A method for producing a magnetic resonance image indicative of mechanical
waves applied to a subject is provided. Mechanical waves are applied to
the subject at a selected frequency to induce oscillatory motion in
tissues within the subject at the same frequency. A spin-lock
radiofrequency pulse, having a resonance frequency matched to that of the
induced oscillatory motion, is applied to the subject. This results in a
spin-lock condition, during which transverse magnetization experiences
rotary saturation resulting from magnetic field fluctuations produced by
the oscillatory motion. Image data is acquired from the saturated
transverse magnetization and images are reconstructed. As a result of the
rotary saturation, these images exhibit darkening in those voxel
locations affected by the oscillatory motion. In this manner, an image
indicative of the applied mechanical waves is produced.