Program - Single Session

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Basics of Internal Dosimetry

Monday 02/06/2023

Room: Memorial Union 49

08:00 - 10:15

Chair(s): Deepesh Poudel, Cheryl Antonio

MAM-A.1  08:00  Internal Dosimetry Program - Considerations and Challenges. Potter C*, Sandia National Laboratories

The determination of internal dose in the form of committed effective dose is required nationally and internationally as part of an occupational radiation protection program. Determination of internal dose is not straightforward because in vivo measurements can sometimes have considerable uncertainty, in vivo measurements can be greatly affected by the individual’s metabolism, and the evaluation of the data requires understanding of complex models and associated mathematics. Models change periodically, which requires reevaluation of analysis methodologies and, in some cases bioassay methods used. In addition, federal requirements for internal dosimetry programs, action levels for bioassay and response, and dose limits can change over time. Such conditions require interactions between the internal dosimetry program and regulators, ensuring agreement in this changing environment. All of these considerations make the field of internal dosimetry interesting and challenging, stressing the importance of having a comprehensive and competent program.

MAM-A.2  08:30  Criteria for Individual Monitoring and Selection of Monitoring Method: A Case Study. Khalaf Majid H.*

This case study provides criteria for individual monitoring and selection of monitoring method case study.This case study provides an introduction about the need for an internal dosimetry program and the need for participation in a routine internal dose monitoring study will detailed a group of workers handling dispersible radioactive materials and to answer the following questions; -Is routine monitoring required? -Can any procedures be implemented to avoid the need for individual monitoring? -Which individual monitoring method should be selected for Pu-239 and Am-241? -Does routine monitoring of Pu-239 by urinary and fecal analysis have adequate sensitivity and which monitoring intervals are the appropriate? -Does routine monitoring of Am-241 by lung monitoring have adequate sensitivity? -Does urine and feces routine monitoring of insoluble forms of Pu-239 have adequate sensitivity?

MAM-A.3  08:45  INTERNAL DOSIMETRY INTERCOMPARISON PROGRAM (DICE). Antonio Cheryl*, HMIS; Rosenberg Brett L., Sandia National Laboratories   CHERYL_L_ANTONIO@RL.GOV

In 2020 an internal dosimetry intercomparison (DICE) program was initiated in the U.S. to allow internal dosimetrist an opportunity to see how their methodologies for calculating intakes and doses compare within the internal dosimetry community. The program was modeled off the European Radiation Dosimetry Group’s (EURADOS) 2017 Intercomparison on Internal Dose (ICIDOSE 2017). DICE was intended to showcase how dosimetry programs utilize available bioassay data, models, and software to achieve a final dose assessment. The two cases evaluated in 2020 involved an inhalation of a plutonium mixture and a depleted uranium inhalation. The cases evaluated in 2022 involved a plutonium mixture contaminated wound and a tritium exposure. Participation was individually or as an organization/department. An evaluation report of each case from 2020 and 2022 will be presented showing a compilation of the results and methods used by the participants.

MAM-A.4  09:00  Where Did This Come From? Lessons Learned from High-Routine Bioassay Investigations. Antonio Cheryl*, HMIS; Carbaugh Eugene H, Retired   CHERYL_L_ANTONIO@RL.GOV

High routine bioassay results can come from several sources, including normal statistical fluctuation of the measurement process, interference from non-occupational sources, and previous occupational intakes, as well as new intakes. A good internal dosimetry program will include an investigation process that addresses these alternatives and comes to a reasonable conclusion regarding which is the most likely source of the detection. A subtle nuance to these investigations is the possibility that a newly detected positive measurement might represent an old intake that has only now become detectable. It is incumbent upon the site performing a high bioassay result investigation to thoroughly address the possible alternatives or face the consequence of accepting responsibility for a new intake. The presenter has encountered all of the foregoing issues in the course of investigating high routine bioassay measurements at the US Department of Energy Hanford Site. The important lessons learned include, 1) have good measurement verification protocols, 2) confirm intakes by more than one bioassay measurement, 3) conduct interviews with workers concerning their specific circumstances and recollections, 4) have good retrievable site records for work history reviews, 5) exercise good professional judgment in putting the pieces together to form a conclusion, and 6) clearly communicate the conclusions to the worker, the employer, and the regulatory agency.

MAM-A.5  09:15  Internal Dose Calculations for Nuclear Medicine Applications. Stabin M*

Internal dose calculations for nuclear medicine applications are based on the well-established concepts and units, as defined by the RAdiation Dose Assessment Resource (RADAR) Committee of the Society of Nuclear Medicine and Molecular Imaging. The RADAR method harmonized the defining equations and units employed to provide quantitative analysis for both nuclear medicine and occupational internal dose calculations. This program will show, from a practical standpoint, how data are gathered and dose calculations are performed in nuclear medicine applications, showing practical examples to solve different problems. An overview will be given of the current state of the art in the use of internal dose calculations in nuclear medicine therapy, and the promise for future improvements to provide more patient specificity in calculations (in therapeutic applications) and better ability to predict biological effects from calculated doses.

MAM-A.6  09:30  A Dosimetrist’s Role in Emergency Response. Rosenberg Brett L*, Sandia National Laboratories

This presentation will identify how important it is for there to be streamlined and effective communication between the field, a dosimetrist, and involved workers in emergency response situations. Examples will be provided of what happens when communication drops, the impact of sharing too much information, and the value of being a point of contact for appropriate monitoring. The field may need verification from a dosimetrist if an intake occurred, and if workers can continue supporting a job that has the potential for additional exposures. Discussions will include scenarios involving medical intervention and the role a dosimetrist should play relative to a physician.

MAM-A.7  09:45  Low-Level Detections – Statistics and Consequences. Rosenberg Brett L*, Sandia National Laboratories

One of the toughest parts of a dosimetry program is setting the criteria on which an occupational intake is determined. This can be further complicated by the presence of the same radionuclides in the environment. There are several things to consider when determining if there is a detection, including the potential follow-up required, the illusion of ‘result shopping,’ and what the data may look like to someone looking back on the records decades later. This presentation will address some of the philosophies dosimetrists may adopt when determining an intake and the appropriate follow-up.

MAM-A.8  10:00  A Brief Introduction to Biokinetic Model Development. Samuels Caleigh*, ORNL Center for Radiation Protection Knowledge; Leggett Rich, ORNL Center for Radiation Protection Knowledge

Biokinetic models are mathematical representations of the time-dependent distribution and retention of internally deposited radionuclides in the respiratory and alimentary tracts and in systemic pools after absorption to blood. These models allow the calculation of the rate of nuclear transformations occurring within specific tissues and the rate of excretion of radionuclides as a function of time, thereby enabling organ dose estimates and providing a means of interpreting bioassay data. Modern biokinetic models generally incorporate biologically realistic structures describing the paths of movement of radionuclides within the body and along excretion pathways. Types of information used to develop rates of transfer of radionuclides between model compartments include physiological data, physical laws, element-specific biokinetic data developed in controlled studies of the fate of the element of interest or biokinetic analogues in human subjects or laboratory animals, studies of human subjects accidentally exposed to radionuclides, autopsy data describing the distribution of elements in the human body, and data from medical procedures involving radiopharmaceuticals. In this talk we will discuss recently developed models, including a model for sodium and models for Group 4b elements, as illustrations of different model formulations and types of data used to develop structures and parameter values for specific models.

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