Diagnostic Value of Quantitative EUS Elastography for Malignant Pancreatic Tumors: Relationship with Pancreatic Fibrosis

Zusammenfassung

Ziel: Die endosonografische Elastografie (EUS-Elastografie) kann zur Bestimmung der Gewebehärte bei Pankreasläsionen eingesetzt werden. Allerdings ist die Interpretation der Bilder in den meisten Fällen von der subjektiven Einschätzung des Untersuchers abhängig. Ziel dieser Arbeit war die Entwicklung einer quantitativen Auswertung der EUS-Elastografie-Daten. Zusätzlich sollte die Korrelation der Elastografie mit der Fibrosebildung bei Pankreas-Malignomen untersucht werden. Material und Methoden: 86 Patienten mit Pankreas-Malignomen und 28 pankreasgesunde Patienten als Kontrollgruppe wurden mittels EUS-Elastografie untersucht. Zur Quantifizierung der EUS-Elastografie erfolgte in Videosequenzen eine Analyse der mittleren Histogrammwerte für die Farben Rot, Grün und Blau. Die Fibrosebildung konnte von 36 Patienten mit Pankreasmalignom mittels quantitativer Morphometrie am histologischen Präparat bestimmt werden. Ergebnisse: Der mittlere Histogrammwert für Rot/Grün/Blau (RGB) war in der Malignomgruppe signifikant höher als in der Kontrollgruppe (14,0 ± 0,4 vs. 11,5 ± 0,9, p = 0,0085). In der Analyse der Einzelfarben zeigte sich ein hochsignifikanter Unterschied zwischen beiden Gruppen jeweils für die Farben Rot, Grün und Blau (p < 0,0001). Für die Farbe Blau ergab sich eine 100 %ige Spezifität und Sensitivität in der Unterscheidung zwischen Tumorgruppe und gesunder Kontrollgruppe. Es gab keine Korrelation zwischen Fibrosegehalt und mittleren Farb-Histogrammwerten. Schlussfolgerung: Eine quantitative EUS-Elastografie durch Analyse von mittleren Histogramm-Farbwerten erlaubt eine klare Unterscheidung zwischen malignen Pankreasläsionen und normalem Pankreasgewebe. Die erhöhte Gewebehärte bei Pankreasmalignomen scheint nicht durch einen vermehrten Fibrosegehalt bedingt zu sein.

Abstract

Purpose: EUS elastography has been used to facilitate the diagnosis of pancreatic cancer, but as yet the interpretation of this procedure has been largely subjective. The present study has been designed to validate a quantitative approach for the analysis of EUS elastography, and to assess its relationship with pancreatic fibrosis. Materials and Methods: 86 patients with malignant pancreatic masses and 28 control subjects without any evidence of pancreatic diseases were examined by EUS elastography. EUS video sequences were subjected to a quantitative analysis based on mean hue histogram analysis. Pancreatic fibrosis was determined by quantitative morphometry in tissue specimens from 36 patients. Results: The mean RGB (red, green, blue) value was significantly higher in the cancer patients compared to the controls (14.0 ± 0.4 vs. 11.5 ± 0.9; p = 0.0085), albeit with significant overlap between the groups. In contrast, a much sharper separation between the groups was obtained based on the individual color values for blue, green and red (p < 0.0001, respectively). By these means, 100 % sensitivity and specificity for the distinction between tumor and normal tissue was obtained for the blue color value, while the red and green color values were less discriminative. The fractional fiber content of the tumors was unrelated to the respective hue histogram color values. Conclusion: Quantitative EUS elastography allows for clear differentiation between malignant pancreatic tumors and normal tissue. Using this approach, we demonstrated that the stiffness of pancreatic tumors is largely independent of their fiber content.

Key words

pancreas - endoscopy - ultrasound

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