Nakagami分佈是用於估計描述組織超音波逆散射訊號之統計性質的有效方法。不同的估算器可能會影響Nakagami參數在檢測逆散射訊號統計的預測差異。通常最大似然估算器（MLE）是用於估計逆散射訊號之Nakagami參數的主要方法。本研究調查了八個估算器對Nakagami參數估計預測之性能和可靠性。本研究將使用電腦模擬和假體實驗產生超音波逆散射訊號。試驗中的四個變量(散射子濃度、假體大小、對數壓縮和雜訊影響)將是影響實驗中兩個評估(性能評估和可靠性評估)的條件。性能評估包括執行時間、參數差異和相對標準差(RSD)，可靠性評估包括柯爾莫諾夫-斯米爾諾夫檢驗（KS檢驗）、決定係數和p值。藉由使用八個估算器來估計超音波逆訊號之Nakagami參數並進行評估。實驗表明Cheng-Beaulieu (CB)估算器和Greenwood-Durand (GD)估算器與其他估算器相比允許更可靠的Nakagami參數估算。在假體寬度3倍脈衝長度時，CB估算器和GD估算器執行時間為63.2μs而MLE執行時間為CB和GD估算器之2020倍。在假體寬度3倍脈衝長度且散射子濃度128 scatterers/mm^2時，CB估算器擁有最小KS-test值0.0191而GD估算器之KS-test值為0.0202。模擬實驗中，所需的假體大小之寬度和對數壓縮動態範圍被建議為7倍脈衝長度和8位元動態範圍。在假體驗證實驗中，估計器之間的差異與模擬實驗相同，假體大小之寬度和對數壓縮動態範圍被建議為3倍脈衝長度和8位元動態範圍。因此，建議將CB估算器和GD估算器作為用於改進基於Nakagami分布對超音波組織特徵表現方法之估算器。

The Nakagami distribution is a valuable tool to estimate the statistics of ultrasound backscattered signals for tissue description. Different estimators may impact the prediction of Nakagami-m parameter in the detection of difference in backscattered statistics. In general, maximum likelihood estimator (MLE) is the principal method applicate to estimate the Nakagami parameters of ultrasound signals. This study investigate the performance and reliability of eight estimators on Nakagami parameter estimations. Ultrasound backscattered signals were generated using a simulation model, and phantom experiments. Four variables, scatterer concentration, phantom size, logarithmic compression and noise effect, will be the conditions of experiment and two assessments, performance assessment and reliability assessment, will be performed by ultrasound backscattered signals. Performance assessment includes execution time, Nakagami-m parameter difference and relative standard deviation (RSD), and reliability assessment includes Kolmogorov–Smirnov test (KS test), R-squared and p-value. Ultrasound signals were utilized to estimate the Nakagami-m parameters by using eight estimators for comparisons. The experiment demonstrated that Cheng-Beaulieu estimator (m_CB) and Greenwood-Durand estimator (m_GD) allowed more trustworthy Nakagami-m estimations compared with other estimators.m_CB and m_GD execute estimation for 63.2 μs and the execution time of MLE estimation is 2020 times m_CB and m_GD’s execution time while window width is 3 times pulse length. m_CB has the least KS-test value as 0.0191 and m_GD has KS-test value as 0.0202 while window width is 3 times pulse length and concentration is 128 scatterers/mm^2. In addition, the required phantom area’s width of the envelope signal and dynamic range of logarithmic compression are suggested as 7 times pulse length and 8-bits. In phantom verification experiment, the difference between estimators are same as in simulation experiment and the required phantom area’s width of the envelope signal and dynamic range of logarithmic compression are suggested as 3 times pulse length and 8-bits. Therefore, m_CB and m_GD are suggested as estimators for the improvement of Nakagami-based methodologies for ultrasound tissue characterization.

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