Ultrasound machines work by emitting very high frequency sound waves at 3.5 to 7 MHz, or megahertz. Sound waves change wavelength as they cross the line between mediums. With an ultrasound machine, a single beam of sound is emitted into the desired area and the sound is recorded. In turn, the sound is reflected off boundaries within the body. The result is a scan of the areas that the beam passed through. Several types of ultrasound machines are used to identify the information needed to support obstetrical and gynecological diagnosis.
Transvaginal Scans
In a transvaginal scan, the procedure is conducted by placing a probe in the vagina. This method normally yields detailed information and clearer images in the early stages of pregnancy and in obese patients. Better images are the result of the head of the scan being situated in close proximity to the uterus and as a result of a higher frequency used in the transducer. The heartbeat of the fetus can be observed clearly as little as 6 weeks into the pregnancy. Vaginal scans have become highly valuable in the early diagnosis of ectopic pregnancy or fetus planted outside the uterus. According to Dr. Joseph S.K. Woo of Obstetric Ultrasound, in the first three months of pregnancy, fetal abnormalities are also diagnosed using the vaginal scan.
Doppler Ultrasound
Mainly used to detect fetal heart rate, Doppler ultrasound has been used for a long time. In recent years, further developments have enabled its application in obstetrics in many areas, such as assessing fetal health, the progression of pregnancy and the restriction of intrauterine growth and in the diagnosis of cardiac abnormalities. Blood flow traits in fetal blood vessels can be examined with the Doppler's flow velocity waveforms. A problem in the fetus is indicated by diminished blood flow depicted through the use of color flow mapping. Fetal cardiac and blood vessel defects have also been assessed using this method. According to the Radiological Society of North America, obstetric ultrasound cannot identify all fetal abnormalities, so pregnant woman may have to undergo additional testing.
3D and 4D Ultrasound
3D ultrasound can provide three-dimensional images of what is being scanned. The transducer takes a series of pictures of the subject. The pictures are processed and presented by a computer as three-dimensional images. The computer operator can also obtain certain views that are not normally available using a 2D ultrasound scan. Parents are often impressed by the quality of the 3D images. However, 4D is one of the latest ultrasound systems providing clearer images at high resolution. According to OBGYN.net, not only can parents see their baby in 4D sonogram, they are able to experience a bond with the unborn child due to real-time movements in fetal images.
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