Reliable diagnosis of liver focal nodular hyperplasia by a combination of T2 weighted signal and three diffusion magnetic resonance metrics of diffusion-derived 'vessel density', slow diffusion coefficient, and apparent diffusion coefficient: a validation study of two centers' data.

[BACKGROUND] Four -values for diffusion-weighted imaging (DWI) can generate three diffusion metrics, namely, diffusion-derived 'vessel density' (DDVD), slow diffusion coefficient (SDC), and apparent diffusion coefficient (ADC). Based on T2-weighted imaging (T2WI) signal and these three metrics, a semi-quantitative (SQ) score scheme termed 'LiverMss-FNH' has recently been proposed to evaluate liver mass. An earlier study described promising results, with LiverMss ≥4.0 strongly suggesting the diagnosis of focal nodular hyperplasia (FNH). By additional patient data, this study aims to validate these earlier results.

[METHODS] Liver mass DWI patient data were prospectively collected in two hospitals [The Second Hospital of Nanjing and (center 1) and The Fifth Affiliated Hospital of Anhui Medical University (center 2)], totaling 12 cases of FNH and 58 cases of liver malignant tumors [MTs; hepatocellular carcinoma (HCC) n=39, intrahepatic cholangiocarcinoma (ICC) n=10, and metastasis (Met) n=9]. DWI was acquired with free-breathing, long time of repetition (TR), and time of echo (TE) of 82 or 80 ms. DDVD was calculated with =0 and =10 s/mm images, SDC was calculated with =600 and =800 s/mm images or with =400 and =600 s/mm images, and ADC was calculated with =0 and =800 s/mm images or with =0 and =600 s/mm images. For SQ analysis, a liver lesion signal was assigned to five categories: low-signal, iso-signal, slightly high-signal, high-signal, 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 on T2WI was assigned a sub-score '0.5' (otherwise scored 0). The maximum LiverMss favoring the FNH diagnosis was 4.5.

[RESULTS] Seventy-five percent (9/12) of the FNH had LiverMss ≥4.0, and the remaining three FNH all had LiverMss of 3.0. Two of the FNH lesions scored 3.0 had only one signal sign being untypical of FNH, and one FNH lesion scored 3.0 had very heterogenous atypical signals. Two HCC cases with apparent intralesional hemorrhage were excluded from SQ scoring. Six MT cases had LiverMss 'subtraction approach', with four cases scored '-3', one case scored '-2.5', and one case scored '-2.0', respectively; thus, their LiverMss would be at least ≤1.5 (n=4), ≤2.0 (n=1), ≤2.5 (n=1), respectively. Fifty MT cases had LiverMss assessment. Six out of seven MT cases scored ≥2.5 had liver cirrhosis as evident on magnetic resonance imaging (MRI), and another case had embolization treatment. The remaining MT (43/50) all had LiverMss ≤2.0.

[CONCLUSIONS] LiverMss ≥3.0 suggests the possibility of a liver mass being FNH, and LiverMss ≥4.0 can strongly favor the diagnosis of FNH.