Uptake, localization, and dosimetry of 111in and 201tl in human testes.

UNLABELLED

This study concerns the testicular uptake and dosimetry of Auger electron-emitting radionuclides that are used during routine diagnostic nuclear medicine procedures. To consider the possible effects of these radionuclides on spermatogenic cells, a study has been undertaken to obtain in vivo data for quantification of (111)In chloride and (201)Tl chloride uptake into the human testis after intravenous administration. Values have been determined for uptake into the testis as a whole and to the seminiferous tubules where the germ cells are located.

METHODS

Data were obtained from patients with prostate cancer who opted for orchidectomy to effect hormone suppression. Patients were administered intravenously 1.5 MBq of either (111)In chloride or (201)Tl chloride at 24 or 48 h before orchidectomy. Upon removal, the testes were analyzed to assess uptake of radionuclide. Conventional dosimetry has been used to estimate testicular radiation doses using our values of percentage uptake.

RESULTS

Uptake of both (111)In chloride and (201)Tl chloride into the testes was seen at a level above that explained by simple homogeneous distribution of the radionuclide throughout the body; the testes as a whole demonstrated increased uptake by factors of 3.56 and 4.01 compared with nonspecific uptake for (111)In and (201)Tl, respectively, at 24 h after administration. Both radionuclides gained access to the seminiferous tubules.

CONCLUSION

The results obtained indicate that the values of testicular radiation doses quoted by the International Commission on Radiological Protection for (111)In might be too low by a factor of 4, whereas those for (201)Tl might be too high by a factor of 4. No data were obtained for uptake by individual germ cells within the testis and, therefore, no consideration of dosimetry at the cellular level was possible. However, it has been demonstrated that uptake of diagnostic Auger electron-emitting radionuclides by male germ cells within the testis is possible after intravenous administration.