The terms “ultrasound” and “sonography” are frequently used interchangeably in everyday conversation, often leading to confusion about whether they refer to the same thing. While the two are intimately connected, they technically refer to different components of the medical imaging practice. This distinction is important for understanding the technology, the medical procedure, and the professional field involved in creating internal images of the human body.
Clarifying the Terminology
The fundamental difference lies in defining the tool versus the practice. “Ultrasound” refers specifically to the high-frequency sound waves utilized in the procedure, which are beyond the range of human hearing, typically in the megahertz (MHz) range. It is the technology itself, the physical tool that makes the imaging possible. The image produced by this technology is called a sonogram, which is the visual record of the sound waves’ interaction with the body’s tissues.
“Sonography,” or ultrasonography, is the name of the diagnostic medical procedure and the professional discipline that applies the ultrasound technology. It represents the act of using the equipment to perform a non-invasive examination for diagnostic purposes. The healthcare professional trained to conduct this examination, position the probe, and capture the images is called a sonographer.
How the Technology Works
The sonography procedure begins with a device called a transducer, which acts as both a speaker and a microphone. This handheld probe is placed on the skin, often with a water-based gel applied to eliminate air pockets that could interfere with the sound waves. The transducer emits rapid pulses of inaudible, high-frequency sound waves into the body’s tissues.
As these sound waves encounter different internal structures, such as the boundaries between fluid, soft tissue, and bone, they are reflected back to the transducer as echoes. The sound waves travel at different speeds depending on the density of the tissue they pass through. The transducer captures these returning echoes and converts them into electrical signals.
A sophisticated computer then processes the time it took for each echo to return and the strength of the signal. This data is used to calculate the distance and shape of the internal structures, creating the real-time, moving image displayed on the monitor.
Common Applications
Sonography is used widely in medicine because it is non-invasive, widely available, and does not use ionizing radiation, unlike X-rays or CT scans. This makes it a preferred method for sensitive examinations, particularly in obstetrics, where it is used to monitor a fetus’s growth and development during pregnancy. Its real-time imaging capability is also utilized for guiding certain medical procedures, such as biopsies or fluid drainages, allowing physicians to visualize the needle’s exact location.
The technology is applied extensively in cardiac imaging, known as echocardiography, to assess the heart’s structure, valve function, and blood flow patterns. Abdominal sonography is routinely used to examine organs like the liver, gallbladder, kidneys, and pancreas for abnormalities such as gallstones or cysts. Specialized Doppler ultrasound can also be used to visualize and measure blood flow and velocity within arteries and veins, making it an effective tool for diagnosing conditions like blood clots or narrowed vessels.