TY - JOUR
T1 - Point spread functions of the T2 decay in k-space trajectories with long echo train
AU - Qin, Qin
N1 - Funding Information:
This work was supported, in part, by a grant from the National Center for Research Resources, a component of the National Institutes of Health. Drs. James Pekar and Peter van Zijl are thanked for helpful discussions. Mary McAllister is acknowledged for her editorial assistance. The constructive critics and helpful suggestions from reviewers are deeply appreciated.
Funding Information:
Grant support from: NIH P41 EB015909.
PY - 2012/10
Y1 - 2012/10
N2 - T2 decay during long echo trains of magnetic resonance (MR) imaging pulse sequences is known to cause a blurring effect, due to the peak broadening of the point spread function (PSF). In contrast, the simultaneous amplitude-loss effect, led by the peak reduction of the PSF, has gained much less attention. In this report, we analyzed the PSFs of both the truncation and T2 decay for Cartesian (linear profile ordering and low-high ordering) and spiral trajectories, respectively. Then, we derived simple formulas to characterize both the blurring and amplitude-loss effects, which are functions of the ratios of the echo train duration (Tk) over T2 (Tk/T2). Signal-to-noise ratio (SNR) per unit time was thus analyzed considering both the amplitude-loss effect induced by the T2 decay and the SNR gain from the long acquisition duration based on MR sampling theory. Optimum Tk/T2 ratios to achieve maximum SNR per unit time were 1.2 for the Cartesian trajectory and 0.8 for the spiral trajectory.
AB - T2 decay during long echo trains of magnetic resonance (MR) imaging pulse sequences is known to cause a blurring effect, due to the peak broadening of the point spread function (PSF). In contrast, the simultaneous amplitude-loss effect, led by the peak reduction of the PSF, has gained much less attention. In this report, we analyzed the PSFs of both the truncation and T2 decay for Cartesian (linear profile ordering and low-high ordering) and spiral trajectories, respectively. Then, we derived simple formulas to characterize both the blurring and amplitude-loss effects, which are functions of the ratios of the echo train duration (Tk) over T2 (Tk/T2). Signal-to-noise ratio (SNR) per unit time was thus analyzed considering both the amplitude-loss effect induced by the T2 decay and the SNR gain from the long acquisition duration based on MR sampling theory. Optimum Tk/T2 ratios to achieve maximum SNR per unit time were 1.2 for the Cartesian trajectory and 0.8 for the spiral trajectory.
KW - Cartesian
KW - K-space trajectory
KW - Point spread function
KW - SNR per unit time
KW - Spiral
KW - T decay
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U2 - 10.1016/j.mri.2012.04.017
DO - 10.1016/j.mri.2012.04.017
M3 - Article
C2 - 22817958
AN - SCOPUS:84866182509
VL - 30
SP - 1134
EP - 1142
JO - Magnetic Resonance Imaging
JF - Magnetic Resonance Imaging
SN - 0730-725X
IS - 8
ER -