Hideaki Wakamatsu

Improved computed radiography image quality from a BaFI:Eu photostimulable phosphor plate

Recent advances in the design of photostimulable phosphor (PSP) plates for computed radiography (CR) systems have made it possible to manufacture plates made of BaFI:Eu phosphor material in the cassette form. The image quality of this plate, six BaF(Br,I):Eu plates, and one BaFBr:Eu plate were evaluated in terms of presampling modulation transfer function (MTF), normalized Wiener spectra (WSN), and detective quantum efficiency (DQE). Compared with the best-performing BaF(Br,I):Eu plate, the BaFI:Eu plate provided DQE that was higher, at spatial frequencies of 0.5, 1.0, and 2.0 cycles/mm, by 12% (21.8 versus 19.4), 13% (18.8 versus 16.7), and 11% (12.0 versus 10.8), respectively. Since presampling MTF values of the two plates were comparable, the BaFI:Eu plates higher DQE is attributable to total WSN conversely being lower by 17% [8.65 x 10(-5) (mm2) versus 10.38 x 10(-5) (mm2)], 17% [5.85 x 10(-5) (mm2) versus 7.03 x 10(-5) (mm2)], and 12% [2.82 x 10(-5) (mm2) versus 3.19 x 10(-5) (mm2)] at the specified frequencies, respectively, primarily due to the contribution of x-ray quantum WSN. This jibes with the high x-ray absorption provided by the 27%-higher x-ray attenuation coefficients (7.54 versus 6.07, at 60 KeV) that BaFI offers over BaF(Br(0.85),I(0.15)), a result of the high atomic number of BaFIs exclusively iodine halide content. The results were consistent with earlier studies of several of these same plates and indicate that BaFI:Eu is a promising avenue to lower image noise and higher overall CR system image quality.