FRODO pulse sequences: a new means of eliminating motion, flow, and wraparound artifacts.

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Abstract
Magnetic resonance images of the spine, chest, abdomen, and pelvis are commonly degraded by ghost artifacts. The authors have developed a new technique named FRODO (Flow and Respiratory artifact Obliteration with Directed Orthogonal pulses) to suppress these artifacts. Signal from tissues responsible for the artifacts is eliminated by use of radio frequency pulses specifically optimized for high selectivity to saturate proton magnetization over one or more independently defined slabs (large rectangular volumes) of tissue. Ghost artifacts from pulsatile flow in the heart and blood vessels, as well as from respiratory motion and swallowing, are suppressed. Additional applications of this technique include elimination of intraluminal signal in blood vessels and suppression of wrap-around artifact along the phase-encoding axis. Preliminary clinical experience suggests that the FRODO technique, in conjunction with other flow compensation methods, may provide a definitive solution to the problem of motion in spine imaging. FRODO pulse sequences may also prove useful for imaging of blood vessels, heart, abdomen, and other areas where motion, flow, or wraparound artifacts limit image quality.