Bone metastases in midgut neuroendocrine tumors: imaging characteristics, distribution, and risk factors.

PURPOSE: Bone metastases (BM) affect 10-30% of patients with small intestine neuroendocrine tumors (siNET), but little descriptive data are available regarding their distribution throughout the skeleton or potential risk factors. Aim of the study is to better describe the imaging characteristics, distribution, and risk factors of siNET bone metastases using 18F-FDOPA PET/CT. METHODS: All patients with well-differentiated siNET who underwent an 18F-DOPA PET/CT examination in our institution were retrospectively screened between October 2017 and February 2020. Location, SUVmax and CT density of each BM were collected. Sex, metabolic tumor volume (MTV) excluding bone, and metastatic sites other than bone were studied to determine risk factors of BM. RESULTS: Among the 69 patients included, 11 patients (15.9%) presented BM on 18F-FDOPA (65 metastases). The most frequently involved sites were: thoracic spine, pelvic bones and ribs. About 64% of patients presented multiple BM. On coupled CT scan, 63% of BM were not visible. Using an optimal threshold of 19.2 ml, MTV was an independent predictor of BM (p = 0.004) with a derived sensitivity of 100% [65.0-100.0] and a specificity of 70.9% [57.7-81.2]. Hepatic metastatic involvement was also a significant predictor of BM (p = 0.044). CONCLUSION: The development of BM in siNETs appears to be a late event, occurring in patients with a high tumor burden and hepatic involvement. They are often multiple and predominate in the axial skeleton.

18F-FDG PET/CT in Anti-Leucine-Rich Glioma-Inactivated 1 Antibody Encephalitis: Typical Pattern and Follow-up.

ABSTRACT: We report the case of a 55-year-old man presenting pseudopsychiatric behavior disorders of subacute-onset. MRI showed a FLAIR (fluid-attenuated inversion recovery) hyperintensity in the left hippocampus. The diagnosis of limbic encephalitis was raised, and the patient was referred for an 18F-FDG PET/CT. PET/CT depicted an increased uptake of the left mesiotemporal structures and also an increased uptake of both cerebellum and striatal areas. This pattern was compatible with an anti-leucine-rich glioma-inactivated 1 antibody encephalitis that was later confirmed.

Position-specific 15 N isotope analysis in organic molecules: A high-precision 15 N NMR method to determine the intramolecular 15 N isotope composition and fractionation at natural abundance.

The position-specific 15 N isotope content in organic molecules, at natural abundance, is for the first time determined by using a quantitative methodology based on 15 N Nuclear Magnetic Resonance (NMR) spectrometry. 15 N NMR spectra are obtained by using an adiabatic "Full-Spectrum" INEPT sequence in order to make possible 15 N NMR experiments with a high signal-to-noise ratio (>500), to reach a precision with a standard deviation below 1‰ (0.1%). This level of precision is required for observing small changes in 15 N content associated to 15 N isotope effects. As an illustration, the measurement of an isotopic enrichment factor ε for each 15 N isotopomer is presented for 1-methylimidazole induced during a separation process on a silica column. The precision expressed as the long-term repeatability of the methodology is good enough to evaluate small changes in the 15 N isotope contents for a given isotopomer. As observed for 13 C, inverse and normal 15 N isotope effects occur concomitantly, giving access to new information on the origin of the 15 N isotope effects, not detectable by other techniques such as isotope ratio measured by Mass Spectrometry for which bulk (average) values are obtained.