Chapter 8 - X-Ray Production

What are the two types of X-rays that are formed in the X-ray making process?

Bremsstrahlung and characteristic

Most of the kinetic energy of electrons is converted into _____.

heat

Most of the heat generated at the target is due to…?

the excitation of outer-shell electrons

The production of heat in the anode increases directly/proportionally with increasing _______________.

x-ray tube current

True or False: The efficiency of X-ray production is dependent on the tube current.

False; the efficiency of X-ray production is not affected by the tube current

The increase of ____ increases X-ray production efficiency.

kVp

What type of X-rays can be formed when a projectile electron comes in proximity to the nucleus, slows down, and abruptly changes direction?

Bremsstrahlung X-rays

The maximum energy of a Bremsstrahlung photon that can be created during an X-ray exposure is equal to?

the energy of the incident electron

Bremsstrahlung is a German word that means?

braking or slowing

Below 70 kVp, what percentage of electrons in the X-ray beam are Bremsstrahlung interactions?

100%

Above 70 kVp, what percentage of electrons in the X-ray beam are Bremsstrahlung interactions?

about 85%

True or False: Every X-ray exposure will contain photons produced from Bremsstrahlung interactions.

True

True or False: The greatest number of X-rays is emitted with energy approximately one-third of the maximum energy.

True

What type of X-rays can be formed when a projectile electron interacts with an inner-shell electron?

characteristic X-rays

True or False: Only the K-shell characteristic X-rays of tungsten are useful for imaging.

True

Below 70 kVp, what percentage of electrons in the X-ray beam are characteristic interactions?

none (0%)

Above 70 kVp, what percentage of electrons in the X-ray beam are characteristic interactions?

about 15%

How is the energy of a characteristic photon calculated?

as the difference between the binding energies of the two orbital electrons involved

True or False: In characteristic radiation, both the incoming electron and the K-shell electron are removed. The X-rays are created when other electrons from outer orbits fill in the K-shell vacancy and release binding energy (cascade effect).

True

What does the term "binding energy" refer to?

energy required to remove an electron from orbit

True or False: In terms of producing X-ray images, Bremsstrahlung photons are more desirable than characteristic photons because they are more efficient in imaging.

False; there is no difference between a bremsstrahlung and a characteristic photon in terms of producing X-ray imaging, they are simply produced by different interactions

True or False: Bremsstrahlung radiation involves deceleration of the electron, while characteristic radiation involves the absorption of an inner-shell electron.

True

What is the X-ray emission spectrum?

a graphical representation of the intensity of X-ray photons as a function of their energy

What does the y-axis (amplitude) on the X-ray emission spectrum represent?

the number of X-rays (intensity)

What does the x-axis (shape) on the X-ray emission spectrum represent?

the X-ray energy

What are the 5 factors affecting the X-ray emission spectrum?

the effect of:

1. mA & mAs

2. kVp

3. added filtration

4. target material

5. voltage waveform

True or False: mA controls the X-ray beam quality.

False; mA controls beam intensity.

True or False: Increasing the mA will increase receptor exposure and patient dose.

True

True or False: kVp controls the energy of the X-ray beam.

True

True or False: Increasing kVp does not change the efficiency of X-ray production.

False; increasing kVp makes X-ray production more efficient

True or False: Higher kVp can increase the quantity/intensity of the beam.

True

An increase in current (mAs) results in a(n) _________ in intensity, and _________ in energy.

increase, no change

An increase in voltage (kVp) results in a(n) ________ in intensity, and ________ in energy.

increase, increase

An increase in added filtration results in a(n) _________ in intensity, and ________ in energy.

decrease, increase

An increase in target atomic number (z) results in a(n) ________ in intensity, and ________ in energy and characteristic radiation.

increase, increase

An increase in voltage ripple results in a(n) ________ in intensity, and ________ in energy.

decrease, decrease

What does mA affect in the X-ray emission spectrum?

amplitude only

What does kVp affect in the X-ray emission spectrum?

both amplitude and shape

What does added filtration affect in the X-ray emission spectrum?

both amplitude and shape

What does target material affect in the X-ray emission spectrum?

both amplitude and shape significantly

What does the voltage waveform affect in the X-ray emission spectrum?

both amplitude and shape significantly

What is the 15% rule in radiography?

it is a useful approximation to adjust the mAs when changes to the kVp are desired in the X-ray protocol

What should you do to mA after increasing kVp by 15%?

halve the mA

What should you do to mA after decreasing kVp by 15%?

double it

What is the minimum kVp 4% change rule?

a rule that is used when you want to make a slight tweak to exposure without doubling or halving it (like the 15% rule)

True or False: Higher kVp = lower contrast (more gray)

True

True or False: Lower kVp = higher contrast (more black and white)

True