Veterinary nuclear medicine can play a vital role in the diagnosis and therapy of a range of diseases and injuries that affect our four-legged friends. Tim Falk reports.
The word ‘nuclear’ does not evoke many positive associations for most people, usually triggering images of mushroom clouds in the south Pacific, catastrophic power plant meltdowns or even those mutant three-eyed fish on The Simpsons.
But tack the word ‘medicine’ after nuclear and you create something far removed from these negative images: a relatively new technique that is changing the way we diagnose and treat a range of conditions that affect our dogs.
“Veterinary nuclear medicine is still in its infancy in Australia and New Zealand,” says Professor Max Zuber. “There’s little nuclear medicine taught in veterinary schools and the overall availability of facilities is limited to a few university veterinary hospitals and a handful of equine and small animal practices.”
Despite this, nuclear medicine is a growing field. “Nuclear imaging in experienced hands can become the first choice in diagnostic tests for difficult cases, such as lameness problems in large-breed dogs and greyhounds. And the scanning procedure itself is much faster,” says Professor Zuber.
What’s involved?
Dr Deepa Gopinath is a small animal vet at Sydney’s Gladesville Veterinary Hospital, a referral centre for nuclear medicine. Dr Gopinath says there are two aspects to nuclear medicine, or scintigraphy, in veterinary science: nuclear imaging and treatment using nuclear medicine.
“Nuclear imaging involves administration of a low dose radioisotope by injection. The radioisotope is taken up selectively by the areas of interest and this uptake can be visualised and measured using a gamma camera. This diagnostic tool is useful in both diagnosis and quantification of certain disease conditions,” she explains.
“Treatment using nuclear medicine involves administration of a larger dose of a particular radioisotope that is selectively taken up by abnormal cells. The radioisotope destroys or slows the growth of these cells. In some disease conditions, a cure is achieved whilst in others, the aim is palliation and improved quality of life.”
Nuclear medicine is a non-invasive, non-surgical method of treatment and this has its own advantages with regards to avoiding the inherent risks of surgery and the post-operative recovery that accompanies general anaesthesia and surgery. “Combine this with the fact that for certain conditions, such as hyperthyroidism and thyroid neoplasia, the success rates of treatment with nuclear medicine exceed those of surgical treatment, and choosing nuclear medicine for these conditions is a no-brainer,” says Dr Gopinath.
Get nuked
It all sounds positive in theory, but what conditions can nuclear medicine help to combat in practice? Dr Gopinath says nuclear techniques allow vets to scan to “detect skeletal disease such as bone tumours, tumour metastases to bone from other sources, healing fractures that were otherwise undetected and, in some cases, developmental bone diseases in puppies. Technetium scanning can also aid in the diagnosis of thyroid tumours in dogs as well as metastasis of these tumours.”
Nuclear medicine can also benefit our dogs’ feline counterparts, most significantly in the diagnosis and assessment of hyperthyroidism. “With particular respect to feline hyperthyroidism (a very common elderly cat disease), radioactive iodine treatment, when available, has made surgical treatment almost obsolete. Not only is the cost of nuclear medicine comparable to surgery, but surgery has the disadvantage of being invasive and of not effectively addressing the ectopic thyroid tissue (thyroid tissue where it’s not meant to be) that occurs in some cats,” Dr Gopinath explains.
Nuclear medicine is also used to palliate dogs with osteosarcoma, a bone tumour that affects mainly large and giant breed dogs. The traditional form of treatment is amputation of the limb followed by chemotherapy. However, some dogs are not good candidates for amputation, and chemotherapy usually carries with it a greater risk of side effects.
“From the view of diagnosis, nuclear medicine techniques can detect certain diseases before other diagnostic techniques can,” says Dr Gopinath. “Nuclear scanning is used to localise the cause of lameness in animals when orthopaedic examination and other imaging techniques such as radiographs and CT scans may not provide an answer.”
Is there an element of risk?
“It’s fairly common knowledge that radioactive material can pose health problems, so health and safety precautions need to be taken when using nuclear imaging for both patients and people working with or around radiation,” Professor Zuber says.
“Any nuclear medicine facility should be housed in an isolated area and pets need to be housed in special cages. The discharge of animals to their owners can only occur when it’s deemed safe depending on the amount of radioactive exposure.”
From a financial standpoint, a thyroid or bone scan can cost around $600-$800, so nuclear medicine is not affordable for everyone. Other disadvantages include the fact that patients require sedation for the scan to take place — usually a very low risk in healthy animals — and that the availability of nuclear medicine is limited mostly to large cities.
However, despite these downfalls, nuclear medicine is still changing the face of veterinary care. “The role of nuclear medicine in vet practice in the future is likely to centre on developments of techniques to diagnose and treat pet cancers that mimic those seen in humans,” Professor Zuber says. The advances seen in human cancer diagnostic imaging with PET scanning are only just starting to filter through into use in animals.
Nuclear medicine, Dr Gopinath says, is helping to improve the lives of pets here and around the world. “Having a non-invasive, effective treatment option for certain diseases in our pets means that we can improve the health, lifespan and, most importantly, the quality of life of those pets without the risks of surgery and general anaesthesia, or the hassles of daily medication,” she says.
Nuclear medicine vs X-rays
How does nuclear medicine compare to X-rays? In nuclear medicine, the radiation is inside the person shining out and is detected by a gamma camera. In an X-ray, the radiation is shone through from the outside by a machine and a photographic film on the other side detects what passes through the body.
Answers to this and a number of other frequently asked questions about nuclear medicine can be found on the Gladesville Veterinary Hospital website: www.gladesvillevet.com.au
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