Purpose To evaluate precision and accuracy of parallel-imaging compressed-sensing 4D phase contrast (PICS-4DPC) MRI venous flow quantification in children with patients referred for cardiac MRI at our children’s hospital. Materials and Methods With IRB approval and HIPAA compliance, 22 consecutive patients without shunts underwent 4DPC as part of clinical cardiac MRI examinations. Flow measurements were obtained in the superior and inferior vena cava, ascending and descending aorta and the pulmonary trunk. Conservation of flow to the upper, lower and whole body was used as an internal physiologic control. The arterial and venous flow rates at each location were compared with paired t-tests and F-tests to assess relative accuracy and precision. RESULTS Arterial and venous flow measurements were strongly correlated for the upper (ρ=0.89), lower (ρ=0.96) and whole body (ρ=0.97); net aortic and pulmonary trunk flow rates were also tightly correlated (ρ=0.97). There was no significant difference in the value or precision of arterial and venous flow measurements in upper, lower or whole body, though there was a trend toward improved precision with lower velocity-encoding settings. Conclusion With PICS-4DPC MRI, the accuracy and precision of venous flow quantification are comparable to that of arterial flow quantification at velocity-encodings appropriate for arterial vessels.

Purpose To investigate four-dimensional flow denoising using the divergence-free wavelet (DFW) transform and compare its performance with existing techniques. Theory and Methods DFW is a vector-wavelet that provides a sparse representation of flow in a generally divergence-free field and can be used to enforce “soft” divergence-free conditions when discretization and partial voluming result in numerical nondivergence-free components. Efficient denoising is achieved by appropriate shrinkage of divergence-free wavelet and nondivergence-free coefficients. SureShrink and cycle spinning are investigated to further improve denoising performance. Results DFW denoising was compared with existing methods on simulated and phantom data and was shown to yield better noise reduction overall while being robust to segmentation errors. The processing was applied to in vivo data and was demonstrated to improve visualization while preserving quantifications of flow data. Conclusion DFW denoising of four-dimensional flow data was shown to reduce noise levels in flow data both quantitatively and visually.

Purpose To determine whether it is feasible to use solely an accelerated 4D-PC MRI acquisition to quantify net and regurgitant flow volume through each of the cardiac valves. Materials and Methods Accelerated, 4D-PC MRI examinations performed between March 2010 through June 2011 as part of routine MRI examinations for congenital, structural heart disease were retrospectively reviewed and analyzed using valve-tracking visualization and quantification algorithms developed in Java and OpenGL. Excluding patients with transposition or single ventricle physiology, a total of 34 consecutive pediatric patients (19 male, 15 female; mean age 6.9 years; age range 10 months-15 years) were identified. 4D-PC flow measurements were compared at each valve and against routine measurements from conventional cardiac MRI using Bland-Altman and Pearson correlation analysis. Results Inlet and outlet valve net flow were highly correlated between all valves (ρ=0.940–0.985). The sum of forward flow at the outlet valve and regurgitant flow at the inlet valve were consistent with volumetric displacements each ventricle (ρ=0.939–0.948). These were also highly consistent with conventional planar MRI measurements of with net flow (ρ=0.923–0.935) and regurgitant fractions (ρ=0.917–0.972) at the outlet valve and ventricular volumes (ρ=0.925–0.965). Conclusion It is possible to obtain consistent measurements of net and regurgitant blood flow across the inlet and outlet valves relying solely on accelerated 4D-PC. This may facilitate more efficient clinical quantification of valvular regurgitation.

Background Lymphatic malformations (LM) can be challenging to treat. Mainstay interventions including surgery and sclerotherapy are invasive and can result in local recurrence and complications. Objective To assess the effect of 20 weeks of oral sildenafil on reducing LM volume and symptoms in children. Methods Seven children (4 boys, 3 girls; ages 13–85 months) with LMs were given oral sildenafil for 20 weeks in this open-label study. The volume of the LM was calculated blindly using magnetic resonance imaging performed before and after 20 weeks of sildenafil. LMs were assessed clinically on weeks 4, 12, 20, and 32. Both the physician and parents evaluated the LM in comparison to baseline. Results Four subjects had a LM volume decrease (1.0–31.7%). In 2 subjects, despite a LM volume increase (1.1–3.7%), clinical improvement was noted while on sildenafil. One subject had a 29.6% increase in LM volume and no therapeutic response. LMs of all 6 subjects who experienced a therapeutic response on sildenafil softened and became easily compressible. Adverse events were minimal. Limitations A randomized-controlled trial will be necessary to verify the effects of sildenafil on LMs. Conclusions Sildenafil can reduce LM volume and symptoms in some children.

2 J. MAGN. RESON. IMAGING 2017;45:1700-1711.