MRI用于立体定向放射治疗定位的精确性分析

Accuracy of magnetic resonance imaging in the localization of stereotactic radiotherapy

目的:研究MRI用于立体定向放射治疗(SRT)定位时误差的大小,明确MRI能否单独用于SRT定位。方法:模拟对病人的扫描方法,对特制体模进行固定和MRI扫描。在治疗计划系统上,测量x、y、z 3个方向靶点距离,并将结果与实际距离做比较,差别的绝对值即为该定位系统的误差。结果:相邻点x方向,误差0.2￣1.4 mm,平均0.9 mm;y方向误差0.3￣1.5 mm,平均0.9 mm。相对点x方向,误差0.3￣1.7 mm,平均0.9 mm;y方向,误差0.4￣1.8 mm,平均0.9 mm。各标记层面之间误差无显著性差别(P>0.05)。z方向误差0.3￣1.9 mm,平均1.0 mm。结论:本研究采用的立体定向定位系统和MRI扫描方法,用MRI进行影像采集制定SRT计划,对多数颅内和头颈部肿瘤的定位精度符合临床要求,但在将MRI进行SRT定位扫描时,必须作全面的检查和验证。

Objective： To measure the errors of magnetic resonance imaging （ MRI ） in the localization of stereotactic radiotherapy （ SRT ）, and to confirm whether MRI can be used in the localization alone. Methods： A specially made phantom was used to acquire MRI images. In the treatment planning system, the distances between targets in x, y, and z directions were measured and compared with true values. The absolute values of the differences between the measured and true values were considered as the errors of the localization system. Results： The errors of adjacent points were in the range of 0.2 to 1.4 mm and 0.3 to 1.5 mm in x and y directions, respectively, and the average was 0.9 mm in beth x and y directions. The errors of opposite points were in the range of 0.3 to 1.7 mm and 0.4 to 1.8 mm in x and y directions, respectively, and the average was 0.9mm in beth x and y directions. There was no significant difference among 6 marked planes in beth x and y directions （P〉 0.05）. Errors in z direction were in the range of 0.3 to 1.9 mm, and the average was 1.0 mm. Conclusion： MRI can be used alone in the localiz,ation of most brain tumors and head and neck tumors, but it is necessary to perform a comprehensive check when MRI is used in SRT localization.