The long-term objective is to develop the new Solid State X-ray Image Intensifier (SSXII) into the preferred dynamic x-ray imaging device with clear advantages over flat-panel devices (FPD) and x-ray image intensifiers (XII). These advantages include higher spatial resolution with smaller pixels, lower instrumentation noise hence better operation at lower exposure, huge dynamic range due to adjustable on-chip gain, no lag, no ghosting, and scalable production based on existing solid state technology. The SSXII consists of an array of modules each with a fiber optic taper that focuses light from a structured phosphor x-ray converter such as CsI(Tl) onto an electron multiplying charge coupled device (EMCCD). EMCCDs are relatively new sensors that have all the benefits of standard CCDs (high resolution, high speed, low noise, no lag) with the addition of on-chip gain created by an extra row of hundreds of special multiplying elements. Adjustment of a low voltage (tens of volts) applied to these electron multiplying elements provides on-chip gains from 1 to greater than 1000X.
The specific aims for the project include development of prototype detectors made of arrays of EMCCD-based modules. A 2x2 system made of commercial EMCCD-based cameras will enable early testing over a limited field of view (FOV). The larger 3x3 array built from components because of its modularity will demonstrate a design that is extensible to full clinical FOVs and may completely replace the functions of XIIs or FPDs but with additional benefits of higher resolution and lower dose operation. For the evaluation of these new array detectors, we will obtain quantitative physical characterizations using linear systems analysis and, using patient specific rapid-prototyped phantoms, we will simulate complete interventions. An operator-friendly LabVIEW-software-based graphics user interface will provide control over the SSXII during fluoroscopy with roadmapping and angiography acquisitions. We will also evaluate the prototype SSXIIs in animal models to explore the wide variety of potential applications prior to planning for initial human studies. Applications we will begin to study are to neuro- and cardio-vascular procedures such as endovascular image guided interventions (EIGI) for treating aneurysms and stenotic vessels deep in the cranial vasculature, diagnosis and treatment of coronary chronic total occlusion (CTO) as well as investigations of possible applications to anti-angiogenic tumor treatment. Additional new modalities involving region of interest (ROI) fluoroscopy, angiography, and cone beam computed tomography (CBCT), where the unique high resolution capabilities of the SSXII can be used while maintaining lower integral dose to the patient, will also be explored. Possible applications in addition to EIGI procedures include mammographic CT and tomosynthesis and other imaging where the low noise characteristics of the SSXII will enable increased number of lower dose views to reduce reconstruction artifacts. In summary, the proposed new SSXII once developed may become the future dynamic x-ray detector of choice with higher resolution and lower exposure operation than is possible with current FPDs or XIIs.
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