Open four-compartment model in the measurement of liver perfusion

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.