SBIR-STTR Award

A dual plane Compton imager prototype system with large volume pixelated CZT detectors will be built for spectrally resolved MeV gamma ray tomographic applications. These two planes will be operated at independent clocks and they will be synchronized via a common periodical pulse. The common periodical pulse is self-generated so it does not rely on external pulse generator. Each detector will be coupled with an application specific integrated circuit (ASIC). The ASIC will convert the gamma ray energy detected by the CZT detectors to a voltage signal. An in-house developed readout and processing electronics will translate the voltage signal to corresponding location and energy deposition information of each gamma ray interaction. This information will be used by 3D Compton imaging reconstruction algorithm to create a 3D map of the material of interest inside the under-test object. In order to achieve the best imaging performance for this application, various detector position configurations and reconstruction algorithms will be evaluated. The final prototype system with optimal reconstruction algorithm will be tested by resolving phantoms with different hydrogen mass concentration.

Phase I has proven that the current setup achieves better than 8mm spatial resolution for 2.2MeV prompt gammas. However, 1mm spatial resolution presents a significant challenge for the current setup due in part to limited timing resolution and count rate. A new analog ASIC will be developed to replace the current analog ASIC that will have better timing resolution and deliver higher count rates. In addition, the dynamic range of the new analog ASIC will increase to 9MeV to measure prompt gammas from elements other than hydrogen. In parallel to the analog ASIC development, a dual plane hybrid Compton camera will be built with our existing digital ASIC. This ASIC has similar timing resolution and dynamic range to the new analog ASIC but operates at lower count rates. It will serve as a testbed for high-energy gamma imaging studies during Phase II. The goal of these studies is to identify and approach the limits of spatial resolution for our dual plane imager by optimizing both the imager design and source-detector configuration. The final goal is to achieve 1 mm spatial resolution at 2.2MeV with 1% H concentration in 3 dimensions.