Mesoscopic structure through the prism of transverse relaxation Zusammenfassung: In standard MR images the contrast between different tissues is primarily determined via their distinctive relaxation rates resulting from differences in the molecular dipole dipole interactions. In addition the transverse relaxation in biological tissue is influenced by the heterogeneous magnetic susceptibility of tissues on the mesoscopic scale of cells and capillaries. When exposed to a strong main field this results in heterogeneous magnetic structures that cause an additional loss of coherence of individual spin signals leading to a dephasing of the overall MR signal so called (transverse) mesoscopic relaxation. These structures are smaller than the typical MR imaging resolution achievable in humans and cannot be investigated directly. The signal acquired from a volume element is a huge average over the individual spins diffusing through the heterogeneous substructure.In this context this thesis analyzes the statistical properties of structural organization in magnetically heterogeneous media that survive the massive signal averaging and that are obtainable from the measurable MR signal. Considered is the statistical organization of magnetic susceptibility inclusions that induce a heterogeneous magnetic field on the mesoscopic scale. In such an environment the nuclear spins rotate at various different Larmor frequencies which leads to an overall frequency shift and additional dephasing the mesoscopic relaxation as introduced above of the MR signal