Retrospective Study
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Hepatol. Jun 27, 2021; 13(6): 699-708
Published online Jun 27, 2021. doi: 10.4254/wjh.v13.i6.699
Comparison of unenhanced magnetic resonance imaging and ultrasound in detecting very small hepatocellular carcinoma
Kazuo Tarao, Akito Nozaki, Hirokazu Komatsu, Tatsuji Komatsu, Masataka Taguri, Katsuaki Tanaka, Testuo Yoshida, Hideki Koyasu, Makoto Chuma, Kazushi Numata, Shin Maeda
Kazuo Tarao, Tarao's Gastroenterological Clinic, Yokohama 241-0821, Japan
Akito Nozaki, Makoto Chuma, Kazushi Numata, Gastroenterological Center, Yokohama City University Medical Center, Yokohama 232-0024, Japan
Hirokazu Komatsu, Department of Gastroenterology, Yokohama Municipal Citizen's Hospital, Yokohama 240-0855, Japan
Tatsuji Komatsu, Department of Clinical Research, National Hospital Organization, Yokohama Medical Center, Yokohama 245-8575, Japan
Masataka Taguri, Department of Data Science, Yokohama City University, Yokohama 236-0004, Japan
Katsuaki Tanaka, Department of Gastroenterology, Hadano Red Cross Hospital, Hadano City 257-0017, Japan
Testuo Yoshida, Department of Radiology, Ashigarakami Hospital, Yokohama 258-0003, Japan
Hideki Koyasu, Department of Radiology, Koyasu Clinic, Yokohama 241-0821, Japan
Shin Maeda, Department of Gastroenterology, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan
Author contributions: Tarao K summarized the data and wrote the paper; Nozaki A, Komatsu H, Komatsu T, Tanaka K, Chuma M, Numata K, and Maeda S followed up the patients; Taguri M conducted statistical analysis; Yoshida T and Koyasu H made suggestions regarding the MRI technique.
Institutional review board statement: The study was reviewed and approved by the Ethics Committee of Yokohama Municipal Citizen's Hospital Institutional Review Board (Approval No. 21-02-01).
Informed consent statement: This study was performed after approval by the respective institutional review boards. The study used anonymous clinical data that were obtained after each patient agreed to treatment by written consent.
Conflict-of-interest statement: There are no conflicts of interest to disclose.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Corresponding author: Kazuo Tarao, PhD, Chief Doctor, Tarao's Gastroenterological Clinic, Taiyo-building3F, Futamatagawa2-58-6, Asahi-ku, Yokohama 241-0821, Japan.
Received: February 4, 2021
Peer-review started: February 4, 2021
First decision: February 24, 2021
Revised: March 9, 2021
Accepted: May 20, 2021
Article in press: May 20, 2021
Published online: June 27, 2021

In hepatocellular carcinoma (HCC), detection and treatment prior to growth beyond 2 cm are important as a larger tumor size is more frequently associated with microvascular invasion and/or satellites. In the surveillance of very small HCC nodules (≤ 2 cm in maximum diameter, Barcelona clinical stage 0), we demonstrated that the tumor markers alpha-fetoprotein and PIVKA-Ⅱ are not so useful. Therefore, we must survey with imaging modalities. The superiority of magnetic resonance imaging (MRI) over ultrasound (US) to detect HCC was confirmed in many studies. Although enhanced MRI is now performed to accurately diagnose HCC, in conventional clinical practice for HCC surveillance in liver diseases, unenhanced MRI is widely performed throughout the world. While, MRI has made marked improvements in recent years.


To make a comparison of unenhanced MRI and US in detecting very small HCC that was examined in the last ten years in patients in whom MRI and US examinations were performed nearly simultaneously.


In 394 patients with very small HCC nodules, those who underwent MRI and US at nearly the same time (on the same day whenever possible or at least within 14 days of one another) at the first diagnosis of HCC were selected. The detection rate of HCC with unenhanced MRI was investigated and compared with that of unenhanced US.


The sensitivity of unenhanced MRI for detecting very small HCC was 95.1% (97/102, 95% confidence interval: 90.9-99.3) and that of unenhanced US was 69.6% (71/102, 95% confidence interval: 60.7-78.5). The sensitivity of unenhanced MRI for detecting very small HCC was significantly higher than that of unenhanced US (P < 0.001). Regarding the location of HCC in the liver in patients in whom detection by US was unsuccessful, S7-8 was identified in 51.7%.


Currently, unenhanced MRI is a very useful tool for the surveillance of very small HCC in conventional clinical follow-up practice.

Keywords: Comparison of magnetic resonance imaging and ultrasound, Surveillance of very small hepatocellular carcinoma, Magnetic resonance imaging, Ultrasound, Unenhanced magnetic resonance imaging

Core Tip: Recent technological development of magnetic resonance imaging (MRI) scanners has been excellent. The 3.0-tesla (T) MR scanner with a higher field strength has been increasingly used because improved lesion detection can be expected as a result of the increased signal-to-noise ratio, which is theoretically twice with 3.0-T compared with 1.5-T. Another important improvement in MRI is the practical use of diffusion-weighted imaging. In this study, a comparison of unenhanced MRI and ultrasound in detecting very small hepatocellular carcinoma (2 cm in maximum diameter) was made. The sensitivity of unenhanced MRI for detecting very small hepatocellular carcinoma was as high as 95.1% as compared with 69.6% of unenhanced ultrasound (P < 0.001).