Annals of Nuclear Medicine

, Volume 26, Issue 4, pp 319–326 | Cite as

Usefulness of extent analysis for statistical parametric mapping with asymmetry index using inter-ictal FGD-PET in mesial temporal lobe epilepsy

  • Tsutomu Soma
  • Toshimitsu Momose
  • Miwako Takahashi
  • Keitraro Koyama
  • Kensuke Kawai
  • Kenya Murase
  • Kuni Ohtomo
Original article

Abstract

Objective

Inter-ictal 18F-2-fluoro-deoxy-d-glucose-positron emission tomography (FDG-PET) is widely used for preoperative evaluation to identify epileptogenic zones in patients with temporal lobe epilepsy. In this study, we combined statistical parametric mapping (SPM) with the asymmetry index and volume-of-interest (VOI) based extent analysis employing preoperative FDG-PET in unilateral mesial temporal lobe epilepsy (MTLE) patients. We also evaluated the detection utility of these techniques for automated identification of abnormalities in the unilateral hippocampal area later confirmed to be epileptogenic zones by surgical treatment and subsequent good seizure control.

Methods

FDG-PET scans of 17 patients (9 males, mean age 35 years, age range 16–60 years) were retrospectively analyzed. All patients had been preoperatively diagnosed with unilateral MTLE. The surgical outcomes of all patients were Engel class 1A or 1B with postoperative follow-up of 2 years. FDG-PET images were spatially normalized and smoothed. After two voxel-value adjustments, one employing the asymmetry index and the other global normalization, had been applied to the images separately, voxel-based statistical comparisons were performed with 20 controls. Peak analysis and extent analysis in the VOI in the parahippocampal gyrus were conducted for SPM. For the extent analysis, a receiver operating characteristic (ROC) curve was devised to calculate the area under the curve and to determine the optimal threshold of extent.

Results

The accuracy of the method employing the asymmetry index was better than that of the global normalization method for both the peak and the extent analysis. The ROC analysis results, for the extent analysis, yielded an area under the curve of 0.971, such that the accuracy and optimal extent threshold of judgment were 92 and 32.9%, respectively.

Conclusion

Statistical z-score mapping with the asymmetry index was more sensitive for detecting regional glucose hypometabolism and more accurate for identifying the side harboring the epileptogenic zone using inter-ictal FDG-PET in unilateral MTLE than z-score mapping with global normalization. Moreover, the automated determination of the side with the epileptogenic zone in unilateral MTLE showed improved accuracy when the combination of SPM with the asymmetry index and extent analysis was applied based on the VOI in the parahippocampal gyrus.

Keywords

Asymmetry index Statistical parametric mapping FDG-PET Mesial temporal lobe epilepsy 

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Copyright information

© The Japanese Society of Nuclear Medicine 2012

Authors and Affiliations

  • Tsutomu Soma
    • 1
    • 3
    • 4
  • Toshimitsu Momose
    • 1
  • Miwako Takahashi
    • 1
  • Keitraro Koyama
    • 1
  • Kensuke Kawai
    • 2
  • Kenya Murase
    • 3
  • Kuni Ohtomo
    • 1
  1. 1.Department of Radiology, Graduate School of MedicineUniversity of TokyoTokyoJapan
  2. 2.Department of Neurosurgery, Graduate School of MedicineUniversity of TokyoTokyoJapan
  3. 3.Course of Health Science, Division of Medical Technology and Science, Department of Medical Physics and Engineering, Graduate School of MedicineOsaka UniversityOsakaJapan
  4. 4.Software Development Group, Product Management and Marketing DepartmentFUJIFILM RI Pharma Co., LtdTokyoJapan

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