Abstract
Aims: Static fluorodeoxyglucose (FDG)-positron emission tomographic (PET) imaging plays an important role in the localization of epileptic foci. Dynamic FDG PET allows calculation of kinetic parameters. The aim of this study was to investigate whether kinetic parameters have potential for identifying epileptic foci, and to assess the correlation of parameters asymmetry indexes (ASYM) between dynamic and static FDG PET for understanding the pathophysiology of hypometabolism within intractable epilepsy.Methods: Seventeen patients who had refractory epilepsy correctly localized by static FDG PET with good outcome after foci resection were included. Eight controls were also studied. We performed dynamic and static FDG PET scan before operation. Images of both scans were coregistered to the montreal neurological institute space, regional time activity curves and activity concentration (AC) were obtained by applying the automated anatomical labeling template to the two spatially normalized images, respectively. Kinetic parameters were obtained using a two-tissue non-reversible compartmental model with an image-derived input function. AC from the static scan was used. Side-to-side ASYM of both static AC and kinetic parameters were calculated and analyzed in the hypometabolic epileptogenic regions and non-epileptogenic regions.Results: Higher values of ASYM from both kinetic parameters and static AC were found in the patients compared to the controls from epileptogenic regions. In the non-epileptogenic regions, no ASYM differences were seen between patients and controls for all parameters. In patients, static AC showed larger ASYM than influx (K1) and efflux (k2) of capillaries, but there were no statistical differences of ASYM between net metabolic flux (Ki) or the phosphorylation (k3) and static AC. ASYM of static AC positively correlated with ASYM of k3.Conclusion: Dynamic FDG PET can provide equally effective in detecting the epileptic foci compared to static FDG PET in this small cohort. In addition, compared to capillary influx, the hypometabolism of epileptic foci may be related to reduced glucose phosphorylation.
Highlights
Epilepsy is considered as one of the most common chronic neurological diseases affecting 65 million people of all ages worldwide (Moshe et al, 2015)
Interictal positron emission tomography (PET) measurements of glucose metabolism using fluorodeoxyglucose (FDG) has become a powerful diagnostic tool for presurgical delineation of patients with intractable epilepsy (Burneo et al, 2015), it demonstrated a sensitivity of 70–95% in patients with temporal lobe epilepsy (TLE) and 20–70% in extra-TLE patients, the highest clinical benefit of FDG PET can be achieved in patients with magnetic resonance imaging (MRI) negative TLE (Uijl et al, 2007; Muhlhofer et al, 2017; Sidhu et al, 2018)
The asymmetry indexes (ASYM) of every parameter in our epileptic focus regions are significantly larger than the nonepileptogenic regions, which is the most needed for visual assessment
Summary
Epilepsy is considered as one of the most common chronic neurological diseases affecting 65 million people of all ages worldwide (Moshe et al, 2015). Hypometabolism of epileptogenic focus delineation for surgical planning by using FDG PET is classically based on static images (Engel et al, 1990; Wieser and ILAE Commission on Neurosurgery of Epilepsy, 2004; Uijl et al, 2007). Static AC or SUV is calculated based on the FDG concentration of a region at a single time point normalized by the administered FDG activity and body weight, it is a relative measurement and can be affected by various factors (Devriese et al, 2016). Quantitative analysis of dynamic FDG PET studies may provide more information than a single time point measurement for the epileptic region and potentially improving the diagnosis and treatment of patients
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