Deformable image registration for dose mapping between external beam radiotherapy and brachytherapy images of cervical cancer.
This study proposed and evaluated different deformable image registration (DIR) methods for this application. Twenty patients who underwent EBRT and BT for LACC were retrospectively analyzed. Each patient had a pre-BT CT at EBRT boost (without applicator) and a CT and MRI at BT (with applicator). The evaluated DIR methods were the diffeomorphic Demons, commercial intensity and hybrid methods, and three different biomechanical models. The biomechanical models considered different boundary conditions. The impact of the BT devices insertion on the anatomy was quantified. DIR method performances were quantified using geometric criteria between the original and deformed contours. The BT dose was deformed toward the pre-CT BT by each DIR method. The impact of boundary condition to drive the biomechanical model was evaluated based on the deformation vector field and dose differences. The GEC-ESTRO guideline dose indices were reported. Large organ displacements, deformations, and volume variations were observed between the pre-BT and BT anatomies. Rigid registration and intensity-based DIR resulted in poor geometric accuracy with mean Dice similarity coefficient (DSC) inferior to 0.57, 0.63, 0.42, 0.32, 0.43 for the rectum, bladder, vagina, cervix and uterus, respectively. Biomechanical models provided mean DSC of 0.96 for all the organs. By considering the cervix-uterus as one single structure, biomechanical models provided mean DSC of 0.88 and 0.94 for the cervix...
Source: Physics in Medicine and Biology - Category: Physics Authors: Rigaud B, Klopp A, Vedam S, Venkatesan A, Taku N, Simon A, Haigron P, de Crevoisier R, Brock KK, Cazoulat G Tags: Phys Med Biol Source Type: research
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