Effect of RR interval variation on image quality in gated, two-dimensional, Fourier MR imaging.

The effect of uneven repetition time (TR) intervals on artifact production during gated two-dimensional Fourier magnetic resonance image acquisition was investigated and a means of compensation presented. In standard spin-echo imaging, incomplete longitudinal recovery combines with normal respiratory heart rate variations to modulate signal intensity and create image copies and smearing along the phase direction. Modulation amplitude, frequency, and pattern, as well as machine parameters including echo time, TR, field of view, and image matrix size, have been found to have a substantial impact on artifact position and intensity. In a group of 10 healthy volunteers, respiratory-induced heart rate modulation produced an average of 17.2% +/- 4.9 variation in the raw data signal, with a mean frequency of 0.36 Hz +/- 0.06. The results of this study indicate that image artifacts caused by heart rate variations within the imaging period are predictable and may be reduced by correcting signal intensity for each phase view before two-dimensional Fourier transformation.