1. Stacy Kopso, M.Ed., RT(R)(M)
X-ray Production
Stacy Kopso, M.Ed., RT(R)(M)

2. X-ray Production
When the exposure button is pressed, the projectile electron collide with the atom of the anode target and loose energy
X-rays are produced through two processes

3. Bremsstrahlung
Occurs when an incident electron interacts w/ the force field of the target’s(tungsten) atomic nucleus
Projectile electron undergoes three processes
Slows down
Changes direction
Loses some of its energy

4. An incident electron interacts w/ the force field of the target’s (tungsten) atomic nucleus and changes direction

5. Bremsstrahlung
The process results in the emission of a bremsstrahlung x-ray photon
85% of the xray beam consists of this interaction
1/3 of the kVp selected

6. Bremsstrahlung
The Brem photon energy is equal to the amount of energy lost by the projectile electron
Small amount of electron energy loss
Low energy photon- long wavelength
Large amount of electron energy loss
High energy photon- short wavelength
The greater the direction change, the greater the energy loss

7. Characteristic Radiation
Projectile electron interacts with the tungsten atom by ejecting an inner shell (K)electron and ionizing the atom
The K shell vacancy is filled by an outer shell electron
The process of filling the K-shell vacancy results in the emission of a characteristic xray photon

9. Characteristic Binding energies of shells K= 69 keV(kiloelectron volt)
L=12 keV
M=3keV
N=1keV
If an L shell fills the K shell the K-Characteristic photon has an energy range of 57keV (69-12)
If an M shell fills the K shell the K-Characteristic photon has an energy range of 66keV (69-3)

10. Characteristic
Energy of the x-ray photon is equal to the difference between the binding energies of the orbital shell (k shell and one that filled vacancy)
Depends on;
energy level of incoming electron
binding energy of electron that is knocked out
shell of orbital electron that drops into vacancy

11. Characteristic
Only K-shell (characteristic x-rays) are diagnostically useful
Characteristic x-rays produced from L-shell and farther from the nucleus, possess too little energy to be diagnostically useful(skin entrance dose or absorbed by filtration)

12. Class work

13. Beam Characteristics Beam Quality Beam Quantity Penetrating ability
Energy
kVp, filtration
Primary factor-kVp
Directly proportional to kVp
High quality=hard beam (high kVp)
Low quality=soft beam (low kVp)
Amount/number
Intensity
mAs, kVp, distance, filtration
Primary factor-mAs
Directly proportional to mAs
Squared for kVp
kVp doubled-intensity increases by factor of 4
Pt dose-expressed in Roentgen

14. Beam Quality Penetrating ability/energy
High quality=hard beam (high kVp)
Low quality=soft beam (low kVp)
Filtration
Removes the lower energy photons making the quality higher. Does not change the energy of the beam
Half value layer
Filtration is measured in half-value layer
Thickness of absorbing material (AL) necessary to reduce the energy of the beam to ½ its original intensity
The only technical factors that affect HVL are kVp and filtration

15. How many half value layers will it take to reduce an x-ray beam whose intensity is 78 R/min to an intensity of less than 10R/min???? 3

16. Beam Quantity Amount/Intensity/Number kVp 15% rule mAs
Direct although not proportional
Double the intensity, increase the kVp by just 15%
60 kVp to 69 kVp
mAs
Directly proportional
Double the intensity, double mAs
30mAs to 60 mAs

17. Beam Quantity Filtration Distance Increase filtration
Decrease quantity
Remove low energy photons
Distance
Increase distance=decrease in quantity
Inverse Square law

18. Inverse Square Law
Used to calculate a change in beam intensity with changes in SID
The intensity of the beam is inversely proportional to the square of the distance
Distance is ½ = 4x more intensity
Distance is doubled = 1/4 intensity
Formula
I 1 /I2 = (d2 /d1 )2

19. Inverse Square Law
An exposure taken at 40 inches yields an intensity of 200mR. What is the intensity if the distance is increased to 80inches?
I 1 /I2 = (d2 /d1 )2
50mR

20. Direct Square Law Density maintenance
Used to maintain radiographic density with changes in SID
mAs 1 / mAs 2 = (SID 1 / SID2)2
A satisfactory radiograph is produced using exposure factors of 75kVp and 10mAs at a distance of 40 inches. What new mAs would be required to produce a similar density if the distance is increased to 80 inches?
40mAs

21. Quality or Quantity???? Directly proportional to kVp
Directly proportional to mAs
Amount/number
Intensity
Penetrating ability
Energy
Primary factor mAs
Affected by kVp and filtration
Affected by mAs, kVp, distance and filtration

22. X-ray beam Primary beam Remnant beam
Useful radiation that consists of the xray photons directed through the xray tube window port
Incident photons
Remnant beam
The portion of the attenuated xray beam that emerges from the patient and interacts with image receptor
Exit radiation

23. Class work

24. Emission Spectrum
Graphically illustrates the x-ray beam so you can visually see the nature of the beam and the effects of different influencing factors on them

25. Emission Spectrum
The xray beam is the result of 2 different anode target interactions
Characteristic and Bremsstrahlung
Characteristic photons have a discrete emission spectrum
Brems have a continuous emission spectrum

26. Characteristic Discrete Emission Spectrum
Photons are named for the shell being filled
K,L,M etc
Bar represents each level according to their energy
Only K and L are labeled because they are the only shells with enough energy to have diagnostic value
Height of bar is the number of photons

27. Characteristic Discrete Emission Spectrum
Y-axis
X-axis
K characteristic photons have an energy ranges of 57keV to 69keV
L characteristic photons have an energy ranges of 9keV to 12kEv

28. Bremsstrahlung Continuous Emission Spectrum
Energy depends on strength of attraction to the nucleus
Energy range of 0 to the maximum kVp selected on the control panel
Most are 1/3 of the kVp selected
Bell shaped graph

29. Bremsstrahlung Continuous Emission Spectrum
1/3 of kVp
kVp selected
Y-axis
X-axis
Bell curve for tungsten target

30. Combine the Two X-ray Emission Spectrum

31. Emission Spectrum
Factors that change the appearance of the x-ray emission spectrum mA
kVp
Tube filtration
Generator type
Target material
Quantity
Vertical axis
Quality
Horizontal axis

32. Change in mAs Quantity changes
An increase in mAs will cause the amplitude of the curve to rise (proportional to the quantity of radiation)

33. Change in kVp Quality & Quantity changes
Increase in kVp will cause the amplitude to rise and the peak of the curve shift to the right

34. Added Filtration Quality & Quantity changes
An increase in filtration will cause the amplitude to decrease and shift the peak of the curve to the right

35. Change in generator Quantity & Quality change
As the efficiency of the generator type increases, so does the x-ray quantity & quality.

36. Class work