近年來生物組織阻抗的量測已經成為生物醫學或臨床研究中相當重要的工具，由於目前導電率量測大部分透過電極以接觸式的方式量測，在量測導電率時，電極與皮膚表面接觸之間存在著許多可能影響量測數值的因素，為了降低阻抗量測的誤差，發展非接觸的阻抗影像是迫切且必要的。本論文提出一以非接觸式阻抗影像量測系統的設計方法，本系統主要包含了差動線圈、二維掃描平台、鎖頻放大器，以及人機控制介面。差動線圈包含了傳輸線圈與接收線圈，傳輸線圈產生主磁場在待測物物體內部感應產生渦電流，阻抗影像利用二維的移動平台控制感應線圈在掃描待測物表面渦電流所產生的磁場，將訊號透過資料擷取卡傳送到電腦，並且將量測的阻抗資料以二維影像的方式重建。在本論文的實驗中，吾人分別檢驗阻抗影像量測系統的性能，其中包含了，影響空間解析度與訊號雜訊比的各種變數，並且實際量測生物組織以及假體的阻抗影像，實驗的結果不但驗證了系統的性能，可以作為未來進一步提升系統靈敏度的重要依據。雖然本論文提出非接觸式阻抗影像可以得到生物組織的阻抗影像，不過仍然有許多缺點可作為未來努力的目標，例如線圈的微小化，掃描平台的設計，陣列線圈感測器等，當阻抗影像的空間解析度與靈敏度都提升後，許多臨床應用都可以進一步被開發出來。 In recent years, the bio-impedance measurement has become an emerging tool for biomedical research and medical practice. The conductivity of biologic tissue is usually accessed by electrodes attached on the object. There are many measurement errors which could rise in interface between electrodes and object. In order to reduce the contact error, it is necessary to develop a contactless impedance measurement. In this paper, we proposed an impedance image modality providing the conductivity distribution within the object. The measurement system includes differential coil, 2D scanning platform, lock-in amplifier, and graphical user interface. The transmittal coil produces a primary magnetic field and results in an eddy current in the object. The received coil picks up the secondary magnetic field resulting from the eddy current. The measured information is collected by the data acquiring card and performed by the two-dimensional image. From the experimental results, we have examined several variables affecting the performance of image quality, such as spatial resolution, signal to noise ratio. The conductivity distribution of biologic tissue and phantoms can be obtained successfully by the proposed imaging method. The experimental results not only provide the feasibility in contactless impedance image, but also provide an improvement in the future. In this work, there still exist many drawbacks to overcome. We hope to minimize the size of differential coil to improve the spatial resolution. The 2D scanning platform can be upgraded to a 3D platform. The sensor array can speed up the time cost of image reconstruction. Finally, many clinic applications can be developed based on the contactless impedance image.
