TY - JOUR

T1 - Accelerated 2D Cartesian MRI with an 8-channel local B0 coil array combined with parallel imaging

AU - Tian, Rui

AU - Uecker, Martin

AU - Davids, Mathias

AU - Thielscher, Axel

AU - Buckenmaier, Kai

AU - Holder, Oliver

AU - Steffen, Theodor

AU - Scheffler, Klaus

N1 - © 2023 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.

PY - 2024/2

Y1 - 2024/2

N2 - PURPOSE: In MRI, the magnetization of nuclear spins is spatially encoded with linear gradients and radiofrequency receivers sensitivity profiles to produce images, which inherently leads to a long scan time. Cartesian MRI, as widely adopted for clinical scans, can be accelerated with parallel imaging and rapid magnetic field modulation during signal readout. Here, by using an 8-channel local B 0 $$ {\mathrm{B}}_0 $$ coil array, the modulation scheme optimized for sampling efficiency is investigated to speed up 2D Cartesian scans.THEORY AND METHODS: An 8-channel local B 0 $$ {\mathrm{B}}_0 $$ coil array is made to carry sinusoidal currents during signal readout to accelerate 2D Cartesian scans. An MRI sampling theory based on reproducing kernel Hilbert space is exploited to visualize the efficiency of nonlinear encoding in arbitrary sampling duration. A field calibration method using current monitors for local B 0 $$ {\mathrm{B}}_0 $$ coils and the ESPIRiT algorithm is proposed to facilitate image reconstruction. Image acceleration with various modulation field shapes, aliasing control, and distinct modulation frequencies are scrutinized to find an optimized modulation scheme. A safety evaluation is conducted. In vivo 2D Cartesian scans are accelerated by the local B 0 $$ {\mathrm{B}}_0 $$ coils.RESULTS: For 2D Cartesian MRI, the optimal modulation field by this local B 0 $$ {\mathrm{B}}_0 $$ array converges to a nearly linear gradient field. With the field calibration technique, it accelerates the in vivo scans (i.e., proved safe) by threefold and eightfold free of visible artifacts, without and with SENSE, respectively.CONCLUSION: The nonlinear encoding analysis tool, the field calibration method, the safety evaluation procedures, and the in vivo reconstructed scans make significant steps to push MRI speed further with the local B 0 $$ {\mathrm{B}}_0 $$ coil array.

AB - PURPOSE: In MRI, the magnetization of nuclear spins is spatially encoded with linear gradients and radiofrequency receivers sensitivity profiles to produce images, which inherently leads to a long scan time. Cartesian MRI, as widely adopted for clinical scans, can be accelerated with parallel imaging and rapid magnetic field modulation during signal readout. Here, by using an 8-channel local B 0 $$ {\mathrm{B}}_0 $$ coil array, the modulation scheme optimized for sampling efficiency is investigated to speed up 2D Cartesian scans.THEORY AND METHODS: An 8-channel local B 0 $$ {\mathrm{B}}_0 $$ coil array is made to carry sinusoidal currents during signal readout to accelerate 2D Cartesian scans. An MRI sampling theory based on reproducing kernel Hilbert space is exploited to visualize the efficiency of nonlinear encoding in arbitrary sampling duration. A field calibration method using current monitors for local B 0 $$ {\mathrm{B}}_0 $$ coils and the ESPIRiT algorithm is proposed to facilitate image reconstruction. Image acceleration with various modulation field shapes, aliasing control, and distinct modulation frequencies are scrutinized to find an optimized modulation scheme. A safety evaluation is conducted. In vivo 2D Cartesian scans are accelerated by the local B 0 $$ {\mathrm{B}}_0 $$ coils.RESULTS: For 2D Cartesian MRI, the optimal modulation field by this local B 0 $$ {\mathrm{B}}_0 $$ array converges to a nearly linear gradient field. With the field calibration technique, it accelerates the in vivo scans (i.e., proved safe) by threefold and eightfold free of visible artifacts, without and with SENSE, respectively.CONCLUSION: The nonlinear encoding analysis tool, the field calibration method, the safety evaluation procedures, and the in vivo reconstructed scans make significant steps to push MRI speed further with the local B 0 $$ {\mathrm{B}}_0 $$ coil array.

KW - image acceleration

KW - magnetic field calibration

KW - nonlinear gradient

KW - parallel imaging

KW - reproducing kernel Hilbert Space

KW - wave-CAIPI

UR - http://www.scopus.com/inward/record.url?scp=85174599484&partnerID=8YFLogxK

U2 - 10.1002/mrm.29799

DO - 10.1002/mrm.29799

M3 - Journal article

C2 - 37867407

SN - 0740-3194

VL - 91

SP - 443

EP - 465

JO - Magnetic Resonance in Medicine

JF - Magnetic Resonance in Medicine

IS - 2

ER -