定量式超音波(QUS)技術被廣泛應用於量化活體組織的特性，例如肌肉、骨頭或肌腱組織。QUS主要來自超音波穿過組織時所產生的聲波傳遞特性改變，包含波速(SOS)、寬頻波衰減(BUA)和結合兩者的stiffness參數(STI)；近來通常應用於骨密度的評估。而QUS影像是將BUA、SOS和STI的訊號，經掃瞄而重建成二維的影像方式表現，這樣的特徵影像更適合用於上述組織的評估。然而，大部分的商用超音波骨密度儀，通常只考慮QUS影像中特定區域或位置的量化參數。跟骨的骨密度已經被證實是非均值的，所以只量測特定的點或區域(ROI)是不客觀的量測方式。建立一套自動找尋跟骨區域來評估量化參數的方法，藉此增進評估骨密度的準確度，是一個重要的課題。另外，阿基里斯腱是人體最大也是最強壯的肌腱；一套非侵入式且客觀的評估技術也是相當重要的。近年利用QUS技術來評估肌腱組織被廣泛提出，所以我們也將利用QUS影像來評估肌腱特性，例如肌腱強度與張力。本研究目的包含 1) 整合自動找尋跟骨區域與QUS影像來建構一套系統，進而提升利用QUS來評估骨密度的準確性、 2) 使用QUS影像來量測阿基里斯腱的特性。
利用腳跟骨的QUS影像來評估骨密度時，考慮全跟骨區域的量化參數，會比只單純考慮影像中最低密度或特定區域的量化參數來的好；通常宣稱的理由是因為骨頭是非均值的材質所導致，但是因超音波通過軟組織與骨頭的相位差相消，也許是另一個因素。所以本研究首先提出利用修正輪廓變形模型(MCDM)，來自動偵測QUS影像上腳跟骨的外型。我們使用一個3D的腳跟骨假體來確認邊界偵測與相位差相消的現象。結果發現量測整體跟骨面積的量化參數，與真實的假體骨密度相關係數R高達0.99。另外，我們亦收集9名受測者來驗證。發現量測整體跟骨面積的準確誤差，比量測任何的跟骨局部區域來的小。這表示量測整體跟骨面積的量化參數來隔離跟骨的非均值與超音波相位差相消，是一種較準確的量測方式。另一方面，修正輪廓變形模型可以應用於BUA、SOS與STI的QUS影像上，並提供一準確且便利的方式來評估骨質疏鬆。
接著我們在QUS的影像上，偵測阿基里斯腱的厚度與位置，並計算其BUA與SOS的參數值。結果顯示，BUA與SOS在年輕族群(23.7±2.0歲之男性17人及女性32人)與中年族群(47.3±8.5歲之中年男女各8人)中，有統計上的差異(p<0.05)。在臨床跟骨肌腱拉長術(ATL)病患手術前後的量測中，發現患者於開刀後，阿基里斯腱厚度由4 mm增加至4.3 mm，而BUA值增加7.2%，SOS值減少0.6%。這樣的結果顯示，肌腱壓力上升會導致BUA降低與SOS升高。然而，至今仍無文獻清楚的討論BUA與SOS的參數與肌腱機械特性的相關性；為了明瞭BUA與SOS相對於肌腱組織在人體內的改變，我們設計了一個定量式超音波與應變量測的肌腱測試系統，用來評估離體豬腱的特性。結果顯示，波衰減會隨著肌腱兩端的拉伸而降低，SOS則會隨著肌腱兩端的拉伸而升高；這些結果都與ATL手術病患所得到的結論相同。。
最後結果顯示BUA和SOS兩種量化參數，確實具有量化阿基里斯腱的潛力。在比較厚度的量測上，超音波的厚度量測與面積在線性回歸分析中，具有高度相關性(R2 = 0.73)；也證實使用超音波來量測非均勻的軟組織厚度，具有較客觀的結果。雖然使用QUS影像來量化肌腱仍有許多困難及問題有待克服解決，不過本研究亦證明QUS具有以非侵入的方式來評估人體阿基里斯腱的潛力；期望未來能提供實際的臨床應用。

Quantitative ultrasound (QUS) technique has been widely applied on the characterization of living tissues, such as muscle, bone and tendon. Currently QUS has been applied for evaluation of bone mineral density (BMD) by measuring wave propagating properties on bone, such as speed of sound (SOS), broadband ultrasound attenuation (BUA) or combination of above two parameters called stiffness index (STI). QUS image is reconstructed by 2D scanning of BUA and SOS, and STI is very informative for analysis of living tissues. However, most commercial ultrasonic devices only measure the parameters from a single point or a specific region of interest (ROI). It was demonstrated that the heel bone density is not uniform, so it is not objective to only observe a specific point or region. To design an automatic method for detecting heel bone region to improve the accuracy of measurement by QUS images is an important issue. On the other hand, Achilles tendon is the largest and strongest tendon of human body. An objectively non-invasive measurement for evaluating Achilles tendon is also important. Recently, noninvasive QUS technique has been widely used to evaluate tendon properties. Therefore, we used noninvasive QUS technique for evaluating the tendon properties like strength and stress. The main objectives of this study were 1) to develop an integrated system by an automatic method to detect heel bone region to improve the accuracy of measurement of bone properties by QUS images, and 2) to investigate the properties of Achilles tendons using QUS images.
Evaluation of SOS or BUA using QUS parameters based on the whole calcaneus bone has been shown to have better performance than a smaller circular ROI selected from a point with minimum density. Although it was claimed that inhomogeneity of the bone might be the main factor in causing such a difference, phase cancellation caused by an ultrasound wave passing through soft tissue and bone could be a factor to this difference. First, a modified contour deformable model (MCDM) was proposed to automatically detect the calcaneus contour from QUS images. A three-dimensional calcaneus phantom was used for the validation of MCDM and the effect of phase cancellation. The correlation between the parametric values evaluated from the whole calcaneus contour and BMD was very high, with a correlation coefficient of R = 0.99. Additionally, 9 subjects were recruited for clinical tests in this study. The precision errors of the measured ultrasonic parameters using whole calcaneal region were smaller than partial circular region (p<0.05). This indicated that calculating quantitative parameters using total calcaneal region provided a more accurate measurement for preventing the defects caused by bone inhomogeneity and ultrasound phase cancellation. On the other hand, the MCDM model could provide more accurate and convenient measurement for evaluating osteoporosis with BUA, SOS and STI of QUS images.
Secondly, we detected the position and thickness of Achilles tendon from the QUS images and calculated the parameters of BUA and SOS. It was found that BUA and SOS were significantly different between the younger group (32 females and 17 males; mean age: 23.7 ± 2.0) and the older group (8 female and 8 males; mean age: 47.3 ± 8.5 s) (p<0.05). One of the participants underwent an Achilles tendon lengthening (ATL), the thickness of Achilles tendon increased from 4 mm to 4.33 mm after the operation. In addition, after the operation for stress release, BUA show an increase of 7.2% but the SOS with a decrease of 0.6%. These results imply that high stress load might decrease BUA and increase SOS, respectively. However, it was not a major concern for BUA and SOS used to evaluate the properties of tendons. In order to understand the changes of BUA and SOS of the patient with pre and post ATL surgery, we designed a measurement system which can provide the information of BUA and SOS of porcine tendon at different loading. The results show that the ultrasonic attenuation decreases and SOS increases while the stress increasing.
In summary, this study indicates that the BUA and SOS are potential candidate parameters of ultrasonic tools to evaluate the properties of Achilles tendon. Comparing the thickness measurement, the regression of the thickness evaluated by ultrasonic technique and the cross-sectional area was statistically significant. The thickness evaluated by ultrasonic technique is considered as independent variable and cross-sectional area is as dependent variable (R2 = 0.73). This indicates the thickness evaluated by ultrasonic technique is an overall measurement because all area penetrated by ultrasonic waves was considered. Consequently, it would be greatly helpful for calculating QUS parameters, and for analyzing non-uniform soft tissues. Utilizing QUS images for evaluating the property of human’s Achilles tendon had highly potential for clinical application.

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