Micro-machined Joule-Thomson Cryosurgical Instrument

提出的工作目标是开发一种微型机械冷冻手术仪器，该仪器利用混合气体焦耳-汤姆逊热力学循环来产生低温尖端温度。为了克服目前冷冻手术器械的局限性，该装置结合了一个微尺度主动阀和一个复合回热交换器。这项研究的最终目标是为外科医生提供一种与目前最先进的冷冻探针相比，在热性能、尺寸、灵活性和成本方面具有显著优势的冷冻探针。这里提出的技术发展将使MEMS技术，其所有固有的优势，带来承担的问题

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.