Abstract
Pharmacokinetic parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) have been increasingly used to evaluate the permeability of tumor vessel. Histogram metrics are a recognized promising method of quantitative MR imaging that has been recently introduced in analysis of DCE-MRI pharmacokinetic parameters in oncology due to tumor heterogeneity. In this study, 21 patients with renal cell carcinoma (RCC) underwent paired DCE-MRI studies on a 3.0 T MR system. Extended Tofts model and population-based arterial input function were used to calculate kinetic parameters of RCC tumors. Mean value and histogram metrics (Mode, Skewness and Kurtosis) of each pharmacokinetic parameter were generated automatically using ImageJ software. Intra- and inter-observer reproducibility and scan–rescan reproducibility were evaluated using intra-class correlation coefficients (ICCs) and coefficient of variation (CoV). Our results demonstrated that the histogram method (Mode, Skewness and Kurtosis) was not superior to the conventional Mean value method in reproducibility evaluation on DCE-MRI pharmacokinetic parameters (K trans & Ve) in renal cell carcinoma, especially for Skewness and Kurtosis which showed lower intra-, inter-observer and scan-rescan reproducibility than Mean value. Our findings suggest that additional studies are necessary before wide incorporation of histogram metrics in quantitative analysis of DCE-MRI pharmacokinetic parameters.
Highlights
Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), as a very common MRI technique, can subjectively judge the enhancement of a target area on a visual basis, semi-quantitatively characterize tumors using curvology[1,2], and can quantitatively evaluate parameters generated using pharmacokinetic models[3,4] which reflected the dynamic distribution of Ga-related contrast agent in the different compartments of the tissue
We found that scan-rescan performance had a relatively poorer reproducibility than intra- and inter-observer analysis regarding to histogram metrics of dynamic contrast-enhanced MRI (DCE-MRI) pharmacokinetic parameters (K trans & Ve) in renal cell carcinoma (RCC)
As for agreement analysis, scan-rescan intra-class correlation coefficients (ICCs) of all histogram parameters were lower than intra- and inter-observer ICCs and intra-observer performance showed the highest ICCs
Summary
Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), as a very common MRI technique, can subjectively judge the enhancement of a target area on a visual basis, semi-quantitatively characterize tumors using curvology[1,2], and can quantitatively evaluate parameters generated using pharmacokinetic models[3,4] which reflected the dynamic distribution of Ga-related contrast agent in the different compartments of the tissue. The two-compartment model of DCE-MRI assumes the contrast agent exchanges between the plasma space and the extravascular-extracellular space (EES)[5], and the forward and backward transfer rate could reflect the permeability of the microvasculature It is used extensively in measuring tumor angiogenesis and blood brain barrier (BBB) disruption. There is increasing interest in analyzing lesion heterogeneity by way of histogram analysis to characterize tumor subtypes[12,13,14,15], tumor histological grades[16,17,18,19], tumor aggressiveness[20] and evaluate treatment effects[21,22,23,24] This methodology has showed its utility in investigating the distributions of various tumor parameters such as permeability in dynamic contrast-enhanced MRI (DCE-MRI)[17,25]
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