MR-Guided Ultrasound Safe, Effective for Fibroid Ablation

Pam Harrison

March 22, 2013

VIENNA, Austria — Advances in magnetic resonance-guided focused ultrasound technology have led to improved results for uterine fibroid ablation, with few safety concerns, a new study shows.

"This noninvasive, incision-free approach to the treatment of uterine fibroids is hugely beneficial to women because it can be a true alternative to surgery," said researcher Matthias Matzko, MD, from the University of Munich in Germany.

He presented the study findings here at the European Congress of Radiology (ECR) 2013. The results were also published online February 4 in Investigative Radiology.

During magnetic resonance-guided focused ultrasound, imaging is used to identify fibroids amenable to ultrasound treatment. Focused sound waves, or sonications, are then sent into the fibroid to heat and destroy small areas. The MRI is temperature-sensitive, allowing for real-time thermal mapping during the procedure. Patients can stop at any time if they find the procedure too uncomfortable.

Historically, the focused ultrasound transducer was fixed in the MRI bed. However, the latest version of the technology, known as ExAblate 2100 by inSightec, which was used by Dr. Matzko and his team, gives operators more freedom.

The transducer is also elevated, which dramatically reduces the amount of energy transferred through the skin, so it can concentrate more effectively in the fibroid itself. "This leads to significantly fewer side effects, including heat sensations and skin burns," Dr. Matzko explained.

Operators can also adapt the beam and automatically shut off parts of the transducer when passing through zones like the intestine, strengthening the technology's safety profile.

"We also have automatic and volumetric treatment planning, so it's much faster because you don't have to adapt manually on every spot," he added.

Noninvasive, Incision-Free

All of these improvements have greatly enhanced the ability of operators to achieve target nonperfused volume ratios. After treatment, unenhanced areas on imaging represent the nonperfused volume to which the blood supply has been interrupted by the procedure. This is the most important predictor of success, Dr. Matzko noted.

The researchers retrospectively reviewed 115 women with symptomatic fibroids. The average total volume was 89 cm³, and the average number of fibroids treated per patient was 2.2.

The magnetic resonance-guided focused ultrasound was 93.5% technically successful, and the average nonperfused volume ratio was 88.0%, he reported. Historically, nonperfused volume ratios have been approximately 60%, which is within treatment targets but not ideal, Dr. Matzko said.

The mean applied energy level delivered by the ultrasound technology was 5400 J, and the mean number of sonications was 74. The only significant factor that affected the nonperfused volume ratio was the planned treatment volume.

"No major complications occurred," Dr. Matzo said. There were only 2 cases of first-degree skin burns, and they resolved within a week of the procedure.

With this technology, "we are faster than before [3.5 vs 4.5 hours] and much more efficient," Dr. Matzko said. "So this works out for the better for both patients and the physician," he noted.

ECR cochair Robbert Nijenhuis, MD, from the University Medical Center Utrecht in the Netherlands, who was asked by Medscape Medical News to comment on the study, noted that there are different types of fibroids, and highly vascularized fibroids are not amenable to magnetic resonance-guided focused ultrasound because not enough heat can be generated for adequate ablation.

It is also not well suited to treat very large fibroids or a large volume of fibroids.

Nevertheless, Dr. Nijenhuis said, "if women want to retain their uterus, this is absolutely an alternative to hysterectomy.... Provided patients are properly selected, focused ultrasound is absolutely a possibility."

Dr. Matzko reports being a speaker for GE Healthcare and inSightec Ltd. Dr. Nijenhuis has reported no relevant financial relationships.

Invest Radiol. Published online February 4, 2013. Abstract

European Congress of Radiology (ECR) 2013. Abstract B491. Presented March 8, 2013.