Calibration of the axial spatial resolution of the xRAI system. (a) Experimental setup for quantifying the axial spatial resolution of the xRAI system by imaging a lead block. (b) xRAI image of the lead block. The red square marks the front side of the block. (c) Normalized pixel intensities along the yellow dashed line in xRAI image in (b). The fitting curve shows the line spread function with a FWHM of 1.1 mm.