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Breath-hold three-dimensional true-FISP imaging of coronary arteries using asymmetric sampling
Vibhas S Deshpande1, Steven M Shea, Yiu Cho Chung
1Department of Radiology, Northwestern University, Chicago, Illinois, USA.
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.