​IS STANDARD SPIROMETRY IN PULMONOLOGY ABOUT TO BE SUPERSEDED ?

Ventilation is a complex function exhibiting significant intra- and inter-individual variability, with a highly inhomogeneous distribution throughout the lung volume. Standard spirometry is the reference examination for assessing ventilatory function, based on global flow–volume curves measured at the mouth during forced breathing. Although simple, this technique is limited by the need for patient cooperation, making it unsuitable for very young children or patients with neurological disorders, and by its low sensitivity to regional lung abnormalities. Because breathing is intrinsically a three-dimensional phenomenon and lung diseases are often regional, ventilation would benefit from being assessed locally within the lung volume.
Despite the inherent challenges of lung MRI (low water content and thus few hydrogen nuclei, as well as physiological motion), recent advances have revealed the potential of functional lung MRI using standard acquisitions that are readily translatable to clinical practice. Over the past fifteen years, studies based on the assumption of linearity between MRI signal intensity and lung tissue density have assessed ventilation from signal variations throughout the respiratory cycle.

THE POTENTIAL OF 3D SPIROMETRY USING MAGNETIC RESONANCE

In this prospective and innovative study, the researchers developed a new technique based not on MR signal intensity, but on lung deformation during respiratory motion : 3D magnetic resonance spirometry. Ten-minute ultra-short echo time (UTE) acquisitions were performed in 25 healthy volunteers breathing freely, both in the supine and prone positions. Despite spatially heterogeneous respiratory parameters among participants, common respiratory patterns emerged across all subjects, with features primarily governed by the lung's dependence on gravity. The 3D maps of spirometric parameters were repeatable and reproducible, despite physiological variability related to each volunteer's individual breathing pattern.

TOWARD A NEW REFERENCE TOOL FOR RESPIRATORY DISEASE ASSESSMENT

With excellent overall repeatability and residual variability intrinsic to respiration, this proof of concept, supported by the european V|LF-Spiro3D program and the FLI infrastructure, establishes 3D magnetic resonance spirometry as a highly informative new imaging modality. It is expected to facilitate regional physiopathological monitoring of respiratory diseases.

Joliot contact : Xavier Maitre (xavier.maitre@universite-paris-saclay.fr)
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