Development of high resolution modular four side buttable small field of view detectors for three dimensional gamma imaging

Objectives: Objectives of this work are to present challenges faced in bringing innovative medical imaging scanners for single photon emission computed tomography (SPECT) to the market. This market has seen innovation in scanner designs based on room temperature semiconductor detectors (RTSD), albeit widespread acceptance has been slow to none. Our objectives are: 1] Dissect typical RTSD based SPECT scanner design2] Uncover technological bottlenecks in bringing innovation to market3] Provide solutions to most of these bottlenecks.

Methods: We present a modular design approach as shown in the figure. The main components of the module are: SPECT Application Specific Integrated Circuit (SPECTASIC) [1] substrates vertically mounted using edge connectors to the Cadmium Zinc Telluride (CZT) substrate. These high-density PCBs and interconnects allow us to increase pixel resolution better than the state of the art of 2.5 mm [2]. We are using Analog to Digital Converter (ADC) substrate and the Field Programmable Gate Array (FPGA) and power board connected using board connectors which sends the data to the wifi or wired connector for the image reconstruction. Typically a SPECT scanner has at its core, gamma detector. These detectors conventionally use scintillators which convert gammas into optical photons. Optical photons are then detected by photosensors such as Photo Multiplier Tube (PMT) or Silicon PMT. This method is proven but highly dose inefficient. Recently, we've seen many vendors offering RTSD based scanners. Most of these scanners use proprietary technologies and are not typically cost-effective and quality-aware at the same time. A compromise needs to be made to achieve one over the other. Our approach leverages the economy of scales found in the semiconductor/electronics industry [3]. Having one geometry of the readout modules which can be mass-produced and be made available to different vendors, while they enjoy the protection of the intellectual properties generated within the scanner geometries and reconstruction methods, creates a win-win situation for the imaging vendors as well as streamlines the supply chain.

Results: Our preliminary results show a position resolution between 0.8 mm - 0.5 mm. This is a significant improvement over the state of the art [2] if not an order of magnitude. We achieve this while maintaining a fill factor of close to 100% with an ability to abut detectors to create large-area 2-dimensional arrays without any dead space. The SPECT ASIC has reported 2% FWHM energy resolution at 662 KeV without correction with CZT detectors [1]. Mass production of these SPECTASIC modules is our next step and we are looking for a platform to showcase this approach so that widespread community adopts it to bring a revolution in SPECT market place.

Conclusions: We believe our detectors can fuel new concepts and geometries of the scanners to target various markets including the cost and quality sensitive as well as developing markets such as North America, Asia, South America. We believe that our approach is novel and will start a revolution in medical imaging that's long due.

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