Radiologic-pathologic correlation of three-dimensional shear-wave elastographic findings in assessing the liver ablation volume after radiofrequency ablation

AIM: To evaluate the usefulness of three-dimensional(3D) shear-wave elastography(SWE) in assessing the liver ablation volume after radiofrequency(RF) ablation.METHODS: RF ablation was performed in vivo in 10 rat livers using a 15-gauge expandable RF needle. 3D SWE as well as B-mode ultrasound(US) were performed 15 min after ablation. The acquired 3D volume data were rendered as multislice images(interslice distance: 1.10 mm), and the estimated ablation volumes were calculated. The 3D SWE findings were compared against digitized photographs of gross pathological and histopathological specimens of the livers obtained in the same sectional planes as the 3D SWE multislice images. The ablation volumes were also estimated by gross pathological examination of the livers, and theresults were then compared with those obtained by 3D SWE.RESULTS: In B-mode US images, the ablation zone appeared as a hypoechoic area with a peripheral hyperechoic rim; however, the findings were too indistinct to be useful for estimating the ablation area. 3D SWE depicted the ablation area and volume more clearly. In the images showing the largest ablation area, the mean kPa values of the peripheral rim, central zone, and nonablated zone were 13.1 ± 1.5 kPa, 59.1 ± 21.9 kPa, and 4.3 ± 0.8 kPa, respectively. The ablation volumes depicted by 3D SWE correlated well with those estimated from gross pathological examination(r2 = 0.9305, P = 0.00001). The congestion and diapedesis of red blood cells observed in histopathological examination were greater in the peripheral rim of the ablation zone than in the central zone.CONCLUSION: 3D SWE outperforms B-mode US in delineating ablated areas in the liver and is therefore more reliable for spatially delineating thermal lesions created by RF ablation.