Separation of liver focal nodular hyperplasia (FNH) and liver malignant tumors by a combination of T2-weighted imaging signal and three diffusion magnetic resonance metrics of diffusion-derived vessel density, slow diffusion coefficient, and apparent diffusion coefficient

Background: This study investigates the differentiation of liver focal nodular hyperplasia (FNH) from liver malignant tumor (MT) by a combination of T2-weighted imaging (T2WI), diffusion-derived vessel density (DDVD), slow diffusion coefficient (SDC), and apparent diffusion coefficient (ADC). Based on the odds ratio (OR) for a sign to suggest the possibility of a lesion being FNH, we propose a liver mass sum score (LiverMss-FNH) scheme to facilitate the diagnosis. Methods: images. For liver semi-quantitative analysis, relative to the adjacent liver signal, a liver lesion's signal was assigned to five categories: low signal, iso-signal, slightly high signal, high signal, and markedly high signal. The lesion on T2WI being not high signal was assigned a sub-score "1" (otherwise scored 0); the lesion being iso-signal on DDVD was assigned a sub-score "1.5" (otherwise scored 0); the lesion on SDC being not high signal was assigned a sub-score "1" (otherwise scored 0); the lesion on ADC being not low signal was assigned a sub-score "0.5" (otherwise scored 0); the existence of stellate scar was assigned a sub-score "0.5" (otherwise scored 0). The sum of these five sub-scores was termed LiverMss-FNH. Results: A total of 26 MT cases had large (median 8.1 cm, standard deviation: 4.2 cm) and very heterogeneous masses which were very unlikely to be FNH. The remaining 13 FNH cases (median 3.8 cm, standard deviation: 1.7 cm) and 56 MT cases (median 4.9 cm, standard deviation: 4.3 cm; hepatocellular carcinoma, n=40; metastasis, n=12; intrahepatic cholangiocarcinoma, n=4) were evaluated with LiverMss. Liver lass lesion being not high signal on T2WI, being iso-signal on DDVD, being not high signal on SDC, being not low signal on ADC, and the existence of stellate scar had ORs of 49.1, 45.8, 30, 8.5, and 13.3, respectively, favoring the diagnosis of FNH. A total of 69.2% (9/13) of the FNH had LiverMss-FNH ≥4.0, while the remaining 4 cases (30.8%) all had a LiverMss-FNH of 3.0. A total of 89.3% (50/56) of the MT had LiverMss-FNH ≤1.5. Conclusions: Liver FNH tend to have lower DDVD signal and lower SDC signal than liver MT. A LiverMss ≥4 can strongly suggest the diagnosis for a liver mass being FNH, and while a LiverMss-FNH ≤1.5 can strongly suggest the diagnosis for a liver mass being MT.