Radiation injury

1. Radiation injury
28th feb 2007

2. Radiation is energy distributed
across the electromagnetic
spectrum as waves or particles

3.  Wave form
penetrating power and ionizing power varies
-radio waves
-microwaves
-infrared
-visible light
-UV
-X ray & gamma ray
-cosmic rays

4.  PARTICULATE RADIATION
Movement of sub atomic particles
Decay of radio active substances
- α particles
- ß particles
- protons, deuterons, meson

5. Sources
 NATURAL
Cosmic radiation
Terrestrial radiation
Internal radiation
 ARTIFICIAL
Medical diagnosis & research
fallouts from nuclear power production and nuclear
weapons
consumer products

6. Measurements of radiation
 Roentgen - Unit of charge produced, as these rays
ionize a given volume of air
 Rad – dose of radiation that will result in the
absorption of 100 ergs of energy per gram of
absorbing substance
 Gray- dose of any form of radiation resulting in the
absorption of 1 J of energy per kg of absorbing
substance
 Rem- dose of any type of radiation that produces a
biologic effect equivalent to 1 rad of X ray or gamma
ray

7. Effects of radiation
 >10 Gray – overt necrosis
 1 – 2 Gray – kills proliferating cells
 <0.5 Gray – no histopathologic effects

8.  Lower doses sub cellular damage occurs
primarily targeting DNA
 If irreparable damage occurs, cells undergo
apoptosis
 Survived cells may show delayed effects
mutation
chromosome aberration
genetic instability

9. Cellular & histological basis of
injury
 ACUTE EFFECTS
Direct effect on DNA
Indirect – Oxygen derived free radicals
- soluble products derived from
peroxidized lipids
-Cross links in DNA strands
-Oxidation & degradation of bases
-Cleavage of sugar phosphate bonds
-Single /double stranded DNA breaks

10.  DELAYED EFFECTS
 FIBROSIS
Ischemic injury caused by vascular damage
death of parenchymal cells
deletion of stem cells
upregulation of chemokines & fibroblast
activation factors

11.  CARCINOGENESIS
Skin cancer
leukemia
osteosarcoma
lung cancer

12. Clinical features of radiation injury

13. Acute whole body exposure
 Prodromal syndrome
<200 rem ; lymphocyte count <1500/μL
 Hematopoetic syndrome
200 – 600 rem ; lymphocyte <1000
petechiae , nausea , vomiting

14.  GI syndrome
600 – 1000 rem
vomiting, diarrhoea, electrolyte imbalance
bacteremia
severe neutrophil platelet depletion
lymphocyte count <500

15.  CNS Syndrome
>1000 rem
intractable nausea & vomiting
confusion, apathy, convulsion, coma
absent lymphocytes

16. Effect of radiotherapy
 Upto 40 – 70 Gray
 Acute radiation syndrome

17. Effect on growth and development
 4 susceptible phases are
pre implantation embryo
stages of organogenesis
fetal period
post natal period

18. Blood vessels
 Endothelial damage
 Sub intimal fibrosis
 Fibrosis of muscle wall
 Capillary changes
thrombosed & obliterated
ectatic

19. Skin
 Hair follicles & epidermis
 Radiation dermatitis
s/c vessels weakened and dilated
dense collagen in dermis
impaired wound healing
infections

20.  HEART
Constrictive pericarditis
Injury to coronary arteries & capillaries
 LUNG
Acute lung injury
Radiation pneumonitis

21.  KIDNEY
Peritubular fibrosis
vascular damage
hyalinisation of glomeruli

22. GIT
 a/c
esophagitis, gastritis, enteritis, colitis,
proctitis
 c/c
ischemia d/t vessel involvement
fibrosis
stricture

23.  Gonads
 Eyes

24. UV Radiation

25. UV Radiation
 Epidemiological evidence of increased incidence
of
-basal cell carcinoma
-squamous cell carcinoma
-? Malignant melanoma
 Common in whites
- melanin layer has a protective value

26.  UV A – 320 – 400 nm
 UV B – 290 – 320 nm
 UV C – 200 – 290 nm

27. Cellular changes
 Inhibition of cell division
 Inactivation of enzymes
 Induction of mutation
 Cell death

28. carcinogenecity
 Pyrimidine dimers in DNA
 Nucleotide excision repair
-recognition of DNA lesion
-incision of damaged strand on both sides
of lesion
-removal of damaged nucleotide
-synthesis of nucleotide patch
-ligation

29.  UV B Causes mutation of oncogenes & tumor
suppressor genes
-p53, RAS

30.  ACUTE EFFECTS
erythema
depletion of langerhans layer
pigmentation
dermal inflammation
 DELAYED EFFECTS
loss of dermal collagen- wrinkling of skin
DNA damage- formation of pyrimidine
dimers
single strand break, DNA cross links

31. THANK YOU...