Detector to detector corrections: A comprehensive experimental study of detector specific correction factors for beam output measurements for small radiotherapy beams.
Loading...
Date
2014-07
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Medical Physics
Abstract
Purpose: The aim of the present study is to provide a comprehensive set of detector specific correction
factors for beam output measurements for small beams, for a wide range of real time and passive
detectors. The detector specific correction factors determined in this study may be potentially useful
as a reference data set for small beam dosimetry measurements.
Methods: Dose response of passive and real time detectors was investigated for small field sizes
shaped with a micromultileaf collimator ranging from 0.6 × 0.6 cm2 to 4.2 × 4.2 cm2 and the measurements
were extended to larger fields of up to 10 × 10 cm2. Measurements were performed at
5 cm depth, in a 6 MV photon beam. Detectors used included alanine, thermoluminescent dosimeters
(TLDs), stereotactic diode, electron diode, photon diode, radiophotoluminescent dosimeters
(RPLDs), radioluminescence detector based on carbon-doped aluminium oxide (Al2O3:C), organic
plastic scintillators, diamond detectors, liquid filled ion chamber, and a range of small volume air
filled ionization chambers (volumes ranging from 0.002 cm3 to 0.3 cm3). All detector measurements
were corrected for volume averaging effect and compared with dose ratios determined from alanine
to derive a detector correction factors that account for beam perturbation related to nonwater equivalence
of the detector materials.
Results: For the detectors used in this study, volume averaging corrections ranged from unity for the
smallest detectors such as the diodes, 1.148 for the 0.14 cm3 air filled ionization chamber and were
as high as 1.924 for the 0.3 cm3 ionization chamber. After applying volume averaging corrections,
the detector readings were consistent among themselves and with alanine measurements for several
small detectors but they differed for larger detectors, in particular for some small ionization chambers
with volumes larger than 0.1 cm3.
Description
Published Journal Article
Keywords
Small fields, Small field dosimetry, Volume effects, Dose response, Detector corrections for small fields
Citation
Azangwe, G. 2014. Detector to detector corrections: A comprehensive experimental study of detector specific correction factors for beam output measurements for small radiotherapy beams. Medical Physics.