AbstractID: 6628 Title: Dosimetric Characteristics of New Gafchromic-HS Film
With increasing complexity of dose verification for intensity modulated radiation therapy
(IMRT), high gradient dosimetry and endovascular brachytherapy, Gafchromic film is an
attractive alternative compared to the existing dosimeters. New Gafchromic type HS film
eliminates most of the problems associated with the radiographic films. The HS film is 40
µm thick and nearly tissue equivalent (1.1g/cm3) which is sandwiched between two (100 µm)
layers of polyester substrate to allow dosimetry measurements in a water phantom.
Dosimetric characteristics of HS film (dose linearity, dose rate dependence, energy
dependence, orientation, and temperature dependence) are presented in the solid and water
phantoms. Our results indicate that HS film is linear between 10-4800cGy and independent
of dose rate between 50 cGy/min up to 650 cGy/min. The optical density (OD) of the film is
energy independent for all megavoltage photon and electron beams used clinically. The
orientational (parallel and perpendicular) response is minimum (2%). The OD of the film is
dependent on the temperature of the water phantom at the time of exposure and the duration
between exposure and reading time. The OD increases with temperature and falls off at
higher (>40°C) temperature. The OD also increases with the duration of reading time. It is
concluded that the new Gafchromic-HS film is ideally suited for dosimetric verification in
the IMRT, high gradient dosimetry and endovascular brachytherapy. Precautions, however,
are needed for the temperature of the medium and the time of readout if in-water
measurements are performed.