Ch.3 Flashcards
If x-rays enter a material such as human tissue, they may
- Be absorbed
- Be scattered
- Be transmitted
Only important types of interactions between x-radiation and matter in diagnostic radiology
Compton, Photoelectric (?)
What is a tech’s biggest source of scatter ?
The patient
When the positron comes to rest, it will combine with any electron and the mass of both particles is converted into energy
Annihilation radiation
During ________ photons strike the image receptor.
Transmission
Partial absorption of the incident x-ray photon. Incident x-ray photon interacts with an outer shell electron of a target atom and removes the electron. Some of the photon energy is transferred to the ejected electron. The remaining energy of the x-ray photon undergoes a change in direction and is given off in the form of a scattered photon.
Compton scatter
Incident X-ray photon interacts with a target atom and excites the atom. No orbital electrons are ejected, no ionization takes place. Contributes to ESE only.
Coherent scatter
Total absorption of the x-ray photon. Incident x-ray photon interacts with an inner k shell electron of a target atom and removes the electron. All of the remaining energy of the incident photon is transferred to the ejected photon (photoelectron)
Photoelectric absorption
X-ray photon interacts with the nucleus of a target atomic
Pair production
Some primary photons will traverse the pt without interacting and reach the IR
Direct transmission
Other primary photons can undergo Compton and/or coherent interactions and as a result may be scattered or deflected with a potential loss of energy
Indirect transmission
This is the most important mode of interaction between x-ray photons and the atoms of the patients body for producing useful images
Photoelectric absorption
What is the diagnostic radiology energy range
23-150 kvp
Less attenuation causes more _______ on the image
Darkness
More attenuation causes more ______ in the image
Light/grays
More attenuation causes more ______ in the image
Light/grays
Responsible for most of the scattered radiation produced during radiologic procedures
Compton scatter
Occurs at the energy level of at least 1.022 million electron volts. Beyond diagnostic range
Pair production
Examples of annihilation radiation/pair production
PET scans
An interaction that occurs at more than 10 MeV in high energy radiation therapy treatment machines
Photodisintegration
Milli =
1000
Centi=
100
Conventional to SI conversion for exposure
2.58x10^-4 c/kg
Conventional to SI conversion for absorbed dose
0.01
1Gy=100 rad
