The effect of respiratory motion on electronic portal imaging device dosimetry.

The effect of respiratory motion on electronic portal imaging device dosimetry. J Appl Clin Med Phys. 2019 Feb 05;: Authors: Fielding AL, Mendieta JB, Maxwell S, Jones C Abstract There is an increasing need to develop methods for in vivo verification of the delivery of radiotherapy treatments. Electronic portal imaging devices (EPID's) have been demonstrated to be of use for this application. The basic principle is relatively straightforward, the EPID is used to measure a two-dimensional (2D) planar exit or portal dose map behind the patient during the treatment delivery that can provide information on any errors in linear accelerator output or changes in the patient anatomy. In this paper we focused on the effect of intra-fraction motion, particularly respiratory motion, on the measured 2D EPID dose-response. Measurements were made with a breast phantom undergoing one-dimensional (1D) sinusoidal motion with a range of amplitudes (0.5, 1.0, and 1.5 cm) and frequencies (12, 15, and 20  cycles/min). Further measurements were made with the phantom undergoing breathing sequences measured during patient planning computed tomography simulation. We made use of the quadratic calibration method that converts the EPID images to a surrogate for dose, equivalent thickness of Plastic Water® . Comparisons were made of the 2D thickness maps derived for the different motions compared to the static phantom case and the resulting dose difference a...
Source: Journal of Applied Clinical Medical Physics - Category: Physics Authors: Tags: J Appl Clin Med Phys Source Type: research