Programmreport 2012 - DORIS - Bundesamt für Strahlenschutz

of H-1-CSI of approximately 12 mm, functional imaging is suitable for biologically adapted radiotherapy only
to a limited extent. For this purpose, PET/CT is considerably better suited due to the much better spatial resolution
of up to 4.6 mm. This technology additionally allows for dynamic FDG-PET and DCE-CT measurements
for quantitative characterisation of energy metabolism and microcirculation in a single session. The application
and testing of the developed medical physics methods in a radiotherapy study of patients with brain
metastases was started. In the second part of the project, the effect of the static magnetic field on microcirculation
in the muscle of subjects at three MR systems with magnetic flux densities of 1.5, 3 and 7 T should be
investigated. To this end, appropriate measurement techniques have been implemented and validated at the
three systems. Unfortunately, the study with healthy volunteers could not be carried out as planned, as a
whole-body coil was unexpectedly not available.
Within the frame of the project “Construction of hybrid voxel models for optimising image quality
and dose in radiography (3609S40002)“ the following results could be achieved: High-resolution scans
of anatomic specimens, a program tool for incorporating the high-resolution partial body voxel phantoms into
existing reference voxel models, a Monte Carlo radiation transport code that can perform simulations in phantoms
combining various resolutions, and first imaging simulations using such phantoms. The project progress
was hampered by various serious problems, so that the final simulation calculations for the assessment of image
quality could not be performed during the project term. Nevertheless, all methods originally planned to be
used were developed successfully, and possible solutions for the open problems were worked out.
In the project “Feasibility study for the assessment of medical ionising radiation exposure in the
Helmholtz Cohort (German National Cohort) (3610S40001)“ the feasibility of assessing medical radiation
exposures was investigated. Initially a questionnaire for use in the feasibility study was constructed using
available literature. Details of previous x-ray examinations were collected from 199 participants (87 male, 112
female) of the Bremen and Hamburg study centers during face-to-face interviews. All participants reported
having been x-rayed and the most common examinations were dental, upper and lower extremities and chest
x-rays. The most common examination among the 90 (45%) participants who reported CT examinations was
of the skull. Manufacturer's recommendations, guidelines of the German Medical Association as well as conversion
factors published by Drexler et al. 1993 were used to retrospectively estimate organ doses. For CT
examinations, the software CT-Expo was used. A total mean dose of 0.6 mSv was calculated for chest examinations,
with 0.11 mSv for the adrenal glands and the lungs. A mean total organ dose of 52.9 mSv was estimated
for skull-CT examinations.
Within the cohort study on the prevalence of congenital anomalies in the vicinity of nuclear power plants a
higher risk of congenital anomalies was observed amongst children of mothers who were potentially exposed
to ionising radiation in the first trimester of their pregnancy. Since this observation was based only on a small
number of cases the question needed further clarification. Within this feasibility study “Risk for congenital
anomalies in the offspring of women occupationally exposed to ionising radiation in the
medical-diagnostic field (3610S40004)“ contact logistics and recruitment were tested as well as the logistics
for examination of newborn children on congenital anomalies. Since the recruitment via the Radiation
Protection Register of the Federal Office for Radiation Protection (BfS) led to an unexpected low participation
rate an extensive non-responder-analysis was conducted and an alternative recruitment method was tested.
Moreover, dose values for the participating mothers were extracted from the Radiation Protection Register.
For the purpose of data quality validation, a population based comparison cohort from the birth register
"Mainzer Modell" was utilized. Data on radiation exposure of the parents of the newborns were collected within
this comparison group. Based on the results of this feasibility study, the study protocol design for a larger cohort
study was developed.
SUBJECT AREA 05 - RADIOECOLOGY
The estimation of radiation exposures may exhibit uncertainties concerning the scenario, the model structure
and the parameters of exposure models. The project “Comparative examination of probabilistic/stochastic
and deterministic exposure modelling with regard to the reliability of the modelling results
and the requirements concerning the quality of input data (3609S50002)“ focused on the investigation
and comparative assessment of techniques for the consideration of parameter uncertainties by
means of conservative deterministic approaches and probabilistic model calculations using Monte Carlo simulations
and Bayesian methods, respectively. In addition, alternative methods for uncertainty modelling like
evidence and possibility theory, and the conceptual disparities between probabilistic and stochastic modelling
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