ORGAN DOSES FOR CHILDREN FROM COMPUTED TOMOGRAPHIC EXAMINATIONS

Computed tomography (CT) offers a hi,bh diagnostic capability, but the dose to the patients is high compared to conventional radiography. Fo r estimating the related radiation risk, the assessment of the doses t o individual organs resulting from CT examinations, especially in paed iatrics, is necessary. Therefore, a catalogue of organ doses from CT e xaminations of children was compiled at the GSF. Being applied for spe cial cases rather than for routine examinations, CT is often operated at 'non-standard' situations. For that reason, the doses were calculat ed for single CT slices of 1 cm width at varying positions throughout the body. The results form a data base from which organ doses for indi vidual paediatric examinations can be derived by suitably combining th e calculated values. Two radiation qualities and two exposure geometri es were considered as well as the use of asymmetric beams. The organ d ose conversion factors are applicable to babies (at the age of about 2 months) and to children between 5 and 7 years but can be used for oth er ages as well with the appropriate adjustments. For the calculations , the patients were represented by the GSF tomographic anthropomorphic models BABY and CHILD. The radiation transport in the body was simula ted using a Monte Carlo method. The doses are presented as conversion factors of mean organ doses per air kerma free in air on the axis of r otation.