Abstract
Background: Single breath washout (SBW) can be used to measure Phase III slope (SIII) as a surrogate of ventilation heterogeneity. Nevertheless the impact of factors contributing to SIII is yet to be investigated.
Objectives: To demonstrate the ability to measure regional SIII slopes from dynamic hyperpolarized (HP) magnetic resonance imaging (MRI).
Methods: Single breath washout imaging (SBW-I) was performed using HP 3He MRI. Three healthy subjects followed breathing instructions according to the ERS/ATS consensus statement. During expiration, 2D whole lung projection images were acquired (7.5 frames per second, 7x7mm2 in plane resolution). Flow was recorded simultaneously. Images were then converted to regional gas-concentration maps allowing calculation of SIII in %/L from regional signal decay (Fig1).
Results: The mean phase SIII (±std) was 0.48%/L (±0.08). The concentration decay in the trachea was similar to what is observed from SBW at the mouth (Fig1D). A gravitational slope of SIII from posterior to anterior of 0.03%/cm was found (Fig1E).
Discussion and Conclusion: SBW-imaging may help understanding the concept of regional ventilation heterogeneity in the context of clinical SBW measurements made from the whole lung. In this preliminary study we have qualitatively shown that Phase III slope in the trachea was similar to what is measured at the mouth and well known gravitational dependence of SIII was observed and quantified.
- Copyright ©the authors 2016
