Computer tomography (CT) for awake animals — is that possible and useful?

Computer tomography (CT) is a modern imaging method that provides highly detailed images of the body. It is often used in veterinary medicine, for example to examine the head, nose, spine, lungs or joints. Most animals will undergo anesthesia for a CT examination, however, in some cases, this can be avoided.

Thanks to modern CT techniques, certain CT scans can now also be carried out on awake animals.

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What is a CT and why is lack of motion so important?

Using X-rays, a CT creates many individual cross-sectional images, from which a three-dimensional image volume is calculated. For these images to be of good diagnostic value, the animal must remain as still as possible. Movements can severely impair image quality (so-called motion artifacts); even as little as normal breathing movements can sometime cause artefacts.

Early CT machines required relatively long scan times, which is why anesthesia was almost always required. However, modern high-speed CT machines can scan individual body regions in as little as “a few seconds” (Ohlerth & Scharf, 2007).

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When is a CT without sedation possible?

CT in Awake Animals is particularly possible if:

• The animal is calm and cooperative
• Only a short examination is required
• No painful fixation of any body parts is required
• Patients with a very high anesthetic risk should be examined

Examinations of the head, nose or sinuses as well as “short chest CTs” or sometimes "trauma CTs" are sometimes suitable, as these can be carried out very quickly (O'Brien & Thrall, 2018).

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What are the benefits of a CT without sedation or anesthesia?

CT studies in a conscious patient offer several benefits:

• “No risk of anesthesia,” particularly important for elderly patients or animals with life-threatening heart/lung diseases
• “Faster recovery” as no wake-up phase is required
• “Fewer drugs,” which may protect certain systems of the body
• “Shorter hospital stay”

Studies show that modern CT scans can be very diagnostically meaningful even without sedation for selected cases (Ohlerth et al., 2017).

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Are there also restrictions?

Yes. Not every animal and not every case is suitable for an awake CT. Sedation or anesthesia is still necessary if:

• The animal is very anxious or restless
• Pain prevents quiet positioning
• A longer or very precise examination is required
• Contrast medium must be administered under controlled conditions

The well-being and safety of the animal always comes first.

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How is an awake animal prepared for CT?

For a CT without sedation or anesthesia, the animal is gently positioned and kept quiet by trained personnel, sometimes using special devices (Oliveira et. al. 2011). Veterinarians make sure to keep stress as low as possible. In some cases, a quiet environment or a short period of familiarization may be enough to keep the animal relaxed.

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Summary

Thanks to modern technology, it is now possible to carry out certain CT examinations even “on awake animals.” This can be a gentle alternative to anesthesia, particularly for older or debilitated animals. Your veterinarian will decide individually whether a CT without sedation is appropriate — tailored to your animal and the diagnostic issue.

If a CT is recommended for your pet, don't hesitate to discuss your options with your vet.

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References:

• Ohlerth S, Scharf G. "Computed tomography in small animals — basic principles and clinical applications." "Veterinary Radiology & Ultrasound", 2007.
• O'Brien RT, Thrall DE. "Thoracic Computed Tomography in Dogs and Cats." "Veterinary Clinics of North America: Small Animal Practice", 2018.
• Ohlerth S, Dennler M, Poirier V. "Advances in CT technology and their impact on small animal imaging." "Veterinary Radiology & Ultrasound", 2017. • Oliveira CR, Ranallo FN, Pijanowski GJ, Mitchell MA, O'Brien MA, McMichael M, Hartman SK, Matheson JS, O'Brien RT. "The VetMousetrap: a device for computed tomographic imaging of the thorax of awake cats". "Vet Radiol Ultrasound". 2011 Jan-Feb;52(1):41-52. PMID: 21322386.

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