Dual-input two-compartment pharmacokinetic model of dynamic contrast-enhanced magnetic resonance imaging in hepatocellular carcinoma

AIM: To investigate the feasibility of a dual-input two-compartment tracer kinetic model for evaluating tumorous microvascular properties in advanced hepatocellular carcinoma（HCC）. METHODS: From January 2014 to April 2015, we prospectively measured and analyzed pharmacokinetic parameters [transfer constant(Ktrans), plasma flow（Fp）, permeability surface area product（PS）, efflux rate constant(kep), extravascular extracellular space volume ratio（Ve）, blood plasma volume ratio（Vp）, and hepatic perfusion index（HPI）] using dual-input two-compartment tracer kinetic models [a dual-input extended Tofts model and a dual-input 2-compartment exchange model（2CXM）] in 28 consecutive HCC patients. A well-known consensus that HCC is a hypervascular tumor supplied by the hepatic artery and the portal vein was used as a reference standard. A paired Student’s t-test and a nonparametric paired Wilcoxon rank sum test were used to compare the equivalent pharmacokinetic parameters derived from the two models, and Pearson correlation analysis was also applied to observe the correlations among all equivalent parameters. The tumor size and pharmacokinetic parameters were tested by Pearson correlation analysis, while correlations among stage, tumor size and all pharmacokinetic parameters were assessed by Spearman correlation analysis. RESULTS: The Fp value was greater than the PS value（FP = 1.07 m L/m L per minute, PS = 0.19 m L/m L per minute） in the dual-input 2CXM; HPI was 0.66 and 0.63 in the dual-input extended Tofts model and the dualinput 2CXM, respectively. There were no significant differences in the Kep, Vp, or HPI between the dual-input extended Tofts model and the dual-input 2CXM（P = 0.524, 0.569, and 0.622, respectively）. All equivalent pharmacokinetic parameters, except for Ve, were correlated in the two dual-input two-compartment pharmacokinetic models; both Fp and PS in the dualinput 2CXM were correlated with Ktrans derived from the dual-input extended Tofts model（P = 0.002, r = 0.566; P = 0.002, r = 0.570）; Kep, Vp, and HPI between the two kinetic models were positively correlated（P = 0.001, r = 0.594; P = 0.0001, r = 0.686; P = 0.04, r = 0.391, respectively）. In the dual input extended Tofts model, Ve was significantly less than that in the dual input 2CXM（P = 0.004）, and no significant correlation was seen between the two tracer kinetic models（P = 0.156, r = 0.276）. Neither tumor size nor tumor stage was significantly correlated with any of the pharmacokinetic par