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NEWS AND INFORMATION
Year : 2012  |  Volume : 35  |  Issue : 2  |  Page : 101-102  

Recent developments in internal dosimetry


Internal Dosimetry Section, Radiation Safety Systems Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085, Maharashtra, India

Date of Web Publication21-May-2013

Correspondence Address:
Hemant Kumar Patni
Internal Dosimetry Section, Radiation Safety Systems Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


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How to cite this article:
Patni HK. Recent developments in internal dosimetry. Radiat Prot Environ 2012;35:101-2

How to cite this URL:
Patni HK. Recent developments in internal dosimetry. Radiat Prot Environ [serial online] 2012 [cited 2022 Jan 19];35:101-2. Available from: https://www.rpe.org.in/text.asp?2012/35/2/101/112356

In the past decade, various aspects of dosimetry and particularly internal dosimetry have been updated utilizing the latest information. The radiation weighting factors and epidemiologically-developed tissue weighting factors were revised in 2007 in Publication number 103 of the International Commission on Radiological Protection (ICRP). ICRP Publication 103 recommended a new methodology for the estimation of dose coefficients for reference adult occupationally-exposed workers, which included the estimation of absorbed and equivalent dose in gender-dependent computational phantoms and then averaging to use tissue weighting factors for the estimation of gender-independent effective dose. ICRP Publication 103 also contained the age-dependent risk factors for various tissues, which can be utilized for the estimation of age-dependent dose coefficients.

Earlier Monte Carlo simulations were carried out using the medical internal radiation dose phantoms (based on reference male and female data of ICRP Publication 23 1975), which were based on mathematical equations for the estimation of external dose coefficients and specific absorbed fractions (SAFs are used in the estimation of internal dose coefficients). Based on the recommendation of ICRP Publication 103, in 2009, the International Commission on Radiation Units and Measurements (ICRU) and ICRP jointly published adult reference computational phantoms based on detailed CT data of individuals as ICRP Publication 110 (based on reference human anatomical and physiological data for use in radiation protection given in ICRP Publication 89 2002). Computational phantoms for other ages are under development by ICRP. These phantoms are given the special name of Voxel phantoms.

The gastro-intestinal (GI) tract model of ICRP Publication 30 (1979) was improved as the Human Alimentary Tract Model (HATM) in ICRP Publication 100 (2006). The HATM provides age-dependent and gender-dependent (in adults) dimensions of the alimentary tract regions and transit times for the movement of materials through these regions.

During the period, 2011-12, ICRP produced three draft reports for consultation on "Occupational Intakes of Radionuclides." These reports included improvement in the Human Respiratory Tract Model taking into account more recent data and the development of the HATM. This series of reports also contained a model for uptake via wounds based on National Council on Radiation Protection and Measurements (NCRP) Report number 156 (2007). In addition, information has been provided on absorption to blood following inhalation and ingestion of different chemical forms of elements and their radioisotopes. Revisions have been made to many models for the systemic bio-kinetics of radionuclides absorbed to blood, making them more physiologically realistic representations of uptake and retention in organs and tissues and of excretion. The series provides the above data for the following elements : h0 ydrogen (H), carbon (C), phosphorus (P), sulphur (S), calcium (Ca), iron (Fe), cobalt (Co), zinc (Zn), strontium (Sr), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo) and technetium (Tc), ruthenium (Ru), antimony (Sb), tellurium (Te), iodine (I), cesium (Cs), barium (Ba), iridium (Ir), lead (Pb), bismuth (Bi), polonium (Po), radon (Rn), radium (Ra), thorium (Th), and uranium (U). The revised dose coefficients based on the recommendation in ICRP Publication 103 using the new computational phantoms and improvements in the bio-kinetic parameters are being computed by ICRP.

Meanwhile, ICRP published "Compendium of Dose Coefficients based on ICRP Publication 60" as ICRP Publication 119 (2012). This provides the dose coefficients estimated with an improved treatment of the radioactive progeny produced within body following intake of radionuclides, treatment of gases and vapors and improved nuclear decay data published as ICRP Publication 107 (2008).

ISO 27048 (2011) is an international standard on the measurement of bioassay data (using both direct and indirect monitoring). It includes procedures for dose assessment based on reference levels for routine and special monitoring programs; assumptions for the selection of dose-critical parameter values; criteria for determining the significance of monitoring results; interpretation of workplace monitoring results; uncertainties arising from sampling, measurement techniques, and working conditions; interpretation of multiple data arising from different measurement methods at different times, handling data below the decision threshold, rogue data, and calculation of doses to the embryo/fetus and infant; reporting/documentation; quality assurance.

All these changes will lead to more realistic measurements, internal dose estimation and occupational dose management.




 

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