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Figure 4: (a) Photoacoustic signal distribution of GO-AuNS-DOTA-Gd in tumor regions at different time points before and after injection; (b) MRI image of GO-AuNS-DOTA-Gd on the coronal plane in tumor regions at different time points before and after injection; (c) quantitative analysis of the PAI signal in the tumor regions; (d) quantitative analysis of MRI gray intensity in the tumor regions; (e) reconstructed 3D image and 3D visualization of tumor and its surrounding tissue based on the MRI slice images; (f) MRI image of GO-AuNS-DOTA-Gd at different concentrations; (g) linear relationship between relaxation rate (1/) and Gd3+ concentrations in GO-AuNS-DOTA-Gd aqueous solutions; (h) representative vertical PET images of a mouse with tumor after 18F-FDG injection.