What is Computed Tomography (CT)?
Computed tomography (CT) images are formed by a xray generator and detector rotating around the patient. The resulting information can be viewed as cross-sectional slices which can be set up in any direction the viewer wishes.
CT provides excellent bony detail and provides more soft tissue detail than standard xrays. Unlike xray images where the anatomy is superimposed, CT images avoid superimposition of anatomy; this is particularly important in a complex area such as the head, where superimposition makes interpretation of xrays challenging.
CT scans are very quick to run (up to a couple of minutes), however the preparation and positioning of the patient takes time. Additionally, if the examination is performed under standing sedation (generally examination of the head), any movement will compromise image quality so repeat scans may be required.
CT in horses
The head is the area of the horse that most commonly undergoes CT examination and this can normally be performed in a standing, sedated horse, and is generally a very safe and well tolerated procedure. CT of the head is extremely useful for the investigation of dental disease and sinus or nasal disease. Other indications for CT examination of the head include headshaking and assessment of trauma/fractures
CT of the neck and limbs can be performed in anaesthetised horses; the precise regions which can be imaged depends on the size of the horse and the diameter of the bore of the CT machine (the hole in the polo!). CT technology is evolving rapidly and some machines allow imaging of the lower limbs in the standing, sedated horse.
CT of the thorax (chest) and abdomen (belly) can be performed in small ponies and foals, again under anaesthesia.
My horse is coming to Bell Equine for a CT scan, what should I do?
- If your horse is insured, you should inform the insurance company that we intend to undertake a CT examination and, where appropriate, check that the insurers are prepared to cover the cost of this examination. Some insurers will require a report from your vet stating why the procedure is necessary. Wherever possible this should be done well in advance of your appointment date. You can download our guide for insurance claims for day-case appointments HERE.
- Please bring details of your insurance policy along to the appointment with you (ie company name, policy number and where possible, claim reference).
- Please bring your horse’s passport with you to the appointment.
- Your horse can eat and drink as normal prior to the procedure (unless we advise you otherwise).
- Be prepared to wait or feel free to leave your horse with us for the morning / afternoon – although the scan itself is quick, the preparation time and time required afterwards for your horse to wake up from the sedation means that you horse is likely to be with us for 3-4 hours.
CT scanning – the procedure
- Your horse will be sedated for the CT scan. In order to be able to sedate your horse easily and safely, and avoid multiple injections, we will place a catheter into the vein on the neck. Depending on the season and breed of your horse, this may require a small region of hair to be clipped.
- Generally, if you wish, you may stay with your horse while the catheter is placed and until he / she goes into the CT room. At this stage you will be asked to wait in reception as owners cannot be in the room when the scan takes place due to the risks of unnecessary radiation exposure to humans.
- Your horse will need to be sedated for the scan; if you know of any reason why this cannot be done safely or if you know of any problems that the horse has previously encountered when being sedated, then please inform us prior to the appointment.
- The scanning process is very quick (less than 2 minutes) but the preparation to ensure it is safe for your horse; to get your horse in position; to ensure the images are of high enough quality and to make sure your horse is ready to travel after the procedure can take up to 3-4 hours. Most horses will be discharged on the same day as the procedure.
- In a small number of horses, sedation may predispose them to mild colic. If your horse is prone to colic, it might be prudent to feed a wet/laxative diet for 24 hours or so before the scan after your horse returns home. If feasible, walking exercise can also be helpful to promote gut motility.
- You should be given an approximate time when your horse should be ready to leave the clinic once we have completed the scan and checked to see that we have images of diagnostic quality. Arrangements to collect the horse can be made at the time.
- Due to the large amount of information collected during the procedure, it is unlikely that you will receive any results before your horse is discharged. In most cases a full report will be produced within 2 working days and copies will be sent to yourself and your referring vet.
Potential risks
- As with any procedure, despite the use of sedation, some horses become wary during the procedure and very rarely will panic, possibly causing injury to themselves. All risks of this occurring are minimalised as far as possible and we ensure we are always prepared for any unforeseen circumstances.
- Intravenous catheterisation is a commonly performed and low risk procedure, however, occasionally horses will develop a small swelling (haematoma) at the catheter site after removal. This will normally reduce over the following days but topical anti-inflammatory gels may help. We will inform you if this happens following removal of the catheter, or please contact us if you notice it once your horse is back home.
- CT scans use X-rays and the amount of radiation used is more than an ordinary, conventional X-ray of the area being imaged; however, your vet will have made the recommendation to perform the CT scan knowing that the risks of the procedure are outweighed by the quality of the information it provides. In human medicine, CT scans are regularly used for diagnostic purposes and the radiation dose of 1 scan is equal to the natural radiation that we receive from the atmosphere over a period of approximately 3 years.
Equine CT is still in its infancy and it continues to reveal many new conditions that we are trying to learn more about. In order to research the applications of CT in horses, we are always interested in hearing how individual horses have fared after they have returned home from having a CT scan. We may contact you and your vet in the future to find out how your horse has got on.
Another important way of increasing our knowledge is by correlating the results of CT with surgical and post mortem examinations. If your horse has previously had a CT scan and undergoes surgery on the same area, we would be grateful to hear of the findings. If for any reason your horse has to be euthanased, then we would welcome the opportunity to perform a post-mortem examination of the scanned area. In this way we can further increase our knowledge and expertise for the benefit of horses in the future.
