In vitro irradiation of blood with Tc-99m: Evaluation of dose and chromosome aberrations in irradiated lymphocytes

The use of ionizing radiation for diagnostic or therapeutic purposes in med icine represents the principal sourer of artificial radiation to humans. Ca lculation of radiation dose is essential to the analysis of risks (biologic al effects) and benefits in any application, including nuclear medicine. Th e: dose assessment in many cases is not necessarily straightforward. Many r adiopharmaceuticals are labelled with radionuclides that undergo not only g amma -emission but also emission of Auger and internal conversion electrons . A typical example is technetium-99m (Tc-99m), which is used in more than 80% of nuclear medicine applications. In this work, in vitro studies have b een carried out to evaluate the dose delivered to lymphocytes by human seru m albumin microspheres (HSAM) labelled with Tc-99m. Experiments were perfor med in order to score unstable chromosomal aberrations induced by Tc-99m-HS AM, using conventional cytogenetic techniques. Henceforth, the relationship between activities introduced into blood samples and induced chromosomal a berrations were evaluated. To assess the dose absorbed in lymphocytes, elec tron and photon transport was performed in a simple model representing the system used for irradiating the cells using the: MCNP Monte Carlo code. In this report, analysis of dose-effect curve demonstrates a linear quadratic response for unstable chromosome aberrations.