多重光電倍增管校正模組設計製作及其於擴散光學斷層造影系統之應用;Design and Fabrication of Multiple-PMT Calibration Module and Its Application in Diffuse Optical Imaging Systems

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题名:	多重光電倍增管校正模組設計製作及其於擴散光學斷層造影系統之應用;Design and Fabrication of Multiple-PMT Calibration Module and Its Application in Diffuse Optical Imaging Systems
作者:	石珮君;Shih, Pei-Jyun
贡献者:	機械工程學系
关键词:	PMT控制電壓校正;頻域式量測系統;仿乳假體驗證;擴散光學斷層造影;PMT control voltage calibration;frequency domain measurement system;breast-mimicking phantom;diffuse optical tomography imaging
日期:	2017-03-22
上传时间:	2017-05-05 17:42:42 (UTC+8)
出版者:	國立中央大學
摘要:	近年來，乳癌為台灣女性癌症發生率之首，故早期發現及治療為重要議題。在醫療檢測技術上，近紅外光擴散光學斷層造影技術 (Near-infrared Diffuse optical tomography imaging system, NIR DOT)為功能性的醫學檢測裝置，因為乳房組織的散射係數相對於近紅外光波段較大，故光源穿透組織後所得到微弱的光訊號，則須採用高靈敏度的光偵測器接收，在藉由擴散方程式進行影像重建，以判別組織的變異狀況。然而，光學檢測設備中會因光偵測器長時間作業造成特性變異，使量測結果產生偏差，故需對光偵測器進行特性量測。本研究主要對光偵測器特性進行校正模組化，設計簡易可拆式近紅外光源模組，並採用高靈敏度的光電倍增管 (Photomultiplier tube, PMT)進行量測，以暗箱機構及馬達電控方式來設計校正裝置，不僅可抑制環境光對PMT之干擾，亦可快速且精準地進行特性量測。根據PMT經由模組量測獲得的特性曲線，為了善用PMT不同控制電壓的有效量測範圍，將各個控制電壓可容許輸入的光功率範圍歸納成一套PMT光功率適用範圍指標。另外，於頻域式量測系統下，獲得PMT各個於不同控制電壓下的相位差關係，將其應用於頻域式光學量測技術之相位補償校正。本研究所設計之實驗中，藉由直徑60mm仿乳房光學係數仿體，以環形擴散光學斷層造影量測機制，其採用3個PMT同時進行量測，將量測的電訊號分別代入是否經由模組之光電校正式，以進行仿體光學特徵驗證。基於本研究設計的光電校正模組，建立光偵測器訊號擷取平台及校正程序，可精確且快速的取得光電倍增管之特性曲線，進而應用於臥床式擴散光學斷層造影系統，提高系統量測結果之準確性。 ;In recent years, breast cancer has the highest incidence rate happens in Taiwanese female, so early detection and treatment become an important issue. In medical screening technology, NIR DOT is a functional medical detection device, which is mainly based on the near infrared light source to penetrate the breast physiological tissue. Because the scattering coefficient of breast tissue is large regarding the near-infrared light band, the weak optical signal is received using high sensitivity detector after the light passes through the tissue and the variation of the tissue can be reconstructed using the diffusion equation. However, due to the long time work, the optical detection equipment will cause the characteristics of variation and the biases of the measurement results. Thus, it is necessary to measure the characteristics of the photo-detectors. The main propose of this study is to calibrate the characteristics of the photo-detector, design the simple and detachable near-infrared light source modules and use the high sensitivity photomultiplier tube (PMT) to measure. Using the dark space mechanism and automatic control with motor to design the correction device not only can inhibit the ambient light interference to the PMT but also can measure the characterization fast and accurately. According to the characteristic curve obtained by the PMT measurement, to make the use of the effective measurement range in different PMT control voltage, the optical power range of each control voltage are induced to a set of PMT optical power index bar. Besides, under the frequency domain measurement system, the phase difference relationship of PMT under different control voltage can be obtained, which is applied to the phase compensation correction of frequency domain optical measurement technology. In this study, the phantom with 60 mm diameter which is trying to imitate the optical coefficient from human breast will be measured by three PMTs at the same time in the ring-diffused shaped optical tomography system, then the measured electrical signal will be taken into photoelectric conversion equation for the verification of characterization. Based on the photoelectric correction module designed in this study, the signal acquisition platform and calibration program of the photo-detector are established, which can obtain the characteristic curve of the photomultiplier tube accurately and quickly. Furthermore, the method is applied to the bed-type diffuse optical tomography system to improve the accuracy of the system measurement results.
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