Development and Evaluation of Multipurpose Phantom for Delivery Quality Assurance of Intensity-modulated Radiation Therapy

Abstract

Treatments demanding high accuracy, such as intensity-modulated radiation therapy (IMRT), should provide the optimal dose distribution and correct intervention. Otherwise, they may become unsafe and cause adverse effects to patients. Delivery quality assurance (DQA) for treatment verification can be performed considering the absolute dose using an ionization chamber and relative dose using a film. However, a film imposes a long waiting time for measurement and is sensitive to temperature and humidity, development conditions, and noise. We aim to evaluate the usefulness of a multipurpose phantom for fast and simple IMRT DQA. The multipurpose phantom is made of poly (methyl methacrylate)-based resin. The phantom allows the insertion of a 2D array detector and an ionization chamber. Therefore, the relative and absolute doses can be measured simultaneously. The IMRT DQA evaluation provided absolute dose of 0.35 ± 1.74% and relative dose of 99.03 ± 0.6 % in 3 mm/3% gamma evaluation for a linear accelerator. In addition, the absolute and relative doses were 1.37 ± 1.05% and 98.7 ± 0.78% in helical tomotherapy, respectively. Therefore, the dose measurements were within acceptable error limits of 3%. The results demonstrate the multipurpose capabilities of the proposed phantom for evaluating dose distribution and absolute dosimetry.