Information About Ultrasound Scans
Patients should visit the Ultrasound section to see details of how to prepare for the specific test they have been referred for. If you have a general enquiry about your appointment and would like to contact us via email please use our contact form.
How does Ultrasound work?
Clinical ultrasound uses brief pulses of energy transmitted as acoustic/sound pulses through body tissues at different rates, dependent on the density and stiffness of the tissue it passes through. Some of the sound pylses are scattered and some are reflected back (echoes) from different tissue surfaces or interfaces. The amount of back echoes is determined by the type of tissue and the velocity of the sound. Ultrasound scanners rely on the detection of the echoes to form an image.
Ultrasound uses sound pulses which are at a frequency too high to be heard by the human ear. These ' high frequency sounds" are produced by an ultrasound machine and pass into the body using a special probe/ hand held device. Depending on the density of the tissue which they meet these sound pulses are rebound back with varying intensity into the ultrasound machine via the same probe. The computer in the ultrasound machine analyses the varying strength of these returned pulses and forms a picture/image depending on the tissue or structure from which they have returned. For example water will appear black and bone will be bright. Other tissues will have varying degrees of grey.
Multiple pulses along successive scan lines are used and as the probe is moved relative to the object, the signals are stored and used to build a 2 D image. As the images are acquired and displayed at rates of several times a second, an effective 'real time' display is generated. The images are then stored on a video monitor from which they can be archived, printed or copied.
Ultrasound was first used to detect submarines during the WW 1. It is used by fishermen to detect shoals of fish. In the 1960' obstetric ultrasound was developed in Scotland by Prof Ian Donald and Prof Stuart Campbell. Since then it has been used to assess most organs of the body, eg solid abdominal and pelvic organs, liver spleen, pancreas, kidneys, uterus and ovaries. It is also used much in cardiac imaging.
Ultrasound, as used in imaging the organs of the body is a safe and very useful technique. It is non-invasive, does not require injections or other procedures to obtain useful pictures/images. It is however very operator dependant that is the production of satisfactory pictures/images depends much on the experience of the operator.
Most ultrasound examinations involve placing the hand held probe on the patients skin surface e.g. over the heart for cardiac examinations or over the abdomen for abdominal or obstetric examinations. Relatively new ultrasound techniques use very small probes which may be placed inside the body like endoscopy or even within a blood vessel as in intravascular ultrasound (IVUS).