Objectives. Modification of the total body irradiation technique before bone marrow transplantation has been implemented to improve uniformity of the dose inside the irradiated body and to obtain appropriate reduction in doses in critical organs. Methods. The total dose of 12.6 Gy was delivered with the use of a combination of the following fields: lateral, anterior-posterior. field to mediastinum. an electron field to the thorax wall and field to coxa. The doses were calculated for ten transverse body sections. Methods of dose reductions in critical regions by splitting different fields were proposed. Results. The resulting dose deviations inside the body with the combination of all the implemented fields varied from 12.5 Gy to 13.6 Gy along the midline and from 12,4 Gy to 13.7 Gy outside the midline. Doses to the lungs were reduced to 8.6 Gy+9,4 Gy. whereas those in the thorax wall and mediastinum were increased to 12.7 Gy+ 13.5 Gy respectively. Doses to lenses were 12.9 Gy+ 13.1 Gy.

Keywords: Bone Marrow Transplantation, total body irradiation