What CT can do for the horse with head disease

Diagnostic imaging of the equine head using 2-dimensional imaging poses significant limitations due to the complex anatomy and superimposition of the internal structures [1]. These result in a low sensitivity and specificity [2,3], and limited diagnostic ability. Conventional radiography also results in marked inter- and intraobserver variation in the interpretation of the radiographs, even with diagnostic quality images using modern digital radiography systems, and many veterinarians in general practice struggle with acquisition and interpretation of images.
By virtue of the cross sectional nature and reconstruction possibilities, computed tomography (CT) imaging offers more diagnostic information than the traditional 2-dimensional systems. This enables imaging of greater anatomical detail, with a wide range of tissue attenuation and has the potential to eliminate the confusion that results from superimposition of surrounding structures.
Computed tomography is based on x-ray technology. As the patient moves through the coil of the CT unit, a circular x-ray tube rotates around the patient’s head emitting x-rays. The radiation passes through different tissues at multiple angles to become either absorbed or attenuated (weakened), with remaining penetrating radiation to impact on a detector mounted on the same rotating frame as the x-ray generator, directly opposite. The signal is then processed by the computer to create a transverse image (‘slice’), represented using a greyscale image. The intensity of the colour represents radio density and is quantified and expressed in Hounsfield Units. This scale corresponds well to tissues of different density, and can differentiate between osseous tissues of different density such as bone and dental tissues but also between some (but not all) different soft tissues, with a greater sensitivity than standard radiography techniques. […]