Investigation of crystal geometries for fiber coupled gamma imaging intra-operative probes

In this work, gamma sensitive intra-operative imaging detectors using CsI(Na), CsI(Tl) and NaI(Tl) scintillators coupled through optical fibers were investigated with simulations and measurements. Three coupling methods were employed between the detectors and optical fiber imaging array: discrete crystals coupled one-to-one with the fibers; discrete crystals coupled through a light diffuser to an unmatched fiber array; and continuous, light sharing crystals coupled directly to the fiber optic array. The discrete crystals were arranged in 4/spl times/4 element arrays of sizes ranging from 1/spl times/1/spl times/2.5 mm/sup 3/ up to 2/spl times/2/spl times/6 mm/sup 3/. CsI(Na) had the best pulse height and single crystal energy resolution (44% at 140 keV) when coupled through fibers to the MC-PMT photodetector. All discrete arrays were completely resolved, indicating that the intrinsic spatial resolution corresponded to the crystal size. The spatial resolution for the 12.5 mm /spl phi//spl times/3.5 mm continuous crystals was /spl sim/1.2 mm FWHM, with relative pulse heights of 1.5 to 5.5 times lower than for the discrete array detectors.