Imaging lungs using inert fluorinated gases

TLDR

The study used 19F projection MRI of hexafluoroethane/20 % O₂ inhaled gas, acquiring free induction decays in 686 gradient directions with a 5 ms repetition time and a 2 ms acquisition window, and applied singular‑value decomposition to reconstruct projections despite RF pulse gaps. The resulting 3‑D images achieved 700 µm resolution after 4.3 h of acquisition, demonstrating that inert fluorinated gas imaging is a cost‑effective alternative to polarized noble gases for steady‑state lung imaging.

Abstract

Abstract Rat lungs were imaged by 19 F projection MRI of hexafluoroethane, mixed with 20% oxygen to form the inhaled gas. The 3D image had 700 μm resolution, and the data took 4.3 h to acquire. Free induction decays were collected in the presence of steady magnetic field gradients in 686 different directions. To take advantage of fast relaxation ( T 1 = 5.9 ± 0.2 ms), the repetition time was 5 ms. To eliminate signal loss from magnetic field inhomogeneities, data were collected within 2 ms of spin excitation (from 80 μs to 2 ms after the 42‐-μs π/2 pulses). The singular value decomposition of the transform from frequency to time domain was used to obtain projections despite the absence of data during and immediately after the RF pulses. Inert fluorinated gas imaging may be less expensive than polarized noble gas imaging and is appropriate for imaging steadystate rather than transient gas concentrations.