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

The study examines the effect of different movement conditions (either walking or being stationary) on the uptake of a medical tracer, 18F-FDG, in the soft tissues of the foot (specifically, the lamellae and coronary band) of healthy horses. The findings suggest that the level of physical activity after the injection of the tracer can affect the amount absorbed in certain parts of the foot, although the impact was found to be relatively small and unlikely to impact the clinical diagnosis of hoof ailments like laminitis.

Research Methodology

• The study involved 8 healthy adult horses. The 18F-FDG tracer was administered to these horses and they were then either made to walk around (AMB condition) or were tied in stalls (NONAMB condition). This type of investigation design is called a randomized crossover design.
• The number of steps taken by the horses in both conditions were measured using accelerometers.
• After the injection, the level of uptake of 18F-FDG in the horses’ digital tissues, including the dorsal lamellae (proximal, middle, and distal), quarter lamellae (medial and lateral), and coronary band, was examined using positron emission tomography (PET) scan.
• The measured uptake was quantified in terms of standardized uptake values (SUV), both maximum (SUVmax) and average (SUVmean), and analyzed through a mixed-effects linear regression model.

Findings

• The average step count for the AMB group was significantly higher than for the NONAMB group. This means that the horses in the AMB group were considerably more active than those in the NONAMB group.
• Horses in the AMB group showed a higher maximum uptake of 18F-FDG in the proximal and middle parts of the dorsal lamellae when compared to the NONAMB horses. This suggests that the higher the ambulatory activity in horses, the more the 18F-FDG uptake in these areas.
• However, there was no significant difference in the uptake in the distal part of the dorsal lamellae or in the coronary band, showing that movement condition had little effect on 18F-FDG uptake in these areas.
• The uptake in the medial quarter lamellae was significantly higher in both max and mean values for the AMB group compared to the NONAMB group. Also, the medial quarter had lower SUV max and mean values when compared to the lateral quarter and mid dorsal lamellae.

Conclusions

• The results of the study show that level of activity (ambulatory state) can affect the uptake of the 18F-FDG tracer by the lamellar tissues, especially in the medial quarter part.
• However, the observed effect was relatively minor and is unlikely to have any significant impact on the clinical detection of diseases of these tissues, such as laminitis, a painful condition in the foot of horses.