Early Identification of Residual Tumors following Microwave Ablation Using Contrast-Enhanced Ultrasonography in a Rabbit VX2 Liver Cancer Model

Abstract

Objective. It is difficult to evaluate the ablation effect immediately after thermal ablation of liver cancer by clinical imaging methods, due to the immediate formation of an annular inflammatory reaction band (IRB). This study is aimed at exploring the early identification indicators of the IRB and residual tumor postmicrowave ablation (MVA) using contrast-enhanced ultrasonography (CEUS). Methods. MVA was used to inactivate part of the tumor nodules in rabbit VX2 liver cancer models, leading to the coexistence of the IRB with residual tumors. Quantitative analysis of the perfusion parameters of the tumor and ablation zone was performed using CEUS, followed by liver biopsy and VEGFR-2 immunohistochemical staining. Results. All rabbits successfully tolerated VX2 tumor inoculation and MVA operation. No statistically significant difference existed between the IRB vs. residual tumors, the IRB vs. junctional areas, and residual tumors postablation vs. VX2 tumors before ablation in regional blood volume, blood velocity, and blood flow estimated by parameters A, k, and A∗k of CEUS quantitative analysis. There was a statistically significant difference between the IRB and normal liver parenchyma in regional blood velocity and blood flow (p=0.005 and p=0.023, respectively). Normal liver parenchyma showed nonspecific VEGFR-2 staining, while VX2 tumor before ablation and residual tumor after ablation both showed positive VEGFR-2 staining; the necrosis zone showed negative staining by VEGFR-2 immunohistochemical staining. Conclusion. MVA had no significant effect on the residual tumor hemodynamics. The blood flow in the IRB increased significantly as compared to normal liver parenchyma, resembling tumor hemodynamic patterns. CEUS can detect residual tumors immediately postablation only when they protrude from the annular-shaped IRB. In addition, VEGFR-2 targeted CEUS may have a great potential for detecting residual tumor after thermal ablation of hepatocellular carcinoma.

Quantitative Analysis of Contrast-Enhanced Ultrasound That Can Be Used to Evaluate Angiogenesis during Patellar Tendon Healing in Rats

“…CEUS can provide real-time, continuous dynamic imaging, and TIC can provide a quantitative analysis of local contrast enhancement [23]. As displayed in Figures 2(c) and 3(a), the basic intensity curves displayed in the control group reflected the absence of blood perfusion in tendons, which was confirmed by the absence of microvessels in immunohistochemistry.…”

Feasibility of contrast-enhanced ultrasonography (CEUS) in evaluating renal microvascular perfusion in pediatric patients

“…In summary, based on four parameters (A, B, k and TtoPk) derived from CEUS quantitative analysis, the reproducibility of CEUS in evaluating renal microvascular perfusion in pediatric patients was verified in this study. Among these parameters, A and k can serve as an estimation of regional blood volume and mean blood velocity, respectively [ 19 ]. Furthermore, this study showed that, with the progression of pediatric CKD, the value of parameter A in the renal cortex decreased, and the difference of the value of parameter k between renal cortex and medulla also tended to decrease.…”

“…Quantitative analysis of CEUS images was based on time-intensity curve (TIC) fittings using specialized software equipped with GE Logiq E9 system [ 19 ]. Six regions of interest (ROIs) with identical areas were manually set: three in the renal cortex and three in the renal medulla, which were placed at approximately the same depth separately (Fig.…”

“…where the following TIC quantitative parameters were involved: [ 1 ] A, the plateau value as an estimate of the regional blood volume; [ 2 ] B, the baseline; [ 3 ] k, the slope of the ascending TIC as an estimate of mean blood velocity; [ 4 ] time to peak intensity (TtoPk), defined as the time from the start of enhancement to the time when contrast agent microvascular perfusion reached the peak [ 19 ]. All parameters were acquired by the same investigator (HM.…”

Ultrasound localization microscopy

“…Additionally, Yi et al proposed to use ULM for the evaluation of thermal ablation treatment at liver tumors to differentiate residual tumor from a so-called inflammatory reaction band (IRB) [73] . Acute responses to treatment may cause increased perfusion of the tissue and a corresponding enhanced brightness in CEUS images that is difficult to distinguish from that of a residual tumor [74] , [75] . The expected differences in the morphology and function of the microvasculature between residual tumor and IRB could likely be better characterized by ULM.…”