Curso de refresco CR-7: Dosimetría Interna

Transcription

1 X Congreso Regional Latinoamericano IRPA de Protección y Seguridad Radiológica Buenos Aires, de abril de 2015 Curso de refresco CR-7: Dosimetría Interna AUGUSTO GIUSSANI

2 BfS - Federal Office for Radiation Protection Department of Radiation Protection and Health agiussani@bfs.de

3 Curso de refresco en dosimetría interna. Models and phantoms for internal dosimetry. The EURADOS IDEAS guidelines for estimation of doses from incorporation monitoring data.

4 Internal exposures.

5 Internal dose is evaluated with mathematical models. Intake Time-activity curves in the source regions Number of nuclear transformations Biokinetic Model Dosimetric Model Internal Dose DOSE COEFFICIENTS e(50)

6 Internal dosimetry. Biokinetics D ( r T, t) A r r S, tsr r, t S T S Physics + Anatomy S r r, t Y E ( r T S 1 M ( r T, t) i i i T r S, E i, t) Anatomy Physics Nomenclature according to Bolch et al., JNM 50:477-84, 2009

7 Skin Skin Compartmental models are used to describe routes for intake, retention and excretion. Inhalation Extrinsic removal Exhalation Ingestion Respiratory Tract Model Sweat Wound Lymph nodes Direct absorption Subcutaneous tissue Other organs Transfer compartment Entry into blood Liver Kidney Urinary bladder Alimentary Tract Model (GI-Tract) Faeces Urine

8 The ICRP30 Series presented simple, nonrecycling compartmental models. ICRP Publication 30 (Part 1) Ann ICRP 2 (3-4), 1979 Limits on intakes of radionuclides by workers da rs, t i ks A r i i S, m dt, t k Ar t out Si Sm S m kt, t a e A r S i k k

9 Biokinetic models starts getting more sophisticated. ICRP Publication 56, Ann. ICRP 20(2), 1990 Age-dependent doses to members of the public from intake of radionuclides Part 1

10 Biokinetic models starts getting more sophisticated. ICRP Publication 67, Ann. ICRP 22(3-4), 1992 Age-dependent doses to members of the public from intake of radionuclides Part 2 Ingestion dose coefficients

11 The changes introduced by the 1990 recommendations call for more detailed models. ICRP Publication 60, Ann.ICRP 21(1-3), recommendations of the International Commission on Radiological Protection

12 In the 2007 recommendations even more tissues have specific weighting factors. Tissue or organ Tissue weighting factor (w T ) ICRP60 ICRP103 Gonads Bone marrow (red) Colon Lung Stomach Bladder Breast Liver Oesophagus Thyroid Skin Bone surface Brain 0.01 Salivary glands 0.01 Remainder E T H H M rem F rem w T H M T T T H 2 H H M T F T F T

13 The characterisation of complex, realistic models requires availability of reliable data. New ICRP Publication series on Occupational Intakes of Radionuclides (OIR) - available from late 2015 (?).

14 The characterisation of complex, realistic models requires availability of reliable data. From To Transfer coefficient Transfer coefficient (d -1 From To ) (d -1 ) Plasma Red blood cells 1.8 Spleen Plasma 5.03 Plasma Skeletal muscle 30.0 Spleen Liver Plasma Liver 19.5 Pancreas Plasma 1.68 Plasma Kidneys 67.1 Pancreas Liver Plasma Spleen 5.30 Skin Plasma Plasma Pancreas 1.77 Skin Excreta Plasma Skin 4.42 Adipose tissue Plasma 1.77 Plasma Adipose tissue 8.83 Brain Plasma Plasma Brain Heart wall Plasma 8.07 Plasma Heart wall 14.1 Lung tissue Plasma 1.47 Plasma Lung tissue 4.42 Red marrow Plasma Plasma Red marrow 5.3 Cartilage Plasma 0.2 Plasma Cartilage 3.0 Trabecular bone surface Plasma Plasma Trabecular bone surface 1.59 Cortical bone surface Plasma Plasma Cortical bone surface 1.06 Stomach wall Plasma 4.16 Plasma Stomach wall 3.53 Stomach wall Liver Plasma Stomach content 4.52 Stomach wall Stomach content 0.21 Plasma Small intestine wall 35.3 Small intestine wall Plasma 9.87 Plasma Small intestine content 1.05 Small intestine wall Liver Plasma Right colon wall 5.65 Small intestine wall Small intestine content 0.21 Plasma Right colon content 0.02 Right colon wall Plasma 6.86 Plasma Left colon wall 5.65 Right colon wall Liver Plasma Rectosigmoid colon wall 2.83 Right colon wall Right colon content 0.21 Plasma Other Left colon wall Plasma 6.86 Plasma Other Left colon wall Liver Red blood cells Plasma Left colon wall Left colon content 0.21 Muscle Plasma Rectosigmoid colon wall Plasma 6.86 Liver Plasma 2.14 Rectosigmoid colon wall Liver Liver Small intestine content Rectosigmoid colon wall Rectosigmoid colon content 0.21 Kidneys Urinary bladder content 1.68 Other 1 Plasma Kidneys Plasma 31.9 Other 2 Plasma

15 There are situations where greater physiological realism is required. DTPA DTPA DTPA log K log K log K Pucitrate PuDTPA Putransferrin log log Pu ci trate Pu ci trate Pu trans ferri n Pu trans ferri n Pu DTPA 29.5 Pu DTPA log Urine Schimmelpfeng et al., Radiat. Prot. Dosim. 136:74-81 (2009) Kastl et al., Int.J.Radiat.Biol., 90: (2014)

16 There are situations where greater physiological realism is required. Pu + DTPA Pu-DTPA Three compartmental systems x[]: Compartments of the DTPA model y[]: Compartments of the Pu model z[]: Compartments of the Pu-DTPA chelate model Kinetics of the second order: Breustedt et al., Health Phys. 99: (2010) Kastl et al., Int.J.Radiat.Biol., 90: (2014)

17 Introducing physiological considerations in the compartmental model. Kastl et al., Int.J.Radiat.Biol., 90: (2014)

18 New models of respiratory and alimentary tract include age- and sex-specific features. ICRP Publication 30 (Part 1) Ann. ICRP 2 (3-4), 1979 ICRP Publication 100, Ann. ICRP 36 (1-2), 2006 Human alimentary tract model for radiological protection

19 New models of respiratory and alimentary tract include age- and sex-specific features. Extrathoracic ET 1 Environment Extrathoracic bb 2 bb 2 LN ET ET seq ET 2 GI tract ET 2 ET seq LN ET BB seq BB 2 BB 1 BB seq BB 2 BB 1 s pt LN TH bb seq bb 2 bb 1 LN TH bb seq bb 2 bb 1 Thoracic AI 3 AI 2 AI 1 Thoracic AI 3 AI 2 AI 1 Initial f b s p bound f b s t Transformed (1-f b )s p s b (1-f b )s t Blood ICRP Publication 30 (Part 1) Ann. ICRP 2 (3-4), 1979 ICRP Publication 66, Ann. ICRP 24 (1-3), 1994 Human respiratory tract model for radiological protection

20 The new structures are physiologically more realistic. Extrathoracic ET 1 Environment LN ET ET seq ET 2 GI tract BB seq BB 2 BB 1 LN TH bb seq bb 2 bb 1 Thoracic AI 3 AI 2 AI 1

21 The new structures are physiologically more realistic. Extrathoracic ET 1 Environment LN ET ET seq ET 2 Oesophagus BB seq BB LN TH bb seq bb INT Thoracic ALV New ICRP Publication series on Occupational Intakes of Radionuclides (OIR) - available from late 2015 (?).

22 Internal dosimetry. D ( r T, t) A r r S, tsr r, t S T S Physics + Anatomy S r r, t Y E ( r T S 1 M ( r T, t) i i i T r S, E i, t) Nomenclature according to Bolch et al., JNM 50:477-84, 2009

23 Also phantoms for S-values calculations gets more realistic. brain skull backbone arm bones ribs lung heart liver large intestine urinary bladder Mathematical phantom MIRD 5 ICRP Publication 110, Ann. ICRP 39 (2), 2009 Adult reference computational phantoms kidneys small intestine large intestine pelvis replaced by voxel-phantoms Courtesy of Maria Zankl, HMGU

24 Voxel phantoms enables a more realistic estimation of absorbed dose. Code Monte Carlo EGSnrc Voxel phantoms ("Reference computational phantoms") of adult male and female Activity is assumed to be uniformly distributed within the source region 25 energy values (10 kev 10 MeV) 69 target organs and tissues 39 source organs and tissues Uncertainties lower than 5 % Nuclear data from new ICRP Publication 107 Courtesy of Maria Zankl, HMGU

25

26 Differences for photons are generally limited. 1 (LiverLiver) 100 (ThyroidThyroid) Male reference computational phantom Female reference computational phantom ORNL male ORNL female 10 SAF (kg -1 ) 0.1 SAF (kg -1 ) Male reference computational phantom Female reference computational phantom ORNL male ORNL female Photon energy (MeV) Photon energy (MeV) Excellent agreement between the values obtained with the reference computational phantoms and the ORNL values. The slight differences for small organs and high energies are due to secondary electrons escape. Zankl et al., Radiat. Prot. Dosim. 105: (2003)

27 Differences for photons are generally limited. 1e-1 (LiverStomach contents) 10 (Stomach wallstomach contents) 1e-2 1 SAF (kg -1 ) 1e-3 1e-4 SAF (kg -1 ) 0.1 1e-5 1e-6 Male reference computational phantom Female reference computational phantom ORNL male ORNL female 0.01 Male reference computational phantom Female reference computational phantom ORNL male ORNL female Photon energy (MeV) Photon energy (MeV) Cross-fire estimates are higher with voxelphantoms as organs are realistically closer than in the ORNL phantom. Very good agreement for the cross-fire irradiation from content to wall. Zankl et al., Radiat. Prot. Dosim. 105: (2003)

28 Differences for electrons are much more significant. 1e+0 Stomach wall Liver 100 Thyroid <- Thyroid 1e-1 1e-2 SAF (1/kg) 1e-3 1e-4 SAF (1/kg) 10 1e-5 Male reference computational phantom, photons 1e-6 Female reference computational phantom, photons Male reference computational phantom, electrons Female reference computational phantom, electr. 1e Male reference computational phantom Female reference computational phantom ICRP 30 approximation, male ICRP 30 approximation, female Particle energy (MeV) Electron energy (MeV) Close organs: cross-fire SAFs have sometimes the same magnitude as photons. High-energy electrons escape the source tissue: reduction of self-dose. Zankl et al., Phys. Med. Biol. 21: (2012)

29 Computational methods are employed also for calibration of in vivo detection systems. phantom calibration Detection system MC simulation spectrum subject subject activity (Bq) Courtesy of T.Vrba, CTU, Prague

30 Computational methods are employed also for calibration of in vivo detection systems. Courtesy of T.Vrba, CTU, Prague

31 Computational methods are employed also for calibration of in vivo detection systems. Courtesy of T.Vrba, CTU, Prague

32 Computational methods are employed also for calibration of in vivo detection systems. Courtesy of M.A.Lopez, CIEMAT, Madrid

33 Computational methods are employed also for calibration of in vivo detection systems. Courtesy of M.A.Lopez, CIEMAT, Madrid

34 Uncertainties play a significant role in internal dosimetry. Sources of uncertainties in the assessment of internal exposures Measurement counting statistics, in vivo: calibration of detectors, in vitro: chemical yield, sampling Biokinetic model dependant on the availability of relevant data (from human or another mammal, chemical analogue, basic physiology) Dosimetric model simplification of anatomy and particle physics, location of short range emitters and radiosensitive target cells and in tissues Application conditions of exposure: time, type of material, selection of model and technique of measurement

35 Uncertainties in the biokinetic model. Sensitivity Uncertainty

36 Uncertainties in the biokinetic model. Uncertainty Sensitivity

37 Uncertainties in the dosimetric model. 100 Source region: Kidneys 8 80 Percentage standard deviation Geometric standard deviation 6 60 SD (%) 40 4 GSD 20 0 Ureters Tonsils Tongue Sp-cord P-gland LN-Th LN-ET Eye-lens Bronchi Thymus Spleen SI-wall Prostate Pancreas O-mucosa Muscle Lymph Kidneys ET GB-wall Ht-wall Adrenals UB-wall Thyroid Skin St-wall Testes S-glands R-marrow Oesophagus Lungs Liver Colon Breast Brain 2 0 Target region

38 Uncertainties in the dosimetric model. 70 Source region: Liver 8 60 Percentage standard deviation Geometric standard deviation 50 6 SD (%) GSD Ureters Tonsils Tongue Sp-cord P-gland LN-Th LN-ET Eye-lens Bronchi Thymus Spleen SI-wall Prostate Pancreas O-mucosa Muscle Lymph Kidneys ET GB-wall Ht-wall Adrenals UB-wall Thyroid Skin St-wall Testes S-glands R-marrow Oesophagus Lungs Liver Colon Breast Brain 2 0 Target region

39 IDEAS Guidelines for the Estimation of Committed Doses from Incorporation Monitoring Data C.M. Castellani, J.W. Marsh, C. Hurtgen, E. Blanchardon, P. Berard, A. Giussani, M.A. Lopez

40 Why were the Guidelines developed? In the 3 rd European Intercomparison Exercise on internal dose assessment wide variability of the results of the evaluations was found. The results in terms of intake and committed effective dose were lognormally distributed with geometric standard deviations ranging from 1.15 for cases dealing with 3 H or 137 Cs, up to 2.4 for cases dealing with 239 Pu. These figures reflect the great difference of the individual results which vary, in the worst of cases, over a range of 5 orders of magnitude.

41 3 rd European Intercomparison Exercise on Dose Assessment from Incorporation Monitoring Data (1998/1999).

42 CED / GM rd European Intercomparison Exercise on Dose Assessment from Incorporation Monitoring Data (1998/1999). H. Doerfel - EURADOS/IAEA Regional Training Course on Advanced Methods for Internal Dose Assessment Prag Februar msv Case 7: Pu-239/ You are above all limits! 29 answers msv msv Don t worry! 0,1 ID

43 Reasons for discrepancies: "stupid" errors: units, orders of magnitude, copying mistakes. Application of contradictory assumptions: Absorption type, time and modality of intake discrepancy between biokinetic and dosimetric model used, confusion between isotopic ratios by mass or by activity (e.g., Pu-mixtures) The most important outcome of the intercomparison was the need to develop agreed guidelines for internal dose evaluation.

44 The EU-Project IDEAS (5 th Framework Programme, ). Forschungszentrum Karlsruhe, Germany SCKCEN, Belgium Electricité de France, France ENEA, Italy IRSN, France KFKI/AEKI, Hungary RPI, Ukraine NRPB (HPA), UK Aim of the project: Development of guidelines for the standardization of dose assessment for occupational internal exposures

45 The EU-Project IDEAS (5 th Framework Programme, ). Work package 1 Collection of incorporation cases Work package 4 Development of general guidelines Work package 3 Evaluation of incorporation cases Work package 2 Preparation of evaluation software Work package 5 Practical testing of general guidelines

46 The Guidelines are developed upon three basic principles (the pillars). Harmonization: by following the guidelines any evaluators should obtain the same internal dose estimate from a given data set of radiometric measurements of biological samples (bioassay). Accuracy: the "best" estimate of dose should be obtained from the available data. Proportionality: the effort applied to the dose evaluation should correspond to the evaluated level of exposure: the lower the dose, the easier the evaluation process will be.

47 The effort is proportional to the expected exposure. Level 0: Annual dose (committed effective dose from intake of radionuclide that occur in the accounting year) less than 0.1 msv. No dose assessment is needed. Measurement values of the bioassay are recorded and the assessed dose can be set equal to zero. Level 1 : Simple, reference evaluation. The assessment is made in a simple way by using the ICRP default parameter values, unless there is better a priori information, e.g. with regard to intakes by inhalation on the particle size distribution. (Annual doses typically between 0.1 and 1 msv)

48 The effort is proportional to the expected exposure. Level 2: Sophisticated evaluation using additional information to give more realistic assessment of dose: typically a special assessment of an accidental intake. Comparisons are made of the model predictions ( the fit ) with the data, to choose between alternative parameter values, or to find optimum parameter values (a posteriori). At this Level, the parameters adjusted typically relate to the material (for inhalation intakes the AMAD and absorption Type), and the time of intake if unknown (dose from the intake typically 1 6 msv).

49 The effort is proportional to the expected exposure. Level 3: More sophisticated evaluation, which applies to cases where there are comprehensive data available, as would be the situation after an accident. The evaluation is an extension of Level 2, typically to parameters relating to the subject (e.g. for inhalation intakes the HRTM particle transport rates). The fundamental approach at this Level is to adjust the model parameter values systematically, in a specific order ( step-bystep approach), until the goodness of fit is acceptable (i.e. the fits obtained to all the data are not rejected by the specified criteria) (dose typically > 6 msv).

50 Critical monitoring quantity. M c e T m 2 T If M<Mc then stop evaluation at Level 0.

51 Content of the document. Detailed indication for data handling How to deal with single data and with multiple datasets Handling of chronic intakes Number and type of data required for dose assessement Processing of measurement data Assessment of uncertainty on data Handling data below detection limit Influence of decorporation therapy ("modified" kinetics) Identification of outliers General information on the philosophy of the guidelines Sctructured approach (flow-charts) according to the level principle

52 Content of the document. Detailed indication for data handling How to deal with single data and with multiple datasets Handling of chronic intakes Number and type of data required for dose assessement Processing of measurement data Assessment of uncertainty on data Handling data below detection limit Influence of decorporation therapy ("modified" kinetics) Identification of outliers General information on the philosophy of the guidelines Sctructured approach (flow-charts) according to the level principle

53 Content of the document. Detailed indication for data handling How to deal with single data and with multiple datasets Handling of chronic intakes Number and type of data required for dose assessement Processing of measurement data Assessment of uncertainty on data Handling data below detection limit Influence of decorporation therapy ("modified" kinetics) Uncertainties are required for: Identification of outliers An objective evaluation of the measured data Identification of outliers General information Application the of philosophy weighted fitted of the procedures guidelines Evaluation of the goodness of the fit Application of statistical tests, e.g. 2 Sctructured approach (flow-charts) according to the level principle

54 Uncertainties are expressed as "scattering factors" (geometrical standard deviation).

55 The procedure is described by means of flow charts. Stage 1 (all levels): Is the evaluation Step 2.0: necessary? Analysis of the incorporation case: Graphical representation of the data, simple calculation by hand Stage 2 (M>M c, i.e E > 0.1 msv): Test the Step reliability 2.3: New of the intake measurement is confirmed if M/SF 2 > P. The probability of a false positive (i.e. to assume erroneously a new intake) is less than 2.5%. Calculate the net measurement result (N = M Step 2.4: New intake is not confirmed. If M/SF P) and go to Stage 3. 2 < P < M*SF 2, Step 2.1: then Assessment the measurement of the uncertainty is compatible on the with measured the previous value intake. M. Realistic No dose estimates assessment of the is performed, uncertainty the are measured required. value In the is saved IDEAS Guidelines together with uncertainties relevant information are given in (radionuclide, terms of scattering activity, type factor of (SF). monitoring) in the individual record. Step 2.2: Calculation of the contribution from previous intakes.

56 The procedure is described by means of flow charts. Stage 1 (all levels): Is the evaluation necessary? Stage 2 (> 0.1 msv): Test the reliability of the measurement

57 The procedure is described by means of flow charts. No Stage Routine monitoring? Stage 1 (all levels): Is the evaluation necessary? Yes Stage 2 (> 0.1 msv): Test the reliability of the measurement Stage 3 (>0.1 msv): Standard "reference" dose evaluation 3.2 Identify pathway of intake 3.3 Assign a priori parameters (default or site-specific) Step 3.3: use a priori Information on AMAD, chemical form (absorption type), time of incorporation, if available. 3.4 Estimate intake and dose Step 3.4: the intake I is obtained dividing the net measurement result N = M P by the relevant retention or excretion Yes function. The dose is Dose < 1 msv Record intake and dose evaluated applying the standard dose coefficients. End No Stage 4

58 The best estimate of intake can be found using the maximum likelihood method. The likelihood of each individual measurement is given by L ( i I ) Where SF exp 2 2 ln( SF ) ln( SF 2 i exp A B ) 2 ) ln( I m( t i ) ln( SFi ) i 2 M i 1 ln( SF i ) ln( M 2 and I is the true acute intake at t=0.

59 The best estimate of intake can be found using the maximum likelihood method. When there are n independent measurements the combined likelihood is the product L( I ) i1 With the MLM the best fit of value of intake I is that which maximizes the likelihood function n L ( I ) i

60 The best estimate of intake can be found using the maximum likelihood method. The likelihood functions can be written as: With L( I ) 2 ( Const exp o 2 I ) 2 o ( I ) n i1 ln( M i ) ln ( ln( I SF i ) m( t 2 i )) 2

61 The best estimate of intake can be found using the maximum likelihood method. The maximum of the likelihood function occurs where 0 2 (I) is a minimum. In order to minimise 0 2 this expression is differentiated with respect to ln(i) and set equal to zero. Rearranging for I gives With I ln( I i ) M m( t n i1 i i ) ln( M n i1 i / ln( SFi ) 1 ln( SF m( t i ) i 2 this becomes 2 )) ln( I ) n i1 n i1 ln( ln( I i ln( SFi 1 SF i ) ) ) 2 2

62 The best estimate of intake can be found using the maximum likelihood method. As an example, consider urine data where the scattering factor is dominated by Type B errors (with SF i = constant) ln 1 n I ln n i1 n I i ln I i1 i 1 n that is n I n I i i1

63 The best estimate of intake can be found using the maximum likelihood method. The previous equation can also be applied to cases where data sets from different monitoring techniques are available. If urine and faecal data are available and the scattering factors for the urine and faecal data are set to SF u and SF f, respectively the equation becomes ln I n u i1 n ln where I i refers to the individual intake evaluations from urine data and I j from fecal data i ln ( SF 1 I u f j1 u f 2 i1 ln ( SF ) j1 ln ( SF ) u ) 2 n n ln I ln ( SF 1 j f f ) 2 2

64 The best estimate of intake can be found using the maximum likelihood method. In this case the 0 2 values is calculated with 2 o ( I) n i1 ln( M ) ln( I m ln ( SF ) )) u n f ui u u ( t i 2 i1 ln( M fi ) ln( I m ln ( SF f ) f ( t i )) 2 With (n u +n f 1) degrees of freedom (evaluated only one value of intake) Where M u refers to the measurements of urine and M f refers to the the measurements of feces. m u refers to the excretion function for urine and m f refers to the excretion function for feces.

65 The goodness of the fit can be judged with the chi-squared test. If the predictions are inconsistent with the data, then the calculated value of 0 2 is inconsistent with the theoretical chisquared ( 2 ) distribution with (n-1) degrees of freedom. The expected value of 2 is equal to the number of degrees of freedom (i.e. n-1). It is indicated that the fits to the data are judged to be inadequate if: the probability that 2 is greater than 0 2 is 5% or less (i.e. if p- value < 0.05). In other words the fit is inadequate at the 5% level of significance (function CHIDIST( 0 2,n-1) in Excel), or if the fit displayed graphically looks unreasonable by eye, i.e if all, or a long series, of data were systematically underestimated or overestimated

66 Application of the guidelines. Work package 1 Collection of incorporation cases Work package 4 Development of general guidelines Work package 2 Preparation of evaluation software Work package 3 Evaluation of incorporation cases Joint IDEAS/IAEA Intercomparison Exercise on Internal Dose Assessment (2004) Work package 5 Practical testing of general guidelines

67 Joint IDEAS/IAEA Intercomparison Exercise on Internal Dose Assessment (2004). Results: GM (msv) GSD Case 1: H-3 Positive influence 26 of the IDEAS guidelines 1.06 on the harmonisation of the assessed intake and dose values Case 2: Cs-137 Geometric mean of GSD: Less outliers among the participants who used the guidelines Case 3: Co More accurate results among the participants who 3rd European used CORRECTLY Intercomparison the guidelines Exercise: Case 4: I Geometric But: mean of GSD: 1.71 Case 5: U Continuous 27 training and education are necessary, as well as QA Case 6: Pu Intercomparison exercises should be performed on a regular basis Case 6: Am Final Workshop in Wien (IAEA-TECDOC-1568)

68 Revision of the guidelines. CONRAD (Coordinated Network in Radiation Dosimetry). Revision of single parts of the guidelines ( ) EURADOS/IAEA Training Course: exercises using EURADOS/IAEA the Czech guidelines Technical and Regional evaluation Training Course of on the Advanced results Methods (Feb. University in Prague (Czech Republic) Prague 2nd to 6th February ). for Internal Dose Assessment Application of IDEAS Guidelines and dissemination of CONRAD internal dosimetry results

69 Revision of the guidelines. 4 exercises considered as "intercomparison" More than half of the participants were able to evaluate the correct intake and/or the correct dose thanks to a precise application of the guidelines Typical errors in the application of the guidelines: choice of the SF-values Subtraction of the contribution of previous intakes No check of the goodness of the fit

70 Example of the results Case ELP1 32 participants. Wrong dose coefficient Order of magnitude (Sv/mSv) Smaller than the result of the monitoring!!! Wrong assumptions on the incorporation time (start of monitoring interval)

71 Example of the results Case ELP1 32 participants.

72 Revision of the guidelines. CONRAD (Coordinated Network in Radiation Dosimetry). Revision of single parts of the guidelines ( ) EURADOS/IAEA Training Course: Exercises woth the guidelines and evaluation of the results (Feb. 2009). EURADOS WG7 Internal Dosimetry - Task 7.1 Drafting of the revised IDEAS Guidelines ( ) - Coord. C.M.Castellani (ENEA, Italy)

73 The new guidelines. WHAT HAS REMAINED/ 1 General structure with flow charts Criteria for acceptance or rejection of fits ( 2 and evaluation by eye ). Methods of data handling before dose evaluation (e.g., correction of excretion measurements) Determination of uncertainties (given as SF-values) Handling of measurements below detection limit

74 The new guidelines. WAS HAS REMAINED/ 2 Handling of measurements after decorporation therapy Identification of outliers WAS HAS BEEN ELIMINATED Detailed description of the respiratory tract (HRTM) Detailed description of the old GI-Tract model Information about absorption classes

75 What is new in the new guidelines. Evaluation methods for direct dose assessment : 3 H Isotopic composition of mixtures of uranium and plutonium mostly encountered in the workplace. Methodology for describing 241 Am ingrowth following decay of 241 Pu. New procedure for analysis of wound cases. Four detailed cases as an example of a correct application of the guidelines (taken from the EURADOS/IAEA advanced training course). Extensive revision of the statistical concepts and of the methodology for model fits: Maximum-Likelihood-Method Autocorrelation test (also for multiple datasets) Revised glossary

76 Direct dose assessment: 3 H case. Calculation of the integral under the curve: Us

77 The NCRP model for the interpretation of wound cases. Retention at the wound site

78 The NCRP model for the interpretation of wound cases. Flow charts and procedure for evaluation of wound cases Selection of the wound route of intake Flow chart related to Special procedure above Level 1 : Evaluation by means of different NCRP default categories

79 Solved cases show how the guidelines have to be applied. Four cases from EURADOS- IAEA 2009 training course Step- by-step procedure for «reference solution»

80 How to subtract the contribution of natural radioactivity. Methods for the subtraction of alimentary background in case of occupational exposure to radionuclides belonging to the three natural decay series, are indicated. Values on daily urinary and fecal excretion for 234 U and 238 U, 228 Th, 230 Th and 232 Th, 226 Ra, 210 Po due to dietary intake are provided.

81 Typical and achievable detection limits are reported. Definitions of DT and DL according to standard ISO 28218:2010.

82 Typical isotopic compositions are given as reference.

83 CONCLUSIONS/1 The Revision of the Guidelines IDEAS performed during their application, in particular following the 2009 training course, allowed to improve its overall structure, while maintaining the principles aimed at the harmonization of methods of assessment of internal dose. The Guidelines were then updated in relation to evolution of non-systemic phase models (mainly the application of the NCRP model for wound and the presentation of the ICRP Alimentary Tract Model).

84 CONCLUSIONS/2 The Guidelines have also been expanded and integrated with methodologies and information that were not present in the previous version. (e.g. direct dose assessment method, subtraction of background due to dietary intake of naturally occurring radionuclides, examples of dose assessment with detailed explanations). The IDEAS Guidelines (Version 2) represent an updated tool for the evaluation of internal dose and a useful reference for harmonization of dose assessment procedures.

85

86 Acknowledgments: ICRP Task Groups INDOS & DOCAL. Schliersee, Germany, 2013

87 Acknowledgments: EURADOS WG 7 Internal Dosimetry. Warsaw, Bologna, Poland, Italy 2014, 2013

88 X Congreso Regional Latinoamericano IRPA de Protección y Seguridad Radiológica Buenos Aires, de abril de 2015 Curso de refresco CR-1: Dosimetría Interna AUGUSTO GIUSSANI, BfS, Germany agiussani@bfs.de