title: Feasibility of Extracted-Overlay Fusion Imaging for Intraoperative Treatment Evaluation of Radiofrequency Ablation for Hepatocellular Carcinoma.
abstract: OBJECTIVE
  Extracted-overlay fusion imaging is a novel computed tomography/magnetic resonance-ultrasonography (CT/MR-US) imaging technique in which a target tumor with a virtual ablative margin is extracted from CT/MR volume data and synchronously overlaid on US images. We investigated the applicability of the technique to intraoperative evaluation of radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC).
  
  
  METHODS
  This retrospective study analyzed 85 HCCs treated with RFA using extracted-overlay fusion imaging for guidance and evaluation. To perform RFA, an electrode was inserted targeting the tumor and a virtual 5-mm ablative margin overlaid on the US image. Following ablation, contrast-enhanced US (CEUS) was performed to assess the ablative margin, and the minimal ablative margins were categorized into three groups: (I) margin <0 mm (protrusion), (II) margin 0 to <5 mm, and (III) margin ≥5 mm. Margin assessment was based on the positional relationship between the overlaid tumor plus margin and the perfusion defect of the ablation zone. Tumors in group I underwent repeat ablation until they were in groups II or III. The final classifications were compared with those obtained by retrospectively created fusion images of pre- and post-RFA CT or MR imaging (CT-CT/MR-MR fusion imaging).
  
  
  RESULTS
  Treatment evaluation was impossible using CEUS in six HCCs because the tumors were located far below the body surface. Of the remaining 79 HCCs, the categorizations of minimal ablative margins between CEUS extracted-overlay fusion imaging and CT-CT/MR-MR fusion imaging were in agreement for 72 tumors (91.1%) (Cohen's quadratic-weighted kappa coefficient 0.66, good agreement, p<0.01).
  
  
  CONCLUSIONS
  Extracted-overlay fusion imaging combined with CEUS is feasible for the evaluation of RFA and enables intraoperative treatment evaluation without the need to perform contrast-enhanced CT.
authors: Department of Gastroenterology, Ikeda Municipal Hospital, Ikeda, Japan.
authors: Yuki
authors: Y
authors: Makino
authors: Department of Gastroenterology, Ikeda Municipal Hospital, Ikeda, Japan.
authors: Yasuharu
authors: Y
authors: Imai
authors: Department of Gastroenterology, Ikeda Municipal Hospital, Ikeda, Japan.
authors: Takumi
authors: T
authors: Igura
authors: Department of Gastroenterology, Ikeda Municipal Hospital, Ikeda, Japan.
authors: Sachiyo
authors: S
authors: Kogita
authors: Department of Gastroenterology, Ikeda Municipal Hospital, Ikeda, Japan.
authors: Yoshiyuki
authors: Y
authors: Sawai
authors: Department of Gastroenterology, Ikeda Municipal Hospital, Ikeda, Japan.
authors: Kazuto
authors: K
authors: Fukuda
authors: Department of Gastroenterology, Ikeda Municipal Hospital, Ikeda, Japan.
authors: Takayuki
authors: T
authors: Iwamoto
authors: Department of Gastroenterology, Ikeda Municipal Hospital, Ikeda, Japan.
authors: Junya
authors: J
authors: Okabe
authors: Department of Radiology, Ikeda Municipal Hospital, Ikeda, Japan.
authors: Manabu
authors: M
authors: Takamura
authors: Department of Radiology, Ikeda Municipal Hospital, Ikeda, Japan.
authors: Norihiko
authors: N
authors: Fujita
authors: Department of Radiology, Osaka University Graduate School of Medicine, Suita, Japan.
authors: Masatoshi
authors: M
authors: Hori
authors: Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Japan.
authors: Tetsuo
authors: T
authors: Takehara
authors: Department of Gastroenterology and Hepatology, Kinki University Faculty of Medicine, Osaka-Sayama, Japan.
authors: Masatoshi
authors: M
authors: Kudo
authors: Department of Radiology, Kinki University Faculty of Medicine, Osaka-Sayama, Japan.
authors: Takamichi
authors: T
authors: Murakami
keywords: Contrast-enhanced ultrasonography; Extracted-overlay fusion imaging; Hepatocellular carcinoma; Multimodality fusion imaging; Radiofrequency ablation