EGS5 simulations for the development of non-contacting system to online measure the radiotracer concentration in blood

Quantitative Positron Emission Tomography (PET) studies require the blood sampling which is very inconvenient and painful for the patients, handling of radioactive samples is risky to the workers and lengthy as well as less efficient to the imaging centers. Various approaches are proposed to reduce the exposure to the workers and number of blood samples to comfort the patients but no one fulfills all the requirements. We are designing a non-contacting system which can in-situ measure the radiotracer concentration in the blood and hence, provide Plasma Time-Activity Curve (PTAC). As a first step we consider a conventional system used to measure the dose in Nuclear Power Plant Systems (NPPS) with High Purity Germanium (HPGe) detector and a small animal PET system with Lutetium Aluminum Garnet with Avalanche Photo Diodes (LuAG-APD) pixelated detector blocks. Monte Carlo Electron Gamma Shower (EGS) 5 simulation tool is used to analyze the suitability of the systems and results are presented for a conventional parallel disc-detector system, a proposed perpendicular disc-detector system and a LuAG-APD animal PET tomograph. Although the conventional NPPS dose measurement system has the advantage of on-site measurement and best energy resolution but suffers from low detection efficiency and cannot be used in our case. However, the LuAG based PET tomograph with high detection efficiency, good spatial resolution, acceptable energy resolution and flexible arrangement to increase detection efficiency seems to be a more appropriate candidate.