摘要： 目的  探讨磁敏感加权成像（SWI）技术在脑弥漫性星形细胞瘤分级中的诊断价值。方法  43 例脑弥漫性星形细胞瘤患者分别于术前行横断面MRI 常规T1WI、T2WI、FLAIR 序列和横断面磁敏感加权成像（SWI）检查，观察SWI 序列对肿瘤小血管和出血灶（微小性出血及非微小性出血）的显示能力，分析在SWI 序列上不同级别星形细胞瘤肿瘤实质信号、小静脉分布及肿瘤出血灶特点，计数和比较不同级别星形细胞瘤肿瘤小静脉数目、微小性出血灶数目和非微小性出血面积。结果  SWI 序列对肿瘤小血管和微小性出血灶数目，以及非微小性出血面积的显示优于常规扫描序列，且差异有统计学意义（均P < 0.01）。在SWI序列上，Ⅱ级星形细胞瘤肿瘤实质部分以高信号为主，小静脉分布稀疏，出血少见；Ⅲ级和Ⅳ级星形细胞瘤以等和稍低信号为主，小静脉密集分布，均伴有出血。Ⅱ ~ Ⅳ级星形细胞瘤肿瘤小静脉计数分别为（3.77 ± 1.11）、（11.86 ± 1.22）和（20.00 ± 1.32）根，肿瘤微小性出血灶计数分别为（0.47 ± 0.39）、（3.32 ± 0.42）和（4.38 ± 0.46）个，肿瘤非微小性出血面积分别为（0.78 ± 1.31）、（3.05 ± 4.40）和（4.23 ± 4.55）cm²，组间总体差异均有统计学意义（均P < 0.01）。结论  SWI 序列对脑弥漫性星形细胞瘤肿瘤小血管和出血灶的显示优于常规MRI序列；不同级别星形细胞瘤肿瘤实质信号特点、小静脉分布特点和出血情况各异；计数和测量肿瘤小静脉和微小性出血灶数目，以及非微小性出血面积有助于星形细胞瘤的准确分级。

关键词: 星形细胞瘤, 磁共振成像, 脑肿瘤

Abstract: Objective To investigate the diagnostic value of susceptibility-weighted imaging (SWI) in grading diffusely infiltrating astrocytomas. Methods Forty-three patients with pathologically proven diffusely infiltrating astrocytomas were collected, and underwent preoperative MRI conventional sequences (including axial T1WI, T2WI and FLAIR) and axial SWI. The ability of showing intratumoral small vessels and hemorrhagic focuses were compared between SWI and conventional techniques. The signal intensities, distribution of venules and bleeding incidence of the tumors were observed respectively on SWI, and the numbers of intratumoral small vessels and cerebral microbleeds, and the sectional areas of bleedings were compared within the three grades of astrocytomas. Results There were significant differences between SWI and conventional sequences in displaying numbers of small vessels and microbleeds and sizes of bleedings (P < 0.01, for all). Low-grade astrocytomas (WHO Ⅱ) displayed mainly as hyperintense, while high-grade (WHO Ⅲ, Ⅳ) ones showed mainly equisignal or low intensities; venules inside low-grade astrocytomas were sparse, but abundant inside high-grade ones; the incidence of hemorrhage in low-grade astrocytomas was less frequent than that in high-grade ones. The numbers of venules in three groups were 3.77 ± 1.11, 11.86 ± 1.22 and 20.00 ± 1.32, respectively. The numbers of cerebral microbleeds were 0.47 ± 0.39, 3.32 ± 0.42 and 4.38 ± 0.46, respectively. The sectional areas of bleedings were (0.78 ± 1.31) cm2, (3.05 ± 4.40) cm2 and (4.23 ± 4.55) cm², respectively. The differences among the three groups were all statistically significant (P < 0.01, for all). Conclusion SWI was more sensitive than conventional techniques in showing small vessels and bleeding sites in astrocytomas. The signal intensities, distribution of venules and bleeding incidence of tumors were significantly different between low-grade and high-grade astrocytomas. The numbers of small vessels and cerebral microbleeds, and the sectional areas of bleedings may help to facilitate the grading of astrocytomas in clinical practice.

Key words: Astrocytoma, Magnetic resonance imaging, Brain neoplasms