An efficient method for calculating kinetic parameters in a dual-input single-compartment model

Abstract

Quantitative measurement of hepatic perfusion has the potential to provide important information in the assessment and management of various liver diseases. The utility of hepatic perfusion characterization relies on the resolution of each component of its dual blood supply, i.e. the hepatic artery and portal vein. In this study, a linear equation was derived by integrating the differential equation describing the kinetic behaviour of contrast agent (CA) in a dual-input single-compartment model, from which the kinetic parameters can be easily obtained using the linear least-squares method. The usefulness of this method was investigated using computer simulations, in comparison with the non-linear least-squares (NLSQ) method. This method calculated the kinetic parameters faster than the NLSQ method by a factor of approximately 10, with almost the same accuracy as the NLSQ method. This method will be useful for analysing the kinetic behaviour of CA in the unique liver environment, especially by generating the functional images of kinetic parameters.

Usefulness of a dual-input single-compartment model for quantitative evaluation of thioacetamide-induced acute liver injury in rats using dynamic contrast-enhanced computed tomography

“…First, we analyzed the kinetic behavior of the contrast agent in the liver by using the dual-input single-compartment model [9], which is illustrated in Fig. 1.…”

“…We obtained C L (t) by drawing an ROI on the liver, avoiding the large blood vessels in the liver. The symbols s a and s p represent the transit times of the contrast agent from the aorta and portal-vein ROIs to the liver ROI, respectively [8,9]. In this study, these transit times were determined visually from the first non-zero values of the time-density curves.…”

“…K 1a , K 1p , and k 2 denote the rate constants for the transfer of the contrast agent from the hepatic artery to the liver, from the portal vein to the liver, and from the liver to the blood, respectively. We expressed K 1a and K 1p in ml/100 ml/min and k 2 in min -1 [8,9]. Because iodinated contrast agent does not enter red blood cells and the hematocrit in small vessels is significantly different from that in the systemic hematocrit [7], we introduced a correction factor (k H ) in Eq.…”

“…1 to correct for the difference between the hematocrit in large vessels used for the determination of C a (t) and C p (t) (H LV , approximately 0.45) and in small vessels (H SV , approximately 0.25), which is given by k H ¼ ð1 À H SV Þ=ð1 À H LV Þ [16]. The K 1a , K 1p , and k 2 values were calculated from DCE-CT data by use of the linear least-squares method [9].…”

“…Previously, we developed an efficient method for quantifying the AHBF and PHBF separately from DCE-CT data, by using a dual-input singlecompartment model and the linear least-squares method [9], and investigated its usefulness by means of computer simulations in comparison with the nonlinear least-squares method [8][9][10].…”