[¹¹C]Flumazenil PET in Temporal Lobe Epilepsy: Do We Need an Arterial Input Function or Kinetic Modeling?

Abstract

11 C]FMZ PET datasets and arterial plasma input functions were available for 15 patients with medically refractory medial temporal lobe epilepsy (TLE) and histologically verified unilateral HS and for 13 control subjects. SPM2 was used for analysis. ADD1020 and ADD2040 images showed decreased FMZ uptake ipsilateral to the epileptogenic hippocampus in 13/15 cases; 6/13 had bilateral decreases in the ADD1020 analysis and 5/13 in the ADD2040 analysis. BP-SRTM images detected ipsilateral decreases in 12/15 cases, with bilateral decreases in three. In contrast, VD images showed ipsilateral hippocampal decreases in all 15 patients, with bilateral decreases in three patients. Bilateral decreases in the ADD images tended to be more symmetrical and in one case were more marked contralaterally. Full quantification with an image-independent input should ideally be used in the evaluation of FMZ PET; at least in TLE, intrasubject correlations do not predict equivalent clinical usefulness.

18F-Flumazenil: A γ-Aminobutyric Acid A–Specific PET Radiotracer for the Localization of Drug-Resistant Temporal Lobe Epilepsy

“…This rate was higher than that found when analyzing static images (80%) but lower than the detection rate when using an invasive model (volume of distribution, 100%) (20). The results of the current study did not attain this level of detection; however, the SPM analysis supported the results of the ROI and visual analyses, indicating that the changes in 18 F-FMZ BP ND are more restricted to the epileptogenic zone than those of hypometabolism on 18 F-FDG PET.…”

“…However, the SUV images falsely localized the epileptogenic zone in 3 cases ( Table 2), highlighting that localization by nonparametric SUV images should be interpreted with some caution, as has had previously been noted by others (20,24). The visual inspection of both the SUV and the BP ND 18 F-FMZ PET images had a lower localization sensitivity than that for 18 F-FDG PET images.…”

“…This methodology is robust (20), relatively simple to apply, and suitable for use in routine clinical practice. The use of the SRTM is further supported by a previous work by Odano et al (12), which directly compared 18 F-FMZ and 11 C-FMZ in healthy volunteers.…”

“…Ryvlin et al (7) reported that visual inspection of 11 C-FMZ uptake images resulted in localization of the epileptogenic zone in 94% of TLE patients, including 100% of patients with unilateral MTS, 86% with normal MR imaging findings, and 66% with bilateral lesions. It is possible that our use of a reference tissue model (SRTM) to generate the parametric BP ND images resulted in a lower localization sensitivity than if an arterial plasma input function method had been used (20). A future study that directly compares 11 C-FMZ PET and 18 F-FMZ PET images in the same patient population, using the same analysis methodology, is required to make definitive conclusions about the relative sensitivity of the 2 tracers for PET imaging in drug-resistant TLE.…”

Validation of reference tissue modelling for [11C]flumazenil positron emission tomography following head injury

“…The pons has been used as a reference tissue for [ 11 C]FMZ and is validated for control subjects [6,[18][19][20][21][22] and various neurological disease patients [20,21].…”