MRSI via fully-refocused spatiotemporal encoding with polychromatic spectral pulses.
A novel method for the rapid acquisition of quality multi-slice 2D images targeting a small number of spectroscopic resonances, is introduced and illustrated. The method exploits the robustness derived from recently proposed spatiotemporal encoding (SPEN) methods, when operating in the so-called "fully refocused" mode. Fully-refocused SPEN provides high-fidelity single-shot images thanks to its refocusing of all offset-derived effects throughout the course of the acquisition. This refocusing, however, prevents exploiting such robustness for spectroscopic imaging. We propose here a solution to this limitation, based on the use of polychromatic refocusing pulses. It is shown that if used to address a series of a priori known resonance positions, these pulses can lead to quality spectroscopic images in a small number of scans - generally equal or slightly larger than the number of targeted peaks. Such strategy is explored in combination with both fully-refocused SPEN and echo-planar-imaging (EPI) acquisitions. The expected SPEN advantages were observed in both phantom-based models, and in in vivo results of fat and water separation in mice at 7 T.
Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel; Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, Fujian 361005, China.
Zhiyong
Z
Zhang
Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel. Electronic address: lucio.frydman@weizmann.ac.il.
Lucio
L
Frydman
D000273:Adipose Tissue / Q000033:anatomy & histology / Q000737:chemistry; D000465:Algorithms; D000818:Animals; D001834:Body Water / Q000737:chemistry; D003116:Color; D017352:Echo-Planar Imaging / Q000379:methods / Q000706:statistics & numerical data; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000706:statistics & numerical data; D051379:Mice; D019047:Phantoms, Imaging
Fast spectroscopic imaging; Fully-refocused acquisitions; MRSI; Polychromatic RF pulses; SPEN MRI