Estimation of Backscatter Coefficients Using an In Situ Calibration Source.
Estimation of Backscatter Coefficients Using an In Situ Calibration Source.
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使用原位校准源估计反向散射系数。
DOI：
10.1109/tuffc.2019.2944305
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Oelze,MichaelL
中科院分区：
文献类型：
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作者：
Nguyen,TrongN;Tam,AlexJ;Do,MinhN;Oelze,MichaelL
本文的目的是论证利用现场校准源估计后向散射系数(BSC)的可行性。使用参考体模技术估计活体中的BSC的传统方法没有考虑由于超声源和要询问的组织区域之间的介入层而引起的传输损失，从而导致基于BSC的估计的偏差和方差增加。为了考虑传输损耗，提出了一种现场校准方法。原位校准技术采用了超声表征良好、生物相容的钛球，并嵌入到样品中。进行了一系列实验，以评估镶嵌的钛球作为原位校准目标的BSC估计。第一个实验量化了直径为0.5 mm、1 mm和2 mm三种尺寸的钛球的背向散射信号强度。第二组实验评估了钛球的BSC估计的重复性，并将这些BSC与理论进行了比较。第三组实验量化了钛珠在样品顶部存在损耗层的情况下提供原位参考光谱的能力。最后一组实验量化了珠子在样品中多个深度上提供校准光谱的能力。所有实验均使用连接到SonixOne系统的L9-4/38线性阵列进行。从2 mm的钛珠子上观察到的信号最强，相对于背景散斑的信噪比(SNR)为11.6分贝。在2.5-5.5 MHz的分析带宽下，利用阵列和单元件换能器，实验得到的BSCs和由Faran理论得到的BSCs之间的平均差异分别为0.54和0.76分贝。用无层和有层的原位校准方法和有层的参考体模方法估计的BSC与没有层的参考体模方法进行了比较。BSCs的平均差值分别为0.15、0.73和-9.69分贝。从位于实际珠深度以上或以下30个脉冲长度的深度的数据块计算的BSC与在珠深度计算的BSC的平均差异分别为-1.55和-1.48分贝。结果表明，原位校准目标可以解释覆盖的组织损失，从而提高了基于BSC的估计的稳健性。
The objective of this article is to demonstrate the feasibility of estimating the backscatter coefficient (BSC) using an in situ calibration source. Traditional methods of estimating the BSC in vivo using a reference phantom technique do not account for transmission losses due to intervening layers between the ultrasonic source and the tissue region to be interrogated, leading to increases in bias and variance of BSC-based estimates. To account for transmission losses, an in situ calibration approach is proposed. The in situ calibration technique employs a titanium sphere that is well-characterized ultrasonically, biocompatible, and embedded inside the sample. A set of experiments was conducted to evaluate the embedded titanium spheres as in situ calibration targets for BSC estimation. The first experiment quantified the backscattered signal strength from titanium spheres of three sizes: 0.5, 1, and 2 mm in diameter. The second set of experiments assessed the repeatability of BSC estimates from the titanium spheres and compared these BSCs to theory. The third set of experiments quantified the ability of the titanium bead to provide an in situ reference spectrum in the presence of a lossy layer on top of the sample. The final set of experiments quantified the ability of the bead to provide a calibration spectrum over multiple depths in the sample. All experiments were conducted using an L9-4/38 linear array connected to a SonixOne system. The strongest signal was observed from the 2-mm titanium bead with the signal-to-noise ratio (SNR) of 11.6 dB with respect to the background speckle. Using an analysis bandwidth of 2.5-5.5 MHz, the mean differences between the experimentally derived BSCs and BSCs derived from the Faran theory were 0.54 and 0.76 dB using the array and a single-element transducer, respectively. The BSCs estimated using the in situ calibration approach without the layer and with the layer and using the reference phantom approach with the layer were compared to the reference phantom approach without the layer present. The mean differences in BSCs were 0.15, 0.73, and -9.69 dB, respectively. The mean differences of the BSCs calculated from data blocks located at depths that were either 30 pulse lengths above or below the actual bead depth compared to the BSC calculated at bead depth were -1.55 and -1.48 dB, respectively. The results indicate that an in situ calibration target can account for overlaying tissue losses, thereby improving the robustness of BSC-based estimates.