X-Ray Emission (Test 1)

Quantity

What refers to the output from the tube, exposure to the patients, intensity of radiation, or amount of radiation?

- milligray in air (mGya)

- gray in air (Gya)

- milliroengten (mR)

- roengten (r)

What units is quantity measured in?

Directly proportional

What is the relationship between mAs and intensity?

mA

What is the controlling factor for the number of electrons available to travel across the X-ray tube?

Time

What is the controlling factor for the amount of time the electrons are allowed to travel across the tube?

mAs

mA x time = ?

Double the number of X-ray photons exiting the tube

Double the mAs = ?

Intensity stays the same

What does doubling the mA and halving the time do to the intensity?

They increase

As kVp increases, what happens to penetration and X-ray quantity?

15% rule

What rule states that a 15% increase in kVp will change the IR exposure/density by a factor of two?

- 2x ir exposure unless 1/2 mAs

- 1/2 ir exposure unless 2x mAs

- 15% kVp increase = ?

- 15% kvp decrease = ?

Decrease contrast (low contrast, long gray scale, many shades of gray)

What does a 15% kvp increase do to contrast?

Increase contrast (high contrast, short gray scale, few shades of gray)

What does a 15% kVp decrease do to contrast?

No

Does kVp have a physical effect in digital imaging?

Inverse Square Law

What states that intensity varies inversely with the square of the distance?

intensity 1 / intensity 2 = distance 2^2 / distance 1^2

What is the inverse square formula?

Square Law (Exposure Maintenance Law)

What refers to the amount needed to change technique when the distance changes?

It diverges and only the center part of the beam is used

As SID increases, what happens to the X-ray beam?

- 1/4 IR exposure unless 4x mAs

- 4x IR exposure unless 1/4 mAs

SID Rule Of Thumb

- 2x SID = ?

- 1/2 SID = ?

Intensity decreases

As filtration is added, the beam is "hardened" by absorbing low-energy photons, so what happens to intensity?

Decreasing the patient's skin dose (ESE)

What is the purpose of filtration?

Penetration (Quality / Energy)

What refers to the range or distance that the X-ray beam travels in matter?

Decrease wavelength and increase penetration

What does increased kVp do to wavelength and penetration?

Half Value Layer

What refers to the thickness of absorbing material necessary to reduce the x-ray intensity to 1/2 its original value?

Penetration increases

As filtration increases, what happens to penetration (quality/x-ray energy?

Inherent Filtration

What type of filtration is any material above the tube window that the radiation passes through?

.5 mm Al equivalent

What is the normal amount of inherent filtration in the X-ray tube?

Bronzing of the tube

Why does inherent filtration in the X-ray tube increase with age?

Added Filtration

What type of filtration refers to thin sheets of aluminum placed between the tube housing and the collimator?

1 to 2 mm Al

What is the normal amount of added filtration?

1 mm Al

What is the amount of added filtration in a collimator?

Copper and Aluminum

What are the two types of metal that a compound filter uses?

tube / patient

In a compound filter, copper is closer to the _________ and aluminum is closer to the _________

- .5 / 50

- 1.5 / 50 and 70

- 2.5 / 71

NRCP Total Filtration Limits

- ____ mm Al below ____ kVp

- ____ mm Al between ____ and ____ kVp

- ____ mm Al above _____ kVp

- Increase intensity

- Increase intensity / Increase energy

- Decrease intensity

- Decrease intensity / Increase energy

- Increase mAs = ?

- Increase kVp = ?

- Increase distance = ?

- Increase filtration = ?