Lay summary
Rapid and quantitative measurement of physiological or functional parameters of living tissue is a prerequisite for pre-clinical and clinical research as well as for clinical trials in drug research across different sites. The quantitative assessment of magnetic resonance (MR) parameters such as relaxation times or magnetization transfer effects is a very time consuming process if sources of instrumental variations have to be minimized to increase reproducibility and reliability to detect small biological changes. Although the principles and measurement strategies to assess these variables are known, we intent to explore new and unconventional MR approaches with the ultimate goal to increase imaging speed, to acquire quantitative parameter maps, and to explore and discover new contrast mechanisms.The current proposal focuses on the development and application of new steady-state free precession (SSFP) imaging methods for rapid and quantitative measurement of different tissue-specific parameters such as magnetization transfer, flow and motion, fat-water composition, and electrical conductivity. Our detailed plan of investigation consists of the following steps and projects:1. Development of SSFP-based magnetization transfer MRI methods Magnetization transfer (MT) imaging has shown great potential for the investigation of white matter diseases, particularly Multiple Sclerosis, and offers additional information about the processes of demyelination and axonal loss, inflammation, infarction, white matter edema, tumor malignancy, and ischemia. Based on our initial work MT-SSFP provides several options for further research directions and applications. Besides technical developments (rf-pulse optimizations, adaptation to different field strength) an important direction of research will focus on the possibilities to quantify magnetization transfer parameters from different SSFP acquisitions such as free/bound water pool sizes or transfer rates. Finally, we plan to analyze the impact of MT effects on quantitative T1 and T2 mapping methods.2. Development of oscillating steady state MRI methodsConventional MRI techniques are periodic, i.e. rf-pulses and gradient areas are identical from repetition to repetition. Oscillating or alternating steady state imaging is based on alternating rf-phases, internal phase evolutions, or externally applied and induced phases. These types of SSFP techniques have been used for the detection of small phase oscillations (MR elasto-graphy, alternating currents), for compensation of eddy current or motion artifacts, and for the design of frequency selective acquisitions. We aim to explore further applications of this powerful technique such as alternating current density and current-induced oscillating motion imaging in tissue and samples, imaging of flow and motion with paired or tripled SSFP acquisitions, and the design of alternating balanced SSFP sequences with modified frequency response profile for separation of fat and water or other metabolites.