Photoacoustic (PA) computed tomography (PACT) is a noninvasive hybrid imaging technique that combines optical excitation and acoustic detection to realize high contrast, high resolution, and deep penetration in biological tissues. However, the spatial resolution of PACT is limited by acoustic diffraction. Here, we report in vivo superresolution PACT, which breaks the acoustic diffraction limit by localizing the centers of single dyed droplets that are flowing in blood vessels. The droplets were prepared by dissolving hydrophobic absorbing dye in oil, followed by mixing with water. The dyed droplets generate much higher-amplitude PA signals than blood and can flow smoothly in vessels; thus, they are excellent tracers for localization-based superresolution imaging. The in vivo resolution enhancement was demonstrated by continuously imaging the cortical layer of a mouse brain during droplet injection. The droplets that were flowing in the vessels were localized, and their center positions were used to construct a superresolution image that exhibits sharper features and more finely resolved vascular details. An improvement in spatial resolution by a factor of 6 has been realized in vivo by the droplet localization technique.

光声（PA）计算机断层扫描（PACT）是一种无创混合成像技术，结合了光激发和声波检测，可在生物组织中实现高对比度，高分辨率和深度穿透。但是，PACT的空间分辨率受到声学衍射的限制。在这里，我们报告了体内超分辨率PACT，它通过定位在血管中流动的单个染色液滴的中心来打破声学衍射极限。通过将疏水性吸收性染料溶解在油中，然后与水混合来制备液滴。染色后的液滴产生的振幅PA信号要比血液高得多，并且可以在血管中顺畅流动。因此，它们是基于定位的超分辨率成像的出色示踪剂。通过在液滴注射过程中连续成像小鼠大脑皮层，证明了体内分辨率的提高。定位在血管中流动的液滴，并使用其中心位置来构建超分辨率图像，该图像表现出更清晰的特征和更精细地分辨的血管细节。通过液滴定位技术已经在体内实现了空间分辨率提高了6倍。