PowerPointPrsentation

1
General Guidelines for the Assessment of Internal
Dose from Monitoring Data (Project IDEAS)
 
H. Doerfel, FZK, Karlsruhe A Andrasi, KFKI,
Hungary M Bailey, J Marsh, J Stather, NRPB, UK V
Berkovski, RPI, Ukraine C-M Castellani, ENEA,
Italy C Hurtgen, SCKCEN, Belgium J-R Jourdain, E
Blanchardon, I Laniece, IRSN, France B LeGuen,
EDF, France I Malatova, RPI Czech Rep.
(corresponding member) R Cruz-Suarez, J Zeger,
IAEA (corresponding members)
2
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Background
Monitoring data
Intake Committed Dose

• Assumptions
• Pathway of intake
• Time course of intake
• Biokinetic Model(s)
• Parameter values for material subject

General experience When a set of bioassay data
is given to two different assessors, it is likely
that different assumptions will be made, and
perhaps different methods applied and therefore
that different results will be obtained.

• Influencing factors
• Amount and quality of data
• Skill and experience of the dosimetrist
• Computational tools available

3
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
What we have learned from recent intercomparison
exercises
 
There is a clear need to develop guidelines on
assessments of intake and internal doses, in
order to promote harmonisation in assessments,
especially, but not only, across the EU.
Such guidelines have formed the core of the IDEAS
project.
4
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Presentation to Intercomparison Workshop 18 April
2005
 
1 The IDEAS Project
2 The IDEAS guidelines
5
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
The project
Cost-shared action in 5th FP 42 Months October
2001 March 2005 (extended to June 2005, to
co-ordinate intercomparison exercise with IAEA
and this Workshop with IM 2005)
 
The aims
To develop guidelines to standardise assessments
of internal doses
By application of such guidelines, different
assessors should obtain the same result from the
same data
6
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Survey of open literature
Work package 1 Collection of incorporation
cases (C. Hurtgen)
Contacts with industry and research institutions
 

• Bibliographic database
• Compilation of references (author, year, title,
  journal)
• Content 547 references (mainly Health Phys.
  (229), Rad. Prot. Dos. (60))

• Incorporation case database
• Detailed information (case description,
  monitoring results, dose assessment)
• Content 209 cases

Selection of cases for assessment by consortium
(WP3)
7
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Work package 1 Collection of incorporation cases
Investigate improved mathematical methods to
assess intakes from monitoring data
 
Implement in existing software (IMIE RPI)

• Implementation of new features
• Mixed fractions of pathway of intake
  (inhalation, ingestion, injection)
• Mixed fractions of absorption types (F, M and S)
• Wound simulated as chronic injection and/or
  multiple injection
• AMADs up to 20 micron
• Import of individual retention and excretion
  functions

Work package 2 Preparation of evaluation
software (V. Berkovski)
8
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)

• Evaluation of 52 cases (29 of them by 2 or more
  evaluators)
• Application of both IMIE and IMBA ExpertTM
• Selection of the best estimates
• Identification of important issues related to the
  guidelines

Work package 1 Collection of incorporation cases
 
Work package 3 Evaluation of incorporation
cases (C-M. Castellani)

• Evaluation database
• Compilation of all information (Word and Excel
  files)
• Content 95 independent evaluations of 52 cases

Work package 2 Preparation of evaluation software
Identification of factors and assumptions for
which guidance is needed
9
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Work package 1 Collection of incorporation cases
Work package 4 Development of general
guidelines (H. Doerfel)
Develop common approach for evaluation of
monitoring data
 
Consider data handling (intake pattern, multiple
data sets, errors, rogue data etc.)
Work package 3 Evaluation of incorporation cases
Develop draft guidelines based on Workshop
discussions
Work package 2 Preparation of evaluation software
Discuss with experts in open Virtual Workshop
(1) on the Internet
Prepare report on draft guidelines
10
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Work package 4 (Development of general guidelines)
 
Details and discussion in Part 2 of presentation
(later)
11
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Virtual workshop for discussion of the guidelines
with the community
Special webpage (www.ideas-workshop.de) for
posting the guidelines
 
Discussion forum for every stage of the
guidelines where anyone could place his (or her)
comments
Announcement of the workshop through contacts,
relevant national and international organisations
etc. (including IRPA Madrid)
Start of the workshop on 31 May 2004 end is
still open
12
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Virtual workshop for discussion of the guidelines
with the community
Statistics of the visits of the website
(www.ideas-workshop.de)
 
13
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Virtual workshop for discussion of the guidelines
with the community
Statistics of the visits of the discussion forum
 
14
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Virtual workshop for discussion of the guidelines
with the community
Special webpage (www.ideas-workshop.de) for
posting the guidelines
 
Start of the workshop on 31 May 2004 end is
still open, Continuation, linked to CONRAD FP6
Project (Carlo-Maria Castellani Hans Doerfel)
Develop guidelines further
Information exchange for internal dosimetry
community
15
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Work package 1 Collection of incorporation cases
Work package 4 Development of general guidelines

• Organise Joint Intercomparison Exercise on
  Internal Dose Assessment together with IAEA
• Prepare, distribute cases guidelines
• Compile results

 
Work package 3 Evaluation of incorporation cases
Workshop (2) with participants to discuss results
Work package 5 Practical testing of general
guidelines
Work package 2 Preparation of evaluation software
Modify draft guidelines according to results of
discussion
Publish report and General Guidelines
16
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Work package 4 (Development of general guidelines)
General philosophy based on the evaluation (Work
package 3)
 
Levels of task based on general philosophy
General guidelines for the evaluation based on
Level of task structure
17
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
General philosophy
Harmonisation by following the procedures any
two assessors should obtain the same estimate of
dose from a given data set
 
Discussion point? Sometimes there is conflict
between these principles. Which has priority?
Best estimate the best estimate of dose
should be obtained from the available data
Proportionality the effort applied to the
evaluation should be proportionate to the dose
the lower the dose, the simpler the process
should be.
18
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)

• processing of data before use,
• handling of single data and multiple data sets,
• number and type of data required for the dose
  assessment
• assessment of the uncertainty on data,
• handling of data below the limits of detection,
• handling of data influenced by chelation therapy
• and the identification of rogue data

The general guidelines provide
 
Detailed information about data handling
General information about the evaluation of the
monitoring data reflecting the general philosophy
Structured approach to the dose assessment
reflecting the levels of task.
19
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Levels of task
Level 0 Annual dose lt 0.1 mSv No evaluation of
dose needed. (German Swiss Guidelines, external
doses rounded)
 
Level 1 Dose from the intake typically 0.1 1
mSv Simple, reference evaluation, with ICRP
defaults used for all parameter values, except
where there is better a priori information
available
Level 2 Dose from the intake typically 1 6
mSv Sophisticated evaluation using additional
information to give more realistic assessment of
dose Adjustment of AMAD, absorption type or the
time of intake if unknown (A posteriori using
measurement data)
Level 3 Dose from the intake typically gt 6
mSv More sophisticated evaluation, which applies
to cases where there are comprehensive data
available Systematic adjustment of the model
parameter values (step-by-step approach), until
the fit is acceptable (not rejected)
20
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Stage 1 (Level 0)
Single routine measurement, M Compare with
tabulated value MC If measurement Mlt MC implies
Annual dose (committed effective dose from
intakes in year) lt0.1 mSv assuming similar
intakes in all monitoring intervals. Record dose
0.0 mSv. Record measurement. STOP
 
21
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Structured approach to dose assessment
Stage 1 Check of the need for evaluation
 
22
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Stage 1 (Level 0) Step 1.1
 
Identify measurement (M) and duration of
monitoring interval (T) Data treatment (if
needed) Other radionuclides present as well as
Indicator that was measured?
23
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
 
24
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Step 1.2 Example of the critical monitoring
quantity Mc
 
25
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Stage 2 (Level 1)

• Measurement MgtMC
• Check whether M is significant
• Need realistic estimate of uncertainty
• If so reference procedure (ICRP 78) Default
  values, a priori parameter values, route of
  intake, etc.
• If annual dose lt1 mSv (record dose) STOP

 
26
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Structured approach of the dose assessment
Stage 1 Check of the need for evaluation
 
Stage 2 Check of the significance of measurement
and consistency with previous evaluations
27
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Stage 2 (Level gt0) Step 2.1

• Assess overall uncertainty on measurement
• New intake?
• Consistent with previous intakes?
• (Rogue point inconsistent with other data?)
• (Weighting in fitting more than one measurement)
• (Objective criteria to determine whether model
  fits data)
• (Objective criteria to choose between models)

 
28
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Stage 2 (Level gt0) Step 2.1

• Assess overall uncertainty on measurement for
  comparison with model (Scattering Factor, SF)
• Type A (Poisson counting statistics) and Type B
  (other)
• Measurement of activity in sample (or in organs)
  and its use to estimate modelled activity (e.g.
  daily excretion rate), sampling errors,
  biological variability

 
29
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Stage 2 (Level gt0) Step 2.1

• Guidance on estimating SF
• Log-normal. Not exact, but pragmatic (approximate
  better than nothing, or only some contributions)
• Some details available for in vivo measurements
• General defaults (Table 2.3, Guthrie Miller)
  excretion etc. based on plutonium.

 
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Step 2.1 Default values for the components of
log-normal uncertainty for various types of
measurement

• Discussion point!!!
• excretion etc. based on plutonium.
• Need more typical SF for other radionuclides -
• contributions please!!!

31
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
 
Discussion Point! P/SF2ltMltPSF2 chance of false
intakes or inconsistency gt30 Use eg SF2 ?
32
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
 
33
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Stage 3 (Level gt 0) Standard evaluation

• Measurement M due to new intake
• Confirm routine (not special, Stage 4)
• Reference assumptions, as ICRP 78, eg. single
  intake (inhalation) at mid-point
• Parameter values related to material (eg AMAD) if
  known before (a priori)
• If annual dose lt1 mSv record and STOP

 
34
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Structured approach of the dose assessment
Stage 1 Check of the need for evaluation
 
Stage 2 Check of the significance of measurement
and consistency with previous evaluations
Stage 3 Standard reference evaluation procedure
35
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Structured approach of the dose assessment
Stage 1 Check of the need for evaluation
 
Stage 2 Check of the significance of measurement
and consistency with previous evaluations
Stage 3 Standard reference evaluation procedure
Stage 4 Special evaluation procedure
Identification of pathway of intake
36
Stage 4 Special Assessment
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Room air contamination (Default)
External contamination
Room air and external contamination AND
justification

• Discussion point!
• Understand the case
• Plot graph of data
• Hand calculation?

37
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Stage 5 Special Assessment Inhalation Stage
5A Initial evaluation using a priori parameters
Stage 5B Varying the AMAD, absorption type
and/or time of intake, if not known, using the
data
Stage 5C Systematic adjustment of model
parameters (HRTM, HAT) until fit is acceptable
38
Stage 5A Special assessment Inhalation Standard
evaluation As Stage 3, but gt1 measurement
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
5.5 Calculate intake (dose?) Ii from each
measurement Mi Best estimate mean (Ii)

• 5.4
• Routine measurement
• inconsistent with previous or
• standard evaluation, dose gt1 mSv

 

• 5.6 If dose from intake lt1 mSv,
• (for every measurement type)
• (for every radionuclide)
• Record and STOP

39
Stage 5B Special assessment Inhalation vary
AMAD, F/M/S, Time of intake
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Stages 5A 5B select parameter values by
fitting model predictions to the data
Procedure stops when model fits, i.e. data do not
reject model. Easy if few data, hence steps 5.6,
5.11.4, 5.12.4 Are there enough data ? Depends
on dose
40
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Criteria for rejecting fit Discussion Point!!!
 

• Model should fit data for unbiased estimate
• Proposed criteria for rejecting fit
• Chi-squared test statistic 1 level if dose lt6
  mSv 5 level if dose gt6 mSv OR
• Fit looks unreasonable by eye (series of data
  under- or over-estimated.

41
Number and type of data needed for assessment of
dose for selected radionuclides and monitoring
procedures

• Discussion point!!!
• This is only a start (place-holder)
• Help is needed to
• confirm (or improve)
• extend to other situations
• Hopefully workplace monitoring will ensure that
  sufficient data are available.

42
Stage 5B Special assessment Inhalation vary
AMAD, F/M/S, Time of intake
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
43
Stage 5B Special assessment Inhalation vary
AMAD, F/M/S (Time of intake)
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Step 5.8 time of intake known

• Main effect of AMAD is partition between
• upper respiratory tract (ET, BB, bb) mostly early
  fecal excretion
• lower respiratory tract (AI) mostly lung
  retention
• Hence estimate effective AMAD

44
Stage 5B Special assessment Inhalation vary
AMAD, F/M/S (Time of intake)
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)

• Main effect of AMAD is partition between
• upper respiratory tract (ET, BB, bb) mostly early
  fecal excretion
• lower respiratory tract (AI) mostly lung
  retention
• Hence estimate effective AMAD

Relatively insoluble materials Ratio of early
fecal excretion to lung retention (day 3) for
Am-241 Could extend to other situations
45
Stage 5B Special assessment Inhalation vary
AMAD, F/M/S (Time of intake)
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Step 5.8 time of intake known
Step 5.11 Fit absorption type A priori assignment
based on chemical form (Step 5.3) Check
goodness of fit (Step 5.11.1). If fit rejected
try other Types (F/M/S)
46
Stage 5B Special assessment Inhalation vary
AMAD, F/M/S (Time of intake)
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Step 5.8 time of intake known
Steps 5.11.12 Model fits data, if dose lt6 mSv
record dose and stop.
Steps 5.11.4 Enough data for 6 mSv?
Step 5.13 If fit rejected or additional data, try
mixture of Types (F/M/S)
47
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Stage 5B Special assessment Inhalation vary
(AMAD), F/M/S Time of intake
Discussion point!!! If model fits, then probably
several sets of parameter values (intake times
and mixtures of absorption Types) will fit. Not
straightforward to harmonise best fit with two
variables. Needs more work.
Step 5.8 time of intake unknown (Cannot
determine effective AMAD)
Step 5.12 Simultaneous fit of time of intake and
absorption. If model fits data, and if dose lt6
mSv record dose and stop.
Step 5.12.4 Enough data for 6 mSv?
Step 5.14 If fit rejected or additional data, try
mixture of Types (F/M/S)
48
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Stage 5C Advanced evaluation

• Vary parameter values in order check fit after
  each step
• HRTM absorption parameters (fr, sr, ss)
• GI tract absorption f1
• HRTM particle transport parameters
• GI tract transit
• Systemic biokinetic model

 
49
General guidelines for the estimation of
committed dose from incorporation monitoring
data (Project IDEAS)
Development of Guidelines
1. IDEAS refine from outcome of the exercise,
and discussions at the Workshop. Publish summer
2005.
 
2 ICRP Guidance Document to accompany revision
of publications 30/54/68/78. Publish 2007?
3 IDEAS web site. CONRAD 2005-2007. FP7? Another
exercise around 2007-8?