The first implantable device that can monitor a tumor for weeks or months after a biopsy and track its growth and how it responds to treatment has been developed by MIT scientists.

The cylindrical, 5-millimeter implant contains nagnetic nanoparticles coated with antibodies specific to the target molecules, which bind to the nanoparticles, causing them to clump together. The clumped nanoparticles produce a marked change in the MRI signal associated with the implanted device.