Phase-contrast MRI and CFD modeling of apparent 3He gas flow in rat pulmonary airways

Phase-contrast (PC) magnetic resonance imaging (MRI) with hyperpolarized He-3 is potentially useful for developing and testing patient-specific models of pulmonary airflow. One challenge, however, is that PC-MRI provides apparent values of local He-3 velocity that not only depend on actual airflow but also on gas diffusion. This not only blurs laminar flow patterns in narrow airways but also introduces anomalous airflow structure that reflects gas-wall interactions. Here, both effects are predicted in a live rat using computational fluid dynamics (CFD), and for the first time, simulated patterns of apparent He-3 gas velocity are compared with in vivo PC-MRI. Results show (1) that correlations (R-2) between measured and simulated airflow patterns increase from 0.23 to 0.79 simply by accounting for apparent He-3 transport, and (2) that remaining differences are mainly due to uncertain airway segmentation and partial volume effects stemming from relatively coarse MRI resolution. Higher-fidelity testing of pulmonary airflow predictions should therefore be possible with future imaging improvements. (C) 2012 Elsevier Inc. All rights reserved.