Arc-ZTE: Continuously-Slewed Zero-TE Imaging With Incoherent Temporal Sampling for Near-Silent Dynamic MRI.

purposeTo enable flexible dynamic and DCE MRI with low acoustic noise and high spatiotemporal resolution using zero echo time (ZTE) imaging.

methodsThis work proposes Arc-ZTE, a technique in which the readout gradients of ZTE are continuously-slewed to form arcs in k-space that are sequentially rotated to yield an incoherent trajectory. These rotations are selected via an optimization procedure that both promotes temporal k-space coverage and penalizes gradient refocusing. Arc-ZTE was evaluated against existing radial ZTE schemes based on metrics for acoustic noise, k-space coverage uniformity, and sampling incoherence. Phantom and in vivo demonstrations were conducted to evaluate image quality at high temporal resolutions.

resultsArc-ZTE achieved stable k-space coverage and improved sampling incoherence over a range of temporal resolutions, with respect to radial ZTE schemes. Although increasing arc curvature increased its acoustic noise over standard radial ZTE (by 0.3-14.2 dB), Arc-ZTE remained substantially quieter than conventional 3D sequences by 20-35 dB. In vivo experiments demonstrated that time-resolved Arc-ZTE effectively captured dynamics of respiratory motion and contrast uptake when reconstructed at 0.5 and 1.1 s/frame respectively.

conclusionArc-ZTE enables flexible, time-resolved, near-silent dynamic MRI through incoherent temporal sampling, which allows data to be retrospectively binned into a flexible choice of temporal resolution without modifying the trajectory design. This work has the potential to significantly improve the success rates of dynamic imaging among neonates, young children, and other sound-sensitive patients.