Radiographic Technique Flashcards
Associated with penetration and quality of x-rays
kVp
Controls image contrast
kVp
Associated with quantity of x-rays
mAs
Controls density of radiographic image
mAs
Responsible for patient exposure
mAs
3 primary exposure factors
kVp, mA, exposure time
Higher kVp = [higher/lower] contrast
Lower
Increasing kVp 15% has the same effect as ___ your mAs
doubling
Measures mAs to SID ratio (exposure maintenance formula)
Direct Square Law
3 types of filtration:
inherent, added, compensating
Affects sharpness of image/spatial resolution
focal spot size
As focal spot size increases, unsharpness [increases/decreases] and spatial resolution [increases/decreases]
increases; decreases
As focal spot size decreases, unsharpness [increases/decreases] and spatial resolution [increases/decreases]
decreases; increases
Most common technique chart
fixed kVp, variable mAs
Controls exposure time
AEC
Two types of radiation measuring devices
Phototimers, ionization chamber
Once a predetermined amount of radiation is transmitted through a patient to the AEC detector, which of the following occurs?
The x-ray exposure terminates.
Which automatic exposure device works by using a gas-filled chamber?
Ionization chamber
Which automatic exposure device works by converting x-ray photons first into light and then into an electronic signal?
Phototimer
Which exposure variable is controlled by the automatic exposure control device?
Seconds
When using AEC, what should the radiographer adjust to manipulate the subject contrast of the image?
kVp
What is the purpose of setting a backup time/mAs?
To prevent excessive exposure of the patient
Which of the following is a system that allows the radiographer to select a specific button on the control panel that represents an anatomic area and displays a preprogrammed set of exposure factors?
Anatomically programmed technique
In order to become familiar with manual technical factors (i.e., setting mAs and kVp and not using AEC), it is very helpful to pay attention to the:
mAs readout
Ensures consistent image quality and to reduce the repeat imaging because of technique error and, in turn, reduce the patient exposure
technique chart
When using a fixed kVp-variable mAs technique chart, if part thickness increases by 5 cm, what needs to happen to the mAs?
It should be doubled
As mAs increases, the quantity of radiation reaching the IR:
Increases
Which of the following technical factors affects the exposure to the IR by altering the amount and penetrating ability of the x-ray beam?
kVp
In order to reduce patient exposure, what exposure factors should be considered?
higher kVp, lower mAs
For every _____ of part thickness, the radiographer should adjust the mAs by a factor of two.
4 to 5 cm
T/F: Changes in kVp do not affect the exposure indicator value.
False
As mAs increases, the quantity of radiation reaching the IR:
increases
In order to reduce patient exposure, what exposure factors should be considered?
high kVp, low mAs
How much change in kVp will change the radiation exposure to the IR by a factor of 2?
15%
Where is the radiographic grid located?
Between the patient and the IR
T/F: Changes in kVp do not affect the exposure indicator number
False
T/F: The same mAs and kVp should be used on an AP lumbar spine and a lateral lumbar spine radiograph
False
What will limit the volume of tissue irradiated?
Cone and collimator
Which grid design is manufactured to match the divergence of the x-ray beam
Focused grid
Once a predetermined amount of radiation reaches the AEC detector, what occurs?
The exposure is stoppped
When using AEC, what should the technologist use to adjust subject contrast on the image?
kVp
A common cause for repeating images done with AEC is innacurate:
centering
Accurate patient measurement is most critical with which chart?
variable kVp, fixed mAs
T/F: AEC can be used with tabletop exams
False
T/F: Technique charts are not needed if using AEC
False
AEC devices work by measuring:
radiation that exits the patient
How many detectors are typically found in an AEC system?
3
Ionization chamber systems measure radiation [before/after] it interacts with the IR.
before
The purpose of a backup timer is to:
limit unnecessary x-ray exposure
What detector(s) should be selected for a right AP shoulder when the patient is supine on the x-ray table?
Center detector only
The purpose of anatomically programmed techniques is to:
present the radiographer with a preselected set of exposure factors
When using AEC with digital imaging systems, assuming all other factors are correct, selecting the center detector on a PA chest image results in:
increased exposure in the lung area
The exposure indicator value reflects excessive exposure to the IR. Which of the following is the best for correcting the exposure error?
Decrease mAs by 50%
What exposure factor affects both the quality and the quantity of the x-ray beam?
kVp
Which of the following is not affected by kilovoltage?
Spatial resolution
Increasing the mAs has __________ effect on brightness displayed in digital imaging.
No
Which of the following would maintain radiation exposure to the IR when the kilovoltage is decreased by 15%?
Double the mAs
What exposure factor change is recommended to maintain radiation exposure to the IR when increasing the patient thickness by 5 cm?
Double the mAs
T/F: An additive pathological disease may require less kVp to maintain adequate exposure to the IR
False
T/F: When exposure factors are selected using anatomically programmed technique, the variables should not be adjusted.
False
Generally speaking, patient dose will be decreased with the ____ kVp -____ mAs chart
fixed; variable
Accurate patient measurement is most critical for the ____ kVp -____ mAs chart
variable; fixed
What is the purpose of a technique chart?
to ensure consistent image quality and to reduce the repeat imaging because of technique error and, in turn, reduce the patient exposure
Exposure time will ______ when using AEC when patient thickness decreases.
decrease
If the backup time/mAs is automatically set by the x-ray unit, the exposure should end when a maximum of _________ has been reached.
600 mAs
The product of milliamperage and exposure time is ______ proportional to the quantity of x-rays produced
directly
The original technique is 50 mA at 0.20 s. Which of the following exposure techniques will maintain the same exposure to the IR?
a. 100 mA at 0.10 s and 400 mA at 25 ms
b. 100 mA at 0.10 s and 200 mA at 0.05 s
c. 200 mA at 0.05 s and 400 mA at 25 ms
d. All options are correct
D
The numerical value that is displayed on the processed image to indicate the level of x-ray exposure received on the digital image receptor is the___________
exposure indicator
If lower than needed kVp is selected, the digital image will have:
a. higher subject contrast and decreased brightness
b. decreased brightness and increased quantum noise
c. all options are correct
d. higher subject contrast and increased quantum noise
D
Decreasing collimation results in:
a. lower image contrast and increased patient exposure
b. increased fog and increased patient exposure
c. all options are correct
d. increased fog and lower image contrast
C
T/F: Negative contrast agents increase the attenuation of the x-ray beam.
False
The detectors selected for an image should be:
the ones that are superimposed by the anatomic structure of interest
Using a higher kVp during an AEC examination results in:
A shorter exposure time
T/F: Using the plus or minus density controls should be done frequently to produce optimal images with AEC
False
