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PRINCIPLES OF D ETECTION OF RADIATION INJURES. Accidental dosimetry. BIOLOGICAL DOSIMETRY. PHYSICAL DOSIMETRY. CLINICAL DOSIMETRY. CYTOGENETIC DOSIMETRY Dicentrics, FISH, PCC, MN A . DOSE RECONSTRUCTION , Personal Dosimeters. NAUSEA, V OMITING, BLOOD CELLS COUNTS,

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PRINCIPLES OF DETECTIONOF RADIATION INJURES


Accidental dosimetry

BIOLOGICAL

DOSIMETRY

PHYSICAL

DOSIMETRY

CLINICAL

DOSIMETRY

CYTOGENETIC DOSIMETRY

Dicentrics,FISH,

PCC, MNA

DOSE

RECONSTRUCTION,

Personal Dosimeters

NAUSEA, VOMITING,

BLOOD CELLS COUNTS,

SKINREACTIONS...

OTHER BIOINDICATORS


Physicaldosimetry


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


Level of radioactive contamination

Radiation dose rate in area

Identity and quantity of radioactive material

Accumulated dose to individuals inarea

Primary use of radiation instrument

Survey meters

Laboratory counters

Personnel dosimeters


Personnel dosimeters

Electronic dosimeter

Film

badge

TLD


Advantages

Permanent record

Energy and nature of exposure

Cost

Disadvantages

Energy dependence

Fading

Size

Photographic film dosimeters


Thermoluminescent dosimeters


Pocket dosimeters


Digital pocket dosimeter


Clinical dosimetry


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


Clinicaldosimetry 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)


Radiation dose under 5 Gy

  • No immediate life-threatening hazard exists

  • Prodromal symptoms of moderate severity

    • Onset > 1 hour

    • Duration < 24 hours


Fatal radiation

  • Nausea and vomiting within minutes(during the firsthour)

  • Within hours (on the first day):

    • Explosive bloody diarrhoea

    • Hyperthermia

    • Hypotension

    • Erythema

    • Neurological signs


Triage categories of radiation injuries according to early symptoms


No vomiting

Vomiting 2-3 h

after exposure

Vomiting 1-2 h

after exposure 

Vomiting earlier than 1 h, other severe symptoms, like hypotension

hyperthermia,

diarrhea, oedema, erythema, CNS symptoms

< 1 Gy

1-2 Gy

2-4 Gy 

> 4 Gy

Outpatient with 5-week surveillance

Surveillance in a general hospital (or outpatient for 3 weeks) followed by hospitalization

Hospitalization in a hematological department 

Hospitalization in a well equipped hematological or surgical department with transfer to a specialized centre for radiopathology

Guide for management of radiation injuries on the basis of early symptoms


Clinical signs of skin injury depending on dose of radiation exposure


Laboratorydosimetry using early changes in lymphocyte counts


Degree of ARS

Dose (Gy)

Lymphocyte counts (cells/L)

2 days after first exposure

Preclinical phase

Mild

Moderate

Severe

Very severe

Lethal

0.1-1.0

1.0-2.0

2.0-4.0

4.0-6.0

6.0-8.0

>8.0

1500-2500

700-1500

500-800

300-500

100-300

0-50

Change of lymphocytes counts depending on dose of acute whole body exposure


Laboratorydosimetry using granulocyte counts


Cytogenetic dosimetry


Cytogenetic dosimetry

Analysis of chromosomal aberrations in peripheral blood lymphocytes - widely used biologicaldosimetry method forassessing 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


Biophysical background to chromosome damage

High LET

*****************************

* * * * * * * *

Low LET


Classification of chromosomal aberrations

Asymmetrical

(UNSTABLE)

Breaks

Symmetrical

(STABLE)

Centric

Ring

Inversion

Intrachange

Interchange

Translocation

Dicentric


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


Dicentric chromosome aberrations in metaphase spreads

dic

f

dic

f

f

f


Dose curves at high LET and lowLET radiation

Y = A+aD + bD2


Dose curvesatacute andchronic exposure

 particles

Fast neutrons

(High LET)

Gamma rays,

X-rays acute exposure

(Low LET)

Y = c + aD

Y = c + aD + bD2

Effect

Dicentric yield

Y = c + aD

Gamma rays

X-rays chronic exposure

(Low LET)

Dose


Dose estimationof a partial bodyradiation exposure (non-uniform irradiation)


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


Limitations of dicentric analysis for dose estimation

  • Dicentrics are unstable and lymphocytes carryingaberration 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


Translocation assay

  • Inretrospective dosimetryandchronic exposurereciprocal translocations used for dose assessment

  • Translocations consideredstablein cell division so yield should not fall with time

  • Typically detected using specific whole chromosome DNA hybridization probes and FISH methodology


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


Stable chromosome aberration analysis with FISH

Translocation

Deletion


Applicability of stablechromosome 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

  • Sensitivitythreshold 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


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)


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

(Medium+PHA+Colcemid)

PCC


PCCs and FISH

Irradiated cells

with excess break

Unirradiated control


Estimation of irradiated body fractions


Applicability of PCC assayfor biological dosimetry

  • Dose estimates obtainable within48 hours of receipt of blood inlaboratory

  • Radiation inducedmitotic delay does not interfere with assaysince performed on interphase nuclei and does not require cell division

  • Method envisioned applicable afterpartial-body/ supra-lethal exposure and improves detection level oflower doses


Micronucleus assay

Cytochalasin B


Micronucleus and nucleoplasmic bridges in binucleated cells

B

A


Micronucleusassay with pancentromeric probe

A

B

centromere positive

centromere negative


Application of micronucleusassay for biological dosimetry

  • Micronucleus not specific toradiation exposure

  • Discrimination between total and partial body exposure moredifficult

  • High doses of radiation interfere with cell division

  • High baseline frequencyand age dependency make reliability of assay questionable


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


Application of GPAassay for biological dosimetry

Relationship between glycophorin A mutant frequency in red blood cells and radiation dose for about 1200 A-bomb survivors


Biophysical assays - ESR(electron spin resonance)

  • Persistent free radicals formed in solid matrix biomaterial (e.g. dental enamel, nailclippings, 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 plasticsand buttons, may be measured and absorbed dose estimated


Characterization of biological dosimetry methods


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


Lecture is ended

THANKS FOR ATTENTION

In lecture materials

of the International Atomic EnergyAgency (IAEA),

kindly given by doctor Elena Buglova, were used


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