Biomedical Imaging and Biophotonics

DIY guide could bring big breakthroughs in focused ultrasound therapy

Focused ultrasound is an emerging, minimally invasive therapy approved to treat bone metastases, uterine fibroids and prostate tumors, with research showing promise in treating dozens of other conditions.

But the prohibitive cost of dedicated focused ultrasound machines has been a barrier to further research.

Enter William Grissom, assistant professor of biomedical engineering. Working with Charles Caskey, assistant professor of radiology, he is throwing open the doors of access by producing a do-it-yourself guide using open-source software so researchers can convert imaging machines into focused ultrasound machines and find their own applications.

“The lack of well-described, accessible, preclinical focused ultrasound systems (FUS) limits progress and decreases repeatability of new developments,” Grissom told the Focused Ultrasound Foundation. “Our open-source system can deliver repeatable, precise and quantifiable thermal and mechanical focused ultrasound over an extended periodin small animals.”

The instructions for hardware and the needed software are downloadable for free on the Vanderbilt University Institute for Imaging Science website. The hardware costs about $10,000, mostly for the MR-compatible transducer and amplifier and the function generator, Grissom said, and making the information widely available will be a boon to research.

The underlying principle of focused ultrasound is similar to the experiment in any beginning science book—use a magnifying glass to focus the sun’s rays, and you can generate enough heat to burn a leaf. Focused ultrasound uses an acoustic lens to concentrate the ultrasound beams on a precise spot in the body, leaving the surrounding tissue unharmed.

“It’s just cranking the power way up on a regular ultrasound system and using a lower frequency than with imaging ultrasound,” Grissom said. “You can put a lot of focused energy into one place, and the mechanical acoustic energy is converted into heat. The heat is what ends up killing the targeted tissue, with no damage to the intervening tissue.”

In addition to not harming surrounding tissue, focused ultrasound requires no incisions and, unlike metal devices that must be inserted into the body, is usable with magnetic resonance guidance so surgeons can see what they’re targeting.

The project was funded through a Department of Defense grant to investigate whether FUS could be used to train the immune system to kill the body’s cancers, leveraging the abscopal effect, where localized treatment of tumors also shrinks tumors outside that zone.

Top Photo: In addition to focused ultrasound, Assistant Professor of Biomedical Engineering William Grissom works on a radio frequency coil array for imaging the prostate using ultra-high-field MRI.