  Fluorine-19 (19F) MRI of injected perfluorocarbon emulsions (PFCs) allows for
the non-invasive quantification of inflammation and cell tracking, but suffers
from a low signal-to-noise ratio and extended scan time. To address this
limitation, we tested the hypothesis that a 19F MRI pulse sequence that
combines a specific undersampling regime with signal averaging has increased
sensitivity and robustness against motion artifacts compared to a non-averaged
fully-sampled dataset, when both are reconstructed with compressed sensing. To
this end, numerical simulations and phantom experiments were performed to
characterize the point spread function (PSF) of undersampling patterns and the
vulnerability to noise of acquisition-reconstruction strategies with paired
numbers of x signal averages and acceleration factor x (NAx-AFx). At all
investigated noise levels, the DSC of the acquisition-reconstruction strategies
strongly depended on the regularization parameters and acceleration factor. In
phantoms, motion robustness of an NA8-AF8 undersampling pattern versus NA1-AF1
was evaluated with simulated and real motions. Differences were assessed with
Dice similarity coefficients (DSC), and were consistently higher for NA8-AF8
compared to NA1-AF1 strategy, for both simulated and real cyclic motions
(P<0.001). Both acquisition-reconstruction strategies were validated in vivo in
mice (n=2) injected with perfluoropolyether. These images displayed a sharper
delineation of the liver with the NA8-AF8 strategy than with the NA1-AF1
strategy. In conclusion, we validated the hypothesis that in 19F MRI, the
combination of undersampling and averaging improves both the sensitivity and
the robustness against motion artifacts compared to a non-averaged
fully-sampled dataset, when both are reconstructed with compressed sensing.
