Strain Assessment in Surgically Resected Inflammatory and Neoplastic Bowel Lesions

Abstract

Purpose: To investigate whether ultrasound-based strain imaging can discriminate between colorectal adenocarcinomas and stenotic Crohn’s lesions in newly resected surgical specimens.

Materials and Methods: Resected surgical specimens from 27 patients electively operated for colorectal tumors or stenotic lesions from Crohn’s disease were prospectively examined with ultrasonography using a Hitachi HV 900 US scanner with real-time elastography (RTE). Three different methods were applied to assess tissue strain: A four-level categorical visual classification, a continuous visual analog scale (VAS, 0 – 100) and a strain ratio (SR) measurement between the lesion and surrounding reference tissue. The imaged sections were marked and subsequently examined by a pathologist. Results from RTE were evaluated according to diagnosis, degree of fibrosis, inflammatory parameters, tumor stage and grade.

Results: 16 sections from Crohn’s lesions, 18 sections from adenocarcinomas and 4 sections from adenomas were examined. Both adenocarcinomas and Crohn’s lesions were found to be harder than the surrounding tissue, but they could not be discriminated from each other by any of the strain imaging evaluation methods. All adenocarcinomas had significantly higher strain ratios than adenomas. The categorical classification differentiated poorly between Crohn’s lesions, adenocarcinomas and adenomas. Categorical evaluation and VAS score showed fair interobserver agreement. SR measurements provided semi-quantitative strain data and added improved information about elasticity properties, despite substantial intra-observer variation.

Conclusion: Sonoelastography with SR measurements and visual evaluation of strain differences could not differentiate stenotic Crohn’s lesions from adenocarcinomas in resected bowel specimens. A small number of adenomas were found to be significantly softer than adenocarcinomas using the same evaluation methods. The tumor stage or grade did not have a significant impact on the elastography results.

Zusammenfassung

Ziel: Untersuchung, inwieweit ultraschallbasiertes Strain-Imaging zwischen kolorektalen Karzinomen und stenotischen Crohn-Herdläsionen bei frisch resezierten chirurgischen Proben unterscheiden kann.

Material und Methoden: Resezierte chirurgische Proben von 27 Patienten nach Operation wegen kolorektaler Tumore oder stenotischer Morbus-Crohn-Läsionen wurden prospektiv mit einem Hitachi HV-900-US-Gerät mit Echtzeit-Elastografie (RTE) untersucht. Zur Bestimmung der Gewebefestigkeit wurden drei verschiedene Methoden angewandt: Eine vierstufige kategorische visuelle Klassifizierung, eine kontinuierliche visuelle Analogskala (VAS, 0 – 100) und Bestimmung der Strain-Ratio (SR) zwischen dem Herd und dem umliegenden Referenzgewebe. Die abgebildeten Schnitte wurden markiert und sofort von einem Pathologen untersucht. Die Ergebnisse der RTE wurden je nach Diagnose, Fibrosegrad, Entzündungsparametern und Stadium und Grad des Tumors bewertet.

Ergebnisse: Es wurden 16 Schnitte von Morbus-Crohn-Herdläsionen, 18 von Adenokarzinomen und 4 von Adenomen untersucht. Sowohl Adenokarzinome als auch Crohn-Herdläsionen waren steifer als das umliegende Gewebe, aber sie konnten mit keiner der Strain-Imaging-Bewertungsmethoden voneinander unterschieden werden. Alle Adenokarzinome hatten eine signifikant höhere Strain-Ratio als Adenome. Die kategorische Klassifizierung konnte nur schlecht zwischen Crohn-Herdläsionen, Adenokarzinomen und Adenomen differenzieren. Kategorische Bewertung und VAS-Auswertung zeigten eine gute Interobserverübereinstimmung. Die SR-Messungen führten zu semiquantitativen Strain-Werten und lieferten zusätzliche Informationen über die elastischen Eigenschaften, trotz einer beträchtlichen Intraobservervariation.

Schlussfolgerung: Die Sonoelastografie mit SR-Bestimmungen und visueller Bewertung der Strain-Unterschiede kann bei resezierten Darmproben nicht zwischen stenotischen Crohn-Herdläsionen und Adenokarzinomen unterscheiden. Eine kleine Zahl an Adenomen zeigte sich signifikant weicher als Adenokarzinome unter Verwendung der gleichen Bewertungsmethoden. Stadium und Grad des Tumors hatten keinen signifikanten Einfluss auf die elastografischen Befunde.

Key words

ultrasound - adenocarcinoma - Crohn’s disease - strain ratio - ex-vivo

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