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  • Author or Editor: Alejandro Valdes x
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Objective—To determine the ideal interval to image acquisition after IV injection of sodium fluoride F 18 (18F-NaF) and evaluate biodistribution of the radiopharmaceutical in clinically normal skeletally immature dogs.

Animals—4 female dogs.

Procedures—Each dog was anesthetized for evaluation with a commercial hybrid positron emission tomography (PET)–CT instrument. A low–radiation dose, whole-body CT scan was acquired first. An IV injection of 18F-NaF (0.14 mCi/kg) was administered, and a dynamic PET scan centered over the heart and liver was acquired during a period of 120 minutes. Uptake of 18F-NaF in the blood pool, soft tissues, and skeletal structures was evaluated via region of interest analysis to derive standardized uptake values and time-activity curves, which were used to determine the optimal postinjection time for skeletal image acquisition. Biodistribution was also assessed from a final whole-body PET-CT scan acquired after the dynamic scan.

Results—Time-activity curves revealed a rapid decrease in the amount of radiopharmaceutical in the blood pool and soft tissues and a rapid increase in the amount of radiopharmaceutical in bones soon after injection. At 50 minutes after injection, the greatest difference in uptake between soft tissues and bones was detected, with continued subtle increase in uptake in the bones. Uptake of 18F-NaF was slightly increased at growth plates and open ossification centers, compared with that at other parts of the bone.

Conclusions and Clinical Relevance—At 50 minutes after IV injection of 18F-NaF at the dose evaluated, PET-CT yielded excellent bone-to-background ratio images for evaluation of the skeletal system in dogs.

Full access
in American Journal of Veterinary Research


Objective—To develop a quantitative method of interpreting tibial scintigrams of Thoroughbred racehorses with tibial stress fractures that may facilitate diagnosis of fractures and to provide prognostic information regarding future performance of affected horses.

Animals—35 Thoroughbred racehorses.

Procedures—Static bone-phase scintigrams of tibial stress fractures were quantitatively analyzed by use of ratios of the mean radionuclide counts per pixel in a region of interest (ROI) drawn around the area of increased uptake of radiopharmaceutical to mean counts per pixel in a second ROI drawn around an apparently normal area of the tibial diaphysis. In horses with unilateral fractures, ratios for the contralateral tibia were determined by use of 2 ROIs drawn at the same positions as the ROIs in the fractured tibia. Ratios were compared between fractured versus apparently normal tibias, between horses that returned to racing versus those that did not, and among horses with various grades of lameness. The association between ratios for fractured tibias and intervals between diagnosis and return to racing was also assessed.

Results—Mean ratio of ROIs in apparently normal tibias was 1.35 (95% confidence interval [CI], 1.21 to 1.50); that in tibias with stress fractures was 3.55 (95% CI, 2.50 to 4.60). These ratios were significantly different. None of the associations between ratios for fractured tibias and grades of lameness or performance outcomes were significant.

Conclusions and Clinical Relevance—Tibial stress fracture scintigrams can be quantitatively analyzed. A prospective study with a controlled rehabilitation period is necessary to evaluate the possible applications of this method.

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in American Journal of Veterinary Research