What is ultrasound ?
Ultrasound refers to sound waves with a frequency above 20,000 MHz, above the human hearing range. Frequencies in the 2-10 MHz range are most commonly used (1 MHz = 1 million Hz). Ultrasonography (USG) is performed by transmitting a narrow beam of ultrasound into the body from a transducer, this sound is then reflected from the various tissues back to the transducer as echoes, which are then converted into an image on a monitor, which is then read by the sonologist.
How useful is it ?
Ultrasound is used for a variety of reasons - common indications include detecting well being of the foetus during pregnancy, diseases of the liver, kidneys, uterus, ovaries, prostate, urinary bladder, gall bladder, thyroid gland, eyes, and scrotum.
Measurement of blood flow velocity using ultrasound is also performed using Duplex scanners, which combine real-time ultrasonography and pulsed Doppler sonography.
How should I prepare myself ?
If an abdominal scan has to be performed, you should reach the sonography department on an empty stomach. Some sonologists do not mind if the patient has a couple of glasses of water prior to the scan. Breakfast and even a cup of tea or coffee should be avoided.
If the pelvis or lower abdomen is to be scanned, you must not pass urine prior to the scan for atleast 1-2 hours, and your urinary bladder should be comfortably full while performing the examination.
Sonography during early pregnancy and of the KUB (kidneys and bladder) also needs a full bladder, fasting is not necessary.
During the mid and late pregnancy scans, fasting again is not required and your urinary bladder again should be comfortably full while the scan is done.
How much time does a scan take ?
An average scan could take between 10-20 minutes, however this time depends on the operator as well as machinery.
There is absolutely no risk related to ultrasound scanning. No long term biological effects have been detected with the long term scanning effects of ultrasound.
Benefits during pregnancy.
Ultrasound is the imaging modality to check the well being of the fetus during pregnancy.
During the first trimester, it is helpful in detecting the presence of an intra uterine pregnancy, the presence of heart beats in the early foetus, and to monitor progress of the early developing foetus in cases of bleeding (threatened abortion). It is also useful in detecting whether the pregnancy is intra or extra uterine (ectopic), or whether the pregnancy will continue or not (missed abortion - miscarriage).
In the second trimester, it is useful in detecting the position of the placenta, well being and accurate growth of the foetus, and in detecting congenital anomalies.
In the third trimester, it is useful in detecting position of the foetus, position of placenta, approximate birth weight of baby,and exact foetal age. An accurate ultrasound will reveal the presence of IUGR (growth retardation), small size of baby (small for gestational age), placenta previa (a low lying placenta), number of foetuses (twins or more !) and many types of congenital anomalies. Not all congenital anomalies can be detected on sonography, however, certain abnormalities of the spine, kidneys and other vital organs can be picked up