The influences of ambiguity phase aberration profiles on focusing quality in the very near field--part I: single range focusing on transmission.
The influences of ambiguity phase aberration profiles on focusing quality in the very near field--part I: single range focusing on transmission.
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模糊相位像差轮廓对极近场聚焦质量的影响——第一部分：单范围聚焦传输。
DOI：
10.1109/58.981384
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
Yue Li
中科院分区：
文献类型：
--
作者：
Yue Li
大多数相位像差测量算法对恒定相位像差和倾斜相位像差存在歧义。基于单范围聚焦的菲涅耳（近场）近似和弗劳恩霍夫（远场）近似，恒定和倾斜的相位像差只改变焦点的位置，不影响像的聚焦质量。因此，在这些算法和相关理论分析中，模糊相位像差通常被认为是无害的，而被忽略。然而，在许多医学超声成像情况下，菲涅尔和弗劳恩霍夫近似可能失效，例如，当成像场处于非常近场时（f值约为1）。在极近场，虽然已知恒定和倾斜的相位像差会降低聚焦质量，但文献中似乎缺乏对其影响的定量分析结果，这也是本文的目的。本文对医学超声成像中常用的透射聚焦方法——单范围聚焦透射进行了非常近场近似的定量分析。恒定和倾斜相位像差轮廓的可容忍水平是成像系统的f数和波长的函数。由于某些相位像差测量算法对二次相位像差曲线也可能存在歧义，因此也纳入了分析。将理论结果与数值和仿真结果进行了比较。这些结果表明，只有在一定条件下，倾斜和二次相位像差的影响才能被忽略。
Most phase aberration measurement algorithms have an ambiguity for constant and tilted phase aberration profiles. Based on the Fresnel (near field) approximation with single range focusing and the Fraunhofer (far field) approximation, constant and tilted phase aberration profiles change the position of the focal point only and do not influence the image focusing quality. Therefore, ambiguity phase aberration profiles are generally considered to be harmless and ignored in those algorithms and related theoretical analyses. However, Fresnel and Fraunhofer approximations may become invalid under many medical ultrasound imaging situations, e.g., when the imaging field is in the very near field (f-number approximately 1). In the very near field, although it is known that constant and tilted phase aberration profiles may degrade the focusing quality, it seems that there is a lack of quantitative analysis results in the literature about their influences, and this is the purpose of the current paper. In this paper, a quantitative analysis with a very near field approximation is performed for single range focusing on transmission, which is a commonly used transmission focusing method in medical ultrasound imaging. The tolerable levels of constant and tilted phase aberration profiles are derived as a function of the imaging system's f-number and wavelength. Because some phase aberration measurement algorithms may also have an ambiguity for quadratic phase aberration profiles, they are also included in the analysis. The theoretical results are compared with numerical and simulation results. These results have shown that the influences of tilted and quadratic phase-aberration profiles can be ignored only under certain conditions in the very near field.
影响因子：
2.4
作者：
CHRISTOPHER, PT;PARKER, KJ
通讯作者：
PARKER, KJ