Edwin L. Aguirre
Ultrasound imaging, or sonography, is one of the most commonly used diagnostic tools in hospitals and clinics today. For example, at Mass General Hospital alone, more than 50,000 ultrasound exams are performed each year.
Ultrasound uses high-frequency sound waves to create real-time images of internal organs like the heart, kidneys and liver as well as blood vessels and muscles. During pregnancy, physicians and health-care professionals apply ultrasound to check the condition of the fetus. Unlike X-rays, ultrasound does not expose the patient to ionizing radiation.
Thanks to the collaborative work by a team of researchers from Texas A&M University, King’s College London and Queen’s University of Belfast in the U.K. and UMass Lowell, ultrasound could someday produce images that are even higher in quality and resolution. The team’s effort, which has been supported in part by grants from the U.K.’s Engineering and Physical Sciences Research Council and the U.S. National Science Foundation, was featured in a recent issue of the journal Advanced Materials.
The Advantage of Optical Ultrasound Sensors
During an ultrasound test, the doctor or technician typically moves a handheld device, called a transducer, over the part of the patient’s body to be examined. The transducer emits sound waves, which bounce off the tissues inside the body. The transducer then captures the reflected waves and converts them into electrical signals. Images are constructed from these signals.
“The sensitivity of transducers can be directly related to its resolution,” says Assoc. Prof. Viktor Podolskiy
of UMass Lowell’s Physics and Applied Physics Department
, who is a member of the team. “To get good resolution, one needs a transducer that is sensitive and has a broad bandwidth, meaning it is sensitive over a broad range of frequencies.”
To accomplish this, the researchers have developed a new material — called “metamaterial” — which converts ultrasound waves into optical signals that can be processed to generate highly detailed images. The metamaterial, consisting of gold nanorods coated with a polymer known as polypyrrole, offers greater sensitivity and broader bandwidth than with conventional, piezoelectric-based ultrasound technology.
“There is now a push toward optical readout and our experiments provide a material that is able to significantly improve optical ultrasound sensors for use in clinical diagnostics and biomedical research,” says Podolskiy.