Measurement of Temporal Asymmetries of Glucose Consumption Using Linear Profiles: Reproducibility and Comparison with Visual Analysis

Summary

Aim: One approach to regionally analyze temporal glucose consumption consists in drawing linear profiles over the maximal values measured in the temporal cortical ribbon. The aim of our study was to test the reproducibility of this method and to compare its diagnostic performance to that of visual analysis in patients with complex partial seizures (CPS). Methods: Regional cerebral glucose consumption (rCMRGIc) was measured interictally in 25 CPS patients and 10 controls using F-18-deoxyglucose and the positron emission tomography (PET) camera ECAT EXACT 47. The PET scans were visually analyzed for the occurrence of unilateral temporal hypermetabolism. Furthermore, rCMRGIc was quantified on six contiguous coronal planes by manually tracing maximal values of temporal glucose consumption, thus creating line profiles of temporal glucose consumption for each side. Indices of asymmetry (ASY) were then calculated from these line profiles in four temporal regions and compared to the corresponding 95% confidence intervals of the control data. All analyses were performed by two observers independently from each other and without knowledge of the clinical findings. Results: The agreement between the two observers with regard to focus lateralization was 96% (κ = 0.93) on visual analysis and 100% (κ = 1) on quantitative analysis. There was an excellent agreement with regard to focus lateralization between visual and quantitative evaluation (κ = 0.8). Conclusion: Quantitation of local temporal rCMRGIc by using linear profile analysis is highly reproducible; for the lateralization of epileptogenic foci, however, this method does not possess significant advantages over the visual evaluation of the scans.

Zusammenfassung

Ziel: Ein Ansatz zur regionalen Analyse des temporalen Glukoseverbrauchs besteht im Zeichnen von Linienprofilen über den Maxima des temporalen Glukoseverbrauchs. Das Ziel unserer Studie war die Überprüfung der Reproduzierbarkeit dieser Methode und der Vergleich der diagnostischen Leistungsfähigkeit dieses Verfahrens mit derjenigen der visuellen Analyse bei Patienten mit komplex partiellen Anfällen (CPS). Methoden: Der regionale zerebrale Glukoseverbrauch (rCMRGIc) wurde interiktal bei 25 CPS-Patienten und 10 Kontrollen mit 18-F-Fluoro-deoxyglukose (FDG) und der PET-Kamera ECAT EXACT 47 gemessen. Die PET-Aufnahmen wurden visuell auf unilateralen temporalen Hypometabolismus hin beurteilt. Weiterhin wurde der rCMRGIc auf sechs koronaren Schichten mit Hilfe manuell gezeichneter Linienprofile quantifiziert. Aus diesen Profilen wurden Asymmetrieindizes (ASY) in vier temporalen Regionen berechnet und mit den 95%-Konfidenzintervallen des Kontrollkollektivs verglichen. Alle Analysen wurden unabhängig von zwei Auswertern ohne Kenntnis der klinischen Daten ausgeführt. Ergebnisse: Die Übereinstimmung zwischen den beiden Auswertern in Hinsicht auf die Fokus-Lateralisierung war 96% (κ = 0,93) für die visuelle und 100% (κ = 1) für die quantitative Anyalyse. Die Übereinstimmung zwischen der visuellen und quantitativen war gut (κ = 0,8). Schlußfolgerung: Die aus der quantitativen Analyse der Linienprofile des temporalen rCMRGIc resultierenden Diagnosen sind hoch reproduzierbar; gegenüber der visuellen Evaluation besitzt diese Methode jedoch keine signifikante Überlegenheit.

Keywords

PET - epilepsy - F-18-deoxyglucose - temporal line profile - epileptogenic focus

Schlüsselwörter

PET - Epilepsie - F-18-Deoxyglukose - temporale Linienprofile - epilepto-gener Fokus

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