Department of Medical Physics and Engineering, Division of Medical Technology and Science, Faculty of Health Science, Graduate School of Medicine, Osaka University, 1-7 Yamadaoka, Suita, Osaka 565-0871, Japan.
Magn Reson Imaging. 2013 Dec;31(10):1744-51. doi: 10.1016/j.mri.2013.08.005. Epub 2013 Oct 2.
The purpose of this study was to develop a simple and inexpensive system for controlling body temperature in small animal experiments using magnetic resonance imaging (MRI) and to investigate the effect of body temperature on the kinetic behavior of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) in the liver. In our temperature-control system, body temperature was controlled using a feedback-regulated heated or cooled air flow generated by two Futon dryers. The switches of the two Futon dryers were controlled using a digital temperature controller, in which the rectal temperature of a mouse measured by an optical fiber thermometer was used as the input. In experimental studies, male ICR mice aged 8weeks old were used and allocated into 5 groups (39-, 36-, 33-, 30-, and 27-degree groups, n=10), in which the body temperature was maintained at 39 °C, 36 °C, 33 °C, 30 °C, and 27 °C, respectively, using our system. The dynamic contrast-enhanced MRI (DCE-MRI) data were acquired with an MRI system for animal experiments equipped with a 1.5-Tesla permanent magnet, for approximately 43min, after the injection of Gd-EOB-DTPA into the tail vein. After correction of the image shift due to the temperature-dependent drift of the Larmor frequency using the gradient-based image registration method with robust estimation of displacement parameters, the kinetic behavior of Gd-EOB-DTPA was analyzed using an empirical mathematical model. With the use of this approach, the upper limit of the relative enhancement (A), the rates of contrast uptake (α) and washout (β), the parameter related to the slope of early uptake (q), the area under the curve (AUC), the maximum relative enhancement (REmax), the time to REmax (Tmax), and the elimination half-life of the contrast agent (T1/2) were calculated. The body temperature of mice could be controlled well by use of our system. Although there were no significant differences in α, AUC, and q among groups, there were significant differences in A, REmax, β, Tmax, and T1/2, indicating that body temperature significantly affects the kinetic behavior of Gd-EOB-DTPA in the liver. In conclusion, our system will be useful for controlling body temperature in small animal experiments using MRI. Because body temperature significantly affects the kinetic behavior of Gd-EOB-DTPA in the liver, the control of body temperature is essential and should be carefully considered when performing DCE-MRI studies in small animal experiments.
本研究旨在开发一种简单且经济的磁共振成像（MRI）小动物实验体温控制系统，并探讨体温对钆塞酸二钠（Gd-EOB-DTPA）在肝脏中的动力学行为的影响。在我们的体温控制系统中，使用 Futon 干燥器产生的反馈调节加热或冷却气流来控制体温。使用数字温度控制器控制两个 Futon 干燥器的开关，其中使用光纤温度计测量的小鼠直肠温度作为输入。在实验研究中，使用 8 周龄雄性 ICR 小鼠，并将其分为 5 组（39°C、36°C、33°C、30°C 和 27°C 组，n=10），分别使用我们的系统将体温维持在 39°C、36°C、33°C、30°C 和 27°C。在尾静脉注射 Gd-EOB-DTPA 后，使用配备 1.5T 永磁体的动物实验 MRI 系统采集约 43min 的动态对比增强 MRI（DCE-MRI）数据。使用基于梯度的图像配准方法，对由于拉莫尔频率随温度漂移引起的图像位移进行校正，并用稳健位移参数估计法校正，然后使用经验数学模型分析 Gd-EOB-DTPA 的动力学行为。通过该方法，计算相对增强（A）上限、对比剂摄取率（α）和洗脱率（β）、与早期摄取斜率相关的参数（q）、曲线下面积（AUC）、最大相对增强（REmax）、最大相对增强时间（Tmax）和对比剂消除半衰期（T1/2）。使用我们的系统可以很好地控制小鼠的体温。尽管各组间的α、AUC 和 q 无显著差异，但 A、REmax、β、Tmax 和 T1/2 存在显著差异，表明体温显著影响 Gd-EOB-DTPA 在肝脏中的动力学行为。总之，我们的系统将有助于使用 MRI 控制小动物实验中的体温。因为体温显著影响 Gd-EOB-DTPA 在肝脏中的动力学行为，所以在小动物实验的 DCE-MRI 研究中，控制体温至关重要，应谨慎考虑。
