title: An automated deformable image registration evaluation of confidence tool.
abstract: Deformable image registration (DIR) is a powerful tool for radiation oncology, but it can produce errors. Beyond this, DIR accuracy is not a fixed quantity and varies on a case-by-case basis. The purpose of this study is to explore the possibility of an automated program to create a patient- and voxel-specific evaluation of DIR accuracy. AUTODIRECT is a software tool that was developed to perform this evaluation for the application of a clinical DIR algorithm to a set of patient images. In brief, AUTODIRECT uses algorithms to generate deformations and applies them to these images (along with processing) to generate sets of test images, with known deformations that are similar to the actual ones and with realistic noise properties. The clinical DIR algorithm is applied to these test image sets (currently 4). From these tests, AUTODIRECT generates spatial and dose uncertainty estimates for each image voxel based on a Student's t distribution. In this study, four commercially available DIR algorithms were used to deform a dose distribution associated with a virtual pelvic phantom image set, and AUTODIRECT was used to generate dose uncertainty estimates for each deformation. The virtual phantom image set has a known ground-truth deformation, so the true dose-warping errors of the DIR algorithms were also known. AUTODIRECT predicted error patterns that closely matched the actual error spatial distribution. On average AUTODIRECT overestimated the magnitude of the dose errors, but tuning the AUTODIRECT algorithms should improve agreement. This proof-of-principle test demonstrates the potential for the AUTODIRECT algorithm as an empirical method to predict DIR errors.
authors.affiliation: Department of Radiation Oncology, University of California San Francisco, CA, USA. Department of Radiation Oncology, University of Texas Health Science Center San Antonio, TX, USA.
authors.forename: Neil
authors.initials: N
authors.lastname: Kirby
authors.forename: Josephine
authors.initials: J
authors.lastname: Chen
authors.forename: Hojin
authors.initials: H
authors.lastname: Kim
authors.forename: Olivier
authors.initials: O
authors.lastname: Morin
authors.forename: Ke
authors.initials: K
authors.lastname: Nie
authors.forename: Jean
authors.initials: J
authors.lastname: Pouliot
mesh_terms: D000465:Algorithms; D006801:Humans; D007091:Image Processing, Computer-Assisted; D010363:Pattern Recognition, Automated; D010388:Pelvis / Q000033:anatomy & histology*; D019047:Phantoms, Imaging; D012984:Software; D035501:Uncertainty