IEEE Trans Med Imaging. 2019 Oct;38(10):2326-2337. doi: 10.1109/TMI.2019.2897588. Epub 2019 Feb 5.
In optoacoustic tomography, negatively focused detectors have been shown to improve the tangential image resolution without sacrificing sensitivity. Since no exact inversion formulas exist for optoacoustic image reconstruction with negatively focused detectors, image reconstruction in such cases is based on using the virtual-detector approximation, in which it is assumed that the response of the negatively focused detector is identical, up to a constant time delay, to that of a point-like detector positioned in the detector's center of curvature. In this paper, we analyze the response of negatively focused spherical ultrasound detectors in three dimensions and demonstrate how their properties affect the optoacoustic reconstruction. Our analysis sheds new light on commonly reported experimental reconstruction artifacts in optoacoustic systems that employ negatively focused detectors. Based on our analysis, we introduce a simple correction to the virtual-detector approximation that significantly enhances image contrast and reduces artifacts.
在光声断层摄影术中，已证明负聚焦探测器可以在不牺牲灵敏度的情况下提高切向图像分辨率。由于对于具有负聚焦探测器的光声图像重建不存在精确的反演公式，因此在这种情况下的图像重建基于使用虚拟探测器近似，其中假设负聚焦探测器的响应与位于探测器曲率中心的点状探测器的响应相同，只是存在一个恒定的时间延迟。在本文中，我们分析了三维中的负聚焦球形超声探测器的响应，并展示了它们的特性如何影响光声重建。我们的分析揭示了在使用负聚焦探测器的光声系统中常见的实验重建伪影。基于我们的分析，我们引入了对虚拟探测器近似的简单校正，这显著提高了图像对比度并减少了伪影。
