High-intensity focused ultrasound relies on ultrasound waves at an intensity several orders of magnitude higher than those used in medical imaging. The waves are focused much in the same way a magnifying glass focuses sunlight to burn a dry leaf, according to Viren Amin.
In medical applications, high-intensity focused ultrasound can precisely destroy cells by generating heat, but it can do so without destroying cells outside the focused area. "You want to cook only the tumour and not the surrounding cells", Viren Amin stated.
There are challenges to overcome before the ultrasound technology can be used to destroy brain tumours. "We need to predict what the ultrasound beam will do when it goes through so many layers of tissue", Viren Amin stated. This tissue "inhomogeniety" causes ultrasound energy to be localized in hot spots.
Ron Roberts, a scientist at the Center for Nondestructive Evaluation, and Bruce Thompson, the centre's director, have developed computational models for ultrasound transmission through inhomogeneous materials. According to Viren Amin, this knowledge can be applied to medical applications to develop high-precision ultrasound therapy.
Another challenge is calculating and delivering the therapy dose - the frequency, intensity and focus - for a specific tumour type and location. Researchers will develop imaging and visualization tools to integrate MRI and ultrasound images as well as simulations of ultrasound beams through tissues and of the heat generated at the focus. These tools will be used to help plan high-intensity focused ultrasound treatments. "It's a true multi-disciplinary project", stated Viren Amin, who has degrees in medicine and biomedical engineering.
Other team members include Ron Roberts and Bruce Thompson of the Center for Nondestructive Evaluation; Mark Bryden, a faculty fellow in the Virtual Reality Applications Center and an ISU associate professor of mechanical engineering; and Scott McClure, an ISU professor of veterinary medicine. Other collaborators include Timothy Ryken, a doctor in the department of neurosurgery and radiation oncology at the University of Iowa in Iowa City; and Shahram Vaezy, an expert in high-intensity focused ultrasound from the University of Washington in Seattle.
The team's research is supported by a $350.000 research grant from the Roy J. Carver Charitable Trust.