Advances in Signal Processing for Relaxometry

Spin relaxation is probably the most common contrast mechanisms in MRI. Despite it being a molecular mechanism, macroscopic relaxation-weighted images provide valuable clinical information regarding tissue viability and pathological state, while also reflecting microscopic features such as architecture, exchange rates, and biochemical state. In order to tap into the plethora of information offered by spin relaxation the field of MRI is gradually adopting a quantitative approach, where the actual values of T1, T2, and T2* relaxation times are being measured, in contrast to traditional collection of relaxation-weighted images. Notwithstanding the challenges of qMRI, this approach optimally utilizes the dynamic range of each parameter, offers higher sensitivity to tissue changes, and most importantly, improves data reproducibility, and standardization. This chapter focuses on advanced techniques for quantification of relaxation times, the use of comprehensive biophysical signal models, and acceleration schemes designed to shorten qMRI scan time and facilitate its use in the clinic.