Radiochromic film dosimetry for Ir-192 HDR source: Determination of
TG43 parameters
Sou-Tung Chiu-Tsao
Quality MediPhys LLC,
Radiochromic film (GAFCHROMIC®
EBT) was used to measure 2-dimensional dose distributions for Ir-192 HDR v2 source
in solid water out to 5cm. A
multiple film technique was employed.
Each film (EBT lot #35076) was in contact geometry with a 6F catheter,
in which an Ir-192 HDR source (Nucletron v2 microSelectron) was driven to the
center of a solid water phantom, 30x30x20 cm. Totally 4 experimental films were
separately exposed, with exposure times of 5s, 20s, 200s, and 300s. The source activity was 9.75 Ci at the
time of experiment. 17 calibration
films were exposed to the same source at about 1 cm above, with exposure times
ranging from 2s to 420s and the film center doses from 0.2 to 38 Gy. All experimental, calibration and
background films were scanned (pixel resolution 0.2mm) using a PeC CCD100
densitometer, with red and green light sources at least two days after
exposures. Conversion from optical
densities to doses was achieved based on the calibration curve established for
each light source used in scanning.
The 2-d dose rate values in cylindrical coordinates were converted to
polar coordinates, and the TG43 parameters were generated. The radial dose function and anisotropy
function were plotted. They agree
with the