Technical Note: The Uses of I’mRT MatriXX in Electron Beams

Abstract

Purpose: The objective of this study is to investigate the properties of I’mRT MatriXX device in electron beams, and to validate MatriXX in electron dosimetry and quality assurance (QA). Methods: The measurements were conducted using MatriXX in electron and photon beams from Siemens linacs. The MatriXX was placed horizontally on the linac tabletop. Solid Water layers were used for buildup. For all the measurements, the linac gantry angle was 0?, and the source-to-surface distance was100 cmfrom the Solid Water surface. The electron cone factors, cutout factors, and beam profiles were measured and compared with thimble ionization chamber results. Results: The effective water equivalent depth of MatriXX measurement point is larger than4 mm. When measuring at the respective depths of maximum dose, MatriXX has different responses to different beam energies. The cone factors measured by MatriXX are nearly identical or close to those derived by ionization chambers. Beam profiles (flatness and symmetry) can be easily determined using MatriXX and are comparable to water tank results. The planar dose map of electron cutout blocks can be visually observed, and the cutout factors can be conveniently measured. Conclusions: The MatriXX needs separate dose calibration factors for electron and photon beams. MatriXX can be used to measure electron cutout factors and beam profiles, thus has the potentials in electron beam dosimetry and routine linac and patient-specific QA tests.