Radiobiology Flashcards

1
Q

What is a direct effect caused by?

A

Caused by photon having a ‘direct hit’ on cell structures/chromosomes

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2
Q

What is indirect effect caused by?

A

Ionization of water in a cell leads to a free radical
H2O → photon = HOH+• + e-
Free radical causes damage

Sometimes it recombines and doesn’t cause issues.

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3
Q

What is radiolysis?

A

Radiolysis is the dissociation of molecules by ionizing radiation.
It is linked to both direct and indirect effects.

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4
Q

What can be caused by direct effect?

A
Genetic damage- offspring
Cell mutation - cancer
Overexpress chemicals - hormones
Delayed or arrested cell division - mitosis and meiosis
Cell death - apoptosis
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5
Q

What can be caused by indirect effect?

A

Ionisation of water leads to a free radical
A radical is a molecule with an unpaired electron (•)
-unstable & reactive

For example, OH • Radicals can combine to form hydrogen peroxide (H2O2). This has a relative long life and is an oxidiser which causes damage to cellular molecules.

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6
Q

Factors that effect tissues

A

Radiosensitivity of the tissue
Volume of tissue irradiated
Dose received

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7
Q

What are the types of BIOLOGICAL EFFECTS?

A

Somatic- individual

Genetic- offspring

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8
Q

Types of somatc effects

A

Acute or early effects - occur within hours or weeks. Alopecia

Late or chronic effects - chromosomal damage. May take up to 20 years
e.g cancer, fibrosis, permanent hair loss, mental retardation in children.

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9
Q

What causes of genetic effects and example

A

Irradiation of gonads (sperm and ova)
Passed onto offspring
Potentially harmful only if dose received before or during reproductive period.

Leukaemia
Mental retardation
Birth defects

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10
Q

Radiation effects can also be divided into:-

A

Deterministic effects (now also termed Harmful Tissue Reaction)

Stochastic effect

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11
Q

Factors of deterministic effects with example

A
Occur once a theshold dose received
Severity increases with dose
Most common-
Cataract - 1Gy
Male – >500cGy Permanent sterility
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12
Q

Factors of stochastic effects

A

Effect that have no threshold

Effects occur by pure chance- statistical

Frequency (incidence) increases with dose
Usually cancer

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