A Fast Magnetic Flux Density Measurement Method With Skip-Echo Acquired Turbo Spin Echo (SATE)

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Abstract
The measurements of magnetic flux density ( $\emph {B}_{\emph {z}}$ ) measurement needed in magnetic resonance electrical impedance tomography (MREIT) and magnetic resonance current density imaging (MRCDI) techniques often utilize spin echo (SE)-based sequences for data acquisition. The low imaging speed of SE-based methods significantly hampers the clinical applications of MREIT and MRCDI. Here, we propose a new sequence for substantially accelerating the acquisition of $\emph {B}_{\emph {z}}$ measurements. A skip-echo acquired turbo spin echo (SATE) imaging sequence based on the conventional turbo spin echo (TSE) technique was proposed by adding a skip-echo module in front of the TSE acquisition module. The skip-echo module consisted of a series of refocusing pulses without acquisition. In SATE, amplitude-modulated crusher gradients were used to remove the stimulated echo pathways, and the radiofrequency (RF) pulse shape was specially selected to preserve more signals. In efficiency evaluation experiments performed on a spherical gel phantom, we demonstrated that SATE had improved measurement efficiency compared to conventional TSE and multi-echo injection current nonlinear encoding (ME-ICNE) sequences via skipping one echo before acquiring signals. The accuracy of the $\emph {B}_{\emph {z}}$ measurements by SATE was validated against those by the ME-ICNE method, while SATE was able to accelerate the data acquisition up to 10-fold. Volumetric coverage of $\emph {B}_{\emph {z}}$ maps obtained in the phantom, pork, and human calf illustrated that SATE can reliably measure volumetric $\emph {B}_{\emph {z}}$ distributions within clinically acceptable time. The proposed SATE sequence provides a fast and effective approach for volumetric coverage of $\emph {B}_{\emph {z}}$ measurements, greatly facilitating the clinical applications of MREIT and MRCDI techniques.
Funding Information
  • STI 2030-Major Projects (2021ZD0200401, 2021YFF1200805)
  • National Natural Science Foundation of China (81971605, 31371001)
  • Key R&D Program of Zhejiang Province (2022C04031, 2021C03003, 2021C03050, 2022C03029)
  • Leading Innovation and Entrepreneurship Team of Zhejiang Province (2020R01003)
  • MOE Frontier Science Center for Brain Science & Brain-Machine Integration
  • Zhejiang University

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