8. Validation of a “Demons” intensity-based deformable image registration algorithm using numerical phantoms and CT-patients

Abstract

Introduction Adaptive Radiotherapy (ART) is a technique which minimizes the dosimetric impact of anatomical changes that may occur during treatment. One of the milestones of ART is deformable image registration (DIR) between original planning images and images acquired during treatment. The aim of this study is to propose a method to evaluate the performances and validate the clinical use of a “Demons” intensity-based DIR algorithm implemented in SmartAdapt® v.13.5 (Varian Medical Systems, USA). Methods Two types of dataset were used to perform the evaluation: numerical phantoms and CT-CBCT images of 5 patients with head and neck (HN max = 0.92) and 0.73 (min = 0.65; max = 0.9) for registrations CTD0-CTre-CT and CTD0-CBCTD16 respectively. The dispersion of the values is mainly due to organs shape and algorithm choice. No significant variation is obtained between DIR for single-modality (CT–CT) and multi-modality (CT–CBCT). Moreover, contours propagation reduces significantly physicians required time for contouring patient images. Conclusions Given the results obtained with numerical phantoms and CT-patients, a clinical use appears possible. SmartAdapt® enables significant time-saving compared to manual re-contouring for re-planning strategies. However, a careful review by a specialist for DIR-generated contours is essential for clinical cases.