Performance characteristics of a Kodak computed radiography system

Abstract

The performance characteristics of a photostimulable phosphor based computed radiographic (CR) system were studied. The modulation transfer function (MTF), noise power spectra (NPS), and detective quantum efficiency (DQE) of the Kodak Digital Science computed radiography (CR) system (Eastman Kodak Co.-model 400) were measured and compared to previously published results of a Fuji based CR system (Philips Medical Systems-PCR model 7000). To maximize comparability, the same measurement techniques and analysis methods were used. The DQE at four exposure levels (30, 3, 0.3, 0.03 mR) and two plate types (standard and high resolution) were calculated from the NPS and MTF measurements. The NPS was determined from two-dimensional Fourier analysis of uniformly exposed plates. The presampling MTF was determined from the Fourier transform (FT) of the system's finely sampled line spread function (LSF) as produced by a narrow slit. A comparison of the slit type ("beveled edge" versus "straight edge") and its effect on the resulting MTF measurements was also performed. The results show that both systems are comparable in resolution performance. The noise power studies indicated a higher level of noise for the Kodak images (approximately 20% at the low exposure levels and 40%-70% at higher exposure levels). Within the clinically relevant exposure range (0.3-3 mR), the resulting DQE for the Kodak plates ranged between 20%-50% lower than for the corresponding Fuji plates. Measurements of the presampling MTF with the two slit types have shown that a correction factor can be applied to compensate for transmission through the relief edges.

Reproducibility of pixel values for two photostimulable phosphor plates in consecutive standardized scannings

“…A digitalization error (causing lack of reproducibility) of pixel values would be deleterious in these situations because it would attribute pixel values that differ from those corresponding to a true change that occurred in the patient. Apparently, photon noise originating from Xrays may be one factor that could contribute to the large digitalization error observed for photostimulable plates of the Digora system 4,6,17,18 . As observed in Table 2 through Table 5, the lower exposure times (0.3; 0.2; 0.1; 0.05 s) showed, in general, higher pixel variability.…”

Clinical and Technical Evaluation of Full Field Digital Mammography

“…35 " 38 Computing the two-dimensional (2D) NPS is important to study the presence or absence of any off-axis noise peaks. Since the computation time of computers is no longer a constraint, 35 computing the entire 2D NPS and estimating the one-dimensional (ID) NPS from the 2D NPS was used.…”

PSNR Correlation between CR and DR according to Changed KvP

“…의학영상을 획득하기 위하여 사용되는 진단영역의 방사선 에너지 대역은 40 kVp ~ 150 kVp의 범위를 사용하고 있다 [2] . 변조전달함수) [3] , 잡음력스펙트럼(noise power spectrum; NPS) [4] , 양자검출효율(detective quantum efficiency; DQE) [5] , RMS(Root Mean Square) [6] , 위너 스펙트럼 (Wiener spectrum), Entropy 등이 있다.…”