原发性中枢神经系统淋巴瘤的CT及MRI表现

目的 探讨原发性中枢神经系统淋巴瘤（PCNSL）的CT及MRI表现特征,以提高术前对该病的影像诊断能力。方法 分析2008年1月—2009年8月华西医院16例经病理证实PCNSL患者的CT、MRI资料及病理资料。结果 病理检查均为B细胞来源的弥漫性大B细胞性淋巴瘤。16例PCNSL 29个病灶,单发11例（69%），多发5例（31%）18个病灶。病灶好发部位依次是大脑半球临近蛛网膜下腔12个（41.4%）、脑室周围深部白质7个（24.1%）、胼胝体3个（10.3%）。有5例病变CT平扫表现为等或略高于脑实质密度影,无出血和钙化；MRI平扫75.9%（19/25）的病灶T1WI呈等低信号,T2WI等稍低信号,类似“脑膜瘤”样信号,均未见血管流空；增强后病灶大都均匀实质团块状或结节状强化,典型的可出现“尖角征”、“握拳征”,3例可见小囊变,呈“硬环征”。结论 CT对PCNSL的定性诊断作用有限,MRI具有一定特征性表现者,多可作出正确的诊断,但确诊有赖于病理。

CT and MRI Manifestations of Primary Central Nervous System Lymphomas

Objective To evaluate CT and MRI manifestations of primary central nervous system lymphomas （PCNSL） in pathologically confirmed patients, so as to improve imaging diagnostic accuracy of PCNSL. Methods The CT and MRI findings in 16 patients with pathologically confirmed PCNSL were analyzed retrospectively from January 2008 to August 2009. Of these patients, 4 underwent CT plain scan, 9 had MRI examination, and 3 underwent both CT and MRI examinations. Results All patients were diffuse larger B-cell lymphoma of B cell lymphoma pathologically. Twenty-nine lesions were identified in 16 patients, 11 （69%） were identified to have solitary tumor loci and the other 5 （31%） presented a multifocal form with a total of 18 lesions. The most frequent locations were the cerebral hemispheres （41.4%）, periventricular white matter （24. 1~/00） and the corpus callosum （10. 3%）. In 5 cases, the tumor presented isodensity or slight hypodensity without hemorrhage or calcification on plain CT images. Nineteen （75.9~） lesions with isointense or hypointense signals on Tl-weighted and isointense or slightly hypointense signals on T2-weighted images were detected on MR Imaging of 12 cases （25 lesions）, which were similar to meningioma. All lesions showed no ＂blood flow＂. Most lesions presented obvious homogenous enhancement, the typical cases presented ＂incision sign＂ and ＂angular sign＂, especially for these lesions adjacent to the subarachnoid space. Three lesions were showed microcystic foci and the presence of ＂ring sign＂ after gadolinium injection. Conclusion CT imaging has limited values to qualitative diagnosis of PCNSL, and conventional MRI plays an important role to make accurate diagnosis in most patients with PCNSL, final diagnosis of the entity depended on pathology.