Introduction: This study describes a simple method of inter‑fractional photon beam monitoring to measure the entrance dose of
radiation treatment using Gafchromic EBT3 film.
Materials and Methods: The film was placed at the center of a 1‑cm thick phantom shaped like a block tray and fixed on the
accessory tray of the gantry. The entrance dose was measured following the placement of the film in the accessory tray. The
dose distribution calculated with the treatment planning system was compared with the dose distribution on the irradiated EBT3
films. The effectiveness of this methodology, as determined by gamma passing rates, was evaluated for the 22 fields of eight
three‑dimensional conformal radiotherapy (3D‑CRT) plans and the 41 fields of nine intensity‑modulated radiotherapy (RT) plans.
The plans for three‑dimensional conformal RT included treatments of the rectum, liver, breast, and head and neck, whereas the
plans for intensity‑modulated RT included treatments of the liver, brain, and lung.
Results: The gamma passing rates for 3D‑CRT ranged from 96.4% to 99.5%, with the mean gamma passing rate for 22 fields
being 98.0%. The gamma passing rate for intensity‑modulated RT ranged from 96.1% to 98.9%, with the mean gamma passing
rate for 41 fields being 97.7%. All gamma indices were over the 95% tolerance level.
Conclusions: The methodology described in this study, based on Gafchromic EBT3 film, can be utilized for inter‑fractional entrance
dose monitoring as quality assurance during RT. Clinical application of this method to patients can verify the accuracy of beam
delivery in the treatment room.
Sun Young
Moon
Department of Bio‑convergence Engineering, Korea University, Seoul
Proton Therapy Center, National Cancer Center, Goyang, Korea
Yunhui Jo,
Jaehyeon Seo, Myonggeun Yoon
Department of Bio‑convergence Engineering, Korea University, Seoul
Dongho Shin,
Proton Therapy
Center, National
Cancer Center,
Goyang, Korea
Journal of Cancer Research and Therapeutics - Volume 18 - Issue 4 - July-September 2022: 1152-1158