18F-sodium fluoride positron emission tomography provides pertinent additional information to computed tomography for assessment and management of tarsal pain in horses.

The study assesses the effectiveness of a specific type of positron emission tomography, the 18F-sodium fluoride (18F-NaF) PET, in comparison to computed tomography (CT) in diagnosing and managing horses with pain in the tarsus and proximal metatarsal areas. The study suggests that PET imaging offers helpful supplemental information to CT and helps in differentiating active versus inactive lesions.

Methods

• The researchers used a sample size of 25 horses exhibiting lameness localized to the tarsal and proximal metatarsal regions. These horses had been subjected to 18F-NaF PET/CT procedures from 2016 to 2021.
• The PET and CT images gathered were independently analyzed retrospectively by three distinct observers. To quantify the degree of 18F-NaF uptake, the researchers used standardized uptake values (SUV).
• In an attempt to establish a relationship between PET and CT findings with the severity of lameness, the observation data were compared with both subjective and objective maximum (Max-D) and minimum pelvic height lameness data.

Results

• The inter-observer consistency, as measured using the kappa-weighted value (κ), was found to be a bit higher for PET (κ = 0.66) compared to CT (κ = 0.6).
• CT and PET scores displayed a reasonable correlation (R = 0.49; P < 0.05). The PET SUVratio (the ratio of SUV of the main lesion to the SUV of the talus) revealed the highest association with Max-D (R = 0.71; P < .05).
• PET and CT scores for the plantar region were significantly greater in Quarter Horses and revealed consistently higher associations with objective lameness data (CT plantar grade – Max-D [R = 0.6; P < .05], PET plantar grade – Max-D [R = 0.47; P = .04]) compared to other areas of the distal tarsal joints.
• In three Warmblood horse breeds, stand-out uptake was observed at the medial cochlea of the distal tibia.

Conclusions

• The study concluded that for tarsal lesion assessment, PET imaging had a moderate correlation with findings from CT scans.
• The intensity of uptake during PET imaging can aid in distinguishing between active and inactive lesions.
• The specific location of the uptake was considered essential in determining the clinical significance of the findings.