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![Theranostic nanoplatforms for treatment and diagnosis of rectal and colon cancer: a brief review](https://image.oaes.cc/83ef93bb-369e-4c25-a14d-b8ff8c9d63ea/2937.fig.2.jpg)
Figure 2. A: Following intravenous injection, SPIONs slowly extravasate from vascular space to interstitial space, from where they can be taken up by immune cells (monocytes/macrophages) and delivered via lymphatic vessels to lymph nodes. The SPIONs remain in normal nodal tissue and reduce MRI signal intensity, thereby enhancing contrast against any metastatic lesions in the node; B and C: demonstrating the mechanism of negative contrast agent, SPIONs in lymph node imaging; B: a conventional T2-weighted MR image of the lymph node showing the whole lymph node is associated with cancer metastases; C: the T2-weighted MR image of the lymph node with enhanced contrast produced by SPIONs showing only two small metastatic regions (e.g., hyper intense foci). The MR images in B and C were reproduced[96]. SPION: superparamagnetic iron oxide nanoparticle; MRI: magnetic resonance imaging