Spin-echo SS-PARSE: a PARSE MRI method to estimate frequency, R₂ and R₂^′ in a single shot

Abstract 

Spin-echo signals allow separate measurements of irreversible and reversible relaxation rates in MRI. A spin-echo version of single-shot parameter assessment by retrieval from signal encoding (SE-SS-PARSE) method has been developed to quantitatively and accurately map transverse magnetization magnitude, frequency, irreversible and reversible relaxation rates in a single shot. These image parameters can be applied to fMRI research as well as a number of neuroimaging applications. Following a description of the signal model, this article demonstrates the performance of SE-SS-PARSE in simulations with different noise levels and in phantom experiments. By solving an inverse problem, the estimated irreversible and reversible relaxation rates in SE-SS-PARSE are highly correlated with the reference relaxation rates from a standard technique (correlation coefficients: r¹=0.9636 for reversible relaxation rate, r²=0.9788 for irreversible relaxation rate). The rapid SE-SS-PARSE technique has the potential to monitor transient changes in R₂ and R₂^′ while minimizing motion artifacts and also is free of geometric and ghosting errors. It is expected that this fast scan technique will find applications in both scientific research and clinical diagnosis.

Keywords: Single-shot MRI, Spin echo, Transverse relaxation rate, Rapid MRI