The effects of computed tomography image characteristics and knot spacing on the spatial accuracy of B-spline deformable image registration in the head and neck geometry.

Objectives: To explore the effects of computed tomography (CT) image characteristics and B-spline knot spacing (BKS) on the spatial accuracy of a B-spline deformable image registration (DIR) in the head-and-neck geometry.

Methods: The effect of image feature content, image contrast, noise, and BKS on the spatial accuracy of a B-spline DIR was studied. Phantom images were created with varying feature content and varying contrast-to-noise ratio (CNR), and deformed using a known smooth B-spline deformation.

3D Variation in delineation of head and neck organs at risk.

Background: Consistent delineation of patient anatomy becomes increasingly important with the growing use of highly conformal and adaptive radiotherapy techniques. This study investigates the magnitude and 3D localization of interobserver variability of organs at risk (OARs) in the head and neck area with application of delineation guidelines, to establish measures to reduce current redundant variability in delineation practice.

Methods: Interobserver variability among five experienced radiation oncologists was studied in a set of 12 head and neck patient CT scans for the spinal cord, parotid and submandibular glands, thyroid cartilage, and glottic larynx.

Bath and shower effects in the rat parotid gland explain increased relative risk of parotid gland dysfunction after intensity-modulated radiotherapy.

Purpose: To assess in a rat model whether adding a subtolerance dose in a region adjacent to a high-dose irradiated subvolume of the parotid gland influences its response (bath-and-shower effect).

Methods And Materials: Irradiation of the whole, cranial 50%, and/or the caudal 50% of the parotid glands of Wistar rats was performed using 150-MeV protons. To determine suitable (i.

Grading-system-dependent volume effects for late radiation-induced rectal toxicity after curative radiotherapy for prostate cancer.

Purpose: To assess the association between the dose distributions in the rectum and late Radiation Therapy Oncology Group and the European Organisation for Research and Treatment of Cancer (RTOG/EORTC), Late Effects of Normal Tissue SOMA, and Common Terminology Criteria for Adverse Events (CTCAE) version 3.0 graded rectal toxicity among patients with prostate cancer treated with RT.

Methods And Materials: Included in the study were 124 patients who received three-dimensional conformal RT for prostate cancer to a total dose of 70 Gy in 2-Gy fractions.

The impact of heart irradiation on dose-volume effects in the rat lung.

Purpose: To test the hypothesis that heart irradiation increases the risk of a symptomatic radiation-induced loss of lung function (SRILF) and that this can be well-described as a modulation of the functional reserve of the lung.

Methods And Materials: Rats were irradiated with 150-MeV protons. Dose-response curves were obtained for a significant increase in breathing frequency after irradiation of 100%, 75%, 50%, or 25% of the total lung volume, either including or excluding the heart from the irradiation field.