x Ray Radiation Hazards

8/9/2019 x Ray Radiation Hazards

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Radiation HazardsRadiation HazardsRadiation HazardsRadiation Hazards


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Early EffectsEarly EffectsEarly EffectsEarly Effects

Cells having high mitotic activity are most

radiosensitive1. Skin

2. G.I tract

3. Red bone marrow4. Oropharynx

5. Testes6. ovaries


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Skin lesions affects the basal cells

1. Skin erythema (Reddening)2. Thinning of skin

3. Blistering4. Poorly healing ulcer

5. malignant


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G.I Tract-- Loss of epithelium & impairedrenewal leads to diarrhoea

Testes affects spermatagonia Ovaries mature follicle

Oropharynx- moderate dose

1. Reddening & swelling of laryngeal lining

2. White diptheroid membrane epithelite

3. Large dose slow healing ulceration &fibrosis


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Red bone marrow1. WBC count drops in 2 days

2. Platelets by 6 days3. RBC by 110 days


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Late effectsLate effectsLate effectsLate effects

In High dose1. Carcinogenesis

2. Cataractogenesis3. Life-shortening


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CarcinogenesisCarcinogenesisCarcinogenesisCarcinogenesis

1. Breast cancer mammography

2. Skin cancer superficial x-ray therapy for acne

3. Bone cancer jaw cancer in women doing radium painting of watches

4. Liver cancer Thorotrast injection in angio & hepatography

5. Lung cancer uranium mines workers

6. Thyroid cancer x-ray therapy for enlargedthymus

7. Leukemia


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CataractogenesisCataractogenesisCataractogenesisCataractogenesis

A single ray of 250 rad produces non-progressing cataract, whereas 500 rad

produce progressive cataract

It is a non-stochastic effect


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Life shorteningLife shorteningLife shorteningLife shortening

It is a stochastic effect, i.e as dose wasincreased average survival decreased


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Low dose effects1. Somatic-- Carcinogenesis

2. Genetic-- a) Gene mutationb) Chromosomal aberrations


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1. Somatic-- Carcinogenesis Repetitive small doses of ionizing radiation

do increase the chances of cancer especiallyleukemia in of child whose mother is

exposed to radiation during pregnancy


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A point change in DNA macromolecule iscalledGene mutationGene mutationGene mutationGene mutation

Injury to the chromosomes with resulting

break & structural changes is calledChromosomal aberrationsChromosomal aberrationsChromosomal aberrationsChromosomal aberrations


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Radiation injury to embryo & fetusRadiation injury to embryo & fetusRadiation injury to embryo & fetusRadiation injury to embryo & fetus

Pre-implantation stage (0 to 10 days)small dose of 5-15 rad can kill the embryo, but

surviving embryo are normal except chromosomal

damage

Organogenesis stage (11 to 41 days)

every embryo surviving radiation develops ananomaly especially in organs undergoing most

active multiplication (mitosis) & differentiation

(maturation)


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From 17th day till delivery, neuroblasts,which are very radiosensitive, are present

throughout the CNS & a small dose of 25

rad can be lethal this is reason for such large

CNS anomalies


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Less than 2-3 wks- lethal effect with

absorption, low anomalies4-11 wks severe anomalies of many

organs11-16 wks microcephaly, stunted growth , genital organ

anomalies

16-20 wks mild microcephaly,

stunted growth, mentalretardation

More than 30 wks rare visible abnormalities


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Acute Whole body radiation syndromeAcute Whole body radiation syndromeAcute Whole body radiation syndromeAcute Whole body radiation syndrome

Occurs in industrial accident with highlevel radioactive material, in nuclear plant,explosion of nuclear weapons

1. Sub-clinical syndrome2. Hematopoietic syndrome

3. G.I syndrome4. Neurovascular syndrome


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SubSubSubSub----clinical syndromeclinical syndromeclinical syndromeclinical syndrome

Below 25 rad no change in blood count, butchromosomal aberrations

25-50 rad WBC temporary fall50-200 rad nausea, vomiting, moderate

recoverable WBC count fall


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Hematopoietic syndromeHematopoietic syndromeHematopoietic syndromeHematopoietic syndrome

Exposure 200- 800 rad1. Prodromal 2 hours to 2 days nausea, malaise

2. Latent 2 days to 3 wks bone marrow & lymph

shows loss of cells3. Manifest full blown syndrome

fever,malaise,diarrohea, petechiae, pancytopenia

4. Recovery lower dose 200-300 rad 5wks to 6months incomplete recovery, more than 500 rad

fatal outcome due to severe leucopoenia,

infection & haemorrhage


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G.I syndromeG.I syndromeG.I syndromeG.I syndrome

Exposure 800-5000 rad1. Prodromal within 2 hrs nausea,vomiting

2. Latent may not be present last 2-5 days

3. Manifest 1-2 wks-- fever, increasing diarroheadue to denudation of small bowel liningepithelium, dehydration due to associated no

fluid reabsorption, sepsis, depletion of WBC,shock, death


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Neurovascular syndromeNeurovascular syndromeNeurovascular syndromeNeurovascular syndrome

Exposure 5000 rad Symptoms start in few min nausea, vomiting,

rapid dehydration, drowsiness, ataxia, convulsion

due to cerebral edema, vasculitis & injury tonerves

Death occurs within few days Bone marrow & G.I syndrome may be associated


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Background RadiationBackground RadiationBackground RadiationBackground Radiation

A. External sources1. Cosmic rays

a. primary arising from sunb. secondary cosmic rays --interaction

with nuclei in earth

atmosphere


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2. Natural radioactive minerals within theearth uranium, thorium, actinium

3. Radionuclides carbon 14, hydrogen 3


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B. Internal sources-- natural radioactivenuclides in tissue of body & materials of

detectors K 40, C 14, Pb 210.


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Stochatic effect it is a probability that aparticular effect will occur, usually for small

absorbed dose. Does not have threshold dose

Nonstochastic effect increases in severity withincreasing absorbed dose thereby increasing injury

to normal cells. It has threshold limits & can be

avoided


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ALARA concept As Low As ReasonablyAchievable

Reducing exposure limits further thanrecommended by balancing of benefits vs cost

Planning radiology department protection

Promoting awareness within department


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Protective shielding1. Pocket dosimeter

2. Film badges3. Thermoluminescent dosimeter (TLD)

badges


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Pocket DosimeterPocket DosimeterPocket DosimeterPocket Dosimeter

Resembles fountain pain with in-builtionization chamber & electrometer

Adv- immediate reading Dis-adv easily damaged

unreliable in inexperienced hands


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Film BadgesFilm BadgesFilm BadgesFilm Badges

Dental film with copper & plastic filterswith lead backing

Adv

1. simple to use

2. Inexpensive

3. Readily processed4. Permanent record


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DisadvantagesDamageable

Not reusableLower sensitivity

Error about 10 to 20 %Can be fogged by heat


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TLD BadgesTLD BadgesTLD BadgesTLD Badges

Crystalline material trap electrons in crystallattice which are released in form of light

when heated in controlled condition.

Measured by photomultiplier device

Lithium fluoride is material used


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Advantages1.Very small

2.Sealed in Teflon (less chance of damage)

3.Low exposure limit

4.Accuracy + 5%

5.Less sensitive to heat6.Reusable worn after in 3 months


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Disadvantages

Expensive No permanent record


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Protective MeasuresProtective MeasuresProtective MeasuresProtective Measures

1. Exposure time total dose to a person forparticular rate is directly proportional to

exposure time2. Distance Longer the distance less is exposure

3. Lead barrier thickness of lead barrier is stated

in half-value layer (HLV), decreases exposure toone half


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Dose reduction in RadiographyDose reduction in RadiographyDose reduction in RadiographyDose reduction in Radiography

Beam filtration Aluminium

Beam collimation

Gonadal shieldingHigh speed image receptor

Optimum film processing

High kV

Careful technique selection


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Protection in MammographyProtection in MammographyProtection in MammographyProtection in Mammography

Skillful technique

Dedicated mammographic machine

Molybdenum targets & filters

Low dose mammographic screens & films

Efficient Breast compression device


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Protection in FluoroscopyProtection in FluoroscopyProtection in FluoroscopyProtection in FluoroscopyIntermittent fluoroscopy

Restriction of field size collimationCorrect operating factors increase kVp, decrease

mA decreases, with no change in brightness

Filtration 2.5 mm aluminium filters

Exposure limits 10 R/min in automatic exposure

control & 5 R/min without automatic exposurecontrol

Protective barrier 2mm lead

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x Ray Radiation Hazards