Dose-rate distribution under partially shielded beams.

We are presenting a method of calculating the dose-rate distributions in partially shielded field. An attenuator was placed in central beam axis and also in an off-axis geometry. The study was made with a Co-60 radiation and with photons generated by 10 and 23 MV Linac at depths, in phantom, from 5 to 30 cm. To obtain the calculated values of dose-rates; the contributions of the three components to the total dose-rate were measured. The calculated dose-rate distributions agree well with the measured data in case of 10 MV and 23 MV radiation.