Beam Restriciting devices

Question 1

Why do we need to employ restricting devices?

Answer 1

1. to reduce patient dose
2. reduce scatter radiation
3. achieve optimal radiographs within reasonable KVP and mAs ranges

Question 2

What are the two principle factors that the amount of scatter produced?

Answer 2

1. patient size

2. field size

Question 3

As field size increases, so does__________

Answer 3

scatter radiaton

Question 4

Reducing the beam, reduces scatter which also results:

Answer 4

in lower optical density, occasionally technical factors must be increased

Question 5

Limit the size of the x-ray field to only anatomic structure of interest

Answer 5

beam restrictors

Question 6

Reason for beam restrictors

Answer 6

1. only the tissue being examined should be exposed

2. larger x-ray fields increasing patient exposure, scatter radiation and reduce image contrast

Question 7

what are types of beam restricting devices?

Answer 7

Aperature diaphragm
cones and cylinders
variable aperature diaphragm

Question 8

Aperture diaphragm is

Answer 8

-lead lined metal diaphragm attached to the x-ray tube head

Question 9

Aperture diaphragm projects the image:

Answer 9

1 cm smaller on all side that the size of the image receptor, leaving a border around edges of the exposed film

Question 10

Cones and cylinders are:

Answer 10

extended metal structure that restrict the beam to the required field size

Question 11

Cones & cylinders are appropriate for

Answer 11

skull and sinus work

Question 12

Cones & cylinders improve

Answer 12

image contrast

Question 13

Most common beam restricting device

Answer 13

variable - aperture collimator

Question 14

variable - aperture collimator restricts:

Answer 14

patient dose by restriction the volume of tissue irradiated, and decreasing scatter radiation

Question 15

Positive beam limitation (PBL) mandiated in _____ and removed in _____

Answer 15

1974;1994

Question 16

Penumbra

Answer 16

• Fuzzy border; image blur that results from the size of the focal spot; geometric artificially

Question 17

How can penumbra be minimized

Answer 17

by using correct SID

Question 18

Off focus radiation absorbed by

Answer 18

the collimator shutters made of @ 3mm lead

Question 19

Off focus radiation increases

Answer 19

image blur

Question 20

Off focus radiation definition

Answer 20

the xrays that are produced when the projectile electrons stray and interact at positions on the anode other than the focal spot

Question 21

Reduce penumbra along the periphery of the beam due to greater distance fomr the focal spot

Answer 21

bottom shutters

Question 22

Reduce the amount of off-focus radiation reaching the film by absorbing this radiation before it exits the tube

Answer 22

Upper shutters

Question 23

The light field is provided by mounting on the path of the x-ray beam at a

Answer 23

40-45 degree angle

Question 24

Light field

Answer 24

• The light field is provided by mounting on the path of the x-ray beam at a 40-45 degree angle
• A light source is placed opposite the mirror and the light is projected through the collimator
• the light source and x-ray source should be equidistant from each other to ensure their light fields are the same size

Question 25

lead blocker

Answer 25

• lead-impregnated rubber that into various sizes and shapes

- absorbs scatter radiation

Question 26

Lead masks

Answer 26

lead that is cut to a particular size or shape for a specific patient and exam
-cerebral angiograms, radiation therapy