Edd Jon F, Rubinsky Boris
Department of Mechanical Engineering, University of California, Berkeley, CA 94720, USA.
Physiol Meas. 2006 May;27(5):S175-85. doi: 10.1088/0967-3334/27/5/S15. Epub 2006 Apr 20.
Imaging has made cryosurgery, the destruction of unwanted tissue through freezing, valuable. Electrical impedance tomography (EIT) has been explored as a method to determine the volume of tissue that is frozen during the procedure. However, studies have shown that tissue near the edge of the frozen zone often survives since in this region it may only be the extra-cellular space that is frozen. This threatens the usefulness of cryosurgery for cancer therapy since inaccurate ablation either allows the cancer to survive or increases the chances of complications. Since low-frequency conductivity of tissue increases due to cell membrane impairment, and ablated tissue implies impaired membranes, EIT has the capability to recover images of tissue viability. Cryosurgery is a technique that can benefit from this: EIT scans before freezing and after thawing can show changes in conductivity and hence viability due to treatment. Assuming unfrozen tissue will survive treatment, we explore the use of differential EIT in combination with intra-operative ice front imaging modes that are currently in clinical practice to recover enhanced-resolution images of cryosurgical treatment efficacy in a set of simulated experiments. We also investigate the sensitivity to violation of this assumption and predict tolerable levels of measurement noise.
成像技术使冷冻手术变得有价值，冷冻手术是通过冷冻来破坏不需要的组织。电阻抗断层成像（EIT）已被探索作为一种确定手术过程中被冷冻组织体积的方法。然而，研究表明，冷冻区边缘附近的组织通常能够存活，因为在这个区域可能只有细胞外空间被冷冻。这威胁到冷冻手术在癌症治疗中的有效性，因为不准确的消融要么使癌细胞存活，要么增加并发症的几率。由于细胞膜受损会导致组织的低频电导率增加，而消融组织意味着细胞膜受损，EIT有能力恢复组织活力的图像。冷冻手术就是一项能从中受益的技术：冷冻前和解冻后的EIT扫描可以显示由于治疗导致的电导率变化，进而显示活力变化。假设未冷冻的组织能够在治疗中存活，我们在一组模拟实验中探索将差分EIT与目前临床实践中使用的术中冰前沿成像模式相结合，以恢复冷冻手术治疗效果的高分辨率图像。我们还研究了违反这一假设的敏感性，并预测了可容忍的测量噪声水平。
