Emerging role of nanoparticles in the diagnostic imaging of gastrointestinal cancer.

Gastrointestinal (GI) cancer, which mainly includes tumors of the esophagus, stomach, liver, biliary system, pancreas, and colon, is one of the most common cancers and the dominant cause of cancer-related deaths globally. For the diagnosis of GI cancer, in addition to routine systemic imaging, such as computed tomography (CT), magnetic resonance imaging, and positron emission tomography-CT, locoregional imaging, which covers endoscopy and ultrasound, is also of great concern. However, the current mainstream contrast agents used in these imaging methods have poor specificity, short maintenance time, and severe side effects. In recent years, with the development of nanotechnology, nanoparticles, such as quantum dots, iron oxide nanoparticles, and gold nanoparticles, have offered many benefits in GI cancer imaging owing to their small size, customizable surface properties, and retention effect. An increasing number of studies have combined the traditional methods of imaging digestive tract tumors with nanoparticles, significantly improving the early diagnosis rate and staging accuracy. Here, we review the current evidence on the utilization of nanoparticles in the diagnostic imaging of GI tumors from the aspects mentioned above.