In positron emission tomography,or PET,a patient ingests or is injected with a slightly radioactive substance that emits positrons,which can be monitored as the substance moves through the body.

• 在正电子发射X射线摄影技术(PET)中，病人要咽下或被注射一些有少许放射性的物质来发出正电子。当这些物质在人体内运动时，正电子可被监测到。