2a - Radiographic Quality Flashcards

1
Q

mAs

A

milliamps x seconds (mAs)

  • Gives the quantity of x-ray
  • Responsible for the DENSITY (overall darkness) of an x-ray
    • Increasing mAs –> more dark x-ray
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2
Q

Relationship between mA and mAs

A

there is a direct relationship between mA and mAs

  • Doubling mA = doubling the mAs
    • 100 mA * 0.2 sec = 20 mAs
    • 200 mA * 0.2 sec = 40 mAs
  • Halving mA = Halving mAs
    • 100 mA * 0.2 sec = 20 mAs
    • 50 mA * 0.2 sec = 10 mAs
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3
Q

Relationship between time and mAs

A

there is a direct relationship between time and mAs

  • doubling time = doubling the mAs
    • 100 mA * 0.2 sec = 20 mAs
    • 100 mA * 0.4 sec = 40 mAs
  • Halving time = halving mAs
    • 100 mA * 0.2 sec = 20 mAs
    • 100 mA * 0.1 sec = 10 mAs
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4
Q

50% mAs reciprocal rule

A

double (or ½) mAs will double (or ½) FILM DENSITY

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5
Q

15% kVp rule

A

adding (or subtracting) 15% kVp, has the same effect as doubling (or halving) the mAs

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6
Q

Rule of 3

A
  • when going for 40” to 72” must use 3x mAs
  • when going for 72” to 40 must use 1/3 mAs
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7
Q

Rule of thumb for kVp

A

If you can see bone leave kVp alone

  • if bone is seen, but film is too light:double mAs
  • film is so light that bone cannot be seen: double mAs + increase kVp 15%
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8
Q

If SID changes, how does mAs change?

A
  • mAs must be adjusted to maintain DENSITY
  • use “Rule of 3”
    • when going for 40” to 72” must use 3x mAs
    • when going for 72” to 40 must use 1/3 mAs
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