Chapter 7 Flashcards
What is the definition of kinetic energy?
The energy of motion
Symbol: KE; Unit: J (joules); Formula: KE = ½ mv^2
What is the unit of measurement for kinetic energy?
J (joules)
What does 1 kEv equal in joules?
1.6 x 10^-16 J
What are projectile electrons?
Electrons traveling/accelerating from cathode to anode
They constitute the X-ray tube current and transfer kinetic energy to target atoms.
What are the three interaction results of projectile electrons?
- Production of heat
- Formation of characteristic x-ray beams
- Formation of bremsstrahlung x-ray beams
What occurs during anode heat?
When projectile electrons interact with the outer-shell electrons of the target atoms
Approximately 99% of the kinetic energy of projectile electrons is converted to heat.
How is the efficiency of x-ray production affected by tube current?
It is independent of the tube current.
What is characteristic radiation?
Radiation resulting from the interaction of a projectile electron with an inner-shell electron of the target atoms
It involves total removal of an inner-shell electron.
What is an electron cascade?
Emission of radiation when an outer-shell electron fills an inner-shell void.
What is bremsstrahlung radiation?
Radiation produced when a projectile electron is slowed by the nuclear field of a target atom nucleus.
What is the maximum-energy bremsstrahlung x-ray?
When the projectile electron loses all its kinetic energy.
What is the shape of the bremsstrahlung x-ray spectrum?
It extends from zero to maximum projectile electron energy.
What factors affect the x-ray emission spectrum?
- Tube current
- Tube voltage
- Added filtration
- Target material
- Voltage waveform
What is the effect of added filtration on x-ray beam intensity?
Reduces x-ray beam intensity while increasing average energy.
What does a change in mA or mAs result in?
A proportional change in the amplitude of the x-ray emission spectrum at all energies.
What is the rule of thumb regarding kVp and mAs?
A 15% increase in kVp is equivalent to doubling the mAs.
What happens to the discrete emission spectrum with an increase in target atomic number?
It shifts to the right.
How many types of voltage waveform are there?
Five types: * Half-wave-rectified waveform
* Full-wave-rectified waveform
* Three-phase/six-pulse waveform
* Three-phase/12-pulse waveform
* High-frequency waveform
What is the effect of voltage waveform on x-ray intensity and energy?
As voltage increases, x-ray intensity and energy increase slowly at first and then rapidly.
What is the effect of an increase in current (mAs) on x-ray quantity and quality?
Increase in quantity; no change in quality.
What happens when voltage (kVp) is increased?
Increase in quantity and quality.
What is the relationship between added filtration and x-ray quantity?
Decreases quantity and increases quality.
What is the effect of voltage ripple on x-ray quantity and quality?
Decrease in both quantity and quality.
• electrons traveling/accelerating from cathode to anode.
• constitute the X-ray tube current.
• transfer kinetic energy to the target atoms.
• interacts with the orbital electrons or the nuclear field of target atoms.
Projectile electron
• occurs when the projectile electrons interact with the outer-shell electrons of the target atoms.
• does not have sufficient energy to ionize outer-shell electrons.
• constant excitation and return of outer-shell electrons.
• directly related to mA and kVp (diagnostic range). approximately 99% of the kinetic energy of projectile electrons is converted to heat.
Anode heat
• if the projectile electron interacts with an inner-shell electron of the target atoms.
• result when the interaction is sufficiently violent to ionize the target atom through total removal of an inner-shell electron.
Characteristic radiation
What is an ELECTRON CASCADE
emitted when an outer-shell electron fills an inner-shell void.
• produced when a projectile electron is slowed by the nuclear field of a target atom nucleus.
• “slowed-down radiation” (German word)
• results from the braking of projectile electrons by the nucleus.
• an interaction with the nucleus of a target atom.
• energy: all or none
BREMSSTRAHLUNG RADIATION
when the projectile electron loses all its kinetic energy and simply drifts away from the nucleus
MAXIMUM-ENERGY BREMSSTRAHLUNG X-RAY
when the projectile electron is barely influenced by the nucleus.
LOW-ENERGY BREMSSTRAHLUNG X-RAY
the range of values of any quantity extends (such as x-rays)
Spectrum
contains only specific values.
DISCRETE SPECTRUM
contains all possible values
CONTINUOUS SPECTRUM
can be graphed as the number of x-rays for each increment of energy in keV.
X-RAY EMISSION SPECTRUM
a plot of the frequency with which characteristic x-rays are emitted as a function of their energy
CHARACTERISTIC X-RAY SPECTRUM
