DE-FG02-04ER84058 Final Report

The goal of the Phase I research was to demonstrate the feasibility of developing a high performance SPECT/CT detector module based on a combination of microcolumnar CsI(Tl) scintillator coupled to an EMCCD readout. We are very pleased to report that our Phase I research has demonstrated the technical feasibility of our approach with a very high degree of success. Specifically, we were able to implement a back-thinned EMCCD with a fiberoptic window which was successfully used to demonstrate the feasibility of near simultaneous radionuclide/CT using the proposed concept. Although significantly limited in imaging area (24 x 24 mm{sup 2}) and pixel resolution (512 x 512), this prototype has shown exceptional capabilities such as a single optical photon sensitivity, very low noise, an intrinsic resolution of 64 {micro}m for radionuclide imaging, and a resolution in excess of 10 lp/mm for x-ray imaging. Furthermore, the combination of newly developed, thick, microcolumnar CsI and an EMCCD has shown to be capable of operating in a photon counting mode, and that the position and energy information obtained from these data can be used to improve resolution in radionuclide imaging. Finally, the prototype system has successfully been employed for near simultaneous SPECT/CT imaging using both, {sup 125}I and {sup 99m}Tc radioisotopes. The tomographic reconstruction data obtained using a mouse heart phantom and other phantoms clearly demonstrate the feasibility and efficacy of the detector in small animal research. The following were the objectives specified in the Phase I proposal: (1) In consultation with Professor Hasegawa, develop specifications for the Phase I/Phase II prototype detector; (2) Modify current vapor deposition protocols to fabricate {approx}2 mm thick microcolumnar CsI(Tl) scintillators with excellent columnar structure, high light yield, and high spatial resolution; (3) Perform detailed characterization of the film morphology, light output, and spatial resolution, and use these data to refine deposition protocols; (4) Develop suitable designs of a collimator to be fabricated during the Phase II; (5) Integrate thick CsI(Tl) films into the existing IGCCD camera to form a prototype dual-imaging detector module; (6) Conduct evaluation of the prototype SPECT/CT detector to determine its suitability for x-ray CT and radionuclide imaging; and (7) Write the Phase I final report and prepare the Phase II research plan. Our work in Phase I has not only accomplished all the above stated goals, but has surpassed them in many aspects. The data presented in the report below show that the proposed combined detector will not only minimize the complexity and cost associated with conventional readouts, but will also improve system reliability necessary for the development of a dual modality system. This is a substantial accomplishment, which brings us a step closer to our Phase II goal of developing a much larger area, higher pixel resolution detector and minimizes risk associated with implementation of the proposed design