Mulkern R V, Wong S T, Jakab P, Bleier A R, Sandor T, Jolesz F A
Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts 02115.
Magn Reson Med. 1990 Oct;16(1):67-79. doi: 10.1002/mrm.1910160108.
Two-dimensional Fourier transform Carr-Purcell-Meiboom-Gill (CPMG) imaging sequences were implemented on 1.9-T and 1.5-T imaging systems in order to test their ability to characterize in vivo transverse decay curves (TDCs). Both hard- and soft-pulse CPMG imaging sequences, consisting of up to 128 echoes with echo spacings of approximately 10 ms were developed, implemented, and tested. These sequences provide one of the most detailed samplings of TDCs from image data sets reported to date. Good agreement between image-extracted T2 values and spectroscopically obtained T2 values of NiCl2-doped saline solutions was found with both hard- and soft-pulse sequences. In vivo TDCs were extracted from rabbit and human image data sets. For several tissues, biexponential TDC fits provided considerable improvement over monoexponential fits and the sensitivity of the fitting parameters to positive baseline offsets was examined. With the time coverage of the relaxation decay curves available from these sequences, the TDCs from white matter in humans appear largely monoexponential while those from cortical grey matter demonstrate biexponential behavior.
为了测试二维傅里叶变换Carr-Purcell-Meiboom-Gill（CPMG）成像序列表征体内横向衰减曲线（TDC）的能力，在1.9-T和1.5-T成像系统上实施了该序列。开发、实施并测试了硬脉冲和软脉冲CPMG成像序列，其包含多达128个回波，回波间隔约为10 ms。这些序列提供了迄今为止从图像数据集中对TDC最详细的采样之一。硬脉冲和软脉冲序列在从图像提取的T2值与光谱法获得的NiCl2掺杂盐溶液的T2值之间均发现了良好的一致性。从兔子和人类图像数据集中提取了体内TDC。对于几种组织，双指数TDC拟合比单指数拟合有显著改进，并研究了拟合参数对正基线偏移的敏感性。利用这些序列可获得的弛豫衰减曲线的时间覆盖范围，人类白质的TDC在很大程度上表现为单指数，而皮质灰质的TDC表现为双指数行为。
