RAD 354 Chapt 8 X-ray Production
• The primary purpose of an x-ray tube is to
accelerate electrons across the tube and
suddenly stop them in the target to produce
electromagnetic x-ray photons
– 99% of the electrical energy is dissipated as heat
– mAs DIRECTLY affects the AMOUNT of photons
produced
– kVp makes the PRODUCTION of x-rays “slightly”
more efficient
X-rays are made via two ways
• Brems
Characteristic
X-rays produced
• X-rays are emitted “isotropically” (in all
directions)
• The x-ray beam is “Polychromatic” (many
energies
• MAX energy is produced by min wavelength
– Duane-Hunt Law 12.4/kVp = min. wavelength
kVp effects
• kVp increase is equal to the “square of the
factor by which kVp is raised”
• kVp increases
– Results in increased energies at ALL levels
– The GREATER the increase, the GREATER the
energies
– Increases “skew” the x-ray emission spectrum to
the RIGHT
Filtration
• Inherent - .5mm al equiv. (will increase over
time as tungsten “boils off and coats” the
window
• Added – 2.0 al added for the 70-80 kVp level
• Total filtration is the SUM of inherent and
added
– INCREASES the average “hardness” of the beam
– Does NOT INCREASE any photon’s energy, only
raises the AVERAGE hardness
Target thoughts
• Increasing the atomic # of the rarget (anode)
will INCREASE the production of x-rays
• INCREASE in mAs = INCREASE in numbers of
PHOTONS
• INCREASE in kVp = INCREASE in QUALITY and
slight increase in production efficiency of xrays
Wave forms
• Half wave
• Full wave
• 3 phase
– 6 pulse
– 12 pulse
High frequency generators