Effect of ambulation following 18F-fluorodeoxyglucose injection on standing positron emission tomography of the healthy equine digit

Abstract

Abstract OBJECTIVE Measure 18F-FDG uptake in digital tissues of healthy horses subjected to different ambulatory conditions between the time of injection and positron emission tomography (PET) scan acquisition. ANIMALS 8 healthy adult horses. METHODS Horses were walked (AMB) or tied in stalls (NONAMB) immediately after injection with ∼1.5 MBq/kg 18F-FDG until scan acquisition using a randomized crossover design. Steps were quantified using accelerometers. Standardized uptake values (SUV; mean and maximum) in digital tissues including the dorsal lamellae (proximal, middle, and distal), quarter lamellae (medial and lateral), and coronary band were analyzed using a mixed-effects linear regression model. RESULTS Mean (95% CI) step count for AMB (569[484–653]) was higher than NONAMB (88[24–152]) P = <.001. The SUVmax (but not SUVmean) was increased in AMB compared with NONAMB in the proximal (2.74[2.52–2.98] vs 2.42[2.05–2.78]; P = .04) and middle (2.74[2.37–3.11] vs 2.36[2.05–2.68]; P = .03) dorsal lamellae but was not different in the distal lamellae or coronary band. In the medial quarter lamellae, both SUVmax (2.53[1.58–3.48] vs 2.07[0.81–3.33]; P = .01) and SUVmean (1.90[1.55–2.25] vs 1.49[0.91–2.06]; P = .007) were increased in AMB compared with NONAMB. The medial quarter lamellae also had lower SUVmax (P = .002) and SUVmean (P = .04) compared with the lateral quarter and lower SUVmax compared with the mid-dorsal lamellae (P = .01). CLINICAL RELEVANCE Lamellar 18F-FDG uptake was affected by ambulatory activity mostly in the medial quarter; however, this effect was relatively small and unlikely to interfere with clinical detection of laminitis.