2007 recommendations of the ICRP change basis for estimation of the effective dose: what is the impact on radiation dose assessment of patient and personnel?

PURPOSE: In radiation protection regulations the algorithm for effective dose calculation is based on Publication 60 (1990) of the International Commission on Radiological Protection (ICRP). The modifications to the tissue weighting factors in Publication 103 (2007) of the ICRP will affect the present methodology of calculating the effective dose and will also have an impact on its assessment. This paper evaluates circumstances under which the application of the new model yields relevant dose differences compared to the prevailing model. MATERIALS AND METHODS: Effective doses were calculated and compared from the measured organ doses according to ICRP 60 and ICRP 103, respectively. The measurements of patient doses were carried out with an anthropomorphic phantom for thoracic and coronary CT examinations. Exposure of radiological personnel was measured based on the geometry of angiographic examinations using two anthropomorphic phantoms. RESULTS: The change of the weighting factor for the breast from 0.05 to 0.12 leads to a noticeable increase in the effective dose for thoracic (21 %) and coronary (31 %) CT examinations. Calculating sex-specific effective doses based on ICRP 60, the dose for coronary CT examination for women is 1.7 times higher than for men. Based on ICRP 103, the difference between female and male doses increases to a factor of 3.3. Due to the consideration of organs in the head and neck region as introduced in ICRP 103, for angiography the personnel is exposed to 24 - 50 % and 38 - 142 % higher doses with and without thyroid protection, respectively. Thereby, the official personal dosimetry will underestimate the effective dose according to ICRP 103 by a factor of 1.6 - 2.4 with thyroid protection and 1.1 - 1.4 without thyroid protection. CONCLUSION: The revision of the parameters for effective dose calculation leads to higher doses and greater sex-specific differences for radiological examinations involving exposure of the breast. This effect should be considered when justifying any radiological examination. For the personnel, the new model results in higher effective doses due to increased emphasis on the organs in the head and neck region. Hence to optimize radiation protection of personnel, the use of radiation-protective shielding for this region becomes more important.

[How conservative is routine personal dosimetry monitoring in diagnostic radiology?]. / Wie konservativ ist die Abschätzung der effektiven Dosis durch die amtliche Personendosimetrie für das Personal in der Radiologie?

PURPOSE: Dose values obtained by official personal radiation exposure monitoring are often considered equivalent to the effective dose of a person. This paper provides estimates of the extent of deviation between the two dose concepts under various conditions. MATERIALS AND METHODS: Doses for patients and personnel were measured using thermoluminescence dosimeters for five different geometries at three work settings in a radiology department. Patients and personnel were simulated with anthropomorphic phantoms. Different types of protective clothing as well as permanent protection shields were considered in the calculations. RESULTS: Dose values obtained by official personal dose monitoring are conservative only for specific radiation protection situations. With state-of-the-art personal protective equipment (wrap-around style lead apron with thyroid shield), the ratio between effective dose and personal dose varies between 0.6 and 1.25. Without thyroid protection the official personal dose systematically underestimates the effective dose: for protective clothing with 0.5 mm lead equivalent without thyroid shielding, the effective dose exceeds the personal dose by factors between 1.7 and 3.1. If protective clothing with lead equivalent 0.35 mm is used, this factor varies between 1.1 and 1.82. CONCLUSION: The official exposure monitoring algorithms for estimating the effective dose for occupationally exposed personnel are not always appropriate for typical situations in diagnostic radiology. Improved dose measurement protocols should avoid underestimation of the effective dose. The results presented herein provide an opportunity to derive more realistic effective dose values from personal dosimetry measurements.

[Optimizing staff radiation protection in radiology by minimizing the effective dose]. / Optimierung des Strahlenschutzes für das Personal in der Radiologie auf Grundlage der effektiven Dosis.

PURPOSE: In the present study the optimization of radiation protection devices is achieved by minimizing the effective dose of the staff members since the stochastic radiation effects correlate to the effective dose. MATERIALS AND METHODS: Radiation exposure dosimetry was performed with TLD measurements using one Alderson Phantom in the patient position and a second phantom in the typical position of the personnel. Various types of protective clothing as well as fixed shields were considered in the calculations. RESULTS: It was shown that the doses of the unshielded organs (thyroid, parts of the active bone marrow) contribute significantly to the effective dose of the staff. Therefore, there is no linear relationship between the shielding factors for protective garments and the effective dose. An additional thyroid protection collar reduces the effective dose by a factor of 1.7 - 3.0. X-ray protective clothing with a 0.35 mm lead equivalent and an additional thyroid protection collar provides better protection against radiation than an apron with a 0.5 mm lead equivalent but no collar. CONCLUSION: The use of thyroid protection collars is an effective preventive measure against exceeding occupational organ dose limits, and a thyroid shield also considerably reduces the effective dose. Therefore, thyroid protection collars should be a required component of anti-X protection.

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.