Surface and buildup region dose measurements with Markus parallel-plate ionization chamber, Gafchromic EBT3 film and MOSFET detector for high energy photon beams

TL;DR

This study compares surface and buildup region dose measurements using three different detectors for high energy photon beams, highlighting how measurement depth and beam angle affect dose readings.

Contribution

It provides a comparative analysis of Markus chamber, Gafchromic EBT3 film, and MOSFET detectors for surface dose measurements in high energy photon beams.

Findings

Surface dose increases with field size and beam obliquity.

Different detectors show varying surface dose readings due to measurement depth.

Measurement depth differences can lead to errors in surface dosimetry.

Abstract

The aim of the study was to investigate surface and buildup region doses for 6MV and 15MV photon beams using a Markus parallel-plate ionization chamber, GafChromic EBT3 film, and MOSFET detector for different field sizes and beam angles. The measurements were made in a water equivalent solid phantom at the surface and in the buildup region of the 6MV and 15MV photon beams at 100 cm source-detector distance for 5 x 5, 10 x 10, and 20 x 20 cm2 field sizes and 0, 30, 60, and 80 beam angles. The surface doses using 6MVphoton beams for 10 x 10 cm2 field size were found to be 20.3%, 18.8%, and 25.5% for Markus chamber, EBT3 film, and MOSFET detector, respectively. The surface doses using 15MV photon beams for 10 x 10 cm2 field size were found to be 14.9%, 13.4%, and 16.4% for Markus chamber, EBT3 film, and MOSFET detector, respectively. The surface dose increased with field size for all dosimeters. As the angle of the incident radiation beam became more oblique, the surface dose increased. The effective measurement depths of dosimeters vary; thus, the results of the measurements could be different. This issue can lead to mistakes at surface and buildup dosimetry and must be taken into account.