COMPUTING THE MODULATION TRANSFER-FUNCTION OF A MAGNETIC-RESONANCE IMAGER

A new method for computing the modulation transfer function (MTF) of m agnetic resonance (MR) imagers is presented. Previous attempts to comp ute the MTF of MR imagers used nonlinear magnitude reconstructed image s, resulting in erroneous MTFs. By using complex domain images, the ne w method produces predisplay MTFs which describe the spatial frequency transfer characteristics of the entire image formation process, excep t the magnitude operator, eliminating the artifacts previously found i n MR imager MTFs. The use of complex domain images results in two-side d MTFs which differentiate the positive and negative frequencies assoc iated with positive and negative phase encoding or positive and negati ve time relative to the echo formation. Experimental results are prese nted which confirm the theoretically predicted form of MR imager MTFs and the need for two-sided MTFs.