Technologies such as 3D, contrast agents, Doppler imaging and hand-held echocardiography systems are blazing new paths to better cardiac care - and research into intuitive ways to annotate digital echo studies to allow instant access to specific images hopes to speed diagnosis and image sharing in the not-too-distant future.
The only thing small about echocardiography is the footprint of the ultrasound units - in comparison to their CT, MR and nuclear medicine cousins. This robust component of any hospital's cardiology department is expanding annually due to the rising number of patients requiring cardiac care. And today, it is being driven by a number of innovative technologies, such as three-dimensional imaging, contrast agents, Doppler imaging and hand-held echo. These technologies also are opening the door to new applications in the future.
Ultrasound has proven itself as a dependable, largely non-invasive and fairly inexpensive modality to diagnose and monitor conditions of the heart. Of these conditions, cardiovascular disease (CVD) is currently the No. 1 cause of death in the United States, claiming the lives of nearly 950,000 Americans each year. CVD includes high blood pressure, coronary heart disease, congestive heart failure, stroke and congenital heart defects.
In a recent report published by the American Heart Association (AHA) titled "Heart Disease and Stroke Statistics," the organization reveals a number of alarming statistics: coronary heart disease (the single largest killer of Americans) accounts for one in five women's deaths; an estimated 700,000 Americans will suffer a coronary attack this year; cardiovascular disease is the No. 3 cause of death for children under the age 15; and at age 40, the lifetime risk of developing congestive heart failure (CHF) for both men and women is one in five.
As these numbers increase, so has the use of echo in cardiology departments and heart centers. From 1992 to 2001, ultrasound use among U.S. cardiologists increased by 87 percent, according to a group of researchers from Thomas Jefferson University in Philadelphia. Led by David Levin, MD, former chairman of radiology at the institution, the study specifically concluded that echocardiography utilization among U.S. cardiologists surged 88 percent.
"The cardiology ultrasound imaging equipment market is the second largest clinical segment of the U.S. ultrasound market with more than $383 million in revenue in 2003," says Luke Liem, medical imaging research analyst for Frost & Sullivan. "The market will continue to experience healthy growth in both revenue and unit shipments going forward as a result of an increase in the U.S. population age 55 and older, an increase in the cumulative patient population who have undergone open-heart surgeries and cardiac catheterizations, and a strong pipeline of technological innovations."
3D IMAGING ON THE MOVE
One promising innovation in echocardiography is three-dimensional (3D) imaging. In November 2002, Philips Medical Systems debuted real-time 3D imaging, Live 3D Echo, on its Sonos 7500 high-end cardiovascular ultrasound unit. An installed base of about 700 hospitals, private practices and academic institutions are now using Live 3D Echo.
"It comes close to the resolution that you get in two-dimensional imaging, except its spread in 3D space in real time," says David Sahn, MD, professor of pediatric cardiology at the Oregon Health and Science University in Portland. The facility uses live 3D for both adult and pediatric echocardiography in clinical and research settings.
"The pediatric exams are for strange ventricles or strange valves, septal defects, and prenatal imaging at 16 to 17 weeks," explains Sahn. "We are doing intra-operative imaging in 3D to help the surgeon look at anatomy before and after bypass. We are looking at mostly valvular disease, although we are looking at some contrast implications of live 3D that may give us an approach to perfusion."
Capturing real-time 3D echo images requires a transducer technology that can put together the 3D volume in less than a 15th or 20th of a second, says Sahn. The speed of sound and the need to acquire the image one line at a time was the biggest limitation previously hindering 3D's use in live echo imaging. Most ultrasound machines create high-resolution images by transmitting and receiving single beams. One frame of a 2D ultrasound image is typically composed of 96,160 lines; for 3D, an image frame is composed