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Home | Current Program | PAC 6 | SC 6-3SC 6-3: Uncertainties in Internal Radiation DosimetryThe primary goal of this Committee, formed in September 2005, is to provide a definitive analysis of uncertainties in internal dosimetry, including uncertainties in measurements of input parameters for breath, urine, feces, blood and tissue samples, uncertainties in multi-pathway modeling of radionuclide retention and distribution in the body, and overall uncertainty analysis for the final estimate of internal radiation dose for a given exposure scenario. The members provide a combination of expertise in measurements, modeling, and statistical analysis of overall uncertainty for a combination of input parameters and model pathways, each of which may have different probability distributions. Scientific Committee 6-3 held two meetings during the fourth quarter of 2005. The first meeting was held on November 3-4, 2005 for the purpose of defining the scope of the report and its contents. During this meeting, the Committee members decided that the report will address uncertainties in internal dosimetry for environmental, occupational and medical scenarios, and include both retrospective and prospective assessments. Multiple examples involving commonly encountered radionuclides will be provided to illustrate the challenges in assessing and reporting uncertainties in internal dosimetry. A second meeting was held on December 15-16, 2005. During this meeting, presentations were made outlining some of the challenges in estimating uncertainty in internal dose estimates. Since another NCRP committee will be addressing uncertainties in determining radiation risks, the Committee also decided to limit its focus to the estimation of uncertainties in determining internal absorbed dose and not to consider the uncertainties associated with the determination of radiation- and tissue-weighting factors. Scientific Committee 6-3 held a meeting on July 6-7, 2006 in Oak Ridge, Tennessee. Following a discussion of the available documents and work already done by some of the Committee members, an extended outline was developed. Inputs from each author were provided to the NCRP Staff Consultant by October 20, 2006 and all contributions were integrated into a draft report that was discussed and refined at a November 2-3, 2006 meeting in Albuquerque, New Mexico. An expanded outline of the report was developed at the SC 6-3 Committee meeting on November 2-3, 2006, and was used by the Chairman to further refine working assignments for the following sections of the report:
The persons in charge of each section were given the responsibility to organize the preparation of their sections and subsections. A meeting of the statistical subgroup was held on January 25-26, 2007 at SENES in Oak Ridge, Tennessee. The purpose of the meeting was to reach agreement on the contents of the report related to the statistical aspects of uncertainty assessment and to assign responsibilities for developing needed statistical sections. First drafts were prepared by March 15, 2007, and were shared with the statistical subgroup. Subgroup comments on the draft sections were returned by March 30, 2007. Complete drafts of all updated sections of the report were provided to the NCRP Staff Consultant by March 30, 2007. This allowed sufficient time for the draft report to be prepared for the SC 6-3 meeting that was held on April 18-19, 2007 following the 2007 NCRP Annual Meeting at the Crystal City Marriott, Arlington, Virginia. At the SC 6-3 Committee meeting, progress was made in expanding upon the statistical subgroup Section 4 addressing “Types and Categories of Uncertainty” and Section 5 dealing with “Bayesian and Other Statistical Methods for Estimating Uncertainties.” Sections were addressed in more detail that involved missing medical and environmental inputs and assignments were made to expedite the preparation of these sections. A more detailed plan forward for each section was developed during the meeting and provided to the Committee by the Chairman. Prior to the October 9-10, 2007 SC 6-3 meeting, updates of Section 3 and 7 were integrated. An updated draft SC 6-3 report was posted on the SC 6-3 website on September 20, 2007 for full Committee member review. The SC 6-3 meeting was held at SENES Oak Ridge, Tennessee. Important gaps noted at the meeting were: (1) medical team inputs for Sections 3.2.3 and 3.3.3, and Section 6.3; (2) the need to develop a clear indication of the situations where uncertainty analysis is necessary; (3) the need to include recommendations on the methods of uncertainty analysis to be used in specific situations; (4) uncertainty in intakes derived from environmental concentrations; and (5) a clear presentation of what the report is expected to accomplish and to whom it is to be addressed. In preparation for an SC 6-3 meeting held in Richland, Washington on December 18-20, 2007, significant updates were provided by Committee members which resulted in: (1) a new section in 3.2.1 that discusses the NCRP Wound Model Report No. 156; (2) an extensive rewrite of Section 4; (3) significant expansion of Section 5 to incorporate issues discussed as being needed by the statistical subgroup, including moving toward consensus on Section 5.5; (4) update of the front end of Section 6; and (5) rewrite of Section 7 to address issues raised at the last meeting and to add additional radionuclide systemic models. Section 7 also provides a table, and accompanying narrative text on proposed estimates of uncertainty that addresses uncertainty in dose per unit intake for selected radionuclides and applications. All these changes were incorporated by the NCRP Staff Consultant, and a revised draft was provided to the Committee members along with an extensive update of the Section 11 references on December 11, 2007. The main result of the discussions of the December 18-20, 2007 meeting was that the report should be streamlined and reorganized in such a way that the main text would be reduced in length and that much of the existing material would be put in appendices. Assignments were made regarding the persons responsible for the preparation of the revised sections and appendices; critical reviewers were also selected for all parts of the report. Dr. Bouville’s notes sent to the Committee members on December 23, 2007 set a date of March 1, 2008 as the deadline for completion of all missing parts and revised sections as well as submission of appendices text. On March 3, 2008, an SC 6-3 interim report on the status of the draft report was forwarded to NCRP. This was also shared with the Committee members with an urgent request to review the document and to provide the needed inputs from those identified as responsible for each section, subsection or appendices. On March 6, a conference call was held with Dr. Bolch and a new agreement was reached to receive the medical team input by April 5. Email between the medical team members has significantly increased and initial drafts of some subsections and case examples have been shared. Other Committee members were given until March 24 to submit their section, subsection and appendices updates. An important revision and shortening of Section 5 was received and has been incorporated into the draft report. Some of Section 5 was moved to Appendix H to streamline and shorten Section 5. The first draft of the new Section 7 also was received. By the first week of April, significant upgrades to Section 8 will be received that will shorten and reorganize that section and will develop data that can go into the appendices. In order to further achieve this reorganization process to produce shorter front section text and a more readable and useable report on some of the Bayesian statistical methods, NCRP scheduled a meeting of several Committee members on April 15 after completion of the 2008 NCRP Annual Meeting. This SC 6-3 meeting led to final decisions on the planned reorganization strategy of the draft report, so that all received inputs could be incorporated by April 30, 2008. The report was then shared with all Committee members in time for an intensive review in preparation for an SC 6-3 meeting on May 14-15, 2008 in Bethesda, Maryland, where final updates and revisions were discussed and integrated into the draft SC 6-3 report. On May 30, 2008, a new draft of the SC 6-3 report was distributed by Tom Bell to all Committee members. A copy was also provided to NCRP, Dr. Tenforde, for an initial review prior to finalization by Dr. Bouville. NCRP received the final draft SC 6-3 report (dated June 12, 2008) by a mailed CD on June 17, 2008 indicating that this draft might be distributed to PAC and expert reviewers in June 2008. The 40 MB file was too big to transmit by e-mail. On June 24, 2008, Dr. Tenforde distributed a PDF copy of the June 12, 2008 draft and requested that a peer review be provided by Friday, August 1, 2008. He asked that the review focus on the technical content of the report, since NCRP staff was in the process of making formatting refinements and validating references. The draft report was e-mailed on June 24, 2008 to: Drs. Bailey, Beck, Groer, Nosske, Racine-Poon, and Stram. A teleconference with SC 6-3 members was held on September 15, 2008 to discuss progress on addressing peer review comments. A comment resolution matrix was developed to document resolution of comments and recommendations. Web conference calls followed on October 6, October 30, and November 6, 2008, to assist in finalizing all needed changes made by the Committee members in response to the comments received from the peer reviewers. A final draft of the SC 6-3 draft report was prepared and forwarded to NCRP on December 2, 2008. It is now in the process of being finalized in preparation for forwarding to Council members in the first quarter of 2009 for their review. The membership of SC 6-3 is:
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