STructural Rectal Atlas Deformation (StRAD) Features for Characterizing Intra- and Peri-wall Chemoradiation Response on MRI

摘要

Radiomic features which quantify morphologic texture and shape of tumor regions on imaging have found wide success in characterizing treatment response in vivo. A more detailed interrogation of intra-and peri-tumoral regions for response-related cues could be achieved by capturing subtle structural deformations that occur due to tumor shrinkage or growth. In this work, we present a novel suite of STructural Rectal Atlas Deformation (StRAD) features to quantify tumor-related deformations in rectal cancers via a cohort of 139 patient MRIs. In flexible non-rigid organs such as the rectum, inter-patient differences complicate evaluation of tumor-related deformations that may occur within the rectal wall or in the peri-rectal environment; necessitating construction of a canonical rectal imaging atlas. Using 63 pelvic MRIs where healthy rectums could be clearly visualized, we built the first structural atlas for the healthy rectal wall. This atlas was used to compute structural deformations within and around locations in the rectal wall of patients where tumor was present, resulting in intra- and peri-wall StRAD descriptors. We evaluated the efficacy of our StRAD features in 2 different tasks: (a) predicting which rectal tumors will or will not respond to therapy via baseline MRIs (n = 42), and (b) identifying which rectal tumors were exhibiting regression on post-chemoradiation MRIs (n = 34). Using a linear discriminant analysis classifier in a three-fold cross-validation scheme, we found that intra-wall deformations were significantly lower for responders to chemoradiation; both on baseline MRIs (AUC = 0.73±0.05) as well as on post-therapy MRIs (AUC = 0.87±0.03). By comparison, radiomic texture features for both intra- and peri-wall locations yielded significantly worse classification performance in both tasks.