Author: Salim Balik, Nguyen Phuong Dang, Hualin Zhang 👨🔬
Affiliation: Radiation Oncology, Keck School of Medicine of USC 🌍
Purpose: An accurate and convenient monitoring of radiation dose delivery during treatment is essential for ensuring patient safety and treatment efficacy. This project aims to develop innovative algorithms and a comprehensive workflow to streamline the utilization of Gafchromic film (GCF) in the in-vivo dosimetry process.
Methods: GCF is widely used in radiation dosimetry for its ease of use and high spatial resolution. However, there are several challenges associated with its application in in-vivo dosimetry, including workflow complexity and requires expertise in image analysis to ensure accurate dose calculations. The proposed workflow integrates the pre-calibration and correction techniques into a comprehensive in-vivo dosimetry process. Calibration films were scanned at different post-irradiation times (0.5, 1.0, 1.5, 15, 24 h); and two calibration curve sets were established: 1) calibration curves were established using 24h scanned image, 2) time correction curves at different scanning times, as functions of doses. An in-house developed software analyzes the scanned images for film auto detection and calculates doses based on calibration sets. Our film dosimetry approach was compared with a commercially available software which utilizes a traditional film optical density processing method.
Results: A test film set was irradiated with 70, 120, and 250 cGy and scanned at 30-min post-irradiation. The results show that this workflow can achieve dose accuracy within 5% without the need for reference film (one scan protocol) or 16-24 hour waiting time. Our approach reduces the film dose uncertainty, overcomes limitations of color channels and wait times.
Conclusion: The project seeks to broaden the use of GCF in in-vivo dosimetry, improving film calibration and dose measurement procedures. Ultimately, our goal is to establish a simple clinical workflow for patient dose measurement, requiring minimal effort for dose calibration and enabling instant post-measurement processing.