Magnetic resonance in medicine · 2026
Image Encoding With Blipped Gradients in an Echo Train.
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Vidarsson Logi, Sarty Gordon E
Аннотация
PURPOSE: An MRI scanner was designed and built to encode k -space points in the spin echoes occurring between 18 0 ∘ pulses in an echo train by using blipped B 0 gradient pulses applied just prior to those spin echoes.
METHODS: The proposed MRI scanner is a modification of an original design that used TRansmit Array Spatial Encoding (TRASE), a built-in B 0 gradient, and a thin RF coil defining a single axial slice. However, for TRASE, the thin profile coil needed a spatially uniform B 1 phase, and this proved difficult to achieve. We therefore replaced the RF encoding coil with a low-power B 0 gradient coil. This removed the need for a uniform spatial B 1 phase for the single slice RF coil to achieve Fourier image encoding. The pulse sequence then sent all 18 0 ∘ transmit RF pulses through the one remaining single slice RF coil with B 0 gradient pulses applied between the RF pulses. The spin echoes between the RF pulses were received and used to define the k -space points in one transverse direction. Image encoding in the perpendicular transverse direction was accomplished via frequency encoding within the built-in transverse B 0 gradient. Mineral oil phantoms were used to establish a proof-of-concept for the blipped-gradient imaging approach.
RESULTS: The phantom images give a proof-of-concept level verification of the blipped-gradient MRI design.
CONCLUSION: With work to address engineering imperfections, a blipped-gradient approach could be used to achieve the extreme Size, Weight, and Power (SWaP) requirements for a spaceworthy MRI.
METHODS: The proposed MRI scanner is a modification of an original design that used TRansmit Array Spatial Encoding (TRASE), a built-in B 0 gradient, and a thin RF coil defining a single axial slice. However, for TRASE, the thin profile coil needed a spatially uniform B 1 phase, and this proved difficult to achieve. We therefore replaced the RF encoding coil with a low-power B 0 gradient coil. This removed the need for a uniform spatial B 1 phase for the single slice RF coil to achieve Fourier image encoding. The pulse sequence then sent all 18 0 ∘ transmit RF pulses through the one remaining single slice RF coil with B 0 gradient pulses applied between the RF pulses. The spin echoes between the RF pulses were received and used to define the k -space points in one transverse direction. Image encoding in the perpendicular transverse direction was accomplished via frequency encoding within the built-in transverse B 0 gradient. Mineral oil phantoms were used to establish a proof-of-concept for the blipped-gradient imaging approach.
RESULTS: The phantom images give a proof-of-concept level verification of the blipped-gradient MRI design.
CONCLUSION: With work to address engineering imperfections, a blipped-gradient approach could be used to achieve the extreme Size, Weight, and Power (SWaP) requirements for a spaceworthy MRI.