Measurement of equine laminar blood flow and vascular permeability by use of dynamic contrast-enhanced computed tomography

Objective - To define the reference range for laminar blood flow (BF) and vascular permeability (VPM) in horses without laminitis by use of dynamic contrast-enhanced computed tomography (CT). Animals - 9 adult horses that were not lame and had no abnormalities of the laminae or phalanges detectable via radiographic examination. Procedures - Each horse was anesthetized by use of a routine protocol. Horses were placed in right or left lateral recumbency with the dependent forelimb in the CT gantry; only 1 limb of each horse was scanned. Serial 10-mm collimated transverse CT images were acquired at the same location every other second for 90 seconds during infusion of ionic, iodinated contrast medium. Custom software was used to estimate BF, VPM, and fractional vascular volume (FVV) in the dorsal, dorsomedial, and dorsolateral laminar regions. Results - Among the 9 horses' forelimbs, mean ± SD dorsal laminar BF was 0.43 ± 0.21 mL·min^-1·mL^-1. Mean dorsomedial and dorsolateral laminar BFs were 0.26 ± 0.16 mL·min^-1 ·mL^-1 and 0.24 ± 0.16 mL·min^-1·mL^-1, respectively. Mean dorsal laminar VPM was 0.09 ± 0.03 mL·min^-1·mL^-1. Mean dorsomedial and dorsolateral laminar VPMs were 0.16 ± 0.06 mL·min^-1·mL^-1 and 0.12 ± 0.06 mL·min^-1·mL^-1, respectively. Mean dorsal laminar FVV was 0.63 ± 0.20 and dorsomedial and dorsolateral laminar FVV were 0.37 ± 0.14 and 0.34 ± 0.17, respectively. Conclusions and Clinical Relevance - In horses, laminar BF, VPM, and FVV can be non-invasively measured by use of dynamic contrast-enhanced.