Fast radio-frequency enforced steady state (FRESS) spin echo MRI for quantitative T 2 mapping: Minimizing the apparent repetition time (TR) dependence for fast T 2 measurement

Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA.
NMR in Biomedicine (Impact Factor: 3.04). 02/2012; 25(2):189-94. DOI: 10.1002/nbm.1729
Source: PubMed


Transverse relaxation time (T(2)) is a basic but very informative MRI parameter, widely used in imaging to examine a host of diseases, including multiple sclerosis, stroke, and tumor. However, short repetition time (TR) is often used to minimize scan time, which may introduce non-negligible errors in T(2) measurement. Specifically, due to the use of refocusing pulse, the steady state magnetization depends not only on TR but also on the TE. Hence, if the TE dependence is not properly accounted for, it may be mistaken as T(2)-induced signal attenuation, leading to non-negligible T(2) underestimation. Our study proposed a fast radio-frequency enforced steady state (FRESS) spin echo (SE) MRI sequence, which saturates the magnetization after the echo and ensures a TE-independent steady state. The proposed FRESS-SE MRI was evaluated with numerical simulation, implemented with echo planar imaging readout, and validated by both phantom and in vivo experiments. In summary, FRESS-SE T(2) MRI technique was developed for fast and accurate T(2) imaging, suitable for in vivo applications.

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