A Monte Carlo study of impact of scan position for cone beam CT on doses to organs and effective dose

The position of the scan isocentre plays a major role in determining the organ doses and effective dose for all regions studied. Nevertheless, values for average effective dose derived at the centre of a region of interest would be suitable for planning treatment regimens and making adjustments to scan protocols. If conversion coefficients based on measurements made at centre of an area of interest were used to evaluate organ doses for individuals, these could lead to significant over/underestimation. The impact of changes in scan position should be taken into consideration when deriving doses to the organs of a patient.