CT-characterisation of bowtiefilters and parameters for dosimetric calculations

CT imaging is the largest man-made source of ionising radiation to the public in developed countries as in Germany. Here more than 60% oft he effective dose delivered to patients is due to CT examinations. However, since only small parts oft he body are exposed to ionising radiation, there are quite large dosest o single organs. To evaluate the dose distributions and ist potential effects further it is necessary to determine dose distributions to various organs in detail. Since it is impossible to measure such doses inside the body simulations have tob e performed. There accuracy depends strongly on an exact characterisation oft he CT parameters including calibrating dose measurements and determination or characterisation o feg the bowtie filter of CT systems. There are various measurements developed and performed to characterise bowtie filters and dose values as a basis fort he following simulation of patient dose distributions.