  Magnetic Resonance cardiac diffusion tensor imaging (cDTI) and cardiac
intravoxel incoherent motion imaging enables probing of in vivo myofiber
architecture and myocardial perfusion surrogates. To study the impact of
experimental parameters such as resolution, off-resonances and heart-rate
variations, we propose a numerical open-source framework called MRXCAT-CDTI. It
allows simulating diffusion and perfusion contrast for spin-echo (SE) and
stimulated echo acquisition mode (STEAM) cDTI sequences. The Fourier encoder
supports in-plane and/or through-slice off-resonance effects, as well as T2*
effects during single-shot image encoding. Optional lesions are included to
mimic ischemic and infarcted myocardial regions. MRXCAT-CDTI allows assessing
realistic influences on data acquisition, and how these affect the data
encoding process and subsequent data processing. As an example, heart-rate
variations lead to differences in partial saturation and relaxation of
magnetization that end up in errors of 9 to 30% for cDTI angle metrics if not
accounted for. For SE echo-planar cDTI, in-plane off-resonance effects more
adversely affect cDTI metrics compared to through-slice off-resonances. With
this work we propose an open-source MRXCAT-CDTI numerical simulation framework
that offers realistic image encoding effects found in cardiac diffusion and
perfusion data to systematically study influences of data encoding,
reconstruction, and post-processing to promote reproducible research.
