Figure 7: The multimodality comparison for in vivo imaging the dual-tumour xenografts.

(a) Six days after the subcutaneous injection of 4T1-luc2 tumour cells, two tumour lesions are visible on the back of a mouse model (red arrows). (b) Three slices of PET (280 μCi ¹⁸F-FDG) in sagittal and axial directions show clear ¹⁸F-FDG uptake in the lower tumour (red arrows) but no significant uptake in the upper one (white arrows). The position of the three PET slices are indicated in (a) with black dotted lines. (c) Without filtering, REFI (280 μCi ¹⁸F-FDG with 0.1 ml, 1 mg ml⁻¹ EO) shows optical signal of both tumours and brown adipose tissue (left mouse), but CLI does not visualize the upper back tumour (right mouse). (d) With 620 nm filtering, two tumours are visualized in REFI (left mouse), but Cerenkov signal are nearly vanished. (e) FMI of QD620 (0.1 ml, 10 mg ml⁻¹) does not show great tumour to normal tissue contrast due to the non-specificity of the fluorescent probe. The black circle indicates the regions of interest (ROI) of the background for calculating signal-to-background ratio.