PRINCIPLES OF DPRINCIPLES OF DETECTIONETECTION

OF RADIATION INJURESOF RADIATION INJURES

Accidental Accidental dosimetrydosimetry

PHYSICAL DOSIMETR

Y

BIOLOGICALDOSIMETRY

CLINICALDOSIMETRY

DOSE RECONSTRUCTION,

Personal Dosimeters

CYTOGENETIC DOSIMETRY

Dicentrics, FISH, PCC, MNA

NAUSEA, VOMITING,

BLOOD CELLS COUNTS,

SKIN REACTIONS...

OTHER BIOINDICATOR

S

PhysicalPhysical dosimetrydosimetry

Instruments for Instruments for ddetecting etecting and and mmeasuring easuring rradiationadiation

Survey metersSurvey meters Geiger-Mueller (GM) Geiger-Mueller (GM)

instrumentsinstruments Ionization chamber instrumentsIonization chamber instruments Scintilation instrumentsScintilation instruments

Laboratory countersLaboratory counters Personnel dosimetersPersonnel dosimeters

Photographic film dosimetersPhotographic film dosimeters Thermoluminescent dosimetersThermoluminescent dosimeters Pocket dosimetersPocket dosimeters

Primary Primary uuse of se of rradiation adiation iinstrumentnstrument

Level of radioactive Level of radioactive contamination contamination

Radiation dose rate Radiation dose rate in areain area

Identity and Identity and quantity of quantity of radioactive materialradioactive material

Accumulated dose Accumulated dose to individuals into individuals in areaarea

Survey meters

Laboratory counters

Personnel dosimeters

Personnel Personnel ddosimetersosimeters

TLD

Filmbadge

Electronic dosimeter

Photographic Photographic ffilm ilm ddosimetersosimeters

AdvantagesAdvantages Permanent Permanent

recordrecord Energy and Energy and

nature of nature of exposureexposure

CostCost

DisadvantagesDisadvantages Energy Energy

dependencedependence FadingFading SizeSize

Thermoluminescent Thermoluminescent ddosimetersosimeters

Pocket Pocket ddosimetersosimeters

Digital Digital ppocket ocket ddosimeterosimeter

Clinical dosimetryClinical dosimetry

Clinical and laboratory Clinical and laboratory sings sings

of acute radiation of acute radiation syndromesyndrome Prodromal Prodromal clinical clinical

eeffectsffects Time of onsetTime of onset Degree of symptomsDegree of symptoms

HHaematological aematological cchangeshanges Lymphocyte countsLymphocyte counts Leukocytes countsLeukocytes counts Biological Biological ddosimetryosimetry

ClinicalClinical dosimetry dosimetry at radiation vomitingat radiation vomiting

Crude estimate of absorbed dose obtainable from clinical presentation

VomitingOnset: 2 h after exposure or later

Onset: 1-2 h after exposure or later

Onset: earlier than 1 h after exposureOnset: 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 Radiation ddose ose uunder 5 nder 5 GyGy

No immediate life-threatening hazard exists

Prodromal symptoms of moderate severityOnset > 1 hourDuration < 24 hours

Fatal Fatal rradiationadiationNausea and vomiting within

minutes (during the first hour)

Within hours (on the first day):Within hours (on the first day): EExplosive bloody diarrhoeaxplosive bloody diarrhoea Hyperthermia Hyperthermia Hypotension Hypotension ErythemaErythema Neurological Neurological ssignsigns

Triage Triage ccategories of ategories of rradiation adiation iinjuries njuries aaccording to ccording to eearly arly

ssymptomsymptoms

Guide for management of radiation injuries on the basis

of early symptomsNo vomiting Vomiting 2-3 hafter exposure Vomiting 1-2 hafter exposure 

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

Stage/symptoms Dose range (Gy)

Time of onset

Erythema Epilation Dry desquamation Moist desquamation Blister formation Ulceration (within skin) Necrosis (deeper penetration)

3-10 > 3 8- 12 15-20 15-25 > 20 25

2-3 weeks 14-18 days 25-30 days 20-28 days 15-25 days 2-3 weeks 3 weeks

Clinical signs of skin injury Clinical signs of skin injury depending on dose of radiation depending on dose of radiation

exposureexposure

Laboratory dosimetry using early changes in lymphocyte

counts

Change Change of of lymphocyteslymphocytes counts counts depending depending oon dose n dose oof acute f acute

whole body exposurewhole body exposureDegree of Degree of

ARSARSDose Dose (Gy)(Gy)

Lymphocyte Lymphocyte counts (cells/counts (cells/L)L)

2 days after first exposure

Preclinical Preclinical phasephaseMildMildModerateModerateSevereSevereVery severeVery severeLethalLethal

0.1-1.0

1.0-2.02.0-4.04.0-6.06.0-8.0

>8.0

1500-2500

700-1500500-800300-500100-300

0-50

LaboratoryLaboratory ddosimetry osimetry uusing sing ggranulocyte ranulocyte ccountsounts

Cytogenetic dosCytogenetic dosimetryimetry

Cytogenetic dosCytogenetic dosimetryimetryAnalysis 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

BBiophysical iophysical bbackground ackground to to cchromosome hromosome ddamageamage

**********************************************************High LET

* * * * * * * ** * * * * * * *Low LET

Classification of Classification of cchromosomal hromosomal aaberrationsberrations

Inversion

Symmetrical(STABLE)

Breaks

Intrachange

Asymmetrical(UNSTABLE)

CentricRing

Interchange

Translocation Dicentric

Biological Biological ddose ose aassessment ssessment uusing sing sstandard tandard ddicentric icentric

aanalysisnalysis 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 Dicentric cchromosome hromosome aaberrations in berrations in mmetaphase etaphase

sspreadspreads

dic

dic

f

f

f

f

Dose Dose curves curves at high LET and lowat high LET and low LET LET

radiationradiation

Y = A+D + D2

Gamma rays,

X-rays acute exposure(Low LET)

Gamma raysX-rays chronic exposure

(Low LET)

particlesFast neutrons

(High LET)

Dose

Dic

entr

ic y

ield

Y = c + D + D2

Y = c + D

Y = c + D

Dose Dose curvescurves atat aacute cute andand cchronic hronic

eexposurexposure

Eff

ect

Dose esDose estimatitimationon of a of a partial bodypartial body radiation radiation eexposurexposure (non-uniform (non-uniform

irradiation)irradiation)

DDicentric icentric aassayssay 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 Limitations of ddicentric icentric aanalysis nalysis

for for ddose ose eestimationstimation 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

Translocation assayTranslocation 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

Stable Stable cchromosome hromosome aaberration berration aanalysis with G-bandingnalysis with G-banding

A normal G banded male karyotype

An idiogram showing the banding patterns of individual chromosomes by fluorescent and Giemsa staining

Stable chromosome aberration analysis with

FISH

Translocation

Deletion

Applicability of Applicability of sstabletable cchromosome hromosome

aaberration berration aanalysis for nalysis for bbiological iological ddosimetryosimetry

• 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

Premature Premature cchromosome hromosome ccondensation (PCC) ondensation (PCC) aassayssay

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 PCC ttechniqueechnique

PERIPHERAL BLOOD

FICOL SEPARATION

FUSE IN PEG

LYMPHOCYTES CHO

CHINESE HAMSTEROVARY (CHO) CELLS (Grown in BrdU)

COLCEMID

MITOTIC SHAKE OFF(METAPHASE CELLS)

PCC

Incubate 1 h(Medium+PHA+Colcemid)

PCCs and FISH

Irradiated cells with excess break

Unirradiated control

Estimation of Estimation of iirradiated rradiated bbody ody ffractionsractions

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

Micronucleus Micronucleus aassayssay

Cytochalasin B

Micronucleus and nucleoplasmic bridges in

binucleated cells

A B

Micronucleus assay with pancentromeric probe

A B

centromere negative centromere positive

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

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 GPA assay for biological dosimetry

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

Biophysical assaysBiophysical assays - - ESRESR ((electron spin resonanceelectron 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

 

Characterization of biological dosimetry methods

Summary of lectureSummary 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 endedLecture is ended

THANKS FOR ATTENTION

In lecture materials of the International Atomic Energy Agency

(IAEA), kindly given by doctor Elena Buglova, were

used