【作者】 徐颖；

【导师】 李平；

【作者基本信息】 重庆大学 ， 仪器科学与技术， 2006， 硕士

【摘要】 B超成像因其成本低、使用方便及实时成像等优点，已成为HIFU治疗中实时监控和疗效评价的重要手段。然而，HIFU治疗系统超声成像中产生的雾状伪像，掩盖了人体组织的真实成像，影响了系统对病灶的定位和治疗。论文分析了雾状伪像的物理成因，对雾状伪像建立了数学模型，并以此为基础完成了雾状伪像的定位和特征分析。依据伪像和组织成像的不同特点，提出了一种差分消除雾状伪像的处理方法。将该方法用于临床图像的处理，提高了B超成像的质量。 论文首先研究HIFU治疗系统超声成像中的伪像。在分析了超声诊断图像中各类伪像的物理成因和临床表现后指出，HIFU治疗系统中除存在上述传统伪像外，还会出现一种雾状伪像，并结合HIFU治疗系统中B超探头的使用环境，说明雾状伪像不同与传统伪像的形成机理。在伪像消除方面，主要介绍了散斑和混响伪像的消除方法，讨论了各种方法的优缺点。 论文根据雾状伪像的成因，建立了雾状伪像的数学模型。以模型为基础，对不同成像条件下的伪像分布进行了仿真实验，并由此归纳出雾状伪像的特征。然后依据模型，完成了临床图像中雾状伪像的自动定位。定位结果验证了成因分析和模型的正确性，且雾状伪像特征的临床表现也与模型得出的伪像特征一致。 论文分析了模型应用于雾状消除的局限性，指出需要寻找消除雾状伪像的新方法。结合模型对雾状伪像的特征分析和大量临床图像的观测结果，总结出伪像和组织成像的不同特点，并以此为依据提出了一种差分消除雾状伪像的方法：治疗前用B超探头分别采集接触体表和治疗位置的图像，进行几何配准和灰度匹配后差分得出伪像，最后用治疗位置获取的图像减去估计的伪像恢复出真实组织。方法用当前采集的图像与预先估计的伪像相减恢复出治疗过程中的组织图像，能满足处理的实时性要求；其次，运用图像融合的思想，不需要伪像和组织的先验知识。在提出雾状伪像消除算法的同时，给出了雾状伪像消除效果的评价标准，并以此为基础对算法消除伪像的结果进行了分析。 最后，论文将雾状伪像的消除算法融入到原有的HIFU治疗方案中，形成了一种能实时消除HIFU治疗系统超声成像中雾状伪像的新治疗方案。以JC型高强度聚焦超声治疗系统为例，对不同种类和同一种类探头在不同深度获取的图像进行处理。临床图像的实验结果表明，算法能有效抑制临床图像中的雾状伪像，从而更多还原

【Abstract】 B-mode imaging is a significant way for real-time monitory and therapeutic evaluation in HIFU therapy due to its characteristics of low-cost, convenience and real-time imaging. However, a real image of tissue components is always covered by fog artifacts resulting from the ultrasonic imaging in HIFU therapeutic system. Fog artifacts have a bad effect on focus location and HIFU therapy. In this paper, the forming mechanism of fog artifacts is analyzed and the mathematical model is established. Thus, the fog artifacts in clinic images can be located and characterized based on the model. According to the different features between the fog artifacts and the tissue images, a differential- method for reducing fog artifacts is proposed. The experiments on clinic images show that the differential method improves the quality of B-mode imaging.Firstly, the paper studies the artifacts in B-mode imaging of HIFU therapeutic system. By analyzing the forming mechanisms and the clinical manifestations of all kinds of artifacts in ultrasonic diagnostic images, this paper indicates that a new kind of artifacts called "fog artifact" appear in the B-mode images acquired by HIFU therapeutic system. Then the forming mechanism of fog artifacts which differs from tradition artifacts is explained combined with the operating environment of a B-mode probe in HIFU therapeutic system. Suppression methods for speckle and reverberation are introduced and their advantages and drawbacks are also discussed.According to the forming mechanism of fog artifacts, the mathematical model is established. Simulation experiments under different imaging conditions are done based on the model and features of fog artifacts are also summarized. The model is used to locate the fog artifacts in clinic images. The experimental results verify the correctness of mechanism analysis and mathematical model.Based on the different characteristics between the fog artifacts and the tissue images, a differential method for removing fog artifacts is proposed. The method regards the image obtained from the probe’s position close to skin as a reference image, which has a clear appearance of the tissue. The reference image is registered and更多还原