Highlights
- •Relevance of Internal Bremsstrahlung (IB) in 32P DPK evaluation was highlighted.
- •DPK including IB is up to 40% larger than the values available in literature.
- •IB inclusion in MC codes among processes related to beta decay is advisable.
Abstract
Purpose
In nuclear medicine, Dose Point Kernels (DPKs), representing the energy deposited
all around a point isotropic source, are extensively used for dosimetry and are usually
obtained by Monte Carlo (MC) simulations. For beta-decaying nuclides, DPK is usually
estimated neglecting Internal Bremsstrahlung (IB) emission, a process always accompanying
the beta decay and consisting in the emission of photons having a continuous spectral
distribution. This work aims to study the significance of IB emission for DPK estimation
in the case of 32P and provide DPK values corrected for the IB photon contribution.
Methods
DPK, in terms of the scaled absorbed dose fraction, , was first estimated by GAMOS MC simulation using the standard beta decay spectrum
of 32P, . Subsequently, an additional source term accounting for IB photons and their spectral
distribution was defined and used for a further MC simulation, thus evaluating the
contribution of IB emission to DPK values, . The relative percent difference, δ, between the DPKs obtained by the two approaches,
vs. , was studied as a function of the radial distance, R.
Results
As far as the energy deposition is mainly due to the beta particles, IB photons does
not significantly contribute to DPK; conversely, for larger R, values are higher by 30–40% than .
Conclusions
The inclusion of IB emission in the MC simulations for DPK estimations is recommended,
as well as the use of the DPK values corrected for IB photons, here provided.
Keywords
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Article info
Publication history
Published online: April 27, 2023
Accepted:
April 7,
2023
Received in revised form:
March 3,
2023
Received:
December 2,
2022
Identification
Copyright
© 2023 Published by Elsevier Ltd on behalf of Associazione Italiana di Fisica Medica e Sanitaria.
