Measurements of X-ray Imaging Performance of Granular Phosphors With Direct-Coupled CMOS Sensors

다국어 초록 (Multilingual Abstract)

<P> For <TEX>${\hbox {Gd}}_{2}{\hbox {O}}_{2}{\hbox {S}}{:}{\hbox {Tb}}$</TEX> granular phosphor screens having a wide range of mass thicknesses, we have investigated the fundamental imaging performance in terms of modulation-transfer function (MTF), noise-power spectrum (NPS) and detective quantum efficiency (DQE). As an optical photon readout device, a CMOS photodiode array with a pitch of 48 <TEX>$\mu{\hbox {m}}$</TEX> was used. Under the representative radiation quality, RQA 5, recommended by the IEC (International Electrotechnical Commission, Report 1267), the MTF was measured using a slanted-slit method to avoid aliasing and the NPS was determined by two-dimensional (2D) Fourier analysis of white images. The DQE was assessed from the measured MTF, NPS and the estimated photon fluence. Figure-of-merit (FOM) curves are presented to describe the tradeoff between the X-ray sensitivity and spatial resolution of screens as a function of mass thickness. This study will be useful for the selection guidance of <TEX>${\hbox {Gd}}_{2}{\hbox {O}}_{2}{\hbox {S}}{:}{\hbox {Tb}}$</TEX> phosphors for the relevant imaging tasks of digital radiography. </P>