Most of the tests that doctors use to diagnose cancer — such as mammography, colonoscopy, and CT scans — are based on imaging. More recently, researchers have also developed molecular diagnostics that can detect specific cancer-associated molecules that circulate in bodily fluids like blood or urine. MIT engineers have now created a new diagnostic nanoparticle that combines both of these features: It can reveal the presence of cancerous proteins through a urine test, and it functions as an imaging agent, pinpointing the tumor location. In principle, this diagnostic could be…