaemorrhage manifested as multiple mini-mottling and strip hypointense foci on susceptibility weighted imaging, on which the detection rate of micro-haemorrhage foci was much higher than that on CT and other sequences of MRI. Among the 7 cases, one also had cerebral infarction and one subarachnoid hemorrhage.(2) Intracranial mass was found in 5 cases, among which two appeared as masses under or bestride cranium in the left frontal region with hypointensity on T1 WI, mixed signal on T2WI, strong homogeneous enhancement and dural tail sign;one showed a mass in saddle area, with high density on CT, slightly low signal on T1WI, high signal on T2WI and heterogeneous enhancement; one case displayed a mass near lateral ventricle with iso-intensity on T1 WI and T2WI and strong homogeneous enhancement; and one case manifested as cystic mass in the left fronto-apical lobe, with thick wall and ring enhancement (3)Obstructive hydrocephalus was found in 1 case, manifesting dilation of ventricles above the aquaeductus mesencephali. (4) Meningopathy was found in 1 case, manifesting diffuse thickening of meninges with strong homogeneous enhancement on MRI. Pathological changes of spinal canal was found in 4 cases among which two showed para-spinal mass involving vertebral canal and causing bone destruction of adjacent ribs; one case showed fusiform mass posterior to vertebral canal with high and intermediate signal on T1 WI and low and iso-signal on T2WI without enhancement; one showed zonale leison in thoracic cord with high signal on T2WI and fluid attenuated inversion recovery. Conclusion The radiologic manifestations of adult CNSCL are various and the role of CT and MRI for the diagnosis of CNSCL may complement each other. SWI is suggested as routine examination for patients of leukemia, in whom intracerebral lesions were suspected in order to find micro-haemorrhage as early as possible and reduce the risk of intracerebral hematoma occurrence.     

MR imaging after surgery for vertebrobasilar aneurysm

We examined the safety and utility of high-field MR in patients who had surgery for cerebral aneurysms of the vertebrobasilar system. Eighteen posterior (and three coincidental anterior) circulation aneurysms were treated. Twenty-one MR scans were obtained at a mean postoperative interval of 7.2 days. The mean size of the preoperative vertebrobasilar aneurysm was 2.2 cm; six were giant (greater than 2.5 cm) and eight were large (greater than 1.5, less than or equal to 2.5 cm). In 17 patients, Sugita nonmagnetic clips were used. In one other, a Drake tourniquet was used. No ill effects occurred from scanning with a high-field imaging unit at 1.5 T. The MR clip artifact was much less obtrusive than that on CT. In 11 cases, the aneurysm could be partially imaged postoperatively, mainly in very large aneurysms or in those treated by clipping the parent vessel. Of these, two revealed residual lumina on MR and nine looked completely thrombosed. Postoperative angiography showed that in four of the thrombosed-appearing aneurysms a residual lumen with a mean diameter of 1.0 cm had been missed. In the patient imaged after application of a Drake tourniquet, no artifact was seen, and a good assessment of progressive partial thrombosis was obtained. Evolution of the signal intensity of new aneurysm thrombus, in those minimally or not obscured by artifact, coincides with patterns previously described for hemoglobin in intracerebral hematomas. The earliest hyperintensity could be seen in either the periphery or the center of the new thrombus. All 15 patients examined with new postoperative deficits showed appropriate lesions, mainly small brainstem ischemic foci. Postoperative CT (performed in all but four of these patients) missed over 80% of these lesions, mainly owing to artifact from clip or bone. We conclude that MR is better than CT in the postoperative assessment of aneurysm patients, particularly in demonstrating small zones of ischemia. High-field MR scanning is safe if nonmagnetic surgical clips are used. MR is not accurate in assessing residual lumina.     

CT and MR imaging features of intracerebral epidermoid--a rare lesion

We present a rare case of intracerebral epidermoid cyst with partial calcification on CT and a characteristic hyperintense signal on diffusion-weighted MR imaging (DWI). MR imaging with DWI may help to accurately distinguish the lesion from other cystic tumours of the brain.     

特发性甲状旁腺机能减退症颅脑CT及MRI表现

目的探讨颅脑CT及MRI检查对特发性甲状旁腺机能减退症(IHP)的诊断价值。方法回顾性分析16例经临床确诊的IHP患者头颅CT(16/16)和MRI(3/16)表现,观察病变的范围和密度/信号等特点。结果IHP颅内主要表现为多发钙化性病变,在CT上表现为高密度,CT值114～373HU,在MRT1WI呈稍高信号或高信号,T2WI呈等信号。双侧尾状核、苍白球、壳核及丘脑的对称性、条形或团块状钙化16例;双侧额、颞、顶、枕叶皮层下钙化10例;小脑齿状核钙化6例(双侧4例,单侧2例);侧脑室旁钙化2例。结论CT和MR对IHP的诊断非常重要,其中CT对病变的显示优于MR,与临床结果结合,对IHP具有定性诊断意义。     

GRE-T_2~＊ WI在辅助诊断脑淀粉样血管病的应用研究

目的：探讨脑实质出血在CT及磁共振梯度回波（GRE）T2＊WI上的表现及GRE-T2＊WI在辅助诊断脑淀粉样血管病的作用。方法：CT证实为急性脑实质出血的20例患者,分为基底节区出血组和皮质-皮质下出血组,发病48h内行磁共振GRE-T2＊W I检查,并进行简易智能量表（MMSE）评分,对CT及T2＊WI征象、MMSE评分结果以及患者的相关信息进行总结并分析。结果：皮质-皮质下组高血压病患者比例明显低于基底节区组,且其MMSE评分明显高于基底节区组。两组病灶在GRE-T2＊W I上均表现为沿病灶边界清楚的极低信号,或边界清楚的低信号环,内部为略高信号或低信号区内混杂小点、斑片状高信号。两组在各自病灶周边或对侧都可见到多发的点状低信号,但皮质-皮质下组数目明显多于基底节区组。在皮质-皮质下组,有更多的病例出现有多灶出血及复发出血。结论：GRE序列对脑出血的敏感性高,成像快速,对微小动脉的点状出血诊断率明显高于CT。临床及CT检查怀疑脑淀粉样血管病脑出血的患者,可加做磁共振GRE-T2＊W I检查,以进一步提高对其诊断的准确性。     

Magnetic resonance applications in cerebral injury.

CT and MR imaging are complementary in the evaluation of cerebral head trauma. CT is still more useful for the initial evaluation of the acutely unstable patient who has a head injury. However, many lesions are identified by MR imaging such as cortical contusions, small subdural hematomas, and diffuse axonal injuries that may not be seen on CT examinations. In addition, MR angiography can play an important role in the diagnostic evaluation of the trauma patient. MR angiography can be clinically useful in delineating vascular abnormalities such as arterial occlusions, arteriovenous fistulae, dissecting aneurysms, and venous sinus occlusion. In pediatric trauma, MR imaging appears to be superior to CT in assessing head injuries, particularly those due to child abuse.     

Vertex epidural hematomas: imaging findings and diagnostic pitfalls

PURPOSE: Our purpose was to show the computed tomography (CT) and magnetic resonance (MR) imaging features of vertex epidural hematomas (EDHs) and emphasize pitfalls in the diagnosis of this entity. SUBJECTS AND METHODS: The neuroradiologic studies of four patients (CT in four, MR imaging and MR venography in one) were evaluated for EDH shape, size and appearance. RESULTS: EDHs were biconvex in three patients and crescentic in one patient. CT appearances included a collection that was hyperdense (two patients), generally isodense with a few regions of hyperdensity (one patient) and mixed hyperdense and hypodense (one patient). MR imaging findings in one patient consisted of hyperintense signal on T1-weighted images and hypointense signal on T2-weighted images. Inferior displacement of the superior sagittal sinus was seen in two patients. Diagnosis of a small vertex EDH was difficult on routine axial CT in one patient, but apparent on MR imaging and MR venography. CONCLUSIONS: Small vertex EDHs can be difficult to diagnose on routine CT. MR imaging or thin section CT should be performed to exclude the diagnosis in patients with trauma to the skull vertex.     

Systemic lupus erythematosus associated with marked intracranial calcification.

The authors describe a case of systemic lupus erythematosus associated with marked intracerebral calcification. The distribution of high signal on T1-weighted MR images was almost identical to the distribution of calcification on CT; however, the bodies of caudate nuclei with little calcification on CT also showed high intensities on T1-weighted images.     

Intracerebral schwannoma: CT and MR findings.

A case of intracerebral schwannoma in a 19-year-old man is reported. CT and MR findings were nonspecific, suggesting a primary glioma. The histologic features were of schwannoma.     

不典型颅内海绵状血管瘤的CT、MRI诊断初探

目的 探讨颅内海绵状血管瘤(ICA)的CT和MRI不典型表现.资料与方法 回顾性分析经手术病理证实的不典型ICA9例,男5例,女4例,年龄11～72岁,平均35岁.所有病例均行MRI平扫及增强检查,其中4例行CT扫描.结果 9例均位于脑内.病灶最大径平均值5.5cm.行CT检查的4例中,2例表现为等、高密度,2例表现为等、低密度;3例病灶内可见钙化.9例T1WI和T2WI呈混杂信号,周围低信号环4例,囊实性病灶5例,囊内见液平面3例,其中囊变伴附壁结节4例,6例出现明显灶周水肿.增强扫描8例呈明显不均匀强化,1例无明显强化.结论 发现瘤体巨大伴有囊性变、瘤体占位效应、病变多种形式的强化等ICA不典型的CT和MRI征象时,应考虑ICA的诊断.     

Intracerebral malignant melanoma: high-field-strength MR imaging

Thirteen patients with intracerebral malignant melanoma underwent high-field-strength (1.5-T) magnetic resonance (MR) imaging. The images were correlated with computed tomography (CT) scans (n = 7) and surgical specimens (n = 7). Most commonly, these lesions were hyperintense to normal white matter on T1-weighted images and hypointense to normal white matter on T2-weighted images. Hemorrhage in the lesion may have a greater influence on this unique appearance than does melanin. The increased tissue sensitivity of MR imaging allowed for 22% greater lesion detection than did CT.     

Preoperative evaluation of patients awaiting liver transplantation: comparison of multiphasic contrast-enhanced 3D magnetic resonance to helical computed tomography examinations

PURPOSE: To determine the feasibility of using a multiphasic magnetic resonance (MR) examination to evaluate the hepatic arterial anatomy and parenchyma in patients awaiting orthotopic liver transplantation (OLT). MATERIALS AND METHODS: Twenty consecutive patients awaiting OLT underwent multiphasic MR (using a T1-weighted 3D gadolinium-enhanced gradient-echo (GRE) sequence and two separate injections of contrast material) and computed tomography (CT) imaging; both imaging studies were performed within a 1-week period for each patient. Quantitative and qualitative assessment of the hepatic arterial system on MR data was performed. Two independent observers classified the hepatic arterial anatomy and evaluated the hepatic parenchyma from the MR data. The prospective CT interpretation was used as the gold standard. RESULTS: Overall qualitative rating of hepatic arterial system-to-background contrast on MR data was good to excellent (average pooled score of 2.00 +/- 0.27), with no significant difference between the two observers after the first or second injections of contrast material. Classification of hepatic arterial anatomy by MR angiography (MRA) and CT angiography (CTA) was concordant in 85% (17/20) of patients and discordant in 15% (3/20) of patients. Focal parenchymal lesions were detected in 25% (5/20) of patients by MR and CT; however, two lesions in one patient with multiple lesions were detected only with MR. CONCLUSION: Multiphasic T1-weighted 3D gadolinium-enhanced MR examination can provide comprehensive evaluation of the hepatic arterial anatomy and parenchyma in patients awaiting OLT. MR may offer an advantage over CT in the detection of focal parenchymal lesions.     

Sensitivity and specificity of fluid-blood levels for coagulopathy in acute intracerebral hematomas.

PURPOSETo characterize the imaging features of intracerebral hemorrhages in coagulopathies that alter prothrombin time or partial thromboplastin time.METHODSA fluid-blood level was defined as a horizontal interface between hypodense bloody serum layered above hyperdense settled blood. The prevalence of fluid-blood levels in acute intracerebral hemorrhages was determined on third-generation CT scans in 32 patients with elevation in prothrombin time or partial thromboplastin time. This was compared with the frequency of fluid-blood levels in 185 patients with intracerebral hemorrhage in which there was no laboratory evidence of coagulopathy.RESULTSThe probability of finding a fluid-blood level in an intracerebral hemorrhage of a patient with abnormal prothrombin time or partial thromboplastin time was 59% (sensitivity). The probability that there will be no fluid-blood level in a patient with a normal prothrombin time and partial thromboplastin time was 98% (specificity).CONCLUSIONFluid-blood levels in acute intracerebral hemorrhage are moderately sensitive to the presence of coagulopathy (ie, abnormal prothrombin time and partial thromboplastin time) and highly specific for this condition. Thus, an intracerebral hemorrhage with a fluid-blood level should prompt a thorough search for coagulopathy because early treatment of this condition may improve the 40% mortality in these patients. Caution should be used to distinguish the horizontal interface of a fluid-blood level from a clot with a flat top. A decubitus CT is useful in these rare instances.     

Local recurrence of rectal cancer: MR imaging before and after oral superparamagnetic particles vs contrast-enhanced computed tomography

The aim of this study was to compare three imaging strategies for the diagnosis of local recurrence of rectal cancer: (a) MR imaging; (b) MR imaging after administration of enteral superparamagnetic particles (Ferristene); and (c) contrast-enhanced CT. Seventeen patients with previous surgery for rectal cancer were examined, 12 patients with local tumour recurrence in the pelvis and 5 patients with postoperative changes. Pelvic multi-coil MR imaging before and after oral administration of superparamagnetic contrast medium [Abdoscan (Ferristene USAN), Nycomed-Amersham, Liding?, Sweden] as well as abdominal and pelvic CT was performed in all patients. The examinations were independently evaluated by three different radiologists. The general effect of the oral MR contrast medium, the delineation of normal and pathological structures as well as confidence in the diagnosis were registered on a visual analog scale (VAS). The diagnosis according to MR before and after oral contrast medium, and CT, was compared, in 16 patients, with the final diagnosis which was verified by biopsy (n = 3), surgery (n = 6), clinical follow-up (n = 4) and by follow-up with MR or CT (n = 3). No significant improvement in MR image quality was found after enteral contrast medium. The post-contrast MR diagnosis was not changed in any of the patients. The diagnosis on MR correlated with the final diagnosis in 12 of 16 patients (sensitivity 91%, accuracy 62%) and the diagnosis on CT in 11 of 16 patients (sensitivity 82 %, accuracy 56 %). The radiologists' "confidence" in the diagnosis and the degree of accordance with the final diagnosis did not score higher on MR after than before oral contrast administration; however, the accordance with the final diagnosis scored better on MR than on CT. No advantages of orally administered superparamagnetic contrast medium were observed in the examined patient group. Magnetic resonance is preferable to CT in diagnosing local tumour recurrence.