Bedside ultrasonography (US) is rapidly changing the practice of emergency medicine. When used in an emergency, bedside US can help establish a diagnosis faster, improve patient outcomes, decrease the risk of unnecessary procedures, and even shorten a patient's length of stay.1,2 The importance of utilizing this new technology is well-documented and thoroughly studied. However, few emergency medicine PAs are certified to use US. PAs should recognize that bedside ultrasound is increasingly popular in many medical specialties and that appropriate utilization can directly benefit patient treatment and outcomes.
US was developed in the early 1940s based on the principles of sonar, and clinicians have utilized the technology for more than 6 decades.3 In 1941, Dr. Karl Dussik was the first to use US to diagnose brain tumors.4,5 However, it is Dr. George Ludwig of the University of Pennsylvania who has been dubbed "the father of ultrasound."4 In the late 1940s, Dr. Ludwig was the first to record and study the differences between sound waves as they traveled through tissues, organs, muscle, and gallstones.4 Following his research, the use of ultrasonography exploded and was quickly applied to many different medical specialties. When more compact and affordable machines became available in the early 1990s, bedside US was born. Emergency bedside US is now a mandated part of training for all emergency medicine physician residencies, as recommended by the American College of Emergency Physicians (ACEP).3,6
HOW ULTRASONOGRAPHY WORKS
US produces sound waves and receives echoes, which are then interpreted. Clinicians typically use a handheld transducer probe, which is moved directly over the patient, to capture images. The transducer probe works by emitting high frequency sound waves that enter the body and hit the boundaries between tissues. These sound waves are picked up by the probe and relayed back to the machine. The machine displays the pulses and echoes on the ultrasound image.
The modern ultrasound is based on the piezoelectric effect in which electricity is transmitted into the probe, vibrating crystals and leading to the emission of sound.7 These sound waves then travel into tissue, reflect off anatomical structures, and return to the ultrasound probe. The returning sound vibrates the crystals in the ultrasound probe, which transmits this energy into electrical impulses. In turn, these electrical impulses appear as a black and white picture—the ultrasonogram. Modern ultrasound technology uses B-mode imaging, also called 2D imaging, which is a gray scale of at least 256 points.7 The returning reflection can vary from strong signals that are hyperechoic (white) to no signal, which is anechoic (black). Certain anatomic structures are easily identifiable based on their echogenicity. For example, the bladder is anechoic, meaning it does not produce echoes, whereas gallstones and bone are hyperechoic (produce many echoes) and appear almost white on ultrasonogram (Figure 1). As technology advances, the quality of ultrasound imaging is rapidly improving.
