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PRINCIPLES OF DETECTION OF RADIATION INJURES. Accidental dosimetry PHYSICAL DOSIMETR Y BIOLOGICAL...
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Transcript of PRINCIPLES OF DETECTION OF RADIATION INJURES. Accidental dosimetry PHYSICAL DOSIMETR Y BIOLOGICAL...
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