TY - JOUR
T1 - Retrospective correction for T1-weighting bias in T2 values obtained with various spectroscopic spin-echo acquisition schemes
AU - Fleysher, Roman
AU - Fleysher, Lazar
AU - Kirov, Ivan
AU - Hess, David A.
AU - Liu, Songtao
AU - Gonen, Oded
N1 - Funding Information:
The authors thank Drs. Andrew A. Maudsley of The University of Miami and Brian J. Soher of Duke University for the use of their FITT spectral modeling software. This work is supported by National Institutes of Health grants number EB001015, NS050520, NS39135, NS29029 and CA111911.
PY - 2009/12
Y1 - 2009/12
N2 - Localized tissue transverse relaxation time (T2) is obtained by fitting a decaying exponential to the signals from several spin-echo experiments at different echo times (TE). Unfortunately, time constraints in magnetic resonance spectroscopy (MRS) often mandate in vivo acquisition schemes at short repetition times (TR), that is, comparable with the longitudinal relaxation constant (T1). This leads to different T1-weighting of the signals at each TE. Unaccounted for, this varying weighting causes systematic underestimation of the T2's, sometimes by as mush as 30%. In this article, we (i) analyze the phenomenon for common MRS spin-echo T2 acquisition schemes; (ii) propose a general post hoc T1-bias correction for any (TR, TE) combination; (iii) show that approximate knowledge of T1 is sufficient, since a 20% uncertainty in T1 leads to under 3% bias in T2; and consequently, (iv) efficient, precision-optimized short TR spin-echo T2 measurement protocols can be designed and used without risk of accuracy loss. Tables of correction for single-refocusing (conventional) spin-echo and double refocusing, such as, PRESS acquisitions, are provided.
AB - Localized tissue transverse relaxation time (T2) is obtained by fitting a decaying exponential to the signals from several spin-echo experiments at different echo times (TE). Unfortunately, time constraints in magnetic resonance spectroscopy (MRS) often mandate in vivo acquisition schemes at short repetition times (TR), that is, comparable with the longitudinal relaxation constant (T1). This leads to different T1-weighting of the signals at each TE. Unaccounted for, this varying weighting causes systematic underestimation of the T2's, sometimes by as mush as 30%. In this article, we (i) analyze the phenomenon for common MRS spin-echo T2 acquisition schemes; (ii) propose a general post hoc T1-bias correction for any (TR, TE) combination; (iii) show that approximate knowledge of T1 is sufficient, since a 20% uncertainty in T1 leads to under 3% bias in T2; and consequently, (iv) efficient, precision-optimized short TR spin-echo T2 measurement protocols can be designed and used without risk of accuracy loss. Tables of correction for single-refocusing (conventional) spin-echo and double refocusing, such as, PRESS acquisitions, are provided.
KW - Spin-echo
KW - T1 weighting
KW - T2 relaxation
KW - Tissue relaxation times
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U2 - 10.1016/j.mri.2009.05.033
DO - 10.1016/j.mri.2009.05.033
M3 - Article
C2 - 19559555
AN - SCOPUS:70449524408
SN - 0730-725X
VL - 27
SP - 1410
EP - 1419
JO - Magnetic Resonance Imaging
JF - Magnetic Resonance Imaging
IS - 10
ER -