X-ray Production and Emission Spectrums

Factors Affecting Radiation Quantity

• The number of projectile electrons used for x-ray production affects radiation quantity.
• mA (milliamps) affects radiation quantity, average beam energy, and maximum photon energy.

Exposure and Units

• Exposure is measured in units of Roentgens (R) or Coulombs per kilogram (C/kg).

X-ray Emission Spectrum

• The amplitude of an X-ray emission spectrum indicates the intensity of the x-rays.
• The location of peak amplitude (‘hump’) in an X-ray emission spectrum indicates the most probable energy of the x-rays.
• The highest energy at the end of the continuous portion in an X-ray emission spectrum depends on the tube voltage (kVp).

X-ray Tube and Emission

• The equation to determine the total number of x-rays emitted from the x-ray tube is not provided.
• mA affects radiation quantity by changing the intensity or quantity of x-rays in the useful beam.

Intensity and Bushong

• Bushong uses intensity and flux interchangeably with intensity.

mA and Exposure

• Increasing mAs from 20mAs to 40mAs while keeping all other conditions the same will double the exposure.

Inverse Square Law

• According to the inverse square law, if the distance from the source is doubled, the intensity of the radiation will decrease by a factor of four.

Area Under the Curve

• The formula for calculating the area under the curve when the tube voltage is increased is not provided.
• If an initial exposure was made using 62 kVp and 10mAs, and the total area under the curve was 6.3 cm², the area under the curve would be higher if the tube voltage was raised to 70 kVp.
• kVp and the area under the curve are directly proportional.

Exposure and Distance

• If the exposure measured at 90 cm from the source was 400 mR, the exposure would be 100 mR if the object moved to 180 cm away from the source.
• The formula for the inverse square law is: I₁ / I₂ = (d₂ / d₁)².

mAs and SID

• If the initial mAs used was 5mAs and the SID was increased from 90 cm to 180 cm, the new mAs needed to maintain the X-ray intensity reaching the image receptor would be 20mAs.

kVp Effects

• Increased kVp shifts the distribution of emitted x-ray energy towards higher energies.
• Added filtration reduces the beam intensity.
• As kVp increases, the efficiency of Brems and Characteristic production also increases.