Compressed sensing with signal averaging for improved sensitivity and motion artifact reduction in fluorine‐19 MRI

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 hypotheses that a ¹⁹F MRI pulse sequence that combines a specific undersampling regime with signal averaging has both increased sensitivity and robustness against motion artifacts compared with a non‐averaged fully sampled pulse sequence, when both datasets are reconstructed with compressed sensing. As a proof of principle, numerical simulations and phantom experiments were performed on selected variable ranges to characterize the point spread function of undersampling patterns, as well as the vulnerability to noise of undersampling and reconstruction parameters with paired numbers of x signal averages and acceleration factor x (NAx ‐AFx ). The numerical simulations demonstrated that a probability density function that uses 25% of the samples to fully sample the k‐space central area allowed for an optimal balance between limited blurring and artifact incoherence. At all investigated noise levels, the Dice similarity coefficient (DSC) strongly depended on the regularization parameters and acceleration factor. In phantoms, the motion robustness of an NA8‐AF8 undersampling pattern versus NA1‐AF1 was evaluated with simulated and real motion patterns. Differences were assessed with the DSC, which was consistently higher for the NA8‐AF8 compared with the NA1‐AF1 strategy, for both simulated and real cyclic motion patterns (P < 0.001). Both strategies were validated in vivo in mice (n = 2) injected with perfluoropolyether. Here, the images displayed a sharper delineation of the liver with the NA8‐AF8 strategy than with the NA1‐AF1 strategy. In conclusion, we validated the hypotheses that in ¹⁹F MRI the combination of undersampling and averaging improves both the sensitivity and the robustness against motion artifacts.     

Earlier chronotype in patients with rheumatoid arthritis

Clinical Rheumatology - Rheumatoid arthritis (RA) patients show an earlier circadian rhythm (i.e. serum melatonin peaks earlier during the night, indicating an earlier timing of the internal...     

Deformación miocárdica de la aurícula izquierda en pacientes con lupus eritematoso sistémico

BackgroundIn patients with systemic lupus erythematosus (SLE), left ventricle diastolic dysfunction (LVDD) may be the only manifestation of cardiac involvement in anticipation of systolic dysfunction. It has been seen that myocardial deformation of the left atrium (LA), through the LA global longitudinal strain (LAGLS), may be useful in assessing diastolic function.ObjectiveTo evaluate LA function through myocardial deformation in patients with LES, and compare the LA strain in patients with active, inactive and controls.MethodsFifty patients with SLE were included and compared with 50 healthy controls paired by age and gender. Myocardial deformation was measured by transthoracic echocardiogram, to investigate the LAGLS, the strain of the three phases of the LA cycle and the strain rate. The differences between groups were compared in univariate analysis.ResultsLAGLS in SLE patients was less than in the controls (41.6% vs. 50.5%; p = .02), and in the 3 phases of the LA cycle. There were no differences in the LA strain rate in both groups (SLE 2.5 s^?1 vs. controls 2.75 s^?1; p = .1). It was also found that the LAGLS was lesser in active patients than controls and inactive.ConclusionsSLE patients have lower myocardial deformation of the LA, which is expressed as a lower diastolic function correlating with early subclinical myocardial damage.