MTF Measurement in MRI Using a Complex Subtraction Method

Abstract

A complex subtraction method was developed to accurately measure modulation transfer functions(MTFs)in positive and negative frequencies of magnetic resonance images(MRI). The MTF was calculated from the line spread function, which was obtained with an original phantom by a process of subtraction of the complex images. The MTF in conventional spin-echo(SE)and Turbo SE, in which effective echo time was set at the first echo, were evaluated by changing the T_2 of the phantom in the frequency-and phase-encoding directions. MTFs indicated the characteristics of the k-space trajectory for each pulse sequence. Using this method, the influences of image nonuniformity and unnecessary artifacts could be eliminated. Analysis of the MTF with the complex subtraction method made it possible to obtain more detail regarding the resolution properties of MRI.