Performance of a deformable image registration algorithm for CT and cone beam CT using physical multi-density geometric and digital anatomic phantoms.

Purpose: To study the accuracy of deformable registration algorithm for CT and cone beam CT (CBCT) using a combination of physical and digital phantoms.

Materials And Methods: The physical phantoms consisted of objects over a range of electron densities, shape and sizes. The system was tested for simple and complex scenarios including performance in the presence of metallic artefacts.

Auto-segmentation of head and neck organs at risk in radiotherapy and its dependence on anatomic similarity.

Purpose: The aim is to study the dependence of deformable based auto-segmentation of head and neck organs-at-risks (OAR) on anatomy matching for a single atlas based system and generate an acceptable set of contours.

Methods: A sample of ten patients in neutral neck position and three atlas sets consisting of ten patients each in different head and neck positions were utilized to generate three scenarios representing poor, average and perfect anatomy matching respectively and auto-segmentation was carried out for each scenario. Brainstem, larynx, mandible, cervical oesophagus, oral cavity, pharyngeal muscles, parotids, spinal cord, and trachea were the structures selected for the study.

Application of aSi-kVCBCT for Volume Assessment and Dose Estimation: An Offline Adaptive Study for Prostate Radiotherapy.

Objective: The purpose of this study is to develop a method to estimate the dose using amorphous silicon detector panel cone beam computed tomography (aSi-kVCBCT) for the OARs and targets in prostate radiotherapy and to compare with the actual planned dose. Methods: The aSi-kVCBCT is used widely in radiotherapy to verify the patient position before treatment. The advancement in aSi-kVCBCT combined with adaptive software allows us to verify the dose distribution in daily acquired CBCT images.

Feasibility of MR-only radiation planning for hypofractionated stereotactic radiotherapy of schwannomas using non-coplanar volumetric modulated arc therapy.

Purpose: To compare the dose calculation accuracy of plans done on a CT density-assigned MR image set for hypofractionated stereotactic radiotherapy (HSRT) using volumetric modulated radiation therapy containing non-coplanar beams.

Methods: Eighteen patients diagnosed with schwannoma treated with HSRT were selected retrospectively. These patients underwent planning CT (pCT) for radiation therapy (RT) and contrast-enhanced three-dimensional fast-spoiled gradient-echo image (3D FSPGR) to assist tumor delineation.

Magnetic resonance image guidance in external beam radiation therapy planning and delivery.

The use of magnetic resonance (MR) imaging in radiation oncology is improving dramatically. This review article discusses the necessity of image guidance and how MR finds a significant place in radiotherapy planning and delivery. The challenges to and current solutions for an in-house MR simulation, dedicated MR simulator, estimation of electron density using MR image sets and development of MR-compatible treatment planning systems are presented.

Feasibility of offline head & neck adaptive radiotherapy using deformed planning CT electron density mapping on weekly cone beam computed tomography.

Objective: The purpose of the study was to use deformable mapping of planning CT (pCT) electron density values on weekly cone-beam CT (CBCT) to quantify the anatomical changes and determine the dose-volume relationship in offline adaptive volumetric-modulated arc therapy.

Methods: 10 patients treated with RapidArc plans who had weekly CBCTs were selected retrospectively. The pCT was deformed to weekly CBCTs and the deformed contours were checked for any discrepancies.