The VetMouseTrap™ holds a cat in
position for a CT scan.
Feline hyperthyroidism is the most common endocrine disease in cats. Cats with elevated levels of thyroid hormone can experience increased appetite, weight loss, vomiting and hyperactivity. The condition is usually diagnosed by symptoms and/or a blood test, and is commonly treated with the drug Methimazole.
Although computer assisted tomography (CT) has been shown to be a reliable alternative for diagnosis, in the past it required a cat be anesthetized prior to scanning. Anesthesia presents additional risk to hyperthyroid cats who often have several health issues, including heart disease and kidney disease.
Dr. Sarah Nemanic, assistant professor of radiology, and Dr. Jana Gordon, assistant professor of internal medicine at the OSU Veterinary Teaching Hospital recently completed a study that may help improve both diagnosis and treatment of cats with feline hyperthyroidism.
The study had several goals: to determine if awake cats can easily be imaged by a CT, to measure the effect of Methimazole on thyroid size and volume, and to see if a pre-treatment CT scan can predict drug dosage.
Participating cats received computer assisted tomography (CT) before and after treatment with Methimazole. Although hyperthyroid cats move around a lot, Dr. Nemanic was able to scan the cats without anesthesia by using a VetMouseTrap™, a padded, clear plastic tube with breathing holes or scan them in their cat carrier. The speed of the CT at OSU also made the process easier. “The head and neck of a cat can be scanned in 3-5 seconds,” says Nemanic.
The study demonstrated that CT is a useful way to image the thyroid glands of awake cats. “CT is the ideal imaging modality for the thyroid gland because the gland has iodine in it, and iodine is the contrast medium that is used for all contrast CT examinations. It makes the thyroid gland easy to see and measure. Also, CT has excellent spatial resolution, so it is a fantastic imaging modality for measuring size and volume,” says Dr. Nemanic.
Images taken in the CT before and after treatment with Methimazole confirmed that hyperthyroid cats have significantly larger thyroid glands than normal cats and that Methimazole treatment does not change the size of the thyroid gland but does significantly lower the brightness (attenuation) of the thyroid gland on CT.
