CT to Cone-beam CT Deformable Registration With Simultaneous Intensity Correction

TL;DR

This paper introduces DISC, a novel deformable registration algorithm that adaptively corrects intensity inconsistencies between CT and CBCT images, significantly improving registration accuracy in adaptive radiation therapy.

Contribution

The paper proposes DISC, a deformable registration method with simultaneous intensity correction, addressing intensity mismatch issues in CT-CBCT registration.

Findings

DISC outperforms original demons in accuracy

Robust against CBCT artifacts and intensity inconsistencies

Improves registration in clinical head-and-neck cases

Abstract

Computed tomography (CT) to cone-beam computed tomography (CBCT) deformable image registration (DIR) is a crucial step in adaptive radiation therapy. Current intensity-based registration algorithms, such as demons, may fail in the context of CT-CBCT DIR because of inconsistent intensities between the two modalities. In this paper, we propose a variant of demons, called Deformation with Intensity Simultaneously Corrected (DISC), to deal with CT-CBCT DIR. DISC distinguishes itself from the original demons algorithm by performing an adaptive intensity correction step on the CBCT image at every iteration step of the demons registration. Specifically, the intensity correction of a voxel in CBCT is achieved by matching the first and the second moments of the voxel intensities inside a patch around the voxel with those on the CT image. It is expected that such a strategy can remove artifacts in the CBCT image, as well as ensuring the intensity consistency between the two modalities. DISC is implemented on computer graphics processing units (GPUs) in compute unified device architecture (CUDA) programming environment. The performance of DISC is evaluated on a simulated patient case and six clinical head-and-neck cancer patient data. It is found that DISC is robust against the CBCT artifacts and intensity inconsistency and significantly improves the registration accuracy when compared with the original demons.