The utility of a 3-dimensional, large-field-of-view, sodium iodide crystal-based PET scanner in the presurgical evaluation of partial epilepsy

F-18-FDG PET is an accurate and reliable technique for localizing medically refractory temporal lobe epilepsy, but widespread use has been hindered by limited reimbursement in many countries because of the high cost of tradit ional PET equipment and radioisotopes. Additionally, the place of FDG PET a s a cost-effective tool for presurgical evaluation of epilepsy has been que stioned because of limited data showing that FDG PET provides localization information incremental to that provided by more established techniques, pa rticularly MRI and ictal electroencephalography (EEG). Three-dimensional (3 D), large-field-of-view, sodium iodide crystal-based scanners have lower eq uipment and running costs and better multiplanar resolution than traditiona l 2-dimensional bismuth germanate (BGO) systems but have not yet been valid ated for evaluation of epilepsy. Our purpose was to investigate the localiz ation rate, accuracy, and prognostic value of FDG PET images acquired on a 3D, large-field-of-view, sodium iodide crystal-based PET scanner in the pre surgical evaluation of intractable partial epilepsy. We also wanted to esta blish the incremental value of FDG PET over established MRI and ictal EEG t echniques. Methods: Fifty-five patients who were surgical candidates becaus e of medically refractory partial epilepsy were examined. For most of these patients, the lesions had not been clearly localized on conventional asses sment. The FDG PET scans were reviewed independently by 2 reviewers who wer e unaware of the patients' clinical details, ictal EEG findings, and volume tric MRI results, and the FDG PET results were correlated with those of MRI and EEG and with postsurgical outcome. Results: Forty-two patients (76%) h ad localizing FDG PET images (37 temporal, 5 extratemporal). The ictal EEG recordings were localizing in 66%, and the MRI findings were localizing in 27% (which increased to 35% after the MRI findings were reviewed again afte r PET). Concordance between the site of the PET localizations and the site of the MRI or EEG localizations was 100%. The PET images were localizing in 63% and 69% of patients with nonlocalizing ictal EEG and MRI findings, res pectively. Twenty-one of 24 patients who subsequently underwent epilepsy su rgery had localizing FDG PET images; of these 21 patients, 18 (86%) had a c lass I outcome. Multiple regression analysis showed the FDG PET results to be predictive of postsurgical outcome independently of the MRI findings. Co nclusion: For intractable partial epilepsy, FDG PET using a 3D, large-field -of-view, sodium iodide crystal-based scanner provided clinically useful lo calizing information that was at least as accurate as the results reported for traditional BGO-based scanners. The PET images provided prognostically significant localization information incremental to that provided by volume tric MRI and ictal EEG, particularly if 1 of these studies was nonlocalizin g.