Virtuelle Färbeverfahren in der Endoskopie

Einführung

Eine Färbung der Schleimhaut des Gastrointestinaltraktes wird seit den 1960er und 1970er Jahren eingesetzt, um die optischen Möglichkeiten der fiberoptischen Endoskopie zu erweitern [1] [2]. Ziel der Färbung war bereits damals, die Detektion von Läsionen zu verbessern bzw. die Charakterisierung von entdeckten Befunden zu optimieren. Die intravitale Färbung durch Auftragen von Farbstoffen geht allerdings mit einem erhöhten Zeitaufwand einher, und ein Zurückkehren zum konventionellen weißlichtendoskopischen Bild ist nach Anfärben der Schleimhaut naturgemäß nicht mehr möglich. Es erscheint konsequent, dass Techniken entwickelt wurden, die diese chromoendoskopischen Effekte in das optische System des Endoskops selbst integrieren.

Technische Systeme. Derzeit stehen mehrere Systeme zur Verfügung, die durch optische Effekte eine Bildoptimierung leisten sollen: NBI (Narrow-Band Imaging, Olympus, Tokyo, Japan), FICE (Fujinon Intelligent Chromo Endoscopy, Fujifilm, Tokyo, Japan) und i-scan (Pentax, Tokyo, Japan) (Tab. [1, ]Abb. [1]). Dabei stellt Ersteres ein optisches Filterverfahren dar, die zwei Letzteren nehmen eine digitale Nachbearbeitung des Bildes vor (sog. digitales Postprocessing).

Tabelle 1 Virtuelle Färbemethoden in der flexiblen Endoskopie.

Virtuelle Färbemethode	Hersteller	Verarbeitung des Lichtsignals
NBI (Narrow-Band Imaging)	Olympus	Filterverfahren, Verwendung von Licht ausgewählter Lichtspektren
FICE (Fujinon Intelligent Chromo Endoscopy)	Fujinon / FujiFilm	digitale Nachbearbeitung des Bildsignals
i-scan	Pentax	digitale Nachbearbeitung des Bildsignals
AFI (Autofluorescence Imaging)	Olympus	Anregung endogener Fluorophore

Abb. 1 Bildoptimierung durch chromoendoskopische Effekte. a Olympus. b FujiFilm. c Pentax.

Mit der NBI-Technik werden kleine mukosale Gefäße optimiert dargestellt und durch eine Einschätzung des Gefäßmusters („vascular pattern intensity“ oder „microvascular density“) wird die Charakterisierung des Befundes anhand dieser Kriterien ermöglicht [3]. Adenome des Kolons zeigen beispielsweise eine höhere kapilläre Dichte als hyperplastische Polypen. Die digitale Nachverarbeitung (FICE, i-scan) zielt ebenfalls darauf ab, die Oberflächenstrukturen optimiert wiederzugeben. Ein weiteres Verfahren, das AFI (Autofluorescence Imaging), bedient sich der Anregung endogener Fluorophore und soll als sog. „Rote-Flagge“-Technik die Aufmerksamkeit auf relevante Befunde leiten oder diese in ihrer Dignität einordnen helfen. Hierbei stellen sich beispielsweise Adenome des Kolons in Magenta dar, wohingegen hyperplastische Polypen grün abgebildet werden.

¹ Medizinische Klinik 1, Klinikum der J. W. Goethe-Universität, Frankfurt

² Interventionelle Endoskopie, Medizinische Klinik 1, Universitätsklinikum Erlangen

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