光纖型式與應變規型式椎間核壓力感測器 之開發與比較

Abstract

目的：使用應變規以及光纖研發出價格便宜、製程簡單、高壓力量測範圍之微型針式感測器以應用於椎間核壓力量測。 背景：椎間核壓力是評估脊椎植入物、骨釘、修復椎間核酵素的一項重要參數，量測椎間核壓力需使用壓力感測器對椎間盤作破壞性的穿刺，所以感測器的尺寸越小對於穿刺過程中的傷害會越少，如此椎間核的水分才不會外溢。傳統量測椎間核壓力是以應變規感測器為主，但受限於應變規尺寸使感測器無法再縮小，現有的光纖感測器可達到最小侵入性傷害以實現醫學上所謂的微創，但其價格過於昂貴且耐久度和穩定度還有待驗證。 材料與方法：將20號針頭放電加工一小孔，並將應變規平貼於小孔內，再以熱熔膠塗佈應變規表面，並加熱使其均勻分布，最後將製成之應變規感測器接上應變規訊號處理器取得訊號。利用微距控制平台將單模步階光纖固定於25號針頭內，將熱熔膠滴附於光纖尾端，並使用烤盤讓熱熔膠形成珠狀結構，最後將製成之光纖感測器接上光功率計解調。校正方面，將感測器鎖入液壓校正系統並使用材料測試機施力來校正，感測器校正之訊號會與工業用感測器之標準訊號比較。驗證方面，豬胸椎試樣被解剖成一運動單元，上方以材料測試機施力，下方置放荷重元讀取力量，用引針在椎間環創造出傷口，再將感測器導入量測椎間核壓力。 結果：本研究成功將應變規感測器尺寸縮小至20號針頭，壓力測量範圍至1.6 MPa，具有高準確度、高靈敏度、高重複性；本研究提出一種能量型的光纖感測解調理論並加以實現，此光纖感測器以單模步階光纖和25號針頭整合，具有高靈敏度，但在遲滯性和非線性度有待改進。此光纖感測系統為能量解調，相較於波長解調及相位解調，能大幅地降低實驗架設成本。

Objective: To develop low-cost, easy-to-made, high-pressure miniature intradiscal pressure transducers using optic fibers and strain gages. Summary of Background Data: Intradiscal pressure (IDP) is an import mechanical index for the evaluation of spinal function. The method to measure the IDP is to introduce a pressure sensor into the nucleus pulposus. The damage due to the insertion of sensor decreased with smaller dimension of the sensor. The strain gage type transducer is frequently used to measure, but its dimension is relatively large, and may induce the interference to the measurement. The size of fiber optic type transducer can be very small, but the stability and repeatability of this type of transducer is still not reliable. Material and Method: The intensity-based fiber optic transducer system is composed of pressure transducer, power meter and coupler. The fiber optic transducer is made of single mode optic fiber, 25 G needle, and ethylene-vinyl acetate copolymer. The stain gage type transducer is composed of pressure transducer, Wheatstone bridge circuit and signal amplify. The strain gage transducer is made of strain gage, 20 G needle, and ethylene-vinyl acetate copolymer. The transducers are calibrated by a home-made calibration system, which is composed of a hydraulic chamber connected with a tested transducer, a standard transducer, and a driving pump. The pressure limit of this calibration system is 1.6 MPa. After calibration, a porcine disc specimen is used to test the maneuver and feasibility of these transducers. Conclusion: This study successfully minimizes the dimension of strain gage type transducer to 20 G needle with high accuracy, precision and sensitivity. This study also showed a new type of fiber optic transducer and integrated it into a 25G needle. Nevertheless, the hysteresis and repeatability of this type of transducer made it less practical for the in vivo or in vitro experiments.