A hybrid multibreath wash-in wash-out lung function quantification scheme in human subjects using hyperpolarized³He MRI for simultaneous assessment of specific ventilation, alveolar oxygen tension, oxygen uptake, and air trapping

Abstract

Purpose To present a method for simultaneous acquisition of alveolar oxygen tension (PAO2), specific ventilation (SV), and apparent diffusion coefficient (ADC) of hyperpolarized (HP) gas in the human lung, allowing reinterpretation of the PAO2 and SV maps to produce a map of oxygen uptake (R). Method An imaging scheme was designed with a series of identical normoxic HP gas wash-in breaths to measure ADC, SV, PAO2 and R in less than 2 minutes. Signal dynamics was fit to an iterative recursive model that regionally solves for these parameters. This measurement was successfully performed in twelve subjects classified in three healthy, smoker and COPD cohorts. Results The overall whole-lung ADC, SV, PAO2 and R were (0.20 ± 0.03cm2/s, 0.39 ± 0.06,113 ± 2Torr and 1.55 ± 0.35Torr/s) and (0.21 ± 0.03 cm2/s, 0.33 ± 0.06, 115.9 ± 4 Torr and 0.97 ± 0.2 Torr/s) and (0.25 ± 0.06cm2/s, 0.23 ± 0.08, 114.8 ± 6.0Torr and 0.94 ± 0.12Torr/s) in healthy, smoker and COPD subjects, respectively. Maps of SV, PAO2 or R are indicators of both smoking-related changes and disease, and the severity of the disease correlated to the degree of this heterogeneity. Subjects with symptoms showed reduced oxygen uptake and specific ventilation. Conclusion High-resolution, nearly coregistered and quantitative measures of lung function and structure were obtained with less than 1 liter of HP. This promising hybrid multi-breath technique produced measures of lung function which revealed clear differences among the cohorts and subjects, and which were confirmed by correlations with global lung measurements.

Free-breathing Dynamic 19F Gas MR Imaging for Mapping of Regional Lung Ventilation in Patients with COPD

“…Statistically significant correlations were observed for all evaluated lung function test parameters compared with median and interquartile range of 19 F washout parameters. An inverse linear correlation of median number of breaths (r = 20.82; P , .0001) and median washout times (r = 20.77; P , .0001) with percentage predicted of forced expiratory volume in 1 second (FEV 1 ) was observed; correspondingly median FV (r = 0.86; P , .0001) correlated positively with percentage predicted FEV 1 .…”

“…Quantification of regional lung ventilation by using dynamic 19 F gas washout MR imaging in free breathing is feasible at 1.5 T even in obstructed lung segments. F gas mixture can be continuously inhaled over several minutes without any notable adverse effects (22)(23)(24).…”

“…F gas mixture can be continuously inhaled over several minutes without any notable adverse effects (22)(23)(24). Inhaling a mixture of the 19 F tracer gas and oxygen over several minutes may provide quantitative regional information of lung ventilation even in regions of slow gas wash-in or washout kinetics (25)(26)(27)(28)(29). However, the major challenge of lung MR imaging by using fluorinated gas tracers is the relatively low SNR compared with that of hyperpolarized 129 Xe gas MR imaging (30).…”

“…The purpose of this work was to quantify regional lung ventilation in patients with COPD by using free-breathing dynamic 19 F gas MR imaging.…”

“…In this institutional review board-approved prospective study, 27 patients with COPD were examined by using breath-hold 19 F gas wash-in MR imaging during inhalation of a normoxic fluorinated gas mixture (perfluoropropane) and by using free-breathing dynamic 19 F gas washout MR imaging after inhalation of the gas mixture was finished for a total of 25-30 L. Regional lung ventilation was quantified by using volume defect percentage (VDP), washout time, number of breaths, and fractional ventilation (FV).…”