Date/Time
Date(s) - 05/03/2025
10:30 am - 11:30 am

Location
Physics and Astronomy Department

ABB 102

Dr. Patricia Oliver

Assistant Professor
Dalhousie University
Profile link: https://medicine.dal.ca/departments/department-sites/radiation-oncology/our-people/our-faculty/PatriciaOliver.html

Title: Transit dosimetry for online adaptive radiotherapy

Abstract:

This study investigates the use of transit dosimetry as a means of quality assurance testing in Online Adaptive Radiation Therapy (OART). With OART, a new treatment plan is created every day. As such, there is no convenient option for pre-treatment, measurement-based, patient-specific quality assurance testing for OART.

The linear accelerator used for OART possesses a flat panel detector situated perpendicular to the beamline. This panel measures the 2D radiation intensity pattern exiting through the patient during treatment delivery. This technique is known as transit dosimetry. Monte Carlo simulations are used to generate corresponding prediction images based on the treatment plan of the day and the patient computed tomography (CT) dataset acquired at the beginning of the appointment. Differences between the predicted and measured transit dosimetry images can be indicative of treatment delivery errors.

A prostate cancer radiation therapy test case is considered. A common problem with this type of treatment is the appearance of bowel gas adjacent to the prostate, which can cause significant dosimetric perturbations. Three scenarios are considered using an anthropomorphic computational phantom: no bowel gas, small amount of bowel gas, and large amount of bowel gas. Correlations between 2D transit dosimetry images and 3D patient dose distributions are explored, with the goal of better quantifying action levels for transit dosimetry.