Purpose: A new radiochromic film dosimetry system consists of the new OrthoChromicTM OC-1 film and a novel calibration procedure was evaluated.
Methods: The novel calibration procedure involved both intensity-to-dose conversion and scanner spatial correction using OrthoChromic-Pro software. Two films, C1 and C2, were exposed simultaneously using the 6xFFF beam with a step-wedge pattern of five 15×3 cm² steps ranging from 590 to 3000 cGy. The films were placed in solid water at 5.0 cm depth and SAD 100 cm. C1 was used for calibration and C2 was used to validate the calibration curves. Another set of films were irradiated to characterize the film system. A film was exposed with an open 20×20 cm² field at SSD 100 cm and 5 cm depth. The beam profile measured with the film was compared to that measured with an IBA cc04 ion chamber in water. To assess the scatter response, the St were generated by exposing films with 1×1 to 10×10 cm² at SSD 100 cm and 10 cm depth. The film St were compared with the stereotactic diode, SD, and cc04 daisy-chained measurements in water. All films were scanned with the Epson 12000XL scanner with 150 dpi and analyzed using an in-house program.
Results: The new calibration procedure was validated with an average dose difference of 1.6% between C1 and C2 and a γ(2%,2mm) passing rate of 100%. For profile, the average absolute difference between cc04 and film within ~80% of field was 0.4% (i.e. profiles were not normalized to each other). The St between films and SD/cc04 were within -0.7% difference on average (range: 0.1% to -1.9%).
Conclusion: Preliminary data has shown that the new film dosimetry system with OC-1 film can achieve highly accurate results. Further studies on energy and intensity modulated fields responses are in progress.
Funding Support, Disclosures, and Conflict of Interest: This work was partially supported by the MSK Cancer Center Support Grant/Core Grant (P30 CA008748).