PurposeTo image multidimensional flow in fetuses using golden-angle radial phase contrast cardiovascular magnetic resonance (PC-CMR) with motion correction and retrospective gating.MethodsA novel PC-CMR method was developed using an ungated golden-angle radial acquisition with continuously incremented velocity encoding. Healthy subjects (n = 5, 27 ± 3 years, males) and pregnant females (n = 5, 34 ± 2 weeks gestation) were imaged at 3 T using the proposed sequence. Real-time reconstructions were first performed for retrospective motion correction and cardiac gating (using metric optimized gating, MOG). CINE reconstructions of multidimensional flow were then performed using the corrected and gated data.ResultsIn adults, flows obtained using the proposed method agreed strongly with those obtained using a conventionally gated Cartesian acquisition. Across the five adults, bias and limits of agreement were − 1.0 cm/s and [− 5.1, 3.2] cm/s for mean velocities and − 1.1 cm/s and [− 6.5, 4.3] cm/s for peak velocities. Temporal correlation between corresponding waveforms was also high (R~ 0.98). Calculated timing errors between MOG and pulse-gating RR intervals were low (~ 20 ms). First insights into multidimensional fetal blood flows were achieved. Inter-subject consistency in fetal descending aortic flows (n = 3) was strong with an average velocity of 27.1 ± 0.4 cm/s, peak systolic velocity of 70.0 ± 1.8 cm/s and an intra-class correlation coefficient of 0.95 between the velocity waveforms. In one fetal case, high flow waveform reproducibility was demonstrated in the ascending aorta (R = 0.97) and main pulmonary artery (R = 0.99).ConclusionMultidimensional PC-CMR of fetal flow was developed and validated, incorporating retrospective motion compensation and cardiac gating. Using this method, the first quantification and visualization of multidimensional fetal blood flow was achieved using CMR.Electronic supplementary materialThe online version of this article (10.1186/s12968-018-0498-z) contains supplementary material, which is available to authorized users.
Funding information Labatt Family Heart Centre FellowshipPurpose: To test and implement a motion-robust and respiratory-resolved 3D Radial Flow framework that addresses the need for rapid, high resolution imaging in neonatal patients with congenital heart disease. Methods: A 4-point velocity encoding and 3D radial trajectory with double-golden angle ordering was combined with bulk motion correction (from projection center of mass) and respiration phase detection (from principal component analysis of heartbeat-averaged data) to create motion-robust 3D velocity cardiac time-averaged data. This framework was tested in a whole-chest digital phantom with simulated bulk and realistic physiological motion. In vivo imaging was performed in 20 congenital heart disease infants under feed-and-sleep with submillimeter isotropic resolution in ~3 min. Flows were validated against clinical 2D PCMRI and whole-heart visualizations of blood flow were performed. Results: The proposed framework resolved all simulated digital phantom motion states (mean ± standard error: rotation -azimuthal = 0.29 ± 0.02°; translation -T y = 1.29 ± 0.12 mm, T z = −0.27 ± 0.13 mm; rotation+translation -polar = 0.49 ± 0.16°, T x = −2.47 ± 0.51 mm, T z = 5.78 ± 1.33 mm). Measured timing errors of peak expiration across all signal-to-noise ratio values were 22% of the true respiratory period (range = [404-489 ± 298-334] ms). For in vivo imaging, motion correction improved 3D Radial Flow measurements (no correction: R 2 = 0.62, root mean square error = 0.80 L/min/m 2 , Bland-Altman bias [limits of agreement] = −0.21 [−1.40, 0.94] L/min/m 2 ; motion corrected, expiration: R 2 = 0.90, root mean square error = 0.46 L/min/m 2 , bias [limits of agreement] = 0.06 [−0.49, 0.62] L/min/m 2 ).Respiratory-resolved 3D velocity visualizations were achieved in various neonatal pathologies pre-and postsurgical correction. |
BackgroundPhase contrast MRI in the great vessels is a potential clinical tool for managing fetal pathologies. One challenge is the uncontrollable fetal motion, potentially corrupting flow quantifications.PurposeTo demonstrate improvements in fetal blood flow quantification in great vessels using retrospectively motion‐corrected golden‐angle radial phase contrast MRI relative to Cartesian phase contrast MRI.Study TypeMethod comparison.Phantom/SubjectsComputer simulation. Seventeen pregnant volunteers.Field Strength/Sequence1.5T and 3T. Cartesian and golden‐angle radial phase contrast MRI.AssessmentThrough computer simulations, radial (with and without retrospective motion correction) and Cartesian phase contrast MRI were compared using flow deviations. in vivo Cartesian and radial phase contrast MRI measurements and reconstruction qualities were compared in pregnancies. Cartesian data were reconstructed into gated reconstructions (CINEs) after cardiac gating with metric optimized gating (MOG). For radial data, real‐time reconstructions were performed for motion correction and MOG followed by CINE reconstructions.Statistical TestsWilcoxon signed‐rank test. Linear regression. Bland–Altman plots. Student's t‐test.ResultsSimulations showed significant improvements (P < 0.05) in flow accuracy and reconstruction quality with motion correction ([mean/peak] flow errors with ±5 mm motion corruption: Cartesian [35 ± 1/115 ± 7] mL/s, motion uncorrected radial [25 ± 1/75 ± 2] mL/s and motion‐corrected radial [1.0 ± 0.5/−5 ± 1] mL/s). in vivo Cartesian reconstructions without motion correction had lower quality than the motion‐corrected radial reconstructions (P < 0.05). Across all fetal mean flow measurements, the bias [limits of agreement] between the two measurements were −0.2 [−76, 75] mL/min/kg, while the linear regression coefficients were (Mradial = 0.81 × MCartesian + 29.8 [mL/min/kg], r2 = 0.67). The corresponding measures for the peak fetal flows were −23 [−214, 167] mL/min/kg and (Pradial = 0.95 × PCartesian–1.2 [mL/min/kg], r2 = 0.80). Cartesian reconstructions of low quality showed significantly higher estimated mean and peak (P < 0.05) flows than the corresponding radial reconstructions.Data ConclusionSimulations showed that radial phase contrast MRI with motion compensation improved flow accuracy. For fetal measurements, motion‐corrected radial reconstructions showed better image quality than, and different flow values from, Cartesian reconstructions.Level of Evidence 1.Technical Efficacy Stage 1.J. MAGN. RESON. IMAGING 2021;53:540–551.
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