Development of a phantom compatible for MRI and hyperthermia equivalent to relaxation times and dielectric properties of the human tissues

我们开发了一种与磁共振成像和热疗兼容的体模，其松弛时间和介电性能相当于人体组织。模型由0~140NaCl3、0~1.6%琼脂糖、0~0.7%μ、3%卡拉胶和0.03%NaN3组成，其余为水。该体模在1.5T时的T1值为202~1,904ms，T2值为38~423ms，电导率为0.27~1.26MHZ/m，相对介电常数在5~130 MHz范围内为78.1~98.9。所研制的体模具有以下特点：1)含有卡拉胶作为固化剂，并允许其在不使用物理增强的情况下用于制造躯干体模。2)通过改变作为TV改性剂的GdCl3和作为T2改性剂的琼脂糖的浓度，可以独立地改变体模的T1和T2弛豫时间。3)模型的导电性可以通过改变NaCl4)来改变。4)当加入NaN_3作为防腐剂时，模型在较长的时间内保持化学和物理上的稳定。5)当制作具有所需松弛时间和导电性的特定模型时，可以从根据实验数据推导出的经验公式中确定合适的GdCl3、琼脂和氯化钠的浓度。因此，所开发的模型可用于MRI和热疗的基础研究、MRI设备的QA、并对核磁共振操作员和放射科医生进行培训。

We developed a phantom compatible for MRI and hyperthermia equivalent to relaxation times and dielectric properties of the human tissues. The phantom consists of 0 -140 μmol/kg GdCl_3, 0 -1.6 % agarose, 0 -0.7 % NaCl, 3 % carrageenan and 0.03 % NaN_3, with water as the remainder. The phantom has a T1 value of 202 to 1,904 ms and a T2 value of 38 to 423 ms at 1.5 T, and has conductivity of 0.27 to 1.26 S/m and relative permittivity of 78.1 to 98.9 for the frequency range of 5 -130 MHz.The phantom developed has the following characteristics;1) The phantom contains carrageenan as a solidifying agent, and allows its use in producing a torso phantom without the use of physical reinforcements.2) T1 and T2 relaxation times of the phantom are independently changeable by varying the concentrations of GdCl_3 as Tv modifier and agarose as T2 modifier. Thus, the range of the T1 and T2 relaxation times of the phantom can be adjusted to correspond to those of all human tissues.3) Conductivity of the phantom is changeable by changing the concentration of NaCl.4) As NaN_3 is admixed as a preservative, the phantom remains chemically and physically stable over extended periods.5) The appropriate concentrations of GdCl_3, agarose and NaCl can be determined from the empirical formulae which are deduced from the experimental data, when making a specified phantom that has the required relaxation times and conductivity.Thus, the phantom developed is useful for basic studies of MRI and hyperthermia, QA of MRI equipment, and training MRI operators and radiologists.