Magnetic resonance acoustic radiation force imaging of deformations induced by acoustic holograms

Motivation: Therapeutic mechanical perturbations of tissue require more precise MR-guided focused ultrasound techniques. Goal(s): The goal of this study was to demonstrate the feasibility of MR-ARFI for measurement of tissue displacement induced by arbitrary ultrasound pressure patterns encoded in acoustic holograms. Approach: Holographic lenses were designed to focus ultrasound into a 2 cm-diameter ring inside a gelatin phantom. A 2D spin echo MR-ARFI pulse sequence encoded displacement into the phase of the MR signal. Results: MR-ARFI generated phase maps that were consistent with simulated displacement of gelatin phantoms. Distortions of the desired pattern were observed, likely due to physical misalignment of lenses. Impact: This study shows that MR-ARFI may be suitable for precise guidance of therapeutic mechanical stimulation by measuring the microscopic deformation of tissue induced by ultrasonic holograms.