Analytical Characterization of RF Phase-Cycled Balanced Steady-State Free Precession

Balanced steady-state free precession (bSSFP) techniques, commonly called True-FISP, FIESTA, or balanced FFE, are rapid, efficient, high signal-to-noise ratio sequences used in angiographic, cardiac and abdominal MR imaging. One of their major drawbacks is their sensitivity to off-resonance effects arising from B(o) inhomogeneities, which can produce the familiar dark bands in the images. Radio frequency (RF) phase cycling is known to minimize this artifact. Although RF phase-cycled bSSFP is an accepted and firmly established technique, a simple and intuitive analytical signal equation has not yet been provided. Here, a complete theoretical framework is developed from which insightful characterizations such as signal uniformity, optimal flip angle, SNR efficiency, and banding effect minimization are provided. The analytical predictions and guidelines are substantiated via direct numerical simulations for clinically relevant tissues (e.g., water-like organs and lipids) using various acquisition conditions, and also verified experimentally with phantoms. We demonstrate that the banding artifact can be virtually eliminated, even for phantoms immersed in significantly nonuniform magnetic fields. (C) 2009 Wiley Periodicals, Inc. Concepts Magn Reson Part A 34A: 133-143, 2009.