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 ( WS N ), 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 plate’s higher DQE is attributable to total WS N conversely being lower by 17% [8.65×10 −5 ( mm 2 ) versus 10.38×10 −5 ( mm 2 )], 17% [5.85×10 −5 ( mm 2 ) versus 7.03×10 −5 ( mm 2 )], and 12% [2.82×10 −5 ( mm 2 ) versus 3.19×10 −5 ( mm 2 )] at the specified frequencies, respectively, primarily due to the contribution of x-ray quantum WS N . 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 BaFI’s 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.