Imaging equipment: Image production terms Flashcards
what are the 3 parts of an x ray circuit
- primary circuit
- secondary circuit
- filament circuit
what is the primary circuits job?
what is on the primary circuit side?
- Circuit breaker
- Autotransformer
- Kvp Meter
- Primary side of step up transfer
- Exposure timer
what does the circuit breaker do?
breaks the circuit, incase the x-ray machine drives too much power
what does the autotransformer do?
changes the kvp to certain settings. Kvp selection
- it is self induction
-single coil of wire
-works off of Alternating current
what does the exposure timer do?
controls how long the exposure stays on
what does the primary side of the step-up transformer do?
steps up the voltage from volts to kilo volts.
-uses mutual induction
-2 coils of wire
what components are on the secondary side of the circuit?
- Rectifier
- X-ray tube
- Secondary side of step up transformers
what does the rectifier do
converts alternating current into direct current
think * AC DC
What does the x-ray tube do?
converts electrons into x-rays
secondary side of step-up transformers
converts volts to kilovolts
what components make up the filament circuit
- Rehostat
- step down transformer
what does a rehostat do?
a variable resister that is connected to the mA selector controls the heat in the filament.
-selects the mA
-“turn up the heat” think of a thermostat (when you chose the mA, correlate that with thermoinioc emission)
-also called variable resistor, and mA selector**
what does the step down transformer do?
Voltage is being decreased, then the mA increases.
Has 2 jobs: decreases voltage and increases amperage
single phase
100% ripple is the worst
3-phase, 6 pulse
14%, old equipment = bad
3-phase, 12 pulse
4 %, not as bad but still not the best
High frequency
1 %= best! new equipment
more ripple = higher % which is
bad!!!!
secondary circuit electricity is in?
kilo volts
what is the filament circuits job?
modifies the incoming- line power to produce the thermionic emission from the filament wire of the x-ray tube by a sequence of devices
what does the line voltage comp senator do?
measures the incoming line voltage
what is the incoming voltage coming into the circuit?
220 volts
-alternating current
which transformer comes first in the circuit?
autotransformer
the autotransformer works on what type of induction?
self induction
the step up and step down transformer work on what type of induction?
mutal induction
what is the difference between direct and alternating current?
direct= electrons only flow in one direction
alternating= electrons change directions
x-ray tube uses what type of current?
direct current due to anode to cathode
transformers can only function using what type of current?
alternating current
Ohm’s law
V = Voltage
I = Amperes
R= Resistance
series circuit
all the resisators connect in a continuous line
parallel circuit
current can flow beyond one continuous line and is made up of multiple sections, meaning the circuit can still work if there is a break
what is the focusing cup made out of?
Nickle, or molybdenum
what is the anode target made out of?
Tungsten- rehiuem
what spins the anode?
the rotor
what is the anode heel effect?
-Anode heel effect refers to the lower field
intensity towards the anode in comparison to
the cathode due to lower x-ray emissions from
the target material at angles perpendicular to the
electron beam.
-The anode surface is not flat, it is at an angle.
-“Fat Cat”
-Put the thicker part under the “cat”
why is the anode side weaker?
because the anode is at an angle
-whereas the cathode doesn’t have anything in it’s way
decrease anode angle
-anode angle is smaller
-it increases the heel effect!!!
what effects the anode heel effect?
- Degree of anode angle
a. Decrease anode angle (steeper) = increase in anode heel effect - SID
a. Decrease in SID = increase anode heel effect (Not as present at 72”). Would increase at a shorter SID - Field Size
a. Increase field size = increase in anode heel effect.
mAs repciprocity law
mA and time are inversely proportional. they go in the opposite directiosn
FOV
the size of your light field is the field of view
increasing FOV =
decrease collimation = larger light field
positive beam limitation
light field is limited to the size of the IF place in the bucky tray
patient size in collimation 
-increase in patient size =how absorption of the beam into the tissue
-less photons will reach the IR =less receptor exposure 
decrease collimation = increase field of view which is
a larger light filed
for larger patients
decrease filed of view!!!
also increases collimation
what is the relationship between beam restriction and receptor exposure?
increasing beam restriction will reduce receptor exposure.
-Receptor exposure is a collection of both primary and secondary radiation a larger Lightfield will increase the amount of radiation reaching the plate.
what is FSS
focal spot size is used to control spatial resolution ( detail)
-small focal spots: produce less blurring and better visibility of detail ( extremity work and ribs)
-large focal spots: have a greater heat- dissipating capacity. (chest and abdomen)
size distortion
magnification of the part
-primarily controlled by OID
-secondary controller is SID

SID can be used to compensate for increase in OID
for every 1 inch increase in OID a 7-8 inch increase in SID should be used to compensate 
1 inch =
2.54 cm
40 inch
102 cm
72 inch
183 cm
shape distortion
is either elongation or foreshortening of the part 
elongation
that part appears longer
resulting from the angle in the tube and image receptor (TIRE)
-we use this to help visualize anatomy for certain images, example and axial calcaneus 
foreshortening
the part appears shorter
- angling the part
-happens in trauma
what does filtration do
primary beam filtration reduces skin does by filtering out the low energy harmful rays 
a filter is placed in the x-ray beam to remove long _________ x rays
wavelengths (low energy)
- Low energy, x-rays contribute nothing to the diagnostic image by increase patient toes through photo electric effect 
has low energy x-rays are removed the average energy of the beam _____
increases
removing the low energy raise results in a ________ patient dose 
lower
technologist never, just filtration it is only adjusted by the physicist 
how will beam filtration affect the primary beam? 
It will make it more homogeneous by producing a beam of mainly high energy x-rays 
filtration _____ the quantity of the beam
reduces
filtration _______ receptor exposure
decrease
filtration ______ the patient skin dose
reduces
filtration _______ contrast
decreases
what is inherent filtration
in the x ray tube
- in the glass envelope of the x-ray tube. Insulating oil around the tube. 
added filtration
aluminum sheets placed in the path of the beam
-works as filters to attenuate low energy photons 
what is total filtration
inherent + added
Minimum filtration requirements NCRP 102
above 70 kvp= 2.5 mm Al equivalent
compensating filters
compensating filters are external filters placed on the collimator of the x-ray tube. They are used to compensate for different thicknesses in densities. 
common names for compensating filters 
- wedge
-boomerang
-trough - a t spine varies in thickness and density a wedge filter may be used to compensate for the variance 
Half value layer 
amount of filtration that reduces the intensity of that to half of its original value.
-Divide by two.
-use lead or AL sheets done by a physicist
if you increase KVP the HVL
also increases
what is the half value layer definition? 
decrease the intensity of the primary beam by 50% of its initial value 
how many have cellular hours will it take to reduce an x-ray beam who is intensity is 78R/min to an intensity of less than 20 R/min 
2
78/2= 39
39/2= 19
attenuation means what
the reduction in intensity of the x ray beam as result of absorption scatter and divergence
higher atomic # = ________ attenuation
increased
increase part thickness = ________ attenuation
increased
increase in kVp= ______ attenuation
lower
absorption
absorption of the x ray photons happens through the photoelectric effect
differential absorption
different objects absorb radiation differently
air = ______ absorption
decrease since it shows up black and isn’t as dense as bone!
bone = increased absorption
where is AEC located
- AEC units are found in either the table, Bucky or wall Bucky not in the image receptor
- between the patient and the IR
what does the technologist set when using AEC ex.) kvp
- KVP
-mA
-select the appropriate chambers
-the ioniziation chamber will determine the exposure time and terminate the exposure when the part is fully penetrated
what are advantages of AEC
- decreased repeat exposure rate due to underexposure
- decreased pt exposure with less repeat images
-increased department efficiency with less repeat images
ionization chamber
behind the patient and in front of IR
- the ionization chamber interacts with exit radiation before it reaches the IR
failure to center correctly using an AEC
Failure to center part of interest over the selected photocell can result in an over or under exposure!!!
PA chest
use two outer cells
factor changes that will affect AEC
as mA increases = AEC( length of exposure time) decreases. why: due to mAs recpiatory
as kVp increases= AEC decreases. why: have a higher energy beam more penetrating less time
as SID increases = AEC increases why: it’s going to take more time to get their
as density setting increases = AEC increase. why: use density setting so it can more dense or less dense + 1 or +2
disadvantages of AEC
- accuracy position over selected cells
- pathology
- prosthetic devices
- collimation
exposure index is what
conserve as an indicator of the relative exposure, used for a particular exam. Technologist should be educated on exposure ranges for each equipment used. exposure ranges are specific to equipment type and manufactur
CR= S number
inverse relationship
high number = underexposed (600)
low number = over exposed ( under 75)
DR= EI, DEL, REX#
direct relationship
high number = over exposed
low number = under exposed
Variable KVP
kvp varies
mAs is constant 
fixed kVp
kvp is fixed
mAs varies
anatomically programmed technique
A suggested technique of KVP an mAs
high voltage
used for barium and chest x ray
ideal MTF is
1
- spatial resolution
what is exposure latitude
exposure latitude is defined as the range of exposures that produces quality images at an appropriate patient dose 
the higher the pulse the ______ voltage ripple
lower
rotating anodes are used an x-ray tube
 Increase tube heat dissipation
A radiograph of the abdomen is obtained using automatic exposure control. Which of the following is likely to occur if a second image is obtained after the introduction of 250 mL of oral barium?
Increased exposure time
- AC will increase the exposure time to maintain image receptor exposure, because barium absorbs more radiation, and therefore more exposure is needed to produce a quality radiograph. 
what is the function of AEC?
To provide proper exposure, and therefore image receptor exposure is maintained 
