Academic Publications
Links to full-text articles can be found in the description
October 2022
A Software for Calculating Dose Coefficients for Fetus and Newborn Following Intakes of Radioisotopes by the Mother
Poster for ERPW Portugal • 2022
February 2021
Organ doses of the fetus from external environmental exposures
Radiation and Environmental Biophysics • 2021 Link
This article presents nuclide-specific organ dose rate coefficients for environmental external exposures due to soil contamination assumed as a planar source at a depth of 0.5 g cm−2 in the soil and submersion to contaminated air, for a pregnant female and its fetus at the 24th week of gestation. Furthermore, air kerma free-in-air coefficient rates are listed. The coefficients relate the organ equivalent dose rates (Sv s−1) to the activity concentration of environmental sources, in Bq m−2 or Bq m−3, allowing to time-integrate over a particular exposure period. The environmental radiation fields were simulated with the Monte Carlo radiation transport codes PHITS and YURI. Monoenergetic organ dose rate coefficients were calculated employing the Monte Carlo code EGSnrc simulating the photon transport in the voxel phantom of a pregnant female and
fetus. Photons of initial energies of 0.015–10 MeV were considered including bremsstrahlung. By folding the monoenergetic dose coefficients with the nuclide decay data, nuclide-specific organ doses were obtained. The results of this work can be
employed for estimating the doses from external exposures to pregnant women and their fetus, until more precise data are available which include coefficients obtained for phantoms at different stages of pregnancy.
September 2020
Uncertainty analysis in internal dose calculations for cerium considering the uncertainties of biokinetic parameters and S values
Radiation and Environmental Biophysics • 2020 Link
Radioactive cerium and other lanthanides can be transported through the aquatic system into foodstuffs and then be incorporated by humans. Information on the uncertainty of reported dose coefficients for exposed members of the public is then
needed for risk analysis. In this study, uncertainties of dose coefficients due to the ingestion of the radionuclides 141Ce and 144Ce were estimated. According to the schema of internal dose calculation, a general statistical method based on the propagation
of uncertainty was developed. The method takes into account the uncertainties contributed by the biokinetic models and by the so-called S values. These S-values were derived by using Monte Carlo radiation transport simulations with five adult non-reference voxel computational phantoms that have been developed at Helmholtz Zentrum München, Germany. Random and Latin hypercube sampling techniques were applied to sample parameters of biokinetic models and S values. The uncertainty factors, expressed as the square root of the 97.5th and 2.5th percentile ratios, for organ equivalent dose coefficients of 141Ce were found to be in the range of 1.2–5.1 and for 144Ce in the range of 1.2–7.4. The uncertainty factor of the detriment-weighted dose coefficient for 141Ce is 2.5 and for 144Ce 3.9. It is concluded that a general statistical method for calculating the uncertainty of dose coefficients was developed and applied to the lanthanide cerium. The dose uncertainties obtained provide improved dose coefficients for radiation risk analysis of humans. Furthermore, these uncertainties can be used to identify those parameters most important in internal dose calculations by applying sensitivity analyses.
November 2019
Measurement, model prediction and uncertainty quantification of plasma clearance of cerium citrate in humans.
Radiation and Environmental Biophysics • Vol. 59 Link
Double tracer studies in healthy human volunteers with stable isotopes of cerium citrate were performed with the aim of investigating the gastro-intestinal absorption of cerium (Ce), its plasma clearance and urinary excretion. In the present
work, results of the clearance of Ce in blood plasma are shown after simultaneous intravenous and oral administration of a Ce tracer. Inductively coupled plasma mass spectrometry was used to determine the tracer concentrations in plasma. The results show that about 80% of the injected Ce citrate cleared from the plasma within the 5 mins post-administration. The data obtained are compared to a revised biokinetic model of Ce, which was initially developed by the International Commission on Radiological Protection (ICRP). The measured plasma clearance of Ce citrate was mostly consistent with that predicted by the ICRP biokinetic model. Furthermore, in an effort to quantify the uncertainty of the model prediction, the laboratory animal data on which the ICRP biokinetic Ce model is based, was analyzed. The measured plasma clearance and its uncertainty was also compared to the plasma clearance uncertainty predicted by the model. It was found that the measured plasma clearance during the first 15 min after administration is in a good agreement with the modelled plasma clearance. In general, the measured clearance falls inside the 95% confidence interval predicted by the biokinetic model.
June 2018
Finding sensitive parameters in internal dose calculations for radiopharmaceuticals commonly used in clinical nuclear medicine.
Radiation and Environmental Biophysics • Vol. 57 • Issue 3. Link
Internal dosimetry after incorporation of radionuclides requires standardized biokinetic and dosimetric models. The aim of the present work was to identify the parameters and the components of the models which contribute most to dosimetric uncertainty. For this a method was developed allowing for the calculation of the uncertainties of the absorbed dose coefficients. More specifically, the sampling-based regression method and the variance-based method were used to develop and apply a global method of sensitivity analysis.
February 2017
Unsicherheits- und Sensitivitäts-analysen von Kompartiment-Modellen und Computer-Voxel-Phantomen für interne Strahlen-exposition der Patienten durch Radiopharmazeutika in der Nuklearmedizin.
Dissertation.
Das Hauptziel dieser Arbeit ist, eine statistische Methode zu entwickeln, um die Unsicherheiten und damit die Zuverlässigkeit der Patientendosen durch die ausgewählten Radiopharmazeutika zu quantifizieren. Im Rahmen einer Sensitivitätsanalyse werden zudem die biokinetischen sowie dosimetrischen Parameter identifiziert, die den größten Einfluss auf die Patientendosis haben und somit am meisten zur Unsicherheit der Dosiskoeffizienten beitragen. Die Unsicherheits- und die Sensitivitätsanalyse wurde für die folgenden sieben in der nuklearmedizinischen Diagnostik häufig angewandten Radiopharmazeutika durchgeführt: 18F FDG, 99mTc Pertechnetat, 99mTc Phosphonat, 99mTc Sestamibi, 99mTc Tetrofosmin, 99mTc Macro-Aggregated-Albumin (MAA), und 201Tl Chlorid.
January 2016
Uncertainty Quantification in Internal Dose Calculations for Seven Selected Radiopharmaceuticals.
The Journal of Nuclear Medicine • Vol. 57 • No. 1. Link
Dose coefficients of radiopharmaceuticals have been published by the International Commission on Radiological Protection (ICRP) and the MIRD Committee but without information concerning uncertainties. The uncertainty information of dose coefficients is important, for example, to compare alternative diagnostic methods and choose the method that causes the lowest patient exposure with
appropriate and comparable diagnostic quality. For the study presented here, an uncertainty analysis method was developed and used to calculate the uncertainty of the internal doses of 7 common radiopharmaceuticals.
November 2015
Ermittlung der Zuverlässigkeit von Dosiskoeffizienten für Radiopharmaka.
Technical Report von BfS Link
Das Ziel dieser Arbeit ist es die Unsicherheiten und damit die Zuverlässigkeit von Dosiskoeffizienten für ausgewählte Radiopharmaka zu ermitteln sowie die biokinetischen und dosimetrischen Parameter zu identifizieren, die am meisten zur Unsicherheit der Dosiskoeffizienten beitragen.
