Use of cone‐beam computed tomography for advanced imaging of the equine patient

Abstract

Access to volumetric imaging modalities, such as magnetic resonance imaging (MRI) and computed tomography (CT), has increased over the past decade and has revolutionised the way clinicians evaluate equine anatomy. More recent advancements have resulted in the development of multiple commercially available cone‐beam CT (CBCT) scanners for equine use. CBCT scanners modify the traditional fan‐shaped beam of ionising radiation into a three‐dimensional pyramidal‐ or cone‐shaped beam of radiation. This modification enables the scanner to acquire sufficient data to create diagnostic images of a region of interest after a single rotation of the gantry. The rapid acquisition of data and divergent X‐ray beam causes some artifacts to be more prominent on CBCT images—as well as the unique cone‐beam artifact—resulting in decreased contrast resolution. While the use of CT for evaluation of the equine musculoskeletal anatomy is not new, there is a paucity of literature and scientific studies on the capabilities of CBCT for equine imaging. CBCT units do not require a specialised table for imaging and in some cases are portable for imaging in the standing or anaesthetised patient. This review article summarises the basic physics of CT technology, including how CBCT imaging differs, and provides objective information about the strengths and limitations of this modality. Finally, potential future applications and techniques for imaging with CT which will need to be explored in order to fully consider the capabilities of CT imaging in the horse are discussed.

Use of a novel helical fan beam imaging system for computed tomography of the distal limb in sedated standing horses: 167 cases (2019–2020)

“…These cone-beam volumetric imaging systems require higher dosages to image thick body parts and still maintain good image quality. 15,16 With the Equina scanner used in the present report, we found that it took 2 or 3 people to optimize CT scanning, with 1 or 2 people to handle the horse and 1 person to operate the scanner. Personnel wore lead shielding and dosimeters and followed radiation protection principles that were as low as reasonably achievable and approved by the regional office of radiation safety to remain in the CT room during scanning.…”

“…2 Cone-beam volumetric imaging has also been used for distal limb scanning. 3,4,14,15 However, the entire imaging study is affected if the patient moves during image acquisition, and cone-beam imaging is more likely to result in streaking artifacts, scatter and noise artifacts, and image distortion, compared with helical fan beam CT. 3,4,15,16 Helical CT systems developed for imaging of human patients can be used in standing horses. For instance, a helical fan beam system installed over a platform has been used to scan the distal limbs of horses.…”

The Role of Computed Tomography in Imaging Non-neurologic Disorders of the Head in Equine Patients

“…However, recent equipment and room modifications allow for the use of regular MDCT scanners in standing sedated horses. Additionally, specially designed cone beam CT units (CBCT) for imaging of standing horses are also available and use a pyramidal- or cone- shaped beam instead of the traditional fan- shaped beam of radiation in MDCT scanners ( 9 ). Strong sedation is needed for the CT examination in standing horses to reduce patient motion, and thereby reducing the risk of patient injury and equipment damage, avoiding general anesthesia make standing CT a lower risk procedure for the equine patient ( 10 ).…”

When radiography and ultrasonography are not enough: the use of computed tomography and magnetic resonance imaging for equine lameness cases

“…Due to the shorter scans time as compared with MRI, motion is less of a problem with standing CT, but is still an issue. [25][26][27][28][29] There are also differences between cone beam and fan beam CT systems. In a basic sense, fan bean CT collects thin slices of information and cone beam CT collects a volume of information.…”

“…Image quality is superior with fan beam CT, compared with the quality in cone beam CT, with fewer artifacts, better signal-to-noise ratio, better contrast resolution, and lower scatter (Figure 1). 26,30 However, cone beam CT can be more anatomically versatile in a standing horse. 25,26…”