Quantitative investigation of the effects of the scanning
parameters in the digitization of EBT and EBT2 Gafchromic film dosimetry with
flatbed scanners
Affiliations: Department of Radiation Oncology, University of
Oklahoma Health Sciences Center, Oklahoma City, OK, USA
Note: [] Corresponding author: Imad Ali, Department of Radiation
Oncology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
73104, USA. E-mail: [email protected]
Abstract: With increasing popularity and complexity of intensity-modulated
radiation therapy (IMRT) delivery modalities including regular and arc
therapies, there is a growing challenge for validating the accuracy of dose
distributions. Gafchromic films have superior characteristics for dose
verification over other conventional dosimeters. In order to optimize the use
of Gafchromic films in clinical IMRT quality assurance procedures, the scanning
parameters of EBT and EBT2 films with a flatbed scanner were investigated. The
effects of several parameters including scanning position, orientation,
uniformity, film sensitivity and optical density (OD) growth after irradiation
were quantified. The profiles of the EBT and EBT2 films had a noise level of
0.6% and 0.7%, respectively. Considerable orientation dependence was observed
and the scanner value difference between landscape and portrait modes were
about 12% and 10% for EBT and EBT2 films, respectively. The highest response
sensitivity was observed using digitized red color images of the EBT2 film
scanned with landscape mode. The total system non-uniformity composed of
contributions from the film and the scanner was less than 1.7%. OD variations
showed that EBT gray scale grew slower, however, reached higher growth values
of 15% when compared with EBT2 gray scale which grew 12% after a long time (480
hours) post-irradiation. The EBT film using the red color channel showed the
minimal growth where OD increased up to 3% within 3 days after irradiation, and
took one week to stabilize.
Keywords: EBT Gafchromic film, film sensitivity, non-uniformity, orientation, optical density growth
