This study evaluates the use of 3D printed phantoms for 3D super-resolution ultrasound imaging (SRI) algorithm calibration. The main benefit of the presented method is the ability to do absolute 3D micro-positioning of sub-wavelength sized ultrasound scatterers in a material having a speed of sound comparable to that of tissue. Stereolithography is used for 3D printing soft material calibration micro-phantoms containing eight randomly placed scatterers of nominal size 205 μm $\times$ 205 μm $\times$ 200 μm. The backscattered pressure spatial distribution is evaluated to show similar distributions from micro-bubbles as the 3D printed scatterers. The printed structures are found through optical validation to expand linearly in all three dimensions by 2.6% after printing. SRI algorithm calibration is demonstrated by imaging a phantom using a $\lambda$/2 pitch 3 MHz 62+62 row-column addressed (RCA) ultrasound probe. The printed scatterers will act as point targets, as their dimensions are below the diffraction limit of the ultrasound system used. Two sets of 640 volumes containing the phantom features are imaged, with an intervolume uni-axial movement of the phantom of 12.5 μm, to emulate a flow velocity of 2 mm/s at a frame rate of 160 Hz. The ultrasound signal is passed to a super-resolution pipeline to localise the positions of the scatterers and track them across the 640 volumes. After compensating for the phantom expansion, a scaling of 0.989 is found between the distance between the eight scatterers calculated from the ultrasound data and the designed distances. The standard deviation of the variation in the scatterer positions along each track is used as an estimate of the precision of the super-resolution algorithm, and is expected to be between the two limiting estimates of (${\tilde{\sigma }}_x,{\tilde{\sigma }}_y,{\tilde{\sigma }}_z$) = (22.7 μm, 27.6 μm, 9.7 μm) and (${\tilde{\sigma }}_x,{\tilde{\sigma }}_y,{\tilde{\sigma }}_z$) = (18.7 μm, 19.3 μm, 8.9 μm). In conclusion, this study demonstrates the use of 3D printed phantoms for determining the accuracy and precision of volumetric super-resolution algorithms.

这项研究评估了3D打印体模在3D超分辨率超声成像（SRI）算法校准中的使用。所提出的方法的主要优点是能够在声速与组织速度相当的材料中对亚波长大小的超声散射体进行绝对3D微定位。立体光刻技术用于3D打印软材料校准微型模型，该模型包含八个随机放置的，标称尺寸为205μm的散射体$\times$ 205微米 $\times$200微米 对背向散射的压力空间分布进行了评估，以显示来自微气泡的与3D打印散射体相似的分布。通过光学验证发现印刷结构在印刷后在所有三个维度上线性扩展2.6％。SRI算法的校准通过使用$\lambda$/ 2螺距3 MHz 62 + 62行列寻址（RCA）超声探头。印刷的散射体将用作点目标，因为它们的尺寸低于所用超声系统的衍射极限。对包含幻影特征的两组640体积进行成像，幻影的体间单轴移动为12.5μm，以160 Hz的帧频模拟2 mm / s的流速。超声信号被传递到超分辨率管线以定位散射体的位置并在640体积中跟踪它们。在补偿了幻像扩展后，根据超声数据计算出的八个散射体之间的距离与设计距离之间的比例为0.989。${\tilde{\sigma }}_X，{\tilde{\sigma }}_{ÿ}，{\tilde{\sigma }}_{ž}$）=（22.7μm，27.6μm，9.7μm）和（${\tilde{\sigma }}_X，{\tilde{\sigma }}_{ÿ}，{\tilde{\sigma }}_{ž}$）＝（18.7μm，19.3μm，8.9μm）。总之，本研究证明了使用3D打印体模确定体积超分辨率算法的准确性和精确性。