[Use of shielding blocks for field formation in gamma teletherapy]

Based on experimentally obtained dose distributions for irregular fields formed on the Rokus-M apparatus by means of shield blocks, a formula for the manual calculation of a dose rate in the open part of an irregular field was proposed. The formula makes use of the tissue air ratio and takes into account change of an equivalent field area in case of the use of central, shifted and edge blocks or their combinations.