Methodical developments for preclinical stem cell tracking on a clinical 3 Tesla MRI

In resent years, MRI as a non-invasive radiation free modality of diagnostic imaging became an irreplaceable versatile technique for preclinical animal research. Dedicated animal MR systems do exist, but the broad availability of clinical MRI facilities and the cost-effectiveness of a combined clinical and preclinical use in conjunction with the high costs for dedicated animal systems make preclinical research on clinical MRI hardware very attractive. Central to the present work are methodical developments of MR techniques able to visualize and assess the pathway of superparamagnetic iron oxide (SPIO) labeled functional stem cells in vivo. Aims followed by this thesis focus on an enhanced specity and sensitivity of the produced cellular contrast and on robust scanning schemes facilitating artifact free sub-millimeter resolution images on clinical large bore systems. In this context it is demonstrated that 3D radial imaging trajectories are beneficial in the sense of reduced motional artifacts and desired background signal properties for detecting single iron oxide labeled cells in small mammals. Other techniques developed in this work employ the dipolar eld pattern of iron oxide labeled stem cells in order to change the initially dark hypointense contrast of cells into a positive contrast which is better dierentiable from heterogeneous tissue structures. Best results are obtained by emploing this cellular magnetic footprint combined with high-resolution 3D radial imaging. A dedicated image reconstruction of the acquired datasets is able to gain positive contrast of single cells in vivo.