Monte carlo simulation on the 4π field of a view compact compton camera by using scintillators

A compact LaCl₃(Ce) Compton camera with a 4π field of view (FOV) was introduced, and the optimized design parameters with the effective choice of the γ-ray interaction order were obtained by using Monte Carlo simulation. The camera consisted of six LaCl₃(Ce) planar scintillators with pixelized structure, which could be coupled with position sensitive photomultiplier tubes. Since γrays were incident from all direction (4π), all of the scintillators were both scattering and absorbing detectors for Compton image reconstruction, and the interaction sequence was decided based on the deposited energy. According to the simulation results, the reconstructed image showed better angular resolution and smaller variance for all incident radiation energies (300 keV ∼ 2 MeV) when the energy of the scattering interaction was assumed to be smaller than that of the absorbing interaction. The optimum thickness of the scintillators to maintain high image resolution and large sensitivity was 1 ∼ 1.5 cm, and the difference between the center of the camera and the scintillators was set to 7 cm to minimize degradation of image resolution and the loss of detection efficiency. With the optimized conditions, the effect of each parameter causing blurring and variance was estimated. At low energy, the finite energy resolution was the main factor increasing the uncertainties of the reconstructed image. However, at high energy, the pixelization effect and the incorrect choice of interaction sequences also were significant factors in the degraded angular resolution and relative standard deviation of the reconstructed image.