Study of Noise Properties for Multi-objective Frequency Processing Using Computed Radiography
Tomoyuki Maruyama, Tsuneo Watanabe, Yoshihiko Kawamura · Japanese Journal of Radiological Technology · 2001
The current frequency processing of computed radiography(CR)is done by an unsharp masking(USM)filter. It emphasizes the noise of CR that influences the high-frequency wave component on the harmonic wave for the rectangular wave. In this study, we measured the overall Wiener spectrum(WS)of the multi-objective frequency processing(MFP)filter and the USM filter. The newly developed MFP is like a Gaussian curve for the imaging forms of processing on smoothing, and its noise properties are better than those of the USM filter. MFP has multi-frequency balance types(MRB)ranging from the "A-type"to"F-type, "and the overall Wiener spectral value decreases stepwise from"A-type"to"F-type." An important function of MFP is that processing emphasizes depression in which conversion by non-linear function depends on contrast, so that overall Wiener spectral values from 0.1-2.0 cycles/mm of spatial frequency decrease to the low frequency wave band. In this way MFP is more similar to conventional film than processing by USM.