Computed tomographic evaluation of the distal limb in the standing sedated horse: Technique, imaging diagnoses, feasibility, and artifacts

Abstract

In several veterinary institutions, adjustments of CT machines have been made that allow for imaging of the standing horse. The risk of general anesthesia is eliminated and the shorter scan completion time reduces cost to clients. The objective of this retrospective, analytical study was to evaluate the technique, imaging diagnoses, feasibility, and image artifacts of multi‐slice helical CT of horses’ distal limbs acquired under standing sedation. The CT images of 250 horses of various breeds, aged 3–23 years, that underwent standing distal limb CT were evaluated. Three observers assessed the CT images for artifacts and inter‐observer agreement was calculated. Eighty‐six percent (95% confidence interval (CI), 81–90) of the scans were carried out on the forelimbs, while 14% (95% CI, 10–19) were of the hindlimbs. A total of 65% (95% CI, 59–71) of horses that underwent standing sedated CT had single imaging diagnoses. Seventy‐one percent (95% CI, 65–77) of the cases had unilateral lesions, 27% (95% CI, 22–33) had bilateral lesions and 2% (95% CI, 1–4) had no diagnosed lesions. The average CT acquisition time was 17.5 minutes (range = 15–20). The average number of acquisitions per horse was 1.7 (median = 1; range = 1–4). There was good to excellent agreement between all three observers for the presence of motion artifact in the metacarpo/metatarsophalangeal joints, identification of marked beam hardening artifact, mild solar/ skin dirt, and photon starvation artifact (kappa 0.61‐0.80). No complications were encountered. Standing examination of the distal limb achieved diagnostic image quality that was obtained with minimal acquisition attempts and in a timely manner.

Highlights of recent clinically relevant papers

“…This retrospective study by Nicoli Mathee and co‐workers in South Africa, France and Australia evaluated the technique, imaging diagnoses, feasibility, and image artefacts of multi‐slice helical computed tomography (CT) of horses' distal limbs acquired under standing sedation .…”

Computed Tomographic Evaluation of the Sagittal Ridge of the Third Metacarpal Bone in Young Thoroughbred Racehorses: A Longitudinal Study

“…Computed tomography (CT) of the distal aspect of the limb of standing sedated horses is becoming increasingly available worldwide [ 11 ]. Three-dimensional visualization of anatomical structures allows precise localisation and characterisation of abnormalities and facilitates objective measurements.…”

Findings consistent with equine proximal suspensory desmitis can be reliably detected using computed tomography and differ between affected horses and controls

“…[11][12][13]15 The use of CT in equine orthopedic diagnostic imaging and particularly soft tissue imaging has significantly increased in recent years. [16][17][18][19] Particularly due to the short acquisition time and the increased availability of standing CT units at the referral level, CT imaging may offer a valid alternative to MRI of the PSL. [18][19][20][21] However, descriptions of CT findings at the level of the PSL origin in horses with and without PSD in the current literature are sparse.…”

“…[16][17][18][19] Particularly due to the short acquisition time and the increased availability of standing CT units at the referral level, CT imaging may offer a valid alternative to MRI of the PSL. [18][19][20][21] However, descriptions of CT findings at the level of the PSL origin in horses with and without PSD in the current literature are sparse. 22 The objective of this study was to evaluate soft tissue and bone window CT images of the proximoplantar MTIII region in horses with and without proximal suspensory pain and to compare findings between observers with different levels of experience.…”

“…The use of CT in equine orthopedic diagnostic imaging and particularly soft tissue imaging has significantly increased in recent years 16–19 . Particularly due to the short acquisition time and the increased availability of standing CT units at the referral level, CT imaging may offer a valid alternative to MRI of the PSL 18–21 .…”