Experimental optimization of detector pixel size for stent visualization in X-ray fluoroscopy

To visualize small interventional device such as stent in angiographic x-ray fluoroscopy, detector pixels must be sufficiently small to limit contrast dilution for partial-area effects. However, X-ray photon number per pixel and pixel signal-to-noise ratio (SNR) are decreasing with the smaller pixels. There must be a size in between with improved visualization. Using quantitative experimental and modeling techniques, we determined the optimal pixel sizes for visualization of a stent 50 μm in wire diameter for different detector types. With regard to detecting the presence of a stent, with an idealized direct detector, the 100 μm pixel size resulted in maximum measured contrast sensitivity. For the idealized indirect detector, optimal pixel size reaches at 200 μm pixel size. With regard to stent deployment, the target is smaller, and the result is more sensitive to pixel size, resulting in a steeper drop in performance with large pixels. We also applied a spatial-temporal channelized human observer model to predict and fit to the experiment results.