When you visit a vet with your pet, and they need further tests to diagnose problems within the body, they would usually have an x-ray (radiograph) or an ultrasound, to find out what is going on. These are normally completely adequate in giving the vet an answer diagnostically, however some situations can benefit from an MRI scan. It is especially useful for bone and soft tissue, and an MRI scan will give an amazing view of what is going on, in high detail. For this Pets4Homes article, we’ll look at what an MRI is, how safe it is, and types of conditions it can be used for.
Let’s start with what isn’t! It is totally different to a normal x-ray or ultrasound. These function by using a beam of energy, into the area that is being looked at, using x-ray or sound waves. The beam is then monitored to how changed and different it is, by the body tissues it passes through.
An MRI, which means Magnetic Resonance Imaging, uses an enormous and extremely effective magnet along with a radio antenna, that is linked to a state-of-the-art computer. So rather than x-ray or sound waves, the antenna sends a radio pulse into the body. They work exactly the same for animals as they do in human medicine.
This is where the scientific bit plays a part, and it’s all to do with the hydrogen atoms in the body. When the animal is in the MRI scanner and it is switched on, the magnet causes all the hydrogen atoms in their body to align within the magnetic field. Once this is achieved, the radio antenna sends a considerable radio pulse into the animal's body – this will cause the atoms to go back to their original state. Whilst this is happening they release energy in the form of billions of extremely weakened radio signals. These radio signals are collected by the antenna and in turn, the computer can then determine how the atoms are positioned giving an excellent, extremely detailed, image of the animal's tissues.
It’s all because of water! H2O (water) means there are two hydrogen atoms in each molecule of water. With every tissue in the body being full of water, this means all tissues can be extremely detailed. During the process of an MRI, the body is actually changed with quantum physics, and an image generated before all the atoms return to their normal position. It is because of this process that the computer is able to define an image of internal organs and structures, with complete accuracy.
Compared to other imaging types, an MRI scan is probably one of the safest. Unlike other techniques, there is no:
Traditional x-rays and CT scans use something called ionising radiation. This radiation can affect an animal in several ways including radiation damage, cancers and even cause abnormalities in unborn puppies and kittens.
None of the tissues are subject to any heat whilst imaging. In ultrasound, there is a small possibility of tissue damage occurring from prolonged and overdone ultrasonography from heat. Because the way it works, an MRI does not produce heat that can damage tissues in the body.
Not side effects exactly, but there are a couple of things that can be a risk.
If a human has an MRI scan they know they have to lay perfectly still during the process. Unfortunately, animals do not understand this concept and any movement can completely ruin the scan. Because of this, the animal will need anything from sedation to a proper anaesthetic. The animal will need to be kept still for up to an hour whilst scanning is performed.
Modern anaesthetic drugs are very safe and close monitoring also helps detect any problems with the anaesthetised animal, but there is always a small risk with any anaesthetic.
Any metallic object can cause major problems with an MRI, essentially because of the huge magnetic field that is generated with the machine. Any metallic objects would get pulled into the machine at incredibly high-speed. This means animals that have any sort of metalwork such as implants, plating, screws in their bones, cannot be scanned as it affects the image. There’s also a possibility the implant may be dislodged due to the magnetic force. Any electronic devices that have been fitted such as pacemakers, also will mean the animal cannot be scanned. Luckily the one thing that is not affected is ID microchips.
Because x-rays and CT scans will not give the definition or full information that vets needs in soft tissue cases, MRI will. The following conditions an MRI scan would be the gold standard:
So, you can see it can be used on many different types of disease and health issues, and with other information provide the vet with a really good idea and insight to what is going on with the animal.
MRI is extremely useful in a number of conditions with your pet. In itself the machine is quite expensive, so many practices deem them out of their budget. That said, if your pet needs an MRI scan, your vet can refer them to the nearest practice that has the equipment in place. If you think that this type of imaging could be useful for your pet, please discuss it with your own veterinary surgeon.