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 H-p(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 (H-p,H-c,H-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 (H-p,H-n,H-o) with E = a(1) H-p,H-c,H-u (10) + a(2) H-p,H-n,H-o (10). Organs not completely shielded are categorized correspondingly. The coefficients a(1) and a(2) increase with higher energies up to 70 keV. The factors a 2 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 H-p,H-c,H-u (10) + 0.051 H-p,H-n,H-o (10) and without thyroid protection E = 0.79 H-p,H-c,H-u (10) + 0.100 H-p,H-n,H-o (10). Health Phys. 99(6):800-805; 2010