Transcranial Sonography of the Insula: Digitized Image Analysis of Fusion Images with Magnetic Resonance

Abstract

Purpose: Transcranial B-mode sonography (TCS) of brain parenchyma is increasingly used as a diagnostic tool for movement disorders. Accordingly, experimental B-Mode Assist software was developed to enable digitized analysis of the echogenicity of predefined brain regions. The aim of the study was to assess the reproducibility of digitized TCS image analysis of the insula.

Materials and Methods: A total of 130 patients with an indication for neurosonological examination were screened for participation in the study. The insula was imaged from the right temporal bone window using Virtual Navigator and TCS-MRI (magnetic resonance imaging) fusion imaging. All subjects were examined three times by two experienced sonographers. Corresponding images of the insula in the axial thalamic plane were encoded and digitally analyzed. Interclass correlation coefficient (ICC) and Spearman’s rank correlation coefficient were used for the assessment of intra- and inter-reader as well as intra- and inter-investigator reliabilities.

Results: TCS images of 114 patients were evaluated (21 patients with TIA, 53 patients with headache, 18 patients with essential tremor, 22 patients with neurodegerative disease). 16 patients were excluded from analysis due to insufficient bone window. The intra-reader, inter-reader, intra-investigator and inter-investigator ICCs/Spearman’s rank correlation coefficients were 0.995/0.993, 0.937/0.921, 0.969/0.961 and 0.875/0.858, resp.

Conclusion: The present study demonstrates a high reliability to reproduce echogenicity values of the insula using digitized image analysis and TCS-MRI fusion images with almost perfect intra-reader, inter-reader, intra-investigator and inter-investigator agreement.

Zusammenfassung

Ziel: Die transkranielle B-Bild-Sonografie (TCS) des Hirnparenchyms wird zunehmend als diagnostische Methode bei Bewegungsstörungen eingesetzt. Deshalb wurde die experimentelle „B-Mode Assist“ Software entwickelt, um die digitalisierte Analyse der Echogenität definierter Hirnstrukturen zu ermöglichen. In dieser Studie wurde die Reproduzierbarkeit der digitalisierten TCS-Bildanalyse der Insula untersucht.

Material und Methoden: Insgesamt 130 Patienten mit Indikation zur neurosonologischen Untersuchung wurden für die Teilnahme an der Studie rekrutiert. Die Darstellung der Insula erfolgte vom rechten temporalen Knochenfenster aus mittels virtueller Navigation und TCS-MRT (Magnetresonanz-Tomografie)-Fusionsbildgebung. Alle Patienten wurden dreifach von zwei erfahrenen Ultraschallanwendern untersucht. Die korrespondierenden Bilder der Insula in der axialen thalamischen Ebene wurden kodiert und digital analysiert. Der Interklassenkorrelationskoeffizient (ICC) und der Spearman-Rangkorrelationskoeffizient wurden für die Beurteilung der Intra-Reader-/Inter-Reader- und der Intra-Investigator-/Inter-Investigator-Reliabilität angewandt.

Ergebnisse: Es wurden TCS-Bilder von 114 Patienten bewertet (21 Patienten mit TIA, 53 Patienten mit Kopfschmerz, 18 Patienten mit essentiellem Tremor, 22 Patienten mit neurodegenerativer Erkrankung); 16 Patienten wurden wegen insuffizienter Knochenfenster von der Analyse ausgeschlossen. Die ICCs betrugen 0,995 (Intra-Reader) und 0,937 (Inter-Reader), sowie 0,969 (Intra-Investigator) und 0,875 (Inter-Investigator). Die Spearman-Rangkorrelationskoeffizienten betrugen 0,993 (Intra-Reader) und 0,921 (Inter-Reader) sowie 0,961 (Intra-Investigator) und 0,858 (Inter-Investigator).

Schlussfolgerung: Die aktuelle Studie zeigt eine hohe Verlässlichkeit bei der Reproduktion der Echogenitätswerte der Insula bei Einsatz von digitalisierter Bildanalyse und TCS-MRT-Fusionsbildgebung mit nahezu perfekten Intra-/Inter-Reader- sowie Intra-/Inter-Investigator-Reliabilitäten.

Key words

transcranial sonography - insula - reproducibility - fusion imaging - virtual navigator

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