Testicular dose and associated risk from inverted-Y field irradiation in patients with Hodgkin's disease

This study aims to estimate testicular dose and the associated risks for infertility and hereditary effects from inverted-Y field irradiation Radiotherapy was simulated on a humanoid phantom using a 6 MV photon beam. Testicular dose was measured for various field sizes and tissue thicknesses along beam axis using an ionization chamber. Gonadal dose was reduced by placing lead cups around the testes supplemented by a field edge block. For a tumor dose of 40 Gy, testicular dose was 0.56-6.52 Gy depending upon the field size and the distance from the inferior field edge. The corresponding dose to shielded testes was 0.12-1.96 Gy. The increase of tissue thickness in reased the testicular dose up to 40%. An excess risk of hereditary disorders of (7-391) per 10000 births was calculated. The treatment parameters, the presence of gonad shield and the somatometric characteristics determine whether testicular dose can exceed 1 Gy which allows a complete recovery of spermatogenesis.