Division of abdominal imaging, Department of Radiology, Taipei Veterans General Hospital, Taipei, Taiwan.
Division of Gastroenterology and Hepatology, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan.
DATE : 2022
75 years old, Male, 88kg
Disease(s): non-hypervascular hypointense hepatocellular nodules
This 75-year-old gentleman has chronic hepatitis B and has regular imaging follow-up. His MR imaging showed cirrhotic liver with marked fibrosis and diffuse nodular regeneration. Given that heterogenous signal intensity of multiple regeneration nodules on T1-weighted image (T1WI) would hinder the detection of small hepatocellular carcinoma (HCC), EOB-MRI was chosen as the primary follow-up imaging modality.
Gadoxetate disodium(Gd-EOB-DTPA) injection 0.1 mL/kg
During regular follow-up by the EOB-MRI imaging, a 7mm nodule was identified at segment 8 of liver. This nodule showed hypovascularity in the arterial phase and hypointensity in the hepatobiliary phase, which was indicated as a ‘‘high-risk nodule’’ or “non-hypervascular hypointense nodule (NHHN)” (Figure 1). Eight months later, this nodule grew to 1cm in diameter, and developed hypervascularization displaying a “wash-in and wash-out” typical enhancement pattern of HCC (Figure 2). Therefore, the patient underwent radiofrequency ablation (RFA) for this tumor. Complete ablation was confirmed by the follow-up MR examination (Figure 3).
MRI showed cirrhosis and hepatic fibrosis with diffuse regenerative nodules in the liver (A). No any enhancing nodule was detected in the arterial phase (B). Portal phase images showed a 7mm hypointense nodule at segment 8 of the liver (C). This nodule displayed hypointensity in 20 minutes hepatobiliary phase (HBP) images (E) but did not show high signal intensity in T2-weighted images (T2WI) (D) or restricted diffusion (F).
The follow-up MR images were obtained eight months after initial examination. The pre-contrast phase MR image showed a 1 cm nodule with hypointensity (A). Hypervascularization of this nodule was noted from the arterial phase image (B), and washout pattern was displayed by the delayed-phase image (C), confirming the diagnosis of HCC. This nodule showed high signal intensity on T2-weighted MR images (D), hypointensity on the HBP (E), and restricted diffusion on the diffusion-weighted image (DWI) (F).
After RFA, all followed-up images confirmed complete coverage of the target tumor without viable tumor.
The development of hepatocellular carcinoma (HCC) is a multistep process from preneoplastic lesions, including regenerative nodule (RN) and dysplastic nodule (DN), to malignant tumor. Unlike overt HCC which shows hypervascularity on the arterial phase images, RN and DN may appear hypointense, isointense, hyperintense, or mixed signal intensity on T1WI compared to the background liver, but not hypervascularity1. In high-risk patients, these hypovascular nodules may show hypointensity on the HBP of EOB-MRI, which was known as non-hypervascular hypointense nodules (NHHNs)2. These nodules could have malignant potential and are considered to be clinical precursors of HCCs3.
A meta-analysis revealed the pooled overall rate of hypervascular transformation of a NHHN was 28.2%, with 1-, 2-, and 3-year cumulative incidence rates of 18.3%, 25.2%, and 30.3%, respectively4. High SI on T2WI and restricted diffusion were known as independent predictors of transformation into hypervascular HCCs, with a median time of 8.0 months versus 62.0 months for the nodules without imaging perdictors5. Moreover, the nodular size larger than 1cm in diameter6, male gender, and hepatitis B/C virus co-infection7 also increased the risk of developing hypervascularization. The existence of NHHN has significant impact on the prognosis of patients. Previous studies demonstrated higher post-treatment recurrence rates after surgical resection (hazard ratio: 1.94)8 or radiofrequency ablation (hazard ratio: 2.84)6 in patients with NHHNs. In this case, the NHHN transformed into a typical hypervascular HCC after eight months. The patient underwent thermal ablation and achieved a complete response.
In conclusion, EOB-MRI is helpful in detecting the presence of non-hypervascular hypointense hepatocellular nodules on HBP, which tend to show hypervascular and malignant transformation during follow-up. Closely imaging follow-up to identify the HCCs is warranted for appropriate management.
|MR device used||Signa HDxt 1.5T(GE Healthcare)|
|Contrast enhancement condition||Dose(mL)||Infusion rate (mL/sec)|
|Physiological saline chaser||30ml||1mL/sec|
|Imaging type||Imaging sequence||Imaging duration||TE
(Number of additions)
(Number of steps)
(Number of matrices)
|Number of slices|
(in & out of phase)
|With a contrast agent|