In vivo molecular imaging can measure the average kinetics and movement routes of injected cells through the body. However, owing to non-specific accumulation of the contrast agent and its efflux from the cells, most of these imaging methods inaccurately estimate the distribution of the cells. Here, we show that single human breast cancer cells loaded with mesoporous silica nanoparticles concentrating the ⁶⁸Ga radioisotope and injected into immunodeficient mice can be tracked in real time from the pattern of annihilation photons detected using positron emission tomography, with respect to anatomical landmarks derived from X-ray computed tomography. The cells travelled at an average velocity of 50 mm s⁻¹ and arrested in the lungs 2–3 s after tail-vein injection into the mice, which is consistent with the blood-flow rate. Single-cell tracking could be used to determine the kinetics of cell trafficking and arrest during the earliest phase of the metastatic cascade, the trafficking of immune cells during cancer immunotherapy and the distribution of cells after transplantation.

体内分子成像可以测量注射细胞通过身体的平均动力学和运动路线。然而，由于造影剂的非特异性积累及其从细胞中的流出，大多数这些成像方法都不能准确估计细胞的分布。^{在这里，我们展示了载有浓缩68} Ga 放射性同位素的介孔二氧化硅纳米颗粒并注射到免疫缺陷小鼠体内的单个人类乳腺癌细胞可以根据使用正电子发射断层扫描检测到的湮灭光子模式进行实时跟踪，相对于来自X 射线计算机断层扫描。^{细胞以 50 mm s -1}的平均速度移动并在尾静脉注射到小鼠后 2-3 秒停在肺部，这与血流速度一致。单细胞追踪可用于确定转移级联反应最早阶段细胞运输和停滞的动力学、癌症免疫治疗期间免疫细胞的运输以及移植后细胞的分布。