Source:http://linkedlifedata.com/resource/umls/id/C0439426
NCI: A unit of mass flow rate equivalent to the rate at which one millionth of a gram of matter crosses a given surface or is delivered to a given object or space over a period of time equal to twenty four hours. Microgram per day is also a dose administration rate unit equal to the rate at which one millionth of a gram of a product is administered per unit of time equal to twenty four hours.,NCI: A unit of mass flow rate equivalent to the rate at which one millionth of a gram of matter travels to a given object or space over a period of time equal to twenty four hours. Microgram per day is also a dose administration rate unit equal to the rate at which one millionth of a gram of a product is administered per unit of time equal to twenty four hours.(NCI)