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Physics 2 > Ch 15 & Tube/Target Interactions > Flashcards

Ch 15 & Tube/Target Interactions Flashcards

1
Q

What factors contribute to Compton scatter

A

KVp

Volume of irradiated material (part size)

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2
Q

What is occupational dose

A

Compton scatter

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3
Q

What does increased kVp do to pt interactions

A

Less photoelectric absorption
More scatter
Less dose

As long as it goes with decreased MAs

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4
Q

How does increased kVp effect image quality

A

Lower amount of contrast

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5
Q

What does decreased kVp do to pt interaction

A

More photoelectric absorption
More dose
Less scatter

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6
Q

How does decreased kVp effect Pt dose

A

Increased photoelectric absorption meaning Increased dose

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7
Q

Decreased kVp effect on image quality

A

Higher image contrast

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8
Q

Increased field size increases the volume of tissue irradiated, what also does this increase

A

Scatter

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9
Q

Decreased field size decrease beam quantity which also

A

Decreases scatter

Decreases amount of remnant radiation hitting the receptor

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10
Q

What is quantum mottle

A

IR does not receive the correct amount of exposure & causes a greying/grainy effect

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11
Q

What do you increase if you decrease the field size to maintain image quality

A

Mas

More photons make the image look less grainy

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12
Q

Is barium/contrast dense or not dense

A

Dense

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13
Q

Atomic number 74

A

Tungsten

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14
Q

Atomic number 56

A

Barium

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15
Q

Atomic number 20

A

Bone

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16
Q

What does beam restriction do for the pt and workers

A

Decrease scatter
Increase detail
Decrease dose
Decrease scale of contrast

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17
Q

What are the types of beam restrictors

A

Collimator
Aperture diaphragm
Cones
Cylinders

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18
Q

What’s the most common beam restrictor

A

Collimator

19
Q

How many sets of shutters do the Collimator have

A

Two

20
Q

What type of collimation does the Collimator allow

A

Rectilinear collimation

21
Q

What do the bottom shutters reduce

A

Penumbra

22
Q

What is penumbra

A

Geometric unsharpness

23
Q

What does the upper shutters reduce

A

Off focus radiation

24
Q

What is off focus radiation

A

Image shadows - ghosting

25
Q

What percent of accuracy does the light field need to be within

A

+/- 2% of SID

26
Q

What is PBL

A

Positive beam limitation

27
Q

What does PBL do

A

Automatically collimate the light field to the size of the IR - you can reduce the light field still but not increase it bigger than IR

28
Q

What does scatter create on the IR

A

Fog

29
Q

What does a grid do

A

Cleans up scatter - soft photons

30
Q

How are the shutters in the Collimator positioned

A

At right angles of each other. That shutter in opposing directions

31
Q

Example of Lead blocker

A

Shield

32
Q

When xray photons interact with matter and lose energy through those interactions, it is called

A

Attenuation

33
Q

Scattered photons that are deflected back towards the X-ray source is called

A

Back scatter

34
Q

What can coherent scatter also be called

A

Classical scatter
Thompson scatter
Unmodified scatter

35
Q

What is coherent scatter

A

Very low energy xray (10kev or lower) - non diagnostic

The atom is excited and releases energy by producing a secondary photon equal to the incident photon - just moving in a different direction.

36
Q

What is photoelectric absorption

A

Patient dose
Xray photon interacts with inner shell electron & ejects it, which gets absorbed by the pt. The atom is now ionized & a photoelectron is produced.

37
Q

What is Compton scattering

A

Occupational dose - AKA Compton effect
Incident photon interacts & removes a loosely bound outer electron, loses 1/3 its energy & proceeds in a new direction as a scattered photon. It can continue to interact with more matter or exit the body

38
Q

What is pair production

A

Does not occur in diagnostic xray
Very high energy photons (1.02 MeV or higher) gets close to the nucleus causing it to lose all of its energy. The result is production of a negatron & positron

39
Q

What is photo-disintegration

A

Does not occur in diagnostic xray
Extremely high energy photons (10 MeV or higher)
Photon strikes the nucleus & energy is absorbed, the nucleus gets excited & emits a nuclear particle

40
Q

Will increased kVp increase scatter or decrease scatter

A

Increase - more power behind the photons, the more chance it will act as a pin ball & go in all directions

41
Q

When will photoelectric absorption happen

A

When lower kVp is used
When contrast agents are used

42
Q

Low kVp does what to contrast

A

High contrast

43
Q

High kVp does what to contrast

A

Decreased contrast

Physics 2 (6 decks)

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