exam 5,7,8 Flashcards
What do the rectifiers in the secondary circuit do?
convert AC to DC
Which waveform has the lowest percentage voltage ripple?
High-frequency
According to the Line-Focus Principle, an anode with a small angle provides:
improved recorded detail
improved heat capacity
The most common cause of x-ray tube failure is:
Vaporized tungsten on glass envelope
Double-focus x-ray tubes have two:
Focal spots, Filaments
The function of the cathode is to produce
thermionic cloud
Filament materials are chosen primarily for their
high melting points
What affects the production of a thermionic cloud?
filament diameter,
filament length,
filament temperature
What causes a filament to break
vaporization
Driving the thermionic cloud from the cathode to the anode requires
a high voltage
The cathode focusing cup has a ____ charge
negative
Tungsten is the material of choice for the source of x-ray photons primarily because of its
high atomic number
Pitting of the anode commonly occurs
with extended use
Cracking of the anode typically occurs
when a cold anode is hit with a high kVp exposure
The actual focal spot is controlled by the
length of the filament
As the actual focal spot size increases, the effective focal spot size
increases
As the angle of the anode increases and the incident electron beam size remains the same, the effective focal spot size
increases
The use of the line-focus principle causes a problem known as the ____ effect.
anode heel
What type of radiation is composed of photons not produced at the actual focal spot?
off-focus
extra-focal
As an x-ray tube ages, the inside can become coated with tungsten, which can cause _____ in the tube.
arcing
Thermionic emission at the filament creates a __________.
space charge
When electrons bombard the target, ____% of their kinetic energy is converted to heat.
99
The ___________ is the source of radiation in the x-ray tube.
focal spot
Tube failure can occur from _______________.
long exposure times
A dual focus tube has two _______.
filaments
The single function of an AEC is to eliminate the need to set
time
When using an AEC, the radiographer loses control of
mAs
The most common AEC configuration includes
three chambers
a center chamber at the center of the image receptor
the left and right chambers slightly higher and lateral.
When an AEC is used for an AP lumbar spine, which ionization chambers are utilized?
the center cell
When an AEC is used for a PA chest, which ionization chambers are utilized?
the left and right outer cells
If the primary beam is collimated from an activated chamber, the result is a
dark radiograph
During x-ray production, almost all of the kinetic energy of the incident electrons is converted t
heat
The transfer of the incident electrons’ kinetic energy to the outer-shell electrons, causing vibration of the outer-shell electron, results in the emission of
infrared radiation
The energy of a bremsstrahlung photon is
the difference between the entering and exiting kinetic energies of the incoming electron
Characteristic interactions may occur only when the incident electron interacts with
an inner-shell electron
During a characteristic interaction, the kinetic energy of the incident electron must be ____ of the electron it knocks from its orbit.
greater than that
At the end of the characteristic cascade, the ____ shell is missing an electron.
outermost
The K shell can hold a maximum of ____ electrons.
2
When comparing the x-ray emission spectrum between beams produced at 70 kVp and 110 kVp,
the 110 kVp beam would demonstrate more brems and a higher characteristic spike.
Projectile electrons travel from ______________.
cathode to anode
Most of the heat generated at the target is due to ___________.
outer-shell excitation
The useful characteristic x-rays from tungsten targets are ___-shell x-rays.
K
Bremsstrahlung x-rays are produced by ______________ at the target.
slowing electrons
The quantity of bremsstrahlung radiation increases proportionately with increased _____.
mAs
What percentage of target interaction results in the production of x-ray photons?
1%
What is required for x-ray production?
Source of electrons, rapid acceleration, rapid decleration
What is the source of electrons in the x-ray tube?
cathode filament
Whaty is the technical factor that accelerates electrons in the x-ray tube?
kVp
controls energy
What happens during thermionic emission?
Free electrons are created
What kind of current is required to induce thermionic emission?
high
What does Bremsstrahlung radiation interact with?
electric field of the nucleus
What variables affect the energy of a bremsstrahlung photon?
energy of the incident electron, proximty of the electron to the nucleus
What controls the energy of bresstrahlung photons?
tube potential
kVp
The types of target interactions that occur during x-ray photon production in the diagnostic range are dependent on what factor?
instant electrons kinetic energy
What is the energy of the brems photon?
the difference between the entering and exiting kinetic energies
A bremstralung interaction only occur when the instant electron interacts with?
the forcefield around the nucleus
Charectiristic interactions may occurs only when the instant electrons only interact with?
inner shell
During a characteristic interaction the energy of the incident electron must be what
greater
During a characteristic interaction the dropping of a higher state electron into a lower state results in?
photon
The energy of the characterstic photon is?
the difference of the binding energy of the outer and inner shells.
