Free‐Breathing Functional Pulmonary Proton MRI: A Novel Approach Using Voxel‐Wise Lung Ventilation (VOLVE) Assessment in Healthy Volunteers and Patients With Chronic Obstructive Pulmonary Disease

Abstract

BackgroundIn respiratory medicine, there is a need for sensitive measures of regional lung function that can be performed using standard imaging technology, without the need for inhaled or intravenous contrast agents.PurposeTo describe VOxel‐wise Lung VEntilation (VOLVE), a new method for quantifying regional lung ventilation (V) and perfusion (Q) using free‐breathing proton MRI, and to evaluate VOLVE in healthy never‐smokers, healthy people with smoking history, and people with chronic obstructive pulmonary disease (COPD).Study TypeProspective pilot.PopulationTwelve healthy never‐smoker participants (age 30.3 ± 12.5 years, five male), four healthy participants with smoking history (>10 pack‐years) (age 42.5 ± 18.3 years, one male), and 12 participants with COPD (age 62.8 ± 11.1 years, seven male).Field Strength/SequenceSingle‐slice free‐breathing two‐dimensional fast field echo sequence at 3 T.AssessmentA novel postprocessing was developed to evaluate the MR signal changes in the lung parenchyma using a linear regression‐based approach, which makes use of all the data in the time series for maximum sensitivity. V/Q‐weighted maps were produced by computing the cross‐correlation, lag and gradient between the respiratory/cardiac phase time course and lung parenchyma signal time courses. A comparison of histogram median and skewness values and spirometry was performed.Statistical TestsKruskal–Wallis tests with Dunn's multiple comparison tests to compare VOLVE metrics between groups; Spearman correlation to assess the correlation between MRI and spirometry‐derived parameters; and Bland–Altman analysis and coefficient of variation to evaluate repeatability were used. A P‐value <0.05 was considered significant.ResultsSignificant differences between the groups were found for ventilation between healthy never‐smoker and COPD groups (median XCCV, LagV, and GradV) and perfusion (median XCCQ, LagQ, and GradQ). Minimal bias and no significant differences between intravisit scans were found (P range = 0.12–0.97).Data ConclusionThis preliminary study showed that VOLVE has potential to provide metrics of function quantification.Level of Evidence2Technical EfficacyStage 1