ANGULAR-DEPENDENCE FACTORS AND AIR KERMA TO DOSE-EQUIVALENT CONVERSION COEFFICIENTS FOR CYLINDRICAL PHANTOMS IRRADIATED BY PLANE-PARALLEL EXTENDED MONOENERGETIC PHOTON BEAMS

With the aid of the Monte Carlo method, conversion coefficients betwee n the receptor-free air collision kerma and the collision kerma for 4- element ICRU tissue have been calculated at a depth of 0.007 g.cm-2 in circular cylinder phantoms irradiated by broad plane-parallel photon beams in a direction perpendicular to the cylinder main axis. The phan tom material was ICRU tissue or PMMA; the phantom diameter 1.9 cm, 7.3 cm, or 30 cm; the phantom length 30 cm. The calculations were perform ed for monoenergetic photons in the energy range between 4 keV and 1.2 5 MeV. The conversion coefficients can be used in the field of extremi ty dosimetry to convert measured kerma or exposure values into persona l dose equivalents: the results for the 7.3 cm diameter cylinder phant oms for the calibration of wrist or ankle dosemeters; those for the 1. 9 cm diameter phantoms for the calibration of finger dosemeters. In ad dition to the conversion coefficients, their angular dependence factor s in the middle plane of the phantoms perpendicular to the main axis w ere also studied. Such quantities for the ICRU tissue phantoms are nec essary in the procedure for type testing extremity dosemeters on rod o r pillar phantoms.