IEEE transactions on bio-medical engineering
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IEEE Trans Biomed Eng · Dec 2013
Noise Effects in Various Quantitative Susceptibility Mapping Methods.
Various regularization methods have been proposed for single-orientation quantitative susceptibility mapping (QSM), which is an ill-posed magnetic field to susceptibility source inverse problem. Noise amplification, a major issue in inverse problems, manifests as streaking artifacts and quantification errors in QSM and has not been comparatively evaluated in these algorithms. In this paper, various QSM methods were systematically categorized for noise analysis. ⋯ The effects of noise in these QSM methods were evaluated by reconstruction errors in simulation and image quality in 50 consecutive human subjects. Bayesian QSM methods with noise weighting consistently reduced root mean squared errors in numerical simulations and increased image quality scores in the human brain images, when compared to non-Bayesian methods and to corresponding Bayesian methods without noise weighting (p ≤ 0.001). In summary, noise effects in QSM can be reduced using Bayesian methods with proper noise weighting.
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IEEE Trans Biomed Eng · Dec 2013
Assessing the Progression of Ventilator-Induced Lung Injury in Mice.
Patients with acute respiratory distress syndrome receiving mechanical ventilation typically experience repetitive closure (derecruitment) and subsequent reopening (recruitment) of airways and alveoli. This can lead, over time, to further ventilator-induced lung injury (VILI). Recruitment and derecruitment (R/D) thus reflect both the current level of lung injury and the risk for sustaining further injury. ⋯ To interpret these findings in quantitative terms, we developed a computational model of the lung in which changes in lung volume occurred both via R/D and distention of already open lung units. Fitting this model to measured PV loops indicates that VILI causes R/D both to increase and to occur at progressively higher pressures, and that the lung tissue that remains open during the breath becomes progressively more overdistended. We conclude that the dynamic PV loop in conjunction with our computational model can be used to assess the current injury state of the lung as well as its likelihood of sustaining further VILI.