Oh Tong In, Lee Jeehyun, Seo Jin Keun, Kim Sung Wan, Woo Eung Je
College of Electronics and Information, Kyung Hee University, Korea.
Physiol Meas. 2007 Jul;28(7):S71-84. doi: 10.1088/0967-3334/28/7/S06. Epub 2007 Jun 26.
We describe a new multi-frequency technique for breast cancer detection. Applying a constant voltage with multiple sinusoidal frequencies between a reference electrode on a distal part of a patient and a scan probe placed on the breast, we measure exit currents from an array of electrodes inside the probe that are kept at the ground potential. The distribution of measured exit currents is called the trans-admittance map and the instrument is called the trans-admittance scanner (TAS). We assume a three-dimensional homogeneous domain including an internal lesion with a complex conductivity different from that of the background. Mathematically analyzing the multi-frequency trans-admittance map obtained on the surface of the domain, we found that both conductivity and permittivity ratios between the background and the lesion are crucial in extracting any useful information about the lesion from the map. Choosing two frequencies in the range of 10 Hz to 500 kHz with one significantly lower than the other and assuming that conductivity values of the background and the lesion do not change much from the low to high frequency, the lesion underneath the probe can be detected only when the conductivity ratio between the background and the lesion is different from the permittivity ratio between the background and the lesion at the chosen high frequency. Results of numerical simulations and saline phantom experiments using a developed TAS system are well matched with the mathematical analysis. The biggest advantage of this multi-frequency technique is that we do not need separately measured reference data in the absence of any lesion. We suggest future studies of a more sophisticated lesion detection algorithm based on the analysis and findings described in this paper.
我们描述了一种用于乳腺癌检测的新型多频技术。在患者远端的一个参考电极与放置在乳房上的扫描探头之间施加具有多个正弦频率的恒定电压，我们测量探头内部保持在地电位的电极阵列的出射电流。所测量的出射电流分布称为跨导纳图，该仪器称为跨导纳扫描仪（TAS）。我们假设一个三维均匀域，其中包括一个内部病变，其复电导率与背景不同。通过对在该域表面获得的多频跨导纳图进行数学分析，我们发现背景与病变之间的电导率和介电常数之比对于从该图中提取有关病变的任何有用信息至关重要。在10 Hz至500 kHz范围内选择两个频率，其中一个频率明显低于另一个频率，并假设从低频到高频背景和病变的电导率值变化不大，只有当背景与病变之间的电导率比与所选高频下背景与病变之间的介电常数比不同时，才能检测到探头下方的病变。使用开发的TAS系统进行的数值模拟和盐水体模实验结果与数学分析结果非常吻合。这种多频技术的最大优点是在不存在任何病变的情况下我们不需要单独测量参考数据。我们建议基于本文所述的分析和发现，对更复杂的病变检测算法进行未来研究。
