Comparison of Ictal Brain Perfusion SPECT With 99mTc-HMPAO Versus 99mTc-ECD for Identification of The Epileptic Seizure Onset Zone
Abstract Background: The chemical microspheres 99mTc-HMPAO and 99mTc-ECD are widely used as tracers in ictal brain perfusion SPECT for identification of the seizure onset zone (SOZ) in presurgical evaluation of patients with drug-resistant epilepsy and uncertainty of SOZ localization after standard diagnostic workup. For both tracers there are theoretical arguments to favor it over the other for this task. The aim of this study was to compare the performance of ictal brain perfusion SPECT between 99mTc-HMPAO and 99mTc-ECD in a rather large patient sample.Methods: The study retrospectively included 196 patients from clinical routine in whom ictal perfusion SPECT had been performed with stabilized 99mTc-HMPAO (n = 110) or 99mTc-ECD (n = 86). Lateralization and localization of the SOZ was obtained by the consensus of two independent readers who visually inspected the SPECT images retrospectively. Results: The 99mTc-HMPAO group and the 99mTc-ECD group were well matched with respect to age, sex, age at first seizure, duration of disease, seizure frequency, history of previous brain surgery, and findings of presurgical MRI. The tracer groups differed significantly with respect to the latency of tracer injection (median latency 4 s longer in the 99mTc-HMPAO group), duration of the seizure after tracer injection (25 s shorter in the 99mTc-HMPAO group), tracer dose (70 MBq higher in the 99mTc-HMPAO group), and delay of the SPECT acquisition after tracer injection (63 min longer in the 99mTc-HMPAO group). The fraction of lateralising ictal SPECT did not differ significantly between the 99mTc-HMPAO and the 99mTc-ECD group (65.5% versus 72.1%, p = 0.355). Sensitivity of ictal perfusion SPECT (independent of the tracer) for correct localization of the SOZ in 62 patients with temporal lobe epilepsy and at least worthwhile improvement (Engel scale ≤ III) 12 months after temporal epilepsy surgery was 63%.Conclusions: This study does not provide evidence to favor 99mTc-HMPAO or 99mTc-ECD for identification of the SOZ by ictal perfusion SPECT in patients with drug resistant epilepsy.