Fig. 4. Targeted imaging performance of NaGdF₄@PEG@bevacizumab–Cy5.5 nanoparticles (NPBCNs) in endometriosis rats. (a) MR-signal intensity of the endometriosis lesion in the targeted group and non-targeted group with prolonged duration after intravenous administration (*, p < 0.05). (b) Representative T₁-weighted images of rats with endometriosis in the targeted group before and after intravenous injection of NPBCNs. (c) Representative T₁-weighted images of rats with endometriosis in the non-targeted group before and after intravenous injection NaGdF₄@PEG–NHS–Cy5.5 nanoparticles (NPCNs). (d) Fluorescence image of the targeted group and the non-targeted group and NPCNs on 3 d post-injection (H = high and L = low).