[Differences comparison in asymmetry index from OSEM and BPL reconstructed 18F-FDG PET-MRI in temporal lobe epilepsy focus localization].

Objective

To evaluate the diagnostic value for temporal lobe epilepsy focus localization based on the asymmetry index (AI) derived from images reconstructed using the ordered subsets expectation maximization (OSEM) and the Bayesian penalized likelihood (BPL) methods on 18F-fluorodeoxyglucose (18F-FDG) PET-MRI.

Methods

This is a cross-sectional study. We collected and analyzed 18F-FDG PET-MRI brain images from 18 patients diagnosed with temporal lobe epilepsy at the PET Center of Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, between January 2020 and June 2023. The acquired PET list-mode data for each patient were reconstructed using three methods respectively: OSEM, BPL (β=150), and BPL (β=350). Quantitative analysis was performed on 9 pairs of bilateral brain regions: cerebellar cortex, hippocampus, parahippocampal gyrus, superior temporal gyrus, middle temporal gyrus, inferior temporal gyrus, entorhinal cortex, transverse temporal gyrus, and temporal pole. The mean standardized uptake value (SUVmean) for each region was extracted, and the AI for each region was calculated. The cerebellar cortex was considered the reference region, and other brain regions were classified into the epileptogenic zone (AI≥20%) and epileptic propagation zone (5%<AI<20%). Differences in SUVmean and AI among the three reconstruction methods were analyzed using one-way ANOVA or the Friedman test.

Results

A total of 18 patients with temporal lobe epilepsy were included [6 males, 12 females, mean age (29.5±14.7) years]. In both the right and left cerebellar cortex, the SUVmean values in the BPL (β=150) and BPL (β=350) were higher than those in the OSEM (left: 6.88±1.86 vs 6.80±1.83 vs 6.57±1.76; right: 6.84±1.81 vs 6.76±1.79 vs 6.49±1.69; all P<0.001). There were no significant differences in AI among the three reconstruction methods for the cerebellar cortex and the epileptic propagation zone (all P>0.05). In the epileptogenic zone, the AI in the BPL (β=350) was lower than that in the OSEM (24.68±4.13 vs 25.42±3.64, P=0.048), while there was no significant difference in AI between the BPL (β=150) and OSEM (P>0.05).

Conclusion

Compared with the OSEM method, AI in images reconstructed with the BPL method demonstrates no significant difference for localizing epileptogenic foci in temporal lobe epilepsy on 18F-FDG PET-MRI.