Anesthesia condition for ¹⁸F-FDG imaging of lung metastasis tumors using small animal PET

Small animal positron emission tomography (PET) with ¹⁸F-FDG has been increasingly used for tumor imaging in the murine model. The aim of this study was to establish the anesthesia condition for imaging of lung metastasis tumor using small animal ¹⁸F-FDG PET. Methods: To determine the impact of anesthesia on ¹⁸F-FDG distribution in normal mice, five groups were studied under the following conditions: no anesthesia, ketamine and xylazine (Ke/Xy), 0.5% isoflurane (Iso 0.5), 1% isoflurane (Iso 1) and 2% isoflurane (Iso 2). The ex vivo counting, standard uptake value (SUV) image and glucose SUV of ¹⁸F-FDG in various tissues were evaluated. The ¹⁸F-FDG images in the lung metastasis tumor model were obtained under no anesthesia, Ke/Xy and Iso 0.5, and registered with CT image to clarify the tumor region. Results: Blood glucose concentration and muscle uptake of ¹⁸F-FDG in the Ke/Xy group markedly increased more than in the other groups. The Iso 2 group increased ¹⁸F-FDG uptake in heart compared with the other groups. The Iso 0.5 anesthesized group showed the lowest ¹⁸F-FDG uptake in heart and chest wall. The small size of lung metastasis tumor (2 mm) was clearly visualized by ¹⁸F-FDG image with the Iso 0.5 anesthesia. Conclusion: Small animal ¹⁸F-FDG PET imaging with Iso 0.5 anesthesia was appropriate for the detection of lung metastasis tumor. To acquire ¹⁸F-FDG PET images with small animal PET, the type and level of anesthetic should be carefully considered to be suitable for the visualization of target tissue in the experimental model.