Development and characterization of a handheld radiation detector for radio-guided surgery

The current state-of-the-art breast surgery uses radioactive brachytherapy sources to indicate the center of the tumor and possibly a few points on the periphery as seen on mammography. Since such guidance is very coarse, tumor free margins are not achievable in many cases and a re-excision procedure is often required. Better radiation guidance (radio-guidance) could come from labelling cancer cells directly with a radionuclide, such as the agent CLR1404. The agent CLR1404 is taken up by breast cancer cells but not normal cells and, labelled with radioactive I-123, could image the whole tumor, not just points. Tc-99m-labelled nanoparticles are used to locate sentinel lymph nodes. Simultaneous detection and differentiation of the photon energies 159 keV from I-123 and 141 keV from Tc-99m requires a radiation detector with high energy resolution and sufficient efficiency. This report involves the design, development and characterization of such a handheld radiation detector. Following the design and integration of the detector, the main characteristics of the detector, such as energy resolution, photopeak efficiency and response at different source-to-detector distances were investigated experimentally. Energy resolution of the detector was found to be less than 10 keV (FWHM) at energies below 159 keV, which allowed discerning the radiation from the two radionuclides. Energy spectra of the radioactive sources acquired experimentally were compared to those simulated in Monte Carlo N-Particle Transport Code (MCNP6X). The detector developed was found to be promising for radiation-guided surgery applications.