Abstract
Purpose: Magnetic resonance imaging (MRI) and positron emission tomography (PET) with 18F-fluorodeoxyglucose (18FDG) are valuable tools for evaluating hippocampal sclerosis (HS); however, bias may arise during visual analyses. The aim of this study was to evaluate and compare MRI and PET post-processing techniques, automated quantitative hippocampal volume (Q-volume), and fluid-attenuated inversion-recovery (FLAIR) signal (Q-FLAIR) and glucose metabolism (Q-PET) analyses in patients with HS.Methods: We collected MRI and 18FDG-PET images from 54 patients with HS and 22 healthy controls and independently performed conventional visual analyses (CVA) of PET (CVA-PET) and MRI (CVA-MRI) images. During the subsequent quantitative analyses, the hippocampus was segmented from the 3D T1 image, and the mean volumetric, FLAIR intensity and standardized uptake value ratio (SUVR) values of the left and right hippocampus were assessed in each subject. Threshold confidence levels calculated from the mean volumetric, FLAIR intensity and SUVR values of the controls were used to identify healthy subjects or subjects with HS. The performance of the three methods was assessed using receiver operating characteristic (ROC) curves, and the detection rates of CVA-MRI, CVA-PET, Q-volume, Q-FLAIR, and Q-PET were statistically compared.Results: The areas under the curves (AUCs) for the Q-volume, Q-FLAIR, and Q-PET ROC analyses were 0.88, 0.41, and 0.98, which suggested a diagnostic method with moderate, poor, and high accuracy, respectively. Although Q-PET had the highest detection rate among the two CVA methods and three quantitative methods, the difference between Q-volume and Q-PET did not reach statistical significance. Regarding the HS subtypes, CVA-MRI, CVA-PET, Q-volume, and Q-PET had similar detection rates for type 1 HS, and Q-PET was the most sensitive method for detecting types 2 and 3 HS.Conclusions: In MRI or 18FDG-PET images that have been visually assessed by experts, the quantification of hippocampal volume or glucose uptake can increase the detection of HS and appear to be additional valuable diagnostic tools for evaluating patients with epilepsy who are suspected of having HS.
Highlights
Mesial temporal lobe epilepsy (MTLE) is the most frequent form of partial drug-resistant epilepsy in adults, and hippocampal sclerosis (HS) is the main pathological substrate, accounting for 17–44.5% of surgical candidates in epilepsy centers [1,2,3]
The hippocampal volume, signal, and glucose uptake values are difficult to compare bilaterally in an asymmetric scan, and mild changes tend to be overlooked by image readers who are blinded to the clinical manifestations or electroencephalography (EEG) data
We explored whether the sensitivity of each modality differed in patients with different HS subtypes, as classified by the International League Against Epilepsy (ILAE) grading system [14]
Summary
Mesial temporal lobe epilepsy (MTLE) is the most frequent form of partial drug-resistant epilepsy in adults, and hippocampal sclerosis (HS) is the main pathological substrate, accounting for 17–44.5% of surgical candidates in epilepsy centers [1,2,3]. The identification of HS is clinically important, as these patients have a 68% chance of becoming seizure free after surgery [4]. Interictal PET imaging is widely used in the presurgical evaluation of patients with MTLE in many epilepsy centers, as temporal glucose hypometabolism has been reported to predict favorable seizure outcomes after surgery [7]. The hippocampal volume, signal, and glucose uptake values are difficult to compare bilaterally in an asymmetric scan, and mild changes tend to be overlooked by image readers who are blinded to the clinical manifestations or electroencephalography (EEG) data
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