7. Beam Restriction

Question 1

is produced during Compton interaction

Answer 1

Scatter radiation

Question 2

Beam-Restricting Devices

Answer 2

Aperture Diaphragm,
Cones or Cylinders,
Variable aperture collimator

Question 3

This can be accomplished by restricting the x-ray beam and by using a grid.

Answer 3

Reducing scatter

Question 4

As the beam is _____, fewer primary photons are emitted from the tube and collimator and fewer
scattered photons are created

Answer 4

restricted

Question 5

The principal factors that affect the amount of scatter produced are:

Answer 5

kilovoltage and irradiated material

Question 6

As kVp _____, fewer photons undergo interaction with matter and more pass through the patient to interact with the image receptor

Answer 6

increases

Question 7

As kilovoltage increases, the percentage of x-rays that undergo Compton interaction _____ and the percentage of photons that undergo photoelectric
absorption ______

Answer 7

increases,

decreases

Question 8

If kVp is increased with no other change in the technical factors selected for a given exposure, the end result will be an ______ in the transmission of photons & therefore an ______ in the exit dose

Answer 8

increase,

increase

Question 9

In radiography, the ______ is selected based predominantly on the size of the part being examined
and the radiographic contrast desired for the image

Answer 9

kilovoltage level

Question 10

Increase kVp and reduce mAs to maintain the same exit dose, the overall result will be a ______ in the amount of exposure produced

Answer 10

decrease

Question 11

The amount of scatter created during an interaction is
affected by the ______ and ______ of the
material being irradiated

Answer 11

volume,

atomic number

Question 12

The volume of irradiated material is controlled by ____ and

Answer 12

field size,

patient thickness

Question 13

As the volume of irradiated tissue ______, the amount of scatter ______

Answer 13

increases,

increases

Question 14

Volume ______ as the field size increases or as the patient thickness increases

Answer 14

increases,

Question 15

The atomic number of the irradiated material also has
an impact on the amount of scatter produced because _____ atomic number materials have a greater number
of electrons within each atom and photons have a
greater chance of striking an electron creating an
absorption interaction.

Answer 15

higher

Question 16

High atomic number materials (iodine, barium, lead)
absorb ______ radiation through photoelectric interaction
than low atomic number materials do

Answer 16

more

Question 17

Of the factors affecting the amount of scatter produced,

the _____ and the _____ are under the direct control of the radiographer

Answer 17

kilovoltage,

field size

Question 18

When the beam is ______, less scatter radiation will
reach the image receptor and as a result, technical
factors may need to be increased to compensate for the
reduction in the overall image receptor exposure.

Answer 18

restricted

Question 19

Is a flat sheet of metal, usually
lead, with a hole cut in the center and attached to am
xray tube port

Answer 19

Aperture Diaphragm

Question 20

depends on the desired exposure field, the source to image receptor distance (SID), and
the distance from the aperture to the focal spot.

Answer 20

The size of the opening

Question 21

Aperture Diaphragm

Principal disadvantage:

Answer 21

Increase in penumbra

Question 22

geometric unsharpness around the periphery of the image

Answer 22

penumbra

Question 23

is the result of x-ray photons being created
in all areas of the focal spot rather than at just a single
point.

Answer 23

Penumbra

Question 24

While the use of different types of restrictors does not alter the sharpness of the internal image details, the ______ the beam restrictor is from the port, the ______
the edges of the exposed area will be

Answer 24

farther,

sharper

Question 25

To avoid exposing an area larger than necessary, | selection of the correct diaphragm and proper SID is

Answer 25

critical

Question 26

are essentially circular aperture | diaphragms with metal extensions

Answer 26

Cones/Cylinders

Question 27

has extension which flares or diverges with the | upper diameter smaller than the bottom flared end

Answer 27

Cone

Question 28

does not flare and has the same diameter at | the bottom of the extension as it has at the top

Answer 28

Cylinder

Question 29

May be equipped with an extension sleeve which can expand or collapse to vary the degree of beam restriction.

Answer 29

Cylinder

Question 30

Most commonly employed in radiography of the skull, | spine, gallbladder and breast

Answer 30

Cylinder

Question 31

The _______ of a cone sometimes makes it difficult to handle and when used with a horizontal beam, the weight of the cone may cause the tube to angle slightly (causes one cutting if central ray is not checked before exposure)

Answer 31

physical weight

Question 32

Unlike cones and aperture diaphragms, _____ do reduce penumbra and off-focus radiation because they provide better beam restriction at a greater distance from the focal spot

Answer 32

Cylinders

Question 33

Determining the _______ – Involves a similar method to that used with an aperture diaphragm.

Answer 33

Cone field size

Question 34

most commonly employed beam | restrictor in radiography.

Answer 34

Collimator

Question 35

It consists of sets of lead shutters at right angles to one another which move in opposing pairs. Each set moves symmetrically from the center of the field

Answer 35

Collimator

Question 36

reduces penumbra along the periphery of the beam because of their greater distance from the focal spot.

Answer 36

Bottom shutters

Question 37

help in reducing the amount of off-focus (stem) radiation reaching the image receptor by absorbing this radiation before it exits the tube

Answer 37

Upper shutters

Question 38

Some units provide an outline of the _________ chambers’ size and location

Answer 38

automatic exposure control (AEC)

Question 39

AEC

Answer 39

automatic exposure control

Question 40

devices are automatic | collimators

Answer 40

Positive Beam Limitation (PBL)

Question 41

PBL

Answer 41

Positive Beam Limitation

Question 42

The use of a collimator results in some _____ of the xray beam because the primary beam is passing through the mirror in the collimator

Answer 42

filtration

Question 43

are generally designed with a special need in mind. Ex: lead blockers and lead masks.

Answer 43

Ancillary devices

Question 44

is simply a sheet of lead-impregnated | rubber that can be cut to any size or shape

Answer 44

Lead blocker

Question 45

usually is cut to correspond to the particular field size desired and is then secured to the end of the collimator

Answer 45

Lead mask