Exploratory Clinical Investigation of (4S)-4-(3-¹⁸F-Fluoropropyl)-L-Glutamate Positron Emission Tomography of Inflammatory and Infectious Lesions

Abstract

We explored system x_Cˉ transporter activity and the dection of inflammatory/infectious lesions using (4S)-4-(3-¹⁸F-fluoropropyl)-L-glutamate (¹⁸F-FSPG) positron emission tomography (PET). Methods: In ten patients with various inflammatory/infectious diseases, as many as five of the largest inflammatory lesions were selected as reference lesions. ¹⁸F-FSPG images were assessed visually and quantitatively. Expression levels of xCT, CD44, and surface markers of inflammatory cells were evaluated by immunohistochemistry. Results: ¹⁸F-FSPG PET detected all reference lesions. ¹⁸F-FSPG uptake in sarcoidosis was significantly higher than that in non-sarcoidosis. The lesion-to-blood pool standardized uptake value (SUV) ratio of ¹⁸F-FSPG was comparable to that of ¹⁸F-fluorodeoxyglucose in sarcoidosis. In non-sarcoid lesions, however, it was significantly lower. In five with available tissue samples, the maximal SUV of ¹⁸F-FSPG and CD163 were negatively correlated ρ = -0.872, P = 0.054). Conclusion: ¹⁸-FSPG-PET may detect inflammatory lesions where activated macrophages/monocytes are present such as in sarcoidosis.