General Pathology

1. Prof.Dr.
Khalil Hassan Zenad
Aljeboori
Copyrights©2017lAliraqiaUniversitylDentistrylPathologylProf.Dr.KhalilHassanZenadAljeboori.
IONIZING RADIATION
Lecture 14

2. Copyrights©2017lAliraqiaUniversitylDentistrylPathologylProf.Dr.KhalilHassanZenadAljeboori.
1. Electromagnetic radiation:
These includes X-Rays have longer waves length than gamma-rays, both penetrating more
than of particulate radiation, passing with many centimeters of tissue, ionizing radiation
form part of normal environment in small amount is harmless, they come from the sun, soil
and bricks, also in some amount in bone (themselves-radioactive carbon), the amount of
radiation use in X-Ray diagnosis is much less than is used in radiotherapy.
2: particulate radiation:
Alpha particles: are rapidly moving nuclei of helium atoms which are emitted such as radium
and thorium or produced by bombardment of elements helium and boron by neutrons.
Beta particles: are rapidly moving electron which emitted naturally from many radioactive
elements, which also be produced by passing high tension currents through cathode ray
tubes.
Both alpha and beta are relatively large and have little penetrating power i.e. up to 2mm of
tissue.
Occur in 2 forms:

3. Copyrights©2017lAliraqiaUniversitylDentistrylPathologylProf.Dr.KhalilHassanZenadAljeboori.
1.natural radioactive substances: include radium, thorium, actinium, and
their products give off radiant energy spontaneously , certain part of this
energy may be inform of electromagnetic waves, but as a role major
portion alpha and beta particles.
2.Artificial radioactive substances: “radioisotopes” isotopes traces in
therapy and traces in diagnosis.
Radiation injuries:
All radiation act in similar fashion on tissues although their power of
penetrating vary, alpha and beta particles have little penetrating ability
are absorbed by superficial of body but gamma rays penetrate deeply in
tissue.
Radioactive substances:

4. Copyrights©2017lAliraqiaUniversitylDentistrylPathologylProf.Dr.KhalilHassanZenadAljeboori.
Its effect depend on:
1. Absorption i.e. the greater absorption of radiation the greater tissue effect,
e.g. gamma rays.
2. Intensity: the effects of radiation depend on intensity of rays absorbed and
the penetrating gamma rays produce the maximal biological results.
3. rate of administration: large doses of short time produce maximal effects
but this result in damage to both normal and abnormal tissue, thus in tumor to
concentrate the dose in tumor mass and minimize the damage to adjacent
tissue.
Irradiation effects:

5. Copyrights©2017lAliraqiaUniversitylDentistrylPathologylProf.Dr.KhalilHassanZenadAljeboori.
1.Radiosensitive: cells killed or seriously injured by 2500 r or less. E.g.: bone
marrow, intestinal epithelia, lymphoid tissue, gonad tissue, tumors, lymphoma
and Ewing’s tumor.
2.Radio resistant: killed by 5000r e.g.: kidney, liver, pancreas, endocrine glands,
bone, cartilage, muscles, brain, tumor melanoma, and sarcoma.
3.Radio responsive : intermediate in sensitivity 2500r to 5000r e.g. : skin, blood
vessels, collagen, elastin, growing bone and cartilage, tumor such as basal cell
carcinoma, cervical carcinoma, thyroid carcinoma.
Tissue changes: tissue divided into 3 groups in respect of their
sensitivity to radiation

6. Copyrights©2017lAliraqiaUniversitylDentistrylPathologylProf.Dr.KhalilHassanZenadAljeboori.
Immediate or early:
1.Radiation burns appear after two weeks.
2.Radiation dermatitis occur secondary to endarteritis obliterans.
3.Radio necrosis.
4.Storage : ingested or injected radioactive elements are stored in various tissues e.g. :
strontium - 90 in bone, iodine – 131 in thyroid.
And may produce chronic eventual effects of delayed nature include :
1.Radio necrosis.
2.Induces malignancy such as squamous cell, basal cell carcinoma of skin, leukemia, bone,
lung, thyroid gland tumors.
3.Aplastic anemia and thrombocytopenia.
4.Genetic abnormalities e.g. mutations and sterility in future generations.
5.Eye damage i.e. cataract.
Result of irradiation:

7. PRESENTATION ENDS
Copyrights © 2017 l Aliraqia University l Dentistry l Pathology l Prof.Dr.
Khalil Hassan Zenad Aljeboori.
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