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首页> 外文学位 >Cryosurgical monitoring using visible light imaging and electrical impedance tomography: A feasibility study.
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Cryosurgical monitoring using visible light imaging and electrical impedance tomography: A feasibility study.

机译：使用可见光成像和电阻抗断层摄影术进行冷冻手术监测：一项可行性研究。

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摘要

Cryosurgery, which uses low temperatures to destroy unwanted tissue, relies heavily on medical imaging to monitor the freezing process. While existing imaging techniques are adequate in some cases, many procedures would benefit from alternative monitoring methods. Two promising techniques that have not been previously assessed for cryosurgical use are optical imaging (OI) and electrical impedance tomography (EIT). OI images are based on differences in visible radiation attenuation, while EIT images are maps of electrical impedance distribution. The act of freezing tissue increases both its optical attenuation and electrical impedance. In this dissertation, we evaluate the feasibility of using OI and EIT to monitor cryosurgical procedures.; In order to test whether frozen tissue provides sufficient optical contrast for OI, we designed an experimental chamber capable of measuring transmitted and reflected visible light through an MRI-monitored bulk tissue sample undergoing one-dimensional planar freezing. We found that the increased scattering of the frozen region attenuated the optical signal in both reflection and transmission modes. The results of a diffusion-based finite difference model analogous to the experimental system compared favorably to our experimental data.; A similar approach was used to test whether frozen tissue provides adequate electrical impedance contrast for EIT. A small planar tissue sample within an impedance measurement chamber was one-dimensionally frozen using a directional freezing stage. The highly insulative frozen region produced easily discernible impedance changes as the ice front moved across the sample. Results produced by a finite element model of our sample chamber compared well to all measured samples.; In the final study, we developed an image reconstruction algorithm appropriate for cryosurgery. This boundary element-based method adjusts the geometry of the imaged frozen region rather than the impedances of the individual pixels, as is the case with traditional finite element-based algorithms. This Front-Tracking (FT) method takes advantage of the fact that frozen regions in cryosurgery are generally simply shaped, convex, have known origins, and are of known resistivity. Simulations based on identical phantoms revealed that our FT algorithm requires fewer independent voltage measurements, achieves finer edge resolution, and is computationally more efficient than traditional EIT reconstruction algorithms.
机译：使用低温破坏有害组织的冷冻手术在很大程度上依赖医学成像来监测冷冻过程。尽管在某些情况下现有的成像技术已足够，但许多程序将从替代的监测方法中受益。以前尚未评估过用于冷冻手术的两种有前途的技术是光学成像（OI）和电阻抗断层扫描（EIT）。 OI图像基于可见辐射衰减的差异，而EIT图像是电阻抗分布图。冻结组织的行为会增加其光学衰减和电阻抗。在本文中，我们评估了使用OI和EIT监测冷冻手术过程的可行性。为了测试冷冻的组织是否可为OI提供足够的光学对比度，我们设计了一个实验室，该室能够测量通过MRI监测的大体积组织样本的透射和反射可见光，该样本进行一维平面冷冻。我们发现，在反射和透射模式下，冻结区域散射的增加都会使光信号衰减。与实验系统类似的基于扩散的有限差分模型的结果优于我们的实验数据。使用类似的方法来测试冷冻组织是否为EIT提供足够的电阻抗对比。使用定向冷冻台将阻抗测量室内的一小块平面组织样本一维冷冻。当冰锋横穿样品时，高度绝缘的冻结区域会产生易于识别的阻抗变化。由我们样品室的有限元模型产生的结果与所有测量样品进行了很好的比较。在最终研究中，我们开发了一种适用于冷冻手术的图像重建算法。这种基于边界元素的方法可以调整成像冻结区域的几何形状，而不是调整单个像素的阻抗，就像传统的基于有限元素的算法一样。这种前跟踪（FT）方法利用了以下事实：冷冻手术中的冷冻区域通常简单地成形，凸出，具有已知的起源并且具有已知的电阻率。基于相同模型的仿真显示，我们的FT算法需要较少的独立电压测量，可以实现更好的边缘分辨率，并且比传统的EIT重建算法在计算效率上更高。

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  • 作者

    Otten, David Michael.;

  • 作者单位

    University of California, Berkeley.;

  • 授予单位 University of California, Berkeley.;
  • 学科 Engineering Biomedical.
  • 学位 Ph.D.
  • 年度 2000
  • 页码 193 p.
  • 总页数 193
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 生物医学工程;
  • 关键词

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