| A new class of small area, high resolution imaging devices was developed investigating novel concepts for in situ functional nuclear emission imaging to facilitate surgical localization and identification of residual radiolabeled tumor deposits. These are flexible, hand-held devices which can fit into small cavities necessitated by minimally invasive surgical techniques yet still produce images of clinical value for the surgeon. Several detector concepts based on imaging scintillators coupled through optical fibers to discretized, multichannel photomultipliers were investigated. The devices are sensitive either to beta particles or gamma rays or both. Each detector class was investigated, characterized and optimized by rigorous Monte Carlo simulations and measurements.; Prototype devices were developed and evaluated. The beta sensitive device utilizes a thin, continuous scintillator of europium doped calcium fluoride, optimized for high resolution imaging of {dollar}<{dollar}1 MeV beta particles. In addition, a new, fast binary organic scintillator was investigated and optimized. The gamma sensitive devices, optimized for 140 keV gamma rays, consisted of high stopping power scintillators of either small discretized elements, or continuous crystal disks. These detectors were coupled to the optical fibers in three ways: discrete, one-to-one coupling; discrete, light sharing coupling; and continuous, light sharing coupling. Sodium doped cesium iodide yielded the best results in terms of energy and spatial resolution, and efficiency. Finally, dual purpose phoswich probes were also developed and characterized, in order to simultaneously validate positron events and eliminate gamma backgrounds resulting from ambient annihilation backgrounds. This novel imaging phoswich combines the individual beta and gamma detector concepts, where two dimensional images of positron distributions are made in the first imaging detector, and validation of the event occurs in the secondary phoswich detectors which simultaneously act as a light guide for the imaging scintillator. In addition to the scintillator based imaging detectors, high resolution and sensitivity semiconductor detectors employing mercuric iodide were also investigated in multi-element array systems. These devices demonstrated superior performance characteristics for gamma ray imaging than their fiber optically coupled counterparts. |
