My vet recommends my pet has an ultrasound examination. What does this involve?
Ultrasound examinations, ultrasonography or echosonography, to use some of the terms, is an imaging technique in which deep structures of the body can be visualised by recording echoes of ultrasonic waves which are directed into the tissues. Ultrasound waves are considered to be entirely safe.
The principal involves directing a narrow beam of high frequency sound waves that may be transmitted through, reflected off or absorbed by the tissue toward which they are pointed, depending on the nature of the surface they strike.
As the beam strikes the interface or boundary between two tissues, some are absorbed and others are reflected back to the transducer which originally generated them. These reflected sound waves are then, via, computer technology, converted into electrical impulses which are finally displayed on a computer screen similar to a television screen. This is a ‘picture’ of the tissues under examination.
The technique is invaluable for the examination of internal organs and was first used in veterinary medicine for pregnancy diagnosis. However the technique is also extremely useful for evaluating heart conditions and also identifying size and changes in organs in the abdomen. It therefore has an important place in the diagnosis of cysts and tumours.
Does the technique have any drawbacks?
Ultrasound examinations are of little value in the examination of organs that contain air. Ultrasound waves will not pass through air and therefore it cannot be used to examine the lungs.
Are there different forms of ultrasound?
Depending on the images produced, ultrasound can take various forms. In veterinary work B-mode ultrasound is the most usual. This gives a two dimensional picture of the organ scanned. M-mode is also used. This is a type of B-mode in which the movement of the object scanned is displayed. This is used for the evaluation of heart function and viability of foetuses in utero.
Doppler ultrasound is a further advance in the technology. Measurements and a visual record are made of flow and velocity in the vessels under examination. The technique is common in cardiology examinations.
Will my dog have to be anaesthetised?
The great advantage of ultrasound Is that anaesthesia is usually unnecessary. The technique is non-invasive but does involve clipping an area of hair and applying a water soluble jelly so that good contact can be made between the probe and the skin. The technique is totally painless and most animals will lie quite comfortably while the scan is being carried out. Occasionally if very frightened or fractious a sedative may be necessary.
Is the technique affordable?
The cost of each scan has to cover capital costs and maintenance as well as the employment of trained personnel in order to interpret the images. Its value, particularly with pregnancy diagnosis, evaluation of the size and normality of internal organs, evaluation of heart function, blood flow and examination of structures within the eye, coupled with the fact that even sedation is seldom necessary makes the cost very well worthwhile.
