PURPOSE: To analyze and correct for eddy current-induced phase imperfections in cardiac cine balanced steady-state free precession (bSSFP) imaging. METHODS: Eddy current-induced phase offsets were measured for different phase-encoding schemes using a higher order dynamic field camera. Based on these measurements, offset phases were corrected for in postprocessing and by run-time phase compensation applying radiofrequency phase increments and additional compensatory gradient areas. The findings were validated using numerical simulations, phantom experiments, and in vivo cardiac scans. RESULTS: Depending on the phase-encoding scheme, significant eddy current-induced phase offsets were detected. Time-varying phase offsets were observed at subsequent excitations leading to steady-state distortions and hence to profile-dependent amplitude modulations in k-space. Taking into account measured k-space trajectories algebraic image reconstruction allowed compensating imperfect spatial encoding. Correction of amplitude modulations was successfully accomplished by run-time phase compensation. CONCLUSION: Using magnetic field monitoring, artifacts in cine balanced steady-state free precession caused by uncompensated eddy current fields can be significantly reduced.
PURPOSE: To analyze and correct for eddy current-induced phase imperfections in cardiac cine balanced steady-state free precession (bSSFP) imaging. METHODS: Eddy current-induced phase offsets were measured for different phase-encoding schemes using a higher order dynamic field camera. Based on these measurements, offset phases were corrected for in postprocessing and by run-time phase compensation applying radiofrequency phase increments and additional compensatory gradient areas. The findings were validated using numerical simulations, phantom experiments, and in vivo cardiac scans. RESULTS: Depending on the phase-encoding scheme, significant eddy current-induced phase offsets were detected. Time-varying phase offsets were observed at subsequent excitations leading to steady-state distortions and hence to profile-dependent amplitude modulations in k-space. Taking into account measured k-space trajectories algebraic image reconstruction allowed compensating imperfect spatial encoding. Correction of amplitude modulations was successfully accomplished by run-time phase compensation. CONCLUSION: Using magnetic field monitoring, artifacts in cine balanced steady-state free precession caused by uncompensated eddy current fields can be significantly reduced.
Authors: Tom Bruijnen; Bjorn Stemkens; Cornelis Antonius Theodorus van den Berg; Rob Hendrikus Nicolaas Tijssen Journal: Magn Reson Med Date: 2019-11-22 Impact factor: 4.668