Preoperative assessment of microvascular invasion of hepatocellular carcinoma using non-Gaussian diffusion-weighted imaging with a fractional order calculus model: A pilot study

Purpose: To assess the clinical potential of a set of new diffusion parameters (D, beta, and mu) derived from fractional order calculus (FROC) diffusion model in predicting microvascular invasion (MVI) of hepatocellular carcinoma (HCC).Materials and methods: Between January 2019 to November 2020, a total of 63 patients with HCC were enrolled in this study. Diffusion-weighted images were acquired by using ten b-values (0-2000 s/mm2). The FROC model parameters including diffusion coefficient (D), fractional order parameter (beta), a microstructural quantity (mu) together with a conventional apparent diffusion coefficient (ADC) were calculated. Intraclass coefficients were calculated for assessing the agreement of parameters quantified by two radiologists. The differences of these values between the MVI-positive and MVI-negative HCC groups were compared by using independent sample t -test or the Mann-Whitney U test. Then the parameters showing significant differences between subgroups, including the beta and D, were integrated to develop a comprehensive predictive model via binary logistic regression. The diagnostic performance was evaluated by receiver operating characteristic (ROC) analysis.Results: Among all the studied diffusion parameters, significant differences were found in D,beta, and ADC between the MVI-positive and MVI-negative groups. MVI-positive HCCs showed significantly higher beta values (0.65 +/- 0.17 vs. 0.51 +/- 0.13, P = 0.001), along with lower D values (0.84 +/- 0.11 mu m2/ms vs. 1.03 +/- 0.13 mu m2/ms, P < 0.001) and lower ADC values (1.38 +/- 0.46 mu m2/ms vs. 2.09 +/- 0.70 mu m2/ms, P < 0.001) than those of MVI-negative HCCs. According to the ROC analysis, the combination of D and beta demonstrated the largest area under the ROC curve (0.920) compared with individual parameters (D: 0.912; beta: 0.733; and ADC: 0.831) for differentiating MVI-positive from MVI-negative HCCs.Conclusions: The FROC parameters can be used as noninvasive quantitative imaging markers for preoperatively predicting the MVI status of HCCs.