Investigation of micro-columnar scintillators on an optical fiber coupled compact imaging system

A compact imaging system with a novel front-end detector is under investigation and development. Unique aspects of this collimator-less system include the use of many thousands of micro-columnar (<10 /spl mu/m diameter) CsI front-end scintillators (140 and 200 microns tall on faceplates of plane glass, fiber optics (FO), and FO with statistical extramural absorbers (EMA)) that are coupled through a 4 times reducing FO bundle to a metal-channel multianode position sensitive photodetector. The highly discrete nature of the scintillator microcolumn arrays ensures very fine intrinsic spatial resolution, limited by the particle penetration and backscatter in the detector assembly, while their retro-reflector-tipped front-ends facilitate light propagation towards the photo-detector. Monte Carlo simulations confirmed the limiting nature of particle penetration on measurable resolution. With this system, absolute light output was highest for the taller arrays, which contradicts results of using much larger, quantized scintillators in other applications. While MTF measurements with an X-ray source indicate the best response with the arrays on FO+EMA substrates, measurements with high and medium (1.7 MeV and 635 keV) energy beta line sources yield the best responses with the plane glass substrate indicating that energy thresholding affects resolution in the classical way, even with these highly miniaturized arrays. Further experiments of complex positron emission distributions along with large gamma ray backgrounds yield images with minimal background contamination and no distortions.