Frequency analyses of CSF flow on cine MRI in normal pressure hydrocephalus.

Our objective was to clarify intracranial cerebrospinal fluid (CSF) flow dynamics in normal-pressure hydrocephalus (NPH). Frequency analyses of CSF flow measured with phase-contrast cine MRI were performed. The CSF flow spectra in the aqueduct were determined in patients ( n=51) with NPH, brain atrophy or asymptomatic ventricular dilation (VD), and in healthy volunteers (control group; n=25).

[Utility of fixed-quantity analysis in evaluating image noise and resolution in multi-slice CT].

We analyzed the spatial frequency of images generated with multi-slice CT (Z-axis) and estimated the definition and noise characteristics. The noise characteristics were calculated with Wiener spectra from multi planar reconstruction (MPR) images, and, in the evaluation of definition characteristics, the modulation transfer function (MTF) was calculated using section sensitivity profile (SSP) with the base method. The Wiener spectra showed a tendency for noise to decrease from a low frequency domain as the effective slice thickness increased.

Measurements of MTF and SNR(f) using a subtraction method in MRI.

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.