Abstract

In gamma camera and single-photon emission computerized tomography, the collimator removes most photons. Here, a gamma camera without collimator utilizes a specific arrangement of detectors. Instead of bending beams (like a lens) or directing beams (by parallel hole collimator), changes are created in detectors' field of view (FOV), so that each detector's FOV looks different from others. Simulation proved this theory, with 98 detectors (2 cm x 1.41 cm) arranged in a zigzag manner for Monte Carlo simulation. A radioactive source with energy of 140 keV was situated on the detectors' faces. Sixty projections, each 3 degrees (0 degrees-17 degrees) apart, were simulated by Monte Carlo N-Particle (MCNP) 4C code, rotating detectors around a radioactive point. The band containing the radioactive source is clearly visible in each projection. Counts obtained after simulation in different projections were reconstructed, and point source location emerged correctly. Simulation of gamma camera with zigzag arrangement of detectors and MCNP-4C code demonstrated that one could string the space and determine radioactive source by image reconstruction without using collimators, solely through these special detectors' distribution.