The effect of ionizing radiation Flashcards
Define radiation
The energy travels across the electromagnetic spectrum in the form of waves or particles. It can be ionizing or non-ionizing
What are the examples of ionizing waves?
*X-ray
*UV
*gamma-ray
(They damage dna )
What are the examples of non-ionizing rays?
- Extremely low frequency (non-thermal)
- Radio(Thermal )
- Microwave (thermal)
- Infrared(Thermal)
What is the difference between ionizing radiation and non-ionizing radiation?
> IR: Causes formation of ions when interacting with matter resulting from the release of an electron. Production of ions requires the energy of short wavelengths and high frequency.
NIF: It is characterized by long wavelength and low frequency and produces vibration and rotation of atoms in biological molecules
What are the units of measurement for Radiation?
*Essentially refers to :
>amount of radiation emitted, radiation dose absorbed, and biological effects of radiation
> Current unit of absorbed dose is the gray (Gy) = 100 rads (previously used )
What is the mechanism of action of radiation
> High frequency and short wavelength
*Capable of deep tissue penetration with moderate ionization of particles along the path. Indirect injury by production of free radicles; and interact with cellular components
> Subatomic particles
*Limited depth penetration but densely ionize structure in their path
> Direct injury
- DNA damage resulting in delayed effects including mutations, chromosomal abnormalities, genetic stability, and later malignancy
- Damage to genetic apparatus of nucleus due to damage of DNA
- chromosomal abnormalities play a role in inducing malignant transformation esp genes involved in repair, cell cycle, and cell arrest
> High doses of radiation
- acute cell death due to membrane or cytoplasmic structural damage
- delayed organ dysfunction; a combination of atrophy of parenchymal cells, ischemia due to vascular damage, and fibrosis
> Cells in G2 and mitotic phases of the cell cycle are most sensitive to ionizing radiation
> Dose rate
*A single dose can cause more injury than divided doses which allow time for tissue repair. A single dose of external radiation to the whole body is more lethal than regional doses with sheilding
Rapidly dividing cells are more radiosensitive than quiescent cells
Haemopoetic cells ,germ cells ,GIT epithelium = highly sensitive
Bone ,cartilage ,muscle and nerve =more radiosensitive
> Ionising radiation produce oxygen-derived free radicles which enhance cell death and increase radiosensitivity
Effects of radiation on cells
6 marks
- Nuclear swelling and clumping of chromatin
- Nuclear pleomorphism
- Gaint cell transformation
- Cytoplasmic swelling
- increased mitotic rate
- Vascular change
Effects of radiation on tissue
Necrosis, atrophy, and fibrosis of organs supplied by damaged blood vessels
Effects of radiation on blood vessels
> Early changes
- Dilation(erythema )
- Endothelial swelling and damage
- Fibrinoid necrosis of small vessel wall
> Later changes
- Telangiectasia
- Endothelial proliferation with hyaline thickening of walls
- Luminal marrowing and obliteration
Effects of radiation on the heart
Fibrosis of the pericardium resulting in constrictive pericarditis
*less commonly, the radiation includes injury to capillary and coronary arteries result in myocardial ischemia and fibrosis
Effects of on skin AKA radiation dermatitis
- Areas like axilla and groin are most susceptible
- Mild post-radiation erythema
- desquamation
- edema
- blisters
> chronic radiation dermatitis
*changes in pigmentation (Increase /decrease ) , hyperkeratosis ,skin atrophy ,dermal and subcutaneous fibrosis and telangietasia
Skin tumor may occur many years after exposure eg basal cell carcinoma , squamous cell carcinoma
Effects of radiation on bone marrow
- Bone marrow and lymphoid tissues are very susceptible to radiation
- A lymphopenia develops within hours of high dose exposure
- Provided death does not supervene from overwhelming infection or hemorrhage radiation effects on blood is reversiable
Effects of radiation on the lung
- Vulnerable due to blood supply
- Acute changes mimic diffuse alveolar damage
- later,intra-alveolar and interstitial fibrosis
Effects of radiation on the gastrointestinal tract
- Radiosensitive due to high turnover of mucosal lining
- Loss of protective absorptive layer resulting in vomiting ,sever diarrheas’ and risk of infection
Later result in atrophy and fibrosis > stricture > bowel
obstruction
Effects of radiation on gonads
- Very sensitive
- Sterility can follow even low doses of radiation to ovaries/testes
- Minor heritable changes to germline > fetal abnormalities
