Boada F E, Christensen J D, Huang-Hellinger F R, Reese T G, Thulborn K R
Massachusetts General Hospital NMR Center, Charlestown.
Magn Reson Med. 1994 Aug;32(2):219-23. doi: 10.1002/mrm.1910320210.
The biexponential relaxation behavior of the sodium nucleus affects the accuracy of quantitative measurement of in vivo tissue sodium concentration (TSC). Theoretical analysis and in vivo experimental results are used to demonstrate the extent of the large bias in the measured TSC that arises when the relaxation behavior in vivo differs significantly from that of the calibration standards which is when a significant fraction of the total sodium signal decays with a relaxation time much shorter than the echo time (TE) used for imaging. This bias can be as large as 20% for measurements of TSC in a normal rat brain with TE = 2 ms. Our findings indicate that shortening the echo time (TE < 0.5 ms) by projection imaging is a reliable means of obtaining accurate in vivo estimates for TSC using MR.
钠原子核的双指数弛豫行为会影响体内组织钠浓度（TSC）定量测量的准确性。理论分析和体内实验结果被用于证明，当体内弛豫行为与校准标准的弛豫行为显著不同时，即当总钠信号的很大一部分以比用于成像的回波时间（TE）短得多的弛豫时间衰减时，测量得到的TSC会出现多大程度的大偏差。对于TE = 2 ms的正常大鼠脑内TSC测量，这种偏差可能高达20%。我们的研究结果表明，通过投影成像缩短回波时间（TE < 0.5 ms）是使用磁共振成像获得准确的体内TSC估计值的可靠方法。
