Quantitative sodium imaging with a flexible twisted projection pulse sequence.
The quantification of sodium MR images from an arbitrary intensity scale into a bioscale fosters image interpretation in terms of the spatially resolved biochemical process of sodium ion homeostasis. A methodology for quantifying tissue sodium concentration using a flexible twisted projection imaging sequence is proposed that allows for optimization of tradeoffs between readout time, signal-to-noise ratio efficiency, and sensitivity to static field susceptibility artifacts. The gradient amplitude supported by the slew rate at each k-space radius regularizes the readout gradient waveform design to avoid slew rate violation. Static field inhomogeneity artifacts are corrected using a frequency-segmented conjugate phase reconstruction approach, with field maps obtained quickly from coregistered proton imaging. High-quality quantitative sodium images have been achieved in phantom and volunteer studies with real isotropic spatial resolution of 7.5 x 7.5 x 7.5 mm(3) for the slow T(2) component in approximately 8 min on a clinical 3-T scanner. After correcting for coil sensitivity inhomogeneity and water fraction, the tissue sodium concentration in gray matter and white matter was measured to be 36.6 +/- 0.6 micromol/g wet weight and 27.6 +/- 1.2 micromol/g wet weight, respectively.
Lu
Aiming
A
Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, Illinois 60612, USA. aiminglu@uic.edu
Atkinson
Ian C
IC
Claiborne
Theodore C
TC
Damen
Frederick C
FC
Thulborn
Keith R
KR
D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000145:classification; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D011859:Radiography; D012015:Reference Standards; D015203:Reproducibility of Results; D012964:Sodium
D012964:Sodium