Knowledge of absorbed dose in the skin of a patient and in the build-up region in the photon beams of linear accelerators is very important in the clinical practice of radiotherapy. The values of these doses depend not only on the quality of the beam and its collimation, but also on the use of beam modifiers, such as wedges, beam shaping blocks and especially on the means of patient immobilisation. In vivo determination of the skin and build-up dose is very difficult and assessment of their values is usually performed on phantoms. The aim of the present work was to verify a method, allowing the use of available equipment for evaluation of skin and build up dose in different clinical situations. Actual doses measured in photon beamsof linear accelerator Clinac 2100 Care presented.

        Key words: linear accelerator - depth dose - build-up region