Brain positron emission tomography imaging with 18Fluorine-fluorodeoxyglucose (FDG-PET) has demonstrated utility in suspected autoimmune encephalitis. Visual and/or assisted image reading is not well established to evaluate hypometabolism/hypermetabolism. We retrospectively evaluated patients with autoimmune encephalitis between 2003 and 2018. Patients underwent EEG, brain magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) sampling and autoantibodies testing. Individual FDG-PET images were evaluated by standard visual reading and assisted by voxel-based analyses, compared to a normal database. For the latter, three different methods were performed: two based on statistical surface projections (Siemens syngo.via Database Comparison, and 3D-SSP Neurostat) and one based on statistical parametric mapping (SPM12). Hypometabolic and hypermetabolic findings were grouped to identify specific patterns. We found six cases with definite diagnosis of autoimmune encephalitis. Two cases had anti-LGI1, one had anti-NMDA-R and two anti-CASPR2 antibodies, and one was seronegative. ¹⁸F-FDG-PET metabolic abnormalities were present in all cases, regardless of the method of analysis. Medial–temporal and extra-limbic hypermetabolism were more clearly depicted by voxel-based analyses. We found autoantibody-specific patterns in line with the literature. Statistical surface projection (SSP) methods (Neurostat and syngo.via Database Comparison) were more sensitive and localized larger hypermetabolic areas. As it may lead to comparable and accurate results, visual analysis of FDG-PET studies for the diagnosis of autoimmune encephalitis benefits from voxel-based analysis, beyond the approach based on MRI, CSF sample and EEG.

Purpose: This review aims to explore the role of well-established and emerging radiopharmaceuticals different from 2-[¹⁸F]FDG (FDG) in multiple myeloma (MM) and smoldering multiple myeloma (SMM), as well as to describe new perspectives in preclinical data. Methods: A literature search was performed to identify clinical studies investigating PET radiotracers other than FDG in MM or SMM in the PubMed and Cochrane Library databases. Data were extracted into summary tables, detailing characteristics such as the mechanism of action of each radiopharmaceutical. For future perspectives, clinical studies were retrieved for imaging MM/SMM with radiopharmaceuticals targeting integrins, while preclinical studies were retrieved for those targeting CD-138, VLA-4, anti-BCMA, and nanoparticles. Results: A total of 28 clinical studies with the following radiopharmaceuticals: [¹¹C]methionine, [¹⁸F]FET, [¹⁸F]fluciclovine, [¹¹C]acetate, [¹¹C]choline, [¹⁸F]choline, [⁶⁸Ga]Ga-PSMA-11, [¹⁸F]NaF, [⁶⁸Ga]Ga-DOTATATE, [⁶⁸Ga]Ga-FAPI-04, [⁶⁸Ga]Ga-pentixafor and [⁸⁹Zr]/[⁶⁴Cu]daratumumab were found and summarized. For future perspectives, one clinical study targeting integrins and four preclinical studies were summarized. Conclusion: Compared to FDG, alternative tracers show promise for improved detection. However, their routine clinical use is limited by factors such as availability, cost, and lack of validation in large multicenter studies. Further research, including dual-tracer and theragnostic approaches, is essential but still far from everyday clinical application.