Biological Dosimetry in Radiation Accidents - PowerPoint PPT Presentation

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Biological Dosimetry in Radiation Accidents
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Biological Dosimetry in Radiation Accidents

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  1. Biological Dosimetry in Radiation Accidents Andrzej Wojcik Department of Radiobiology and Health Protection Institute for Nuclear Chemistry and Technology Warszawa Department of Radiobiology and Immunology Insitute of Biology Swietokrzyska Academy Kielce

  2. Why is it important to perform biological dosimetry in case of a radiation accident? Phases of the Acute Radiation Syndrome P. Gourmelon et al. 2004

  3. The methods The principle of biological dosimetry Biological dosimetry is a method of dose assessment on the basis of radiation-induced damage in the body • Chromosomal Aberrations and Micronuclei in peripheralblood lymphocytes. Application: whole- and partial-body exposure • Electron paramagnetic resonance (EPR)Application: teeth, bones – partial body exposure Bothmethodsrely on comparing the results of a measurement with a calibration curve that is generated under in vitro conditions

  4. The material of choice for biological dosimetry is the human peripheral blood lymphocyte • Lymphocytes circulate around the body, so some of them arealwaysexposed even in cases of partial-body exposure • Lymphocytes can be collected easily • Lymphocytes are to over 95% in the resting phase G0

  5. The principle of blood lymphocyte culture Phytohaemaglutinine Colcemid culture time = 48h harvest slide praparation staining Cytochalasin B culture time = 72h Analysis of chromosomal aberrations Analysis of micronuclei

  6. A mitotic cell with chromosomal aberrations ace dic ?

  7. Analysis of chromosomal aberrations by fluorescence in situ hybridization (FISH) chromosome 8 reciprocal translocation chromosome 14 chromosome 2

  8. The frequency of radiation-induced aberrationsis the same in lymphocytes exposed under in vivo and in vitro conditions 0 – 3 Gy 0 – 3 Gy Frequency Y Dose (Gy) A calibration curve

  9. Is it better to analyse unstable aberrations like dicentrics or stable aberrations like translocations? initial damage Dicentric Translocation Dicentric restitution Translocation Micronucleus

  10. How stable with time are dicentrics and translocations? Frequencies of aberrations as function of time post exposure K. Buckton et al., 1983 Aberrations in Lymphocytes of patients withMorbus Bechterew who were treated with radiotherapy cells with dicentrics cells with translocations Percent Years after exposure t1/2 = 3 years Frequency of dicentrics remains stable for several weeks that of translocations – for several years

  11. How to detect partial-body exposure Distribution of radiation-induced dicentrics Whole body exposure Partial body exposure Example of a distribution Number ofaberrations Numberof cells 0 1 2 3 4 5 70 24 5 0 0 0 m = 0,34 ab/cell Overdispersed distribution Poisson distribution var m var m > 1 = 1(dispersion index, relative variance) The degree of deviation from a Poisson distribution allows to assess the size of the exposed part of the body

  12. 11 young frontier guards were exposed to one or several sources ofCs-137 not exceeding 150 GBq at the Lilo military training center 20 km to the east of Tbilisi, from mid 1996 - mid 1997. Autumn 1997: 7 soldiers were treated in Ulm, Germany4 soldiers were treated inParis, France

  13. Patient Acute dose (Gy) Dolphin (Gy) Percent of lymphocytes irradiated Qdr (Gy) Function G (Gy) AN 1.2 ± 0.2 2.3 0.40 2.8 3.1 ± 0.8 EP 1.6 ± 0.3 2.5 0.50 3.4 4.3 ± 1.0 CG 0.7 ± 0.2 - - - 1.0 ± 0.5 TK 0.5 ± 0.2 - - - 0.7 ± 0.4 Problem 1: partial body exposure, Problem 2: chronic exposure ad 1. Dolphin or Qdr methods: allow the reconstruction of dose received by blood which was exposed and the part of the body which was exposed. ad 2. G-function: Dose response relationship:Y = aD + bD2 A coefficient G is added to the parameter b, reducing it to 0, when the DNA repair time exceeds the irradiation time (> 6 hours). The dose-effect curve becomes Y = aD + (Gx)bD2 , where x = t/t0 with t being the time over which the radiation occurred and t0 the mean lifetime of breaks EPR - 4.5  0.3 1.4  0.4 1.5  0.2

  14. The Tokaimura criticality accident September 30, 1999, uranium conversion test plant of JCO Co. Ltd. in Tokai-mura, 115 km northeast from the center of Tokyo. Three workers (A, B and C) were involved in the process of enriching U-235.The criticality chain reaction started when B was pouring uranyl nitrate solution into a tank through a peephole, while A who was standing beside the tank supported the funnel that was inserted into that hole. C, the supervisor, was in the next room.

  15. The problem: extremely high dose, causing mitotic delay of lymphocytes solution: Premature Chromosome Condensation - PCC Phytohaemaglutinine okadaic acid calyculin A harvest slide praparation staining culture time = 48h G2 PCC S PCC

  16. Frequencies of PCC-aberrations in lymphocytes of Tokaimura victims Caclulated doses Doses confirmed by measurement of 24Na (22Na → 24Na) Worker A died after 81 days, worker B after 210 days. Patient C is alive.

  17. Biological dosimetry in accidents during radiotherapy • Problem: • Extreme partial-body exposure • Effect of fractionated doses before accidental exposure In none of the accidents that occurred since the 70-ties until the Bialystok accident was it necessary to apply biological dosimetry for dose reconstruction

  18. The radiological accident at the Białystok Oncology Center 27th February 2001 5 patients treated for mamma Ca (post-operative RT) were exposed to a single dose of 8 MeV electrons patient number number of fractions received before accident 1 1 2 24 3 10 4 21 5 2 Dose measured by the physicist immediately after the accident: 103 Gy Validity of measurement questioned by the manufacturer of the accelerator

  19. Solution: Analysis of aberrations in lymphocytes of breast cancer patients undergoing a correct radiotherapy Problem 1: no appropriate calibration curve available Dose effect curves for aberrations and micronuclei in lymphocytes irradiated in vivo (radiotherapy patients) and in vitro Venkatachalam et al. Mutat. Res. 1999

  20. absorbed energy (J) mass (kg) Problem 2: how to bring the doses absorbed during therapy to a common denominator Absorbed Dose vs Equivalent Whole Body Dose Ein Eex Absorbed dose= 1 Gy = 1 Joul / kg Equivalent whole body dose (EBWD) Ein Eex absorbed energy (J) body mass (kg) EWBD = 1 Gy EWBD = Σ J / body mass

  21. The idea behind the strategy of comparing the aberration frequencies found in lymphocytes of accident patients with the dose-response curve plotted on the basis of data from properly treated breast cancer patients Accident dose dose-response curve of accident patients Frequency of aberrations dose-response curve of proper radiotherapy EWBD

  22. Dose-response curves for accident patients and for control (properly treated) breast cancer patients Wojcik et al. Radiation Research 160: 677-683, 2004

  23. t ½ = 160 000a - CO2 The principle of Electron Paramagnetic Resonance EPR Bone = hydroxyapatite crystals Ca10(PO4)6(OH)2 bound by collagen The paramagnetic centres occur in carbonated apatites= hydroxyapatite crystals where some of the OH- or PO43- have been replaced by carbonate ions CO32- Bone tissue can contain up to 8% of these. Tooth enamel - more.

  24. EPR: Electron Paramagnetic Resonance example of an extrapolation curve

  25. Dose estimation by EPR Accident doses received by Patients 3, 4 and 5 estimated at a tissue depth of 1.9 cm (dmax of 8 MeV electrons). The bottom line values were derived from the physical measurement perfomed by the local medical phisics team immediatelly after the accident. Patient 3 Patient 4 Patient 5 frontal position 59  7 64  11 71  3 distal position 67  8 84  19 78  5 calculation based on physical 103  9 83  9 103  9 measurement

  26. Bialystok accident: frequencies of chromosomal aberrations and doses estimated by EPR Patient 3 EPR analysis 52 - 76 Gy Patient 5 EPR analysis 68 - 83 Gy Patient 2 ? Patient 4 EPR analysis 53 - 103 Gy Patient 1 ? ? Wojcik et al. Radiation Research 160: 677-683, 2004