title: Measurements of MTF and SNR(f) using a subtraction method in MRI.
abstract: A method was developed for accurate measurement of the modulation transfer function (MTF) and signal-to-noise ratio in the spatial frequency domain (SNR(f)) of magnetic resonance images (MRI). The MTF was calculated from the complex images of a line object which were obtained by the subtraction of two separately acquired data sets of a specially designed phantom with a sliding sheet. Moreover, the SNR(f) was calculated from the MTF and Wiener spectrum, both of which were determined using the same phantom configuration. The MTFs and SNR(f)s in the conventional spin-echo (SE) and turbo SE, in which the effective echo time was set to the first echo, were evaluated by changing the T2 of the phantom and the echo train length. The MTFs in the positive and negative frequencies indicated the effect of the k-space trajectory for each pulse sequence. SNR(f)s gave spatial frequency information that was not obtained with conventional methods. In this method, the influence of image nonuniformity and unwanted artefacts (edge and ghost) could be eliminated. An analysis of the MTF and the SNR in the spatial frequency domain provides additional information for the assessment of image quality in MRI.
authors.affiliation: Department of Radiological Technology, School of Health Sciences. Faculty of Medicine, Kanazawa University, Ishikawa, Japan. ramiyati@mhs.mp.kanazawa-u.ac.jp
authors.forename: Tosiaki
authors.initials: T
authors.lastname: Miyati
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fujita
authors.forename: Toshio
authors.initials: T
authors.lastname: Kasuga
authors.forename: Kichiro
authors.initials: K
authors.lastname: Koshida
authors.forename: Shigeru
authors.initials: S
authors.lastname: Sanada
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Banno
authors.forename: Mitsuhito
authors.initials: M
authors.lastname: Mase
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamada
mesh_terms: D016477:Artifacts; D007089:Image Enhancement / Q000295:instrumentation / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D011786:Quality Control; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013269:Stochastic Processes; D013382:Subtraction Technique