Sensitivity of Human Lymphocytes to Low-Dose Radiation

1. Sensitivity of Human Lymphocytes to Low-Dose Radiation Gordon K. Livingston, PhD Technical Director, Cytogenetic Biodosimetry Laboratory Radiation Emergency Assistance Center Training Site Oak Ridge Insitute for Science and Education Oak Ridge, TN 37831 Gordon.Livingston@orise.orau.gov http://orise.orau.gov/reacts

2. Cytogenetic Biodosimetry Cytogenetic analysis provides a method to estimate radiation dose to individuals exposed to ionizing radiation when physical dosimetry devices are not available.

3. Lymphocytes • Lymphocytes serve as ideal biological dosimeters because they: • are very sensitive to radiation, • are readily available in routine blood samples, • circulate throughout the body, • can be easily cultured and induced to divide in vitro • respond consistently to ionizing radiation exposure by expressing chromosomal DNA damage in a dose-dependent manner.

4. Image of Normal Metaphase Spread

5. Dicentric Chromosome

6. Dicentric Chromosome Assay • Low background rate (1-2 per 1,000 cells) • Independent of age and gender • Sensitivity range (0.2 – 5 Gy) • Specificity to radiation is high • Consistent radiation dose-response • Proven in accidents over four decades • Considered the gold standard

7. Multiple Dicentric Chromosomes

8. Y=aD Linear Y=aD+bD2 Dicentrics/cell Quadratic (linear-quadratic) Dose [Gy] Typical Dose Response Curves

9. The Lymphocyte Micronucleus Test as a Radiation Biodosimeter

10. LyLLy

11. Lymphocyte in Normal Anaphase

12. Lymphocyte in Abnormal Anaphase

13. Micronucleus

14. X-Ray Therapy Machine

15. X-ray Exposure Conditions Westinghouse Orthovoltage Therapy Unit 78 kV, 5 mA, 2mm Al added filtration output measured at 19.8 cGy/min at 50 cm 30 cm field size with +/- 10 % uniformity graded doses of 0, 5, 10, 15, 20 & 25 cGy 10 ml media (3-4 x 105 cells/ml) in 25 cm2 culture flasks at 37 C for 72 hr

16. Micronucleus Dose Response

18. The Micronucleus Test as a Biological Dosimeter Linear Dose Response to X-rays y = 2.783 x + 3.714 35.5 = 2.783 x + 3.714 X = 11.4 c Gy NCRP Dose to red marrow is 0.2 m rad / micro Ci 48,000 micro Ci x 0.2 m rad = 9,600 m rad = 9.6 rad (9.6 c Gy)

20. Red 1, 2 & 4 Green 3, 5 & 6

24. Cytogenetic Biodosimetry • Limitations • Large event could overwhelm resources • Labor intensive • Samples require shipment • Advantages • Proven method for dose estimation • Amenable to web-based image scoring • Existing resource of clinical laboratories

25. Cytogenetic Dosimetry Capacity Worldwide • Cytogenetic labs and regional networks already collaborating with WHO: • North-American • Latin American (with IAEA support) • European • Scandinavian • Eastern Europe: RF and Ukraine • Western-Pacific: Japan, S. Korea, Australia • Need to integrate and coordinate these networks globally • Need a clear concept of operations for emergencies and in "quiet" time to make the most of these labs joint capabilities

26. Consortium Lab in Consortium (Metafer System) REAC/TS CBL Secure Central Server (Access Limited) Lab in Consortium (Metafer Software) Satellite Scoring Station (Metafer Software)

27. The re-establishment of the REAC/TS-Cytogenetic Biodosimetry Laboratory, operated by the Oak Ridge Institute for Science and Education (ORISE), was supported by: • DOE-NNSA, • DOE-EH, and • Nuclear Regulatory Commission. Establishing a Web-Based International Radiation Cytogenetic Biodosimetry Consortium at REAC/TS is being funded by DOE-NNSA.

28. Questions