Controlled freezing of nonideal solutions with application to cryosurgical processes.
Controlled freezing of nonideal solutions with application to cryosurgical processes.
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应用于冷冻手术过程中的非理想溶液的受控冷冻。
DOI：
10.1115/1.2895423
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
A. Shitzer
中科院分区：
文献类型：
--
作者：
H. Budman;J. Dayan;A. Shitzer
冷冻手术的成功，即最大限度地破坏细胞，要求在冷冻过程中控制冷却速度。标准的冷冻手术设备通常不是为执行所需的控制过程而设计的。在本研究中，开发了一种新的冷冻装置，通过精确控制探针温度随时间的变化，可以在冷冻过程中实现指定的冷却速率。这种新装置已经在土豆泥的水溶液中进行了实验测试。测量了与生物组织热特性相似的冷冻介质中的温度场。冷冻探针的温度被控制在一个期望的时变剖面上，这被认为是最大限度地坏死。研究了闭环控制系统的跟踪精度和稳定性。结果发现，在大多数情况下，跟踪精度很好，测得的探针温度与期望的设定值之间的误差在+/- 0.4℃以内。然而，由于过冷现象或由于冷冻探针中液氮沸腾状态的不稳定，与设定值发生了明显的偏差。将实验结果与有限元程序计算结果进行了比较，结果吻合较好。两个数据集之间的偏差似乎主要是由于热电偶结在介质中的定位错误。
Success of a cryosurgical procedure, i.e., maximal cell destruction, requires that the cooling rate be controlled during the freezing process. Standard cryosurgical devices are not usually designed to perform the required controlled process. In this study, a new cryosurgical device was developed which facilitates the achievement of a specified cooling rate during freezing by accurately controlling the probe temperature variation with time. The new device has been experimentally tested by applying it to an aqueous solution of mashed potatoes. The temperature field in the freezing medium, whose thermal properties are similar to those of biological tissue, was measured. The cryoprobe temperature was controlled according to a desired time varying profile which was assumed to maximize necrosis. The tracking accuracy and the stability of the closed loop control system were investigated. It was found that for most of the time the tracking accuracy was excellent and the error between the measured probe temperature and the desired set point is within +/- 0.4 degrees C. However, noticeable deviations from the set point occurred due to the supercooling phenomenon or due to the instability of the liquid nitrogen boiling regime in the cryoprobe. The experimental results were compared to those obtained by a finite elements program and very good agreement was obtained. The deviation between the two data sets seems to be mainly due to errors in positioning of the thermocouple junctions in the medium.