Table 1.
Typical human fetal cardiovascular cine MR blood flow imaging parameters at 1.5 T.
| Acquisition | Conventional 2D PC MR 28 | Radial 2D PC MR | 4D Flow 29 |
|---|---|---|---|
| Trajectory | Cartesian | golden angle radial | Cartesian |
| TR/TE (ms) | 5.3/2.9 | 5.9/3.6 | 3.0/2.0 |
| Flip angle (degrees) | 20 | 20 | 6 |
| Velocity sensitivity | Through-plane | Through-plane | Fully encoded |
| Encoding velocity (cm/s) | 150†, 100‡ or 50§ | 150†, 100‡ or 50§ | 120 |
| Acceleration | GRAPPA, R = 2 (Reff = 1.7) | CS, R ≥ 4 | SENSE, R = 2–3 CS SENSE, R = 4–6 |
| Cardiac gating | MOG or DUS | MOG or DUS | DUS |
| Motion correction | – | Automatic, based on ROI | – |
| Maternal respiration | Free breathing | Free breathing | Shallow |
| Field of view (mm) | 340 × 234 × 5 | 340 × 340 × 5 | 300 × 300 × 50 |
| Acquired voxel size (mm) | 1.3 × 1.3 × 5.0 | 1.3 × 1.3 × 5.0 | 2.5 ×2.5 × 2.5 |
| Acquisition matrix | 256 × 176 × 1 | 256 × 256 × 1 | 120 × 120 × 20 |
| Segments | 3 | – | 2–3 |
| Reconstructed cardiac phases | 15 | 15 | 20–30 |
| Acquired temporal resolution (ms) | 32 | 29* | 24–36* |
| Signal averages | 1 | 1 | 1–2 |
| Scan duration (s) | 14–19 | 18 | 120–180 |
† 150 cm/s encoding velocity used for large arteries: ascending and descending aorta, main pulmonary artery and ductus arteriosus; ‡ 100 cm/s encoding velocity used for branch pulmonary arteries and superior vena cava; § 50 cm/s encoding velocity used for umbilical vein; TE, excitation time; TR, repetition time; MOG, metric optimized gating; DUS, Doppler ultrasound; GRAPPA, generalized autocalibrating partial parallel acquisition; CS, compressed sensing; SENSE, sensitivity encoding; R, acceleration factor; Reff, effective acceleration factor; ROI, region of interest; * additional temporal blurring depending on regularization in CS reconstruction