Lecture 2 Flashcards

1
Q

charged particle interactions- which cells do more

A

heavier particles behave differently in these, where alpha particles and protons are charged particles and heavy. The lighter ones like electrons and stuff do not behave as differently

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2
Q

3 ways to deposit energy (giving up energy)

A

excitation, ionization, radioactive losses

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3
Q

what is excitation

A

incoming particle excites the target atom by shifting an orbital electron and moves one to increased energy state (draws away from the nucelus) and boosts to outermost shell and so it gives off EM radiation since closer is in lower energy and outer is in higher energy

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4
Q

what is ionization

A

remove orbital electron (greater than binding energy of orbital electron) and the ejected electron fives off a delta ray, which can go on to interact with additional atoms

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5
Q

what is a delta ray

A

the secondary electron produced by ionization, which is a way to deposit energy

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6
Q

how much energy do delta waves deposit from energetic electrons in soft tissue

A

70%

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7
Q

At 40 eV electrons, what is the relationship between ionization and excitation

A

they should be equal

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8
Q

how many secondary electrons are produced from a 10 kEV electron

A

450 secondary with energy between 10 and 70 KeV

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9
Q

what is the energy that below which, electrons can no longer produce ionization

A

11.2 eV

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10
Q

what is Brensstahlung radiation

A

charged particle comes close enough to nucleus so it is slowed down by nucleus and it is shifted.

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11
Q

what is annihilation

A

positron combines with an electron, which produces two gamma rays equal to the mass energy of a positron and electron. at 511 keV each, and they go in opposite directions.

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12
Q

what type of imaging modality uses annihilation

A

PET imaging

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13
Q

what is specific ionization and how is it used

A

it is energy happening for a long time with photons, but with protons, they deposit at one depth which is called the Bragg peak. This is dose dependent, so it dumps its energy at one depth. It is used in proton beam therapy to target specific tissues without affecting others.

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14
Q

neutron interactions

A

cannot excite or ionize. They interact with the nucleus sometimes and release a charged particle.

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15
Q

what do neutrons interact best with

A

they interact best with light nuclei in H,CO,

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16
Q

what happens when a neutron hits a nucelus

A

recoil of the nucleus so that it loses energy via excitation or ionization then the neutron is captured and turns an H1 usually into an H2

17
Q

What are the Xray (photon) interactions

A

Daylight scatter, Compton scatter, photoelectric effect

18
Q

what is daylight scatter and what is it also called

A

classical or coherent scatter; Xray is emitted with the same energy but in a different direction.

19
Q

does the energy and deflection change with Rayleigh scatter

A

shallow deflection energy and there is no net change in energy. It tends to come into play with low energy. There is no ionization and no absorbed dose

20
Q

why is rayleigh scatter important in imaging

A

it comes up in imaging degradation