Rewcastle J C, Hahn L J, Saliken J C, McKinnon J G
Department of Diagnostic Imaging, Foothills Hospital, Calgary, Alberta, Canada.
J Surg Oncol. 1997 Oct;66(2):110-3. doi: 10.1002/(sici)1096-9098(199710)66:2<110::aid-jso7>3.0.co;2-g.
During liver cryosurgical procedures, the authors observed seriously inconsistent rates of iceball growth implying inconsistent probe cooling rates. This inconsistency can lead to several problems, most importantly, loss of precision and reliability in freezing the chosen volume of tissue. The observation led to investigation of the performance of the cryosurgery machine.
The performance of the Cryotech LCS 3000 with different moratorium periods was investigated. Freezing was performed in a gelatin phantom with thermocouple monitoring at the probe tip.
It was determined that a moratorium period between unit filling and clinical use essentially eliminates the uncertainty in probe performance. The need for this arises from the design of the system. A full liquid nitrogen tank does not have the necessary pressure required to induce effective freezing. A partially filled tank increases vapor pressure in the storage dewar driving more liquid nitrogen through the probes, thus allowing a more reliable and faster freeze.
The simple measure of introducing a moratorium period between filling the dewar with liquid nitrogen and its use in surgery allows partial evaporation of the nitrogen and enhances cryoprobe performance. This protocol modification may reduce the chance of inconsistent probe performance thus making liver cryosurgery more reliable.
在肝脏冷冻手术过程中，作者观察到冰球生长速率严重不一致，这意味着探头冷却速率不一致。这种不一致会导致几个问题，最重要的是，在冷冻选定体积的组织时会失去精度和可靠性。这一观察结果促使对冷冻手术设备的性能进行研究。
研究了不同暂停期的Cryotech LCS 3000的性能。在装有热电偶的明胶模型中进行冷冻，热电偶在探头尖端进行监测。
确定在设备填充和临床使用之间设置一个暂停期基本上可以消除探头性能的不确定性。这是由系统设计所导致的需求。满液氮罐没有诱导有效冷冻所需的必要压力。部分填充的罐会增加储存杜瓦瓶中的蒸气压，驱使更多液氮通过探头，从而实现更可靠、更快的冷冻。
在向杜瓦瓶中填充液氮与将其用于手术之间引入一个暂停期这一简单措施，能使液氮部分蒸发并提高冷冻探头的性能。这种方案修改可能会减少探头性能不一致的可能性，从而使肝脏冷冻手术更可靠。
