Ballageer EA, Kunst CM, Berger KL, et al.
Introduction/Purpose: The correlation of FDG PET signal, and simultaneously collected contrast-enhanced computed tomography (CT) images in spontaneous canine hepatic masses with histopathological diagnosis of the mass obtained with surgical biopsy can lead to advancement towards non-invasive methods of diagnosing underlying processes. Additional benefit to the patient exists as whole body PET scan represents a screening process to rule out distant primary tumor or metastases.
Methods: Twelve client-owned dogs with spontaneous masses in the liver discovered on ultrasound and exceeding 3 cm in diameter were enrolled between 1/2010 and 5/2012. Each received an intravenous injection of 18F-fluorodeoxyglucose, dosage ranging from 5.9 to 22.9 MBq/kg, 1 hour prior to scanning. A PET and multiphasic CT was performed, with injection of 800 mg I/kg iopamidol administration before arterial and venous phase images were collected. At review of images with the surgeon, therapy decision changes based on imaging were recorded. Each patient then had a laparoscopic or open surgical biopsy of the mass(es) within 1 week after imaging to correlate with images with histopathology. Analysis of images for attenuation, contrast enhancement, and radiopharmaceutical uptake was performed on MedView® software.
Results: Fifteen masses in the twelve dogs were histopathologically correlated with imaging results. 4/15 (26.7%) masses were benign, while 11/15 (73.3%) were malignant in origin. Malignant masses included 4 well differentiated hepatocellular carcinomas. All masses with peripheral arterial enhancement pattern were malignant, and benign masses tended to have higher magnitude increase in attenuation between arterial and venous phases of contrast uptake. The highest standardized uptake value (SUVmax) was in a plasma cell tumor at 7, but the lowest at 2.4 was also in a malignant mass, a well-differentiated hepatocellular carcinoma. The mean SUVmax for malignant masses was 4.08, while for benign masses, it was 3.4. CT examination resulted in case management decision change in 10/12 (83.3%) cases, while PET examination resulted in change in 8/12 (66.7%).
Discussion/ Conclusion: Considerable overlap in quantification of signal between benign and malignant hepatic processes on both CT and FDG PET examination exists, though larger case numbers may elucidate a difference not yet seen. Whole body screening commonly leads to therapeutic decision changes, and reveals distant disease that can affect overall outcome or increase suspicion of malignancy in the canine patient.