The accuracy of dose in vivo measurements during total body irradiation

The aim of this work was to estimate the error in dose calculations, to check the agreement between the measured and calculated doses and to analyse dose discrepancies in the group of thirty patients undergoing total body irradiation. A combination of lateral and anterior posterior fields with electron boost was used in 8 fractions and on 4 consecutive days a Cobalt unit was used as a source of radiation. Lung shields were used at anterior-posterior fields. Compensators were attached at neck, head and legs. Doses were preliminarily calculated and then measured in vivo by thermoluminscent, semiconductor and ionisation dosimeters attached to the body in 10 representative transverse cross-sections. Calculations and measurements were carried out for the beam at the body entry and exit. The error in dose calculations was estimated for each reference point. Dose deviations between calculations and measurements were analysed using the Student's test.