LaTIM, INSERM, UMR 1101, CHRU Morvan, Brest, France.
Institut de Recherche Technologique b<>com, Cesson-Sévigné, France.
Med Phys. 2017 Dec;44(12):6447-6455. doi: 10.1002/mp.12629. Epub 2017 Nov 6.
In prostate radiotherapy, dose distribution may be calculated on CT images, while the MRI can be used to enhance soft tissue visualization. Therefore, a registration between MR and CT images could improve the overall treatment planning process, by improving visualization with a demonstrated interobserver delineation variability when segmenting the prostate, which in turn can lead to a more precise planning. This registration must compensate for prostate deformations caused by changes in size and form between the acquisitions of both modalities.
We present a fully automatic MRI/CT nonrigid registration method for prostate radiotherapy treatment planning. The proposed registration methodology is a two-step registration process involving both a rigid and a nonrigid registration step. The registration is constrained to volumes of interest in order to improve robustness and computational efficiency. The method is based on the maximization of the mutual information in combination with a deformation field parameterized by cubic B-Splines.
The proposed method was validated on eight clinical patient datasets. Quantitative evaluation, using Hausdorff distance between prostate volumes in both images, indicated that the overall registration errors is 1.6 ± 0.2 mm, with a maximum error of less than 2.3 mm, for all patient datasets considered in this study.
The proposed approach provides a promising solution for an effective and accurate prostate radiotherapy treatment planning since it satisfies the desired clinical accuracy.
在前列腺放射治疗中，剂量分布可以在 CT 图像上计算，而 MRI 可用于增强软组织可视化。因此，MR 和 CT 图像之间的配准可以通过提高对前列腺的分割的可视化效果来改善整体治疗计划过程，同时当对前列腺进行分割时，该方法已经证明了观察者间的可变性，这反过来又可以实现更精确的规划。这种配准必须补偿两种模态采集之间前列腺尺寸和形状变化引起的变形。
我们提出了一种用于前列腺放射治疗计划的全自动 MRI/CT 非刚性配准方法。所提出的配准方法学是一个两步配准过程，涉及刚性和非刚性配准步骤。为了提高鲁棒性和计算效率，注册受到感兴趣区域的约束。该方法基于互信息最大化，结合由三次 B 样条参数化的变形场。
该方法在 8 个临床患者数据集上进行了验证。使用两幅图像中前列腺体积之间的 Hausdorff 距离进行定量评估表明，对于本研究中考虑的所有患者数据集，整体注册误差为 1.6±0.2mm，最大误差小于 2.3mm。
该方法为有效的和准确的前列腺放射治疗计划提供了有前途的解决方案，因为它满足了所需的临床精度。
