Effective dose estimation in diagnostic radiology with two dosimeters: impact of the 2007 recommendations of the ICRP.

In many standard situations in radiation protection the effective dose is underestimated if it is based on the depth personal dose equivalent Hp(10) measured with a single dosimeter in the anterior thoracic region (chest) underneath the protective apron (Hp,c,u). The estimate can be significantly improved by inclusion of a second dosimeter worn on the front area of the neck over of the protective garment (Hp,n,o) representing organs and areas that are usually not completely covered by the protective garment. The recent recommendations of the International Commission on Radiological Protection (ICRP) emphasize the contribution of the head and neck region to the effective dose. This accentuates the need for a valid representation of this body region in the effective dose algorithm. In this paper we derived coefficients for the two-dosimeter situation using phantom measurements for selected radiological procedures with different geometries between patient and investigator. According to ICRP 60, the algorithm with {without} thyroid protection is E = 0.64{0.64} Hp,c,u + 0.016{0.073} Hp,n,o. According to ICRP 103, the algorithm becomes E = 0.60{0.60} Hp,c,u + 0.047{0.094} Hp,n,o. The ICRP 103 model reveals that the underestimation of the effective dose based on Hp(10) using a single dosimeter worn under the protective garment is even higher than previously assumed based on ICRP 60. Future personal dosimetry should be qualified by a two-dosimeter concept. The head and neck region which is not covered by a conventional protective garment needs to be protected by mounted shielding or other constructive measures.