Imaging Analysis

Two pediatric radiologists (with 18 and 7 y of experience in pediatric imaging, respectively) performed US examinations independently. Two radiologists analyzed the US imaging data retrospectively, and the analysis was conducted under consensus. The reviewers were blinded to clinical data. In grayscale images, the location, size (defined as the maximum transverse diameter), echogenicity of the lesion, and background liver parenchymal echogenicity were analyzed. On both CDI and SMI, internal vascularity was assessed, and the Doppler features were classified into the following 3 patterns: typical spoke-wheel pattern, multifocal spoke-wheel pattern, and nonspecific pattern. When radiating arteries branching from a single central vessel are directly visualized, it is defined as a typical spoke-wheel pattern. When multifocal radiating arteries branch from vessels, it is defined as a multifocal spoke-wheel pattern (Fig. ​(Fig.1).1). It is classified as nonspecific when it cannot be divided into any pattern. To evaluate any difference in the Doppler pattern of FNH in relation to lesion size, we divided the lesions into small FNH with ≤3 cm diameter and the large FNH with >3 cm in diameter.

The diagram of intralesional vascular pattern. A, Typical spoke-wheel pattern; radiating arteries branching from a single central vessel. B, Multifocal spoke-wheel pattern; multifocal radiating arteries branching from vessels. C, Nonspecific pattern; vessels cannot be divided into any pattern.

Two pediatric radiologists analyzed contrast-enhanced MRI images with/without a hepatocyte-specific agent for confirmatory diagnosis of FNH. Definitive diagnosis of FNH was based on the presence of 6 main MRI signs: (1) iso or slight hypointensity relative to the liver on T1-weighted images plus iso or slight hyperintensity on T2-weighted images, (2) intense and homogeneous signal enhancement during the arterial phase, (3) iso or slight hyperintensity during the portal venous and delayed phases, (4) lobulated outlines and a central scar characterized by T2 hyperintensity, (5) T1 hypointensity, and (6) hyperintensity on hepatobiliary phase.^25–29