Triage, Monitoring And Dose Assessment For People Exposed To Ionising Radiation Following A Malevolent Act

Transcription

1 Triage, Monitoring And Dose Assessment For People Exposed To Ionising Radiation Following A Malevolent Act Radiological and Nuclear Emergency Management: Aspects of Radiobiology ENEA Casaccia Research Centre, Rome 6 November 2012 George Etherington, Kai Rothkamm, Arron Shutt and Mike Youngman Centre for Radiation, Chemical and Environmental Hazards

2 Outline Objectives of triage and monitoring Scenarios Current challenges Assistance networks International projects

3 Objectives of individual monitoring in emergencies 1. To quantify absorbed doses to organs for people who may be at risk of deterministic effects on their health (e.g. acute radiation syndrome) providing an input to decisions on medical treatment 2. To quantify effective doses for people exposed at lower levels but still potentially at risk of stochastic effects on their health (cancer induction) providing an input to decisions on decorporation (e.g. use of Prussian Blue for radiocaesium intakes) 3. To identify the potentially large numbers of people for whom exposures are unlikely to have an effect on health e.g. the worried well

4 Malevolent use scenarios An external irradiation incident (e.g. hidden source ) An environmental contamination incident (e.g. a radiological dispersal device, RDD) A food/water contamination incident

5 Malevolent use scenarios Factors to be taken into account Any incident would occur at a location not known in advance (therefore, no site-specific plans) The location could be a highly populated urban area Large numbers of people could be affected The time between exposure and detection of the incident may be unknown (covert scenarios) Radiation exposures could range from very low to substantial, and could be combined with conventional injuries

6 Some major challenges C1. Rapid selection and prioritisation of people for monitoring C2. Rapid initiation of individual contamination monitoring at the scene C3. Monitoring large numbers of people C4. Monitoring: different people, different detection systems C5. Monitoring for contamination by α- and pure β-emitters C6. Rapid determination of external irradiation doses C7. Rapid interpretation/assessment of individual contamination monitoring data C8. Evaluation of internal dose thresholds for deterministic effects

7 Rapid selection and prioritisation for monitoring C1 The concept of Triage The use of simple procedures for rapidly sorting people into groups based on: - their degree of physical injury - actual or potential effects on health Trauma triage and the allocation of care to these people so as to expedite treatment and maximise the effective use of resources. Radiological triage

8 Types of care The term care is used in a broad sense, for: urgent treatment of trauma injuries treatment of life-threatening radiation exposures decontamination procedures through to radiological monitoring designed to provide information and reassurance provision of advice on possible health consequences

9 Radiological triage stages (Trauma triage) Clinical observations Information on location, proximity Premonitoring Biodosimetry Initial contamination screening measurements Measurements with transportable body monitors Monitoring Measurements with laboratory body monitors Results of urine monitoring Time period after incident (d)

10 Triage at Goiânia Group Total population Number ~ 1,000,000 % of population 100 People monitored 112, People with significant external and internal doses People admitted to hospital People needing intensive medical care Deaths Severe trauma (amputation)

11 Rapid initiation of contamination monitoring C2 Pre-monitoring triage External contamination monitoring Decontamination Rapid screening for internal contamination Measurement of internal contamination

12 Rapid initiation of contamination monitoring Monitoring large numbers of people C2, C3 Screening (triage) Measurement of internal contamination

13 Monitoring large numbers of people HPA s transportable body monitoring system

14 Monitoring: different people, different detectors C4 Monte Carlo particle transport calculations for body monitoring Problems: - In a radiological incident, members of the general public are not well-represented by standard calibration phantoms. - A wide range of detectors may need to be used. Aim: To allow body monitoring calibrations for any possible detector system, radionuclide, age, subject size and orientation.

15 Modelling of mathematical detector/phantom system Schematic Comparison between mathematical and physical calibration Model MCNPX

16 Monitoring for contamination by α- and pure β-emitters C5 Issues - People need to be given instructions on providing samples that can be followed reliably - Ideally, 24 hour urine samples are needed - Reliable arrangements for sample collection & delivery to laboratory are needed - A reliable sample tracking system is needed - Sample preparation and radiochemistry are likely to be time-consuming - Sample throughput can be quite low

17 Rapid determination of external irradiation doses C6 Biologically-based biodosimetry Physically-based biodosimetry Dose estimation based on clinical observations Swartz HM et al (2010). Health Physics 98, no 2,

18 Biologically-based biodosimetry Measurements of biological materials/processes affected by radiation exposure Examples: chromosome damage [dicentrics, micronuclei, translocations, PCC] IAEA (2011) gene expression signatures Paul et al (2008) protein biomarkers C-reactive protein (CRP) [acute phase inflammatory response, useful up to 3 d after exposure; dose > 1 Gy; reproducibility?] Blakely et al (2010) γ-h2ax [DNA damage signalling & repair; useful up to 2d after exposure, radiation-specific; sensitive to doses > 200 mgy; results within 24 h] Rothkamm & Horn (2009) - Chromosome aberration analysis is the gold standard, but time-consuming and low throughput; some gains possible through automation - Few methods are completely specific to radiation damage - Complex time-dependent responses, often short-lived - Gene expression & protein biomarkers great potential but not validated - Most assays are not field-deployable specialised laboratories needed

19 Physically-based biodosimetry Measurements of physical effects in tissues after radiation exposure Examples: Free radicals in finger nails measured by Electron Paramagnetic Resonance (EPR) Radiation-induced defects in tooth enamel measured by EPR or Optically-Stimulated Luminescence (OSL) Health Physics 98, no 2 (2010) - Effects are generally specific to radiation damage - Some techniques show time-independent response (e.g. EPR on tooth enamel) - Potentially field-deployable - OSL can also be used with personal electronic devices (chips, CCs, etc.)

20 Dose estimation based on clinical observations Clinical observations and haematology measurements after radiation exposure Goans & Waselenko (2005) Examples: Time to onset of nausea & vomiting Serial lymphocyte counts Neutrophil:lymphocyte ratio measurement Concentration of blood lymphocytes, μl -1 (Dainiak, 2007). - Effects not necessarily caused by radiation exposure - Haematology measurements require skilled personnel and repeated blood sampling

21 Rapid interpretation of individual contamination monitoring data C7 Dual Action Level approach 200 msv Upper level 20 msv Lower level 1 msv

22 Upper Action Levels on dose Internal contamination E 50 = 200 msv Level proposed by TIARA project above which medical treatment to reduce doses (e.g. by decorporation) should be considered (Menetrier et al., 2005) External contamination D = 2 Gy to skin 20% of the level recommended by IAEA (Generic Procedures for Medical Response (IAEA-EPR-MEDICAL 2005)) for immediate decontamination, immediate medical examination, and medical treatment.

23 Upper Action Levels on dose Example: 60 Co inhalation (adults)

24 Actions associated with Action Levels M > AL U (upper action level) urgent external decontamination (if appropriate) refer for immediate medical assessment take blood samples for serial lymphocyte counts and for biodosimetry measurements AL U > M > AL L (upper action level) external decontamination in priority order (if appropriate) more accurate internal contamination measurements in priority order long-term follow-up monitoring M - measurement AL U upper action level AL L lower action level

25 TIARA method: 137 Cs whole body measurement 137 Cs whole body measurement TIARA Treatment Initiatives after Radiological Accidents (Menetrier F et al., 2007)

26 Rapid assessment of internal doses C7 Dose per unit measurement lookup tables

27 Limitations on use of look- up dose assessment tables Calculations use a combination of default parameter values, BUT Particle size distribution could be highly variable Absorption Type is dependent on chemical form, on which information would be sparse Intake pathway may be uncertain Measurements (particularly rapid screening measurements) could have large uncertainties Therefore, while dose assessments based on default values for input data may be adequate for initial dose assessments they may not be adequate as a final assessment if doses are significant

28 Evaluation of internal dose thresholds for deterministic effects C8 IAEA (2005). Generic Procedures for Medical Response during a radiological or nuclear emergency, EPR-Medical 2005

29 Effect of dose protraction Example: Risk of mortality vs bone marrow dose Risk Gy/h 0.02 Gy/h Absorbed dose (Gy) Risk = 1 exp(-h) H = ln 2 (D/D 50 ) V H hazard function D absorbed dose V shape factor NRPB (1996). Risks from Deterministic Effects of Ionising Radiation.

30 Plans for triage and monitoring for people returning to the UK after Fukushima

31 International Networks IAEA Response Assistance Network (RANET) coordinates international assistance in the event of a radiation emergency (specialist laboratories, monitoring, data analysis, modelling). WHO BioDoseNet a worldwide biological dosimetry network to complement smaller local networks in the event of large numbers of casualties

32 Network-related projects RENEB Realising a European Network of Excellence in Biological Dosimetry. EC-funded project to realise the European Network of Biodosimetry, Global Health Security Initiative (GHSI) an international forum to share and collaborate on initiatives to enhance global public health preparedness Radiological / Nuclear Threats Working Group Survey/database of radionuclide bioassay laboratory capabilities. Aims are to establish an international radionuclide bioassay laboratory network; develop standard procedures; hold emergency exercises

33 Other networks / projects EURADOS WG7 aims to harmonize and co-ordinate research in internal dosimetry and to disseminate scientific knowledge. EURADOS WG10 aims to establish a multi-parameter approach to dose assessment in retrospective dosimetry, spanning both biological and physical dosimetry and including emergency response. MULTIBIODOSE Multi-disciplinary biodosimetric tools to manage high scale radiological casualties EC FP7 Security Research Programme project (currently in 3 rd year)

34 References TMT Handbook (2009). Triage, Monitoring and Treatment of People exposed to Ionising Radiation following a Malevolent Act. Carlos Rojas-Palma, Astrid Liland, Ane Naess Jerstad, George Etherington, Maria del Rosario Pérez, Tua Rahola and Karen Smith (editors). HPA (2010). Use of Prussian Blue (Ferric Hexacyanoferrate) for Decorporation of Radiocaesium). Advice from the Health Protection Agency. Radiation, Chemical and Environmental Hazards RCE-17, December Etherington G, Rothkamm K, Shutt A L and Youngman M J (2011). Triage, monitoring and dose assessment for people exposed to ionising radiation following a malevolent act. Radiat Prot Dosim 144,

35 Biodosimetry references Swartz HM et al (2010). A critical assessment of biodosimetry methods for large-scale incidents. Health Physics 98, no 2, Blakely WF et al (2010). Multiple parameter radiation injury assessment using a non-human primate radiation model biodosimetry applications. Health Physics 98, no 2, Rothkamm K and Horn S (2009). Ann Ist Super Sanità no 3, Goans RE & Waselenko JK (2005). Medical management of radiological casuatlies. Health Physics 89, no 5, Paul S & Amundson SA (2008). Development of gene expression signatures for practical radiation biodosimetry. Int J Radiat Oncol Biol Phys 71, no 4, IAEA (2011). Cytogenetic Dosimetry: Applications in Preparedness for and Response to Radiation Emergencies. EPR-Biodosimetry 2011.

36 Triage, Monitoring And Dose Assessment For People Exposed To Ionising Radiation Following A Malevolent Act Radiological and Nuclear Emergency Management: Aspects of Radiobiology ENEA Casaccia Research Centre, Rome 6 November 2012 george.etherington@hpa.org.uk Centre for Radiation, Chemical and Environmental Hazards