# Advances in compact magnetic resonance : devices, methodologies, and investigations

• Fortschritte in der Kompakt Magnetischen Resonanz : Geräte, Methoden, und Messungen

Magnetic Resonance Imaging (MRI) and Magnetic Resonance Spectroscopy (MRS) are the most developed and commonly known facets of Magnetic Resonance (MR). This work explores compact MR strategies so that new directions for MRI and MRS may arise in the future. This thesis is divided into three parts, namely, Devices, Methodologies, and Investigations. Ten relaxometry devices are developed in Part I. Three devices are single sided while seven are closed sensors. Single sided sensors include the worlds smallest single sided sensor the S$^4$~MOUSE comparable to the old generation NMR-MOUSE but over 126 times smaller. Other single sided sensors include the $^{23}$Na NMR-MOUSE and the next generation Fourier NMR-MOUSE. Closed magnets include the worlds smallest $0.6$~cm$^3$ NMR probe that includes the magnets, noise shielding, the NMR coil, and the sample tube. Other prominent closed sensors include $1.6$~cm$^3$ 1 T NMR probe including magnets and a palm-top $^2$H sensor. New geometries are developed with different shimming strategies to achieve relaxometry, one of the strategies is now a patent. Part II of this work deals with simulation of 1D NMR signal based on stretched exponential approach and also implements a 2D correlation method `CPMG SWIET' to measure $D$-$T_2$ maps suitable for low SNR conditions. This part ends with a chapter on future methods, procedures, and strategies to move towards spectroscopy and elucidates a geometry with imaging-level homogeneity without prior shimming. Simulations of a 10 Tesla pineapple-sized magnet and 2D polarized magnet assemblies, and an idea of moving magnets to homogenize the field, among others, are key future directions for compact NMR. Part III deals with investigations performed using the NMR-MOUSE and its comparison with competitive techniques such as THz imaging and evanescent field dielectrometry.