OBJECTIVE: The up-regulation of translocator protein (TSPO) in activated but not resting microglia, can be detected using PET imaging. This can serve to provide noninvasive in vivo quantitative biochemical / molecular imaging of neuro-inflammation in multiple sclerosis (MS). Although the radiotracer 11C-PK11195 has been used previously for this purpose, it has a few limitations. Recently, we evaluated an improved radiotracer 18F-GE180 for detecting neuro-inflammation in children with multiple sclerosis (MS).
METHODS: Five non-sedated MS patients (ages 14- 17 years; 2 girls) with clinical and MRI diagnosis of multiple sclerosis were administered 0.07 mCi/kg 18F-GE180 i.v. and scanned using the GE SIGNA PET/MR scanner.  MRI images were compared with previous clinical MRI scans to monitor lesion changes.
RESULTS: A low background uptake in non-inflammed brain parenchyma with higher uptake seen in choroid plexus and vascular compartments.  Multifocal parenchymal areas of intense 18F-GE180 uptake were seen in two MS patients. The highest SUV values were seen in the PET-positive lesions (SUV = 0.93 ± 0.19), whereas PET-negative lesions showed values no different from background grey/white matter. The PET-negative lesions were consistent with stable MRI T2 hyper-intense lesions, suggesting that those lesions were not in active neuro-inflammation phase. 
CONCLUSIONS: The low signal-to-noise ratio of 18F-GE180, longer half-life of 18F-GE180, compared with previously used 11C-PK11195, has significant advantages. Our preliminary data suggest that 18F-GE180-PET may be a useful radiotracer to evaluate degree of neuro-inflammation in children with MS, and a 3-D brain imaging, using the hybrid PET/MR scanner, can provide comprehensive assessment of demyelinating lesions.