A Lens that Goes Straight to the Heart

MILLING A LENS THAT GOES STRAIGHT TO THE HEART

HOUGHTON, Mich.--An ultrasound device that features a lens only one millimeter across could help prevent coronary arteries from re-blocking following bypass surgery.

The lens, milled by Dr. Craig Friedrich, an associate professor of mechanical engineering at Michigan Technological University, is part of an ultrasound system developed in cooperation with Professor Robert Keynton of the University of Louisville. The integrated miniature acoustical lens-transducer system, as it is called, measures the dragging force of blood against the walls of arteries as it surges by.

"For instance, when surgeons do a graft, they could use it to make sure the blood is flowing by smoothly, with no turbulence," Friedrich said. Turbulence may cause inflammation on the inside of arteries, which can result in more plaque build-up and subsequent blockage.

The lens focuses intense ultrasound waves on the interior walls of blood vessels to measure the "shear stress" of the blood flow. Currently, the system is being used to determine if this shear stress causes arterial re-blockage following coronary bypass surgery.

What makes this lens special is not only its size--it's as thick as two strands of human hair--but also how it's made. Using micromachining techniques to make tiny lenses is nothing new, but keeping them in shape is.

Most errors occur when the lens is attached to the transducer, the part of the system that changes sound waves to electrical energy. This time, the researchers managed to create the perfect lens by milling it out after the system was assembled.

The device holds promise in a number of different areas, including detecting small tumors. And Friedrich says more breakthroughs are in the wings.

"This project started about six years ago, and we've made a lot of progress on tiny acoustic devices since then," he said.

CONTACT INFO FOR REPORTERS:Craig Friedrich: 906-487-1922, [email protected]

Robert Keynton: 502-852-6356, [email protected]

JOURNAL INFORMATION: The research paper "Design and fabrication of a miniaturized integrated, high frequency acoustical lens-transducer system" by Jinghong Li, Craig R Friedrich and Robert S Keynton is being published in Journal of Micromechanics and Microengineering, Volume 12, Number 3, May 2002. For a full copy of this paper, please contact Dr Alice Bows, press officer, Institute of Physics; Tel(0)20 7470 4800, e-mail [email protected]

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