Constrained non-rigid registration for use in image-guided adaptive radiotherapy

Abstract

A constrained non-rigid registration (CNRR) algorithm for use in prostate image-guided adaptive radiotherapy is presented in a coherent mathematical framework. The registration algorithm is based on a global rigid transformation combined with a series of local injective non-rigid multi-resolution cubic B-spline Free Form Deformation (FFD) transformations. The control points of the FFD are used to non-rigidly constrain the transformation to the prostate, rectum, and bladder. As well, the control points are used to rigidly constrain the transformation to the estimated position of the pelvis, left femur, and right femur. The algorithm was tested with both 3D conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT) dose plan data sets. The 3DCRT dose plan set consisted of 10 fan-beam CT (FBCT) treatment-day images acquired from four different patients. The IMRT dose plan set consisted of 32 cone-beam CT (CBCT) treatment-day images acquired from 4 different patients. The CNRR was tested with different combinations of anatomical constraints and each test significantly outperformed both rigid and non-rigid registration at aligning constrained bones and critical organs. The CNRR results were used to adapt the dose plans to account for patient positioning errors as well as inter-day bone motion and intrinsic organ deformation. Each adapted dose plan improved performance by lowering radiation distribution to the rectum and bladder while increasing or maintaining radiation distribution to the prostate.

A domain constrained deformable (DoCD) model for co-registration of pre- and post-radiated prostate MRI

“…Firstly, the prostate and internal structures were manually segmented, as in [16, 33, 34]. Future work will employ an automatic segmentation scheme such as [36] to automatically segment the CG and PZ.…”

“…As in [33, 34], in this work manual segmentations of the prostatic structures were used to drive the registration. The prostate and CG were manually delineated on each image (the PZ is simply the subtraction of the two) by an expert radiation oncologist using the Slicer software [35].…”

“…In addition, a rigid registration (translation plus rotation) was used as a comparative strategy in [34] for a deformable registration of pre-EBRT MRI and CT. Rigid was therefore used as a comparative strategy in this study.…”

Computer Simulation and Analysis of Three-Dimensional Tumor Geometry in Radiotherapy

“…Image-guided radiation therapy (IGRT) uses advanced imaging technology such as on-board imaging system to achieve precise and accurate dose delivery. Many studies have reported inter-fractional organ motions and efficacy of IGRT in reducing targeting errors using daily CT images (Den et al 2009, Wang et al 2009, Houghton et al 2009, Pawlowski et al 2010, Varadhan et al 2009, Greene et al 2009). Owing to these techniques, errors in patient set-up and dose delivery can be reduced to some extent.…”

A Unified Framework for Joint Segmentation, Nonrigid Registration and Tumor Detection: Application to MR-Guided Radiotherapy

“…The goal in radiotherapy cancer treatment is to deliver as much dose as possible to the clinical target volume (CTV), while trying to deliver as little dose as possible to surrounding organs at risk[4,10]. When higher doses are to be delivered, precise and accurate targeting is essential because of unpredictable inter- and intra-fractional organ motions over the process of the weekly treatments, which require accurate nonrigid mapping between treatment and planning day.…”