Center for Fast Ultrasound Imaging, Department of Health Technology, Technical University of Denmark, DK 2800, Kgs. Lyngby Denmark.
Department of Biomedical Sciences, University of Copenhagen, DK 2200, Copenhagen, Denmark; Department of Diagnostic Radiology, Rigshospitalet, DK 2100, Copenhagen, Denmark; Department of Clinical Medicine, University of Copenhagen, DK 2200, Copenhagen, Denmark.
Ultrasonics. 2022 May;122:106695. doi: 10.1016/j.ultras.2022.106695. Epub 2022 Feb 4.
Microbubble (MB) tracking plays an important role in ultrasound super-resolution imaging (SRI) by enabling velocity estimation and improving image quality. This work presents a new hierarchical Kalman (HK) tracker to achieve better performance at scenarios with high concentrations of MBs and high localization uncertainty. The method attempts to follow MBs with different velocity ranges using different Kalman filters. An extended simulation framework for evaluating trackers is also presented and used for comparison of the proposed HK tracker with the nearest-neighbor (NN) and Kalman (K) trackers. The HK tracks were most similar to the ground truth with the highest Jaccard similarity coefficient in 79% of the scenarios and the lowest root-mean-square error in 72% of the scenarios. The HK tracker reconstructed vessels with a more accurate diameter. In a scenario with an uncertainty of 51.2μm in MB localization, a vessel diameter of 250μm was estimated as 257μm by HK tracker, compared with 329μm and 389μm for the K and NN trackers. In the same scenario, the HK tracker estimated MB velocities with a relative bias down to 1.7% and a relative standard deviation down to 8.3%. Finally, the different tracking techniques were applied to in vivo data from rat kidneys, and trends similar to the simulations were observed. Conclusively, the results showed an improvement in tracking performance, when the HK tracker was employed in comparison with the NN and K trackers.
微泡（MB）跟踪在超声超分辨率成像（SRI）中起着重要作用，它可以实现速度估计和提高图像质量。本工作提出了一种新的分层卡尔曼（HK）跟踪器，以在 MB 浓度高和定位不确定性高的情况下获得更好的性能。该方法试图使用不同的卡尔曼滤波器跟踪具有不同速度范围的 MB。还提出了一种扩展的跟踪器评估框架，并将所提出的 HK 跟踪器与最近邻（NN）和卡尔曼（K）跟踪器进行了比较。在 79%的情况下，HK 轨迹与地面实况的相似度最高，具有最高的杰卡德相似系数，在 72%的情况下，HK 轨迹的均方根误差最低。HK 跟踪器重建的血管直径更准确。在 MB 定位不确定性为 51.2μm 的情况下，HK 跟踪器估计直径为 250μm 的血管为 257μm，而 K 和 NN 跟踪器分别为 329μm 和 389μm。在相同的情况下，HK 跟踪器估计 MB 速度的相对偏差低至 1.7%，相对标准偏差低至 8.3%。最后，不同的跟踪技术应用于大鼠肾脏的体内数据，观察到与模拟相似的趋势。总之，与 NN 和 K 跟踪器相比，当 HK 跟踪器被应用时，跟踪性能得到了提高。
