Issues on VMAT QA Program with EBT3 Radiochromic Films: An improvement proposal
Palavras-chave:Gafchromic film, Calibration Curves, Patient Specific Quality Assurance, Instability, Cost-Benefit
ResumoEBT3 radiochromic film is renowned in medical physics field due its dose verification for Quality Assurance (QA) program in intensity-modulated radiotherapy (IMRT). However, it is known that QA programs, which include these films, are expensive and relatively time-consuming. Furthermore, it was noted that dosimetry with EBT3 film has been suffering with lack of accuracy. In that way, it was evaluated its possible dosimetric inaccuracy, the time expenditure in the whole QA process, as well as the cost-benefit of such a program and it is suggested efforts to improve this process based on our institution expertise. A retrospective study was performed on VMAT
plans, rating how many cases got success by absolute dosimetric Gamma analysis. Furthermore, in order to verify the film intra-lot aging, the calibration curves were compared to the lot fabrication date. On the other hand, with single- and multi-channel dosimetric analyses, further trials were performed over the post-irradiation
saturation curves up to 35 h after irradiation. The retrospective Gamma analyses exhibited that about 23% of the total VMAT cases did not passed by absolute Gamma evaluation. It was seen that the fabrication date influences the dose response, which prerequisites a calibration curve for each film box. For the multichannel
analyses, as excepted, the red channel sensitivity was the highest for doses up to 5 Gy. Moreover, it was reinforced that the dose response is a direct function of dose level for both types of analyses. In that way, it was chosen a post-irradiation time interval of 12h-16h, with dose response variation criteria less than 2%. Finally, it was verified, based on our routine, that there were about 23h/month expended in a film QA program and directly costs bordering US$20,000.00/year.
Casanova BV, Pasquino M, Russo G, Grosso P, Cante D, Sciacero P, et al. Dosimetric characterization and use of GAFCHROMIC EBT3 film for IMRT dose verification. J Appl Clin Med Phys. 2013;14(2):4111.
Aland T, Kairn T, Kenny J. Evaluation of a Gafchromic EBT2 film dosimetry system for radiotherapy quality assurance. Australas Phys Eng Sci Med. 2011;34(2):251-60.
Sankar A, Ayyangar KM, Nehru RM, Kurup PG, Murali V, Enke CA, Velmurugan J. Comparison of Kodak EDR2 and Gafchromic EBT film for intensity-modulated radiation therapy dose distribution verification. Med Dosim. 2006;31(4):273-82.
Khachonkham S, Dreindl R, Heilemann G, Lechner W, Fuchs H, Palmans H, Georg D, Kuess P. Characteristic of EBT-XD and EBT3 radiochromic film dosimetry for photon and proton beams. Phys Med Biol. 2018;63(6):65007.
Gafchromic radiotherapy films. Ashland, KY. [cited 2018 Apr 1] Available from: http://www.ashland.com/products/gafchromic-radiotherapy-films.
Niroomand-Rad A, Blackwell CR, Coursey BM, et al. Radiochromic film dosimetry. AAPM Report No. 63. Recommendations of the AAPM Radiation Therapy Committee, TG No. 55. Med Phys. 1998;25(11):2093–115.
Saur S, Frengen J. EBT film dosimetry with flatbed CCD scanner: a novel background correction method and full dose uncertainty analysis. Med. Phys. 2008;35(7):3094-101.
Andres C, Del Castillo A, Tortosa R, Alonso D, Barquero R. A comprehensive study of the Gafchromic EBT2 radiochromic film. A comparison with EBT. Med Phys. 2010;37(12):6271-78.
Rink A, Lewis DF, Varma S, Vitkin IA, Jaffray DA. Temperature and hydration effects on absorbance spectra and radiation sensitivity of radiochromic medium. Med Phys. 2008;35(10):4545-55.
Lewis DF; Performance of the Vidar® Red LED Dosimetry Pro Advantage™: A scanner optimized for use with GAFCHROMIC® EBT Dosimetry Film. Advanced Materials Group, International Specialty Products, Wayne, NJ.
EPSON EXPRESSION 10000XL. [cited 2018 Apr 1] Available from: http://www.epson.pt/products/scanners/business-scanners/epson-expression-10000xl.
Pérez Azorín JF, Ramos García LI, Martí-Climent JM. A method for multichannel dosimetry with EBT3 radiochromic films. Med Phys. 2014;41(6):062101.
Marrazzo L, Zani M, Pallotta S, Arilli C, Casati M, Compagnucci A, Talamonti C, Bucciolini M. GafChromic(®) EBT3 films for patient specific IMRT QA using a multichannel approach. Phys Med. 2015;31(8):1035-1042.
Low DA, Harms WB, Mutic S, Purdy JA. A technique for the quantitative evaluation of dose distributions. Med Phys. 1998;25(5):656-61
Ezzel GA, Burmeister JW, Dogan N, LoSasso TJ, Mechalakos JG, Mihailidis D, et al. IMRT commissioning: Multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119: IMRT commissioning. Medical Physics. 2009;36(11):5359-73.
Marroquin EY, Herrera González JA, Camacho López MA, Barajas JE, García-Garduño OA. Evaluation of the uncertainty in an EBT3 film dosimetry system utilizing net optical density. J Appl Clin Med Phys. 2016;17(5):466-481.