Principles of MR guided Focused Ultrasound Surgery (MRgFUS) Treatment

MRgFUS combines two well-known technologies: ultrasound and Magnetic Resonance Imaging to provide non-invasive treatment alternative for uterine fibroids. High Intensity Focused Ultrasound (HIFU) waves are used to non-invasively heat and thermally destroy the fibroid, while magnetic resonance imaging (MRI), provides continuous detailed anatomical images for treatment planning guidance, allows for real-time thermal monitoring during the treatment, and post-procedural assessment of the extent of treatment after the administration of a gadolinium contrast.

Focused Ultrasound generates heat by focusing ultrasound waves, ablating tissue only at the focal point, an effect similar to a magnifying glass used to focus the sun’s energy on a single point.

The high-intensity ultrasound deposits localized energy, causing rapid vibration of molecules within the focal spot. The energy causes the temperatures at the focal spot to rise to 60-80°C resulting in thermal ablation of a small area (1-2cc) of tissue. A larger volume is ablated by treating multiple adjacent small areas. The number of sonications and thus the length of the treatment depend on the size of the fibroid. The time required for the entire MRgFUS procedure ranges from 120-180 minutes.

agnetic resonance imaging (MRI) is superior for imaging soft tissue compared to other modalities, in addition to being able to monitor temperature and tissue coagulation and therefore avoid damage to the surrounding normal tissue.

R imaging provides highly precise 3D anatomical information for exact tumor localization and visualizes the beam path to avoid surrounding tissue, nerves, scars and other organs to enable safe targeting of the energy. It also provides real time and continuous MR thermal feedback, to help determine whether the energy was directed correctly and the appropriate amount delivered. This continuous closed loop feedback mechanism allows the physician to adjust parameters according to the patient’s needs.

Post-treatment contrast imaging is used to evaluate the treatment outcome.

This use of MR with focused ultrasound provides the ability to get immediate feedback, react to that feedback, and know immediately what the outcome is. This provides the doctor with information that ensures efficacy and safety of the procedure.

Published Evidence Supporting MR guided Focused Ultrasound

MR guided Focused Ultrasound Surgery is well established. Thousands of patients have been treated worldwide. There is a broad evidence base supporting MRgFUS in a variety of therapeutic settings . Over 70 peer reviewed papers have shown that MRgFUS is safe and effective in the treatment of uterine fibroids, with up to three year follow-up.

The top five papers about uterine fibroids are the following:

  1. Stewart E, Gostout B, Rabinovici J, Kim HS, Regan L, Tempany CM for the MRI guided Focused Ultrasound for Uterine Fibroid Group. Sustained Relief of Leiomyoma Symptoms by Using Focused Ultrasound Surgery, Obstetrics & Gynecology, 2007, 110(2):279-287.
  2. Gorny KR, Woodrum DA, Brown DL, Henrichsen TL, Weaver AL, Amrami KK, Hangiandreou NJ, Edmonson HA, Bouwsma EV, Stewart EA, Gostout BS, Ehman DA, Hesley GK. Magnetic Resonance-guided Focused Ultrasound of Uterine Leiomyomas: Review of a 12-month Outcome of 130 Clinical Patients, 2011, J Vasc Interv Radiol., 22(6):857-64
  3. Rabinovici J, David M, Fukunishi H, Morita Y, Gostout BS, Stewart EA, for the MRgFUS Study Group. Pregnancy Outcome After Magnetic Resonance-guided Focused Ultrasound Surgery (MRgFUS) for Conservative Treatment of Uterine Fibroids, Fertility & Sterility, 2008.
  4. Funaki K, Fukunishi H, Sawada K. Clinical Outcomes of Magnetic Resonance-guided Focused Ultrasound Surgery for Uterine Myomas: 24-months Follow-up, Ultrasound Obstet Gynecol, 2009, 34:584-589.
  5. Zowall H, Cairns JA, Brewer C, Lamping DL, Gedroyc WMW, Regan L. Cost-effectiveness of Magnetic Resonance-guided Focused Ultrasound Surgery for Treatment of Uterine Fibroids, BJOG, 2008, 115:653-662.