week 6: tissue interactions Flashcards
differential absorption: a process whereby some of the x-ray beam is ___________ and some _____________ anatomic part
absorbed in the tissue; passes through (transmits)
beam name as it leaves the x-ray tube
primary radiation
beam name as it leaves the patient
remnant radiation (also known as exit radiation)
what is exit radiation composed of?
transmitted and scattered radiation
what is exit radiation?
when the attenuated x-ray beam leaves the patient
When an x-ray photon enters into biological tissue what three basic “things” can happen?
- the photons pass through the body unaffected
- absorption of photons occurs
- change of direction of photons
the reduction in the intensity or number of photons in the primary x-ray beam
attenuation
why does attenuation occur?
it is a result of the photon interaction with the atomic structures that comprise the tissues
what are the two processes the occur during beam attenuation?
absorption and scattering
What does it mean for an x-ray photon to pass through biological tissue (transmission)?
most common “interaction”
Here, the photon does not interact with tissue and photon has no loss of intensity
What are the five interaction in matter?
- Coherent
- Photoelectric
- Compton
- Pair production
- Photodisintegration
which interaction is the one is below diagnostic range?
Coherent scattering
which interaction is at the diagnostic range?
photoelectric, compton
which interaction is above the diagnostic range?
pair production, photodisintegration
what is to note regarding the probability of a photoelectric interaction?
probability concerns (1) energy of incoming x-ray photon (kVp) and (2) atomic number of anatomic tissue)
what is to note regarding the probability of a Compton scattering?
probability is kVp dependent only
Compton scattering interacts with which type of electron shell: inner or outer?
outer
Photoelectric interactions interacts with which type of electron shell: inner or outer?
inner
what are the 4 factors that affect beam attenuation?
- Tissue thickness
- Type of Tissue
- X-ray beam quality
- Transmission
what contributes to patient dose?
the photoelectric effect
what contributes to occupational dose?
Compton scattering radiation
how is beam attenuation impacted by an increase/decrease in tissue thickness?
increase in tissue thickness = increase attenuation
decrease: decrease attenuation
how is beam attenuation impacted by an increase/decrease in types of tissue?
increase in tissue atomic number/tissue density = attenuation increase
decrease: attenuation decrease
how is beam attenuation impacted by an increase/decrease in x-ray beam quality?
increase in x-ray beam quality = less attenuation
decrease: increase attenuation
exit radiation interacts with an IR to create a non-visible image which is a ____________
latent image
processed latent image, now a visible image is a _______
manifest image
block radiation rather than allowing it to pass through
radiopaque
allows radiation to pass through
radiolucent
radiopaque vs. radiolucent: which is bright/which is dark?
radiopaque = bright
radiolucent = dark
positive contrast agent is _________
radiopaque
negative contrast agent is _________
radiolucent (example: air when inspiring)
what are the two broad forms of pathology?
additive, destructive
additive pathology _________, and is (harder/easier) to penetrate, is more (radiopaque/radiolucent)
adds to tissue density, harder, radiopaque
destructive pathology _________, and is (harder/easier) to penetrate, is more (radiopaque/radiolucent)
takes away from tissue density, easier, radiolucent
the fraction of x-rays removed from a beam per unity thickness of the attenuating medium
linear attenuation coefficient
the fraction of the x-rays removed from a beam of unity cross-sectional area by unit mass of the medium
total mass attenuation coefficient
photon and electron in/out for the photoelectric effect
photon in, (photo)electron out
photon and electron in/out for Compton scattering
photon in, electron out and photon out
