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RADT 3000 IPE > Beam Restriction (collimator) > Flashcards

Beam Restriction (collimator) Flashcards

1
Q

Collimation ____________ image quality

A

Increases

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2
Q

Collimation ____________ patient dose

A

Reduces

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3
Q

Collimation decreases __________, ___________, ____________,and _______ creating more black and white increasing ____________

A

Density, scatter, fog, and noise

Contrast

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4
Q

When collimating never exceed the _______ of the image receptor.

A

Size

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5
Q

Collimation

A

Controls the size and shape of the primary beam, minimizes amount of scatter radiation reaching the film and patient, absorbs off focus radiation

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6
Q

As kVp increases scatter __________

A

Increases

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7
Q

As kVp increases patient dose _________, because….

A

Decreases ; the photons pass through the patient

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8
Q

Scatter is produced in the __________ by the ___________ __________.

A

Patient ; Compton effect

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9
Q

Irradiated material

A

The volume and atomic number of the material being irradiated

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10
Q

As volume increases scatter ___________

A

Increases

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11
Q

If you decrease the tissue exposed you will __________ scatter produced

A

Decrease

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12
Q

As the field size increases, scatter ___________ therefore: you should ___________

A

Increases ; collimate

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13
Q

Increase collimation equals __________ scatter

A

Decreased

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14
Q

Increased collimation equals a ____________ in contrast

A

Increase

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15
Q

Increased collimation equals a ____________ in Compton

A

Decrease

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16
Q

Increased collimation equals a ____________ in density film/screen

A

Decrease

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17
Q

Increased collimation equals a ____________ in quantum mottle with digital

A

Increase

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18
Q

Increased collimation equals a ___________ in technical factors

A

Increase

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19
Q

Increased collimation does not effect:

A

Detail, distortion, or magnification

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20
Q

What are the three types of beam restrictors?

A

Aperture diaphragm, cones/cylinders, collimators

21
Q

Aperture diaphragm

A

Flat sheet of metal, usually lead, with opening in the center
Simple and inexpensive
Use different diaphragms for different film size

22
Q

What are three disadvantages of the aperature diaphragm?

A

Increased penumbra, increase in off-focus radiation, and a Fixed field size

23
Q

In the aperature diaphragm, the closer the diaphragm is to the patient the less ___________

A

Penumbra

24
Q

What is an aperature diaphragm used in?

A

Chest units, head units, dental, and mammo

25
Q

For an aperature diaphragm, how do you calculate the size of the circle it will produce on the IR?

A

SID X Diameter of the diaphragm / Distance from focal spot to diaphragm
Example: 40” X 2” = 80
80/ 5” = 16” circle

26
Q

Cones/ Cylinders

A

Circular aperature diaphragm with metal extension attached to housing
Simple inexpensive

27
Q

Disadvantages of cone/cylinders

A

Can be heavy and fixed field size

28
Q

Cylinders can be good in reducing ___________ and ________ _________.

A

Penumbra ; off-focus radiation

29
Q

Cones/ cylinders have greater beam limitation when the cone is ___________ and the diameter is ____________.

A

Longer ; Smaller

30
Q

For a cone/cylinder, how do you calculate the size of the circle it will produce on the IR?

A

SID X lower Diameter of the cone / Distance from focal spot to cone bottom
Example: 40” X 3” = 120”
120” / 16” = 7.5” circle

31
Q

When you make the cone longer you will have a ___________ coverage.

A

Smaller

32
Q

Collimator

A 
2 sets of lead shutters at right angles to one another ( 1 is for off focus radiation and 1 if for beam restriction)
Most common used 
Expensive 
Field sixes vary
Light source
33
Q

Collimation must be accurate within ______% of the SID

A

2%

34
Q

Between 1974-1993 the federal law required fixed machines to be equipped with __________ ___________ _________ that works on sensors.

A

Positive Beam Limitation (PBL)

35
Q

The bottom shutters of the collimators reduce __________.

A

Penumbra

36
Q

Accuracy of the collimators are check regularly. True or False?

A

True

37
Q

Collimators provide up to _____mm of added filtration.

A

1

38
Q

Disadvantages of collimators

A

Cost, maintenance, and over collimation

39
Q

Always allow _____” of light beyond each edge of anatomy.

A

1/2”

40
Q

For collimators, as distance increases the size of the field _________.

A

Increases

41
Q

2 ancillary devices

A

Lead blockers and lead masks

42
Q

Lead blockers

A

Sheat of lead rubber

43
Q

Lead masks

A

Cut to correspond to field size

44
Q

What do ancillary devices do?

A

Absorb scatter

45
Q

Increased field size = _________ scatter

A

Increased

46
Q

Increased kVp = _________ scatter

A

Increased

47
Q

We should collimate to ________ scatter and patient dose

A

Reduce

48
Q

Increased collimation = ________ patient dose, _________ scatter, and ________ quantum noise.

A

Decreased patient dose
Decreased scatter
Increased quantum noise

49
Q

Flat panel detectors are _______ size. Therefore it is very critical for a radiographer to __________.

A

One ; collimate

RADT 3000 IPE (8 decks)

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