Open Four-Compartment Model in the Measurement of Liver Perfusion1

Rationale and Objectives The goal was to improve informativeness in the determination of liver perfusion with a clinically available iodinated computed tomography (CT) contrast agent by developing open multicompartmental modeling. Materials and Methods Contrast-enhanced functional CT (fCT) examinations were conducted with temporal resolutions of 200–500 msec to 6 New Zealand White rabbits. First, we applied conventional open two-compartment model for the determination of arterial and portal blood flows (F A and F P ), blood and interstitial volume fractions (f b and f i ), and capillary permeability–surface area product (PS) of liver parenchyma. Then, we improved the modeling of vascular physiology by developing three- and open four-compartment models. For comparison, conventional single-compartment model was applied. We determined F A and F P also by using the peak-gradient method. Results Conventional two-compartment model yielded identical fittings with single-compartment model and does not provide unique solutions for f b and f i . The presented open four-compartment model provided F A and F P values of 0.40 ± 0.19 and 1.99 ± 0.57 mL/min/mL (tissue), f b and f i values of 0.30 ± 0.05 and 0.19 ± 0.04 mL/mL (tissue), and PS values of 4.0 ± 1.7 mL/min/mL (tissue). F A and F P are in a good agreement with those derived by using the peak-gradient method. Conclusions With the use of clinical extracellular iodinated CT contrast agent, the presented open four-compartment model provided physiological arterial and portal blood flow values and is also a potential tool in the assessment of blood and interstitial volume fractions and capillary permeability–surface area product. Moreover, the model requires neither measurements from hepatic vein or from other organs nor visual determination of arterial or portal phase.