X-RAY PRODUCTION

Question 1

CONDITIONS NECESSARY TO PRODUCE X-RAYS:

Answer 1

• Large potential difference (kVp)
• Quantity of electron (mAs)
• A place of interaction (target)
• Source of electron (filament)

Question 2

FIVE X-RAY INTERACTION WITH MATTER

Answer 2

Coherent Scattering
Compton Scattering
Photoelectric Effect
Pair Production
Photodisintegration

Question 3

• J.J. Thompson
• Classical or Thompson scattering.
• Occurs at below 10 keV
• The incident x-ray interacts with a target atom, causing it to become excited.
• Results:
o No electron ejected (excitation only)
o Change in x-ray direction (scattered)
o No change in its energy (same wavelength and same frequency).
o Little importance to diagnostic radiology.
o Contributes slightly to image noise (if it reaches the IR).

Answer 3

COHERENT SCATTERING

Question 4

TWO TYPES OF COHERENT SCATTERING

Answer 4

Rayleigh scattering
Thompson Scattering

Question 5

 Involves all of the electrons of the atom in the interaction

Answer 5

Rayleigh scattering

Question 6

 Involves a single electron of the atom in the interaction

Answer 6

Thompson scattering

Question 7

• Arthur Holly Compton
• The high-energy (high kVp) incident x-ray interacts with the outer-shell (loosely bound) electron and ejects it from the atom.
• Ejected electron is also known as: Compton, secondary, recoil and inelastic e-.
• Results:
o An electron ejected (Compton e-).
o Change in x-ray direction (scattered).
o Reduction in energy (reduced frequency, and increased wavelength).

Answer 7

COMPTON SCATTERING

Question 8

• The low-energy (low kVp) incident x-ray interacts with the inner shell (tightly bound) electron.
• Ejected electron is called a photoelectron.

• Results:
o Incident x-ray disappears
o Total x-ray absorption.
o Production of characteristic x-rays.
o Ion pair: photoelectron (ejected e-) and positive atom (deficient of one e-).

Answer 8

PHOTOELECTRIC EFFECT

Question 9

• Occurs at 1.02 MeV
• The incident X-rays interact with the nuclear force field.
• Result:
o Incident x-ray disappears.
o Production of 2 electrons with opposite electrostatic charges (positron, antimatter, and an electron) both having an energy equivalence of 0.51 MeV.

Answer 9

PAIR PRODUCTION

Question 10

o Occur at 10 MeV
o The incident x-ray interacts directly with the nucleus.
o Results:
o X-ray is absorbed by the nucleus.
o A nucleon/nuclear fragment is emitted.
o Photodisintegration does not occur in diagnostic imaging.

Answer 10

PHOTODISINTEGRATION

Question 11

IMPORTANT X-RAY INTERACTIONS TO RADIOLOGY:

Answer 11

o Compton (30-150 keV)
o Photoelectric (30-150 keV)