Ultrasound technology can provide real-time images of unborn children.
An "ultrasound" refers to any noise beyond the upper limits of human hearing. Diagnostic sonography and obstetric sonography both use ultrasonic waves to image internal organs or a fetus during pregnancy. Since its development in the 1950s, sonography has become an important tool for diagnosing disease and monitoring fetal development.
History
The history of ultrasound can be traced back to the invention of Sound Navigation and Ranging, or sonar, during World War I. Sonar uses underwater pulses of sound to detect ships or submarines by picking up echoes. After returning from World War II, a Scottish professor based at the Glasgow University Department of Midwifery decided to adapt sonar for medical purposes after experiencing its use in the U.K. Royal Air Force.
Professor Ian Donald teamed up with Dr. John MacVicar, later professor of obstetrics and gynaecology, and a young technician named Tom Brown to produce the first working ultrasound machine. They achieved early success by successfully diagnosing an ovarian cyst in a woman who had previously been told she had stomach cancer. Development of the ultrasound continues to this day with 3D and even 4D sonography becoming available to doctors and pregnant women.
Physics
An ultrasound machine uses a transducer to both emit and receive ultrasonic waves. During a sonogram, very high frequency sound waves, around 3.5 to 7 megahertz, are sent into the body and reflected back or echoed to the transducer. Because the ultrasonic waves are reflected differently within the body as they strike different surfaces, not all waves come back at the same time. The information from the different echoes reflected back to the transducer is compressed to form a picture on a monitor by the ultrasound machine.
Undergoing an Ultrasound
During an ultrasound a clear gel is applied to the body to eliminate air pockets between the transducer and the area being studied. The sonographer or ultrasound technician then presses the transducer firmly against the skin, moving it over the area of the body to obtain the clearest image. During some ultrasound examinations, the transducer is inserted into a natural opening in the body. These internal procedures usually aim to study the heart, prostate or uterus and ovaries.
Limitations of Ultrasound
Ultrasound waves are disrupted by air or gas within the body and are not suitable for studying the bowel or organs obscured by the bowel. Bones cannot be penetrated by ultrasonic waves, making sonograms unsuitable for visualizing areas inside bone; on the other hand, this makes them ideal for imaging a fetus because of the lack of nearby bone. Overweight patients also pose difficulty as extra tissue weakens sound waves as they pass deeper into the body.
Benefits
Aside from internal sonography, most ultrasound exams are noninvasive and painless. Ultrasound exams are widely available and easy to use by specialized technicians, meaning doctors do not have to be present at each examination. Ultrasound, unlike X-ray imaging, does not use ionizing radiation and is better for examining soft tissue. It also allows doctors or technicians to see a real-time internal image of the patient, which is particularly useful in surgery.
Tags: ultrasonic waves, ultrasound machine, into body, reflected back, sound waves, within body
