Efficacy of combining electric-field and coronal-plane imaging to obtain ultrasound-ultrasound fusion images in monopolar radiofrequency ablation for patients with liver cancer

Abstract

Aim For radiofrequency ablation to treat patients diagnosed with liver cancer, the ablation area cannot be envisaged beforehand, even by experts. This study aimed to assess the clinical feasibility of applying a combination of electric (E)-field and coronal (C)-plane simulations to ultrasound-ultrasound (US-US) fusion images. Methods The study protocols were approved by the institutional ethics committee. Between October 2017 and July 2019, 151 patients with 151 hepatocellular carcinoma nodules (80 treated with navigation images and 71 without navigation images) were retrospectively compared in this cross-sectional study. The E-field, which is a simulated image that predicts the ablation area, was applied to the US-US fusion images. The C-plane is defined as a sagittal plane in relation to the original 2-D US images. The positions of each E-field area in the maximum cross-sectional area of the tumor were easily identified from C-plane results. The primary end-point of this study was achievement of an adequate safety margin (greater than 5 mm). The sphericity of the ablation volume was used as a secondary end-point. Results The rate of achieving a sufficient safety margin was significantly higher in the group treated with navigation images (71/80) than in the group treated without navigation images (31/71,P < 0.001). The median sphericity was 0.55 with navigation images and 0.42 without navigation images (P < 0.001). Conclusion Using the combination of an E-field and a C-plane on US-US fusion images can be a feasible method for acquiring a sufficient safety margin.