AbstractID: 8189 Title: In Vivo Dosimetry of High Dose Rate Brachytherapy Using an Improved Radiochromic
Film
Despite many advantages of radiochromic films for dosimetry, their low sensitivity in the range of < 5 Gy has
limited their application for daily in vivo dosimetry. With the advent of an improved radiochromic film, we
investigate its potential as an in vivo dosimeter for fractionated HDR brachytherapy. A new radiochromic film has
higher sensitivity in the range of 0.5−40 Gy. This film was calibrated from 0 to 50 Gy using a 6 MV photon beam
and, then read by a scanning densitometer of filtered fluorescence. The film readings on the surface of HDR vaginal
cylinders were compared with the dose calculated from a treatment planning system (TPS) to validate the
radiochromic film as an in vivo dosimeter. The optical density response was quite linear in the low dose range of
0.5−10 Gy using a red filter. The optical density in the range of >10 Gy was constant within 3% difference between
24 h and 72 h after exposure, but in the range of < 5 Gy, the variation of the optical density vs. post-irradiation
affected the readings. In vivo patient doses were determined to be 2%−4% less in the red filter than the dose of TPS.
Reproducibility of doses on the surface of the applicator showed < 5% variation between different fractions. In
daily dose range of fractionated HDR treatment, the new radiochromic film read with the red filtered light could
offer a simple and expedient way to directly verify and document the dose delivered to the patient.