Computed tomography and magnetic resonance imaging

Until a few years ago, diagnostic imaging for guinea pigs was limited to radiography (x-rays) and ultrasound. Although these are still very useful and widely used diagnostic tools, there are now far more advanced diagnostic imaging methods, such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), that are being more commonly used in guinea pig medicine and can be used to accompany radiography and/or ultrasound, or in some circumstances as a first line diagnostic measure.

CT, also known as CAT scanning, is a non-invasive imaging modality that uses x-rays to scan and create cross-sectional pictures of the animal which can be used to evaluate anatomy, function and pathology of many structures.

In guinea pigs, CT is particularly useful for viewing bony changes, such as those associated with advanced dental disease.

A CT scanner is a large box-like machine with a short tunnel or hole running through the centre. Your guinea pig will be placed on the examination table which then moves in and out of the tunnel.

The x-ray tube and electronic x-ray detectors are located opposite each other in a ring, called a gantry, and rotate around your guinea pig to create the scan image.

The CT scan is controlled from a separate room, where the information is processed and from where the veterinary team can monitor your guinea pig.

MRI is also a non-invasive imaging modality that scans the guinea pig using a magnetic field to produce high-quality images of the animal which can be used to evaluate anatomy, function and pathology of many structures. Unlike a CT scan, it does not use any x-rays.

In guinea pigs, MRI is usually used to look at soft tissue structures, including organs within the body, and is especially useful when diagnosing tumors.

An MRI scanner consists of a box-like machine with a tunnel through the centre that is open at both ends. Your guinea pig will need to be sedated or anesthetized to keep it immobilized, then it will be placed onto a motorized table in the center of the scanning tunnel. The table then moves inside the machine allowing the magnets to scan the body and create an image. In order for the image to be diagnostic and not blurred, the guinea pig must stay totally still, and this is why sedation or anesthesia is generally required.

An MRI scan relies on a strong magnetic field to move around and react with different atoms within the body to create the image.

The operator is located in a different room, and the veterinary team will also monitor your guinea pig from here.

MRI scanners are very noisy which is another reason why your guinea pig is very likely to be sedated or placed under general anesthesia, and it can take around half an hour to complete.

• Tumors, especially brain tumors.
• Abscesses within the body/skull.
• Fluid within the tympanic bullae or the ear (inner and middle ear disease).
• Tumors within bone or the chest/abdomen.
• Central nervous disease, such as epilepsy.
• Assessing the vertebral column.
• Upper respiratory tract disease.
• Dental disease and the extent of it.

CT scanning is normally the technique of choice for assessing the skull and calcified structures, whereas MRI is mostly used for evaluating soft tissue.

During the scanning process of both CT and MRI, your guinea pig must stay totally still to get a good diagnostic image. Therefore, to ensure your guinea pig is immobile during the procedure, your veterinarian will need to either sedate or anesthetize your guinea pig. General anesthesia is usually required, even in the most relaxed and well behaved guinea pig.

The viewing of both CT and MRI scanning can be instant as the scan is shown on a screen as it is being taken. However, you may need to wait for a radiologist to view and assess the scans before any results are given to you, which may take a few days.

CT and MRI scanning are now widely available through referral practices or visiting scanning companies. Although still expensive, now that they are more widely available and used, the costs have dramatically reduced in the last few years, making these services much more readily available to guinea pig owners, the vast majority of who may not have insurance.

Cost will vary significantly between veterinary practices and different areas of the country, but as an average figure, you should expect to pay anything between £500 and £1500 for a CT or MRI scan.

Insurance companies may cover the cost of CT and MRI scans, but you will need to either speak to them or ensure you have read your policy documents, including the small print, to know exactly what you are and are not covered for. If your guinea pig does not already have pre-existing exclusions on its policy relating to the reason they are being scanned, the scan has been recommended by a veterinarian for a specific medical problem, and you do not have any exclusions on the policy for advanced imaging, then there isn’t a reason why your insurance company should not cover your guinea pig for CT and MRI scanning.

You should call your insurance company before going ahead with any CT or MRI diagnostic scanning if you are in any doubt about your current cover. They will give you all the information you need about what is and isn't covered; they will also give you confirmation that you are covered.