Biological Effects of Ionizing RadiationBiological Effects of Ionizing RadiationDeterministic effectsDeterministic effects

Effects of partial body irradiationEffects of partial body irradiationLectureLecture

IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources

IAEA Post Graduate Educational Course in Radiation Protection and Safety of Radiation Sources

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IntroductionIntroduction

Partial body irradiation may cause local Partial body irradiation may cause local radiation injury of the part of the bodyradiation injury of the part of the body

Sources of data for deterministic effects in Sources of data for deterministic effects in man:man: side effects of radiotherapyside effects of radiotherapy effects on the early radiologistseffects on the early radiologists effects amongst survivors of the atomic effects amongst survivors of the atomic

bombs at Hiroshima and Nagasaki in Japan bombs at Hiroshima and Nagasaki in Japan consequences of severe accidentsconsequences of severe accidents

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ContentContent

TThreshold doses for deterministic hreshold doses for deterministic effects in different organseffects in different organs

Radiation-induced damage of the:Radiation-induced damage of the: SkinSkin EyeEye LungLung GonadsGonads ThyroidThyroid SkeletonSkeleton

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OverviewOverview

Partial body irradiation may cause Partial body irradiation may cause local radiation injury of the part of local radiation injury of the part of the bodythe body

Possible target:Possible target: SkinSkin ThyroidThyroid LungLung Eye lensEye lens Gonads, etcGonads, etc

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Threshold of Threshold of ooccurrenceccurrence for local for local injuryinjury

Organ or Organ or tissuetissue

Dose in Dose in less thanless than 2 2 daysdays, , GyGy

Deterministic effectsDeterministic effects

Type of effectType of effect Time of Time of

occurrenceoccurrence

SkinSkin 33 ErythemaErythema 1 – 3 weeks1 – 3 weeks

ThyroidThyroid 55 HypothyroidismHypothyroidism 1st – several 1st – several yearsyears

Lens of the Lens of the eyeeye

22 CataractCataract 6 months - 6 months - several yearsseveral years

GonadsGonads 33Permanent Permanent sterilitysterility

weeksweeks

LungLung 88 PPnneeumonitisumonitis 1-3 months1-3 months

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Time of Onset of Clinical Signs of Skin Time of Onset of Clinical Signs of Skin Injury Injury vsvs Dose Received Dose Received

SymptomsSymptoms Dose range Dose range Time of Time of oonset nset

(Gy) (Gy) (day) (day)

ErythemaErythema 3-10 3-10 14-21 14-21

EpilationEpilation >3 >3 14-18 14-18

Dry desquamationDry desquamation 8-12 8-12 25-30 25-30

Moist desquamationMoist desquamation 15-2015-20 20-28 20-28

Blister formationBlister formation 15-25 15-25 15-25 15-25

Ulceration Ulceration >20 >20 14-21 14-21

Necrosis Necrosis >25 >25 >21 >21

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Radiation injury of the skin: acute Radiation injury of the skin: acute phasephase Inflammation: Inflammation: redness (erythema), swelling redness (erythema), swelling

(oedema), elevated temperature (oedema), elevated temperature Passive tissue compression: Passive tissue compression: thrombosis,thrombosis,

circulation disorderscirculation disorders (insufficient blood supply)(insufficient blood supply) Tissue atrophy, necrosis:Tissue atrophy, necrosis: pain, acute ulcerationpain, acute ulceration

mmoderate doses ( > 20 Gy): oderate doses ( > 20 Gy): eepidermal cell depletion pidermal cell depletion (denudation) due to the mitotic death of the(denudation) due to the mitotic death of the epidermal epidermal cells basal and viable upper layers with consecutive dry cells basal and viable upper layers with consecutive dry oror moist desquamation, blistering of the epidermis and moist desquamation, blistering of the epidermis and secondary dermal secondary dermal uulcerationlceration

vvery high doses (>100 Gy surface dose): ery high doses (>100 Gy surface dose): aacute dermal cute dermal necrosis within 2-3 weeks (interphase death of necrosis within 2-3 weeks (interphase death of endothelial and fibroblast type cells; sometimesendothelial and fibroblast type cells; sometimes moist moist desquamation and blisters)desquamation and blisters)

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Radiation injury of the skin: late Radiation injury of the skin: late phasephase

Epidermal and dermal atrophy: (Epidermal and dermal atrophy: (fragilefragile skin) skin) Insufficient blood supplyInsufficient blood supply Late necrosis with skin ulcerationLate necrosis with skin ulceration Occlusion of lymphatic vessels with local lymph Occlusion of lymphatic vessels with local lymph

stagnation: stagnation: pain, late oedemapain, late oedema Hyperkeratotic and fibrotic degeneration of the Hyperkeratotic and fibrotic degeneration of the

skinskin Decreased immunological defence of the skin Decreased immunological defence of the skin

with increased sensitivity against infectionswith increased sensitivity against infections, etc, etc Persistent or recurring pain Persistent or recurring pain Increased risk of skin malignanciesIncreased risk of skin malignancies

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Radiation injury of the eyeRadiation injury of the eye

Observations:Observations: X-ray treatment of eye tumorsX-ray treatment of eye tumors

Radiation injuries:Radiation injuries: Lid erythemaLid erythema ConjunctivitisConjunctivitis CataractCataract RetinopathyRetinopathy

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CataractCataract

Cataract Cataract - - any detectable change of the any detectable change of the normally transparent normally transparent llens of the eyeens of the eye

Reason of development:Reason of development: SSome abnormal metabolic disorderome abnormal metabolic disorder CChronic ocular infectionhronic ocular infection TraumaTrauma Old ageOld age Ionizing radiation (radiation-induced cataract)Ionizing radiation (radiation-induced cataract)

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Radiation-induced cataractRadiation-induced cataract

TThe threshold dose following a single exposure he threshold dose following a single exposure of low-LET radiation is 2 Gy, for neutrons 0.2 Gyof low-LET radiation is 2 Gy, for neutrons 0.2 Gy

Lowering the dose rate or extending the exposure Lowering the dose rate or extending the exposure period increases the EDperiod increases the ED5050 value to an average of value to an average of 9.3 Gy9.3 Gy

Estimated latency periods: 6 month to 35 yearsEstimated latency periods: 6 month to 35 years Doses of less than 0.1 Sv/year are not thought to Doses of less than 0.1 Sv/year are not thought to

present appreciable risk for detectable visual present appreciable risk for detectable visual impairmentimpairment

OOccupational exposure limit for the eye is 0.15 Sv ccupational exposure limit for the eye is 0.15 Sv (ICRP-60)(ICRP-60)

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Radiation-induced retinopathyRadiation-induced retinopathy

TThreshold dose of retinal damage: 15 - 35 Gy hreshold dose of retinal damage: 15 - 35 Gy depending ondepending on: : radiation quality, dose rate, radiation quality, dose rate, fractionation, fraction sizefractionation, fraction size tthreshold for visual impairment: ~ 50 Gy hreshold for visual impairment: ~ 50 Gy ooccurrence: 35 Gy ~ 10%; 45 Gy ~ 66 %; 80 Gy ~ 100 %ccurrence: 35 Gy ~ 10%; 45 Gy ~ 66 %; 80 Gy ~ 100 %

Latency period: 6 months to 3 yearsLatency period: 6 months to 3 years Clinical manifestation:Clinical manifestation:

mmicroaneurysms of the capillariesicroaneurysms of the capillaries ““cotton-wool spots”cotton-wool spots” intraretinal haemorrhages, and intraretinal haemorrhages, and leakage of retinal vessels with exudatesleakage of retinal vessels with exudates

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Radiation-induced hypothyroidismRadiation-induced hypothyroidism

Threshold dose – 5 Gy of acute Threshold dose – 5 Gy of acute exposure within 2 daysexposure within 2 days

Latent period – yearsLatent period – years Pathophysiological mechanism Pathophysiological mechanism

involved:involved: direct lesions to follicular cellsdirect lesions to follicular cells alterations of vascular systemalterations of vascular system immunological reactionsimmunological reactions

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Deterministic radiation injury of Deterministic radiation injury of the lungthe lung

PheumonitisPheumonitis Threshold dose – 8 Gy of acute Threshold dose – 8 Gy of acute

exposureexposure Latent period – 1-3 monthsLatent period – 1-3 months

Fibrosis Fibrosis At the late stage and as a consequence At the late stage and as a consequence

of acute pneumonitisof acute pneumonitis Latent period – 6 monthsLatent period – 6 months

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Radiation-induced pulmonary Radiation-induced pulmonary reactionsreactions Phases of development:Phases of development:

LatencyLatency degenerative changes of pneumocytes and of

endothelial cells Acute pneumonitisAcute pneumonitis

dose-dependent leakage of proteins in the alveolar space

thickening of alveolar septa oedema of the interstitium, and changes to the capillaries in the number of type II

pneumocytes and alveolar macrophages Fibrosis Fibrosis

capillary loss further decrease in the number of type I pneumocytes increased collagen deposition

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Deterministic radiation injury of Deterministic radiation injury of the gonadsthe gonads

Sterility:Sterility: TemporaryTemporary PermanentPermanent

Target organ:Target organ: TestesTestes Ovarium Ovarium

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Deterministic radiation injury of Deterministic radiation injury of the gonads (Cont’d)the gonads (Cont’d)

Organ Organ / consequence / consequence of exposureof exposure

Threshold absorbed dose of Threshold absorbed dose of exposureexposure

Acute, SvAcute, Sv Protracted, Sv/yearProtracted, Sv/year

TestesTestes temporary sterilitytemporary sterility permanent sterilitypermanent sterility

0.150.15

3.03.0

0.40.4

2.02.0

OvaryOvary permanent sterilitypermanent sterility

2.52.5 0.20.2

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Deterministic radiation injury of Deterministic radiation injury of the skeletonthe skeleton

Threshold dose – 5-10 GyThreshold dose – 5-10 Gy Children bones are more sensitiveChildren bones are more sensitive The severity of radiation-induced damage The severity of radiation-induced damage

to growing bone depends on:to growing bone depends on: the total radiation dosethe total radiation dose fractionationfractionation dose homogeneitydose homogeneity volume irradiatedvolume irradiated symmetry of the volume irradiatedsymmetry of the volume irradiated patient's age, etcpatient's age, etc

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SummarySummary

This lecture presented materials about This lecture presented materials about effects of partial body irradiationeffects of partial body irradiation

The following topics were covered in The following topics were covered in the lecture: threshold doses for the lecture: threshold doses for deterministic effects in different deterministic effects in different organs, radiation-induced damage of organs, radiation-induced damage of the skin, eye, lung, gonads, thyroid and the skin, eye, lung, gonads, thyroid and skeleton skeleton

Comments are welcomedComments are welcomed

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Where to Get More InformationWhere to Get More Information UNSCEAR, Sources and Effects of UNSCEAR, Sources and Effects of

Ionizing Radiation, 2000 Report to the Ionizing Radiation, 2000 Report to the General Assembly with Scientific General Assembly with Scientific Annexes, United Nations, New York,2000Annexes, United Nations, New York,2000

IAEAIAEA - WHO. Diagnosis and treatment of - WHO. Diagnosis and treatment of radiation injuries, Safety Reports Series radiation injuries, Safety Reports Series No. 2, IAEA, Vienna, 1998No. 2, IAEA, Vienna, 1998

Hopewell JW. The skin: It's structure and Hopewell JW. The skin: It's structure and response to ionizing radiation. Int J response to ionizing radiation. Int J Radiat Biol 1990; 57:751-73Radiat Biol 1990; 57:751-73