AbstractID: 9486 Title: Kodak EDR2 film dosimetry: Effects of film orientation and phantom density
The objective of this study is to test the accuracy of Kadak EDR2 film dosimetry in solid-water and lung-equivalent (cork)
materials. The films are calibrated in a solid-water phantom using the18 MV 10x10 cm2 beams at 100 cm SAD and 3.5 cm
depth. The films are oriented perpendicular to the beam axis and are exposed to 0 to 8.0 Gy during calibration. The optic
densities on each film are scanned with a 16-bit Vidar scanner in a 0.357 mm pixel resolution. The film data are then analyzed
by Root software from CERN. Another film is then irradiated by the same 18 MV beam at 100 cm SSD in a solid water phantom
with the film parallel to the beam axis. The agreement of this measurement with that from a parallel-plate ion chamber ranges
from better than 1% (at dmax) to 3% (at 15 cm depth). Additional 18 MV depth dose profiles are measured with the EDR2 films
and the ion chamber in a cork phantom. Comparison of the film dosimetry (oriented perpendicular to the beam) and ion chamber
measurements shows an agreement to within 1%. The parallel geometry film dosimetry, however, underestimated the dose by
6% in the cork phantom. Our data suggest that caution should be taken when using parallel geometry film dosimetry, especially
in a low-density phantom.