CT or X-ray: which reveals more in horses? [H&H VIP]
The world of diagnostic imaging is changing fast.
Most equine vets now use digital radiography rather than traditional photographic X-ray plates, while MRI and ultrasound scans have become routine.
Fewer diagnostic centres currently have access to computerised tomography, or CT. This high-resolution radiography development can produce images of a virtual “slice” of the region that is being examined.
In an X-ray of the foot of a horse, for example, taken from front to back, all the bone structures are superimposed upon one other. The resulting flattened image can be difficult to interpret. A CT scan, on the other hand, allows the vet to look at the same structures slice by slice.
Vets in Belgium and the Netherlands compared the X-ray results and CT scans of 30 horses suspected of having lower limb fractures to see which type of image enabled the most accurate diagnosis. They asked four experienced orthopaedic equine vets to interpret the necessary images, without allowing them
to confer.
The results, published in the EVJ, showed that agreement between the vets’ diagnoses was very good. The level of correlation between the two types of image, however, was not so impressive.
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Both imaging methods showed up most of the fractures, but the CT images appeared to reveal more tiny cracks around the main fracture and more fragments.
The horses were standing and weight-bearing for the X-rays, but the CT scans were carried out under anaesthesia. While it’s possible that the fractures were more “opened up” for the CT scans, this method was still judged to provide a better assessment.
The vets make the point, however, that both types of image are just a projected picture.
There is no substitute for surgical evaluation of the bone in the operating theatre.
