An ultrasound probe, also known as a transducer, is a medical diagnostic device that emits ultrasound waves into a patient's body and transmits data to a computer to produce an internal image of the body, known as a sonogram. Ultrasound waves bounce off of tissue masses and boundaries in the body, and these echoes are recorded by the ultrasound probe and interpreted by the computer, which then creates the sonogram on a monitor. The ultrasound probe is generally placed directly on the patient's body and moved over the area to be viewed. Since water is a good conductor for sound waves, a water-based gel is usually placed on the patient's skin to help facilitate movement of the ultrasound waves, and patients undergoing obstetric ultrasound are usually asked to arrive for the test with a full bladder.
Quartz crystals in the ultrasound probe change shape and emit ultrasonic waves when they are supplied with an electrical current. These sound waves bounce back from the body and hit the quartz crystals, which then produce and electrical current that the probe sends to the computer. Variations in the current help the computer "see" shapes and masses inside the body. This electrical current is what the computer uses to create the sonogram.
Ultrasound probes come in varying shapes and sizes for use with different areas of the body. The most common types of probes are used externally and are about the size of a bar of soap, and are generally flat or slightly curved on the transmitting end. Vaginal ultrasound probes are a special type of probe used during early pregnancy to detect the presence and location of a fetus. This type of ultrasound probe is inserted directly into the vagina in order to obtain an image of the uterus, and is longer and more slender than probes used on the outside of the body. Similar probes are designed to be inserted into the rectum or esophagus to view portions of the colon, prostate, stomach, and other internal organs.
There are numerous medical uses for ultrasound technology. Prenatal ultrasounds are perhaps the most widely-recognized kind of ultrasound test, but ultrasounds can also be used to diagnose circulation problems and heart conditions, detect tumors and blockages, and diagnose and treat kidney stones. Ultrasounds are relatively safe and carry no known substantial risk to the patient, but as with any medical procedure, care should be taken to avoid unnecessary procedures.