Ionization due to Radiation Effects on Human Body Electron - - PowerPoint PPT Presentation

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Dec 28, 2022 125 likes •218 views

Mechanism of Causing Ionization due to Radiation Effects on Human Body Electron Radiation Enlarged particles Enlarged Where ionization occurs Highdensity ionization particles Cells rays, Xrays Lowdensity

SLIDE 1

Ionization due to Radiation

High‐density ionization Low‐density ionization

α‐particles γ‐rays, X‐rays

Where ionization occurs Electron Radiation Cells

α‐particles

Mechanism of Causing Effects on Human Body

Enlarged Enlarged

SLIDE 2

Damage and Repair of DNA

Repair Damage

Radiation

Repair enzyme

DNA

Complete repair Partial or incomplete repair

Cell Radiation Nucleus DNA Mechanism of Causing Effects on Human Body

SLIDE 3

DNA→Cells→Human Body

Cells Mutation Cell death or cell degeneration Damage (chemical change) Repair enzyme

Possibility of causing acute effects and fetal effects

Incomplete repair Repair succeeded Repair failed

No hazard DNA

Possibility of causing cancer and hereditary effects

Human Body

Mechanism of Causing Effects on Human Body

SLIDE 4

Radiation Damage to DNA

Damage per 1 mGy of X‐rays (per cell) Damage per 1 mGy of X‐rays (per cell)

Cell Radiation

DNA

Radiation Base damage 2.5 locations Single‐strand break 1 location Double‐strand breaks 0.04 locations

Source: Morgan, Annual Meeting of the National Committee on Radiation Protection and Measurements (NCRP) (44th, 2008)

Mechanism of Causing Effects on Human Body

Damage Nucleus

DNA

SLIDE 5

Lapse of Time after Exposure and Effects

Physical process Biochemical process Year Time One‐thousandth of a second after irradiation Clinical process

Mutation Cell death or cell degeneration Stochastic effects Cancer Hereditary effects Deterministic effects Acute radiation syndromes Fetal effects Cataract

Biological process

Mechanism of Causing Effects on Human Body

SLIDE 6

Deterministic Effects

No effects

Permanent damage

Loss of functions Morphological defects Temporary dysfunction ⇒ Recovery afterward There is the threshold dose for deterministic effects.

Damaged cells

Dead cells Normal cells

Repaired cells Amount of radiation

Mechanism of Causing Effects on Human Body

SLIDE 7

Radiosensitivity of Organs and Tissues

Hematopoietic system: Bone marrow and lymphatic tissues (spleen, thymus gland, lymph node) Reproductive system: Testis and ovary Gastrointestinal system: Mucous membrane and small‐intestinal villus Epidermis and eyes: Hair follicle, sweat gland, skin and lens Other: Lung, kidney, liver and thyroid gland Support system: Blood vessel, muscle and bone Transmission system: nerve Active cell division No cell division High sensitivity Low sensitivity

Mechanism of Causing Effects on Human Body

SLIDE 8

Stochastic Effects

Incidence of cancer

There is no threshold dose for stochastic effects (assumption).

Stochastic effects

Cancer and leukemia Hereditary effects Radiation Repair and elimination Proliferation Cancer cell Normal cells

Mechanism of Causing Effects on Human Body