Background fog subtraction methods in Gafchromic® dosimetry

•Three background fog subtraction methods are studied.•An exponential law is used to test the influence of each method on calibration.•A protocol user friendly and very low time consuming was identified.

We compared three different background fog subtraction methods in order to evaluate their influence on the dose calculation by Gafchromic® films. The research has involved both scanner response uniformity and effects of each method in the Net Optical Density (NOD) determination and dose evaluation. The dosimetric system is set-up by a flatbed scanner EPSON Perfection Pro 750 and External Beam Therapy films (EBT3 model). Photon beams (6 MV), provided by a Siemens Oncor Impression Linear Accelerator, have been used for film irradiation, covering the 0.5–50 Gy range. A clinical proton beam, produced by a superconducting cyclotron, has been used to test the different techniques. Results allow us to define an easy and fast protocol for application, with the accuracy and the precision adequate to clinical practice needs.