In this paper, we demonstrate the use of functional argument to linearize the inherently nonlinear response of a radiochromic film based reference dosimetry system. In this way, relative dosimetry can be conveniently performed using radiochromic film dosimetry system without the need of establishing calibration curve.
Purpose: A new method to evaluate radiochromic film dosimetry data scanned in multiple color channels is presented. The multi‐channel method allows for the separation and removal of the non‐dose‐dependent portions of a film image and performs superior to the traditional single channel method. Methods: Exposed radiochromic films were scanned in RGB format on a flatbed color scanner and measured to build calibration. Images were converted to dose maps using both single color channel and multi‐channel method. The multi‐channel method allows for the separation of the scanned signal into one dose‐dependent part and another dose‐independent part and enables the correction of a variety of disturbances including non‐ uniformities of the film as well as scanner related artifacts. The fundamental mathematics of the two methods is described and the dose maps calculated with both methods are compared and analyzed. Results: The multi‐channel dosimetry method was shown to remove effectively non‐dose dependent abnormalities from radiochromic dosimetry film images and improve the integrity of the dose information and also reduces random noise in the dose images and mitigates scannerrelated artifacts such as lateral position dependence. In providing an ability to calculate dose maps from data in all the color channels the multi‐channel method provides the ability to examine the agreement between the color channels. The method permit compensation for nonuniformities in the film, increases the signal to noise level, mitigates scanners effect of the calculated dose map and extends the evaluable dose range to 10 cGy – 100. Conclusions: Multi‐channel dosimetry is shown to have significant advantages over single channel method in ensuring the best data integrity and dosimetric accuracy. All authors are employees of International Specialty Products, Manufacturer of Gafchromic Films
Purpose: To assess the possibility of using a public calibration function for radiochromic film dosimetry in dose QA of highly conformal treatment plans. Methods: EBT3 film calibration strips (3.5×20cm2 from lots A101212 and A011713) were exposed on a Varian Trilogy at a facility to a 10×10cm2 open field at doses of 80,160,320 cGy using 6MV photons. Together with a strip of unexposed film from the same lot the exposed films were digitized in a single scan using different Epson 10000XL scanners at two different facilities. The dose‐response data for each color‐channel from each facility were generated using the same calibration function X(D) = a + b/(D‐c), where X(D) is the response at dose D and a, b and c are the coefficients. Different batches of EBT3 film were exposed to a VMAT beam. These films, plus two reference strips exposed to doses of zero and 160 cGy, were digitized on the scanners at the two facilities. Using the multi‐channel dosimetry method and One‐scan protocol (Med Phys, 39:6339‐49, 2012) the recorded doses on the VMAT films were calculated and the results were compared with the VMAT plan using a Gamma index of 3%/3mm. Results: The passing rates obtained for dose maps calculated for all combinations of VMAT images and calibration functions were nearly unchanged, using the One‐scan protocol. Also, in all cases a passing rate of >99% was obtained for Gamma index of 3%/3mm. On the other hand, if the One‐scan protocol was not employed, the dose maps for VMAT images and calibration functions from different scanners showed poor correlation with the treatment plan. This is probably due to the scan‐to‐scan variability. Conclusion: We have found that it is feasible to use a public calibration function for a given radiochromic film lot using the same methodology, One‐scan protocol, for patient‐specific QA. Two of the authors are the employees of Ashland Inc., the manufacturer of GafChromic film.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.