Phase shift due to inversion recovery process and chemical shift effect in inversion recovery prepared gradient-echo magnetic resonance imaging.

PURPOSE: The purpose of this study was to assess phase shift due to the inversion recovery process and the chemical shift effect in inversion recovery prepared gradient-echo magnetic resonance imaging. MATERIALS AND METHODS: The signal intensities of three phantoms, composed of physiologic saline solution with Gd-DTPA, olive oil, and fat emulsion, were measured on a 1.5 Tesla unit. The sequence was single-shot two-dimensional. The parameters were as follows: TI 100-2500 msec at 100 msec intervals, TR 11.25 msec, TE 2.250 msec, 3.375 msec, and 4.500 msec. The k-space was filled with the centric view order. RESULTS: The signal intensity curves of the emulsion showed various patterns. At a TE of 2.250 msec, TI at the minimum value of signal intensity was 1500 msec. At a TE of 4.500 msec, TI at the minimum value was 500 msec. Up to a TI of 1000 msec, the signal intensity at a TE of 2.250 msec was stronger than that at a TE of 4.500 msec, and from a TI of 1000 msec, the signal intensity at a TE of 4.500 msec was stronger than that at a TE of 2.250 msec. CONCLUSION: We concluded that fat emulsion showed paradoxical phase shift.