Micro-machined Joule-Thomson Cryosurgical Instrument

拟议工作的目标是开发一种利用混合气体焦耳-汤姆逊热力学循环来产生低温尖端温度的微机械低温外科仪器。该装置包括一个微型主动阀和一个复合回热换热器，以克服目前限制低温外科仪器的限制。这项研究的最终目标是为外科医生提供一种在热性能、尺寸、灵活性和成本方面与当前最先进的相比具有显著优势的低温外科探头。这里提出的技术发展将使MEMS技术及其所有固有的优势能够应用于解决 冷冻治疗。低温探头将使用传统的微加工技术制造，从而产生一种可以批量制造的低成本设备。用于监测和控制温度场的仪器和加热器可以单片安装在探头上。探头结构将主要由硅和玻璃制成，因此将与磁共振成像兼容，从而实现对冷冻手术过程的实时监控。在该项目的R21阶段，我们将分别设计和制造主动阀和换热器。这些组件将进行测试，以证明它们满足 冷冻外科系统的要求。R21阶段将在系统级测试中达到顶峰 证明了热力循环的可行性和部件的可靠性。R33阶段的目标是利用这一技术基础来设计、制造和演示一种集成的微制造低温外科探头。演示探头将以符合临床使用的方式进行包装。将演示探头承受压力、热和弯曲载荷的能力，这些载荷大于使用过程中预期的载荷。低温探测器的性能将在热真空环境中进行精确测量。随后，体内测试将在明胶溶液中进行，然后在切除的动物组织中进行，以便量化与冻结区相关的时间和长度尺度。将开发和演示能够自动执行根据冻结区特征定义的手术方案的控制算法。

The objective of the proposed work is the development of a micro-machined cryosurgical instrument that utilizes a mixed-gas Joule-Thomson thermodynamic cycle to produce cryogenic tip temperatures. The device incorporates a micro-scale active valve and a composite recuperative heat exchanger in order to overcome limitations that currently limit cryosurgical instruments. The ultimate goal of this research is to provide surgeons with a cryosurgical probe that has significant advantages in terms of thermal performance, size, flexibility, and cost relative to the current state-of-the-art. The technical developments proposed here will enable MEMS technology, with all of its inherent advantages, to be brought to bear on the problem of cryosurgery. The cryoprobe wilJbe fabricated using conventional micro-fabrication techniques resulting in a low cost device that can be batch fabricated. Instrumentation and heaters to monitor and control the temperature field may be monolithically installed on the probe. The probe structure will be primarily silicon and glass and will therefore be compatible with magnetic resonance imaging, enabling real-time monitoring of cryosurgical procedures. During the R21 Phase of the project we will design and separately fabricate the active valve and recuperative heat exchanger. These components will be tested to demonstrate that they satisfy the requirements of the cryosurgical system. The R21 phase will culminate in a system level test that demonstrates the viability of the thermodynamic cycle and the reliability of the components. The goal of the R33 Phase is to utilize this technology base in order to design, fabricate, and demonstrate an integrated micro-fabricated cryosurgical probe. The demonstration probe will be packaged in a manner that is consistent with clinical usage. The ability of the probe to withstand pressure, thermal, and bending loads that are greater than those anticipated during usage will be demonstrated. The performance of the cryoprobe will be precisely measured in a thermal vacuum environment. Subsequent, in-vivo testing will occur in a gelatin solution and later in excised animal tissue in order to quantify the time and length scales associated with the freeze zone. Control algorithms that will enable automatic implementation of surgical protocols, defined in terms of freeze zone characteristics, will be developed and demonstrated.