Fast 3D ultrashort echo-time spiral projection imaging using golden-angle: A flexible protocol for in vivo mouse imaging at high magnetic field

PurposeTo develop a fast three-dimensional (3D) k-space encoding method based on spiral projection imaging (SPI) with an interleaved golden-angle approach and to validate this novel sequence on small animal models. MethodsA disk-like trajectory, in which each disk contained spirals, was developed. The 3D encoding was performed by tilting the disks with a golden angle. The sharpness was first calculated at different T2* values. Then, the sharpness was measured on phantom using variable undersampling ratios. Finally, the sampling method was validated by whole brain time-of-flight angiography and ultrasmall superparamagnetic iron oxide (USPIO) enhanced free-breathing liver angiography on mouse. ResultsThe in vitro results demonstrated the robustness of the method for short T2* and high undersampling ratios. In vivo experiments showed the ability to properly detect small vessels in the brain with an acquisition time shorter than 1min. Free-breathing mice liver angiography showed the insensitivity of this protocol toward motions and flow artifacts, and enabled the visualization of liver motion during breathing. ConclusionsThe method implemented here allowed fast 3D k-space sampling with a high undersampling ratio. Combining the advantages of center-out spirals with the flexibility of the golden angle approach could have major implications for real-time imaging. Magn Reson Med 77:1831-1840, 2017. (c) 2016 International Society for Magnetic Resonance in Medicine