title: Measurement of the distribution of ventilation-perfusion ratios in the human lung with proton MRI: comparison with the multiple inert-gas elimination technique.
abstract: We have developed a novel functional proton magnetic resonance imaging (MRI) technique to measure regional ventilation-perfusion (V̇A/Q̇) ratio in the lung. We conducted a comparison study of this technique in healthy subjects (n= 7, age = 42 ± 16 yr, Forced expiratory volume in 1 s = 94% predicted), by comparing data measured using MRI to that obtained from the multiple inert gas elimination technique (MIGET). Regional ventilation measured in a sagittal lung slice using Specific Ventilation Imaging was combined with proton density measured using a fast gradient-echo sequence to calculate regional alveolar ventilation, registered with perfusion images acquired using arterial spin labeling, and divided on a voxel-by-voxel basis to obtain regional V̇A/Q̇ ratio. LogSDV̇ and LogSDQ̇, measures of heterogeneity derived from the standard deviation (log scale) of the ventilation and perfusion vs. V̇A/Q̇ ratio histograms respectively, were calculated. On a separate day, subjects underwent study with MIGET and LogSDV̇ and LogSDQ̇ were calculated from MIGET data using the 50-compartment model. MIGET LogSDV̇ and LogSDQ̇ were normal in all subjects. LogSDQ̇ was highly correlated between MRI and MIGET (R = 0.89,P= 0.007); the intercept was not significantly different from zero (-0.062,P= 0.65) and the slope did not significantly differ from identity (1.29,P= 0.34). MIGET and MRI measures of LogSDV̇ were well correlated (R = 0.83,P= 0.02); the intercept differed from zero (0.20,P= 0.04) and the slope deviated from the line of identity (0.52,P= 0.01). We conclude that in normal subjects, there is a reasonable agreement between MIGET measures of heterogeneity and those from proton MRI measured in a single slice of lung.NEW & NOTEWORTHYWe report a comparison of a new proton MRI technique to measure regional V̇A/Q̇ ratio against the multiple inert gas elimination technique (MIGET). The study reports good relationships between measures of heterogeneity derived from MIGET and those derived from MRI. Although currently limited to a single slice acquisition, these data suggest that single sagittal slice measures of V̇A/Q̇ ratio provide an adequate means to assess heterogeneity in the normal lung.
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla, California.|The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California.
authors.forename: Rui Carlos
authors.identifier: http://orcid.org/0000-0002-8885-8671
authors.initials: RC
authors.lastname: Sá
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla, California.|The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California.
authors.forename: A Cortney
authors.initials: AC
authors.lastname: Henderson
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla, California.
authors.forename: Tatum
authors.initials: T
authors.lastname: Simonson
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla, California.|The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California.
authors.forename: Tatsuya J
authors.initials: TJ
authors.lastname: Arai
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla, California.
authors.forename: Harrieth
authors.initials: H
authors.lastname: Wagner
authors.affiliation: Department of Radiology, University of California, San Diego, La Jolla, California; and.|The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Theilmann
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla, California.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Wagner
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla, California.|Department of Radiology, University of California, San Diego, La Jolla, California; and.|The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California.
authors.forename: G Kim
authors.initials: GK
authors.lastname: Prisk
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla, California; shopkins@ucsd.edu.|Department of Radiology, University of California, San Diego, La Jolla, California; and.|The Pulmonary Imaging Laboratory, University of California, San Diego, La Jolla, California.
authors.forename: Susan R
authors.initials: SR
authors.lastname: Hopkins
mesh_terms: D000328:Adult; D001784:Blood Gas Analysis / Q000379:methods; D002849:Chromatography, Gas / Q000379:methods; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D005741:Noble Gases / Q000008:administration & dosage / Q000097:blood*; D011522:Protons; D012129:Respiratory Function Tests / Q000379:methods; D014692:Ventilation-Perfusion Ratio / Q000502:physiology*
chemical_list: D005741:Noble Gases; D011522:Protons
keywords: arterial spin labeling; magnetic resonance imaging; multiple inert gas elimination technique; specific ventilation imaging; ventilation-perfusion ratio