Digital or computerised radiography, while being available for a number of years in Australia, has in the last twelve months seen a rapid increase in popularity in equine practice. Digital radiography does not refer to the way the x-ray beam is made but to the way the image is processed. This modern technology is faster and cleaner, eliminating the requirement for ‘wet’ chemical processing and a darkroom.

Some of these new units are portable or mobile; others remain in a hospital just as in the human hospital environment. Equipment is very expensive. Although there are some relatively inexpensive units available, the images produced are of poorer quality and do not rival top quality wet processing techniques.

As images are stored in a computer they can be reproduced multiple times. Additional labels can be added, images flipped upside down or as a mirror image, made darker or lighter and magnified. Images can be stored on hard drive back ups, on DVD and on CD and can be emailed around the world. Clients can be provided with a copy of their horse’s x-rays without the fear of losing their pictures;, Contrary to early concerns images cannot be tampered with, e.g. chips erased, without leaving an indelible mark on the image, and a historical trail. Practices download all the original data and store it as a legal record: these protection systems were designed by the medical fraternity as digital radiography was introduced in human radiography.

Although digital radiography can produce beautiful pictures it requires skill and experience with the equipment and this takes time for your veterinarian to learn and time to get the job done; it is not an instant miracle. Poor technique produces poor results and non-diagnostic images. It also takes time to read images on a computer screen and this takes some acclimatisation for the veterinarian in addition to learning about the software system showing the images. No more use for light boxes in the practice although it is interesting that the human field still prints on special laser film creating a ‘film’ that looks is like the old style film but of much higher quality, many of its images including CT scans for ease and speed of reading. Film prints of digital images are also currently the repository requirement at thoroughbred auctions; developments are being made in this area.

A pre-purchase examination may include a radiographic exam. This may be of one or of a pair of joints as indicated by the clinical examination or a full set of 34 (‘thoroughbred yearling set’) or 42 (‘Hong Kong set’). An indication of findings may be given at the time but a good veterinarian will review the images on a quality computer screen and write his report back at the practice. It is too easy to miss changes in the field and is an unreasonable demand.

Vendors’ initial concerns that little problems will show up that wouldn’t have previously been found have not become an issue. Quality images are always essential in making a diagnosis and giving a reasonable prognosis for athletic ‘soundness’. In fact as we a see a little more detail and even soft tissue on digital radiographs veterinarians are able to be a little clearer about what is going on. What used to look like a small degenerative change at the front of a fetlock joint with ‘maybe’ a chip now looks like a chip; surgery that may not have been considered for such a case may go ahead with a more positive outlook. When a picture is clear a veterinarian can be more clear and positive in his diagnosis about a finding.

It is still important to remember that an x-ray image taken is only a ‘moment in time’. Changes on radiographs can happen very rapidly, e.g. OCD in young horses. While quality images reveal a clearer picture of what ‘is’ they are no protection against what will happen in the future.

Types of Digital Systems Used In Practice Two types of systems are in use. The first uses plates that look similar to old wet processing plates. Rather than containing film which is ‘exposed’ by x-rays to create the image these plates contain screens which store the image. When put into the computerised processor the computer reads ‘screen’ and stores the image on the hard drive, reproducing it for us to look at then immediately cleans the ‘screen’ by erasing the image data from it. Hey presto ready to use again. The second type of digital system essentially has the x-ray unit and a single plate connected directly by cables to the computer; the image pops up on this plate and is rapidly sent to the computer’s hard drive, again erasing the image information on the plate to allow its repeated use. Each type system has pros and cons. In experienced hands both systems are similarly very fast in comparison to wet processing. The first ‘computerised’ systems have very robust plates to hold its ‘screens’ and as the screens are used independently there is more freedom to work around the horse or at any distance from the computer. While the unit needs to very close by to a full screen (34–42 images), plates can be used at any distance from the processor so can be taken in the car and processed later. The second ‘direct’ systems have a computer and single plate that packs away and can be transferred between vehicles so is very portable. The unit must be right next to the horse and if the plate gets a kick and is damaged repairs are incredibly expensive, tens of thousands of dollars.

Sesamoid fragment with new bone changes in a two year old thoroughbred

Twenty year old Shetland with Chronic Laminitis after a hoof trim

SUSANNAH THOMSON HAWKE (BVSc Bachelor Veterinary Science, Bristol UK 1987)

Susannah Hawke is well renowned for her expertise in the area of digital x-ray in regards to Pre-purchase examinations, lameness diagnosis and digital radiography.

• MACVSc Membership Australian College Veterinary Scientists, by examination

• Surgery of Horses 1996 Graduate Diploma Animal Chiropractic

• Diploma In Racing with a Paper published on the radiographic management of shins to prevent shin soreness.