Real-Time Elastography of Hepatic Thermal Lesions In Vitro: Histopathological Correlation

Abstract

Purpose: To evaluate the reliability of elastography, a new ultrasonographic method, for delineating thermal lesion boundaries in porcine liver tissue by comparing lesion dimensions determined by real-time elastography with the findings at gross pathology.

Materials and Methods: A total of 15 thermal lesions with diameters ranging from 17 to 60 mm were created using radiofrequency ablation (RFA). Color-coded elastography was performed by one experienced examiner, using a 6 – 15 MHz high frequency linear transducer (LOGIQ E9, GE). Lesions were examined using B-mode and real-time elastography (RTE). Lesion detection, delineation and size were assessed using B-mode and RTE immediately after each thermal ablation ( < 5 min). Measurements of the sections representing the same image plane used for elastography were taken during pathologic examination and compared to the measurements obtained from the elastograms.

Results: In our sample a statistically significant correlation in vitro between RTE and pathological measurements with respect to the lesion’s principal axis and area (r² = 0.9338 long axis, r² = 0.8998 short axis and r² = 0.9676 area) was found. Overall, elastography slightly underestimated the lesion size, as judged by the digitalized pathologic images.

Conclusion: These results support that RTE outperforms conventional B-mode ultrasound and could potentially be used for the routine assessment of thermal therapies.

Zusammenfassung

Ziel: Überprüfung, inwieweit es in vitro möglich ist, mit der Real-time-Elastografie (RTE) als neue Ultraschallmethode, Läsionen nach RFA zu beurteilen im Vergleich zur Histopathologie am Schweinemodell.

Material und Methoden: Insgesamt wurden 15 Ablationsläsionen mit einem Diameter von 17 – 60 mm nach RFA untersucht. Alle Untersuchungen mittels RTE wurden von einem erfahrenen Untersucher mit einem hochauflösenden Linearschallkopf (6 – 15 MHz, LOGIQ E9, GE) durchgeführt. Die Ablationsdefekte wurden im B-Bild und mit der RTE beurteilt. Beurteilt wurden die Detektion und Abgrenzbarkeit unmittelbar nach der RFA ( < 5 min). Die Läsionsausdehnung in der RTE wurde mit dem Ablationsdefekt in der Histopathologie verglichen.

Ergebnisse: Die statistische Auswertung zeigte eine signifikante Korrelation zwischen Defektbeurteilung mittels RTE und der Histopathologie, sowohl bei Messungen des Diameters als auch bei der Läsionsfläche (r² = 0,9338 lange Achse, r² = 0,8998 kurze Achse sowie r² = 0,9676 Flächenausdehnung). Insgesamt unterschätzte die RTE die Läsionsgröße im Vergleich zur Histopathologie leicht.

Schlussfolgerung: Mit der RTE bietet sich eine Möglichkeit eines verbesserten Monitorings von RFA-Läsionen in der Routine. Mit der RTE bietet sich die Möglichkeit einer routinemäßig verbesserten Beurteilung der RFA gegenüber dem konventionellen B-Bild.

Key words

abdomen - liver - radiofrequency (RF) ablation - technology assessment

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