CALCULATION OF ABSORBED DOSE DUE TO THE Y-90-DOTATOC PEPTIDE RECEPTOR RADIONUCLIDE THERAPY BY MCNP5/X

Strong beta emitters, like Y-90, Lu-177 labelled peptide, are used for treatment of neuroendocrine tumours where there is a good expression of somatostatin receptors. In this work, MCNPS/X computer software and ORNL human phantoms were used to calculate absorbed dose due to 90Y labelled DOTATOC in the peptide receptor radionuclide therapy. Tumour was considered as a sources of beta radiation and represented as a sphere with diameter of 1-4 cm and 5 cm in liver, pancreas, and lungs. Results are expressed as absorbed dose per unit of cumulated activity, S value in units mGy.(MBq.s)(-1). The far largest dose is in tumour itself, then in organ which contains the tumour. Doses in other organs, where the metastasis are the most frequent, due to the bremsstrahlung radiation, are much smaller and could be neglected. The largest dose; 8.66.10(-3) mGy-(MBq.s)(-1) was obtained for tumour with size of 3 cm.