homework review 2 Flashcards
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
The ionization chamber contains air and, when exposed to x-radiation, creates an _______________________
electrical charge due to ionization.
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
When using AEC, what should the radiographer adjust to manipulate the subject contrast of the image?
kVp
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
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
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 (squared/increases).
increases
For every _____ of part thickness, the radiographer should adjust the mAs by a factor of two
4-5 cm
true/false:
Changes in kVp do not affect the exposure indicator value.
false
A device consisting of very thin lead strips with radiolucent interspaces intended to absorb scatter radiation emitted from the patient is a:
grid
A larger the x-ray beam field size results in
-increase in scatter
-increase in contrast
-increase in fog
increase in scatter and increase in fog
T/F: As collimation decreases, exposure to the IR increases.
true
Changing from an 8:1 grid to a 12:1 grid, along with making the appropriate adjustments, will result in:
-increased patient dose
-an image with increased contrast
-using more mAs
all of the above
T/F: Digital IRs are not sensitive to scatter radiation.
false
Grids that move during the exposure are __________ in motion and ________________
reciprocating, Potter-Bucky diaphragm
Significant collimation requires an increase of _____________ of the mAs.
30-50%
The most common cause of grid cutoff is due to:
off level misalignment
Why does the air-gap technique work?
The scatter photons are more likely to miss the image receptor
T/F:
A good alternative to collimation is electronic masking.
false
