St Pierre Timothy G, Clark Paul R, Chua-Anusorn Wanida
School of Physics, M013, The University of Western Australia, Crawley, WA 6009, Australia.
NMR Biomed. 2004 Nov;17(7):446-58. doi: 10.1002/nbm.905.
A single-spin-echo methodology is described for the measurement and imaging of proton transverse relaxation rates (R2) in iron-loaded and normal human liver tissue in vivo. The methodology brings together previously reported techniques dealing with (i) the changes in gain between each spin-echo acquisition, (ii) signal level offset due to background noise, (iii) estimation of signal intensities in decay curves at time zero to enable reliable extraction of relaxation times from tissues with very short T2 values, (iv) bi-exponential modelling of decay curves with a small number of data points, and (v) reduction of respiratory motion artefacts. The accuracy of the technique is tested on aqueous manganese chloride solutions yielding a relaxivity of 74.1+/-0.3 s-1 (mM)-1, consistent with previous reports. The precision of the in vivo measurement of mean liver R2 values is tested through duplicate measurements on 10 human subjects with mean liver R2 values ranging from 26 to 220 s-1. The random uncertainty on the measurement of mean liver R2 was found to be 7.7%.
本文描述了一种单自旋回波方法，用于在体测量和成像铁负荷的和正常人体肝脏组织中的质子横向弛豫率（R2）。该方法整合了先前报道的技术，这些技术涉及：（i）每次自旋回波采集之间增益的变化；（ii）背景噪声导致的信号电平偏移；（iii）估计时间为零时衰减曲线中的信号强度，以便能够从具有非常短T2值的组织中可靠地提取弛豫时间；（iv）用少量数据点对衰减曲线进行双指数建模；以及（v）减少呼吸运动伪影。该技术的准确性在氯化锰水溶液上进行了测试，其弛豫率为74.1±0.3 s-1（mM）-1，与先前报道一致。通过对10名平均肝脏R2值范围为26至220 s-1的人类受试者进行重复测量，测试了体内平均肝脏R2值测量的精度。发现平均肝脏R2测量的随机不确定度为7.7%。
