Image Production 4.2 Flashcards
Cassetteless digital systems have a fixed spatial resolution determined by
(TFT) Thin film transisitor
(DEL) detector element size. Size is fixed so max detail is defined by physical size of the individual elements
Cassetteless system
direct or indirect digital system; where no cassette/IP is used.
CR
uses IP containing PSP
Laser divergence
negative factor that occurs in CR readers
Focal spot size
appropriate for anatomical part being imaged is important to render optimal image resolution
Proximity of the phosphor screen crystals
refers to conventional film-screen radiography
If 30/23/15cm TRIFOCUS IMAGE INTENSIFER is operated in the 15-cm mode, the fluoroscopic image will be magnified by a factor of?
The degree of magnification (MF) is found by dividing the fullsize input diameter by 30 cm by the selected input diameter (15 cm) MF = 30 cm/15 cm =2.0
If image intensifer was operated in the 23-cm mode, the MF would be 30/23=1.3. If the II was operated in the 30-cm mode, the MF would be 30/30=1.0
Device used to change ac to unidirectional current is
Solid-state diode; AKA rectifiers. Md of semiconductive materials suchas silicon, selenium, germanium that conduct electricity in only one direction.
xray circuit devices suchas transformer/autotransformer
operates on AC
xray tube
operates on unidirectional. So current RECTIFIED before it gets to tube.
Process of full wave rectification
changes neg halfcycle to useful positicleve halfcy
XR circuit rectification system
located between secondary coil of the high-voltage transformer and the XR tube
A series of rectifiers placed between transformer and XR tube
function to change AC to more useful DC
During CR imaging, the latent image present on PSP changed to a digital signal by the
ADC analog to digital converter
Exposed CR cassette is placed into CR scanner/reader
where PSP is removed automatically
The latent image appears as the PSP is scanned
by helium neon laser to obtain pixel data
PSL photostimulated luminescence
As the plate is scanned in the CR reader, it releases a violet light
The analog image
the luminescent light is converted to electrical energy
The electrical energy is sent to ADC
where it is digitized and becomes the digital image that is displayed eventually on highres monitor or printed by laser printer
The secondary side of autotransformer feautres 2 multiple channel selection switched, to choose the number of coils that will supply voltage to the primary side of the high voltage transformer. Choosing more or less coils exploits
The transformer law
The KVp selector
is an array of multiple connection points to the autotransformer coils on the theoretical secondary side of the device
autotransformer
operates on self-induction; having one column of coided wire tha functions as bothe the primary and secondary side.
autotransformer
by changing the number of coils selected, the technologist is setting the value for Ns, the number of turns of the secondary side of the transformer.
Transformer Law
Vs/Vp = Ns/Np
By changing Ns, the tech is indirectly changing secondary voltage.
mA selector
Ohm’s Law
Focusing cup
Coulomb’s Law
To explit E=mc2, the mass to energy conversion formula
need PET scanner, nuclear power plant, nuclear weapon
Combos that offer the greatest heat-loading capability
The smaller the focal spot size, the more limited the anode is with respect to the quantity of heat it can safely accept
Combos for anode include t
target angle and focal spot size
12-degree target angle, 1.2-mm actual focal spot
Note: a steep target angle increases the heel effect
Mask image
Digital image subtraction. Pixel values are electronically subtracted fr pixel values
Ghost/phantom image
an image artifact; the appearance of ghost images can be seen when CR image plates are incompletely erased or IP has not been used for 24 hrs
Moire image/artifact
if a grid has a frequency that approx the CR scan frequency and the grid strips are orientated in the same direction as the scan.
Latent image
is image exsists on film prior to chemical processing.
In Digital Fluoroscopy what is eliminated
“overheads” -images sent thru ADC allows images post-processing which eliminates nd for overheads
what is the smallest particle of an element that retains the characteristics of the element
“atom” - An element is md up of 1 kind of atom.
The atom may be broken down into subatomic particles but not have characterisitics of the element
xrays travel as bundles of energy called
photons or quanta
Atomic mass
is the number of protons and neutrons in the nucleus represented by the letter “A”
When a predetermined level of ionization is reached in the ionization chamber, what does the machine do
Exposure is terminated.
AEC is very dependant on KVP
What type of XR machine uses a continually decreasing mA for the shortest times possible
“Falling load generator”
Allowing for shortest exposure time mks use of max heat storage capacity at every mA.
What type of current is req’d for proper operation of the XR tube
“unidirectional/direct current/DC”
uses rectifer to change AC to DC
