An Junseok, Sugita Naohiro, Shinshi Tadahiko
Department of Mechanical Engineering, Institute of Science Tokyo, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
Laboratory for Future Interdisciplinary Research of Science and Technology (FIRST), Institute of Integrated Research (IIR), Institute of Science Tokyo, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8501, Japan.
Phys Med Biol. 2025 Jul 16;70(14). doi: 10.1088/1361-6560/adeb3d.
. Super-resolution ultrasonography (SR-US) provides detailed microvasculature images, improving diagnostic precision. However, it typically depends on tacking microbubbles (MBs) used as contrast agents at low concentration. This process requires acquiring a large amount of acoustic data, leading to longer acquisition times. In this paper, we describe a method that allows for the use of higher concentrations of MBs, which reduces the acquisition time and enables high-speed SR-US. Our approach involves isolating and detecting individual MBs even when they are located close to each other, making it possible to use higher bubble concentrations efficiently.. In this study, as introduced in previous research, we use phase patterned waves (PPWs) to isolate MBs by adjusting the intensities of each bubble's point spread function (PSF). The PPWs create high and low sound pressure across the lateral plane, optimizing the variation in PSF intensities for MBs positioned side by side. Unlike conventional irradiation method of ultrasound plane waves, PPWs cause significant sound pressure attenuation with increasing axial distance due to destructive interference. This effect allows us to alternate the PSF intensities for MBs aligned along the axial direction. By estimating the positions of MBs in both the lateral and axial directions and combining them into two-dimensional coordinates, we can accurately determine the final positions of the MBs.. We applied PPWs and conventional ultrasound irradiation methods to estimate the positions of two MBs, achieving accuracy within 25% of the wavelength from their actual locations, even when the bubbles were closer than Sparrow's resolution limit. Furthermore, using an overlapped PSF model, we improved the accuracy of the estimated positions to within an average of 15% of the wavelength from their true locations, regardless of the number of overlapping MBs or their relative positions.. Isolating MBs using PPWs is expected to enable high concentrations of MBs in SR-US, paving the way for high-speed SR-US.
超分辨率超声检查（SR-US）可提供详细的微血管图像，提高诊断精度。然而，它通常依赖于使用低浓度的微泡（MBs）作为造影剂。这个过程需要采集大量的声学数据，导致采集时间更长。在本文中，我们描述了一种方法，该方法允许使用更高浓度的MBs，从而减少采集时间并实现高速SR-US。我们的方法包括即使单个MBs彼此靠近时也能将其分离和检测出来，从而能够有效地使用更高的气泡浓度。在本研究中，如先前研究所介绍的，我们使用相位图案波（PPWs）通过调整每个气泡的点扩散函数（PSF）的强度来分离MBs。PPWs在横向平面上产生高低声压，优化并排放置的MBs的PSF强度变化。与传统的超声平面波照射方法不同，由于相消干涉，PPWs会随着轴向距离的增加而导致显著的声压衰减。这种效应使我们能够交替排列沿轴向排列的MBs的PSF强度。通过估计MBs在横向和轴向上的位置并将它们组合成二维坐标，我们可以准确地确定MBs的最终位置。我们应用PPWs和传统的超声照射方法来估计两个MBs的位置，即使气泡比瑞利分辨极限更近，也能实现其估计位置与实际位置的误差在波长的25%以内。此外，使用重叠PSF模型，无论重叠MBs的数量或它们的相对位置如何，我们都将估计位置的精度提高到平均在其真实位置波长的15%以内。使用PPWs分离MBs有望在SR-US中实现高浓度的MBs，为高速SR-US铺平道路。
