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
Research background

Nowadays advancement of magnetic resonance imaging (MRI) has markedly improved the quality of liver imaging. We believe that a high-speed scan and diffusion-weighted imaging are two major factors that have contributed to the improved detection of hepatocellular carcinomas (HCCs). In early MRI, a respiration artifact was the most troublesome factor deteriorating the quality of images of the liver. A high-speed scan brought by the conversion from 1.5-tesla (T) to 3.0-T facilitates whole-liver MRI while patients hold their breath. Breath-holding scans reduce motion and misregistration artifacts, and create high-quality liver images. In addition, the practical use of diffusion-weighted imaging has contributed to the detection of cell-rich lesions. Tumors are proper objects of these sequences. There is a report (or several reports) that the sensitivity of detecting pancreatic cancer rose with the use of diffusion-weighted imaging. We believe that the same can be applied to detect HCC. Currently, dynamic MRI with contrast media is considered the standard procedure to diagnose HCC. However, with improved images, non-contrasted liver MRI is still a useful modality to detect HCCs.

Research motivation

Previous reports in 2001-2003 stated that the sensitivity of unenhanced MRI to detect very small HCC (≤ 2 cm in diameter) was about 60%. Since then, there have been few reports on the sensitivity to detect very small HCC, especially in recent years.

Research objectives

Surveillance of HCC in liver diseases, especially in liver cirrhosis, has been conducted by ultrasound (US) or MRI throughout the world. Although US was performed more popularly than MRI in the surveillance of HCC, the superiority of MRI over US has been demonstrated in many studies since 2001-2003. Although enhanced MRI is now performed for the accurate diagnosis of HCC, in conventional clinical practice for HCC surveillance in liver diseases, unenhanced MRI is widely performed throughout the world. On the other hand, MRI has made marked improvements in recent years. In this study, a comparison of unenhanced MRI and US in detecting very small HCC was made. In order to conduct precise evaluation, we selected patients in whom MRI and US were performed at about the same time (on the same day whenever possible or at least within 14 d of one another).

Research methods

Out of the 403 patients with very small HCC nodules (≤ 2 cm in maximal diameter), 102 who underwent unenhanced MRI and US at nearly the same time (on the same day whenever possible or at least within 14 d of one another) at the first diagnosis of HCC were selected. The detection rate of HCC by unenhanced MRI was studied in comparison with unenhanced US.

Research results

We found that the sensitivity of unenhanced MRI for detecting very small HCC was as high as 95.1%, as compared with 69.6% by unenhanced US (P < 0.001).

Research conclusions

Currently, unenhanced MRI is a very important imaging modality for picking up very small HCC in usual clinical practice.

Research perspectives

As in this study, the marked superiority of unenhanced MRI to detect very small HCC as compared with unenhanced US was confirmed, and it may be desirable to perform routine surveillance of HCC in liver diseases by unenhanced MRI.