A sector scanner with a small transducer footprint is required to image between the rib spaces and allow good flexibility to obtain the various imaging planes. A suitable video recorder should be able to scroll slowly and freeze on an image for closer study. Scanners which feature cine memory to provide a freeze frame of every image for the last few seconds allowing the whole heart cycle to be examined and which can be upgraded to include a doppler facility are preferable. The eye is the perfect organ for ultrasonic examination. It is made up of several tissues delineated by distinct interfaces some of which are curved producing special reflections enabling the operator to obtain an image of the eye which is easily recognisable.
Most examinations involve scanning across the cornea with the eyelids held open.
This avoids the necessity of clipping the hair from the eyelids and eliminates any attenuation of the sound waves by eyelid tissue. Also, the eye itself can be observed during scanning, facilitating the correlation of the ultrasonographic image with the orientation of the globe. In large animals, particularly the horse, there is less hair on the eyelids, and scanning may be performed with the eyelids closed in many cases. Following the instillation of local anaesthetic eye drops, a mound of contact gel is placed upon the cornea. This gel must be viscose to maintain its shape for as long as possible so that it can act as a stand-off despite the action of gravity.