Gafchromic EBT3 Radiochromic Films Research Articles

Dosimetric Characterization of DSF/NaOH/IA-PAE/R. spp. Phantom Material for Radiation Therapy

Background: Different compositions of DSF/NaOH/IA-PAE/R. spp. composite particleboard phantoms were constructed. Methods: Photon attenuation characteristics were ascertained using gamma rays from 137Cs and 60Co. Absorbed doses at the location of an ionization chamber and Gafchromic EBT3 radiochromic films were calculated for high-energy photons (6 and 10 MV) and electrons (6, 9, 12, and 15 MeV). Results: The calculated TPR20,10 values indicate that the percentage discrepancy for 6 and 10 MV was in the range of 0.29-0.72% and 0.26-0.65%. It was also found that the relative difference in the dmax to water and solid water phantoms was between 1.08-1.28% and 5.42-6.70%. The discrepancies in the determination of PDD curves with 6, 9, 12, and 15 MeV, and those of water and solid water phantoms, ranged from 2.40-4.84%. Comparable results were found using the EBT3 films with variations of 2.0-7.0% for 6 and 10 MV photons. Likewise, the discrepancies for 6, 9, 12, and 15 MeV electrons were within an acceptable range of 2.0-4.5%. Conclusions: On the basis of these findings, the DSF/NaOH/IA-PAE/R. spp. particleboard phantoms with 15 wt% IA-PAE addition level can be effectively used as alternative tissue-equivalent phantom material for radiation therapy applications.

Skin Dosimetry with EBT3 Radiochromic Film in Radiotherapy of Parotid Cancer.

Background: Skin is a sensitive organ and should be spared in radiotherapy and irradiation of skin in radiotherapy can cause to acute and late skin effects such as erythema, desquamation, epilation, color change, or even necrosis. Objective: The aim of the present study is to do skin dosimetry in radiotherapy of parotid cancer using Gafchromic EBT3 radiochromic film. EBT3 radiochromic films were calibrated in 0.2-5 Gy dose range.Material and Methods: This is an experimental study in the field of radiotherapy physics. Treatment planning was performed on a RANDO phantom for treatment of parotid cancer by a clinical oncologist. Based on the treatment planning, the skin dose at various points in the overlapping region of right anterior-oblique and right posterior-oblique fields were measured using EBT3 radiochromic film.Results: The minimum and maximum skin doses in a fraction (with 2.0 Gy prescribed dose) were 0.50 Gy and 0.97 Gy, respectively. Based on these values, the total skin dose in 30 treatment fractions (for removed tumor) or in 35 treatment fractions (for unremoved tumor) was in the range of 15-33 Gy. Conclusion: Based on the skin dosimetry results of parotid cancer radiotherapy using EBT3 films, it is predicted that there will occur mild skin reactions and these reactions can be neglected due to being mild.

SU-E-T-94: Surface Dose Characteristics of Flattened and Flattening Filter Free Megavoltage Photon Beam

Purpose: To evaluate the surface dose characteristics of the flattened and flattening filter free (FFF) megavoltage photon beam with radiochromic film and compare the Result: with that from ion chamber. Methods: A Varian TrueBeam linear accelerator capable to produce both flattened and FFF photon at 6 MV and 10 MV was used in this study. Surface dose measurement was performed with both Gafchromic EBT3 radiochromic film and PTW23342 parallel plate chamber. Build-up dose was measured by adding different thickness of solid water slabs on the top of the measuring devices, at 100 cm SSD with field size of 2×2, 5×5, 10×10 and 20×20 cm2. The measurement data were normalized to PDD at 5 cm depth which was obtained from commissioning data. Percentage surface dose was calculated by extrapolating the PDD from 2 mm build-up to the surface. Results: Surface doses of the FFF photon were 5 – 10% higher than that of the flattened photon at field size smaller than 10×10 cm2. In film measurement, the surface doses for 6X flattened and FFF photon increased from 12.0% to 30.6% and 20.5% to 36.1% respectively, when field size increased from 2×2 to 20×20 cm2; for 10X flattened and FFF photon, they were increased from 6.1% to 24.2% and 11.2% to 23.5% respectively. Surface dose obtained in chamber measurement showed 2 – 6% higher than the corresponding measurement with film, but with a similar trend with that in the film measurement. Conclusion: FFF photon has a higher surface dose than flattened photon at field size smaller than 10×10 cm2. Surface dose measured from chamber is found to be higher than that from film, which is probably due to the chamber design. Nonetheless, the trend of surface dose increases with field size is consistent between the two measuring devices.