Comparison of CT-based lobar ventilation models with ³He MRI ventilation measurements in asthmatics

Abstract

Introduction CT models of ventilation can be computed from expiratory and inspiratory scans by means of the relative lobar expansion. This model has been validated against SPECT [1].

Objective To compare models of lobar ventilation from CT with ³He MRI using multi-modal image registration in a population of asthma patients.

Methods 29 patients with moderate-to-severe asthma underwent breath-hold CT at TLC and FRC. CT was used to segment the lobes at FRC and TLC by identification of major fissures and these were used to calculate percentage lobar ventilation [1]. ¹H and ³He MRI were acquired in the same breath at FRC+1L [2], and the ¹H MRI to CT registration was applied directly to ³He MRI allowing direct comparison of lobar CT ventilation with ³He.

Results ³He MRI was successfully warped to inspiration CT using the transform from the ¹H MRI and CT registration. The mean absolute difference between CT and ³He MRI ventilation across lobes was 4.8% (mean±SD for each lobe: RUL+RML=6.1±4.6%; RLL=5.0±5.7%; LUL=4.0±4.1%; LLL=4.6±3.7%).

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Conclusion This study compares percentage lobar ventilation from CT models with a direct measure of gas ventilation using ³He MRI. In so doing we validate the CT ventilation model and demonstrate that multi-modal registration allows the regional interpretation of ³He MR images on top of the underlying anatomy of the CT.

References [1]Radiol 2010;257:854-62 [2]NMR Biomed 2011;24:130-34.