MRI distortion: considerations for MRI based radiotherapy treatment planning
MRI distortion: considerations for MRI based radiotherapy treatment planning
复制标题
DOI：
10.1007/s13246-014-0252-2
复制
发表时间：
2014-03-01
影响因子：
--
通讯作者：
Holloway, Lois
中科院分区：
文献类型：
--
作者：
Walker, Amy;Liney, Gary;Holloway, Lois
为了放射治疗计划（RTP）的目的，需要考虑磁共振图像中的失真。在四种不同的MRI扫描仪上使用多个序列扫描市售MRI网格体模，以评估几何失真的变化。然后确定整个视场中存在的失真。研究了不同带宽对图像失真和信噪比的影响。创建失真图，并将其与扫描仪孔内患者解剖结构的位置进行比较，以估计特定临床区域内失真的幅度和分布。MRI序列方案和扫描仪之间的失真幅度和模式各不相同。失真的幅度随着与2D成像平面内的扫描仪的等中心的距离的增加而增加。整个体模的平均失真通常保持在2.0 mm以下，尽管对于涡轮自旋回波序列，朝向体模边缘的失真增加到最大值4.1 mm。应用每个供应商提供的校正算法减少但没有完全消除失真。增加采集序列的带宽降低了失真量，但代价是在测量的带宽上信噪比降低了13.5。成像协议参数，包括带宽，切片厚度和相位编码方向，应注意RTP中的失真调查，因为每个都可以影响失真。不同临床部位的失真程度不同。
Distortion in magnetic resonance images needs to be taken into account for the purposes of radiotherapy treatment planning (RTP). A commercial MRI grid phantom was scanned on four different MRI scanners with multiple sequences to assess variations in the geometric distortion. The distortions present across the field of view were then determined. The effect of varying bandwidth on image distortion and signal to noise was also investigated. Distortion maps were created and these were compared to the location of patient anatomy within the scanner bore to estimate the magnitude and distribution of distortions located within specific clinical regions. Distortion magnitude and patterns varied between MRI sequence protocols and scanners. The magnitude of the distortions increased with increasing distance from the isocentre of the scanner within a 2D imaging plane. Average distortion across the phantom generally remained below 2.0 mm, although towards the edge of the phantom for a turbo spin echo sequence, the distortion increased to a maximum value of 4.1 mm. Application of correction algorithms supplied by each vendor reduced but did not completely remove distortions. Increasing the bandwidth of the acquisition sequence decreased the amount of distortion at the expense of a reduction in signal-to-noise ratio of 13.5 across measured bandwidths. Imaging protocol parameters including bandwidth, slice thickness and phase encoding direction, should be noted for distortion investigations in RTP since each can influence the distortion. The magnitude of distortion varies across different clinical sites.