van Hal Vera H J, Muller Jan-Willem, van Sambeek Marc R H M, Lopata Richard G P, Schwab Hans-Martin
Photoacoustics & Ultrasound Laboratory Eindhoven (PULS/e), Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB Eindhoven, The Netherlands.
Photoacoustics & Ultrasound Laboratory Eindhoven (PULS/e), Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB Eindhoven, The Netherlands; Department of Vascular Surgery, Catharina Hospital Eindhoven, P.O. Box 1350, 5602 ZA Eindhoven, The Netherlands.
Ultrasonics. 2023 May;131:106936. doi: 10.1016/j.ultras.2023.106936. Epub 2023 Feb 7.
Abdominal ultrasound image quality is hampered by phase aberration, that is mainly caused by the large speed-of-sound (SoS) differences between fat and muscle tissue in the abdominal wall. The mismatch between the assumed and actual SoS distribution introduces general blurring of the ultrasound images, and acoustic refraction can lead to geometric distortion of the imaged features. Large aperture imaging or dual-transducer imaging can improve abdominal imaging at deep locations by providing increased contrast and resolution. However, aberration effects for large aperture imaging can be even more severe, which limits its full potential. In this study, a model-based aberration correction method for arbitrary acquisition schemes is introduced for delay-and-sum (DAS) beamforming and its performance was analyzed for both single- and dual-transducer ultrasound imaging. The method employs aberration corrected wavefront arrival times, using manually assigned local SoS values. Two wavefront models were compared. The first model is based on a straight ray approximation, and the second model on the Eikonal equation, which is solved by a multi-stencils fast marching method. Their accuracy for abdominal imaging was evaluated in acoustic simulations and phantom experiments involving tissue-mimicking and porcine material with large SoS contrast (∼100 m/s). The lateral resolution was improved by up to 90% in simulations and up to 65% in experiments compared to standard DAS, in which the use of Eikonal beamforming generally outperformed straight ray beamforming. Moreover, geometric distortions were mitigated in multi-aperture imaging, leading to a reduction in position error of around 80%. A study on the sensitivity of the aberration correction to shape and SoS of aberrating layers was performed, showing that even with imperfect segmentations or SoS values, aberration correction still outperforms standard DAS.
腹部超声图像质量受到相位畸变的影响，相位畸变主要由腹壁脂肪和肌肉组织之间较大的声速差异引起。假设的声速分布与实际声速分布之间的不匹配会导致超声图像普遍模糊，并且声折射会导致成像特征的几何畸变。大孔径成像或双换能器成像可以通过提供更高的对比度和分辨率来改善深部位置的腹部成像。然而，大孔径成像的像差效应可能更严重，这限制了其全部潜力。在本研究中，针对延迟求和（DAS）波束形成引入了一种基于模型的任意采集方案像差校正方法，并对单换能器和双换能器超声成像的性能进行了分析。该方法使用手动指定的局部声速值来采用像差校正的波前到达时间。比较了两种波前模型。第一种模型基于直线近似，第二种模型基于程函方程，通过多模板快速行进法求解。在涉及具有大声速对比度（约100 m/s）的组织模拟物和猪材料的声学模拟和体模实验中评估了它们在腹部成像中的准确性。与标准DAS相比，模拟中横向分辨率提高了90%，实验中提高了65%，其中使用程函波束形成通常优于直线波束形成。此外，在多孔径成像中几何畸变得到减轻，导致位置误差减少约80%。对像差校正对畸变层形状和声速的敏感性进行了研究，结果表明，即使分割或声速值不完善，像差校正仍优于标准DAS。
