Dynamic Accumulation and Distribution of [F]FDG in Human Thyroid Cancer Model on Nude Mice: by INER Animal Rotating PET Scanner and Micro-Autoradiography

Received 1/8/2002; accepted 1/17/2002. For correspondence or reprints contact: Pan-Fu Kao, M.D., Department of Nuclear Medicine, Chang Gung Memorial Hospital and Chang Gung University, 199 Tung Hwa North Road, Taipei 105, Taiwan, R.O.C. Tel: (886)3-3281200 ext. 2622, Fax: (886)3-3282619, E-mail: [email protected] Background: Fluor ine-18-2-deoxy-D-glucose ([F]FDG) has been widespread used in tumor detection. This study investigated the dynamic accumulation and the distribution of [F]FDG in human thyroid cancer bearing nude mice with INER ARO-PET (Animal Rotating PET) scan and autoradiography. Methods: Human thyroid cancer cells were subcutaneously inoculated into 2 nude mice and allowed to grow for 2 months. The mice were anesthetized with pentobarbital (65 mg/kg; ip), followed by administration of [F]FDG through the tail vein. The injected dose of [F]FDG was 520 μCi to one mouse, and 620 μCi to the other. Only the plannar images were acquired using the upper and lower detectors of the ARO-PET system for dynamic study. The ARO-PET scanner acquired 30 sec/frame dynamic planar images, with 35 31 matrix size, for 4 h. Immediately after the dynamic image acquisition, the mice were sacrificed for micro-autoradiography and histopathological examination with H&E staining. A time-activity curve was generated by drawning regions of interest over the tumor and the contralateral side of thigh as the background control. Results: Dynamic image analyses showed a progressive and consistent increase in the uptake of [F]FDG up to 4 h after injection of the radiotracer. The uptake of [F]FDG by the thyroid cancer was approximately twice higher than that observed on the background control. In consistent with the observed uptake of [F]FDG by ARO-PET, micro-autoradiography showed density of silver grains in the tumor and surrounding granulation tissue. Conclusion: Dynamic analyses of [F]FDG planar imaging demonstrated progressive accumulation of [F]FDG in human thyroid tumors. The tumor uptake was about twice higher than the background at 4 h after injection of the radiotracer. Tumor uptake of [F]FDG was confirmed by micro-autoradiography performed on the same animal. The present studies suggest that the ARO-PET scanner can be used for [F]FDG dynamic distribution studies in small animals by a planar mode of imaging acquisition.