Usefulness of hybrid deformable image registration algorithms in prostate radiation therapy

摘要

To evaluate the accuracy of commercially available hybrid deformable image registration (DIR) algorithms when using planning CT (pCT) and daily cone‐beam computed tomography (CBCT) in radiation therapy for prostate cancer. The hybrid DIR algorithms in RayStation and MIM Maestro were evaluated. Contours of the prostate, bladder, rectum, and seminal vesicles (SVs) were used as region‐of‐interest (ROIs) to guide image deformation in the hybrid DIR and to compare the DIR accuracy. To evaluate robustness of the hybrid DIR for prostate cancer patients with organs with volume that vary on a daily basis, such as the bladder and rectum, the DIR algorithms were performed on ten pairs of CT volumes from ten patients who underwent prostate intensity‐modulated radiation therapy or volumetric modulated arc therapy. In a visual evaluation, MIM caused unrealistic image deformation in soft tissues, organs, and pelvic bones. The mean dice similarity coefficient (DSC) ranged from 0.46 to 0.90 for the prostate, bladder, rectum, and SVs; the style="fixed-case">SVs had the lowest style="fixed-case">DSC. Target registration error ( style="fixed-case">TRE) at the centroid of the style="fixed-case">ROIs was about 2 mm for the prostate and bladder, and about 6 mm for the rectum and style="fixed-case">SVs. RayStation did not cause unrealistic image deformation, and could maintain the shape of pelvic bones in most cases. The mean style="fixed-case">DSC and style="fixed-case">TRE at the centroid of the style="fixed-case">ROIs were about 0.9 and within 5 mm generally. In both software programs, the use of style="fixed-case">ROIs to guide image deformation had the possibility to reduce any unrealistic image deformation and might be effective to keep the style="fixed-case">DIR physically reasonable. The style="fixed-case">pCT/ style="fixed-case">CBCT DIR for the prostate cancer did not reduce the style="fixed-case">DIR accuracy because of the use of style="fixed-case">ROIs to guide the image deformation.