Quantitative assessment of wall motion in multiple-gated studies using temporal Fourier analysis

We described a method for quantification of left-ventricular wall motion in multiple-gated studies, based on approximation of local time-activity curves by the first harmonic of the corresponding Fourier spectrum. The Fourier transform is adapted to the global left-ventricular time-activity curve by shortening the length of the base period. The degree of shortening depends on the corresponding power in the second and higher harmonics; the base period that resulted in minimal power in the higher harmonics was selected for a Fourier transform of the regional curves. This usually results in exclusion of both the diastasis phase and the left-atrial filling phase from the calculations. With a model of the left-ventricular volume curve it is shown that important advantages of this adaptation are (a) a better approximation of the maximum difference in the curves, and (b) less spread in the phase determination. Wall motion was related to the Fourier parameters. The combination of the mean amplitude and the standard deviation of the phase histogram gives the best results for global analysis of the motion of the wall.