脑膜瘤相对血流量MR定量检测:梯度回波与平面回波序列法的比较

MR quantitative measurement of relative blood volume in patients with meningioma:comparison of gradient echo and echo planar imaging sequences

目的通过对梯度回波序列法与平面回波(echoplanerimaging,EPI)序列法重建脑膜瘤相对血流量图的比较,对脑膜瘤相对血流量的定量检测进行评价。方法应用西门子1.5TMR仪对18例脑膜瘤病人进行检查,获取常规的T1WI、T2WI和增强T1WI,以及动态的磁顺应敏感图像(T2WI梯度回波序列或SEEPI序列)。在采集动态的磁顺应敏感图像期间(梯度回波法12例,EPI法6例),应用程控注射器以每秒5ml的流率注入钆喷替酸葡甲胺(GdDTPA)(0.2mmol/kg)。应用优视系统(advancedvisualsystem,AVS)软件逐点处理动态的磁顺应敏感资料,对重建的全部相对血流量图作感兴趣区分析,通过借鉴文献中脑灰质血流量数值,定量计算脑膜瘤的相对血流量。结果肿瘤相对血流量与脑灰质相对血流量的比率是3.01±1.18(梯度回波序列法为3.07±1.39;EPI序列法为2.84±0.94)。脑膜瘤的平均相对血流量为(14.47±5.96)ml/100g:梯度回波序列法为(14.85±6.72)ml/100g,EPI序列法为(13.72±4.54)ml/100g;梯度回波序列法与EPI序列法的结果比较差异无统计学意义(t=0.42,P=0.68)。结论应用脑灰质血流量数值法可便捷地定量检测脑膜瘤的相对血流量,脑膜瘤的相对血流量明显增高而且非均匀性;血脑屏障破坏情况下,仍可估算相对血流量值;尽管EPI序列法更具有效应,梯度回波序列法和EPI序列法均能有效地应用于相对血流量的测定。

Objective To quantitatively measure the relative blood volume (rBV) in meningioma, and to compare the utility of reconstruction using both gradient-echo sequence and echo-planar imaging (EPI) sequence. Methods Eighteen patients with meningioma were studied on a Siemens 1.5-T scanner. During the gradient-echo sequence (n=12) and EPI sequence (n=6), a bolus (0.2 mmol/kg) of Gd-DTPA was injected mechanically with a flow rate of 5 ml/second. Image processing of dynamic data was performed on a pixel-by-pixel basis using Advanced Visual Systems (AVS) program. Based on gray matter blood volume in the literature, absolute values of relative blood volume of meningioma were calculated. Results The mean ratio of tumor rBV/gray matter rBV was 3.01±1.18 (3.07±1.39 in gradient echo sequence and 2.84±0.94 in EPI sequence). According to the ratio of tumor rBV/gray matter rBV, a mean value, 14.47±5.96 ml/100 g (14.85±6.72 ml/100 g in gradient echo sequence and 13.72±4.54 ml/100 g in EPI sequence), of rBV in meningiomas was calculated. These differences were not statistically significant (t=0.42, P=0.68). Conclusion Compared with the gray matter, absolute rBV value of meningioma can be obtained, and increased inhomogeneous rBV was observed in meningioma. Estimation of rBV is feasible although there is a breakdown of the blood-brain barrier in meningioma. Based on the two different sequences, no bias can be observed in our rBV reconstruction.