Fig. 2. Single-cell imaging using radioluminescence microscopy.

(a) Schematic diagram of the radioluminescence microscope. A CdWO₄ scintillator was placed above the radiolabelled cells and excited by β⁺ particles emitted from decaying radionuclides. The resulting optical photons were captured using a high numerical-aperture objective (20×, 0.75 NA) coupled to a 50 mm focal-length tube lens and an EM-CCD camera. (b) Representative brightfield and fluorescence images revealed the localisation of MDA-MB-231 cells, and radioluminescence images indicated [¹⁸F]HFB accumulated sporadically in regions (orange arrows, bottom panel) unrelated to the localisation of MDA-MB-231 cells (white arrows, bottom panel). (c) In contrast to bulk gamma counting, singe-cell analysis showed significantly greater binding of [¹⁸F]FDG to MDA-MB-231 cells in comparison to [¹⁸F]HFB. The accumulation of [¹⁸F]HFB in MDA-MB-231 cells was not significantly different from background. Experiments repeated ≥ twice. Error bars are mean ± SEM, *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001 and scale bar is 50 µm