Acoustic pressure wave generation within an MR imaging system: Potential medical applications

The static magnetic field of a magnetic resonance (MR) imaging system was used as a component of an electromagnetic transducer for generating acoustic pressure waves. To permit limited focusing, the transducer was constructed from a conductive thin plate shaped like a section of a sphere. The plate was placed within the static field of the MR unit (B0 = 1.5 T), and current pulses with a rise time of 73 nsec and amplitude of 1.0 kA were applied to it. Hydrophonic recording demonstrated a shock wave with a peak pressure of 4.8 MPa at the approximated focal point. MR guidance of lithotripsy would be particularly useful to limit undesirable soft‐tissue damage. It is also suggested that the integration of an acoustic pressure wave generator with MR imaging and control provides a novel technology for the treatment of solid soft‐tissue tumors.