Development and Characterization of New Test Materials with Adjustable Relaxation and Diffusion Properties for Magnetic Resonance Imaging

Abstract

Reference materials for phantoms are becoming increasingly important with the growing role of quantitative magnetic resonance imaging (MRI). By measuring specific tissue parameters such as relaxation times, diffusion, fat fraction, etc., quantitative MRI allows detailed characterization of tissue properties and is of great importance in the diagnosis and monitoring of many diseases, including tumors, stroke, multiple sclerosis, and hepatic steatosis. The development of new imaging sequences requires thorough validation and testing. Appropriate validation mechanisms are critical to ensure that the proposed technique provides reproducible and, most importantly, accurate quantitative measurements. This is where test materials, or phantoms, play a crucial role: These are specially designed test objects containing materials with stable and well-defined MR properties, such as relaxation times (T1, T2) or the apparent diffusion coefficient (ADC). They provide controlled conditions with known reference values, reproducibility, and the absence of biological variability, making them ideal for rapidly testing and optimizing new imaging techniques. The composition and production of such materials have therefore become an important area of research. This thesis focuses on the development and characterization of test materials for quantitative MRI, with particular emphasis on materials for fat-water quantification, diffusion-weighted imaging, and relaxometry at 3 Tesla. The research culminated in four peer-reviewed publications and addressed critical challenges in the design of test materials, including temporal stability, spectral purity, non-toxicity, biomimetic properties, and the ability to independently adjust multiple MR parameters within a single material.