Abstract

Relative output factors are used in radiation therapy for treatment planning purposes including treatments using kilovoltage X-ray beams. The output factor is the relative dose output for a particular applicator relative to a reference applicator. Due to the differences in the scatter contribution from the inside of an applicator, it is more accurate if output factors are measured for all combinations of X-ray beam energy and applicator. Previously published papers and various kilovoltage X-ray beam dosimetry protocols have discussed the validity of using various cylindrical and parallel plate ionization chambers for relative output factor measurements. In this work, we evaluated the suitability of Gafchromic™ EBT3 film for the determination of output factors for kilovoltage X-ray beams. Output factors were measured with Gafchromic™ EBT3 film for beam qualities of 50, 75, 100 and 125kVp and applicator sizes of 2, 3, 4cm diameter, 8×8 and 12×12cm(2) square applicators. The film read out was performed with a flatbed EPSON Expression10000XL scanner. The measured data was compared with benchmark data from measurements using an Advanced Markus ionisation chamber as well as comparing with ratios of published backscatter factor values. The agreement between output factors measured with EBT3 film and the ionisation chamber was generally better than 2%, with the largest difference of 3.3% occurring for the 2cm diameter field with the 50kVp X-ray beam. These differences were consistent with the estimated total uncertainty in the measurements as calculated by the ISO GUM. The agreement between the output factors measured with film and the published BSFs was generally better than 5% but differences of up to 12% occurred for the smallest field size. The results demonstrate that Gafchromic™ EBT3 film is a suitable dosimeter for output factor measurements of kilovoltage X-ray beams.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.