title: Monotone spline regression for accurate MTF measurement at low frequencies.
abstract: The modulation transfer function (MTF) of radiographic systems is frequently evaluated by the system's line spread function (LSF) using narrow slits. The conventional slit method requires LSF tail approximation, which is achieved by exponentially extrapolating the LSF tails beyond 1% of peak value. However, the estimated MTF at low frequencies from extrapolation may not reflect the true performance of the system. In this study, a monotone spline regression technique for LSF tail approximation is developed to improve the accuracy of MTF estimation at low frequencies. This technique is based on the underlying physical principles of the system response. The advantages of this technique are demonstrated with simulated examples of which the true MTFs are known. The application of this measurement technique is also demonstrated.
authors.forename: Zhongxing
authors.initials: Z
authors.lastname: Zhou
authors.forename: Feng
authors.initials: F
authors.lastname: Gao
authors.forename: Huijuan
authors.initials: H
authors.lastname: Zhao
authors.forename: Lixin
authors.initials: L
authors.lastname: Zhang
authors.forename: Liqiang
authors.initials: L
authors.lastname: Ren
authors.forename: Zheng
authors.initials: Z
authors.lastname: Li
authors.forename: Muhammad U
authors.initials: MU
authors.lastname: Ghani
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
mesh_terms: D000465:Algorithms; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D012044:Regression Analysis; D015203:Reproducibility of Results