Tungsten alloy pinhole collimator is widely used in gamma camera for medical diagnosis. Wherein, tungsten alloy is a new type of environmentally friendly radiation shielding material that has better shielding capacity than poisonous lead to protect doctors and patients from radiation pollution.
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It has been reported that the conventional knife-edge collimator is not suitable for nuclear imaging system because many scattering radiations near the pinhole aperture happen and blur image. So, the researchers introduced a new pinhole collimator, which shapes a channeled aperture for reducing image degradation induced by the scattering radiations, and analyzed its characteristics by Monte Carlo simulation. Resolutions defined as the full-width at half-maximum of the point spread ding and efficiencies are calculated about several pinhole diameters from 4 to 8 mm and channel heights from 2 to 10 mm. For this calculation, the researchers assumed that 137Cs radiation sources with 662 keV mono-energies enter into the designed collimator at the 1 m distance from the detector plane. The efficiencies and resolutions of the channeled collimator are compared with those of the conventional collimator. By comparison results, it is verified that the new collimator takes advantage more than the conventional collimator. The optimum channel height and diameter of the pinhole collimator from simulation results are also proposed and designed.
