Differential Diagnosis of AH109A Tumor and Inflammation by Radioscintigrap with l‐[Methyl‐(11)C]methionine

For the evaluation of tumor imaging with l‐[methyl‐(11)C]methionine ((11)C‐Met), a basic study on the differentiation of tumor from inflammation with (11)C‐Met and a comparison of the diagnostic value of the image with that obtained using (67)Ga citrate, a conventional scintigraphic agent, are important. (11)C‐Met accumulations into inflammatory lesions, AH109A tumor and normal tissues of rats were examined by means of a tissue distribution study. Aseptic inflammatory lesions on the back of Donryu rats induced by croton oil and 1.5% carrageenan showed significantly lower accumulations of (11)C‐Met than the AH109A tumor. Histologically, croton oil induced granulomatous inflammation and carrageenan, acute exudative inflammation. Whole‐body antoradiography with (l4)C‐Met, a substitute for (11)C‐Met, was negative in the carrageenan lesion and showed a slightly increased activity at the periphery of the croton oil lesion, in contrast with the high tumor activity. Whole‐body autoradiogra‐phy with (67)Ga citrate was performed to compare the imaging ability with that of (14)C‐Met; it showed high activities in the tumor, bone, and intestine, and a broad increased activity at the periphery of the croton oil lesion, but was negative in the carrageenan lesion. (11)C‐Met accumulations in the inflammations were very low and clinical application with positron emission tomography, should be useful for the differential diagnosis of tumor from inflammation.