An analytic approach to double dosimetry algorithms in occupational dosimetry using energy dependent organ dose conversion coefficients.

Personnel dose in diagnostic radiology is often underestimated. Typically the effective dose E is estimated based on dosimeters worn underneath the protective clothing measuring the personal dose equivalent Hp(10). This one-spot-measurement systematically neglects the exposure to the unshielded organs in the head and neck region. In this paper, energy dependent double dosimetry algorithms in the range of 30-80 keV are derived using organ dose conversion coefficients. The doses of shielded organs are assigned to a single dosimeter in the anterior thoracic region (chest) underneath the apron (Hp,c,u), and the doses of the organs not shielded are assigned to another dosimeter placed on the front area of the neck over the protective garment (Hp,n,o) with E = a1 Hp,c,u(10) + a2 Hp,n,o(10). Organs not completely shielded are categorized correspondingly. The coefficients a1 and a2 increase with higher energies up to 70 keV. The factors a2 are clearly higher according to ICRP 103 (rather than ICRP 60) because ICRP 103 considers additional organs in the head and neck region. According to ICRP 103, a conservative general algorithm with thyroid protection is E = 0.84 Hp,c,u(10) + 0.051 Hp,n,o(10) and without thyroid protection E = 0.79 Hp,c,u(10) + 0.100 Hp,n,o(10).