Chapter 3 Interactions with X-Ray production and matter Flashcards
What are some characteristics of X-ray?
invisible, travels in waves, no mass, no charge
What are the three tissue interactions?
absorption/attenuated, scattered, pass through without interacting
What is Absorbed Dose?
amount of energy absorbed per unit mass
What is attenuation?
reduction in number of primary photons due to absorption and scatter as beam passes through the patient
What is direct transmission?
photons with no interaction
What is indirect transmission?
photons that interact with the patient, scattered or deflected with loss of energy
What is an exit photon?
image formation photon/photons that strike the IR and have no interaction with the patient
What is small angle scatter?
photon with a small degree of bending of its path/reached IR and degrades image covering up visibility of detail or radiographic fog
What are attenuated photons?
interacted with biological tissue and have been scattered or absorbed
What are the five different photon interactions?
Coherent Scatter
Photoelectric absorption
Compton Scatter
Pair Production
Photodisintegration
What two photon interactions are most important in x-ray?
Photoelectric absorption and Compton scatter
What are other names for coherent scatter?
classical elastic or unmodified scattering
Define Coherent Scatter
low energy photon (less than 10 keV), transfers its energy by causing all or some electrons of the atom to vibrate momentarily
Define Photoelectric Absorption
responsible for patient dose and contrast in images (23-150kVp), photon interaction with an inner shell electron K or L shell tightly bound electron is ejected and fill an open shell in a close atom
Define Characteristic Photon
most common type, when an orbital electron of target atoms are removed from their shell and outer shell electrons fill inner shell vacancies, also called fluorescent radiation
What is the Auger effect?
instead of characteristic photons, energy is liberated when this vacancy is filled transferred to another electron of atom ejecting it
What is the atomic number of bone, calcium and soft tissue?
Bone 13.8
Calcium 20
Soft Tissue 7.4
What effect does Positive contrast have?
leads to an increase in absorbed dose in body structures
What are other names for Compton Scatter?
incoherent inelastic or modified scattering
What is Compton Scatter?
responsible for technologist dose, interacts with outer shell electron knocks outer shell electron out called a recoil electron
What is Pair Production?
energy of incident photon is at least 1.022 MeV, photon interacts with nucleus energy transformed into two particles ejecting a positron and negation, used in PET
What is Photodisintegration
energies exceeding 10 MeV, used in high energy radiation therapy treatment
