Development of non-invasive temperature measurement system for continuous monitoring of deep brain temperatures

已有研究表明，新生儿缺氧缺血后降温可减少损伤，改善功能结局。然而，临床试验目前受到非侵入性测量大脑温度的困难的阻碍。微波辐射测量是静冈大学提出并发展的一种非侵入性脑温度测量技术。辐射计系统通过放置在头部表面的波导天线检测来自大脑内部的非常微弱的自发电磁辐射，并用中心频率1.2、1.65、2.3、3.0和3.6 GHz的五个接收器放大这些辐射。该系统还包括两个锁定放大器、控制电路、参考噪声源和温度恢复算法，在原有的1.2 GHz和1.65 GHz接收机的基础上增加了2.3 GHz、3.0 GHz和3.6 GHz接收机，并开发了整个系统的控制程序。除了这些，还有几个…制造了更多的电路，如缓冲电路、恒压/电流电路、电源电路等。为了不在屏蔽室中而在正常环境中稳定地工作，对系统采取了几种降低背景噪声和热波动的对策。经过这些改进，系统在正常的房间里变得稳定，并且可以使用波导天线进行校准实验。五个接收器的温度分辨率分别为0.183、0.273、0.148、0.108、0.118℃。还从婴儿的MRI数据中获得了新的放射加权函数。利用获得的分辨率和婴儿头部的温度形状函数，利用温度恢复模拟方法估计了大脑中心的可信区间，该方法也是为评估该系统而开发的。由此获得的间隔约为0.3℃。这一结果与1℃的目标值相比是令人满意的。目前正在进行婴儿头部温度分布模型的制作和温度测量实验系统稳定性的进一步对策研究。较少

It has been shown that cooling the brain of newborn baby after hypoxia-ischemia can reduce damage and improve functional outcome. Clinical trials are, however, currently hindered by the difficulty in measuring brain temperature non-invasively. Microwave radiometry has been proposed and developed as a non-invasive technique for brain temperature measurement at Shizuoka University. The radiometer system detects the very weak spontaneous electromagnetic radiation from inside the brain by a waveguide antenna placed on the head surface and amplifies them with five receivers operating at center frequencies of 1.2, 1.65, 2.3, 3.0 and 3.6 GHz. The system also includes two lock-in amplifiers, control circuit, reference noise source, and the temperature retrieval algorithm.Among the five receivers, 2.3, 3.0 and 3.6 GHz receivers have been added to the 1.2 and 1.65 GHz receivers that were previously made, and a control program for the whole system has been developed. In addition to those, several … More circuits such as buffer circuits, constant voltage/current circuits, supply circuits, etc. were manufactured. In order to operate stably not in a shielded room but in a normal room, several countermeasures for reducing background noises and thermal fluctuation have been made to the system. After such improvements, the system became stable in a normal room, and a calibration experiment could be done using a waveguide antenna. Temperature resolutions for the five receivers were 0.183, 0.273, 0.148, 0.108, 0.118 ℃. New radiometric weighting functions were also obtained from baby's MRI data. Confidence interval at the brain center was estimated by the temperature retrieval simulation method, which also developed for the evaluation of the system, using the obtained resolutions and a temperature shape function in a baby's head. The interval thus obtained was about 0.3 ℃. This result was satisfactory in comparison with the target value of 1 ℃. Manufacturing the temperature distribution phantom of a baby's head and the further countermeasures for stabilization of the system for temperature measurement experiment are now underway. Less