A new fast and unsynchronized method for MRI of viscoelastic properties ofsoft tissues

Quantitative measurement of mechanical properties of biologic tissues may h ave several applications for diagnosis or biomechanic modeling in sports me dicine, traumatology, or computer-guided surgery. The magnetic resonance im aging (MRI) methods previously tested for these applications all required s ynchronization between MRI acquisition pulses and the mechanical stimulatio n. A new unsynchronized method operating with no prior knowledge of intensi ty, direction, and frequency of the mechanical waves is proposed. A specifi cally modified SPAMM (SPAtial Modulation of Magnetization) sequence has bee n used, operating on a 0.2-T MRI system. The experimental results obtained on test objects fit well with theoretical calculations. The new proposed me thod Is very fast (a less than 5-second acquisition time) for routine clini cal use. (C) 2000 Wiley-Liss, Inc.