Comparison of Airway Diameter Measurements from an Anthropomorphic Airway Tree Phantom Using Hyperpolarized 3He MRI and High-Resolution Computed Tomography

摘要

An anthropomorphic airway tree phantom was imaged with both hyperpolarized (HP) ³He MRI using a dynamic projection scan and computed tomography (CT). Airway diameter measurements from the HP ³He MR images obtained using a newly developed model-based algorithm were compared against their corresponding CT values quantified with a well-established method. Of the 45 airway segments that could be evaluated with CT, only 14 airway segments (31%) could be evaluated using HP ³He MRI. No airway segments smaller than ~4 mm in diameter and distal to the fourth generation were adequate for analysis in MRI. For the 14 airway segments measured, only two airway segments yielded a non-equivalent comparison between the two imaging modalities, while eight more had inconclusive comparison results, leaving only four airway segments (29%) that satisfied the designed equivalence criteria. Some of the potential problems in airway diameter quantification described in the formulation of the model-based algorithm were observed in this study. These results suggest that dynamic projection HP ³He MRI may have limited utility for measuring airway segment diameters, particularly those of the central airways.