When Eugene Strandness arrived on the scene in the laboratory of Dr. Robert Rushmer in the UW Department of Physiology and Biophysics in the early 1960s, the method of ultrasound was being used to measure blood flow and blood vessel dimensions in animals.
Rushmer had put forth the concept that "nondestructive testing" methods could be used on live, active animals to yield unprecendented information about cardiovascular function. The idea of nondestructive testing was gaining use and acceptance in industry at the time. Based on the successes in animal experiments, Rushmer foresaw its potential use in humans to diagnose blood flow disorders.
Strandness and colleagues went on to show that harmless ultrasound waves could reveal characteristics of blood vessels and the blood moving inside them. The waves penetrated body tissues and bounced back; and using the Doppler effect, the researchers could estimate the speed of the blood as it coursed through an artery or a vein. The Doppler effect refers to the change in frequency (pitch) of sound waves emitted or reflected by an object as it moves toward or away from you, as when a siren changes from higher to lower pitch as an ambulance approaches, passes, and then recedes from you. The faster the sound source is moving, the greater the change in pitch. Similarly, ultrasound waves scattered by moving blood exhibit the same effect, and reveal the speed with which blood is moving.
Strandness, Rushmer and colleagues developed the first ultrasound instrument sold in the U.S.; it was called the Dopotone® , marketed by Smith-Kline Instrument Company. The device found two immediate applications: detecting the heartbeat of an unborn fetus, and measuring characteristics of the circulatory system.
Vascular surgeons needed a picture of the location and extent of lesions or obstructions in blood vessels in order to correct these disorders. Until ultrasound was developed, physicians had to rely on three basic types of information: the patient's description of symptoms, the absence of pulses in limbs or the presence of abnormal sounds or murmurs, and information from an x-ray technique called arteriography. Although arteriography could locate the site of disease, it was not suitable for long-term follow-up.
Strandness experimented with the measurement of limb blood pressure as a means to assess blood flow abnormalities, as in the case of atherosclerosis, which leads to the build-up of fatty plaques in the arteries. Another method, called plethysmography, could measure flow at the level of the toes, the forefoot, and the calf of the leg, but it was cumbersome and didn't really provide the kind of information needed. Strandness discovered that as an arterial obstruction gradually developed, the surrounding circulation usually compensated in order to maintain resting blood flow levels within a normal range. "It was possible to have a very ischemic [blood-deficient] foot and in some cases actual gangrene with normal levels of blood flow in the calf," he exclaims. What was needed was a method that would allow the physician to examine blood flow directly at any desired site in the body.
The initial instrument had many limitations; most notably, it used continuous waves, and so could not determine the exact site within tissue where flow was being detected. But this early work demonstrated the great promise of medical ultrasound, and a team of bioengineers came together to capitalize on it. A burst of inventiveness followed, led by Don Baker, Jack Reid, and others. Improvements were based on a pulsed system which used bursts of sound, permitting localization of the sampled site.
An ultrasound scanning device was developed in order to detect and distinguish the atherosclerotic plaques from the normal arterial wall. The instrument could produce either a longitudinal or a cross-sectional image of an artery. Later, the imaging capabilities were combined with a pulsed Doppler system to produce the ultrasonic duplex scanner, which is the basis for all ultrasound imaging instruments today.
A technology transfer agreement negotiated in 1974 between the UW Center for Bioengineering and a local company called Advanced Technology Laboratories, Inc. (ATL), marked the beginning of the development of a series of ultrasound products that has made Bothell-based ATL one of the leaders in the field of diagnostic medical ultrasound systems in the world today.
In early 1996, the UW and ATL unveiled plans to develop an ultrasound diagnostic instrument small enough to hold in the hand, for use on battlefields or in disaster situations where victims require immediate assessment of their injuries.The $12.6-million project is the largest collaboration ever between the UW and a Washington firm to develop a new product.
The hand-held instrument will be dramatically smaller than current high-performance devices, which weigh between 350 and 600 pounds. The goal is to develop a portable device that can be taken into the field to quickly diagnose life-threatening conditions for which treatment must be initiated within a certain limited time period. An ultrasound exam could reveal, for example, if body organs are distorted because of internal bleeding, or if, and where, shrapnel has been driven into the body.
The new instrument holds significant commercial potential and the promise of a major expansion of the diagnostic ultrasound market. Key players in the project from the UW include Lawrence Crum, a principal physicist with the Applied Physics Laboratory, who also holds faculty appointments in bioengineering and electrical engineering; Steve Carter and William Shuman, both with clinical appointments in the UW Department of Radiology; Brent Stewart, director of Diagnostic Physics; and Roy Martin, of anesthesiology and bioengineering. Leading the ATL team are Jacques Souquet, senior vice president, and Lauren Pflugrath, senior director of systems engineering.