Radiotherapy planning of the pelvis using distortion corrected MR images: the removal of system distortions
Radiotherapy planning of the pelvis using distortion corrected MR images: the removal of system distortions
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DOI：
10.1088/0031-9155/45/8/305
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发表时间：
2000-08-01
影响因子：
3.5
通讯作者：
Leach, MO
中科院分区：
文献类型：
--
作者：
Tanner, SF;Finnigan, DJ;Leach, MO
在使用磁共振（MR）图像进行放射治疗计划时，图像失真是一个重要的考虑因素。该失真是系统失真（由主磁场不均匀性和所施加磁场梯度的非线性引起）和由被成像对象/患者引起的效应的结果。已经开发了一个两阶段的协议，以纠正系统和对象引起的失真骨盆图像，其中包括措施，以保持成像和校正程序的质量，准确性和一致性。在此描述校正过程的第一阶段，该阶段涉及系统失真的去除。对象（患者）引起的影响将在随后的工作中描述。图像是在患者躺在平坦的刚性床上的情况下采集的，其再现了治疗条件。围绕患者并连接到床的标记管框架在每个图像中提供质量保证数据。使用单独的体模映射三个正交平面中的系统失真，该体模紧密配合在质量控制框架内。已编写软件，用于自动测量和检查测试对象生成的许多标记位置，并确保使用一致的成像协议采集患者数据。结果表明，在测量失真中使用的扫描仪和幻影给出了高度可重复的结果，在同一成像会话中标记位置的重复测量之间的平均变化为0.1 mm。证明了对系统畸变的面内分量的有效校正。
Image distortion is an important consideration in the use of magnetic resonance (MR) images for radiotherapy planning. The distortion is a consequence of system distortion (arising from main magnetic field inhomogeneity and nonlinearities in the applied magnetic field gradients) and of effects arising From the object/patient being imaged. A two-stage protocol has been developed to correct both system- and object-induced distortion in pelvic images which incorporates measures to maintain the quality, accuracy and consistency of the imaging and correction procedures. The first stage of the correction procedure is described here and involves the removal of system distortion. Object- (patient-) induced effects will be described in a subsequent work. Images are acquired with the patient lying on a fiat rigid bed, which reproduces treatment conditions. A frame of marker tubes surrounding the patient and attached to the bed provides quality assurance data in each image. System distortions in the three orthogonal planes are mapped using a separate phantom, which fits closely within the quality control frame. Software has been written which automates the measurement and checking of the many marker positions which the lest objects generate and which ensures that patient data are acquired using a consistent imaging protocol. Results are presented which show that the scanner and the phantoms used in measuring distortion give highly reproducible results with mean changes of the order of 0.1 mm between repeated measurements of marker positions in the same imaging session. Effective correction for in-plane components of system distortion is demonstrated.