Investigation of the optimal design parameters of a bar detector for nuclear medicine applications

This study examined the optimal design parameters for a bar detector that allows 3-dimensional position decoding of impinging gamma rays. Simulation studies were carried out to determine the optimum design parameters of a bar detector. Experimental measurements were carried out to validate the simulation. The bar detector simulator consisted of a long scintillation crystal, ranging in size from 5 cm to 20 cm and with a relatively small cross section (4×4 mm²), that was coupled to two photo sensors, one on each end. A statistics-based positioning (SBP) scheme was used to improve the positioning accuracy. This method mapped the event characterization vectors to the associated position based on the chi-square error. The simulation showed that a 5-cm-, 10-cm-, and 20-cm-long NaI(Tl) bar detector could achieve a full width at half maximum(FWHM) spatial resolution of 0.9 mm, 1.7 mm and 3.3 mm for 511 keV gamma photons, respectively. There was approximately a 20% improvement in the performance of the SBP scheme over the conventional linear estimate. The simulation also showed that the grounded surface treatment was important for providing optimum performance with respect to the spatial resolution and spatial uniformity. For the experimental studies, average spatial resolutions of 3.0 mm and 8.5 mm FWHM, were achieved for the 5-cm- and 10-cm-long CsI(Na) bar scintillators with a ⁵⁷Co source, respectively. This investigation demonstrated that the proposed bar detector could be used as a gamma-ray imaging detector, particularly for PET applications in the field of nuclear medicine, with many advantages over conventional detector configurations.