Skip to main content

Table 2 4D Flow CMR scan parameters

From: 4D flow cardiovascular magnetic resonance consensus statement

  Ideally Reason Limiting factor Consensus value
Acquisition Parameters
Field of view Max SNR, coverage Scan time, system imperfections Cover region of interest
Spatial resolutiona Maximum, at least 5–6 voxels across vessel diameter of interestb, isotropic resolution. Accuracy Scan time, SNR <2.5×2.5×2.5 mm3 for aorta or pulmonary artery
<3.0×3.0×3.0 mm3 for whole heart and greater vessels
Velocity encoding timing (beat- vs. TR-interleaved) TR-interleaved Avoid inter-cycle variability Temporal resolution TR-interleaved
k-space segmentation factor 1 Accuracy (temporal resolution) Scan time 2
Temporal resolutionc Max Accuracy Scan time <40 ms
ECG synchronizationd Retrospective Cover entire ECG cycle, avoid sequence interruption Reconstruction complexity If available: retrospective
Else: Prospectivee
Respiratory motion compensationf 100 % acceptance, motion correction Scan time, reduction of breathing artifacts Reconstruction complexity, robustness, breathing artefacts (ghosting and blurring) If available: Leading or trailing MR navigator on liver/diaphragm interface, 6 mm window size, typically resulting in 50 % acceptance rate.
Otherwise: Bellows with 50 % acceptance rate.
Partial k-space coverage in phase- and slice-encoding directions Full k-space coverage SNR, resolution Scan time If available: Elliptical k-space
Otherwise: Half scan 75 % × 75 % (y × z)
Flip Angleg Ernst angle: α = acos(e-TR/T1) SNR Contrast vs. SNR Ernst angle
Parallel Imaging No parallel imaging SNR Scan time R = 2-3 (depends on #channels in coil array)
k-t undersamplingh No k-t under sampling SNR Scan time If available: R = 4-5
Venc Maximum expected velocity, multiple vencs VNR, avoid aliasing Scan time Single venc, 10 % higher than maximum expected velocity
Postprocessing Parameters
Maxwell correction Yes Accuracy   Yes
Eddy current correction Yes Accuracy Different methods and their validity and robustness Yes
Phase unwrapping Yes Accuracy Different methods and their validity and robustness Yes
Gradient non-linearity correction Yes Accuracy Availability If available
  1. aAlways indicate the effectively acquired resolution in combination with the interpolated resolution
  2. bStudies have demonstrated that 5–6 voxels across the vessel diameter is sufficient for flow volume quantification [165]
  3. cAlways indicate the effectively acquired resolution. If a temporal interpolation is performed, also indicate the interpolated temporal resolution along with the interpolation method used
  4. dSo called self-gating techniques have been evaluated and may become an alternative to the ECG [32]
  5. eFor prospective gating, analyses that involve integration over the whole cardiac cycle needs to be accompanied with a description of how the incomplete temporal coverage was handled
  6. fDifferent types of respiratory navigators exist; variants include approaches that allow less motion in the central parts of k-space. Always describe the method that has been used and indicate the mean navigator efficiency in percent as well as the navigator acceptance window in mm. For fix window sizes and no k-space reordering, 6 mm navigator window is recommended, and this typically results in 50 % navigator efficiency
  7. gThe SNR is strongly dependent on the in-flow effect, therefore the flip angle can be and is often chosen higher than the Ernst angle. When using contrast agents, the Ernst angle further increases (due to lower T1)
  8. h k-t undersampling factor 4–5 in combination with conventional parallel imaging factor 2–3 is not recommended