Characterization of canine metastatic pulmonary nodules on 18F-fluorodeoxyglucose positron emission tomography/computed tomography.

BACKGROUND

Pulmonary metastasis is a major cause of mortality in dogs with cancers, but traditional thoracic imaging methods, such as radiographs and computed tomography (CT), have limited sensitivity for detecting small nodules. 18F-fluorodeoxyglucose positron emission tomography/CT (18F-FDG PET/CT) offers functional imaging capabilities and may improve metastasis detection and cancer staging. However, its role in evaluating pulmonary nodules in dogs is not well understood, and species-specific imaging parameters are lacking.

OBJECTIVE

This study aimed to characterize metastatic pulmonary nodules in dogs using 18F-FDG PET/CT, with a focus on associations among nodule size, location, and maximum standardized uptake value (SUVmax).

ANIMALS AND PROCEDURE: A total of 109 pulmonary nodules detected on 18F-FDG PET/CT in dogs with aggressive cancer were retrospectively reviewed by a Board-certified radiologist. Descriptive and analytical statistical analyses were done to assess relationships between imaging factors.

RESULTS

Nodule size and SUVmax varied highly, with a median diameter of 6.4 mm (range: 5 to 20 mm) and median SUVmax of 3.72 (range: 0.7 to 27.45). A moderate but positive correlation was noted between nodule size and SUVmax (τ = 0.526; P < 0.001). Nodule location did not significantly affect SUVmax. Furthermore, using a proposed SUVmax cutoff of 2.5 obtained from a human guideline, 34.9% (38/109) of nodules were classified as nonmalignant.

CONCLUSION AND CLINICAL RELEVANCE: Our findings contribute to the growing body of research on 18F-FDG PET/CT imaging in canine oncology and highlight the need for a dog-specific SUVmax threshold to improve diagnostic accuracy. We emphasize the need for larger prospective studies to refine interpretation of SUVmax values for metastatic pulmonary nodules in dogs.