Tsui Po-Hsiang, Yeh Chih-Kuang, Chang Chien-Cheng, Chen Wen-Shiang
Division ofMechanics, Research Center for Applied Sciences Academia Sinica, Taipei, 11529, Taiwan, ROC.
Ultrason Imaging. 2008 Apr;30(2):78-94. doi: 10.1177/016173460803000202.
Conventional ultrasonic B-mode images qualitatively describe tissue structures but are unsuitable for quantitative analyses of scatterer properties. We have recently developed an ultrasonic parametric imaging technique based on the Nakagami statistical distribution that is able to quantify scatterer concentrations. The aim of the present study is to further explore both the behavior of a Nakagami image in characterizing different scatterer structures at different signal-to-noise ratios (SNRs) and the feasibility of Nakagami imaging using a general commercial ultrasound scanner for tissue examinations. Simulations, experiments on a tissue-mimicking phantom and in vitro measurements on a muscle tissue before and after microwave treatment were carried out. The SNR and contrast-to-noise ratio (CNR) were estimated to quantify image performance. The results demonstrate that a Nakagami image can differentiate different scatterer concentrations for single, hypoechoic and hyperechoic targets. Also, a Nakagami image, when combined with an ultrasound scanner, can complement the B-scan to characterize tissue and to identify the region of interest with a larger CNR. However, the noise effect can degrade the performance of a Nakagami image. When the signal SNR decreased to 15 dB in simulations and to 8 dB in experiments, the CNR of the hyperechoic Nakagami image decreased by 4% and 27%, respectively, and that of the hypoechoic one decreased by 42% and 80%, respectively. These results indicate that a Nakagami image behaves well in identifying regions with high scatterer concentrations but does not perform well when both the scatterer concentration and SNR are low.
传统超声B模式图像可定性描述组织结构，但不适用于散射体特性的定量分析。我们最近基于 Nakagami 统计分布开发了一种超声参数成像技术，该技术能够量化散射体浓度。本研究的目的是进一步探索 Nakagami 图像在不同信噪比（SNR）下表征不同散射体结构的行为，以及使用通用商用超声扫描仪进行组织检查时 Nakagami 成像的可行性。进行了模拟、在组织仿体上的实验以及对微波治疗前后肌肉组织的体外测量。估计了信噪比和对比噪声比（CNR）以量化图像性能。结果表明，Nakagami 图像可以区分单个、低回声和高回声目标的不同散射体浓度。此外，当与超声扫描仪结合使用时，Nakagami 图像可以补充B扫描以表征组织并以更大的CNR识别感兴趣区域。然而，噪声效应会降低 Nakagami 图像的性能。在模拟中当信号SNR降至15 dB且在实验中降至8 dB时，高回声Nakagami图像的CNR分别下降了4%和27%，低回声图像的CNR分别下降了42%和80%。这些结果表明，Nakagami图像在识别高散射体浓度区域时表现良好，但在散射体浓度和SNR都较低时性能不佳。
