In-vivo dosimetry in total body irradiation using GafchromicTM EBT-3 film: A retrospective analysis for quality assurance

Background: Total Body Irradiation (TBI) is a specialized radiotherapy technique and it varies from routine radiotherapy techniques that involve a complex treatment procedure. It is therefore mandatory to perform an in-vivo dosimetry check to ensure dose accuracy and homogeneity during treatment. There is also a clear demand for in-vivo dose validation which must be reliable. The primary objective of this work is to review in-vivo dosimetry measured for our TBI patients using Film. Materials and Methods: In this study, in-vivo dosimetric data of 185 patients who received TBI during 2015 to 2021 were evaluated. The measurements were performed at 14 anatomical sites using Gafchromic (TM) EBT-3 film (The Ashland Inc., Bridgewater, USA). For midplane dosimetry, a special TBI phantom was designed and used for measurements. Result: For most of the patients, the in-vivo dosimetry result and the mean dose to the whole body were within +/- 10% (90.1% - 110%) of the prescription dose. The standard deviation was calculated for all the patients and the values were observed between 2.4cGy to 24cGy. Also, the analysis shows that both surface and mid-plane dosimetry were within the acceptable limits of +/- 10% of prescription dose. The mean mid-plane dose with film and ionization chamber shows 1.5% variation at the umbilicus. Conclusion: This extensive patient data analysis, as well as the reproducibility of patient dosimetry values and dose homogeneity of +/- 10% from the prescription dose, proves that the TBI treatments at our center meet the acceptable limits and EBT3 films are reliable in TBI in-vivo dosimetry.