IEEE Trans Ultrason Ferroelectr Freq Control. 2024 May;71(5):572-583. doi: 10.1109/TUFFC.2024.3379293. Epub 2024 May 10.
Quantitative ultrasound (QUS) techniques based on the backscatter coefficient (BSC) aim to characterize the scattering properties of biological tissues. A scattering model is fit to the measured BSC, and the fitted QUS parameters can provide local tissue microstructure, namely, scatterer size and acoustic concentration. However, these techniques may fail to provide a correct description of tissue microstructure when the medium is polydisperse and/or dense. The objective of this study is to investigate the effects of scatterer size polydispersity in sparse or dense media on the QUS estimates. Four scattering models (i.e., the monodisperse and polydisperse sparse models, and the monodisperse and polydisperse concentrated models based on the structure factor) are compared to assess their accuracy and reliability in quantifying the QUS estimates. Simulations are conducted with different scatterer size distributions for sparse, moderately dense, and dense media (volume fractions of 1%, 20%, and 73%, respectively). The QUS parameters are estimated by using model-based inverse methods at different center frequencies between 8 and 50 MHz. Experimental data are also analyzed using colon adenocarcinoma HT29 cell pellet biophantoms to further validate the results obtained from simulations at the volume fraction of 73%. Our findings reveal that the choice of scattering model has a significant impact on the accuracy of QUS estimates. For sufficiently high frequencies and dense media, the polydisperse concentrated model outperforms the other models and enables more accurate quantification. Furthermore, our results contribute to advancing our understanding of the complexities associated with scatterer size polydispersity and dense media in spectral-based QUS techniques.
基于背散射系数（BSC）的定量超声（QUS）技术旨在描述生物组织的散射特性。将散射模型拟合到测量的 BSC 上，并且拟合的 QUS 参数可以提供局部组织微结构，即散射体大小和声吸收浓度。然而，当介质为多分散性和/或密集时，这些技术可能无法正确描述组织微结构。本研究的目的是研究稀疏或密集介质中散射体大小多分散性对 QUS 估计的影响。比较了四种散射模型（即单分散和多分散稀疏模型，以及基于结构因子的单分散和多分散集中模型），以评估它们在定量 QUS 估计中的准确性和可靠性。对于稀疏、中度密集和密集介质（体积分数分别为 1%、20%和 73%），进行了不同散射体大小分布的模拟。使用基于模型的逆方法在 8 到 50 MHz 之间的不同中心频率下估计 QUS 参数。还使用结肠腺癌 HT29 细胞球生物仿体的实验数据进行分析，以进一步验证在体积分数为 73%时从模拟中获得的结果。我们的研究结果表明，散射模型的选择对 QUS 估计的准确性有重大影响。对于足够高的频率和密集的介质，多分散集中模型优于其他模型，能够实现更准确的量化。此外，我们的结果有助于深入了解与基于谱的 QUS 技术中的散射体大小多分散性和密集介质相关的复杂性。
