MR recognition of supratentorial tumors

Eighty patients with intrinsic tumors of the cerebral hemispheres and thalami were studied with a 0.5 T superconducting system and third- or fourth-generation computed tomographic (CT) scanners. Twenty-eight patients had histologically verified gliomas, 34 were presumed to have primary brain tumors on clinical grounds, 13 had metastases, and five were postoperative. Lesions shown on CT were equally well demonstrated on magnetic resonance (MR) imaging; more metastases were seen on MR than on CT images. MR revealed abnormal signals in 10 cases in which CT findings were equivocal. It was not possible to differentiate edema from tumor in many cases using the MR imaging sequences currently available. The histologic types of the tumors could not be determined from the MR appearances.     

MR imaging of cerebral vascular malformations

Fifteen vascular malformations, including six supratentorial arteriovenous malformations (AVMs), three venous malformations, and six brainstem vascular malformations, were examined on 0.5 T magnetic resonance (MR) and GE 9800 and 8800 computed tomographic (CT) scanners. All the malformations were shown by MR, and the arterial and venous drainage of AVMs was precisely delineated. Hematoma was always differentiated from calcification by MR signal characteristics. Increased signal in the brain parenchyma was often seen adjacent to AVMs. The signal of blood within venous malformations altered with spin-echo techniques using various repetition times and was distinguished from rapidly flowing blood in AVMs that lacked signal in all imaging sequences. Brainstem malformations were seldom demonstrated by angiography. Hemorrhage was common and was invariably associated with multiple areas of absent signal that may have represented abnormal vessels. These appearances are distinct from those of intrinsic tumors and are probably pathognomonic of brainstem vascular malformations.     

CT和MRI对颅内表皮样囊肿诊断价值的评价

目的：评估CT和MRI对颅内表皮样囊肿的诊断价值，分析误诊原因，提高诊断水平。方法：44例经手术和病理证实的颅内表皮样囊肿，术前全部行常规MRI检查，其中19例行Gd-DTPA增强MRI检查；17例作CT平扫，其中12例作静脉注射增强CT检查。结果：颅内表皮样囊肿多位于桥小脑角池，本组病例中占34．9％(15／4例)；肿瘤多呈不规则形态，占70．45％(31／44例)；CT平扫多呈均匀低密度，占70．59％(12/17例)，造影后多无强化，占91．71％(11／12例)；MRT1加权像上多呈均匀低信号，但略高于脑脊液，T2加权像上多呈均匀高信号，占61．36％(27／44例)，Gd-DTPA增强后多无强化，占84．21％(16／19例)。肿瘤周围的脑组织均无水肿，占100％，肿瘤较大时可以挤压、推移周围脑组织或脑室结构，引起比较明显的占位效应，占70．45％(31／44例)；肿瘤较大时，很少引起阻塞性脑积水。结论：颅内表皮样囊肿在CT和MRI像上有特征性表现，MRI无论在定位和定性诊断上优于CT，Gd-DTPA的应用有助于颅内囊性占位的诊断与鉴别诊断。     

肾嫌色细胞癌:动态增强CT及MR表现

目的:分析肾嫌色细胞癌的影像学表现及其血液动力学特征与病理的关系,提高诊断准确性.方法:经手术病理证实的肾嫌色细胞癌16例,术前经螺旋CT或多层螺旋CT平扫、皮髄交界期和实质期扫描,注射流率3 ml/s;3例经MRI SE T1WI、T2WI和扰相梯度回波动态增强成像.仔细复习CT和MRI扫描结果并与手术病理作回顾性对照分析.结果:16例嫌色细胞癌中肿瘤呈球形14例,椭圆形2例,边缘光整.所有肿瘤平扫软组织密度均匀,3例可见钙化,1例瘢痕伴钙化.肿瘤直径3.5～13.0cm,平均7.6cm.实质性肿瘤15例,1例实质期增强可见小囊变.肿瘤平扫CT值22.7～34.2 HU,平均27.1 HU;动态增强皮髓交界期CT值30.4～71.8 HU,平均43.3 HU;实质期CT值32.9～82.4 HU,平均51.7 HU.4例可见轮辐状强化.3例行MRI检查,MR T1WI为略低信号,T2WI为略高信号,1例可见中心轮辐状瘢痕,皮髄交界期轻中度强化,实质期强化相仿.结论:肾嫌色细胞癌多位于髓质,瘤体呈球形,坏死囊变很少见,瘤肾分界截然;皮髄交界期强化低于、等于或高于肾髓质,但明显低于肾皮质,实质期强化多低于或等于皮髄交界期,少数高于皮髄交界期;轮辐状强化或轮辐状中心瘢痕超过1/3.     

MR imaging of syringomyelia and hydromyelia

The relative effectiveness of plain computed tomography (CT), metrizamide CT, conventional myelography, and magnetic resonance (MR) imaging was compared for the examination of cystic spinal cord lesions. Intramedullary cavities in 18 patients were demonstrated by MR imaging: cavities were uncomplicated in 13 patients, associated with spinal tumors in two, and studied after occipital craniectomy for treatment of Chiari malformation and syringomyelia in two. Cavities were shown by MR imaging in all enlarged spinal cords, but a cavity was shown in only one of four small cords. The rostral limits of the cavities were demonstrated better than were the caudal extensions. Ventricular communication was not demonstrated. Chiari malformation was shown only in cavities that did not involve the medulla. Syringes associated with tumor were indistinguishable from uncomplicated cavities, but the tumor had abnormal signal on long spin-echo sequences in two cases. Cystic cord tumor (one case) had an inhomogeneous appearance. Caudal displacement of the cerebellar hemisphere through the surgical defect associated with compression of the fourth ventricle was shown in two cases after posterior fossa craniectomy. Thirteen patients were studied with metrizamide CT also. MR imaging proved to be as accurate as metrizamide CT in the diagnosis of intramedullary cavities that result in spinal cord enlargement, but it was less sensitive in detecting cavities within normal-sized or diminished spinal cords. It had the advantage that tumor tissue could be distinguished from associated syrinx cavities by differences in signal characteristics; and cerebellar ectopia was evaluated easily on sagittal MR views.     

Imaging of pancreatic neoplasms: comparison of MR and CT

Thirty-two patients with pathologically proved pancreatic carcinomas or cystadenomas were evaluated with MR images obtained with T1-weighted spin echo (short TR/short TE), inversion recovery, and T2-weighted spin-echo (long TR/long TE) pulse sequences. CT was used as the reference standard to determine the ability of MR to delineate normal and abnormal pancreatic anatomy and thereby to exclude or detect pancreatic malignancy. Short TR/short TE spin-echo sequences were significantly better (p less than .05) than inversion recovery or T2-weighted spin-echo sequences in resolution of both normal and abnormal anatomy. Resolution of pancreatic anatomy correlated (r = .9) with the image signal-to-noise ratio. In seven (22%) of 32 cases, MR visualized pancreatic tumors better than CT did because it showed a signal intensity difference between the tumor and normal pancreatic tissue. Overall, the slight superiority of MR over CT for tumor visualization tended to occur in larger tumors and was not statistically significant. On T1-weighted images, 63% (20 of 32) of pancreatic tumors studied had lower signal intensities than normal pancreatic tissue, whereas on T2-weighted sequences (TE = 60, 120, and 180 msec) only 41% (13 of 32) of tumors had increased signal intensities. Currently available MR imaging techniques offer no significant advantages over CT for evaluating the pancreas for neoplasia.     

Brain radiation lesions: MR imaging

This retrospective study was performed to assess the capability of magnetic resonance (MR) to depict and characterize diffuse and focal radiation lesions in the brain using the spin-echo technique. The MR images of 55 patients who had undergone radiation therapy were reviewed. Comparative computed tomography (CT) studies were available for all the patients. Normal white matter was chosen as reference tissue for the quantitative comparison of signal intensities. Radiation lesions (identified in eight patients) were seen as regions of high signal intensity on the sequence with a long repetition time (TR) (2.0 sec) and showed no difference in signal compared with white matter when the TR was short (0.5 sec). Nonspecific prolongation of T1 and T2 relaxation times was measured in such lesions. In one patient, subependymal tumor spread, demonstrated by contrast-enhanced CT, was missed on MR images, masked by the adjacent abnormal signal owing to radiation effects. Recurrent or residual brain tumor could not be distinguished from radiation brain necrosis either by CT or by MR imaging. It is concluded that MR can depict radiation lesions with great sensitivity but is not very helpful for discrimination between recurrent or residual brain tumor, radiation necrosis, and other brain lesions.     

Hepatocellular carcinoma: MR imaging

Sixty patients with hepatocellular carcinoma (HCC) were studied with computed tomography (CT) and magnetic resonance (MR) imaging at 1.5 T. MR imaging was equivalent to CT in detection of HCC. MR imaging was superior to CT in demonstrating the details of tumors, especially pseudocapsules. In 58 cases, main tumors were detected with MR imaging. On spin-echo (SE) 600/25 (repetition time msec/echo time msec) sequences, tumors were hyperintense in 18 cases, isointense in ten, and hypointense in 30. On SE 2,000/60 sequences, all but two tumors had high signal intensity. Pseudocapsules, intratumoral septa, daughter nodules, and tumor thrombi, which are important characteristics of HCC, were demonstrated in 22, three, six, and six cases, respectively, on MR imaging. MR imaging is useful for characterizing the internal architecture of HCC.     

Intracranial hemangioblastomas: CT and MR findings

The CT and magnetic resonance (MR) findings in eight patients with 10 biopsy-proven intracranial hemangioblastomas were reviewed. Three of these patients had von Hippel-Lindau (VHL) syndrome. Nine tumors were infratentorial, seven were cystic, and five had well-defined mural nodules. The only three solid tumors, the only brain stem tumor, and the only supratentorial tumor in this series occurred in VHL patients. Magnetic resonance detected a single tumor missed by CT, and no lesion seen on CT was missed by MR. The tumor nodule, when present, was identified in every case using MR, although it was usually more apparent on contrast-enhanced CT. In three cases MR was better than CT in defining the margins of posterior fossa tumors. Serpentine vessels were well seen as flow voids against high signal cyst or tumor on T2-weighted images, but contrast-enhanced CT also demonstrated them. Magnetic resonance was found superior to CT for the detection of intracranial hemangioblastomas, and complementary in their characterization.     

中枢性原始神经外胚层肿瘤的CT和MRI表现

目的探讨中枢性原始神经外胚层肿瘤(primitive neuroectodermal tumor,PNET)的影像表现特征,以提高对此病的认识。方法回顾性分析经手术病理证实的9例PNET患者的CT和MRI资料。结果发生于大脑半球7例,脑干及松果体区各1例。9例病灶边界均清晰,密度或信号不均匀。CT平扫实质部分与脑灰质等或稍高密度,MRI上T1WI呈与脑灰质等或稍低信号,T2WI呈等或稍高信号。7例无或轻度瘤周水肿;6例有明显占位效应;瘤内出血6例,钙化5例;6例见流空血管信号穿行,6例与侧脑室关系密切。5例与局部硬脑膜相连,其中2例邻近骨质变薄,增强扫描多明显强化。结论 PNET影像学表现有一定特征性。     

泪腺良性混合瘤的CT和MRI诊断

目的 探讨CT和MRI对泪腺良性混合瘤的诊断价值. 资料与方法 回顾性分析45例经病理证实的泪腺良性混合瘤的临床和影像学资料,30例行CT检查,35例行MRI检查. 结果 45例中,起源于泪腺眶部43例,泪腺睑部2例.肿瘤呈椭圆形29例,圆形10例,不规则形6例;边缘光滑30例,边缘不规则呈分叶状或结节状15例.CT表现为等密度,大多数密度均匀.眶壁骨质受压、凹陷或缺损22例,骨质破坏伴眶壁硬化、肥厚6例,骨质增生硬化14例.MR T1WI上呈低信号25例,等信号10例,T2WI上呈高信号21例,等信号14例,增强后肿瘤呈中度至明显强化,大多数强化均匀. 结论 泪腺良性混合瘤的CT和MRI表现有一定特征,CT和MRI结合可以提高病变诊断的准确性.     

Longitudinal stress fractures of the tibia: diagnosis by magnetic resonance imaging

 Objective. Previous works describe magnetic resonance (MR) imaging characteristics of stress fractures. Diagnosis of the atypical, longitudinal type of stress fracture has been reported using computed tomography (CT). This report focuses on MR imaging of longitudinal stress fractures of the tibia. Materials and methods. Six cases are presented in which a longitudinal linear abnormal marrow signal was detected in the middle and distal parts of the tibial shaft. Five patients were imaged using a 1.5 Tesla MR unit. Axial, sagittal and coronal T1 and T2-weighted or fat suppressed proton density fast spin echo images were obtained in all but one patient. One patient was imaged using a 0.5 Tesla MR unit with axial and coronal T1- and T2-weighted sequences. Initial conventional radiographs seen at clinical presentation were interpreted as normal in all cases. Two patients underwent radionuclide bone scan, and one patient was imaged with CT prior to MR imaging. Results. In each instance, MR imaging demonstrated linear marrow signal abnormalities orientated along the long axis of the tibial shaft. Endosteal and periosteal callus was identified on axial images. In all cases, MR imaging clearly demonstrated a fracture extending through one cortex with abnormal signal in both the marrow cavity as well as adjacent soft tissues indicating edema. Conclusion. MR imaging was shown to be excellent for demonstration of fracture lines, callus, and marrow and soft tissue abnormalities seen in association with longitudinal stress fractures.     

Localized 1H NMR spectroscopy in fifty cases of newly diagnosed intracranial tumors.

Fifty patients with newly diagnosed, untreated intracranial tumors were examined with 1H nuclear magnetic resonance single-volume spectroscopy (MRS) using a 1.5 T whole-body MR system. Prior to the MRS, contrast enhanced MR and/or CT imaging studies were carried out. Histological verification was obtained in all patients except one. All tumor spectra revealed distinct abnormalities as compared with the normal brain spectra. Although most meningiomas showed a rather characteristic spectral pattern, generally features specific for the various tumor types were not observed. For instance, though a strong lactic acid signal was seen in most malignant tumors, this signal was also evident in five benign neoplasms.     

良性泪腺混合瘤CT、MR诊断价值

目的:探讨良性泪腺混合瘤CT和MR诊断价值。方法:对12例经手术及病理学证实的良性泪腺混合瘤患者进行回顾性分析,观察其CT及MR表现的特点。结果:12例患者中,类圆形8例,椭圆形4例。肿瘤位于眼眶上、外方,眼球受压向下内移位。肿瘤边界清晰,周围泪腺窝骨质膨胀变薄。CT表现为肿块与脑组织密度相似,等密度均匀8例,密度不均匀4例。MR表现为T1WI呈低信号,T2WI及脂肪抑制相呈高信号。增强扫描肿瘤明显强化8例,4例轻中度强化。结论:CT、MR可清晰地显示泪腺混合瘤的形态、大小、密度等,具有一定特征性,为该病诊断和鉴别诊断提供了可靠的诊断依据。     

Benign pleomorphic adenomas of the salivary glands: surface coil MR imaging versus CT

High resolution magnetic resonance (MR) imaging of three salivary gland tumors was performed at 1.5 T and compared with CT. Two of the three tumors were well seen on CT. However, one required CT sialography to separate tumor from the remaining parotid parenchyma, and, in the other, soft tissue invasion could not be excluded on the basis of CT. Magnetic resonance imaging demonstrated sharp tumor margins with no evidence of invasion. All three tumors were pathologically proven benign pleomorphic adenomas confirming the MR findings. On T2 weighted images, the two large adenomas demonstrated inhomogeneity that was not observed on CT.     

The role of MR and CT in evaluating clival chordomas and chondrosarcomas

Sixteen chordomas and nine chondrosarcomas of the clivus were evaluated with CT and MR either before (22 cases) or after (three cases) treatment with proton beam irradiation. The ability of these imaging techniques to provide information necessary to direct patient treatment was studied. The tumor was detected and its gross margins were identified by both techniques in all instances. No reliable diagnostic features allowing differentiation between these two tumors were encountered. MR generally was superior in defining the exact position of the brainstem and optic chiasm relative to the tumor, and it frequently provided superior information about tumor extension into the nasopharynx and cavernous sinus. CT was always better than MR in demonstrating tumoral calcification and in defining the exact anatomy of bone destruction. MR was generally superior to CT in demonstrating the position of the cavernous internal carotid artery relative to the tumor and often provided superior visualization of the vertebral and basilar arteries. In cases in which bone-induced artifact obscured the interface between the neural axis and tumor in the CT image, or in which the tumor had suprasellar extension and was likely to compress the optic chiasm and tracts, MR was of great value in planning irradiation therapy. The high occurrence of clinically asymptomatic signal intensity alterations in the MR studies of previously treated patients appears to limit the differential diagnostic value of this information. Given its greater availability and lower cost, CT appears to be the technique of choice for routine follow-up of previously treated patients.     

Giant cell tumor of the proximal tibia: MR and CT appearance

The magnetic resonance (MR) appearance of four cases of giant cell tumor (GCT) of the proximal tibia are described and the MR grading of these tumors is compared with CT and conventional radiography. Magnetic resonance showed the lesions to be well defined with respect to adjacent marrow and cortical bone. Homogeneous intermediate signal intensity or low signal within the tumors was seen on T1-weighted images. T2-weighted images showed mixed signal intensity with small "bright patches" of increased signal intensity in all four cases. No fluid levels were identified. Magnetic resonance was superior to CT and plain radiography in radiologic grading of the tumors. Computed tomography was superior in determining if cortical invasion was present. Intraarticular tumor extension was more accurately detected by MR and arthrotomography than CT. An MR manifestation of GCT of the proximal tibia is described which may be a common appearance of this tumor by this modality. Magnetic resonance is the procedure of choice in the radiologic grading of GCT.     

Primary thyroid lymphoma: MR appearance

Magnetic resonance imaging was evaluated in six patients with primary thyroid lymphoma. Five patients had a solitary localized tumor and one had multiple tumors. These masses showed homogeneous iso- or high intensity compared with the uninvolved thyroid tissue on T1-weighted images and homogeneous high intensity on T2-weighted images. Diffuse lobulated goiter with homogeneous intensity was seen in the sixth case, where the differentiation between lymphoma and Hashimoto thyroiditis was impossible. Extrathyroidal tumor extension occurred in two cases and cervical lymphadenopathy in one case. In five of six cases, identification and staging of primary thyroid lymphoma were possible with MR imaging. Magnetic resonance imaging was comparable to CT in the detection of tumors (five cases), extrathyroidal extension (two cases), and cervical lymphadenopathy (one case). In three cases, the pseudocapsule (a low-intensity band forming the border between tumor and thyroid tissue) was detected only by MR imaging. In one case, the discrimination between tumor and uninvolved thyroid gland was clearer on MR imaging than on CT.     

胚胎发育不良性神经上皮肿瘤的影像学诊断

目的探讨胚胎发育不良性神经上皮肿瘤（DNT）的影像学特点。资料与方法回顾性分析经病理证实的7例DNT的影像学表现。7例中5例行CT平扫;7例均行MRI平扫,其中5例同时行MRI增强扫描;2例行”FFDG正电子发射体层摄影（PET）检查。结果7例中5例位于颞叶,1例位于顶叶,1例同时累及额颞叶;病变均位于皮层区。CT像上4例呈均匀低密度,1例呈低、等混杂密度,其中3例可见邻近颅骨变薄;MRI上病变呈均匀或不均匀长T1、长T2信号,除1例外其他均无明显的占位效应和周围水肿;MRI增强检查3例无明显强化,2例可见结节状或点状强化;PET检查2例均呈低代谢。结论DNT的临床和影像学表现有一定特点,联合应用多种影像学检查方法有助于病变的术前诊断。     

Magnetic resonance imaging of intracranial epidermoids: report of two cases

Intracranial epidermoids are uncommon benign tumors in the subarachnoid spaces. We have studied two patients with these tumors originating in the basal cisterns using magnetic resonance (MR) imaging, computed tomography (CT), and cerebral angiography. Both CT and MR showed the extraaxial position of these tumors and their extension into the posterior fossa well. Angiography did not show any abnormal vasculature but displacement of vessels by the tumor mass was well demonstrated. MR was found to be relatively specific in characterizing these tumors.