Highlights
- •Application of the kS factor in PDD(10) and kvol in FFF beams could be essential.
- •Error combination in dose calibration of FFF beams could otherwise approach 2%.
- •Error combination in FFF beams calibration for most common chambers is within 1%
Abstract
Purpose
To examine whether it is essential to apply correction factors for ion recombination
(kS) to percentage depth dose (PDD) measurements and to the volume-averaging effect (kvol) to ensure accurate absolute dose calibration for flattening filter-free (FFF) beams
for the most commonly used ionization chambers.
Methods
We surveyed medical physicists worldwide (n = 159) to identify the five most common
ionization chamber combinations used for absolute and relative reference dosimetry
of FFF beams. We then assessed the overall absolute dose calibration error for FFF
beams of the Artiste Siemens and TrueBeam Varian linear accelerators resulting from
failing to apply correction factors kS in the PDD(10) and the volume-averaging effect (kvol) to such chamber combinations.
Results
All the chamber combinations examined—the Farmer PTW 30013 ionization chamber used
for absolute dosimetry, and the PTW 31010, PTW 30013, IBA CC04, IBA CC13, and PTW
31021 ionization chambers used for PDD curves measurements—showed non-negligible errors
(≥0.5%). The largest error (1.6%) was found for the combination of the Farmer PTW
30013 chamber with the IBA CC13 chamber, which was the most widely used chamber combination
in our survey.
Conclusions
Based on our findings, we strongly recommend assessing the impact of failing to apply
correction factors kS in the PDD(10) and kvol prior to using any chamber type for FFF beam reference dosimetry purposes.
Keywords
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Article info
Publication history
Published online: August 29, 2020
Accepted:
July 5,
2020
Received in revised form:
July 2,
2020
Received:
April 4,
2020
Identification
Copyright
© 2020 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
