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BIOLOGICAL EFFECTS OF IONIZING RADIATION ON TISSUES

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BIOLOGICAL EFFECTS OF IONIZING RADIATION ON TISSUES Powered By Docstoc
					BIOLOGICAL EFFECTS
OF IONIZING RADIATION
ON TISSUES, ORGANS
    AND SYSTEMS
  Types of cellular damage

                 Norma         Mutation



                 repair




                           Changes of
Interphase     Mitotic     metabolism
 cell death   cell death   & function
        Radiosensitivity of tissues
   Bone marrow             Skin                    CNS




Highly               Moderately              Least
radiosensitive       radiosensitive          radiosensitive
•Lymphoid tissue     •Skin                   •Central nervous
•Bone marrow         •Vascular endothelium   system (CNS)
•Gastrointestinal    •Lung                   •Muscle
epithelium           •Kidney                 •Bone and cartilage
•Gonads              •Liver                  •Connective tissue
•Embryonic tissues   •Lens (eye)
      Relative radiosensitivity of various organs
          based on parenchymal hypoplasia
           Organs                  Relative radio    Chief mechanism of parenchymal
                                    sensitivity                hypoplasia
Lymphoid organs; bone marrow,          High         Destruction of parenchymal cells, especially
testes & ovaries; small                             the vegetative or differentiating cells
intestines
Embryonic tissue
Skin; cornea & lens of eyes;        Fairly high     Destruction of vegetable and differentiating
gastrointestinal organs: cavity,                    cells of the stratified epithelium
esophagus, stomach, rectum
Growing cartilage; the               Medium         Destruction of proliferating chondroblasts or
vasculature; growing bones                          osteoblasts; damage to the endothelium;
                                                    destruction of connective tissue cells &
                                                    chondroblasts or osteoblasts
Mature cartilage or bone; lungs;     Fairly low     Hypoplasia secondary damage to the fine
kidneys; liver; pancreas;                           vasculature and connective tissue elements
adrenal gland; pituitary gland
Muscle; brain; spinal cord             Low          Hypoplasia secondary damage to the fine
                                                    vasculature and connective tissue elements,
                                                    with little contribution by the direct effects on
                                                    parenchymal tissues
Haematopoietic system




      Bone marrow
     Hierarchical organization
        of haematopoiesis
                     BFU-E        CFU-E
                                            red blood cell
                      BFU-MK      CFU-MK
                                               platelets
     CFU-GEMM                      CFU-M
                    CFU-GM                  monocytes
                                  CFU-G
                                            neutrophils
Stem cell                        CFU-Ba
                                             basophils
                                  CFU-Eo
            CFU-L                            eosinophils
                                  CFU-BL
                                            B lymphocytes
                      Thymus      CFU-TL    T lymphocytes
Proliferation Bone marrow Differentiation       Blood
           Bone marrow kinetics
Normal physiological situation

 Resting    Proliferating       Differentiating     Mature Blood
stem cells compartment:         compartment:         cells
           stem cell and         precursors
            progenitors                                    exit
                                            differentiation
 activation             proliferation,
                        differentiation
  Stem cells: immature cells with autorenewal capability
  Progenitors: primitive cells, high proliferative potential
  Mature cells: no proliferative capability
                  Effects of radiation
                  on haematopoiesis

 Resting          Proliferating    Differentiating   Mature   Blood
stem cells       compartment:      compartment:       cells
                 stem cell and      precursors
    activation    progenitors
I
R                proliferation,    differentiation
R
                 differentiation
A
D
I    Block of                 Depletion by absence of renewal
A    proliferation,
T    cell death         Depletion of
I
O                       proliferating          BLOOD APLASIA
N                       compartment
           Effect of radiation
            on bone marrow




Normal bone marrow   Irradiated bone marrow
                        lacks all precursor
                       haematopoietic cells
Model of blood renewal system
                    Cell pools in normal steady state
                   Stem   Dividing
                                     Maturing
                             &                  Blood
                   cell   maturing     only

                      ?    2 days 1 day 1 day 1 day          Time
                               Transit time
                                                        After Irradiation
                   Changes after irradiation
                                                          1 hour
 Number of Cells




                                                          1 day

                                                          2 days
 Relative




                                                          3 days

                                                          4 1/4 days

                                                          5 days
Erythrocytes changes
as a function of dose

                1 Gy
              3 Gy
Leukocytes changes
as a function of dose



                          Normal
                        <1Gy
                        1-2 Gy
             2-5 Gy
   >5-6 Gy

    Time after exposure, days
Thrombocytes changes
 as a function of dose



                        Normal
                  <1Gy
      2-5 Gy     1-2 Gy


    >5-6 Gy


   Time after exposure, days
             Effects of radiation
             on lymphatic tissue
A                                B




      Normal monkey                  Germinal centre of normal
       lymph node                      monkey lymph node
C                                D




    Lymphoid cells depleted
                                 Germinal centre of irradiated
in cortex of canine lymph node
                                     human lymph node
Early changes in peripheral blood
       lymphocyte counts




                   0.25-1.0 Gy

                   1.0-2.0 Gy

                   2-4 Gy
                   4-6 Gy
                   >6 Gy
Lymphocytes changes
 as a function of dose




             <1 Gy
             1-2 Gy

             2-5 Gy
      >5-6 Gy
Time after exposure, days
Effect of radiation on
gastrointestinal tract




                   Irradiated
                gastrointestinal
                    mucosa
   Pathogenesis of the
gastrointestinal syndrome

             Depletion of the epithelial
              cells lining lumen of
              gastrointestinal tract
             Intestinal bacteria gain
              free access to body
             Haemorrhage through
              denuded areas
             Loss of absorptive
              capacity
Reproductive cell kinetics and
      sterility – male
Reproductive cell kinetics and
     sterility – female
Human skin structure
Penetration of radiation
 through skin stuctures
       Alpha radiation is absorbed in
      superficial layers of dead cells
      within the stratum corneum
      Beta radiation damages epithelial
      basal stratum. High energy ß-
      radiation may affect vascular layer
      of derma, with lesion like thermal
      burn
      Gamma         radiation   damages
      underlying tissues and organs
 Effect of radiation on skin




Normal            Irradiated
           Pulmonary effects




Irradiated lung tissue   Pulmonary fibrosis
         Summary of lecture
 Bone marrow consists of progenitor and stem
  cells, the most radiosensitive cells in the human
  body and the most important in controlling
  infection
 Doses in tens of gray produce central nervous
  system syndrome, causing death before
  appearance of the haematopoietic or
  gastrointestinal syndromes
 The latter syndromes may occur after doses of as
  low as 2.5 and 8 Gy, respectively. Lesions in the
  brain are usually caused by damage to the
  vascular endothelium
 Lung lesions do not usually appear at radiation
  doses less than 10 Gy. Significant concern in
  partial-body irradiation and in radiation therapy
         Lecture is ended


   THANKS FOR ATTENTION


                In lecture materials
of the International Atomic Energy Agency (IAEA),
 kindly given by doctor Elena Buglova, were used

				
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posted:11/12/2011
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