INVESTIGATION OF CRYSTAL GEOMETRIES FOR FIBER-COUPLED GAMMA-IMAGING INTRAOPERATIVE PROBES

CsI(Na), CsI(Tl) and NaI(Tl) scintillators coupled through optical fib ers were investigated with simulations and measurements to evaluate th eir potential as gamma imaging intraoperative probes. Three coupling m ethods were employed: discrete crystals coupled one-to-one with the fi bers; discrete crystals coupled through a light diffuser to an unmatch ed fiber array; and continuous crystals coupled directly to the fiber optic array. The discrete crystals were 4x4 element arrays ranging in size from 1x1x2.5 mm(3) to 2x2x6 mm(3). CsI(Na) produced the best puls e height and single crystal energy resolution (44% at 140 keV) when co upled through fibers to the photodetector. All elements of the arrays were completely resolved, indicating that the intrinsic spatial resolu tion will be determined by the crystal size. The spatial resolution fo r the 12.5 mm phi x 3.5 mm continuous crystals was similar to 1.33 mm FWHM. Preliminary imaging measurements faithfully reproduced the activ ity distributions and compared favorably with simulations.