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

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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.