Positron emission particle tracking (PEPT) enables 3D localization and tracking of single positron-emitting radiolabelled particles with high spatiotemporal resolution. The translation of PEPT to the biomedical imaging field has been limited due to the lack of methods to radiolabel biocompatible particles with sufficient specific activity and protocols to isolate a single particle in the sub-micrometre size range, below the threshold for capillary embolization. Here we report two key developments: the synthesis and ⁶⁸Ga-radiolabelling of homogeneous silica particles of 950 nm diameter with unprecedented specific activities (2.1 ± 1.4 kBq per particle), and the isolation and manipulation of a single particle. We have combined these developments to perform in vivo PEPT and dynamic positron emission tomography (PET) imaging of a single radiolabelled sub-micrometre size particle using a pre-clinical positron emission tomography/computed tomography scanner. This work opens possibilities for quantitative assessment of haemodynamics in vivo in real time, at the whole-body level using minimal amounts of injected radioactive dose and material.

正电子发射粒子跟踪 (PEPT) 能够以高时空分辨率对单个正电子发射放射性标记粒子进行 3D 定位和跟踪。PEPT 向生物医学成像领域的转化受到限制，因为缺乏对具有足够比活性的生物相容性颗粒进行放射性标记的方法，以及分离低于毛细血管栓塞阈值的亚微米尺寸范围内的单个颗粒的方案。在这里，我们报告了两个关键进展：具有前所未有的比活性（每个颗粒 2.1 ± 1.4 kBq）的 950 nm 直径均质二氧化硅颗粒的合成和⁶⁸ Ga 放射性标记，以及单个颗粒的分离和操作。我们将这些进展结合起来，使用临床前正电子发射断层扫描/计算机断层扫描扫描仪对单个放射性标记的亚微米尺寸颗粒进行体内 PEPT 和动态正电子发射断层扫描 (PET) 成像。这项工作为使用最少量注射的放射性剂量和材料在全身水平上实时定量评估体内血流动力学开辟了可能性。