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In vivo T 1ρ mapping in cartilage using 3D magnetization‐prepared angle‐modulated partitioned k ‐space spoiled gradient echo snapshots (3D MAPSS)
Author(s) -
Li Xiaojuan,
Han Eric T.,
Busse Reed F.,
Majumdar Sharmila
Publication year - 2008
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.21414
Subject(s) - flip angle , nuclear magnetic resonance , signal (programming language) , imaging phantom , gradient echo , magnetization , materials science , relaxation (psychology) , k space , signal to noise ratio (imaging) , physics , magnetic resonance imaging , optics , computer science , medicine , radiology , quantum mechanics , magnetic field , programming language
For T 1ρ quantification, a three‐dimensional (3D) acquisition is desired to obtain high‐resolution images. Current 3D methods that use steady‐state spoiled gradient‐echo (SPGR) imaging suffer from high SAR, low signal‐to‐noise ratio (SNR), and the need for retrospective correction of contaminating T 1 effects. In this study, a novel 3D acquisition scheme—magnetization‐prepared angle‐modulated partitioned‐ k ‐space SPGR snapshots (3D MAPSS)—was developed and used to obtain in vivo T 1ρ maps. Transient signal evolving towards the steady‐state were acquired in an interleaved segmented elliptical centric phase encoding order immediately after a T 1ρ magnetization preparation sequence. RF cycling was applied to eliminate the adverse impact of longitudinal relaxation on quantitative accuracy. A variable flip angle train was designed to provide a flat signal response to eliminate the filtering effect in k ‐space caused by transient signal evolution. Experiments in phantoms agreed well with results from simulation. The T 1ρ values were 42.4 ± 5.2 ms in overall cartilage of healthy volunteers. The average coefficient‐of‐variation (CV) of mean T 1ρ values ( N = 4) for overall cartilage was 1.6%, with regional CV ranging from 1.7% to 8.7%. The fitting errors using MAPSS were significantly lower ( P < 0.05) than those using sequences without RF cycling and variable flip angles. Magn Reson Med 59:298–307, 2008. © 2008 Wiley‐Liss, Inc.