Evaluation of Valvular Insufficiency and Shunts with Parallel-imaging Compressed-sensing 4D Phase-contrast MR Imaging with Stereoscopic 3D Velocity-fusion Volume-rendered Visualization

Abstract

Purpose:To assess the potential of compressed-sensing parallel-imaging four-dimensional (4D) phase-contrast magnetic resonance (MR) imaging and specialized imaging software in the evaluation of valvular insufficiency and intracardiac shunts in patients with congenital heart disease. Materials andMethods:Institutional review board approval was obtained for this HIPAAcompliant study. Thirty-four consecutive retrospectively identified patients in whom a compressed-sensing parallel-imaging 4D phase-contrast sequence was performed as part of routine clinical cardiac MR imaging between March 2010 and August 2011 and who had undergone echocardiography were included. Multiplanar, volume-rendered, and stereoscopic three-dimensional velocityfusion visualization algorithms were developed and implemented in Java and OpenGL. Two radiologists independently reviewed 4D phase-contrast studies for each of 34 patients (mean age, 6 years; age range, 10 months to 21 years) and tabulated visible shunts and valvular regurgitation. These results were compared with color Doppler echocardiographic and cardiac MR imaging reports, which were generated without 4D phase-contrast visualization. Cohen k statistics were computed to assess interobserver agreement and agreement with echocardiographic results. Results:The 4D phase-contrast acquisitions were performed, on average, in less than 10 minutes. Among 123 valves seen in 34 4D phasecontrast studies, 29 regurgitant valves were identified, with good agreement between observers (k = 0.85). There was also good agreement with the presence of at least mild regurgitation at echocardiography (observer 1, k = 0.76; observer 2, k = 0.77) with high sensitivity (observer 1, 75%; observer 2, 82%) and specificity (observer 1, 97%; observer 2, 95%) relative to the reference standard. Eight intracardiac shunts were identified, four of which were not visible with conventional cardiac MR imaging but were detected with echocardiography. No intracardiac shunts were found with echocardiography alone. Conclusion:With velocity-fusion visualization, the compressed-sensing parallel-imaging 4D phase-contrast sequence can augment conventional cardiac MR imaging by improving sensitivity for and depiction of hemodynamically significant shunts and valvular regurgitation.q RSNA, 2012 Supplemental material: http://radiology.rsna.org/lookup /suppl

Compressed sensing MRI: a review of the clinical literature

“…1,2,18,21,22,25,28,29 All of these studies found that the combined methodology produced images deemed acceptable or not significantly different from fully sampled images, while employing acceleration rates from 23 to 7.23, depending on the application. Five of these studies compared the combined method with the standard imaging protocol for the respective study's imaging application.…”

“…32 A total of 275 subjects were imaged across the 18 studies (range, 3-34; mean 5 15.28; median 5 11.5; standard deviation 5 10.23). 7 studies imaged healthy subjects, 15,[19][20][21]23,24,27 and 11 imaged patients referred for the type of imaging under consideration 1,2,14,[16][17][18]22,25,26,28,29 ( Figure 5). …”

“…22 In 10 studies human readers rated images. 1,15,18,[21][22][23][26][27][28][29] In eight studies, accurate measurement of a quantitative metric with CS MRI (e.g. contrast uptake or metabolite concentration) was assessed.…”

Fast and Accurate 4D Flow MRI for Cardiovascular Blood Flow Assessment

“…Compressed sensing in combination with Poisson disk undersampling has also been used to accelerate 4D flow MRI, reaching net acceleration factors of 2 to 5 [109][110].…”

“…Other methods, such as k-t PCA or compressed sensing, have been demonstrated to achieve acceleration factors up to 8 [109][110]139]. The combination of spiral 4D flow MRI with such methods may permit even higher acceleration factors.…”