Die Modulations-Übertragungs-Funktion in der Magnetresonanztomographie – Praktische Anwendung und Grenzen

Abstract

The modulation transfer function (MTF) of an imaging system can be derived by Fourier transformation of its line spread function. A perspex/water phantom providing an interface with a variable contrast step was used to obtain MTF's in a magnetic resonance imaging system. A conventional spin echo pulse sequence, gradient echo plus sequences and fast imaging techniques were applied. The impact of particular pixel sizes was investigated by varying the field of view and the size of the acquisition matrix in a conventional spin echo sequence (TRITE 500/15 ms). The calculated MTF's for pixel sizes from 0.3 to 2.0 mm had cutoff frequencies slightly less than the theoretically achievable Nyquist frequency. No influence was seen when different contrast steps were applied. However, different pulse sequences such as spin echo, gradient echo or rapid gradient echo and fast spin echo sequences provided different MTF's. The impact on the practical application and the limitations of the procedure are discussed.