Examining lung microstructure using ¹⁹F MR diffusion imaging in COPD patients

Abstract

Purpose To examine the time‐dependent diffusion of fluorinated (19F) gas in human lungs for determination of surface‐to‐volume ratio in comparison to results from hyperpolarized 129Xe and lung function testing in healthy volunteers and patients with chronic obstructive pulmonary disease. Methods Diffusion of fluorinated gas in the short‐time regime was measured using multiple gradient‐echo sequences with a single pair of trapezoidal gradient pulses. Pulmonary surface‐to‐volume ratio was calculated using a first‐order approximation of the time‐dependent diffusion in a study with 20 healthy volunteers and 22 patients with chronic obstructive pulmonary disease. The repeatability after 7 days as well as the correlation with hyperpolarized 129Xe diffusion MRI and lung function testing was analyzed. Results Using 19F diffusion MRI, the median surface‐to‐volume ratio is significantly decreased in chronic obstructive pulmonary disease patients (S/V = 126 cm−1 [87–144 cm−1]) compared with healthy volunteers (S/V = 164 cm−1 [160–84 cm−1], p < 0.0001). No significant difference was found between measurements within 7 days for healthy (p = 0.88, median coefficient of variation = 4.3%) and diseased subjects (p = 0.58, median coefficient of variation= 6.7%). Linear correlations were found with S/V from 129Xe diffusion MRI (r = 0.85, p = 0.001) and the forced expiratory volume in 1 second (r = 0.68, p < 0.0001). Conclusion Examination of lung microstructure using time‐dependent diffusion measurement of inhaled 19F is feasible, repeatable, and correlates with established measurements.

High-Sensitivity, Low-Field 19F-MRI Approach Using High Manganese Ferrite Concentrations

“…For each spoke, RF excitation is employed with a hard pulse (duration = T RF ). Under a constant gradient, the RF switch transforms from the transmit mode to the receive mode for sampling . The sum of one-half the time used for RF transmit and the dead time generated by the transmit/receive mode switch plus the time of filter delay after analogue to digital conversion turns on is termed as delta­(Δ).…”

“…Not only the high-performance fluorine agents but also the optimized MRI methods can contribute to the 19 F-MRI application on the human diagnosis . Although the conventional systems at 1.5 T and 3 T have resulted in considerable improvements in data quality and diagnostic value, they remain relatively expensive and out of the financial reach for much of the world.…”

“…16 Not only the high-performance fluorine agents but also the optimized MRI methods can contribute to the 19 F-MRI application on the human diagnosis. 17 Although the conventional systems at 1.5 T and 3 T have resulted in considerable improvements in data quality and diagnostic value, they remain relatively expensive and out of the financial reach for much of the world. On the contrary, the low-field MRI systems have benefited from a relatively low cost, a subject comfort, and a safety perspective in terms of decreased projectile risks, implant compliance, and the possibility to image closer to implants due to more minor magnetic susceptibility artifacts.…”

Feasibility of free‐breathing 19F MRI image acquisition to characterize ventilation defects in CF and healthy volunteers at wash‐in

“…19 F pulmonary MRI with fluorinated gases has been used to characterize ventilation abnormalities such as unventilated areas (ventilation defect percentages [VDPs]) and poorly ventilated regions (fractional lung volume with prolonged gas washout time in both cystic fibrosis [CF] and chronic obstructive pulmonary disease). [1][2][3][4][5][6] The 19 F gases, including C 3 F 8 and SF 6 , can be mixed with oxygen (O 2 ) to create normoxic gas mixtures. 19 F MRI has the potential to spatially measure lung function 3 at multislice acquisitions encapsulating the full 3D lung cavity without the need for ionizing radiation.…”

Volume‐Controlled 19F MR Ventilation Imaging of Fluorinated Gas

“…Over recent years, sulfur hexafluoride (SF 6 ), tetrafluoromethane (CF 4 ), hexafluoroethane (C 2 F 6 ), perfluoropropane (C 3 F 8 ), and octafluorocyclobutane (C 4 F 8 ) have been used to investigate static ventilation 3,4 and diffusion, 5 gas wash‐in and wash‐out dynamics, 6–9 fractional ventilation, 10 ventilation/perfusion ratios, 11,12 as well as surface/volume ratios 13 in animal models, healthy volunteers, and patients with various lung diseases.…”