Chapter 15 Flashcards
A radiographer can best minimize the amount of scatter radiation reaching the image receptor by restricting the beam.
a. True
b. False
True
The principal factors that affect the amount of scatter produced are focal spot size and the type of irradiated material.
a. True
b. False
False
When kilovoltage is increased with no other changes in technical factors, fewer scattered photons will result.
a. True
b. False
False
Scattered photons from Compton interactions are of no use in demonstrating radiographic structures of interest.
a. True
b. False
True
Image quality is improved when scatter reaching the image receptor is reduced.
a. True
b. False
True
Bone absorbs more radiation and produces more scatter than soft tissue.
a. True
b. False
False
Soft tissue absorbs more radiation and produces more scatter than bone.
a. True
b. False
False
Penumbra is a geometric unsharpness around the periphery of an image.
a. True
b. False
True
Automatic collimators are known as positive beam limitation (PBL) devices.
a. True
b. False
True
PBLs may also filter the x-ray beam.
a. True
b. False
True
Lead masks may serve as beam restrictors.
a. True
b. False
True
Scatter radiation in radiography is produced during
a. Compton interactions.
b. photoelectric effect interactions.
c. coherent or classical interactions.
d. an annihilation interaction.
Compton interactions
Scattered photons will
a. impair image quality.
b. add to image receptor exposure.
c. not be considered part of the useful beam.
d. all of the above.
All of the above
A radiographer can best reduce the amount of scatter radiation from reaching the receptor by
a. collimating.
b. beam restriction.
c. utilizing a grid.
d. all of the above.
all of the above
Which of the following is placed between the patient and the image receptor to absorb scatter radiation?
a. radiographic grid
b. AEC detector
c. collimator
d. cylinder
radiographic grid
A key factor that affects the amount of scatter produced is
a. kilovoltage.
b. milliamperage.
c. time.
d. anode composition.
kilovoltage
A factor that affects the amount of scatter produced is
a. the irradiated material.
b. milliamperage.
c. time.
d. anode composition.
the irradiated material
As the kilovoltage increases, the percentage of x-rays that undergo ____ interactions will increase.
a. photoelectric
b. coherent
c. Compton
d. Bremsstrahlung
Compton
As the kilovoltage increases, the percentage of photons that undergo a ____ interaction will decrease.
a. photoelectric
b. coherent
c. Compton
d. characteristic
photoelectric
If an increase in kilovoltage is accompanied by a reduction in mAs, to maintain the same exit dose the overall result will be
a. a decrease in the amount of radiation produced.
b. a decrease in the amount of scatter produced.
c. an increase in the amount of radiation produced.
d. an increase in the amount of scatter produced.
a decrease in the amount of scatter produced
As more photons pass through the irradiated material unattenuated, the resulting image receptor exposure will
a. demonstrate greater image distortion.
b. be unchanged.
c. increase.
d. decrease.
increase
When more photons are absorbed photoelectrically, the image receptor will
a. receive increased exposure due to the increase in secondary radiation production.
b. increase its sensitivity automatically.
c. not operate due to lack of photons.
d. receive less exposure.
receive less exposure
As the volume of irradiated tissue ____, the amount of scatter produced ____.
a. increases; increases
b. increases; decreases
c. decreases; increases
d. decreases; decreases
increases; increases
The volume of the irradiated tissue increases as
a. field size and patient thickness increase.
b. patient density increases.
c. patient orientation to the beam changes.
d. tissue composition increases.
field size and patient thickness increase
The ____ the atomic number of the irradiated material, the ____ the number of photoelectric absorption interactions that occur.
a. higher; lower
b. higher; higher
c. lower; higher
d. lower; unaffected
higher; higher
The ____ the atomic number of the irradiated material, the ____ the number of photoelectric absorption interactions will be, and the ____ the scatter produced.
a. higher; lower; less
b. higher; higher; less
c. lower; higher; more
d. lower; lower; less
higher; higher; less
When a beam-restricting device is used to limit field size, technical factors may need to ____ to compensate for the change in image receptor exposure.
a. be increased
b. be decreased
c. remain unchanged
d. none of the above
be increased
All of the following are considered beam-restricting devices EXCEPT
a. aperture diaphragm.
b. beam filter.
c. positive beam limitation (PBL) device.
d. collimator.
beam filter
Penumbra is ____ when the beam restrictor is at a/an ____ distance from the port.
a. reduced; increased
b. reduced; decreased
c. unchanged; increased
d. increased; increased
reduced; increased
An effective method for reducing scatter radiation production is the
a. 15% rule of kVp change.
b. use of x-ray beam angulation.
c. use of an increased exposure time with mA compensation.
d. selection of small focal spot.
15% rule of kVp change
Cones and cylinders would be commonly employed for the following examinations EXCEPT
a. orbits.
b. L5-S1 spot.
c. skull.
d. AP thoracic spine.
AP thoracic spine
The shutters of a collimator
a. regulate field size.
b. reduce penumbra.
c. reduce stem radiation.
d. all of the above.
All of the above
All of the following are true of positive beam limitation (PBL) EXCEPT:
a. PBL automatically collimates the beam.
b. PBL senses the size and orientation of the receptor.
c. PBL is possible with portable radiography.
d. PBL may be overridden by the radiographer in select instances.
PBL is possible with portable radiography
When collimating down from a 14”x17” field size to a 8”x10” field size,
a. mAs must be increased to maintain image receptor exposure.
b. kVp must be increased to maintain image quality.
c. off-focus radiation production is increased.
d. the mAs should be reduced by 50 percent.
mAs must be increased to maintain image receptor exposure
The collimation assembly of a radiographic unit
a. employs an upper and lower set of shutter blades.
b. allows the radiographer to adjust the field size in a circular dimension.
c. removes the mirror assembly for exposures.
d. all of the above.
employs an upper and lower set of shutter blades
Placing a lead blocker adjacent to an obese patient’s anatomy during a lateral lumbar spine radiograph
a. is unnecessary with today’s digital receptors.
b. will improve image quality.
c. will reduce exposure to the patient.
d. will reduce exposure to the radiographer.
will improve image quality
