磁共振图像(MRI)空间几何失真对立体放射治疗中靶点位置精确度影响的分析

The analysis of spatial distortion in magnetic resonance imaging influence on precision and accuracy of target position in stereotactic radiotherapy

目的：分析模拟靶点MRI空间几何失真的因素，以及其对立体放射治疗中靶点位置精确度的影响程度。材料和方法：将5×5矩阵小孔有机玻璃靶点模拟装置和Leksell-G型立体定位头架进行磁共振扫描，分别测量MRI二维横断面和不同扫描层厚情况下选取层面在纵向的几何失真程度。结果：MRI二维横断面上模拟把点X、Y方向精确度分别为（0．03±0．12）mm、（0.44±0．31）mm，平面距离精确度为（0．46±0．31）mm，选取层面在纵向（Z方向）的精确度为（0．46±0．41）mm。结论：梯度场非线性和主磁场的非均匀性以及不同扫描展尽是MRI几何失真的因素。磁共振作为立体放射治疗靶点定位是可行的。

Purpose: analyzing factors of the imitating target spatial distortion in magnetic resonance imaging(MRI),and effects of the spatial distortion on precision &. accuracy of target position in stereotactic radiotherapy.Materials and Methods: The plexiglass target position simulator and the stereotactic skull scaling instrument(Leksell-G) was scanned with magnetic resonance, the spatial distortion of the MRI cross section and the spatialdistortion of the selected scanners with different thickness in Z direction was measured. Results: The precisionand accuracy of distance in MRI cross section was (0. 46 ±0. 31 )mm , and the cotribution was (0. 03 ±0. 12 )mm inX direction, (0. 44 ±0. 31 )mm in Y direcion, The precision and accuracy of setected scanner was (0. 46 ±0. 41 )mmin Z direction. Conclusion: The spatial distortion in MRI stems from the gradient field nonlinearities and magneticfield inhomogeneities and different thickness. To locate target with MRI is practicable for stereotacitic radiothera-Py.