Anyone who has ever known a pregnant woman has probably seen the ultrasound photos of the growing baby. Doctors use these ultrasounds to detect any developmental problems with the fetus, calculate the accuracy of the due date, and even determine the gender of the baby. Although this is a common function of ultrasounds, ultrasounds do have many other uses including being used to observe blood flow in the body, to locate tumors, and to observe the joints in the body. So how exactly does an ultrasound work?
The technology used by ultrasounds is similar to the SONAR used by submarines. It is also similar to the technology used by bats and dolphins to navigate and to communicate. The ultrasound machine has several parts. First, the transducer probe is used to emit high frequency sound waves into the body. The shape of the probe determines how much of the body can be seen. Some probes are also meant to be inserted into the body (for example into the esophagus or vagina) to get a closer view of an internal organ.
Second, the Central Processing Unit (CPU) is basically a computer that sends currents to the probe and does the calculations to process the data received from the probe. It then forms an image onto a monitor and stores that image. The monitor is basically the same as a computer monitor. Finally, the machine also has a keyboard and mouse that can be used by the technician to type notes and take measurements. Some machines may also have a printer, which is the source of those baby pictures we are all so familiar with.
During an ultrasound examination, the probe is placed on the body or inserted into the body. The probe then emits high frequency sound pulses into the body. The sound pulses hit boundaries between different types of tissues, for example between muscle and bone. Waves are reflected back to the probe as they hit these boundaries. Other waves continue farther on, until they, too, encounter a boundary. When reflected back, the waves are relayed to the computer which calculates the distances and then uses these calculations to display a two-dimensional image on the screen.
Different kinds of ultrasound can be used for different purposes. Three-dimensional ultrasounds are useful in detecting tumors and breast lesions and in examining the prostrate. The probes are used to take several 2-D images. These are scanned into the machine and the computer puts them together to create a 3-D image.
Doppler ultrasound uses changes in the frequency of the sound waves. With this information, the ultrasound can tell the motion of an object. If the frequency gets higher, the object is moving toward the probe. If the frequency drops, the object is moving away. With this technology, doctors are able to measure blood flow in the heart and arteries.
Since it does not use radiation, ultrasound is considered a safe alternative to an x-ray. Also, the ultrasound is smaller than other medical equipment (for example MRIs), so it is convenient to move and store. For these reasons, medical science is finding more and more uses for the ultrasound machine.