EX1; Podcast - Principles of X-Ray Production Flashcards
When is an X-ray produced
when highly accelerates electron are suddenly brought to a stop by hitting a stationary object
What specifically is converted into X-rays via the high speed electrons
kinetic energy
This mechanism for production involves electron to nucleus interaction
bremsstrahlung
“braking radiation”
What are the three requirements for x-ray production
electrons
high velocity (electrons)
high Z-number absorbing material/target (i.e Tungsten 74W)
The higher the what, the greater the kinetic energy of the electron
velocity
KE = 1/2mV^2
True or False
All the electrons move at the same velocity
False; some move at high velocity than others
What occurs when some electrons striking the nucleus suddenly stop and give off all their KE
a single high energy x-ray photon is produced
Most electrons pass close to the nucleus, decelerate and give up some of their KE and produce this
x-ray photons with various energies
This mechanism for production involves electron to electron interaction
characteristic radiation (K-radiation)
How does characteristic radiation cause ionization
incident electrons interact with K (or L) shell electrons of target (tungsten) atoms
What is the result from characteristic radiation
heterogenous x-ray beam but much narrower energy spectrum than Bremsstrahlung
What is the target/focal spot made of
tungsten embedded within the copper anode
What are the actual dimensions of the target/focal sport
1x3mm
What are the effective focal spot dimensions; it is angulated (20º) to produce a beam from a smaller area
1x1mm
Why is tungsten used as a target
high melting point and heat stability
high ductility
produces predictable and optimal energy x-rays
high atomic numbers
high thermal conductivity
low vapor pressure (don’t want vapor in vacuum)
What percentage of diagnostic x-ray beam is characteristic radiation
30%
This is a significant byproduct of X-ray production (over 99%)
heat
What is used to reduce overheating of the target
copper stem of anode and oil immersion
The heterogenous x-ray beam produced at the anode is net out of a lined tube through what
the portal; a channel for the passage of X-rays
This absorbs less penetrating (long wavelengths) x-rays which are harmful
the filter; made of aluminum
X-rays with longer wavelengths are mostly absorbed by what and do not reach the target tissues
skin
What is the half valve of the filter
the thickness of it; reducing number of X-rays passing
This is “shaping of the beam”
collimation
What does x-ray beam collimation greatly reduces what
unnecessary exposure to patients
Most x-ray tubes have which type of collimation
round (7cm)
This type of collimation is slightly larger than the size of the image receptor
rectangular
This shaped diaphragm limits the size of divergent beam
doughnut
This farther reduces the beam size providing mean of aiming the beam
external collimator
What are the necessary conditions for x-ray production involving electrons
separation of electrons
concentration of electrons
imparting high speed to the electrons
sudden stopping of the electrons stream to produce x-rays
The purpose of this is to supply electrons through a heated filament cathode is the negate electrode
cathode
The cathode filament is recessed into what to help contain and direct electrode
molybdeum focusing cup
The purpose of this is to stop the high energy electrons and to convert their kinetic energy into x-rays and the positive electrode
anode
This is low-voltage circuit, filament made of tungsten, molybdenum focusing cup, and electron cloud
cathode
This is high-voltage circuit, angled tungsten target/focal spot, heat absorber/radiator (copper)
anode
The production and separation is much like this
like a light bulb
“thermionic emission”
The electron cloud is produced at what
the filament
The electrons become more active by what
random collisions producing more free electrons
Theis located at the cathode serves to concentrate the electrons
molybdenum collar (focusing cup)
When the high voltage circuit (at the anode) is activated, these concentrated electrons form a beam that does what
hits the focal spot located on the face of the copper anode
What activates the high voltage circuit at the anode
high potential difference created between the filament cathode and target anode
These parts of the control panel influence radiographic imaging
millamperage (number of electrons)
exposure time (between cathode/anode)
kilovoltage
These are factors influencing radiographic image
density, contrast, resolution
distortion
filtration and collimation
True or False
The distance from source to receptor and the distance from object to receptor can play a roll in radiographic image
True
Object attenuation (absorption) depends on what
density (of bone and such)
atomic number
thickness
The permeability of x-rays depends on what
photon energy
thickness of object
density of the object being radiographed
This is the complete absorption of the beam of object (like amalgam)
photoelectric absorption
This is almost complete absorption (like cortical bone)
coherent/thompson scattering
True or False
There is no such thing a complete penetration to receptor
False; there is in air filled spaces like the maxillary sinus
This is scatter-partial/tangential exposure of receptor; undesirable but always occurs
compton scattering
