Graduate School of Engineering, Tokai University, Kanagawa, Japan.
Magn Reson Med Sci. 2011;10(3):177-83. doi: 10.2463/mrms.10.177.
We examined the temperature dependence of relaxation times in proton components of fatty acids in various samples in vitro at 11 tesla as a standard calibration data for quantitative temperature imaging of fat. The spin-lattice relaxation time, T(1), of both the methylene (CH(2)) chain and terminal methyl (CH(3)) was linearly related to temperature (r>0.98, P<0.001) in samples of animal fat. The temperature coefficients for the 2 primary proton components differed significantly; in 5 bovine fat samples, the coefficient at 30 °C was 1.79±0.07 (%/°C) for methylene and 2.98±0.38 (%/°C) for methyl. Numerical simulations based on such a difference demonstrated the possibility of considerable error from inconsistent ratios in fatty acid components when calibrating and estimating temperature. The error reached 3.3 °C per 15 °C in temperature elevation when we used a pure CH(2) signal for calibration and observed the signal with 18% of CH(3) to estimate temperature. These findings suggested that separating the fatty acid components would significantly improve accuracy in quantitative thermometry for fat. Use of the T(1) of CH(2) seems promising in terms of reliability and reproducibility in measuring temperature of fat.
我们在 11 特斯拉的标准校准数据下，体外研究了不同样本中脂肪酸质子成分弛豫时间随温度的变化，以便对脂肪进行定量温度成像。动物脂肪样本中，亚甲基（CH(2)）链和末端甲基（CH(3)）的自旋晶格弛豫时间 T(1)与温度呈线性关系（r>0.98，P<0.001）。2 个主要质子成分的温度系数有显著差异；在 5 个牛脂样本中，30°C 时亚甲基的温度系数为 1.79±0.07（%/°C），甲基的温度系数为 2.98±0.38（%/°C）。基于这种差异的数值模拟表明，在进行校准和估计温度时，如果脂肪酸成分的比例不一致，可能会导致相当大的误差。当我们使用纯 CH(2)信号进行校准，并用 18%的 CH(3)观察信号来估计温度时，温度升高 15°C 时误差达到 3.3°C。这些发现表明，分离脂肪酸成分将显著提高脂肪定量测温的准确性。从可靠性和可重复性方面来看，使用 CH(2)的 T(1)似乎很有前途，可以测量脂肪的温度。
