- 學位論文
整合頻率分集技術與Nakagami統計模型 以應用於評估骨組織特性
The application of bony tissue characterization by the Nakagami statistical model with the technique of frequency diversity and compounding.
摘要
超音波比X-Ray系統具有造價便宜、非游離性、體積小、攜帶方便等優點，現今已被應用於定量測量骨質密度，主要的測量方法為寬頻超音波衰減法與超音波聲速法。這些方法需應用兩個換能器外，所以其測量位置主要以跟骨為主，同時其測量值的誤差也很大。為此，本研究嘗試使用一個換能器量測骨組織之超音波逆散射訊號，並整合Nakagami統計模型(Nakagami statistical model)與頻率分集（frequency diversity）技術以應用於定量評估骨組織特性之可行性。 實驗的驗證是使用中心頻率1 MHz的平面式超音波換能器進行假體與臨床骨組織檢測，其中，假體實驗針對濃度分別從2到32 scatterers/ 的玻璃砂散射子假體進行五次實驗，每次實驗擷取128條A-line。臨床實驗係由130名自願者進行超音波與雙能量X-光吸收儀（Dual Energy X-ray Absorptiometry, DEXA）的量測，並計算出受測者的Nakagami參數與骨密度（bone mineral density, BMD）值。頻率分集是使用兩個FIR的帶通濾波器(頻寬0.5 MHz，中心頻率為0.75 MHz與1.25 MHz)，處理所擷取的超音波逆散射訊號，以計算出meff參數。實驗結果顯示Nakagami與meff參數能夠有效地分辨假體中散射子濃度的變化，m參數與meff參數之平均靈敏度(ΔNakagami parameter/Δscatterer number density)分別為0.006與0.049，且m參數與DEXA測出之BMD的相關係數為0.82，meff參數與DEXA測出之BMD的相關係數為0.58。本實驗結果顯示Nakagami參數能夠有效地區分假體中散射子濃度與骨質密度，未來或可被應用於發展有別於超音波衰減法、聲速法與DEXA的骨質密度測量系統。
並列摘要
Ultrasound has several advantages, such as low cost, irradiation, small size, and portable, over the X-ray system. Presently, ultrasound was applied to quantitatively measure the bone density, in which the broadband ultrasonic attenuation and ultrasonic velocity are two primary methods. These methods require the application of two transducers that further limited the measurement mainly at the calcaneus as well as led to a large measurement error. For these reasons, this study is to apply a transducer to measure ultrasonic backscattered signals from bone tissues. The integration of the Nakagami statistical model and frequency diversity technique was subsequently applied to explore its feasibility on the quantitative assessment of bone tissues. The experiment was verified with the use of a 1 MHz central frequency plane transducer to perform measurements from phantoms and clinical bone tissues. For each phantom, with scatterer concentrations varying from 2 to 32 scatterers/mm3, five measurements were carried out and that a totally of 128 A-lines of ultrasonic signals was collected for each measurement. Moreover, clinical studies, there are 130 volunteers applied to the measurements by ultrasound and dual Energy X-ray absorptiometry for the calculation of Nakagami parameters and BMDs. The two FIR bandpass filters with a bandwidth of 0.5 MHz and a central frequency of 0.75 and 1.25 MHz were used for the estimation of meff parameters obtained from frequency diversity technique. The experimental results showed that the Nakagami parameter could effectively distinguish the variation of scatterer concentration that the sensitivities of m and meff parameter were respectively 0.006 and 0.049. Furthermore, the correlation between m and BMD obtained by DEXA is high with a coefficient of 0.82. The correlation between meff and BMD is medium with a coefficient of 0.58. This study concluded that the Nakagami parameter is another approach capable of evaluating the variation of scatterer concentration in phantoms and the status of bony density.