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Oral Radiology > Lecture 1 - Radiation > Flashcards

Lecture 1 - Radiation Flashcards

1
Q

Radioactivity describes what?

A

The decay rate of a radioactive material.

*Measured in Becquerels

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2
Q

What is exposure?

A

Measure of radioactive kinetic energy emitted from a source and is quantified generally by its capacity to ionize air. It’s a measure of the intensity of the radiation field.

*Measured in units of charge/mass - Coulombs/Kilogram (C/Kg)

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3
Q

What is the absorbed dose?

A

Energy absorbed by any type of matter, and is derived by calculating the imparted energy divided by the mass absorbing it.

*Measured in Gray (Gy)

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4
Q

What is the equivalent dose?

A

It is used to compare the biological effect on a tissue from diff types of radiation.

*Particulate radiation has high LET (linear energy transfer) than photons, and thus a greater biological effect. [Larger marbles have more mass and can potentially transfer more energy in a collision

**Measured in Sieverts (Sv)

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5
Q

What is the effective dose?

A

It is used to measure the estimated risk to humans.

*Takes into account the type of radiation (equivalent dose) and the nature of each organ or tissue being irradiated, so sums it up to get a whole body effective dose

**Measured in Sievert (Sv)

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6
Q

More ________ dividing, ______ differentiated cells are most susceptible and thus are more heavily weighted in calculating effective dose.

A

Rapidly

Less

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7
Q

What is the absorbed dose?

What is the equivalent dose?

What is the effective dose?

A
  • Energy deposited in a kg of a substance by the radiation
  • Absorbed dose weighted for harmful effects of different radiations
  • Equivalent dose weighted for susceptibility to harm of different tissues (More sensitive the tissue is, the higher the effective dose)
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8
Q

What is radiobiology?

A

The study of the effects of ionizing radiation on living systems

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9
Q

What is a direct effect?

A

When a photon or secondary e- ionizes biological macromolecules

THIS ACCOUNTS FOR 1/3 OF BIOLOGIC DAMAGE FROM X-RAYS

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10
Q

T/F - Altered molecules differ structurally and functionally from originals, so this results in a biological change.

A

TRUE

*Can lead to cell death, mutation, or carcinogenesis

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11
Q

What is the radiolysis of water?

A

Photon absorbed by water in an organism, ionizing water molecules into free radicals

*photon + H2O = Hdot + OHdot

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12
Q

T/F - Ionization of H2O leads to free radical production.

A

TRUE

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13
Q

What is the indirect effect?

A

Free radicals and toxins produced thru the intermediate step of water radiolysis then interact with biological macromolecules to cause changes.

THIS ACCOUNTS FOR 2/3 OF BIOLOGICAL DAMAGE FROM X-RAYS

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14
Q

T/F - Organic free radicals are unstable and transform quickly to stable altered molecules

A

TRUE

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15
Q

What is the primary cause of radiation induced cell death?

A

Damage to DNA

Can result from:

Breakage of one or both DNA strands

Cross linking of DNA strands w/in helix to other DNA strands

Change or loss of base

Disruption of H-H bonds b/t DNA strands

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16
Q

What is the deterministic effect?

A

Radiation injury dependent on the dose
-The greater the dose, the greater the injury severity

High level of exposure is req’d to produce a clinically observable effect

There is an exposure threshold below which the effect does not occur or is clinically observable

Typically these effects are tissue related

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17
Q

What are 4 modifying factors of deterministic effects on tissues and organs?

A

Dose - above threshold level

Dose rate - High rate produces more damage

O2 - Damage increases as oxygen level rises

LET - Increase LET (Linear energy transfer) produces greater damage

18
Q

T/F - Less differentiated tissues are more sensitive to radiation.

A

True

*Stem cells are highly sensitive to radiation

19
Q

What is the stochastic effect?

A

This is the one that we really worry about with taking radiographs

Radiation injury is based on the probability of occurrence

Probability of the effect occurring increases with dose

There is no threshold level, and there is not level of exposure at which there is zero risk

Examples: Radiation induced cancer and genetic alterations from sub lethal damage to DNA

20
Q

What are the 3 guiding principles of radiation safety?

A

Justification - We have the obligation to do more good than harm

ALARA - As low as reasonably achievable

Dose limitation - There are no dose limits in diagnostic and therapeutic radiology, so we need to adhere to good radiation safety practices and have a good radiation protection program in place

21
Q

What is radiation?

A

Transmission of energy through space and matter

*Can be ionizing or nonionizing depending on the amount of energy in the radiation

EX: Heat, light, sound, radio, microwaves

22
Q

Higher frequency = __________ energy

A

MORE

23
Q

Where is the line b/t non-ionizing radiation and ionizing radiation?

A

B/t visible light and UV radiation. Visible light and lower is non, while UV and higher (X-rays and gamma rays) are ionizing

24
Q

What is ionizing radiation?

A

Radiation with sufficient energy to displace atomic electrons, and that breaks bonds that hold a molecule together

*Can lead to cell death and/or molecular alteration leading to harmful effects

25
Q

We get 50% of our radiation from where/what? What about the other 50%?

A

Natural - Mostly from radon 37%

Manmade - CT scans 24%

26
Q

What is particulate radiation?

A

Alpha and beta particles and neutrons

27
Q

What is electromagnetic radiation?

A

Photons

EX: Gamma and X rays

28
Q

Exposure is measured in what?

A

Coulomb/kilogram

29
Q

Absorbed dose (imparted energy/mass) is measured in what?

A

Gray

30
Q

Equivalent dose is measured in what?

A

Sievert

31
Q

Effective does is measured in what?

A

Sievert

32
Q

Radioactivity is measured in what?

A

Becquerel

33
Q

What is radiation?

A

Transmission of energy thru space and matter

34
Q

What is ionizing radiation?

A

Radiation with sufficient energy to displace atomic electrons, thus breaking bonds that hold a molecule together

35
Q

Our sources of radiation come from two main things. What are they?

A

Natural

Man-made

36
Q

Tell me the following forms of natural radiation listed from greatest to least.

A

RADON - 37%

COSMIC - 5%

INTERNAL - 5%

TERRESTRIAL - 3%

37
Q

Tell me the sources of man-made radiation from greatest to least.

A

CT Scans - 24%

Medical x-rays - 12%

Nuclear medicine - 12%

Consumer products - 2%

Other - ~1%, Occupational, fallout, nuclear fuel cycle, misc

38
Q

Particulate radiation has three things. Name them.

A

Alpha particles

Beta particles

Neutrons

39
Q

Electromagnetic radiation (photons) have 2 things. Name them.

A

Gamma rays

X rays

40
Q

SI Units

Exposure?

Absorbed dose?

Equivalent dose?

Effective dose?

Radioactivity?

A

Exposure - Coulomb/kilogram (C/kg)

Absorbed - Gray

Equivalent dose - Sievert (Sv)

Effective dose - Sievert (Sv)

Radioactivity - Becquerel (Bq)

Oral Radiology (7 decks)

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