CALCULATION OF BACKSCATTER FACTORS FOR DIAGNOSTIC-RADIOLOGY USING MONTE-CARLO METHODS

Backscatter factors were determined for x-ray beams relevant to diagno stic radiology using Monte Carlo methods. The phantom size considered most suitable for calibration of dosimeters is a cuboid of 30 x 30 cm( 2) front surface and 15 cm depth. This phantom size also provides a go od approximation to adult patients. Three different media were studied : water, PMMA and ICRU tissue; the source geometry was a point source with varying field size and source-to-phantom distance. The variations of the backscatter factor with phantom medium and field geometry were examined. From the obtained data a set of backscatter factors was sel ected and proposed for adoption as a standard set for the calibration of dosimeters re? be used to measure diagnostic reference doses.