Development and evaluation of a new radiographic and fluoroscopic imager based on electron-multiplying CCDs: The solid state x-ray image intensifier

A new dual detector system was developed which utilizes a low resolution, large field-of-view x-ray image intensifier (II) and a high resolution, region-of-interest microangiographic (MA) detector on the same c-arm gantry. With this new MA-II system, the larger field-of-view (FOV) II can be operated when the demands of the task are not as high, and a larger imaging area is desired. However, when a higher-resolution image with greater image quality is desired at a targeted region-of-interest (ROI), the MA can be deployed to take on these greater demands. To quantitatively and qualitatively assess the imaging performance of each detector under realistic conditions, angiographic images of simulated vessels and rabbit neurovasculature were acquired with both detectors under nearly identical conditions. With the MA detector deployed, vessels as small as 95 mum were visible, whereas the II could not detect vessels smaller than 235 mum. The ROI MA mode was also shown to provide sharper images with higher contrast-to-noise ratios and was four times as likely to successfully detect overlapping vessels as compared to the II. More accurate three-dimensional center lines of vasculature using multi-view reconstruction techniques were also obtained with the MA.;The solid state x-ray image intensifier (SSXII) was developed to provide similar high-resolution imaging capabilities as the MA and a built in adjustable gain to provide high-sensitivity imaging capabilities for operation at all exposures used in medical x-ray imaging procedures. The imaging components used in construction of the prototype SSXII were selected based on a theoretical performance evaluation, using a Fourier-based linear-systems model analysis. The performance of the prototype SSXII was then extensively evaluated. Images of various objects and image comparisons with current state-of-the-art detectors qualitatively demonstrated that the SSXII is capable of providing substantial improvements. A quantitative assessment of spatial resolution, noise performance, and overall performance was then determined using MTF, INEE, and DQE measurements. In addition to the overall performance of the SSXII, the performances of individual components were determined using measurements of their resolution and transmission efficiency. The unique ability of the SSXII to operate in both tradition energy integrating (EI) mode and single photon counting (SPC) mode was also demonstrated.;To better assess detector performance, a new method for determination of the two-dimensional presampled MTF, the "noise-response method", was developed and evaluated. Compared to current measurement methods, the noise-response method simplifies the MTF determination by eliminating the need for manufacture and alignment of precisely machined test objects, thereby eliminating inaccuracies that result from the use of such objects and subsequent analysis of the resulting images. The accuracy of this method was demonstrated using both simulated and experimental data sets. For the simulated image set which used a simple detector model for which the "true" MTF was known exactly, excellent agreement was obtained with the MTF determined using the noise-response method, with a maximum deviation of 1.1%. Comparison measurements were also made on this simulated data set with the established edge-response method and these showed deviations greater than 35% from the "true" MTF. Experimental measurements on a range of detector technologies (including an XII, FPD and SSXII) demonstrated agreement between the noise-response and edge-response methods within experimental uncertainty, with discrepancies likely resulting from errors inherent in the edge-response MTF procedure. The two-dimensional MTF for the FPD was non-isotropic, with an increase observed on the diagonals, whereas the SSXII MTF was shown to be largely symmetric. Initial results indicate that the new noise-response method is a promising candidate to replace existing standard methods.;To further assess detector performance, the instrumentation noise equivalent exposure (INEE) metric has been developed to address the need for a direct, quantitative measure of the quantum-noise-limited exposure range of x-ray detectors by providing the threshold exposure at which the detector instrumentation-noise exceeds the quantum-noise. Frequency dependence and all instrumentation noise sources were investigated to provide a greater understanding of this promising new metric and to ensure quantum noise limited operation at every spatial frequency of interest. Measurements were done on various x-ray detectors to demonstrate the usefulness of these new developments. In addition to providing a practical quantification of instrumentation noise, the INEE was also shown to provide insight into overall detector performance in terms of the behavior of the DQE as a function of exposure. (Abstract shortened by UMI.)...