APPLICATION OF MONTE CARLO CALCULATION FOR THE VIRTUAL CALIBRATION OF A LOW-ENERGY IN VIVO COUNTING SYSTEM
N. Pierrat, L. de Carlan, D. Cavadore, D. Franck, IEEE Medical Imaging conference, 19-22/10/2004, Rome (Italy).
Internal dosimetry can be derived from the assessment of retained activity in the body at a given time. In radiation protection, this assessment is performed using dedicated counting systems. The calibration of these systems (generally based on NaI or HPGe detectors) is ensured by anthropomorphic phantoms which can only provide rough representations of human tissue generating substantial corrections on calibration factors. These corrections are particularly crucial in lung measurement because of the absorption in tissue.
In order to improve calibration, numerical phantoms associated with Monte Carlo codes have already proved their benefit. In this goal, a Graphical User Interface called OEDIPE was developed in the laboratory, allowing to simulate measurement process using all measurement parameters, and was already validated for a one-germanium detector system. The system of COGEMA Marcoule is composed of four-germanium detectors, the most widespread configuration. The modelisation of this system and the validation of this model with different measurement configurations are presented in this paper. The validation of this model was realized with point sources and the Livermore calibration phantom. The final goal is to approach a personalized numerical calibration of the facilities to improve dose assessment. Such application could be an opening door on a better activity assessment in nuclear medicine, especially in personalized dosimetry in radioimmunotherapy.