Imaging performance of a terbium-doped fiber optic screen for diagnostic imaging

The resolution of a fiberoptical boule was determined experimentally. A boule is a matrix of scintillating glass fibers arranged parallel to each other and compressed into a thick plate. A 51 mm × 51 mm by 3 mm thick terbium-activated boule was optically coupled to a 1 k × 1 k × 16 bit CCD camera. The image of an edge was used to compute the line spread function, and the modulation transfer function was calculated. After correcting for the MTF of the CCD and optics, the MTF of the fiberoptical plate demonstrated 20% modulation at a spatial resolution of 15 line pairs per millimeter. The x-ray absorption of the 3 mm thick plate was 98% at 70 kV (3.3. mm half value layer). It is shown using simple trigonometry that for a very high resolution detector, x-ray beam divergence (angled photons striking the receptor) at the periphery of the field of view may cause substantial resolution losses. The role that fiberoptical plate technology may play in diagnostic medical imaging is discussed.