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Radiology I > Radiation Physics 2 > Flashcards

Radiation Physics 2 Flashcards

1
Q

What force maintains electrons and protons in the shells?

A

Electrostatic forces

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2
Q

What balances electrostatic forces?

A

Centrifugal forces of rotating electrons

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3
Q

What is the term for the energy used to remove an electron from its shell?

A

Electron binding energy

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4
Q

What shell is binding energy the greatest?

A

The K shell since it’s closest

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5
Q

What is ionization?

A

What happens when a neutral atom loses an electron

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6
Q

When does ionization happen and what electrons are usually lost?

A

When things are heated up or when high speed collisions with x-rays or particles are made. Usually outer shell electrons are lost

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7
Q

What is electromagnetic energy?

A

Movement of energy through space or matter as a combination of electric and magnetic fields

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8
Q

When is electromagnetic energy generated?

A

When the speed of an electrically charged particle is altered

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9
Q

What are the two processes by which x-rays are produced?

A

Bremsstrahlung and characteristic radiation

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10
Q

How is bremsstrahlung produced?

A

By the suddens stopping or slowing of an electron at the target

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11
Q

How does this slowing down occur?

A

The electron passes near the positive nucleus, giving up its energy as a photon

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12
Q

When is characteristic radiation produced?

A

When a high speed electron displaces an electron from the inner shell of the tungsten, causing ionization of the atom

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13
Q

Once the inner shell electron is removed, what happens?

A

An outer shell electron drops in to fill the void emitting a photon in the process

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14
Q

What determines the energy of the x-rays produced by a metal?

A

The atomic number, higher=more energy

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15
Q

What happens to the intensity of the beam when using a longer collimator?

A

It decreases

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16
Q

What are two ways we can compensate for a long collimator?

A

Increase the mA or the current, more electrons produced

Increase the exposure time, does not change intensity but more electrons overall

17
Q

What is attenuation?

A

The reduction in intensity of an x-ray beam as it travels through matter

18
Q

What 3 things affect attenuation?

A

Energy of initial beam
Thickness of absorber
Density of absorber

19
Q

After attenuation, the average energy of the beam is higher or lower?

A

Higher, low energy photons are attenuated or removed

20
Q

What is the name for the effect of low energy photons being removed?

A

Filtration that results in beam hardening

21
Q

What are the 3 kinds of interactions that attenuate the x-ray beam?

A

Coherent scattering, photoelectric absorption, and compton scattering

22
Q

Describe the process of coherent scatter

A

A photon passes near an outer shell electron, gives its energy to the electron and disappears

The electron moves up a shell, then falls back down releasing a photon at an angle

23
Q

What is a downside to coherent scatter?

A

The photon going off at an angle distorts the image slightly

24
Q

Describe compton scattering

A

A photon collides with an outer shell electron, loses some energy, and get deflected. The photon loses energy and the electron gains it

25
Q

What types of tissues will cause photoelectric absorption?

A

Hard or calcified tissues, causes radiopacities

26
Q

What is the SI unit for radiation?

A

KERMA, kinetic energy released in matter

27
Q

The KERMA is expressed in units of?

A

Gray or gy, 1 gy is 1 joule/kg

28
Q

What else is measured in grays

A

The absorbed dose

29
Q

How is the equivalent dose measured? What is it used for?

A

Sieverts, used to compare biological effects of different types of radiation on given tissue or organ

30
Q

What is the effective dose used to measure? Unit of measure?

A

The risk to humans, sieverts

31
Q

When the beam exits a specimen it forms a ?

A

Data set

32
Q

Aluminum filtration is used to remove what types of photons?

A

Soft, low energy, long wavelength leaving the hard high energy short wavelength

33
Q

What is fluorescence?

A

Instantaneous transmission of visible light upon application of a stimulus, used in extra oral radiology

Radiology I (9 decks)

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