Fast Positive-Contrast Imaging of SPIO-Labeled Cells with Low-Angle Alternating-TR SSFP

Introduction: Positive-contrast imaging of super paramagnetic iron oxide (SPIO)labeled cells avoids problems associated with negative contrast such as other signal voids and partial volume effects [1-7]. Many techniques offer 2D imaging with thick slices and long scan times. A fast 3D alternating repetition time (ATR) SSFP [8] method with reliable on-resonant suppression has recently been introduced with preliminary phantom results [7]. In this work, we further analyze the signal characteristics, perform sensitivity experiments, propose a new technique to suppress fat in addition to the on-resonant signals, and present in vivo results.