Effective dose and effective dose equivalent--the impact of the new ICRP definition for external photon irradiation.

In a recent recommendation, the International Commission on Radiological Protection substituted the effective dose equivalent, HE, with a similar quantity--the "effective dose," E--changing both the set of organs considered and the respective weighting factors. To quantify the impact of these changes, calculations of E and HE were performed for various photon energies and external irradiation geometries using a Monte Carlo code and mathematical anthropomorphic phantoms to which an esophagus was introduced for this purpose. For energies greater than 15 keV, E less than HE, the difference depending on photon energy and exposure geometry.