Detection of hepatocellular carcinomas with near-infrared fluorescence imaging using indocyanine green: its usefulness and limitation

Background Indocyanine green (ICG), an agent for measuring liver function, becomes fluorescent under near-infrared (NIR) light after binding to serum proteins. Hepatocellular carcinoma (HCC) with a deposit of preoperatively administered ICG becomes clearly detectable under ICG fluorography; however, it remains unclear whether this detection method is always reliable. This case series study was designed to clarify the reliability of this method. Methods ICG (0.5 mg/kg) was injected from the 3rd to 28th preoperative day to evaluate hepatic function in 58 patients with HCCs. Preoperative imaging modalities identified 76 HCC foci. The operative fields and resected specimens were observed with an NIR camera system. Preoperatively detected lesions and lesions newly detected by the ICG fluorography were histologically investigated. Results ICG fluorography identified 73 of 76 preoperatively diagnosed HCC lesions. Intraoperative ICG fluorography visualized 47 lesions in 40 patients. The other 26 lesions showing emission were found in the sectioned specimens under NIR observation. Other than preoperatively diagnosed foci, ICG fluorography visualized 35 new lesions, including 6 HCCs, 2 dysplastic nodules and 27 non-neoplastic lesions, such as bile plugs and cysts. The sensitivity of ICG fluorography for HCCs was 96% and its positive predictive value was 71.5%. Conclusions Indocyanine green fluorography is useful to detect HCCs; however, attention should be paid to the fact that HCCs may be occasionally overlooked by this imaging method and that lesions detected by this method are not always neoplastic lesions.