2215 - Developing and Validating a Novel In Vivo Film Dosimetry System for Accurate Radiation Measurement

R. Aydin¹, A. Viswanathan², and M. F. Chan³; ¹Ashland, Wilmington, DE, United States, ²Ashland, Wilmington, DE, ³Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY

Purpose/Objective(s): Field trials were conducted to assess a novel Point/Skin Dose film-based Medical Dosimetry Systems performance in a real clinical setting, focusing on its efficacy for point/surface dose measurement. The purpose of this investigation is to evaluate the prototype systems accuracy, reliability, and usability for dosimetry in both in vitro or in vivo contexts, applicable in radiotherapy and diagnostic radiology. This system is designed to facilitate patient dose measurement, offering secondary verification of the radiation dose. Materials/

Methods: This study utilized radiochromic film, specifically designed for consistent dose accuracy across a range of from low (3 cGy) to high (450 cGy) radiation doses. The evaluation of the device prototype was conducted through a series of radiation exposures to these predefined dose ranges. Our investigation protocol included an in-depth examination of dose accuracy and an analysis of angular dependence, with assessments performed at 360- degree coverage in 45-degree increments at a 300 cGy dose level using a cylindrical phantom. Additionally, the reproducibility of results was evaluated using five samples under identical experimental conditions at each dose level. The energy dependence of the prototype films was assessed using a medical linear accelerator, equipped with photon energies (6MV, 6FFF, 10FFF, 15MV) and electron energies (6, 9, 12, 16, 20 MeV).
Results: Our analysis revealed that the prototype device exhibits dose accuracy across both low and high dose ranges. Specifically, for low doses ranging from 3 - 80 cGy, the accuracy was within +1 cGy or +20%. For higher doses, from 80 - 450 cGy, the accuracy was within +15cGy or +5%. Angular dependence, which assesses the consistency of dose measurement when the radiation beam traverses the film from different angles, showed a maximum variation of 6.3% - noted when the beam passed through the opposite side of the film. The reproducibility results, which measure the consistency of the devices performance under the same conditions, demonstrated excellent reliability within +2%. The evaluation of energy dependence - how the film responds to different radiation energies - indicated a deviation within 5% of all assessed photon and electron energies, benchmarked to 6MV photons. Based the findings, we recommend that the device be utilized strictly following the established guidelines to ensure optimal performance and accuracy.
Conclusion: The radiochromic film-based point/skin dose measurement system presents several advantages over conventional dosimetry solutions. Key features include its consistent and dose accuracy, which is vital for reliable dosimetry. The system also offers high spatial resolution, enabling intricate 2D dose mapping for comprehensive analysis. Furthermore, its design prioritizes user convenience, with ease of handling and analysis, streamlining the process of conducing dose measurements, positioning it as an advanced tool in medical dosimetry.