Purpose: Radio-dynamic therapy (RDT) uses a combination of high-energy photon beams and photo/radio-sensitizers to kill cancer cells. RDT treatment plans were generated following our institutional protocol for a phase I study on RDT. In this work, we present the experimental and theoretical studies that were conducted to insure accurate dose delivery for RDT.
Methods: A LA45 RaceTrack Microtron was commissioned for RDT. LA45 uses scanning electron beams to produce uniform photon dose distributions and a purging magnet to remove the contaminant electrons. Purging efficiency was tested as it could influence machine calibration. The Eclipse system was used for treatment planning. Monte Carlo simulation was used to model 45 MV beams to serve as a second check for RDT. Matrixx 2d array was used treatment plan QA check. Initial trials of portal imaging with the 45MV beam using humanoid phantom showed blurry images, which was attributed to scattered electrons generated by the patient. A 5-mm copper build-up plate was therefore used to insure optimal image contrast and film exposure.
Results: Purging magnet was found to be functional as was seen by the comparison between percentage depth curves of a 10cm x10cm field with and without the purging magnet. The machine was calibrated following TG51. A comparison between the calculated and measured dose distributions was made resulting in 95% of pixels analyzed passing our acceptance criteria. This was achieved with our phantom studies as well as with patients treated in the phase 1 trial. Portal images using 45 MV photons showed better image quality compared to lower energies with the copper buildup
Conclusion: Treatment plans for RDT were designed to facilitate post treatment PET imaging, which were used to dose delivery verification and treatment assessment, and were successfully delivered to patients.