What You Need to Know About Biodosimetry:
The Basics

• What is the difference between radiation biodosimetry and radiation bioassay?
• Why is biodosimetry needed?
• What is physical dosimetry?
• What is dose reconstruction?
• What clinical clues help provide estimates of radiation dose?
• How do you use the REMM Dose Estimator for Exposure?
• What should you do when there are conflicting dose estimates?
• Use of biodosimetry in long term surveillance studies after radiation exposure
• See REMM Biodosimetry Reference List

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What is the difference between radiation biodosimetry and radiation bioassay?

• Radiation biodosimetry: definition
• Radiation bioassays measure
  • Whether internal contamination has occurred
  • What isotopes are detected
  • Various kinds of bioassays are available
    • Some assays are for initial screening (yes, no contamination and initial triage based on cut point)
    • Some are for more definitive isotope identification and detailed quantification
    • Most detailed bioassays can determine a “past, current and future” radiation dose from contamination
    • More information about using bioassays
      • Miller CW, Ansari A, Martin C, Chang A, Buzzell J, Whitcomb RC Jr. Use of epidemiological data and direct bioassay for prioritization of affected populations in a large-scale radiation emergency. Health Phys. 2011 Aug;101(2):209-15. [PubMed Citation]
      • Management of Persons Internally Contaminated with Radionuclides in a Nuclear or Radiological Emergency, A Manual for Medical Personnel, 2018, (IAEA and partners)
      • Management of Persons Contaminated with Radionuclides: Scientific and Technical Bases (NCRP Report No. 161, Vol. II), Bethesda, MD, 2010.
      • Management of Persons Contaminated with Radionuclides: Handbook (NCRP Report No. 161, Vol. I), Bethesda, MD, 2008.
• Bioassays measure radioactivity directly in biological specimens
  • Examples: blood, urine, feces, sweat
• Bioassay results can be used to
  • Estimate radiation dose (to the whole body or specific organs) expected to be accumulated in the future over a specified period of time
  • Measure the ongoing effectiveness of treatments for internal contamination
• Examples of units of measure for radiation exposure from internal contamination
  • After internal contamination: various units are used including, e.g. Committed Effective Dose Equivalent (CEDE)
  • After both external exposure and internal contamination: various units are used including Total Effective Dose Equivalent ( TEDE)
• When to Use Bioassay vs. Biodosimetry

  Type of Incident	Exposure (Biodosimetry)	Contamination (Bioassay)
  Improvised Nuclear Device (IND)	Effective (shine)	Effective (fallout)
  Nuclear Power Plant (NPP)	Limited	Effective (fallout)
  Radiation Dispersal Device (RDD)	Limited	Effective
  Radiation Exposure Device (RED)	Effective	Not useful

  Biodosimetry determines a "past" radiation dose from an "exposure" incident.
  Bioassay determines "past, current and future" radiation dose from a "contamination" incident.

  Source of table above: Healthcare Response Challenges after Various Kinds of Radiation Mass Casualty Incidents (HHS/TRACIE webinar, 1 hour 16 minutes, July 11, 2018) (Several experts speakers; this table is shown at 27:50 of video, in section from Robert Jones, Ph.D. Viewing video requires registration.)

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Why is biodosimetry needed?

• Since most victims of large mass casualty radiation emergencies would not be wearing personal dosimeters, other methods must be used to estimate the dose they received
• Biodosimetry helps to
  • Predict the time course and severity of the phases of the Acute Radiation Syndrome
  • Facilitate short term triage, including where the patient should be treated
  • Suggest countermeasure that will be needed to treat ARS, especially acutely
  • Assess the risk of long term consequences from radiation exposure.

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What is physical dosimetry?

• Actual measurements of radiation exposure made by detection equipment including
  • Personal dosimeters
    • Worn on outside of clothing by workers in an actual or potential radiation environment to track exposure
    • Measure the radiation dose received by the device
    • Knowing the location of the device on the wearer's person helps interpret the significance of the dosimetry reading for the wearer
    • Many different kinds of devices are available
  • Survey meters
    • Measure radiation levels in the environment
    • Can be used to estimate dose that may have been received by workers or victims in the area assessed by the meter
    • Different kinds of devices are used for specific tasks.

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What is dose reconstruction?

• Matching a victim's geographic location(s) during an incident to radiation exposure maps for the incident created from
  • Actual measurements in the field and/or
  • Computer modeling data
• Computerized 2D or 3D models of radiation levels in the environment
  • Can be generated from data acquired in an actual incident or from theoretical models of events, including in specific venues
  • Can be overlain on maps of affected areas to track changes in radiation levels over time.
  • Detailed mapping of radiation levels can help provide
    • Data for protective action recommendations
    • Dose estimates for individuals or groups of victims in specific locations
• See details about Dose Reconstruction
• See illustration of radiation protection factors that would affect dose reconstruction: Time Distance, Shielding
• See Time Sequenced Size of Dangerous Fallout Zone and 0.01 R/Hour Boundary after a Hypothetical 10kT Nuclear Detonation at Ground Level

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What clinical clues help provide estimates of radiation dose?

• Evaluate subsyndrome severity scores for the 4 ARS subsyndromes
  • A higher severity score for any of the subsyndromes is generally correlated with higher absorbed dose
  • Subsyndromes
    • 
    • 
    • 
    • (a.k.a. Cerebrovascular)
• A targeted physical exam is also useful.

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How do you use the REMM Dose Estimator for Exposure?

• The REMM Dose Estimator for Exposure provides information that can help responders assess, triage, and manage victims.
• Providers should
  • Collect and consider all the physical, clinical and laboratory information and observe how data change over time.
  • Correlate information from victim's history and physical, including signs and symptoms, with specific radiation effects expected at various doses.
  • Use physical dosimetry information if and when it is available.
    • Was the victim wearing a personal radiation dosimeter? This would be unlikely in a terrorist event but likely for an occupational radiation worker.
    • Do incident managers have information about radiation dose in the geographic area where the victim was at the time of the incident?
  • Register the victim in the incident data base using the best biodosimetry and clinical information available.

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What should you do when there are conflicting dose estimates?

• Initially, use the highest whole body dose estimate to plan treatment.
• Modify the treatment plan as additional clinical and laboratory data are obtained over time.

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Use of biodosimetry in long term surveillance studies after radiation exposure

• Simon SL, Bouville A, Kleinerman R. Current use and future needs of biodosimetry in studies of long-term health risk following radiation exposure. Health Phys 2010 Feb; 98(2): 109-17. [PubMed Citation]

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References

See Biodosimetry Reference List