Ultrasound imaging is based on the same principles involved in the sonar used by bats, ships and fishermen. When a sound wave strikes an object, it bounces back, or echoes. By measuring these echo waves, it is possible to determine how far away the object is and its size, shape and consistency (whether the object is solid or filled with fluid).
In medicine, ultrasound is used to detect changes in appearance of organs, tissues, and vessels or detect abnormal masses, such as tumors.
In an ultrasound examination, a transducer both sends the sound waves and receives the echoing waves. When the transducer is pressed against the skin, it directs small pulses of inaudible, high-frequency sound waves into the body. As the sound waves bounce off of internal organs, fluids and tissues, the sensitive microphone in the transducer records tiny changes in the sound’s pitch and direction. These signature waves are instantly measured and displayed by a computer, which in turn creates a real-time picture on the monitor. One or more frames of the moving pictures are typically captured as still images. Small loops of the moving “real time” images may also be saved.
Doppler ultrasound, a special application of ultrasound, measures the direction and speed of blood cells as they move through vessels. The movement of blood cells causes a change in pitch of the reflected sound waves (called the Doppler effect). A computer collects and processes the sounds and creates graphs or color pictures that represent the flow of blood through the blood vessels. For most ultrasound exams, the patient is positioned lying face-up on an examination table that can be tilted or moved.
A clear water-based gel is applied to the area of the body being studied to help the transducer make secure contact with the body and eliminate air pockets between the transducer and the skin that can block the sound waves from passing into your body. The radiologist then presses the transducer firmly against the skin in various locations, sweeping over the area of interest or angling the sound beam from a farther location to see an area of concern better.
Doppler sonography is performed using the same transducer. When the examination is complete, the patient may be asked to dress and wait while the ultrasound images are reviewed. Ultrasound examinations are painless, fast and easily tolerated by most patients.
After you are positioned on the examination table, the radiologist or sonographer will apply some warm water-based gel on your skin and then place the transducer firmly against your body, moving it back and forth over the area of interest until the desired images are captured. There is usually no discomfort from pressure as the transducer is pressed against the area being examined.
If scanning is performed over an area of tenderness, you may feel pressure or minor pain from the transducer.
Ultrasound exams in which the transducer is inserted into an opening of the body may produce minimal discomfort.
If a Doppler ultrasound study is performed, you may actually hear pulse-like sounds that change in pitch as the blood flow is monitored and measured. Once the imaging is complete, the clear ultrasound gel will be wiped off your skin.
After an ultrasound examination, you should be able to resume your normal activities immediately. Instructions to the patients Prior to starting the procedure, the patient will usually be given a hospital gown to wear.
Altough no special preparations for USG are required but it is better to come on overnight fasting state or atleast 6hours fasting in cases of liver and Gall bladder pathology.
In cases of Renal doppler overnight fasting or atleast 6hours fasting is preferred as bowel gases may obstruct the study. For USG pelvis and KUB, a full-bladder is required for which you may be asked to drink up to six glasses of water two hours prior to your exam and avoid urinating so that your bladder is full when the scan begins.
For small parts (thyroid, scrotum, breast, joints and bone), no preparation is necessary. You may need to remove all clothing and jewelry in the area to be examined.
You may be asked to wear a gown during the procedure.
Other preparation depends on the type of examination you will have. For some scans your doctor may instruct you not to eat or drink for as many as 12 hours before your procedure.
Please get all the old x-rays, sonography films along with the other papers, operative notes, discharge card etc. relevant to the case