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Rad Positioning I > Chapter 1 (pages 38-47) > Flashcards

Chapter 1 (pages 38-47) Flashcards

1
Q

When making an image, exposure factors must be picked with what variables?

A

Density of part/anatomic number
Thickness of the anatomical part
Pathology
Technology being used

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2
Q

What are technique factors?

A

kVp and mA

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3
Q

Image Quality Factors (analog)

A

Density
Contrast
Spatial Resolution
Distortion

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4
Q

What is the primary controlling factor for RE?

A

mAs

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5
Q

What is the secondary controlling factor for RE?

A

SID

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5
Q

Relationship between RE and mAs

A

Direct Proportional

If you double the mAs, you double the amount of x-rays

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5
Q

Other factors that affect the RE (analong)

A

kV, part thickness, chemical time, chemical temp, grid ratios, and film screen speed

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6
Q

What is the Anode Heel Effect?

A

Cathode side of the tube has more xrays being projected than the anode side, so the thicker side of the patient should go to the cathode side

FATCAT - fat side to cathode

Diaphragm is the thickest part of the abdomen

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7
Q

What are examples of compenstating filters?

A

Boomerang (shoulder)
Ferlic filter (hips)
Wedge filters (chest, foot)

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8
Q

What does a compensating filter do?

A

Filters out a portion of the primary beam toward the thin or less dense part of the body

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9
Q

What causes an image to be underexposed and what will it look like?

A

Too little mAs - image will be very light

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10
Q

What causes an image to be overexposed and what will it look like?

A

Too much mAs, image will be very dark

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11
Q

What is contrast?

A

The difference in receptor exposure between adjacent areas

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12
Q

What does long gray scale contrast look like?

A

Many, many shades of grey - hard to tell the difference between them (think of a paint strip)

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13
Q

What does low contrast look like?

A

a large amount of adjacent grays. Difficult to tell the difference from one gray to the next. Needs a kVp # like 110

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14
Q

In productions, what is the main controlling factor for contrast?

A

kVp

Digital images use kVp and LUT (look up tables)

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15
Q

A high kVp will give what type of contrast?

A

Low contrast image - more gray colors

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16
Q

A low kVp will give what type of contrast?

A

High contrast - more black and white

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17
Q

What is the relationship between kVp and receptor exposure?

A

Direct - as you increase kVp, RE increases

18
Q

4 causes of grid cutoff

A

Off center - the center of your IR must be the same as the center of your focused grid

Off level - means your central ray is not at a good 90 degrees to the center of the grid

Off focus - this has to do with distance. Some grids only work for certain distances

Upside down focus - x-rays must be going in the same direction as the grid lines

19
Q

What is grid frequency?

A

The number of lead strips per inch or centimeter

20
Q

What is spatial resolution?

A

defined as the recorded sharpness of structures on an image

21
Q

Geometric controlling factors for spatial resolution (analog)

A

Focal spot size, SID and OID

A small focal spot results in less penumbra

The higher the SID, the better the spacial resolution

As OID decreases, spatial resolution increases

22
Q

What is motion on an image?

A

Blurring effect

Can be voluntary or involuntary

23
Q

What is the best way to control motion?

A

Short exposure time
Communication to the patient
Patient immobilization and controlled breathing

24
Q

What is distortion?

A

A misrepresentation of an object shape or size

25
Q

What has the least amount of beam divergence?

A

Central ray

26
Q

What are the 4 controlling factors of distortion?

A

SID - magnfication
OID - magnification
Object-image alignment - foreshortening
CR alignment - elongated

27
Q

What are the 5 different tissue types from least dense to most

A

Air
Fat
Water
Muscle
Bone

27
Q

Current technology has a broader:

A

Exposure latitude (can edit pictures now that they are digital)

28
Q

What is short gray scale contrast?

A

Looks like very few shades of white, black, and gray

29
Q

What is high subject contrast?

A

A certain black and white look of an image.

30
Q

What is the kVp range for all body parts?

A

60-120. 130 will degrade the image

31
Q

What is foreshortening?

A

The object is not lined up correctly with the IR. Incorrect placement causes the object to look smaller.

Ex. both joints of long bones need to be on IR.

32
Q

How does central ray alignment affect distortion?

A

Central ray must be aligned with the object. The more beam divergance, the more distortion. Body part will look elongated

33
Q

Types of distortion

A

Magnification
Elongation
Foreshortening

34
Q

Another word for distortion?

A

Misrepresentation

35
Q

How much does SID need to increase for every 1” of OID

A

By a factor of 7

36
Q

How to fix grays when RE is optimal?

A

15% rule

37
Q

How to fix overpenetrated and overexposed

A

Decrease kVp

38
Q

How to fix underpenetrated and underexposed

A

Increase kVp

39
Q

How to fix overexposure or underexposure

A

Double or half mAs

40
Q

What is Air Gap Technique theory?

A

Increasing OID, reduces scatter - no need for a grid

41
Q

A 40” SID is how many cm?

A

100 cm

42
Q

What is needed in the filament cup to burn off electrons?

A

mA and current

Rad Positioning I (33 decks)

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