physics Flashcards
Beam hardening refers to the removal of?
low energy x-rays from a polyenergetic beam.
All x-rays in a monoenergetic beam have the same energy, which does not change as the beam passes through a given material. In a polyenergetic beam, lower energy x-rays have a higher probability of absorption than higher energy x-rays and are therefore removed from the beam preferentially as it traverses a given material. As such the energy of the beam increases with depth and becomes “harder”.
The probability of photoelectric absorption in an absorber is proportional to
Z3
E-3
The charged particle interaction that occurs most frequently in a tungsten target x-ray tube is?
excitation. Approximately 99% of electrons incident on the x-ray tube target interact through excitation which produces heat.
Bremsstrahlung interactions result in??
polyenergetic x-rays.
the force of attraction between the electrons and the nucleus varies inversely with distance squared, the magnitude of energy lost varies, and a polyenergetic x-ray beam is produced.
What is the principal source of x-rays produced in an x-ray tube?
Stopping high speed electrons = BL
For a given cathode filament size, what is the effect as the anode angle is decreased?
Decreases in the apparent focal spot size and decreases in the heat load capacity
Which of the following are characteristics of x-ray beam filtration?
Filters made from higher atomic number material attenuate more higher energy x-rays
Inherent filtration is not the primary source of filtration. added filtration provides using higher Z materials provides the most attenuation.
Since mammography is done at low energies copper would remove almost the entire spectrum and would not be a good filter to use.
Which of the following is true regarding the K-edge filtration utilized in mammography?
It produces a smaller range of photon energies in the output spectrum
K-edge filtration reduces the overall spectrum with maximum reduction occurring just above the k-edge. If the atomic number of the filter is less than that of the target material the k-edge would also be decreased, because of this the attenuation would not be above the characteristic radiation produced in the target and this characteristic radiation would be absorbed more. Also, k-edge filtration doesn’t involve electrons therefore the answers discussing electrons are incorrect.
Which of the following determines the maximum energy of Bremsstrahlung x-rays produced in an x-ray tube operated at 100 kVp?
The peak voltage applied between the cathode and anode
What would be the result if the amount of added filtration is changed from 2 mm to 1 mm of Aluminum filtration?
The radiation dose to the patient would increase and the HVL would decrease.
Wti is the unit of light measurinf on the surface
Lux is a measure of illuminace
Candela: illuminace intensity
Roentgen: exposure
EM enrgy is measured in
Kev. dont choose J
in Mag MG we use ?
small FS
compresion mode
