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POD EXAM 1 > XRAY PHYSICS > Flashcards

XRAY PHYSICS Flashcards

1
Q

Roentgen/ Air kerma

A

quantity of exposure (Roentgen kerma think bad karma on russian spy so theyre gonna be exposued to a high amount of xray)

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2
Q

Rad/ Gray

A

Quantity of exposed xray that is actually absorbed

10-20Gy is lethan to us

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3
Q

Rem (r)/ Sievert (Sv)

A

the effective biological damage that the abs radiation has caused (not all xrays are equally lethal) 2 Sv is lethal dose to humans

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4
Q

Curie/ Becquerel

A

quantity of radioactivity

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5
Q

exposure

A

amount of ionization that is produced when radiation passes through the body

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6
Q

Absorbed dose

A

amount of ENERGY abs by body when radiation passes through it

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7
Q

Dose equivalent

A

bio damage caused by radiation

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8
Q

Effective dose equivalent

A

measures biodamage to a specific organ

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9
Q

how much does.. rad=gY=cGy=mGy?

A

1 rad= .01 Gy=1cGy=10mGy

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10
Q

how much does rem=Sv=cSv=mSv?

A

1rem=.01Sv=1cSv=10mSv

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11
Q

Attenuation

A

the idea that some tissue abs more xrays than other tissues which leads to diff shades of gray on film

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12
Q

radiopaque

A

tissues that ABS xrays and appear white

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13
Q

Radiolucent

A

tissue that allows for complete penetration of xray and will appear black

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14
Q

Inverse square law

A

“the farther away youre from an energy source the less youll be exposed to it”, light intensity from a source is inversely proportional to the square distance between the object and the source

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15
Q

kVp

A
  • energy of the xray beam
  • normal: 50-70 kVps
  • manpulates energy/QUALITY of xray and a little bit of quantity too
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16
Q

mA

A
  • controls NUBMER of photons produced
  • normal: 10-30mAs
  • affects quantity/AMOUNT of xray
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17
Q

Timer

A
  • controls length of exposure
  • normal: 1/60-1/100 of a second
  • manipulate quantity (amount) of xray
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18
Q

what is the minimal Source to Image distance? (SID)

A

12 in from patient

-alters number of photons stirking the film

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19
Q

cathode

A
  • negative electrode of xray tube
  • has:
    - Filament (makes electrons when heated (mA))
    - focusing cup (directs filament electrons to the anode)
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20
Q

Anode

A
  • positive electrode
  • Target: e- produced by cathode are directed and made of tungsten and make xrays
  • focal spot: area on target from which xrays are emitted
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21
Q

Filtration

A

you add filtration so that beam comes out and is abs and wont reach the xxray plane

  • inherent:abs off focus radtion that doesnt contrbute to producing a good image
  • added: filters the useful xray beam and abs low energy xrays that cant reach the image
22
Q

Characteristic radiation

A
  • e interacts w/ atom’s inner shell e and removes the e which causes ionization
  • xray photons produced as outer shell e fill inner shells
23
Q

Bremsstrahlung radiation

A
  • E slows down/ brakes as it passes by post charged nucleus

- changes course of E which causes it to lose E in the form of xray photons

24
Q

what happens when you increase mA?

A

-inc QUANTITY only

25
Q

What happens when you increase kVP?

A

-mainly increases quality and little bit of quantity

26
Q

how does filtration affect xray quantity/ quality?

A
  • dec quantity

- inc quality

27
Q

Line focus principle

A

-allows a large area for heating while maintaining a small focal spot size (stationary anode)

28
Q

actual focal spot vs effective

A
  • actual: location on tungsten target where e- are directed FROM the cathode and is tilted so that the xrays strike a larger area which spreads out heat (increase of incident beam increases actual foca spot)
  • effective: seen by the image receptor, is smaller than actual focal spot
29
Q

Heel effect

A

-xray beam has a greater intensity at cathode side and thus you must position thicker portion of body closer to cathode

30
Q

which process produces xrays?

A

Bremsstralung radiation

31
Q

Coherent scattering

A

-as xray photons excite target atom a secondary photon of equal energy is released in diff direction and will be abs by patient and will not contribute to the image

32
Q

Compton scattering

A
  • when xray photo interact with matter and egects an OUTER shell e- -> ionization
  • causes xray to continue in diff direction with dec E
  • creates a “fog” and affects image quality (dec contrast)
33
Q

photoelectric effect

A
  • Xray photon is abs and an INNER shell e- is ejected during ionization
  • causes mean attenuation and image formation
  • contributes to patient’s abs dose
34
Q

finish this statement… “diagnostic image is formed by the ? and ?”

A

photoelectric effect and remnant radiation

35
Q

finish this statement “most xrays interact w/ matter via ? scattering which casues image?”

A

compton, fog

36
Q

how does low kVP affect image (not quality)?

A

favors photoelectric effect, increases dose of radiation and more radiation is abs by the body

37
Q

How does high kVP affect image (not quality) ?

A
  • favors Cmopton scattering

- more ratiation makes its way to the xray film because less is abs by bodY)

38
Q

Opical density

A

-amount of darkening in a radiograph

-

39
Q

mAs

A

-the primary controlling factor of an image
-mAxseconds
-inc mAs -> darker image
inc mAs by factor of 2
dec mAs by factor of 1/2

40
Q

law of reciprocity

A

-as mAs increase, xray quantity and radiograph density increases proportionally

41
Q

radiographic contrast

A

-difference in densities that allows for distinction between 2 adjacent densities in the same image

42
Q

Subject contrast

A
  • result of attenuation difference as xrays pass through body
  • affected by tissue thickness
43
Q

short contrast

A
  • used in food/ankle images
  • high contrast images that distinguishes bone from soft tissues
  • has few shades of gray
44
Q

long contrast

A
  • used in abdomen
  • diff between soft tissues
  • low contrast image and thus has higher shades of gray
45
Q

what is the primary factor in controlling contrast?

A
  • kVp

- high kVP -> low contrast

46
Q

how do you produce short contrast?

A

-increase mAs by 2x AND dec kVP by 15%

47
Q

how to you produce lengthened contrast?

A

dec mAs by 1/2 and increase kVP by 15%

48
Q

relationship between focal spot size and detail?

A

larger focal spot size –> decreased detail

49
Q

relationship between OID

A

-the greater the distance -> less detail/sharpness

50
Q

SID relationship

A

-greater the distance the sharper the image (but need to increase mAs too)

51
Q

how can you increase image definition/ spatial resolution?

A
  • small focal spot size
  • decreased OID
  • increased SID
  • slow film speed
52
Q

how does shape distortion happen?

A
  • central beam not perpendicular to film
  • foot plane not parallel to film
  • xray beam not centered over middle of foot
  • seen with medial oblique foot xray

POD EXAM 1 (9 decks)

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