Cardiac and respiratory self-gated 4D multi-phase steady-state imaging with ferumoxytol contrast (MUSIC)
Journal of Cardiovascular Magnetic Resonance volume 18, Article number: O51 (2016)
Our recently proposed MUSIC approach acquires ferumoxytol-enhanced 4D images using ECG and airway pressure signal for motion gating. It has been routinely used in our institution and provides detailed information on vascular anatomy. However, the airway pressure signal is only available in patients with general anesthesia (GA) and ECG is often problematic in high field strength. Therefore, we propose the self-gated MUSIC (SG-MUSIC) where cardiac and respiratory motion is compensated by retrospective data sorting base on derived SG signals. In this study, we tested SG-MUSIC on pediatric patients under GA so that the derived SG signal can be validated against the recorded physiological signal and the images compared with the original MUSIC.
The kspace is sampled using ROtating Cartesian Kspace (ROCK) method (Fig. 1) where kykz views of 3D Cartesian grid were reordered using quasi-spiral pattern with each arm starts from the outer and ends at the center kspace. The arms are rotated using segmented golden ratio in which the entire kspace is divided into 7 angular segments, each segment is sampled using golden ratio and different segments are sampled in a pseudo-random order. The extra degree of randomness ensures uniform kspace sampling even after data sorting. Cardiac and respiratory SG signal was derived from the kspace centerline using cross-correlation and band-pass filter. The data is then retrospectively gated based on respiratory SG signal and binned to 6 phases based on cardiac SG signal, followed by ESPIRiT reconstruction. Static phantom experiment was performed to validate the ROCK pattern in different settings: 1)direction of quasi-spiral arms (inward vs. outward); 2) rotating strategy (segmented golden ratio vs. golden angle). Data was sorted using physiological signal recorded from previous patient scans. 6 pediatric patients underwent GA were included in this study. 4 mg-Fe/kg ferumoxytol was administrated. The SG-MUSIC (0.9/2.9 ms, 25°, 1 mm3) was performed after clinical protocol, which includes the original MUSIC. ECG and airway pressure signal were recorded.
The time series of SG projections show that the inward quasi-spiral significantly reduces the eddy-current artifacts on SG signals. The k-space pattern shows the segmented golden ratio provides are much uniform k-space sampling after data sorting (Fig. 1). In-vivo results in Fig. 2 show the SG signal corresponds well with the recorded physiological signal and SG images is comparable with the ones using recorded physiological signal on the same data. The SG-MUSIC (TA = 6 min) has better image quality than original MUSIC (TA = 8 min) due to the use of ROCK sampling pattern and ESPIRiT reconstruction. The volumetric images allows reformatting into arbitrary planes for visualization of detailed vascular structures.
The proposed SG-MUSIC eliminates the need of physiological signal for motion gating, has slightly increased scan efficiency, while exceeding the image quality of the original MUSIC.
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Han, F., Zhou, Z., Han, E.S. et al. Cardiac and respiratory self-gated 4D multi-phase steady-state imaging with ferumoxytol contrast (MUSIC). J Cardiovasc Magn Reson 18 (Suppl 1), O51 (2016). https://doi.org/10.1186/1532-429X-18-S1-O51
- Good Image Quality
- Cartesian Grid
- Golden Ratio
- Phantom Experiment
- Arbitrary Plane