Background: Cardiovascular flow is commonly assessed with two-dimensional, phase contrast (2D PC-MRI). However, scan prescription and acquisition over multiple planes is lengthy, often requires direct physician oversight, and has inconsistent results. Time-resolved volumetric PC-MRI (4D flow) may address these limitations. Objective: We assess the degree of agreement and internal consistency between 2D and 4D flow quantification in our clinical population. Method: Software enabling flow calculation from 4D flow was developed in Java. With IRB approval and HIPAA compliance, eighteen consecutive patients without shunts were identified who underwent both (a) conventional 2D PC-MRI of the aorta and main pulmonary artery and (b) 4D flow imaging. Aortic and pulmonary flow rates were assessed with both techniques. Results: Both methods showed general agreement in flow rates (ρ: 0.87-0.90). Systemic and pulmonary arterial flow rates were well-correlated (ρ: 4D 0.98-0.99, 2D 0.93), but more closely matched with 4D (p<0.05, Brown-Forsythe). Pulmonary flow rates were lower than systemic rates for 2D (p<0.05, two-sample t-test). In a sub-analysis of patients without pulmonary or aortic regurgitation, 2D showed improved correlation of flow rates while 4D phase-contrast remained tightly correlated (ρ: 4D 0.99-1.00, 2D 0.99). Conclusion: 4D PC-MRI demonstrates greater consistency than conventional 2D PC-MRI for flow quantification.

<b><i>Background:</i></b> Patients on maintenance hemodialysis (MHD) exhibit muscle wasting and impaired physical function which can be reversed with regular exercise, but accessibility to exercise programs for this unique population is lacking. We assessed the efficacy of a home-based exercise program on a broad range of indices of physical function, quality of life (QoL), and cognitive decline in patients with MHD. <b><i>Design and Methods:</i></b> Twenty-eight MHD patients, mean age 66 ± 7 years, were randomized to a 12-week home-based, case-managed aerobic and resistance exercise program or to usual care (13 exercise and 15 usual care). Comparisons were made for peak VO₂, ventilatory inefficiency, 6-min walk test (6MWT), 1-min sit-to-stand (1STS), muscle strength, body composition, QoL, and cognitive measures. <b><i>Results:</i></b> Peak VO₂ improved significantly in the exercise group (<i>p</i> = 0.01 between groups); exercise time improved by 41 and 36% at the ventilatory threshold and peak exercise, respectively (<i>p</i> &#x3c; 0.01 between groups), but there were no differences in ventilatory efficiency. Trends for improvements in 6MWT and 1STS in the exercise group were observed, but no differences were observed in strength or body composition. Among measures of QoL, general health determined by the SF-36 improved in the exercise group, but there were no differences between groups in cognitive function. <b><i>Conclusions:</i></b> MHD patients improved exercise capacity and some indices of QoL following a 12-week home-based exercise program. Home-based exercise is feasible for patients undergoing MHD and may help to obviate accessibility barriers to regular exercise.

OPEN ACCESS Citation: Zhang Y, Vakhtin AA, Jennings JS, Massaband P, Wintermark M, Craig PL, et al. (2020) Diffusion tensor tractography of brainstem fibers and its application in pain. PLoS ONE 15(2): e0213952. https://doi.org/10.

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