All Exams
What exposure time is needed to create 12 mAs when using a setting of 600 mA?
.02 second 12mAs/600mA= sec
100 mA x _____ second = 40 mAs 40 mAs/100 mA
.4 second
Increasing kVp will result in increased: 1. beam energy 2. IR exposure 3. photon speed
1
grid ratio: no grid- 5:1 6:1 8:1/10:1 12:1 16:1
1 2 3 4 5 6
Which of the following will result in improved image quality? increased matrix size increased bit depth increased pixel size
1 & 2
Using a grid will result in which of the following? 1. increased image quality 2.decreased scatter production 3.decreased patient dose
1 only
An increase in which of the following will increase scatter production? 1. tissue thickness 2. kVp 3. collimation
1&2
What is the purpose of a technique chart? 1. helps ensure consistent image quality 2. helps reduce repeats due to technique errors 3. reduces scatter production
1&2
increasing kvp will result in increased: 1. beam energy 2. Ir exposure 3. photo speed
1&2
Which of the following occur when the rotor (prep button) of the x-ray machine is pressed? filament begins to heat up anode begins to spin electrons move rapidly from cathode to anode
1,2
Increasing kVp will result in which of the following? higher energy photons increased scatter production more photons created
1,2 & 3
Changing from an 8:1 grid to a 12:1 grid will result in: 1. less scatter striking the IR 2. increased radiographic contrast 3. the need to increase technique
1,2&3
which of the following may result in a repeat when using AEC? 1. poor positioning 2. tube/ IR not aligned 3. incorrect cell selection
1,2&3
Using a fixed kVp technique chart, a patient measuring 20 cm requires a technique of 60 mAs @ 85 kVp. What technique would be used for a patient measuring 24 cm?
120 mAs @ 85 kVp
Changing from an 8:1 grid to a 12:1 grid will result in which of the following? 1.decreased scatter production 2. increased image contrast 3.need to increase mAs
2 & 3
Which of the following will occur if kVp is increased? tube current decreases beam quality increases beam quantity increases
2,3
Which of the following would result in quantum mottle being seen on an image? too much mAs used insufficient kVp used SID that is too long
2,3
As kvp increases, scatter production
increases
When beam quality increases, the ability for the beam to penetrate through tissue does what?
increases
as tissue volume increases, scatter production
increases
fluid filled structures (barium filled bowel)
increases exposure time
increase SID
increases exposure time
what factors decrease size distortion?
increasing SID decreasing part thickness
lead lines run parallel to one another grid covers the IR most often used in mobile radiography
parallel grid focus
The abdomen is a structure described as having low subject contrast.
true
mAs controls only the amount of x-rays produced.
true
patient pathology may alter absorption characteristics of tissue
true
true or false: Adjusting the density controls will affect exposure to the IR
true
using a grid will improve contrast & improve image quality: T/F`
true
where does this interaction occur?
tube target
gross overexposure will cause loss of contrast
unable to see structures fully
when performing a forearm study, you should :
use a manual technique and no grid
An imaging system with a high detective quantum efficiency (DQE) produces a quality image:
using lower radiation exposure
higher grid ratios
usually have higher lead content require more mAs improve image quality as compared to a low grid ratio
what type of exposure technique chart uses a set mAs for a part, regardless of thickness
variable kvp chart
any factor change that increases scatter production :
will decrease contrast
Which of the following may be manipulated to alter image contrast?
window width
A radiographer takes an image without a grid using 8 mAs and 75 kVp. If the image is repeated using a 12:1 grid what mAs is needed to maintain exposure
〖mAs〗_1 = 〖GCF〗_1 〖mAs〗_2 〖 GCF〗_2 8 = 1 x 5
The number of lead strips per inch is called:
grid frequency
What are two ways that you can double the exposure from the x-ray tube?
1. An increase in kvp by 15% 2. Double mAs
which image demonstrates the lowest bit depth? which image is made of the largest pixels?
1. image C 2. Image B
low contrast:
1. long scale 2. many shades of gray 3. wide window width 4. high kvp 5. more scatter
As grid ratio increases:
1. scatter clean up to the IR will increase 2. radiographic contrast increases 3. Technique needed increases
High contrast:
1. short scale 2. few shades of gray 3. narrow window 4. low kvp 5. less scatter
When is higher mAs required in reference to grids?
1. when going from a low grid ratio to a high grid ratio 2. going from a non grid to using a grid
As kvp increases: 1. scatter production increases 2. contrast decreases 3. IR exposure increases
1.2&3
A grid should be used whenever the anatomic part size exceeds
10cm in thickness
What is the most appropriate setting for backup time/mAs when using AEC?
150% of expected exposure time
backup time is set to
150% of expected mAs
backup time should be set by the radiographer to
150-200% of expected exposure time
200 mA x .083 second
16.6 mAs
a part measures 14cm and requires 20mAs at 75kvp, using a variable kvp tech chart, what would be used for 18cm
20 mAs @ 83 kVp
mA x .3 second = 60 mAs 60 mAs/.3 second
200mA
when using a variable mAs technique chart, how does technique change for 5cm increase in thickness
2cm per 4-5 cm
Using a grid will result in which of the following? decreased scatter production decreased patient dose increased image contrast
3 only
an image taken using 10mAs at 75kvp at 5:1 grid, what mAs would be needed if a 16:1 grid were used instead
30 mAs
An exposure of 360 mR is recorded at 40". What will exposure measure if distance is increased to 72"? I1 = 360 mR I2 = x d1= 40" d2= 72"
360/x=72^2/40^2 x = 111 mR
A person stands 3 feet from a source of radiation and receives an exposure of 160 mGy. If distance from the source is moved to 6 feet, what would exposure amount be?
40 mGy
An exposure of 20 mGy is recorded at a distance of 40". If distance is increased to 72", what will exposure measure?
6.2 mGy
Lead strips of a grid are 6.4 mm high and 0.8 mm apart. What is grid ratio? grid ratio= height of lead strips/ distance between them
6.4/.8=8:1 grid ratio
If the backup/mAs is automatically selected by the x-ray unit, exposure should end when a maximum of ______ has been reached.
600 mAs
A satisfactory image of the abdomen is taken using 20 mAs and 85 kVp at a distance of 40 inches. If distanced is increased to 72 inches, approximately what new mAs must be used to maintain exposure?
65 mAs
a patient measuring 26cm for an abdomen, requires a technique of 20 mAs at 75kvp, using a variable mAs technique chart, what technique should be used for a patient measuring 35cm
80mas 75kvp
Using a variable kVp chart, if a part measures 14 cm and requires 75 kVp, what kVp is needed for a part measuring 18 cm?
83 kVp (2 kVp per cm).
Which of the following projections utilizes distortion to better demonstrate anatomy? a.PA axial wrist, Stetcher method for the scaphoid b.PA wrist c.AP forearm d.AP abdomen
A
Which of the following will result from increasing OID? a.increased contrast b.increased resolution c.decreased magnification d.increased IR exposure
A
Converts electronic signal to a digital signal
ADC
Comparing grids of the same frequency, a higher ratio grid will clean up more scatter than one with a lower ratio. Select one: a.false b.true
B
using which of the following will reduce scatter radiation production? A. grid B. collimation C. small focal spot size D. high kvp
B
The height of lead strips in a grid divided by the distance between them is:
grid ratio
The use of a grid helps reduce scatter production. a.true b.false
B. False grids will reduce scatter production to the IR only
Increasing kVp will result in: Select one: a.decreased tube current b.increased photon speed c.increased beam penetration d.all of the above
C
Using which of the following will reduce scatter radiation production? Select one: a.high kVp b.small focal spot size c.collimation d.a grid
C
use of the airgap technique requires an increase in which of the following A. SID B. collimation C. OID D. kvp
C
Please briefly outline what happens in a CR reader once a cassette is placed in the reader.
Cassette is placed in reader, a laser beam of helium scans the plate, when scanned plate releases energy and light that was stored. Released light goes to the PMT that collects the light which then the PMT converts the light to an electrical signal the signal goes to the analog digital converter, the signal is converted to a series of numbers to the computer to an x-ray image
Which grid ratio would be best at reducing the amount of scatter striking the IR? Select one: a.6:1 b.12:1 c.8:1 d.16:1
D
Which of the following mA and exposure time combinations would result in the least chance of patient motion on the final image? a.300 mA @ .03 second b.100 mA @ .09 second c.200 mA @ .045 second d.500 mA @ .018 second
D
A grid should be used whenever an anatomic part exceeds: Select one: a.5 cm in thickness b.5 cm in length c.10 cm in length d.10 cm in thickness
D. 10cm thickness
Which of the following will occur when a stream of high speed electrons is suddenly stopped? heat is generated light is emitted electricity is generated
HEAT IS generated
what factors have no effect on spatial resolution?
grid ratio collimation mas kvp anode heel affect
Which of the following will result in elongation or foreshortening of an image? IR that is angled CR angle increased OID
IR angle CR angle
A radiograph is taken using 10 mAs @ 60 kVp. If mAs is decreased to 5 mAs, what kVp must be used to maintain exposure?
If mAs is cut by ½, kVp must be increased 15% in order to maintain exposure. 15% of 60 is 9. 60 + 9 = 69 kVp SO a technique of 5 mAs @ 69 kVp will maintain original exposure
A radiograph is produced using 25 mAs @ 75 kVp. What kVp would be needed to double exposure?
Increase kVp 15% to double exposure. 15% of 75 is 11.25 75 + 11.25 = 86.25 Therefore - 86 kVp needed to double exposure
When using automatic exposure control (AEC), the technologist CANNOT directly assign which of the following parameters?
Milliamp-seconds (mAs)
What projection should be performed to minimize magnification of a structure that is located anteriorly in the body?
PA
focused grid: lead lines angled to match divergence of beam most effective in cleaning up scatter uses focal range (SID)
Referring to the image above, what type of grid is depicted?
How is SOD determined?
SID - OID
tissue interactions
Signaling that typically occur between adjacent tissues.
what is the purpose of using a technique chart?
to reduce the chance of repeats due to poor technique selection
direct conversion DR
a:Se TFT
indirect conversion DR
a:Si scintillator TFT the scintillator converting x-rays to light & because of the amorphous silicon (a-si) is used in indirect conversion.
grids will a higher lead content have a greater selectivity, grids with higher selectivity
absorb more scatter
line focus principle
actual focal spot- where electrons bombard target effective focal spot- directly below tube A large target angle produces a large effective focal spot size A small target angle produces a small effective focal spot, a smaller effective focal spot results in improved image detail
The patient pathology that results in body tissue being harder to penetrate is referred to as what?
additive
In order for x-ray photons to be produced, electrons must: be released from the filament accelerate rapidly stop suddenly
all
Photons that make up the primary x-ray beam: can ionize body tissue have different energy levels travel at the speed of light
all of the above
Using an increased amount of OID will create an image that demonstrates what? magnification loss of detail increased contrast
all of the above
Added filtration is typically made of:
aluminum
What do exposure indicator numbers indicate?
amount of radiation striking the IR
calipers measure part thickness
an instrument used to measure distances or diameters
When an incident electron interacts with the inner shell of a target atom, the result is:
an x-ray photon
What are calipers used for?
anatomical part measurement
ionization chamber type devices are considered to be entrance type devices because they
are placed infront of the image receptor air within chamber becomes ionized creating an electrical charge
what do the boxes on an upright bucky represent?
arrangement of 3 AEC dectors on an upright bucky
identify what is wrong with this image
artifact
positive beam limitation is actually
automatic collimation
A low SNR results in an a poor quality digital image.
true
CR:
barium fluorohalide with europium separate reader system PSP PMT
What property of the x-ray beam influences the area of unsharpness around an image?
beam divergence
a phototimer AEC is an exit type device because it is placed
behind the IR radiation must exit the IR before it is measured by the detector
smaller pixels, the more pixels there is =
better resolution
where are the sensors for an ion chamber AEC unit located?
between the patient and IR
In order to work properly, where is a grid placed?
between the patient and the IR
Which of the following materials is a scintillator? a.barium fluorohalide with europium b.amorphous selenium c.cesium iodide (CsI) d.amorphous silicon
c
When performing an AP projection of the hip using AEC, what is the best cell configuration to select?
center cell
when using AEC for an AP shoulder, what detection selection is best?
center cell only
Which of the following is a target interaction which will result in x-ray production?
characteristic
Scatter radiation produced during diagnostic exams is primarily the result of what interaction?
comptom
lead lines run at right angles to eachother clean up scatter twice as effectively as linear grids
cross-hatch grid pattern
as collimation increases, contrast will
decrease
as tissue volume decreases, radiographic contrast will
decrease
what factors will decrease spatial resolution?
decrease SID (short sid) increase OID increase focal spot size increase part thickness higher the angle motion distortion
destructive diseases
decrease absorption less difficult to penetrate pneumothorax emphysema
scatter on an image will
decrease contrast
air-filled structures (bowel gas)
decrease exposure time
an increase in kvp will
decrease exposure time
increase in mA will
decrease exposure time
when using AEC, an increase in mAs will
decrease exposure time
larger pixels =
decrease in resolution
what factors increase contrast?
decrease kvp increase OID increase collimation increase grid ratio decrease part thickness size increase atomic # use of contrast material decrease window width
what factors decrease IR exposure?
decrease mAs decrease kvp increase SID decrease OID increase collimation increase grid ratio increase patient part thickness increase in filtration SID changed from 40" to 72" (but technique remains the same) mA is reduced by half. Exposure time is reduced by half.
How is exposure affected when distance from a source of radiation is doubled?
decreased by a factor of 4
When a matrix size is fixed (stays the same), what will decreasing the field of view (FOV) result in?
decreased pixel size
as collimation increases, scatter production
decreases
as kvp increases, radiographic contrast
decreases
high mA, ______________ exposure time
decreases
what factors increase size distortion?
decreasing SID increasing OID increasing part thickness
Which type of digital imaging equipment has the highest DQE?
direct conversion DR
factors that affect resolution: (2)
distance - SID/OID motion- voluntary/involuntary
____________ will result in reduce spatial resolution
distortion
an AEC system is preprogrammed to end an exposure when a certain amount of exposure has been reached, this means
equipment determines exposure time & determines total amount of mAs used in an exposure
identify what is wrong with the image
excessive collimation
visiblity
exposure contrast
when using an AEC unit, what occurs once a predetermined amount of radiation is transmitted through the patient to the detector?
exposure terminates
when using AEC, the equipment determines which of the following?
exposure time
When using an AEC device, how is exposure time affected when kVp is increased?
exposure time decreases
what would happen if AEC were use for an AP chest on a stretcher?
exposure time would be too long
AEC and APR are essentially the same thing.
false
AEC can and should be used for tabletop examinations:
false
Which tube component provides the electrons needed for x-ray production?
filament
what determines focal spot size?
filament size
IR used in DR imaging systems
flat panel detector
what factors have no effect on IR exposure?
focal spot size
what factors have no effect on distortion?
focal spot size
identify what is wrong with the image
grid artifact
parallel grid shown
grid covers the IR mobile/portable exams use this
The number of lead lines per inch or centimeter in a grid defines:
grid frequency
positive contrast material:
high atomic number barium/iodine increases absorption seen as white or bright on images requires an increase in Kvp more kvp needed for barium
positive contrast
high atomic number radiopaque barium/iodine
When looking at a digital image, what is window level used to adjust?
image brightness
when collimation increases ___________ increases
image contrast
increasing OID has what affect on image contrast?
image contrast increases
what factors increase shape distortion?
improper CR alignment part alignment IR alignment CR angle and direction
using a grid will
improve image quality increase contrast improve recorded detail
Where are the sensors (cells) located with an ionization chamber type AEC device?
in front of the IR
As grid ratio increases, radiographic contrast will:
increase
what factors will increase resolution?
increase SID decrease OID decrease focal spot size decrease part thickness decrease in magnification
Additive diseases
increase absorption more difficult to penetrate pleural effusion atelectasis
grids are used to improve contrast and absorb scatter before it hits the IR, use of a grid will also:
increase contrast improve image quality improve the ability to see recorded detail
an increase in patient thickness will
increase exposure time
increase collimation will
increase exposure time
what is the result when switching from a grid with 8:1 ratio to 12:1 grid?
increase image contrast
what factors decrease attenuation
increase in beam energy
what factors decrease contrast?
increase kvp decrease OID decrease collimation decrease grid ratio increase part thickness decrease atomic # fog increase window width
Exposure time decreases:
increase kvp increase mA
when using a kvp variable technique chart, what is the appropriate changed needed for 1 cm increase in tissue thickness?
increase kvp by 2
what factors increase IR exposure?
increase mAs increase kvp decrease SID increase OID decrease collimation decrease grid ratio decrease part thickness mAs is doubled kVp increased by 15%
higher kVp will:
increase number of compton interactions/increase scatter increase energy of scatter created
exposure time increases:
increase pt thickness increase SID
what factors increase attenuation?
increase tissue density atomic # tissue increase increase tissue thickness
A larger bit depth will result in images that display what?
increased contrast resolution
The speed of electrons moving from cathode to anode during x-ray production is controlled by:
kvp
What factor actually controls the speed of electrons moving from cathode to anode in the x-ray tube?
kvp
AEC eliminates the need for the radiographer to set the exposure time, but you must still select
kvp mA proper IR gird, if needed
performing which projection on a patient would result in the most scatter? 1. AP lumbar 2. Oblique lumbar 3. Lateral lumbar
lateral lumbar
What unit is resolution expressed in?
line pairs/mm
lead lines that run in 1 direction
linear grid pattern
negative contrast material:
low atomic number air/gas dark or black images
negative contrast
low atomic number radiolucent air/gas
The number of electrons that flow from cathode to anode during x-ray production is directly proportional to what?
mA
Which technical factor directly controls the number of x-ray photons created?
mAs
when using AEC, paying attention to the ______ __________ will help you become more familiar with the manual technique factors
mAs readout
Size distortion on an image is also known as what?
magnification
What is the formula SID/SOD used to calculate?
magnification factor
Converts x-ray photons into an electric signal Answer 2
photoconductor
Converts visible light to electric signal
photodector
Which of the following is a tissue interaction which results in the total absorption of an x-ray photon within the body?
photoelectric
converts visible light into electrical energy
photomultiplier (PM) tube photodiode (solid-state device)
Which component of a CR reader collects visible light and converts it to electrical signal?
photomultiplier tube (PMT)
Which of the following impacts contrast resolution of a digital image?
pixel bit depth
Which of the following immobilization devices requires an increase in exposure?
plaster cast
grids will:
prevent scatter from hitting the IR allow you to see detail better require more technique
AEC controls the ________________ of radiation reaching the image receptor.
quantity no effect on contrast
AEC works by measuring
radiation exiting the patient
light paddles coated with fluroscent material serve as detectors
radiation interacts with the paddles, producing visible light light is transmitted to remote PM tubes or photodiodes that convert the light to electricity
AEC operation & types of systems:
radiation through the patient converted to electrical signal exposure terminated phototimer system ionization chamber system
what is placed between the lead strips?
radiolucent
What is placed between the lead strips of a grid?
radiolucent material
what type of grid is shown? what does focal range mean
range of SID that can be used with the grid focused grid
What is the focal range of a grid?
range of SIDs that may be used with a grid
IR exposure stays the same if the mAs stays the same
reciprocity 100 mA x .1 second = 10 mAs 200 mA x .05 second = 10 mAs All above mA/time combinations = 10 mAs All should result in same amount of IR exposure
Collimation, what does the beam restriction do?
reduce amount of tissue being exposed reduce PT dose reduce scatter production increase image quality (contrast)
using good collimation will
reduce scatter production
grids will not:
reduce scatter production increase detail reduce pt dose
If you go from not using a grid to using a 16:1 grid, how are the following image quality characteristics effected? detail/spatial resolution will
remain unchanged
how is spatial resolution of an image affected when the grid ratio is increased
remains unchanged
Focal spot size is determined by the pixel and matrix size, the larger the matrix, the smaller the pixels, the overall better
resolution
decreasing kvp has what affect on scatter production
scatter decreases
Decreasing kVp used has what affect on scatter production?
scatter production decreases
Converts x-ray photons to light
scintillator
Elongation and foreshortening are examples of what?
shape distortion
Angling of the IR, body part or tube when creating an image results in which of the following?
shape distortion (elongation or foreshortening)
Accuracy
spatial resolution distortion
When pixel density increases, how is image spatial resolution affected?
spatial resolution increases
alignment and positioning
spine- center cell selected abdomen- all 3 cells selected pelvis; 2 outer cells
1. When a predetermined level of ionization is reached at an ionization chamber, what happens?
the exposure is terminated
the higher the kvp value, the shorter
the exposure time high kvp with AEC decreases the exposure time & mAs, reducing pt exposure
what is the greatest source of scatter during a radiologic exam?
the patient
higher grid ratios remove more scatter than lower grid ratios IF
they have the same frequency
Which DR system component is divided into square detector elements known as DELs?
thin-film transistor
purpose of the back up timer:
to limit unnecessary x-ray exposure
what is the purpose of setting backup timer when using AEC?
to prevent patient overexposure if the AEC fails
What is the reason for have filtration in the x-ray tube?
to reduce pt skin dose
