恶性胶质瘤患者采用3D MPRAGE及常规序列MR成像与CT图像融合的效果比较

Comparison of the effect of 3D MPRAGE and conventional serial MR imaging and CT image fusion in patients with malignant glioma

目的MR与CT图像融合可提高恶性胶质瘤放疗靶区勾画的准确性,为减少误差采取何种MR成像方式和图像融合方法,尚无统一标准。本研究对不同序列MR成像利用颅脑内在特征与CT图像融合的效果比较,旨在探讨增强T1加权三维磁化强度预备梯度回波序列(contrast-enhanced T1weighted imaging-three dimensional magnetization prepared rapid acquisition gradient echo sequence,CE T1WI-3D MPRAGE)MR成像在恶性胶质瘤放疗中的应用价值。方法选取2017-09-01-2020-03-30经组织病理学确诊的恶性胶质瘤患者24例,其中,采用CE T1WI 3D MPRAGE序列MR扫描的患者12例为观察组,采用CE T1WI常规序列MR扫描的患者12例为对照组。将2组的MR图像与CT定位图像导入放疗计划系统,选取颅脑内在特征进行融合,记录x、y、z轴方向的平均差值;分别在MR/CT融合图像和CT图像上勾画脑干靶区,测量脑干中心坐标值,计算脑干靶区体积差值占比。比较2组患者图像融合时在x、y、z轴方向上的平均融合误差,以及脑干中心坐标、体积占比的平均差值。统计学分析主要采用2独立组均值差异的t检验及非参数的符号检验。结果观察组和对照组患者MR扫描的平均时间分别为(12.59±0.27)和(16.59±0.33)min,差异有统计学意义,t=-43.843,P<0.001。进行图像融合后,2组在x轴方向的平均融合误差分别为(0.02±0.04)和(0.60±0.26)mm,差异有统计学意义,t=-7.535,P<0.001;y轴方向的平均融合误差分别为(0.02±0.05)和(0.71±0.33)mm,差异有统计学意义,t=-6.600,P<0.001;z轴方向的平均融合误差分别为(0.22±0.21)和(0.77±0.37)mm,差异有统计学意义,t=-6.277,P<0.001。2组的脑干体积占比差值分别为(3.62±3.73)%和(10.21±7.91)%,差异有统计学意义,t=-2.922,P=0.014。2组的脑干靶区中心坐标值在x轴方向的平均融合误差分别为(0.19±0.03)和(0.44±0.37)mm,差异比较无统计学意义,t=-1.820,P=0.096。结论采用CE T1WI 3D MPRAGE序列MR成像,并利用颅脑内在特征与CT图像融合,流程简单,MR扫描时间缩短,图像融合的准确性和重复性较好,有利于恶性胶质瘤放疗靶区的确定。

OBJECTIVE MR and CT image fusion can improve the accuracy of target delineation for malignant glioma radiotherapy.There is no uniform standard for which MR imaging method and image fusion method should be adopted to reduce the error.This study compared the effect of fusion of different sequences of MR imaging with CT images using the intrinsic characteristics of the brain,and aimed to explore the application value of contrast-enhanced T1 weighted imaging three dimensional magnetization prepared rapid acquisition gradient echo sequence(CE T1 WI 3 D MPRAGE)MR imaging in the radiotherapy of malignant glioma.METHODS From 2017-09-01 to 2020-03-30,24 patients with malignant glioma diagnosed by histopathology were selected.Among them,12 patients with CE T1 WI 3 D MPRAGE sequence MR scan were used as the observation group,and CE T1 WI conventional sequence MR was used.Twelve patients scanned were the control group.The MR images and CT positioning images of the two groups were imported into the radiotherapy planning system,and the intrinsic characteristics of the brain were selected for fusion,and the average differences in the x-axis,y-axis,and z-axis directions were recorded;the brainstem target area was delineated on the MR/CT fusion image and CT image respectively,and the brainstem center coordinate value was measured to calculate the volume difference ratio of the brainstem target area.The average fusion error in the x-axis,y-axis,and z-axis directions of the image fusion between the two groups of patients,as well as the average difference between the central coordinate of the brain stem and the volume ratio were compared.RESULTS The average time of MR scan of the observation group and the control group were(12.59±0.27)min and(16.59±0.33)min,respectively,and the difference was statistically significant(t=-43.843,P<0.001).After image fusion,the average fusion error of the two groups in the x-axis direction were:(0.02±0.04)mm,(0.60±0.26)mm,and the difference was statistically significant(t=-7.535,P<0.001).The average fusion error in the y axis direction were:(0.02±0.05)mm,(0.71±0.33)mm,the difference was statistically significant(t=-6.600,P<0.001).The average fusion errors in the z-axis direction were:(0.22±0.21)mm and(0.77±0.37)mm,and the difference was statistically significant(t=-6.277,P<0.001).The difference in the proportion of brainstem volume between the two groups were(3.62±3.73)%and(10.21±7.91)%,respectively,and the difference was statistically significant(t=-2.222,P=0.014).The average fusion error of the central coordinate values of the brainstem target area in the x-axis direction of the two groups were(0.19±0.03)mm,(0.44±0.37)mm,and the difference was not statistically significant(t=-1.820,P=0.096).CONCLUSIONS Using CE T1 WI 3 D MPRAGE sequence MR imaging,and using the intrinsic characteristics of the brain to be fused with CT images,the process is simple,the MR scanning time is shortened,the accuracy and repeatability of image fusion is good,which is conducive to determining the target area of malignant glioma radiotherapy.