Accelerated MPIO-Labeled Cell Imaging in the Heart

INTRODUCTION Super-paramagnetic iron oxide (SPIO) particles can label macrophages and monocytes in circulation; the effects of these labeled cells can then be detected by T2*-weighted MRI [1]. This has enormous potential for imaging inflammatory responses in the heart, but it has been difficult to do in vivo using conventional methods for free-breathing, ungated imaging. Subspace imaging with temporal navigation and sparse sampling of (k, t)-space has previously been used to accelerate several cardiac imaging applications [2], conventionally alternating between acquiring navigator data and sparse data every other TR. Here we describe a more efficient self-navigated pulse sequence to acquire both navigator and sparse data in the space of a single TR, doubling imaging speed to approach 100 frames per second (fps). We show the feasibility of using the resulting method to assess myocardial inflammation in a pre-clinical rodent ischemic re-perfusion injury (IRI) model using micron-sized paramagnetic iron oxide (MPIO) particles to label immune cells in circulation.