Technical Note: Characterization and correction of gradient nonlinearity induced distortion on a 1.0 T open bore MR-SIM
Technical Note: Characterization and correction of gradient nonlinearity induced distortion on a 1.0 T open bore MR-SIM
复制标题
DOI：
10.1118/1.4930245
复制
发表时间：
2015-10-01
期刊：
影响因子：
3.8
通讯作者：
Glide-Hurst, Carri K.
中科院分区：
文献类型：
--
作者：
Price, Ryan G.;Kadbi, Mo;Glide-Hurst, Carri K.
目的：磁共振成像（MRI）中的失真损害空间保真度，可能影响描绘和剂量计算。我们在1.0 T高场开放式MR模拟器（MR-SIM）中表征了2D和3D大视场（FOY）、不同位置的序列无关失真，以实现MRI治疗计划的校正图。36 x 43 x 2 cm（3）体模，具有255个已知标志使用1.0 T高场开放式MR-SIM在横轴、矢状轴和冠状轴等中心扫描（类似于1 mm（3）），通过在上下方向的三个重叠位置步进扫描465 x 350 x 168 mm（3）3D体模，以获得总465 x 350 x 400 mm（3）采样FOV，产生>13 800个标志（3D多普勒-回波，TE/TR/alpha = 5.54 ms/30 ms/28，体素尺寸= 1 x 1 x 2 mm（3））根据体模示意图生成二元模板（参考）。自动程序通过掩蔽、阈值处理和连通性测试将MR图像转换为二进制，以识别标志。通过质心映射生成失真图。图像通过扭曲与逆失真映射进行校正，时间稳定性assessed.Results：在采样FOV，不可忽略的残余梯度失真存在接近9.5 cm的等角点，与7.4 mm的最大失真接近23 cm的等角点。在6个月内，横向平面的x和y方向的平均梯度失真分别为-0.07 +/- 1.10 mm和0.10 +/- 1.10 mm，矢状面为0.03 +/- 0.64和0.09 +/- 0.70 mm，冠状面为0.4 +/- 1.16和0.04 +/- 0.40 mm。在实施3D校正图后，失真减少到
Purpose: Distortions in magnetic resonance imaging (MRI) compromise spatial fidelity, potentially impacting delineation and dose calculation. We characterized 2D and 3D large field of view (FOY), sequence-independent distortion at various positions in a 1.0 T high-field open MR simulator (MR-SIM) to implement correction maps for MRI treatment planning.Methods: A 36 x 43 x 2 cm(3) phantom with 255 known landmarks (similar to 1 mm(3)) was scanned using 1.0 T high-field open MR-SIM at isocenter in the transverse, sagittal, and coronal axes, and a 465 x 350 x 168 mm(3) 3D phantom was scanned by stepping in the superior-inferior direction in three overlapping positions to achieve a total 465 x 350 x 400 mm(3) sampled FOV yielding >13 800 landmarks (3D Gradient-Echo, TE/TR/alpha = 5.54 ms/30 ms/28, voxel size = 1 x 1 x 2 mm(3)) A binary template (reference) was generated from a phantom schematic. An automated program converted MR images to binary via masking, thresholding, and testing for connectivity to identify landmarks. Distortion maps were generated by centroid mapping. Images were corrected via warping with inverse distortion maps, and temporal stability was assessed.Results: Over the sampled FOV, non-negligible residual gradient distortions existed as close as 9.5 cm from isocenter, with a maximum distortion of 7.4 mm as close as 23 cm from isocenter. Over six months, average gradient distortions were -0.07 +/- 1.10 mm and 0.10 +/- 1.10 mm in the x and y directions for the transverse plane, 0.03 +/- 0.64 and 0.09 +/- 0.70 mm in the sagittal plane, and 0.4 +/- 1.16 and 0.04 +/- 0.40 mm in the coronal plane. After implementing 3D correction maps, distortions were reduced to