Since its inception in 2000, MRI-guided focused ultrasound ablation had been proven effective only on benign breast lesions. It is also safe and effective on malignant lesions, according to Canadian researchers.Investigators treated 12 patients with
Since its inception in 2000, MRI-guided focused ultrasound ablation had been proven effective only on benign breast lesions. It is also safe and effective on malignant lesions, according to Canadian researchers.
Investigators treated 12 patients with small, malignant breast tumors with two different ultrasound ablation systems before they underwent tumor resection. They found that MR-guided focused ultrasound ablation produced considerable thermal coagulation of tumor volume within the zones targeted for ablation. Their results appeared in the June issue of Radiology.
The technique is noninvasive and easily tolerated by patients, said coauthor Yvan Boulanger, Ph.D., an associate professor of radiology at the University of Montréal. It provides real-time planning of the treatment, volumetric control of the delivered thermal dose, and detection of the resulting tissue alterations.
No significant complications occurred - only two minor skin burns were reported - and patients were able to go home immediately after recovering from conscious sedation, he said.
The patient lies prone on the focused ultrasound table - a regular MR table modified to contain a computer-controlled transducer that is set up inside the magnet bore. The interventionalist positions the transducer to focus the ultrasound beam inside the breast tumor.
Through multiple sonications - short sound wave blasts lasting from 12 to 20 seconds - the temperature at the focal point increases, producing coagulation necrosis.
The study's histopathological analysis found that in three patients treated with an unmodified ablation system, 46.7% of cancer tissue was within the targeted zone, with 43.3% of it reaching necrosis. For the remaining nine patients treated with a system modified to focus the ultrasound beam up to 20 cm inside the body, a mean of 95.6% of the tumor was within the target zone, yielding 88.3% necrotic cancer tissue.
MR-guided focused ultrasound ablation has several advantages compared with other thermal ablation techniques. Unlike interstitial laser therapy and radio-frequency ablation, focused ultrasound ablation does not involve the insertion of a probe or any skin incision. In contrast to interstitial therapy, which uses a fixed probe, the focal point is changeable, providing high flexibility in controlling the size and shape of the treatment zone, Boulanger said.
The target volume that can be treated in one sonication is small but more homogeneous compared with other ablation techniques. Depending on the lesion, treatment can take from 30 minutes to 2.5 hours, according to the study.
"Focused ultrasound ablation takes a few seconds, resulting in local temperature elevations independent of perfusion rate, and it can be reproduced if ablation is only partially successful," Boulanger said.
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