Real-time Tissue Elastography Visualizing Of Hepatocellular Carcinoma-associated Microwave Ablation Lesions

ObjectiveTo evaluate the application of real-time tissue elastography (RTE) in visualizinghepatocellular carcinoma-associated microwave ablation (MWA) lesions before and afterMWA treatment. This study investigated the use of RTE in visualizing human HCC andpost-MWA HCC lesions at different depths and compared imaging of the lesion area withB-mode and CECT/MRI methods in order to assess the application of RTE in evaluatingthe efficacy of liver tumor ablation.MethodsEighteen patients with viable HCC were evaluated by RTE during the period fromJune2011to September2011in this prospective study. Two patients each had two HCCs.Therefore, a total of twenty HCCs were included in this study. Eighteen patients with20lesions were individually examined by B-mode US, RTE and CECT/MRI before andafter ablation. The boundaries of HCC lesions and post-MWA HCCs were determined byB-mode ultrasound (US) and RTE and the area of the enclosed boundary was computed.RTE and B-mode US were performed using a Hitachi HI-VISION900(Hitachi Medical,Chiba, Japan) ultrasound system, equipped with a4-8MHz convex probe (EUP-C532,Hitachi Medical, Japan). The sonoelastography unit is integrated completely into thesystem platform.Prior to MWA, the liver was scanned to locate the HCC detected using analternative cross-sectional imaging technique, such as CECT/MRI. Patients wererequired to hold their breath while moving digital images were registered for30-40s inorder to select five still images. After fitting the still image, a RTE image was obtainedwith a corresponding B-mode image. The lesion boundary observed using B-mode USand RTE was determined and the area of the enclosed boundary was computed. Corresponding RTE images were obtained at the same site5min after MWA and used todetermine the lesion boundary and area. The tumor and ablation zone were evaluated byCECT/MRI scanning performed2-8days before and48hours after MWA. The X-axis(length), Y-axis (width) diameters of HCC lesions and ablation zones were measuredaccording to CECT/CEMRI images. Ablation areas were calculated according to theformula of S=1/4πXY.ResultsThe boundaries of17HCC lesions (diameter0.94-3.48cm) and the correspondingpost-MWA lesions (diameter2.24-3.91cm) were clearly visualized by RTE anddistinguishable from the surrounding normal tissue. No flexible images were obtainedfrom three lesions and their corresponding ablation lesions at a depth of more than6cmfrom the surface. Before ablation, a high correlation was observed in the measurementsof area made using RTE, B-mode US and contrast-enhanced CT/MRI (CECT/MRI), withno significant differences observed between these three groups (r=0.977，P0.0001;r=0.969，P0.0001). After ablation RTE clearly showed the boundaries of ablationlesions and no significant differences were observed in the measurement of area usingRTE and contrast-enhanced CT, with a high correlation between both these groups(r=0.975,P0.0001). Clear visualization of the boundaries of the post-MWA HCCs wasnot possible using B-mode US, with areas obtained for only eight lesions. The differencebetween B-mode US measurements and CECT measurements in the area was statisticallysignificant with no linear correlation between these groups (r=0.337, P>0.05)ConclusionRTE was used for accurate visualization of the boundary and area of HCC andpost-MWA HCC lesions, thus demonstrating the feasibility of the use of RTE forintraoperative evaluation of hepatocellular carcinoma-associated microwave ablation.Therefore, RTE represents a novel, non-invasive and quantitative technique forvisualization of hepatocellular carcinoma-associated microwave ablation (MWA),although the applicability of this approach is limited by the depth of the lesion.