Exam 2 Flashcards
What is another name for overexposed?
burned out
If the film is too dark it is
a. overexposed
b. underexposed
a
If a film is too dark but can see the structures what should you do?
decrease kVp 15%
T/F
kVp and mAs can make a film darker or lighter
True
Quantity of x-rays is under the control of ________
a. mAs
b. kVp
a
What is the primary function of mAs?
Density
Patient exposure to x-ray is __________ with increased mAs
a. increased
b. decreased
So, increasing the mAs will do what to the x-ray?
a
Quality of the beam is under the control of…
a. mAs
b. kVp
b
What should be done if an x-ray is underexposed? (too light)
Double mAs or increase kVp by 15%
What should be done if an x-ray is overexposed?
half mAs or decrease kVp 15%
beam penetrability is controlled by the ________
kVp
Patient exposure is ____________ affected by kVp
a. greatly
b. not greatly
b
What percentage should mAs be change to make the 1st visible change in density?
30%
_______ mAs will reduce density by 1/2
50%
T/F
30% and 50% rules apply to both mAs and kVp
false, only mAs
If you can’t see any structures on an x-ray because it is too light, what do you do?
increase kVp 15% AND double mAs
decreasing mAs can be done by either…
decreasing the time or mAs
decreasing time of mAs will lessen what?
motion
at a high mA station decreasing mA will ________ stress on the tube
a. decrease
b. increase
a
What is the 50% reciprocal rule?
doubling the mAs doubles the density of the film
doubling the time would allow ________ patient motion
a. more
b. less
more
When a film is too dark but you can still see the structure use the _________
50% rule
If a film is too light buy you still see the structures what do you do?
double the mAs
What does the kV control?
film contrast, it will also change the film density
a film that has too low of a kV will be what?
a. too light
b. too dark
why?
a
what ever is being x-rayed is under penetrated
If a film is too dark from too much kV, it is known as?
over-penetrated
how much kv to see the first change of density of a film?
4
________ increase in kV will 2x the density of a film
15%
a 15% decrease in kV will do what to the density?
decrease it by half
15% of the kVi s equal to what in mAs?
1/2 mAs with a decrease in kV of 15%
2x mAs with an increase in kV of 15%
The optimal kV drives the best contrast with…
the least amount of radiation
If a film is too dark and you can\t see structures what do you do?
decrease both kV and mAs
If the film is too light and you can’t see structures what do you do?
increase kV and mAs
what will the film look like if the film density is too high?
it will be too dark
film fogging will increase or decrease film density?
increase
What are some examples of film fogging?
What will the end result be?
scattered rays regular (overhead) light safe light increased developing temperature, time or concentration expired film
increase film density (too dark)
Decreased tube distance without reducing the technique will increase or decrease film density?
increase
increasing film size and collimation without reducing technique will increase or decrease film density?
increase
T/F collimation from a smaller size to a larger one will add density
Why?
What will the end result be on the film?
true
more scatter
increased density (darker)
lack of a compensating filtration that is needed for a body part will result in what?
increased film density
not using the grid with grid technique factors will increase or decrease film density?
increased film density
Wrong film-screen combination will increase or decrease film density?
increase
tissue, body build and age will do are all factors to what
film density
incomplete exposure will increase or decrease film density
decrease
a malfunction in equipment will increase or decrease film density
decrease
An increase in tube distance without increasing the technique will increase or decrease film density
decrease
Film density is greatest with ___________ and least with _______
air; bone/metal
The difference between densities is known as what?
film contrast
films that are black and white generally have ________ contrast
a. high
b. low
a
T/F In a high contrast film the film is generally bright and dark with many step in between?
False, few steps between
A high contrast film is also known as a ____________, and have a _________ exposure latitude
a. short scale contrast; narrow
b. short scale contrast; wide
c. long scale contrast; narrow
d. long scale contrast; wide
a
A low contrast film is also known as a ____________, and have a _________ exposure latitude
a. short scale contrast; narrow
b. short scale contrast; wide
c. long scale contrast; narrow
d. long scale contrast; wide
d
______ contrast films are generally grey and have little black and white.
low
for higher contrast films use ________ kV and __________ mAs.
lower; higher
For lower contrast films use ___________ kV and _________ mAs
higher; lower
For one imaging we basically want a relatively __________ contrast
a. high
b. low
a
Film is manufactured for different contrast this is called___________ or ___________
detector contrast or film contrast
What controls contrast
a. kV
b. mAs
a
to increase contrast if the film is too gray _________ kV and _________ mAs.
decrease kV and increase mAs
if the density of a film is good but too gray what should you do?
cut the kV by 15% and 2x the mAs
Is contrast better or worse when the film is too light?
worse
2x mAs is equal to what in kV?
15%
What do you do to kVs and mAs if you need to decrease the contrast?
cut mAs in half and increase kVs by 15%
Contrast is better or worse when a film is too dark?
worse
What are some things that can adversely affect contrast on a film?
fog of any type
processing problems
too much or too little selective filtration
wrong film for the screen used
using a frid with anon grid technique and visa versa
improper techniue for the tue distance
Contrast on film occurs between structures of different ___________
densities
Contrast is due to the type of thickness of tissue absorbing the rays differently, this is called
differential absorption
bone __________ all or most rays leaving a white shadow on the film
a. absorbs
b. reflects
a
Water structures absorb fewer rays leaving what kind of shadow?
gray
how is the appearance of fat on a x-ray?
little absorption leaves a dark gray
what is the appearance of air on an x-ray?
black
What are the four different densities in the body?
air, oil, water, calcium
the greater the thickness of the structure the __________ the density
greater
a thick structure on an x-ray will appear _________ than a thin one
a. lighter
b. darker
a
t/f
The thicker structure will reflect more rays than a thinner
false, it will absorb
What radiographic technique should be avoided?
variable kV
What technique would the mAs stay constant but the kVp will vary?
variable kV
What are the three types of radiographic techniques?
variable kV
Fixed KV
High KV technique
For variable kV a large person would need a ________ kV
a. high
b. low
high, a thin person would need a low
is there more or less scatter with large bodies and high kV?
more
which radiographic technique is mostly used today?
Fixed kV technique
mAs is varied for the thickness in what kind of radiographic technique?
fixed kV technique
contrast shoudl be consistent in what radiographic technique?
Fixed KV technique
what radiographic technique is not for bone films?
high kV techniue
What are the settings for an x-ray?
automatic exposure control technique chart slide rule calculator Anatomical programmed chips variation from the chart recommended optimal kV ranges
what setting would be used if the exposure is made by photocells behind the patient?
When is exposure terminated?
automatic exposure control
when desired density is reached
what setting is pre-set by the operator and proper patient positioning is critical?
automatic exposure control
t/f
Technique charts are precise
false they are estimates
how should you get your technique chart?
with your unit
how are technique charts listed?
how are they measured?
list the body part and view
in cm, some parts may have a S,M, and L designation used for extremities and ribs
t/f
technique charts usually have the recommended kV, mA, tie and mAs
true
t/f
the technique chart will not need modifications
false
why do technique charts sometimes need modifications?
due to variance of machines and electrical output
the film screen, grid type, generator, patient age, habitus and some disease processes play a part too
What is the rule of thumb for technique charts?
if using high frequency with a chart made for single cut the mAs in half
What device is known as supertech?
slide rule calculator
What setting has a chip installed in the console with desired techniques?
What does the chip do?
anatomical programmed chips
allows selection of a preferred radiographic technique by measurement of a part
how does an anatomical programmed chip work?
the part and view is selected and the cm is entered the kV and mAs are set automatically, but they can be set manually
what setting would you use for patients that are considered “non-standard?
variation from the charts
a patient less than age of 12 how much do you decrease the mAs?
30-50%, you would decrease it even more for infants
What should you do to the mAs for an osteoporotic patient?
decrease the mAs by 30%-50%, this would include bedridden patients
What should be done to mAs for an obese patient?
increase the mAs 30-50%
what would you do to the mAs for excessively muscular and big boned patients?
increase the mAs by 50%
What will staying in the optimal kV range do?
assures good contrast with minimum of patient exposure
t/f
film density is varied with mAs when the optimal range is used
true
it is more difficult to see _______ when films are too dark or too light
detail
it is difficult to see detail on films with too much ___________
grain
What are some reasons it may be difficult to see detail on screens?
too fast of screens too high of kV and low mAs dirty or poorly cleaned screens screens cleaned with harsh substances old deteriorated screens
the ability to visualize small structures clearly
detail
What details should be able to be seen?
clarity of internal and external margins of a structure
lack of clarity =
poor detail
good clarity =
good detail
the edges of a structure will be unclear
unsharpness
if their is no unsharpness there is what?
a good recorded detail
unsharpness is called
penumbra
sharpness is called
umbra
what are the three things that cause unsharpness?
geometric unsharpness
screen unsharpness
motion unsharpness
What is the term of sharpness that relates to the distance between the focal spot and object?
geometric unsharpness
What will a decrease in the SID do to the geometric unsharpness?
increases it
What will an increase in SID do to sharpness?
increases sharpness
What does an increase in the object film distance do to the
increases geometric unsharpness
What does an increase in object film distance do to the sharpness of an image?
increase it
What does a small focal spot do to sharpness?
increases geometric sharpness
What does a large focal spot do to the geometric unsharpness?
increases unsharpness
What are three things that you could do to decrease geometric unsharpness?
use a short of an object film density
use as long of a SID
use a small focal spot
is there less clarity when using a single screen or no screen
a single screen
Which has less clarity a single screen or a double screen?
a double screen
do high or low speed screen have less clarity?
high speed screens
In order to reduce screen unsarpness and maintain low patient exposure what should you do?
use 400 speed rare earth screens
maintain good film/screen contact - if they are warped or damaged they should be replaced.
What is the most common cause of image blur?
a. Geometric unsharpness
b. Screen unsharpness
c. motion unsharpness
c
What are some things that can be done in order to limit patient motion unsharpness?
use short exposure time
instruct patient not to move
have patient hold breath for longer exposures
what are the two things that can contribute to motion unsharpness?
patient motion and equipment motion
What are some stabilizing devices that can be used to reduce patient motion?
patient is more stable when against with the grid cabinet radiographic table head clams radiographic sponges someone holding the patient
What are some things that can cause equipment motion unsharpness?
faulty locks for the tube
faulty grid cabinet locks on upright equipment
unstable cassette holder or frame
how do you avoid equipment motion unsharpness?
check equipment
blurring from motion is almost always due to what?
patient moving
What is the grid range?
40”-72”
What is the interspacing material for grids?
aluminum
When should you use a grid?
a. when the part is over
b. when the kV is more than
c. are there any exceptions
a. 10-15 cm
b. 70
c. some exceptions in the cerv. spine
