Magnetic resonance-guided focused ultrasound surgery: Part 2: A review of current and future applications

Abstract

Magnetic resonance-guided focused ultrasound surgery (MRgFUS) is a novel combination of technologies that is actively being realized as a noninvasive therapeutic tool for a myriad of conditions. These applications are reviewed with a focus on neurological use. A combined search of PubMed and MEDLINE was performed to identify the key events and current status of MRgFUS, with a focus on neurological applications. MRgFUS signifies a potentially ideal device for the treatment of neurological diseases. As it is nearly real time, it allows monitored provision of treatment location and energy deposition; is noninvasive, thereby limiting or eliminating disruption of normal tissue; provides focal delivery of therapeutic agents; enhances radiation delivery; and permits modulation of neural function. Multiple clinical applications are currently in clinical use and many more are under active preclinical investigation. The therapeutic potential of MRgFUS is expanding rapidly. Although clinically in its infancy, preclinical and early-phase I clinical trials in neurosurgery suggest a promising future for MRgFUS. Further investigation is necessary to define its true potential and impact.

Figure 1

Transcranial sonothrombolysis of clotted blood in a phantom setup with 230Khz, 30seconds, 10% duty cycle, 3950W. After performing a calibration sonication in the center of the middle column of clotted blood, lysis parameters can be tested at additional locations. Pre (A) sonication T2 MRI. In (B) the blue spots are completed sonications. In figure C, discrete areas of clot lysis at the target areas are demonstrated by increased T2 signal.

Figure 1

Transcranial sonothrombolysis of clotted blood in a phantom setup with 230Khz, 30seconds, 10% duty cycle, 3950W. After performing a calibration sonication in the center of the middle column of clotted blood, lysis parameters can be tested at additional locations. Pre (A) sonication T2 MRI. In (B) the blue spots are completed sonications. In figure C, discrete areas of clot lysis at the target areas are demonstrated by increased T2 signal.

Figure 1

Transcranial sonothrombolysis of clotted blood in a phantom setup with 230Khz, 30seconds, 10% duty cycle, 3950W. After performing a calibration sonication in the center of the middle column of clotted blood, lysis parameters can be tested at additional locations. Pre (A) sonication T2 MRI. In (B) the blue spots are completed sonications. In figure C, discrete areas of clot lysis at the target areas are demonstrated by increased T2 signal.

Figure 2

Demonstration of focal heating of the trigeminal nerve root entry zone in a cadaveric laboratory setup. In this example a discrete 8 degree temperature rise as measured by realtime MR thermometry (top panels) was achieved with the ExAblate 650Khz system with 750W for 10s. Such a MRgFUS system could be used to focally heat the trigeminal nerve for the treatment of trigeminal neuralgia.