Tofts P S, Shuter B, Pope J M
Institute of Neurology, London, United Kingdom.
Magn Reson Imaging. 1993;11(1):125-33. doi: 10.1016/0730-725x(93)90420-i.
In order to study the relationship between the concentration of Gd-DTPA in tissue, and the resulting changes in relaxation times and signal intensity, a phantom material that has similar relaxation times to tissue and that can be doped with Gd-DTPA is required. The "tissue-equivalent" material should not contain Gd; nor should it alter the relaxivities of Gd-DTPA from their values in aqueous solution (R1 = 4.5 sec-1 mM-1; R2 = 5.5 sec-1 mM-1 at 1.5 T). Conventional materials, based on CuSO4-, MnCl2-, or GdCl3/LaCl3-agarose mixtures, are not suitable, since Gd is displaced from the Gd-DTPA chelate. The new material, consisting of Ni-DTPA dissolved in agarose, is easy to prepare and does not interact with Gd-DTPA. Its relaxation times are stable; relaxivity R1 was within 4% of its aqueous value over 109 days. T1s have low dependence on temperature (0.2-1.0%/degrees C at 21 degrees C) and on field strength, allowing the material to be used as a relaxation time standard for quality assurance. Equations giving the concentration of Ni-DTPA and agarose to produce a required T1 and T2 are provided.
为了研究组织中钆喷酸葡胺（Gd-DTPA）的浓度与弛豫时间和信号强度变化之间的关系，需要一种具有与组织相似弛豫时间且可掺杂Gd-DTPA的体模材料。这种“组织等效”材料不应含有钆，也不应改变Gd-DTPA在水溶液中的弛豫率（在1.5T时，纵向弛豫率R1 = 4.5秒-1毫摩尔-1；横向弛豫率R2 = 5.5秒-1毫摩尔-1）。基于硫酸铜、氯化锰或氯化钆/氯化镧-琼脂糖混合物的传统材料不合适，因为钆会从Gd-DTPA螯合物中被置换出来。由溶解在琼脂糖中的镍-二乙三胺五乙酸（Ni-DTPA）组成的新材料易于制备，且不与Gd-DTPA相互作用。其弛豫时间稳定；在109天内，弛豫率R1在其水溶液值的4%以内。纵向弛豫时间（T1）对温度（21℃时为0.2 - 1.0%/℃）和场强的依赖性较低，这使得该材料可作为质量保证的弛豫时间标准。文中还提供了给出产生所需T1和T2的Ni-DTPA和琼脂糖浓度的方程式。
