History of radiation dose metrics spins heads

The pace of technological development generally outruns that of government. Nowhere is that more evident than in the history of radiation dose measurement. Following is a chronology of national and international efforts to standardize the measurement of x-ray output from CT scanners.

1977: The International Commission on Radiological Protection (ICRP) develops the effective dose equivalent, H.

1980s: Units of measurement are changed to reflect international standards: Rad becomes gray; rem becomes Sievert; and mCi becomes MBq. While most of the world uses grays and Sieverts, the U.S. sticks to rads and rems, further confusing matters.

1991: The Nuclear Regulatory Commission adopts H for radiation dose.

1991: The ICRP replaces H with effective dose, E.

1993: The National Council on Radiation Protection and Measurements adopts E.

2004: The ICRP proposes modification of E.

"Much of the confusion among the radiological community stems from the regulatory nature of these standards. The only professional who can tie it all together is the medical physicist," said Orhan Suleiman, Ph.D., senior science policy advisor in the FDA's Office of Drug Evaluation.