Monitoring During Hepatic Radiofrequency Ablation (RFA): Comparison of Real-Time Ultrasound Elastography (RTE) and Contrast-Enhanced Ultrasound (CEUS): First Clinical Results of 25 Patients

Abstract

Purpose: To evaluate the reliability of ultrasound elastography for delineating thermal ablation defects post-radiofrequency ablation (RFA) by comparing lesion dimensions determined by real-time elastography (RTE) with the findings of contrast-enhanced ultrasound (CEUS).

Materials and Methods: A total of 21 malignant liver tumors were percutaneously ablated using RFA. Color-coded elastography and CEUS were performed by one experienced examiner, using a 1 – 5 MHz multi-frequency convex transducer (LOGIQ E9, GE). Lesions were examined using CEUS and real-time elastography (RTE) to assess ablation defects. Measurements of lesions (long axis, short axis, and area) representing the same image plane used for elastography were taken during CEUS examination and compared to the measurements obtained from the elastograms. All measurements were performed by two independent observers.

Results: A statistically significant correlation in vivo between RTE and CEUS measurements with respect to the lesion’s principal axis and area (r = 0.876 long axis, r = 0.842 short axis and r = 0.889 area) was found. Inter-rater reliability assessed with the concordance correlation coefficient was substantial for all measurements (ρc ≥ 0.96) Overall, elastography slightly underestimated the lesion size, as judged by the CEUS images.

Conclusion: These results support that RTE could potentially be used for the routine assessment of thermal ablation therapies.

Zusammenfassung

Ziel: Überprüfung, inwieweit es in vivo möglich ist, mit der Real-Time-Elastografie (RTE), Läsionen nach RFA zu beurteilen im Vergleich zum kontrastmittelverstärkten Ultraschall (CEUS).

Material und Methoden: Insgesamt wurden 21 maligne Lebertumoren perkutan mit Hilfe der RFA abladiert. Die postinterventionelle farbkodierte Elastografie sowie die CEUS-Untersuchungen wurden von einem erfahrenen Untersucher mit einem Konvexschallkopf (1 – 5 MHz, LOGIQ E9, GE) durchgeführt. Die Ablationsdefekte wurden im CEUS und mit der RTE von zwei unabhängigen Auswerten beurteilt. Die Läsionsgrößen (lange-, kurze Achse sowie Fläche) wurden sowohl im CEUS, als auch in der RTE bestimmt. Die Läsionsausdehnung in der RTE wurde mit dem Ablationsdefekt im CEUS korreliert.

Ergebnisse: Die statistische Auswertung zeigte eine signifikante Korrelation zwischen Defektbeurteilung mittels RTE und des CEUS, sowohl bei Messungen des Diameters als auch bei der Läsionsfläche (r = 0,876 lange Achse, r = 0,842 kurze Achse sowie r = 0,889 Flächenausdehnung). Interrater-Reliabilität der Messungen war stabil mit einem Konkordanz-Korrelationskoeffizienten von ρc ≥ 0,96. Insgesamt unterschätzte die RTE die Läsionsgröße im Vergleich zur CEUS leicht.

Schlussfolgerung: Die RTE bietet eine potentielle Möglichkeit des Monitorings von RFA-Läsionen.

Key words

abdomen - liver - ablation procedures - interventional procedures

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