Combidex (generic name: ferumoxtran-10) is an investigational functional molecular imaging agent consisting of iron oxide nanoparticles for use in combination with MRI to aid in the differentiation of cancerous from normal lymph nodes. Lymph nodes are regularly the site for metastases of many different types of cancer, particularly breast cancer and prostate cancer. Computed tomography (CT) and MRI are the methods presently used for imaging lymph nodes. Present guidelines for imaging lymph nodes are that nodes greater than 10 mm in size are usually deemed cancerous while nodes less than 10 mm in size are generally presumed normal. CT and MRI cannot distinguish between lymph nodes that are enlarged due to the infiltration of cancerous cells as opposed to inflammation nor can these methods dependably detect disease in nodes that are not enlarged. Clinical studies have shown that Combidex accumulates in non-cancerous lymph node tissue, which may perhaps enable doctors using MRI to have improved diagnostic confidence in differentiating between normal and diseased lymph nodes.

Combidex is the brand name for an ultrasmall superparamagnetic iron oxide to detect metastatic disease in lymph nodes. Metastatic lymph nodes show very less uptake of this MRI contrast agent, which results in less signal decrease and allows the differentiation of normal lymph nodes from normal-sized, metastatic nodes.

Intraventricular or intracerebral injection, but not intracarotid administration of Combidex (100 ?g), resulted in MRI signal changes in the deep cervical lymph nodes around the carotid artery, and, less powerfully, in the superficial cervical nodes. Within 2 hours of Combidex administration, iron was histologically localized in cervical lymph nodes, with patched staining of capsule and peripheral sinus consistent with delivery via multiple afferent lymphatic vessels.