A dual-modality ultrasound-gamma system: Monte Carlo simulations of the scintillation imager

The aim of the ECORAD collaboration is to develop a dual integrated compact and portable camera able to acquire ultrasound and scintigraphic images at the same time. In this work, we present some simulated results of the scintigraphic part of the system. This camera consists of a rotating slant collimator with four segments connected to a planar LaBr3:Ce scintillator and to a PMT Hamamatsu Flat Panel H8500. Simulations are achieved by means of the GEANT4 program. The volumetric information is reconstructed from the planar images acquired at each position of the rotating collimator by means of a simple back-projection method. Results showed that the planar spatial resolution is better that the axial one. First preliminary results suggest that the detection limit of the camera is about 15:1 (in terms of Tumor/Background ratio) for a spherical tumor with 8 mm diameter located at 3 cm distance from the collimator. This confirms that with our approach it is feasible to develop a compact camera able to recover the 3D position of lesions located at small depths (up to some centimeters), without the need of rotating the camera around the body.