使用超音波逆散射訊號統計模型於骨質疏鬆症之臨床偵測

Using Statistical Models for Ultrasonic Backscattering to Clinically Assess Osteoporosis

黃智宏(Chih-Hong Huang)

指導教授 ： 王士豪

中原大學/工學院/醫學工程研究所/碩士(2003年)

https://doi.org/10.6840/cycu200300760

摘要

目前偵測骨質疏鬆症的方法以雙能量X光吸收量測法(DEXA)、定量化電腦斷層掃描(QCT)、定量化超音波(QUS)最常被採用，然而DEXA與QCT具游離輻射危險及價格高昂之缺點，QUS雖無游離輻射之虞，但其量測結果無法排除脂肪或其他軟組織之影響。本研究嘗試使用超音波逆散射訊號Nakagami統計參數偵測骨骼微結構狀態，以評估骨質疏鬆症程度，本方法除可排除脂肪或其他軟組織對結果之影響外，尚有價格低廉及無游離輻射風險之優點。

本研究包含軟體模擬、假體實驗、與臨床實驗三部分。軟體模擬與假體實驗顯示散射子濃度增加時，Nakagami參數值會隨之非線性增加並趨近於1。散射區間長度小於10mm會使統計參數值不穩定。臨床實驗使用1MHz超音波換能器量測人體脛骨與跟骨，定義四個正規化統計參數來嘗試定量評估骨質疏鬆症程度。結果顯示此四個參數與髖關節骨密度值之相關係數達0.66~0.70，雖較DEXA不同部位量測結果之相關係數低(0.72)，但高於DEXA與BUA之相關性(0.58)，研究證實此四參數可應用於臨床評估骨質疏鬆症程度。

為進一步方便於臨床測量，本研究也研製一套可攜式的超音波量測系統，其功能包括超音波訊號之激發與接收、濾波、訊號放大、數位化與資料傳輸。此系統可放大訊號達35.6dB，數位化解析度為12位元，取樣頻率為65MHz。經由假體測試結果顯示本系統與過去使用之量測系統的結果相關性達0.99，本系統將進一步用於臨床研究。

關鍵字

散射訊號 ； Nakagami分佈 ； 骨質疏鬆

並列摘要

Osteoporosis is commonly detected using DEXA, QCT, and QUS. However, DEXA or QCT have disadvantages of radiation risk and high cost. On the other hand, QUS is an irradiational modality in which its results of measurement are affected by fat and other soft tissue. For these reasons, this study attempted to assess the degree of osteoporosis by detecting microstructures of the bone using Nakagami statistical parameters for ultrasonic backscattering signals. The influence of fat and other soft tissues could be eliminated using this method. Moreover, it has advantage of low cost and non-radiation.

This investigation included software simulations, experiments on phantoms, and the clinical experiments. Results obtained from software simulations and phantoms experiments showed that Nakagami parameter approaches to 1 associated with the increase of scatterers concentration. The parameter is unstable when the length of gated scattering is less than 10mm. In clinical experiments, A transducer of 1 MHz was used to measure human tibia and calcaneus. To better quantitatively assess the degree of osteoporosis, four normalized statistical parameters were defined. Result demonstrated that the correlation coefficients between these four parameters and BMD of hip are ranged from 0.66 to 0.70. Although these relations are less than that obtained using DEXA, these are larger than relation between DEXA and BUA. These results showed that the proposed four statistical parameters have a great potential in assessing degree of osteoporosis.

To further make a convenience in clinical measurements, the study also developed a portable ultrasound measurement system that has functions of excitation and reception for ultrasonic signals, filter, amplification, digitization, and data transfer. The maximum amplification of signals is 35.6dB. Digital signals have 12bits resolution and 65MHz sampling frequency. The phantom test by this system showed a correlation coefficient between results obtained from this system and these from previous system is 0.99. This just developed system will be further applied to clinical investigation.

並列關鍵字

scattering signals ； Nakagami distribution ； osteoporosis

參考文獻

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