Optimization of detector pixel size for interventional x-ray fluoroscopy

Visualization of guide-wires and stents is of great interest in x-ray fluoroscopy. Detector pixels need to be small to limit partial-area effects with pixel-thin guide-wires. However, as pixels become smaller, the number of x-ray photons per pixel and the pixel signal-to-noise-ratio (SNR) decrease. Hence, there is a trade-off between resolution and SNR that will affect visualization. For imaging interventional devices, we determined the optimum detector pixel size using human observer detection experiments and modeling. Contrast sensitivities for guide-wire detection were determined for an idealized digital detector with pixels of 100, 200, 300 and 500 mum and for a guide-wire diameter of 400 mum. Results indicate that the optimal pixel size is around 200 gm at fluoroscopic exposures. At higher exposures, a smaller detector pixel is desirable. With large pixels, detection was degraded significantly due to contrast-dilution from partial-area effects. A human observer model predicted results, Having established the model for an idealized situation, we then use it to predict the effect of physical detector parameters like MTF, NPS and fill-factor on image quality. The model is a very promising tool for designing detectors for dose-efficient x-ray systems.