Large deformation three-dimensional image registration in image-guided radiation therapy

Abstract

In this paper, we present and validate a framework, based on deformable image registration, for automatic processing of serial three-dimensional CT images used in image-guided radiation therapy. A major assumption in deformable image registration has been that, if two images are being registered, every point of one image corresponds appropriately to some point in the other. For intra-treatment images of the prostate, however, this assumption is violated by the variable presence of bowel gas. The framework presented here explicitly extends previous deformable image registration algorithms to accommodate such regions in the image for which no correspondence exists. We show how to use our registration technique as a tool for organ segmentation, and present a statistical analysis of this segmentation method, validating it by comparison with multiple human raters. We also show how the deformable registration technique can be used to determine the dosimetric effect of a given plan in the presence of non-rigid tissue motion. In addition to dose accumulation, we describe a method for estimating the biological effects of tissue motion using a linear-quadratic model. This work is described in the context of a prostate treatment protocol, but it is of general applicability.

Improved prostate delineation in prostate HDR brachytherapy with TRUS‐CT deformable registration technology: A pilot study with MRI validation

“…Many CT prostate segmentation technologies have been investigated in recent years, such as the models‐based,23, 24, 25 classification‐based26, 27, 28 and registration‐based29, 30 methods. Most of these segmentation approaches are based on the appearance and texture of the prostate gland on CT images.…”

A Novel Intensity Similarity Metric with Soft Spatial Constraint for a Deformable Image Registration Problem in Radiation Therapy

“…The patient undergoes a fractionated treatment process, where the incremental amount of dose is applied over several days. The original planned dose based on the planning CT is usually not valid throughout the whole treatment process, specifically for deformable targets such as prostate and organs at risk such as bladder and rectum with filling variations [6]. One solution is to acquire CT images prior to treatment in order to better capture the recent state of the anatomy.…”

“…al. [6], where a two step registration is proposed to deal with the presence of gas in the rectum. We believe that a good approach for solving this problem should be based on a unified variational formulation that can recover the dense deformation field and also deal with these special regions.…”

Assessment of a commercially available automatic deformable registration system

“…It has been applied to problems such as autosegmentation, ( 1 , 2 ) four‐dimensional (4D) treatment optimization, ( 3 , 4 , 5 , 6 , 7 ) dose accumulation ( 1 , 8 ) and tumor growth/regression analysis. ( 9 ) Varied objectives in these and other potential applications, compounded by the fact that often the lack of a gold standard makes true assessment impossible, ( 10 ) make validation of deformable image registration algorithms very difficult.…”

“…Various measures of volume overlap evaluated using radiation oncologist delineated prostate contours have been used for validation of deformable registration of ${\mathrm{normalT}}_2$‐weighted pelvic images with and without inflated endorectal coils. ( 29 , 30 , 31 ) Volumetric‐based methods have also been used when validating deformable registration of pelvic CT ( 1 , 2 ) and head and neck CT ( 16 ) images.…”