X-ray production Flashcards
On the cathode side of the x-ray tube, neg. charged electrons are boiled off of the thoriated tungsten filament wire in a process known as
Thermonic emmission
They form what is called a
space charge or electron cloud
electrons are herded together by the neg. charged
nickel focusing cup
when the exposure switch is depressed, the anode begins to rotate as the _ is created
space charge
The distance between any 2 successive points on a wave
wavelength
the max. height of the wave
amplitude
the # of waves that passes a particular point in a given time frame
frequency
frequency and wavelength are _ proportional
inversely
Photon energy and frequency are _ proportional
directly
The three factors that affect x-ray emission are under who’s control
radiographer
The three factors that affect x-ray are known as
prime factors
What are the prime factors
mA, kV, S, and distance
what is the measurement of the #’s of electrons crossing the tube per sec.
mAs
what is the primary controlling factor for x-ray quantity
mAs
more mAs = _ density on the image
more
mAs is calculated my x
mA x s of exposure
what is the primary controlling factor for x-ray quality
kV
Higher kV = _ penetrability
higher
Higher penetrability = _ scatter and _ density on the film
higher, higher
kV is a _controlling factor for density (quantity)
secondary
The relationship of x-ray quantity to distance is described in the
inverse square law
If distance is doubled from an x-ray source the pt would only receive _ the radiation
1/4
Distance and radiation intensity are _ proportional
inversely
what is the formula for inverse square law
I1 (D2)2
— = ———
I2 (D1)2
Exposure Maintenance formula or DSL
mAs1 (D1)2
——- = ——-
mAs2 (D2)2
What formula states that if the radiation intensity decreases, the density on the image receptor decreases
Exposure maintenance formula or DSL
Intensity and density are _ proportional
directly
x-rays qualities
highly penetrating
invisible rays
form of electromagnetic radiation
x-rays are electrically
neutral
x-rays are not affected by either _ & _ fields
electric and magnetic
x-rays can be produced over a wide variety of
energies and wavelengths
polyenergetic and heterogeneous
x-rays release very small amounts of _ upon passing through matter
heat
x-rays travel in
straight lines
x-rays travel at the
speed of light
x-rays can _ matter
ionize
x-rays cause _ of certain crystals
fluorescence
x-rays cannot be _ by a lens
focused
x-rays affect
photographic film
x-rays produce _ and _ changes in matter through ionization and excitation
chemical and biological
x-ray produce
secondary and scatter radiation
x-ray beam after it exits the tube and before it enters the pt.
primary beam
x-rays that exit the pt to strike the image receptor
exit
weak x-ray photon interacts with the force field of an atom and is absorbed. The atom is put in an excited state and releases the energy in the form of a scattered x-ray that is traveling in a different direction than originally
coherent scatter
Coherent scatter is also called
classical or Thompson or Rayleigh
Coherent interacts w
entire atom
Coherent scatter is in what range
below diagnostic range
What has a net loss of e-
compton scatter
compton interacts with
outershell e-
Compton causes
radiographic fog and is responsible for may. of scatter during procedures
what has total absorption of k-shell
PE
photoelectric effect creates
photoelectron
what creates the annihilation affect and is above the diagnostic range and interact w/the nuclear field
Pair Production
what interacts with the nucleus and is above the diagnostic range
Photodisintegration
what is the reduction in # of x-ray photons in the beam as it passes through matter due to scatter and absorption
Attenuation
attenuation is affected by 2 things
thickness of body pt
z# of the tissue the beam is striking
Attenuation is caused by
absorption (PE)
scatter (compton)
what are the 3 principal parts of an x-ray system
x-ray tube
operating console
high voltage generator
x-ray tube has a protective housing which reduces
amount of leakage radiation
the housing often contains
oil
the oil serves as both an insulator against _ and as a thermal cushion to
electric shock
dissipate heat
the tube is a vacuum tube made of either
glass or metal
vacuum tube is also known as
diodes
diode means what
has two ends one positive and one neg.
neg. end of tube is known as
cathode
positive end is known as
anode
the cathode contains
the filament
focusing cup
most tubes are _
dual focus
dual focus means
they have both large and small filament w?different levels of resolution
most tubes have rotating anodes why?
to dissipate heat
target has
have high z#
excellent conductor of heat
high melting point
target consists of
tungston
the target is supported by
molybdenim and graphite
an induction motor that is located outside of the glass housing
stator
the stator causes the rotor to
spin
there are slight changes in the voltage coming into the x-ray circuit from the wall outlet. This keeps the voltage coming in at a steady 220 volts
line compensator
what has a single coil and can at most either double the incoming voltage, thus cutting the incoming amperes in half or vice versa
autotransformer
this cuts off the current in order to stop the x-ray exposure
exposure timers
exposure timers are
electronic timers
step up transformer works by
mutual induction
step up transformer has more coils on the
secondary side vs the primary side
what reduces current to mA
step down transformer
step down transformer has more coils on the
primary side than on the secondary side
what only allow current to flow in one direction, thereby changing the incoming AC to DC
rectifiers
Single phase, the wavelength of the electricity rises and falls
120 times per second
single phase has _%voltage ripple
100
what is three lines of current run at the same time, keep the sine wave amplitude at its peak nearly all of the time
three phase power (3 phase 6 pulse fully rectified)
three phase power has _% voltage ripple
14%
what are 4 beam restricting devices
aperture diaphragm
cones/cylinders
collimators
PBL
when an image receptor is placed in the bucky, a sensing device automatically sets the collimators to film size
PBL
