2001 Volume 57 Issue 5 Pages 559-564
We proposed a method for practical estimation of the presampling modulation transfer function(MTF) of a computed radiography (CR) system by using the MTFs of an imaging plate and the sampling aperture. TheMTFs of three imaging plates (GP-25,ST-VN, and RP-1S)with different photostimulable phosphors weremeasured by using direct fluorescence (the light emitted instantaneously by x-ray exposure), and the presamplingMTFs were estimated from these imaging plate MTFs and the sampling aperture MTF. Our results indicated that for imaging plate RP-1S the measured presampling MTF was significantly superior to the estimated presampling MTF at any spatial frequency. This was because the estimated presampling MTF wasdegraded by the diffusion of direct fluorescence in the protective layer of the imaging plate's surface. Therefore, when the presampling MTF of the imaging plate with a thick protective layer is estimated, correction forthe thickness of the protective layer should be carried out. However, the estimated presampling MTF of imaging plates with a thin protective layer were almost the same as the measured presampling MTF, except in the high spatial frequency range. Therefore, we consider this estimation method to be useful and practical, because the spatial resolution property of a CR system can be obtained simply from the imaging plate MTF measured with direct fluorescence.
