鞍区毛细胞型星形细胞瘤的MRI特征

MRI features of pilocytic astrocytoma in sellar region

目的探讨鞍区毛细胞型星形细胞瘤的MRI表现特征。方法回顾性分析20例经病理证实的鞍区毛细胞型星形细胞瘤的MR平扫及增强资料。结果本组鞍区毛细胞型星形细胞瘤呈实性、囊实性病灶,MR平扫为等长T1、长T2信号;2例合并出血者可见不均匀短T2信号。将其余18例患者按照肿瘤实性成分均匀性分成均匀和不均匀两组,分析其内部成分的MRI特征。均匀组6例,肿瘤实性部分信号较均匀,可见多发微小囊变,增强后实性部分强化均匀或不均匀,囊变区可强化或不强化;不均匀组12例,肿瘤实性部分信号不均,可见大小不等的不同信号区,其中6例不同信号区边缘可见类似"间隔"样结构,9例肿瘤边缘可见单个囊状或多个新月状囊变区;增强后肿瘤实性部分不同信号区强化幅度与T1WI信号高低成反比,"间隔"样结构及肿瘤边缘囊变区无强化。结论肿瘤实质成分不均匀的鞍区毛细胞型星形细胞瘤中实性部分大小不等的不同信号区及其强化的方式反映了其病理特点,有一定的特征性,MRI对本病的术前诊断有重要参考价值。

Objective To analyze the MR imaging features of pilocytic astrocytoma in sellar region. Methods Pre-and-post contrast MR images of 20 patients with pathologically proved pilocytic astrocytoma in the sellar region were retrospectively reviewed. Results Solid or solid-cystic change and presented iso-or long T1 and long T2 signal on MRI were found. Of 20 patients,2 had hemorrhage showing mixed short T2 signal,and the other 18 patients were divided into 2 groups depending on the homogeneity of the solid part of the tumor on MRI. The solid part of tumor in 6 patients showed homogeneity,and presented comparatively homogeneous signal,and multiple microcysts could be found. After contrast administration,the solid part showed uniform or non-uniform enhancement,while the cystic part showed either enhancement or non-enhancement. The solid part of tumor in 12 patients presented heterogeneous signal,and the abnormal signal intensity were different in size. In the border of the abnormal signal intensity area,＂septa＂ structures were found in 6 patients,while single cystic change or multi-crescent-like capsules were found in 9 patients. After contrast administration,the extent of the enhancement in different area of the solid part of tumor was inversely proportional to that of signal intensity on T1WI. ＂Septa＂ structures and cystic part showed no enhancement. Conclusion The abnormal signal area varying in size in solid part of pilocytic astrocytoma in sellar region,and modalities of enhancement of the tumor can reflect the characteristics of the tumor pathologically. This feature is extremely valuable in diagnosis of pilocytic astrocytoma in sellar region even before operation.