Intraoperative Shear Wave Elastography vs. Contrast-Enhanced Ultrasound for the Characterization and Differentiation of Focal Liver Lesions to Optimize Liver Tumor Surgery

Abstract

Purpose Assessment of intraoperative quantitative shear wave elastography (SWE) and contrast-enhanced ultrasound (CEUS) for the characterization of focal liver lesions (FLLs) during liver surgery using postoperative histopathological results as the gold standard.

Materials and Methods US data of 79 consecutive patients with 98 FLLs who underwent liver surgery between 08/2015 – 06/2017 were prospectively acquired and retrospectively analyzed. Multifrequency linear/T-shaped probes (6 – 9 MHz) were used to store cine loops of at least 5 s and images of B-mode, SWE and CEUS. The first CEUS loop was continuously documented over 1 min. in each case. Quantitative SWE analysis of FLLs was performed by placing 5 regions of interest to measure shear wave speed (m/s) and stiffness (kPa). CEUS was evaluated during the arterial, portal venous and late phase after i. v. bolus injections of 2.4 – 10 ml sulfur hexafluoride microbubbles. Postoperative histopathology after tumor resection or intraoperative biopsy was obtained to confirm findings of SWE and CEUS.

Results Of 98 FLLs in 79 patients (mean age: 58 years sd ± 12y) 88 were malignant and 10 were benign ranging from 0.69 to 15.2 cm in size (mean: 2.8 cm, sd ± 2.25 cm). SWE characterized 73/88 FLLs correctly as malignant and 7/10 as benign using a cut-off value of 2.5 m/s/21.3 kPa (p < 0.0005). The sensitivity was 83 %, specificity 70 %, accuracy 82 %. CEUS could correctly identify 86/88 malignant and 8/10 benign FLLs. The sensitivity was 98 %, specificity 80 %, accuracy 96 %. SWE could correctly identify 2 malignant FLLs which CEUS falsely characterized as benign.

Conclusion Intraoperative CEUS and SWE are excellent tools for the highly accurate visualization, characterization and malignancy assessment of hepatic tumors during liver surgery.

Zusammenfassung

Ziel Evaluation der intraoperativen Scherwellenelastografie (SWE) im Vergleich zum Kontrastmittelultraschall (CEUS) zur Charakterisierung fokaler Leberläsionen (FLLs) während Lebertumoroperationen in Korrelation zur postoperativen Histologie als Goldstandard.

Material und Methode Es erfolgte eine prospektive Datenakquisition und retrospektive Analyse von US-Daten von 79 Patienten mit 98 FLLs, die zwischen August 2015 und Juni 2017 im Rahmen einer Lebertumoroperation einen intraoperativen US erhielten. Multifrequenz-Linear-/T-Sonden (6 – 9 MHz) wurden zur Akquisition von Cineloops > 5 sek. sowie von B-Bild-, SWE- und CEUS-Bildern verwendet. Der erste CEUS-Loop wurde kontinuierlich über 1 min. gespeichert. Mittels 5 Regions-of-interest erfolgte die quantitative SWE-Auswertung der FLLs durch Messung des Shear-wave-speed (m/s) sowie der Festigkeit (kPa). Die CEUS–Evaluation erfolgte während arterieller, portalvenöser und venöser Spätphase nach i. v.-Bolus-Injektionen von 2,4 – 10 ml Sulphurhexaflourid-Mikrobläschen. CEUS- und SWE-Befunde wurden zur postoperativen Histopathologie nach Resektion/intraoperativer Biopsie korreliert.

Ergebnisse Von 98 FLLs bei 79 Patienten (im Mittel 58 Jahre SD ± 12 Jahre) waren 88 maligne und 10 benigne. Die Größe lag zwischen 0,69 und 15,2 cm (im Mittel 2,8 cm, SD ± 2,25 cm). Mittels SWE wurden 73/88 FLLs korrekt als maligne und 7/10 als benigne charakterisiert unter Anwendung eines Cut-off von 2,5 m/s/21,3 kPa (p < 0,0005). Die Sensitivität betrug 83 %, die Spezifität 70 % und die Genauigkeit 82 %. CEUS konnte 86/88 maligne und 8/10 benigne FLLs korrekt charakterisieren. Die Sensitivität betrug 98 %, die Spezifität 80 % und die Genauigkeit 96 %. 2 von CEUS fälschlich als benigne charakterisierte FLLs konnten mittels SWE korrekt als maligne identifiziert werden.

Schlussfolgerung CEUS und SWE während Lebertumoroperationen ermöglichen eine exzellente intraoperative Lebertumordiagnostik durch hochauflösende Visualisierung und genaue Charakterisierung von FLLs.

Key words

intraoperative ultrasound - shear wave elastography - CEUS - liver tumor surgery

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