Design of a new Compton Camera by Monte Carlo method and assessment its important parameters affecting image quality

Abstract

In nuclear medicine imaging systems such as Gamma camera and SPECT, currently uses a mechanical collimator and a scintillation detector to detect distribution of gamma emitter radiopharmaceuticals. The detection technique, however, suffers from spatial resolution and sensitivity trade-off because of mechanical collimation. Compton camera principle is a suggested alternative which avoids the mentioned trade-off. Compton camera consists of one scattering detector and one absorber detector. Compton scattering of emitted photons from the source is detected in a special scattering detector which replaces the mechanical collimator. This research study simulated a Compton camera which is composed of a “Si” scattering detector (dimensions: 22.4 × 22.4 × 14 mm3) in a distance of “D” from an absorber detector (NaI(Tl), dimensions: 20 × 20 × 1 cm3). To evaluate the image quality of the designed Compton camera in different and inside the spread range of energies which uses for nuclear medicine studies, the point sources of Tc-99m (140 keV), I-131 (364.4 keV) and C-11 (511 keV) are assumed to be located in the front of the scattering detector and in the distance of “h= 10 mm” from it, and important parameters which affects on image quality, were calculated, analyzed and the best thickness for scattering detector were found. The thickness of absorber detector was assumed 10 mm which is about the thickness of detectors in SPECT systems. This study modeled the Compton camera realistically with all the details of the Compton camera such as Doppler broadening. Our results showed the spatial resolution would improve while the sensitivity would decrease by increasing the distance between scattering and absorber “D”. Also the optimum “D = 20 cm” at “h=1 cm” were found. Furthermore our results showed by increasing the photo peak energy of isotope the spatial resolution and sensitivity would improve significantly.KeywordsCompton CameraDiagnostic imagingNuclear medicineEmission imaging