Indication of MR Image-guided Focused Ultrasound

Abstract

  Transcranial MR-guided focused ultrasound (MRgFUS) can be used for tissue coagulation by focusing ultrasound on a single target at high density. MRgFUS has been developed and clinically applied as a device that can create coagulation foci non-invasively, as the coagulation focus and temperature can be observed in real-time by MRI.

  The procedure to focus on coagulation with MRgFUS is as follows : preoperative MR images are performed to plan the target and CT scans are used to mark areas, including air and calcification where ultrasound cannot penetrate. The stereotactic surgical frame was fixed to the patient's head. After setting up, MRI was performed again to confirm the target. The treatment was performed while confirming that the temperature increased at the planned target. Once the tissue temperature rose to approximately 45℃, improvement of the patient's symptoms was examined. The power of ultrasound and duration of sonication were further adjusted to increase the temperature to create a sufficient coagulation focus in the targets.

  Thalamotomy by MRgFUS for essential tremors has been covered by public insurance in Japan since June 2019. To this date MRgFUS has been used in more than 250 cases, and its efficacy has been recognized. MRgFUS has also been used to treat Parkinson's disease since 2020. In the future, MRgFUS is expected to expand its indications to include neurological and psychiatric disorders other than neurodegenerative and movement disorders.