Evaluation of the use of intraoperative real-time virtual sonography with sonazoid enhancement for detecting small liver metastatic lesions after chemotherapy in hepatic resection

Background: Systemic chemotherapy can drastically downsize metastatic liver tumors and these small liver lesions could sometimes be difficult for surgeons to detect during hepatectomy. We assessed the usefulness of intraoperative real-time virtual sonography (RVS) with contrast-enhanced ultrasonography (CEUS) using 'Sonazoid' contrast agent (RVS-CEUS). Methods: We performed the intraoperative RVS-CEUS technique on 10 tumor lesions in six cases, which were scheduled for hepatic resection of < 10 mm in diameter in our liver metastases series. These lesions were preoperatively diagnosed by contrast enhanced-computed tomography (CE-CT) or Gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (EOB-MRI). We assessed the detectability of a tumor with RVS-CEUS during surgery and compared it with that of preoperative CE-CT or EOB-MRI. Results: Detectability of RVS-CEUS for 10 small lesions was 90% (n = 9/10) and that of other preoperative modalities were 50% (n = 5/10, CE-CT) and 100% (n = 10/10, EOB-MRI). Minimum tumor size detected was 3.0 mm in diameter, and maximum depth of detection with RVS-CEUS was 43.5 mm; these results could be an advantage when compared with other intraoperative diagnostic modalities. Conclusion: Intraoperative RVS-CEUS was useful for detecting small metastatic liver lesions after chemotherapy and could be an effective intraoperative diagnostic technique for hepatic resection of a size < 10 mm.