  The aim of this study was to investigate the impact of decay data provided by
the newly developed stochastic atomic relaxation model BrIccEmis on dose point
kernels (DPKs - radial dose distribution around a unit point source) and
S-values (absorbed dose per unit cumulated activity) of 14 Auger electron (AE)
emitting radionuclides, namely 67Ga, 80mBr, 89Zr, 90Nb, 99mTc, 111In, 117mSn,
119Sb, 123I, 124I, 125I, 135La, 195mPt and 201Tl. Radiation spectra were based
on the nuclear decay data from the medical internal radiation dose (MIRD)
RADTABS program and the BrIccEmis code, assuming both an isolated-atom and
condensed-phase approach. DPKs were simulated with the PENELOPE Monte Carlo
(MC) code using event-by-event electron and photon transport. S-values for
concentric spherical cells of various sizes were derived from these DPKS using
appropriate geometric reduction factors. The number of Auger and Coster-Kronig
(CK) electrons and x-ray photons released per nuclear decay (yield) from
MIRD-RADTABS were consistently higher than those calculated using BrIccEmis.
DPKs for the electron spectra from BrIccEmis were considerably different from
MIRD-RADTABS in the first few hundred nanometres from a point source where most
of the Auger electrons are stopped. S-values were, however, not significantly
impacted as the differences in DPKS in the sub-micrometre dimension were
quickly diminished in larger dimensions. Overestimation in the total AE energy
output by MIRD-RADTABS leads to higher predicted energy deposition by AE
emitting radionuclides, especially in the immediate vicinity of the decaying
radionuclides. This should be taken into account when MIRD-RADTABS data are
used to simulate biological damage at nanoscale dimensions.
