Highlights
- •Fricke dosimetry as primary standard for the determination of absorbed dose to water.
- •Monte Carlo method and the correction factors associated to Fricke dosimetry.
- •Reduced uncertainties associated to the determination of the absorbed dose to water;
- •Determination of absorbed dose to water for 192Ir HDR sources.
- •Absolute radiation dosimetry for HDR brachytherapy.
Abstract
Purpose
Fricke dosimetry has shown great potential in the direct measurement of the absolute
absorbed dose for 192Ir sources used in HDR brachytherapy. This work describes the determination of the
correction factors necessary to convert the absorbed dose in the Fricke solution to
the absorbed dose to water. Methods: The experimental setup for Fricke irradiation
using a 192Ir source was simulated. The holder geometry used for the Fricke solution irradiation
was modelled for MC simulation, using the PENELOPE. Results: The values of the factors
determined for validation purposes demonstrated differences of less than 0.2% when
compared to the published values. Four factors were calculated to correct: the differences
in the density of the solution (1.0004 ± 0.0004); the perturbations caused by the
holder (0.9989 ± 0.0004); the source anisotropy and the water attenuation effects
(1.0327 ± 0.0012); and the distance from the center of the detection volume to the
source (7.1932 ± 0.0065). Conclusion: Calculated corrections in this work show that
the largest correction comes from the inverse squared reduction of the dose due to
the point of measurement shift from the reference position of 1 cm. This situation
also causes the correction due to volume averaging and attenuation in water to be
significant. Future versions of the holder will aim to reduce these effects by having
a position of measurement closer to the reference point thus requiring smaller corrections.
Keywords
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Article info
Publication history
Published online: April 09, 2021
Accepted:
March 23,
2021
Received in revised form:
March 1,
2021
Received:
September 16,
2020
Identification
Copyright
© 2021 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
