The world of veterinary diagnostic imaging has moved on enormously since the day when we had only grainy film radiography and ‘snowstorm’ ultrasound at our disposal. When I first graduated as a vet (and we’re not talking ancient history here!) I rarely took X-rays in the field as the X-ray machine in its travelling case alone weighed 23kg – having to lug that in and out of your car a few times rather dented the enthusiasm! Plus you never knew until you got back to the practice whether you’d got the specific bit of anatomy you wanted in the picture and whether the exposure was exact enough to see what you were looking for. If the pictures weren’t perfect you faced another trip out to the rapidly-losing-patience client and another session of lugging the equipment in and out of the truck. Ultrasound was little better. Most practice scanners were purchased primarily to scan cattle for pregnancy and the probe was rarely of the correct frequency and the image quality rarely detailed enough to make much more of a judgement call than ‘big hole in tendon’. And you probably knew that from palpating it anyway!
The x-ray machine I have now is a LOT lighter, but best of all it’s a digital system and the images can be viewed on a screen just seconds after they’re taken. This saves time and money meaning that fewer images need to be taken to ensure an optimal view and the images can be manipulated to enhance important areas. Diagnoses can often be reached on the spot and in cases where an expert opinion is required the images can be whizzed across the country, or even the world, in seconds.
Similarly with the new ultrasound machines there is a different frequency probe for tendon scanning and reproductive scanning and the image quality is hugely improved. No more snowstorms! Best of all the portable machine I have is small, light and can run without a power supply.
Most people will be familiar with radiography and ultrasound but there are now several new ways of looking inside horses which you may be less familiar with.
NUCLEAR SCINTIGRAPHY (BONE SCANNING)
Bone scanning involves injecting the horse with a radioactive isotope (usually Technetium-99), waiting for a couple of hours then scanning the horse’s body (or whichever part of it you’re interested in) with a gamma camera which detects radiation. The technetium is taken up by molecules in the horse’s body which are used in bone remodelling so the resulting scan shows areas where there are active inflammatory bone processes occurring. This is useful when changes have been seen on x-rays but it is not apparent whether you are looking at an old or an active lesion. It is especially useful for pelvis/sacro-iliac/back problems where it is very hard to get an X-ray picture.
Scintigraphy is also useful for the less-than-cooperative horse as a screening procedure. It is often easier to take to locate a lameness in a fractious horse by scinitigraphy than by repeated nerve/joint blocks!
Horses remain radioactive for 48hrs after the scan and must be stabled in isolation for this time. All their urine, dung, bedding and uneaten food is also considered radioactive and must be disposed of accordingly.
CT (Computed Tomography) SCANNING
The biggest problem with CT scanning is getting the horse in the machine! These scanners look like the big white tunnels that you see in human hospitals (most of them are ex-NHS) but as you can imagine you can’t just ask the horse to lie down on the trolley whilst you slide it into the machine! They are basically a modified X-ray machine which takes sequential slices through the patient which can be examined slice by slice or reconstructed into a 3D picture. They are hugely useful for heads – partly because you can sedate a horse and put its head in the tunnel fairly easily and partly because heads are so difficult to X-ray. I have sent horses for CT scans for diagnosis of sinusitis, tooth root abscess, intra-cranial tumours and assessment of structures involved in skull fractures.
You can also use CT scans very effectively to diagnose lower limb lamenesses, especially where the problem lies within the hoof; but the horse will need a GA for leg CTs which does add to the time, cost and risk involved.
STANDING MRI (Magnetic Resonance Imaging)
This is a very useful tool used especially for foot lamenesses. Prior to the availability of MRI any foot pain in the area of the mid-foot backwards that couldn’t be diagnosed by X-ray tended to be termed Navicular Syndrome or more latterly Palmar Foot Pain. Now most of these cases can be accurately diagnosed. A lot can be attributed to damage to the deep digital flexor tendon (DDFT) where it attaches to the pedal bone or to injuries of the collateral ligaments of the coffin joint.
As the name implies the horse remains standing (sedated) for this procedure. The foot is placed into a strong magnetic field. Pulses of radiofrequency are passed through the tissues and returned as radiowaves which a computer can then interpret and turn into an image. For obvious reasons the horse must have its shoes removed for this procedure and it is fairly slow – it can take several hours – but it is a very good way of looking at bone and especially soft tissue in inaccessible areas .
So there you have it, a quick gallop through some of the flashy new tools that we have at our disposal to locate, image and diagnose lamenesses. All are expensive and, especially if your horse needs X-rays as well, or more than one of the above, you can rapidly approach your insurance limit leaving little or no money for the treatment of the condition you’ve discovered. Fine if the recommendation is rest, not so good if your horse requires surgery. It is important to be guided by your vet as to which line of investigation is likely to bear the best results and how to use your insurance allowance most efficiently.
It is worth noting that whilst most insurers will cover 100% of the cost of scintigraphy and CT scanning not all will pay for the full cost of MRI.
Picture credits: DR machine – author; CT and Scintigraphy scans – Rainbow Equine Hospital; MRI scan – Hallmarq Imaging