脑星形细胞肿瘤的MR灌注成像与病理对照

目的研究MR灌注成像在脑星形细胞肿瘤术前分级中的应用价值.方法32例脑星形细胞肿瘤病人依次行常规MRI平扫、MR灌注成像及增强MRI.MR灌注成像采用动态增强T2*WI梯度回波-回波平面成像序列(T2*WIGRE-EPI),造影剂用量为0.2mmol/kg,注射流率为3～4 mL/s.首先得到信号强度-时间曲线,并合成相对脑血流容积(rCBV)图,计算出最大rCBV比率.独立样本t检验用于评价两组数据的差异,P＜0.05认为有统计学意义.结果低级别星形细胞瘤(Ⅰ～Ⅱ)18例,高级别星形细胞瘤(Ⅲ～ⅣV)14例.低级别星形细胞瘤组最大rCBV比率为(2.57±0.78)1.44～4.88,高级别星形细胞瘤组最大rCBV比率为(5.40±0.63)4.76～7.07,两组之间比较有显著性差异(P＜0.01).结论MR灌注成像能有效地在术前评价星形细胞肿瘤的病理级别.

Comparison of perfusion-weighted MR imaging and pathology of intracranial astrocytomas

[Objective] To study the value of the perfusion MR in the preoperative assessment of histological grade of astrocytoma. [Methods] Thirty-two patients were confirmed with astrocytomas underwent MR plain scanning, perfusion MR and post contrast scanning respectively. Dynamic contrast enhancement T2*-weight gradient-echo echoplanar sequence was used to produce perfusion MR. The use of contrast agent volume was 0.2 mmol/kg and the flow rate of injection was 3～4 mL/sec. Firstly, the signal over time curves were described and the relative cerebral blood volume (rCBV) maps were produced. Then the maximum relative rCBV ratios were calculated as the following formula: maximum rCBV ratios= maximum rCBV of ipsilateral tumor/rCBV of contralateral white matter. Independence samples T-test was used to evaluate the difference of the maximum rCBV ratios between two groups. (P ＜0.05) was considered statistically significant. [Results] All cases were divided into two groups according to the histological grades. 18 cases were designed to low-grade astrocytomas (Ⅰ～Ⅱ) group and 14 to high grade astrocytomas (Ⅲ～Ⅳ)group. The maximum rCBV ratio was (2.57±0.78) (range 1.44～4.88) in low grade astrocytomas group, (5.40±0.63) (range 4.76～7.07) in high grade astrocytomas group. The differences in maximum rCBV ratio between two groups were statistically significant (P ＜0.01). [Conclusion] Perfusion MR is very useful in the preoperative assessment of astrocytomas of histological grades.