lecture 3 prod of xrays PART 2 Flashcards
flow of electrons through an electrical conductor
electricity
amount of electrons flowing through a conductor per second
current [measured in amperes A] [also called mA]
path of electrical current
circuit
difference in electrical potential energy between two points in an electric circuit.
voltage (potential difference) measured in volts V
during each 1/2 cycle (1/120 of a second) anode is positive and
attracts the electrons from the cathode
[electricity]
during each alternate 1/2 cycle (1/120 of a second) anode is negative, therefore,
no attraction for electrons exists and no x-radiation is produced (inverse voltage)
in the USA ___ cycles of electricity per second
60
changes alternating current into direct current
full wave rectification
full wave rectification has ____ potential between cathode and anode.
constant potential
full wave rectification has highest volt possible, so means more efficient ___ at producing x-rays and x-rays produced will have a ___energy
electrons
higher energy
constant potential and direct current will have:
____exposure times
_____beam intensity
_____mean energy of beam
_____radiation dose
shorter exposure times
more consistent beam intensity
higher mean energy of beam
decreased radiation dose
how are x-rays produced?
whenever high-speed electrons are suddenly decelerated or brought to stop when they pass close to nucleus of high Z # abosrobing material (tungsten)
what are the 2 mechs for x-ray formation
bremsstrahlung radiation and characteristic radiation
breaking radiation mech/ electron to nucleus for xray formation
bremsstrahlung radiation
electron to electron interaction
characterisitic radiation
mech where fast moving electrons either slow down or stop when they come close to the nucleus of the atoms and part of their energy is transferred as xrays
bremsstrahlung radiation
mech when electrons displace inner shell electrons, this mech is produced
characterisitic radiation
high-velocity electrons directed toward the target material
bramsstrahlung radiation
with bramsstrahlung radiation, higher the velocity, the ____the KE of electrons.
bramsstrahlung radiation increases with _____ the voltage (kV) and the atomic number of the target
greater KE (higher velocity)
radiation increases with increasing voltage
two types of bramsstrahlung radiation
- impacting electron is deflected and decelerated. kinetic energy lost is emitted as an x-ray photon
- head-on collision with nucleus: electron brought to rest producing a max energy photon
this type of radiation has a wide distribution of wavelengths (heterogeneous)
bramsstrahlung radiation
what happens when electrons interact with tungsten atoms during bramsstrahlung radiation?
electrons lose their energies in random fashion
summerize bramsstrahlung radiation steps
- electrons with different voltage are accelerated towards the anode under the influence of high kilovoltage
- at anode, they either interact with nucleus or rapidly decelerate and get deflected (change direction)
- process results in the release of energy in the form of x-ray photons (eV)
this radiation arises when cathode electron collides with inner orbital electron of Tungsten atom (target) and removes it from orbit. then, the atom is now ____ and unstable
characterisitic radiation
atom is then ionized and unstable
during characterisitic radiation, the hole left by the electron is:
filled by electron from outer shell, and energy is emitted from this electron in the form of x-ray radiation characterisitic of tungsten and the involved shell
with characterisitic radiation, the energy emitted by the electron is equivalent to the difference in the binding energies of the
two shells/orbit
with characteristic radiation, when an outer shell electron is shifted inward it must give up some of its energy in the form of radiaiton called
a characterisitic photon
this radiation makes up the majority of the x-ray beam and produces a heterogenous beam of varying photon energies
bramsstrahlung radiation
this radiaiton is only a minor source of radiation from the x-ray tube and produces photon energies specific for the target material
characteristic radiation
