Understanding the Terminology
The terms “ultrasound” and “sonography” are often used interchangeably, leading to some confusion. While they are closely related in the context of medical imaging, they refer to distinct aspects of the process.
“Ultrasound” refers to the high-frequency sound waves themselves, which are beyond the range of human hearing, generally exceeding 20 kilohertz (kHz). In medical imaging, these sound waves typically operate at much higher frequencies, usually in the megahertz (MHz) range. These waves are the fundamental component that allows for imaging inside the body.
“Sonography,” also known as ultrasonography, is the diagnostic medical procedure or technique that utilizes these high-frequency sound waves to create images of internal body structures. It is the application of ultrasound technology to visualize organs, tissues, and blood flow. The image produced by this process is called a sonogram, which is essentially the visual output of the sonography procedure. Therefore, while ultrasound is the tool (the sound waves), sonography is the method or practice of using that tool.
The Underlying Technology
The creation of an ultrasound image relies on the principle of sound wave reflection, similar to how sonar operates. A specialized device called a transducer emits high-frequency sound waves into the body. These sound waves travel through tissues until they encounter boundaries between different structures, such as organs, fluids, or bones.
When the sound waves hit these boundaries, some are reflected back as echoes to the transducer. The transducer then detects these returning echoes and converts them into electrical signals. A computer processes these signals, using the time it took for the echoes to return and their strength, to construct a real-time image on a screen. Different tissue densities produce varying echo strengths, which translate into different shades of brightness on the sonogram, allowing medical professionals to visualize internal anatomy.
Practical Uses and Roles
Sonography is a widely used diagnostic tool across many medical specialties due to its non-invasive nature and ability to provide real-time images without ionizing radiation. Common applications include monitoring fetal development during pregnancy, assessing blood flow through vessels, and examining various internal organs like the liver, kidneys, and heart. It can help diagnose conditions such as gallstones, kidney stones, and certain cancers, as well as guide procedures like biopsies.
The professional who performs these examinations is known as a sonographer. Sonographers are healthcare professionals specifically trained to operate the ultrasound equipment, acquire high-quality images, and often provide initial observations to physicians. They play an important role in patient care.