Photon-Tissue Interactions Flashcards
Most common photon-tissue interaction in diagnostic imaging
Photoelectric and Compton interactions
Explain photoelectric interaction
Incoming x-ray photon hits K-shell electron, energy is transferred to electron which is ejected from K shell. Photon is absorbed. Hole in K shell is filled by electrons from outer shell.
What is an ejected k-shell electron called?
Photoelectron
Photoelectron interaction produces what in a radiograph
Contrast because of the differential absorptions of incoming x-ray photons in the tissues
Photoelectric interaction results in what to the patient?
Increased dose
Compton interaction is also called what?
Compton scattering; modified scattering
Explain Compton interaction
Incoming x-ray photon strikes a loosely bound, outer-shell electron, photon transfers part of its energy, electron is removed from orbit as scatter, photon scatters in another direction
Scattered photons may interact with other electrons which causes what?
More ionization, additional scattering, photoelectric absorption, or may exit the patient.
Coherent scatter is also known as what?
Classic; Thompson’s scatter
Explain Coherent Scatter
electrons are not removed but vibrate, this emits energy which travels in a path slightly different from the original path. No ionization occurs.
Effect of coherent scatter
Fog may occur when kVp is greater that 70
Coherent scatter is produced by what?
Low energy x-ray photons
Explain pair production
Interaction between the incoming photon and the atomic nucleus, produced at photon energies greater than 1.02 million electron volts
Which photon-tissue interactions do not occur in diagnostic radiography
Pair Production and Photodisintergration
Name the 5 different types of photon-tissue interactions
Photoelectric, Compton, Coherent, Pair Production, Photodisintergration
