A Cornell graduate student in biomedical engineering has overcome one of the problems that has kept ultrasound devices large and bulky. By building a transducer that almost doubles in efficiency, George K. Lewis and adviser William L. Olbricht were able to build a pocket-sized high-intensity therapeutic ultrasound. The researchers hope that their new technology, now undergoing animal trials, one day will make it into portable clinical devices that could “stabilize a gunshot wound or deliver drugs to brain cancer patients.”
Tinkering in his Olin Hall lab, George K. Lewis, a third-year Ph.D. student in biomedical engineering and a National Science Foundation fellow, creates ultrasound devices that are smaller, more powerful and many times less expensive than today’s models. Devices today can weigh 30 pounds and cost $20,000; his is pocket-sized and built with $100. He envisions a world where therapeutic ultrasound machines are found in every hospital and medical research lab.
Lewis suggests that his technology could lead to such innovations as cell phone-size devices that military medics could carry to cauterize bleeding wounds, or dental machines to enable the body to instantly absorb locally injected anesthetic.
Lewis miniaturized the ultrasound device by increasing its efficiency. Traditional devices apply 500-volt signals across a transducer to convert the voltage to sound waves, but in the process, about half the energy is lost. In the laboratory, Lewis has devised a way to transfer 95 percent of the source energy to the transducer.
His new devices are currently being tested in a clinical setting at Weill Cornell Medical College. Under the direction of Jason Spector, M.D, director of Weill Cornell’s Laboratory for Bioregenerative Medicine and Surgery and assistant professor of plastic surgery, Peter Henderson, M.D., the lab’s chief research fellow, is using one of the devices in experiments that aim to minimize injury that occurs when tissues do not receive adequate blood flow.
Their lab is performing tests in animals to determine whether low doses of the chemical hydrogen sulfide, known to be toxic at high doses, might be able to minimize such injury by slowing cellular metabolism.
Doctors are hopeful that the ultrasound from Lewis’ portable device will enable hydrogen sulfide to be targeted to specific parts of the body, allowing doctors to use less of it, and cutting down on toxicity risks, Henderson explained.
From the article abstract in Review of Scientific Instruments:
We have developed a portable high power ultrasound system with a very low output impedance amplifier circuit (less than 0.3 Omega) that can transfer more than 90% of the energy from a battery supply to the ultrasound transducer. The system can deliver therapeutic acoustical energy waves at lower voltages than those in conventional ultrasound systems because energy losses owing to a mismatched impedance are eliminated. The system can produce acoustic power outputs over the therapeutic range (greater then 50 W) from a PZT-4, 1.54 MHz, and 0.75 in diameter piezoelectric ceramic. It is lightweight, portable, and powered by a rechargeable battery. The portable therapeutic ultrasound unit has the potential to replace “plug-in” medical systems and rf amplifiers used in research. The system is capable of field service on its internal battery, making it especially useful for military, ambulatory, and remote medical application
Abstract in Review of Scientific Instruments…
Cornell press release: Grad student develops pocket-size, inexpensive ultrasound device…
Images: Top: George K. Lewis with his newest portable ultrasound device. Bottom: Ultrasound waves created by one of Lewis’ devices leave the transducer, submerged under water, causing the water to bubble, spray and turn into steam.