PRINCIPLES OF DETECTION OF RADIATION INJURES

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PRINCIPLES OF DETECTION OF RADIATION INJURES
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Accidental dosimetry
BIOLOGICAL DOSIMETRY
PHYSICAL DOSIMETRY
CLINICAL DOSIMETRY
CYTOGENETIC DOSIMETRY Dicentrics, FISH, PCC, MNA
DOSE RECONSTRUCTION, Personal Dosimeters
NAUSEA, VOMITING, BLOOD CELLS COUNTS, SKIN
REACTIONS...
OTHER BIOINDICATORS
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Physical dosimetry
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Instruments for detecting and measuring radiation

• Survey meters
• Geiger-Mueller (GM) instruments
• Ionization chamber instruments
• Scintilation instruments
• Laboratory counters
• Personnel dosimeters
• Photographic film dosimeters
• Thermoluminescent dosimeters
• Pocket dosimeters

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Primary use of radiation instrument

• Level of radioactive contamination
• Radiation dose rate in area
• Identity and quantity of radioactive material
• Accumulated dose to individuals in area

Survey meters
Laboratory counters
Personnel dosimeters
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Personnel dosimeters
Electronic dosimeter
Film badge
TLD
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Photographic film dosimeters

• Advantages
• Permanent record
• Energy and nature of exposure
• Cost

• Disadvantages
• Energy dependence
• Fading
• Size

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Thermoluminescent dosimeters
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Pocket dosimeters
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Digital pocket dosimeter
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Clinical dosimetry
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Clinical and laboratory sings of acute radiation
syndrome

• Prodromal clinical effects
• Time of onset
• Degree of symptoms
• Haematological changes
• Lymphocyte counts
• Leukocytes counts
• Biological dosimetry

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Clinical dosimetry at radiation vomiting
Crude estimate of absorbed dose obtainable from
clinical presentation

• Vomiting
• Onset 2 h after exposure or later
• Onset 1-2 h after exposure or later
• Onset earlier than 1 h after exposure
• Onset earlier than 30 min after exposure

MILD ARS (1-2 Gy)
MODERATE ARS (2-4 Gy)
SEVERE ARS (4-6 Gy)
VERY SEVERE ARS (6-8 Gy)
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Radiation dose under 5 Gy

• No immediate life-threatening hazard exists
• Prodromal symptoms of moderate severity
• Onset gt 1 hour
• Duration lt 24 hours

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Fatal radiation

• Nausea and vomiting within minutes (during the
  first hour)
• Within hours (on the first day)
• Explosive bloody diarrhoea
• Hyperthermia
• Hypotension
• Erythema
• Neurological signs

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Triage categories of radiation injuries
according to early symptoms
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Guide for management of radiation injuries on
the basis of early symptoms
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Clinical signs of skin injury depending on dose
of radiation exposure
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Laboratory dosimetry using early changes in
lymphocyte counts
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Change of lymphocytes counts depending on dose of
acute whole body exposure
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Laboratory dosimetry using granulocyte counts
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Cytogenetic dosimetry
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Cytogenetic dosimetry

• Analysis of chromosomal aberrations in peripheral
  blood lymphocytes - widely used biological
  dosimetry method for assessing radiation dose,
  especially useful
• in persons not wearing dosimeters while exposed
  to radiation
• in cases of claims for compensation for
  radiation injuries not supported by unequivocal
  dosimetric evidence
• for validation of occupational radioprotection
  cases involving suspected low-dose exposures

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Biophysical background to chromosome damage
High LET



Low LET
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Classification of chromosomal aberrations
Asymmetrical (UNSTABLE)
Breaks
Symmetrical (STABLE)
Centric Ring
Inversion
Intrachange
Interchange
Translocation
Dicentric
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Biological dose assessment using standard
dicentric analysis

• Introduced by M. Bender in 1964
• Isolated lymphocytes stimulated by
  phytohaemagglutin (PHA) into mitosis
• Arrest of metaphase using colchicine
• Scoring of dicentric chromosome aberrations in
  metaphase spreads

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Dicentric chromosome aberrations in metaphase
spreads
dic
f
dic
f
f
f
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Dose curves at high LET and low LET radiation
Y AaD bD2
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Dose curves at acute and chronic exposure
Gamma rays, X-rays acute exposure (Low LET)
? particles Fast neutrons (High LET)
Y c aD
Y c aD bD2
Effect
Dicentric yield
Y c aD
Gamma rays X-rays chronic exposure (Low LET)
Dose
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Dose estimation of a partial body radiation
exposure (non-uniform irradiation)
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Dicentric assay

• Most accurate method for dose estimation with
  sensitivity threshold of about 0.1 Gy for whole
  body low LET radiation
• Especially useful
• in cases where dosimeter not used, e.g.
  radiation accident
• to support physical dosimetry results in
  radiation protection and safety practice
• to determine partial body exposure not detected
  by locally placed dosimeter

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Limitations of dicentric analysis for dose
estimation

• Dicentrics are unstable and lymphocytes carrying
  aberration elimininated with time (average
  lifetime 150-220 days, depending on dose), hence
  can underestimate magnitude of dose
• Method useful only within few months of
  irradiation

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Translocation assay

• In retrospective dosimetry and chronic exposure
  reciprocal translocations used for dose
  assessment
• Translocations considered stable in cell division
  so yield should not fall with time
• Typically detected using specific whole
  chromosome DNA hybridization probes and FISH
  methodology

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Stable chromosome aberration analysis with
G-banding
An idiogram showing the banding patterns of
individual chromosomes by fluorescent and Giemsa
staining
A normal G banded male karyotype
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Stable chromosome aberration analysis with FISH
Translocation
Deletion
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Applicability of stable chromosome aberration
analysis for biological dosimetry

• Method based on scoring stable chromosome
  aberrations (translocations and insertions)
  detected with fluorescent in-situ hybridization
  of whole chromosomes
• Requires complex procedures and technical
  equipment
• May be use decades after exposure

• Sensitivity threshold a few cGy but method not
  feasible for doses less than 0.2 Gy because of
  expense and time needed for analysis
• Spontaneous level of stable chromosome
  aberrations not well established

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Premature chromosome condensation (PCC) assay

• Initially introduced by Johnson and Rao (1970)
• Mitotic-inducer cells (i.e. CHO) isolated using
  chemical (colcemid) and physical (rapid shaking
  of flask) technique
• Test cells (i.e. human lymphocytes) fused with
  CHO cells using polyethylene glycol (PEG)
• Interphase DNA of test cells condense into
  chromatid/chromosome-like structures (46 for
  non-irradiated human cells)

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PCC technique
CHINESE HAMSTER OVARY (CHO) CELLS (Grown in
BrdU) COLCEMID MITOTIC SHAKE
OFF (METAPHASE CELLS)
FUSE IN PEG
PERIPHERAL BLOOD
CHO
LYMPHOCYTES
FICOL SEPARATION
Incubate 1 h (MediumPHAColcemid)
PCC
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PCCs and FISH
Irradiated cells with excess break
Unirradiated control
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Estimation of irradiated body fractions
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Applicability of PCC assay for biological
dosimetry

• Dose estimates obtainable within 48 hours of
  receipt of blood in laboratory
• Radiation induced mitotic delay does not
  interfere with assay since performed on
  interphase nuclei and does not require cell
  division
• Method envisioned applicable after partial-body /
  supra-lethal exposure and improves detection
  level of lower doses

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Micronucleus assay
Cytochalasin B
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Micronucleus and nucleoplasmic bridges in
binucleated cells
B
A
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Micronucleus assay with pancentromeric probe
A
B
centromere positive
centromere negative
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Application of micronucleus assay for biological
dosimetry

• Micronucleus not specific to radiation exposure
• Discrimination between total and partial body
  exposure more difficult
• High doses of radiation interfere with cell
  division
• High baseline frequency and age dependency make
  reliability of assay questionable

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Glycophorin A (GPA) somatic cell mutation assay

• Performed by two-color immunofluorescence flow
  cytometry on peripheral blood erythrocytes
• Based of measuring N/0 variants of erythrocytes,
  which display phenotype consistent with loss of
  expression of GPA (M) allele
• Can be performed only on individuals
  heterozygous at this locus that codes for the N/M
  blood group antigens (approximately half of
  population)
• Prompt but requires complex and expensive
  equipment
• Sensitivity threshold about 0.2-0.25 Gy

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Application of GPA assay for biological
dosimetry
Relationship between glycophorin A mutant
frequency in red blood cells and radiation dose
for about 1200 A-bomb survivors
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Biophysical assays - ESR (electron spin
resonance)

• Persistent free radicals formed in solid matrix
  biomaterial (e.g. dental enamel, nail clippings,
  hair) from accidentally exposed victim can be
  detected via ESR
• Measurements provide reliable biophysical dose
  estimates and partial body exposure information
• In some circumstances, certain clothing material,
  particularly hard plastics and buttons, may be
  measured and absorbed dose estimated

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Characterization of biological dosimetry methods
 
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Summary of lecture

• In radiation accidents, important to estimate
  the absorbed doses in victims to plan appropriate
  medical treatment
• In most accidents, physical dosimetry of
  absorbed dose is not possible. Even where
  possible, important to confirm the estimates by
  other methods
• Most commonly used method cytogenetic analysis
  of chromosomal aberration in peripheral blood
  lymphocytes using dicentrics, translocations, PCC
  and micronuclei assays

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Lecture is ended
THANKS FOR ATTENTION
In lecture materials of the International Atomic
Energy Agency (IAEA), kindly given by doctor
Elena Buglova, were used