18F-FDOPA PET and MRI characteristics correlate with degree of malignancy and predict survival in treatment-naïve gliomas: a cross-sectional study.

INTRODUCTION: To report the potential value of pre-operative 18F-FDOPA PET and anatomic MRI in diagnosis and prognosis of glioma patients. METHODS: Forty-five patients with a pathological diagnosis of glioma with pre-operative 18F-FDOPA PET and anatomic MRI were retrospectively examined. The volume of contrast enhancement and T2 hyperintensity on MRI images along with the ratio of maximum 18F-FDOPA SUV in tumor to normal tissue (T/N SUVmax) were measured and used to predict tumor grade, molecular status, and overall survival (OS). RESULTS: A significant correlation was observed between WHO grade and: the volume of contrast enhancement (r = 0.67), volume of T2 hyperintensity (r = 0.42), and 18F-FDOPA uptake (r = 0.60) (P < 0.01 for each correlation). The volume of contrast enhancement and 18F-FDOPA T/N SUVmax were significantly higher in glioblastoma (WHO IV) compared with lower grade gliomas (WHO I-III), as well as for high-grade gliomas (WHO III-IV) compared with low-grade gliomas (WHO I-II). Receiver-operator characteristic (ROC) analyses confirmed the volume of contrast enhancement and 18F-FDOPA T/N SUVmax could each differentiate patient groups. No significant differences in 18F-FDOPA uptake were observed by IDH or MGMT status. Multivariable Cox regression suggested age (HR 1.16, P = 0.0001) and continuous measures of 18F-FDOPA PET T/N SUVmax (HR 4.43, P = 0.016) were significant prognostic factors for OS in WHO I-IV gliomas. CONCLUSIONS: Current findings suggest a potential role for the use of pre-operative 18F-FDOPA PET in suspected glioma. Increased 18F-FDOPA uptake may not only predict higher glioma grade, but also worse OS.

Xenon impairs reconsolidation of fear memories in a rat model of post-traumatic stress disorder (PTSD).

Xenon (Xe) is a noble gas that has been developed for use in people as an inhalational anesthestic and a diagnostic imaging agent. Xe inhibits glutamatergic N-methyl-D-aspartate (NMDA) receptors involved in learning and memory and can affect synaptic plasticity in the amygdala and hippocampus, two brain areas known to play a role in fear conditioning models of post-traumatic stress disorder (PTSD). Because glutamate receptors also have been shown to play a role in fear memory reconsolidation--a state in which recalled memories become susceptible to modification--we examined whether Xe administered after fear memory reactivation could affect subsequent expression of fear-like behavior (freezing) in rats. Male Sprague-Dawley rats were trained for contextual and cued fear conditioning and the effects of inhaled Xe (25%, 1 hr) on fear memory reconsolidation were tested using conditioned freezing measured days or weeks after reactivation/Xe administration. Xe administration immediately after fear memory reactivation significantly reduced conditioned freezing when tested 48 h, 96 h or 18 d after reactivation/Xe administration. Xe did not affect freezing when treatment was delayed until 2 h after reactivation or when administered in the absence of fear memory reactivation. These data suggest that Xe substantially and persistently inhibits memory reconsolidation in a reactivation and time-dependent manner, that it could be used as a new research tool to characterize reconsolidation and other memory processes, and that it could be developed to treat people with PTSD and other disorders related to emotional memory.