MRI-Guided Ultrasound Destroys Tumor Without Breaking Skin

Using an MRI to guide high-intensity ultrasound waves, physicians at The Hospital for Sick Children (SickKids) in Toronto, Ontario, Canada, were able to destroy a benign bone tumor called osteoid osteoma in a 16-year-old boy without breaking the skin, marking the first successful procedure of this kind in North America. The lesion had reportedly caused the patient excruciating pain for one year prior to the procedure, but by the time he went to bed that night, the teen reported complete pain relief.

Since the mid-1990s, minimally invasive treatments have been used to burn the tumor. In these treatments, radiofrequency or laser energy is delivered through a needle placed, using CT guidance, in the tumor. These therapies are effective and less risky than invasive surgery and are currently widely used. However, these procedures still carry risks, including radiation exposure from CT, infection, burning of the surrounding tissue, and bone fractures resulting from the hole that remains following tumor treatment.

High-intensity focused ultrasound therapy uses sound waves to heat, under MRI guidance, an area the size of a grain of rice, and destroy the tumor. The treatment is completely noninvasive so the skin and surrounding bone remain intact, greatly reducing the risk of complications, particularly infections. Using MRI rather than CT to guide the sound waves means the patient avoids ionizing radiation exposure. The risk of bone fracture is also likely lower than in other treatments, and recovery is quick. An added benefit is rapid pain relief.

“With high-intensity focused ultrasound, we are moving from minimally invasive to noninvasive therapy, significantly reducing risk to the patient and fast-tracking recovery,” says interventional radiologist Michael Temple, MD, who led the team that performed the surgery. “The osteoid osteoma tumor was chosen as our pilot study because the lesion is easily accessible and while the procedure is sophisticated, it is relatively straightforward. The success of this first case is great news for [the patient] and exciting for our team as we look at developing more complex incisionless treatments in the future.”

The procedure was performed using a specialized MRI table with support from Sunnybrook Health Sciences Centre’s MRI and radiation oncology staff. While the surgery itself took 30 minutes, it required about three hours of preparation, which involved general anesthesia and precise placement of the patient on the table, which is equipped with a built-in, high-intensity focused ultrasound transducer. The team used MRI to determine the tumor’s exact location and to help target the ultrasound waves to eventually ablate the entire tumor, one focal spot at a time. Using MRI also enabled them to monitor the temperature induced by the ultrasound to ensure there was no unexpected increase in heat in surrounding tissues. Accurate positioning and monitoring are critical as heat from the focused ultrasound waves could damage surrounding tissues, nerves, or skin.

The patient was discharged a few hours after the procedure and two days later was able to resume most daily activities.

High-intensity focused ultrasound therapy is available in pediatric and adult centers in Europe. The procedure was first performed on patients with osteoid osteoma in Italy in 2010 and is currently used in North America to treat uterine fibroids and bone metastases in adult patients.
Source: The Hospital for Sick Children