PURPOSE: To evaluate the feasibility of using asymmetric sampling in a three-dimensional, magnetization-prepared, segmented true-FISP (fast imaging with steady-state precession) sequence in order to reduce the sensitivity to resonance offsets, while simultaneously improving imaging speed. MATERIALS AND METHODS: Asymmetric sampling reduces the repetition time, leading to reduced resonance offset effects and improved resolution in a fixed imaging time. However, it introduces additional phase terms due to blood flow, which can cause image artifacts. Computer simulations were performed to study the off-resonance and flow effects of asymmetric sampling in true-FISP. Coronary artery imaging was performed in healthy volunteers. RESULTS: Simulations and volunteer studies show that image artifacts due to flow-induced phase variations may be acceptable at low velocities. Volunteer studies demonstrate that relatively high-resolution coronary artery images can then be acquired within a single breath-hold with segmented three-dimensional true-FISP imaging using data asymmetry in the readout direction. CONCLUSION: Asymmetric sampling is a useful modification to true-FISP for reducing the off-resonance artifacts and improving imaging speed when the flow velocities are small. Copyright 2002 Wiley-Liss, Inc.
PURPOSE: To evaluate the feasibility of using asymmetric sampling in a three-dimensional, magnetization-prepared, segmented true-FISP (fast imaging with steady-state precession) sequence in order to reduce the sensitivity to resonance offsets, while simultaneously improving imaging speed. MATERIALS AND METHODS: Asymmetric sampling reduces the repetition time, leading to reduced resonance offset effects and improved resolution in a fixed imaging time. However, it introduces additional phase terms due to blood flow, which can cause image artifacts. Computer simulations were performed to study the off-resonance and flow effects of asymmetric sampling in true-FISP. Coronary artery imaging was performed in healthy volunteers. RESULTS: Simulations and volunteer studies show that image artifacts due to flow-induced phase variations may be acceptable at low velocities. Volunteer studies demonstrate that relatively high-resolution coronary artery images can then be acquired within a single breath-hold with segmented three-dimensional true-FISP imaging using data asymmetry in the readout direction. CONCLUSION: Asymmetric sampling is a useful modification to true-FISP for reducing the off-resonance artifacts and improving imaging speed when the flow velocities are small. Copyright 2002 Wiley-Liss, Inc.
Authors: Richard M McCarthy; Vibhas S Deshpande; Nirat Beohar; Sheridan N Meyers; Steven M Shea; Jordin D Green; Xin Liu; Xiaoming Bi; F Scott Pereles; John Paul Finn; Charles J Davidson; James C Carr; Debiao Li Journal: Invest Radiol Date: 2007-10 Impact factor: 6.016
Authors: Thanh D Nguyen; Ludovic de Rochefort; Pascal Spincemaille; Matthew D Cham; Jonathan W Weinsaft; Martin R Prince; Yi Wang Journal: J Magn Reson Imaging Date: 2008-11 Impact factor: 4.813