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.
Highlights
Hepatocellular carcinoma (HCC) is one of the most commonly diagnosed malignant tumors in the world, with a globally increasing incidence rate [1]
Using contrast-enhanced ultrasonography (CEUS), we found that all VX2 tumors exhibited the same enhancement pattern: rapid wash-in followed by rapid wash-out including residual tumors following Microwave ablation (MVA), which is the hallmark of HCC
There was a statistically significant difference between the inflammatory reaction band (IRB) and normal liver parenchyma in regional blood velocity and blood flow as estimated by parameter k and A∗k of CEUS quantitative analysis (p = 0:005, 0:023, respectively). These results suggest that MVA had no significant effect on the blood flow of residual tumor, but IRB was immediately formed post-MVA, and the blood flow pattern in IRB increased significantly as compared to normal liver parenchyma
Summary
Hepatocellular carcinoma (HCC) is one of the most commonly diagnosed malignant tumors in the world, with a globally increasing incidence rate [1]. With the total treatment effect, the thermal ablation of HCC is becoming more and more extensively used in the clinic [2]. The local thermal ablation can achieve complete inactivation of HCC nodules with a diameter of less than 3 cm. For single HCC nodules with a diameter of less than 2 cm, local thermal ablation. BioMed Research International may be the preferred treatment, and for single HCC nodules with a diameter of 2-3 cm, local thermal ablation is comparable to surgical resection [3, 4]. For patients with HCC who cannot be surgically resected, thermal ablation therapy could be used for the local control of the tumor and preparing for transplantation [5]. Microwave ablation (MVA), as an important technique of tumor thermal ablation, is widely used in clinics [6]
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