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D2: 621 Radiology > Principles of Radiology > Flashcards

Principles of Radiology Flashcards

1
Q

Can xrays be focused on a single point?

A

No

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2
Q

What property of an xray allows it to penetrate

A

Short wavelength

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3
Q

What produces an x ray?

A

Two electrodes in a glass vaccum tube

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4
Q

Which is the positive Electrode?

A

Anode, the TARGET of negative electrons

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5
Q

Which is the negative Electrode?

A

Cathode, the expeller of negative electrons

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6
Q

What does the cathode consist of

A

Tungsten filament wound in molybdenum cup

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7
Q

How does the cathode make electrons?

A

When the tungsten is heated it boils off electrons

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8
Q

What is the process of “boiling off” electrons that the cathode goes through when heated?

A

Thermionic emission

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9
Q

What is the anode made of

A

Copper for heat conduction and tungsten to produce radiation

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10
Q

What percent of the xray kinetic energy produced by the cathode is turned into heat?

A

99%

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11
Q

What are the 3 ways an x ray can interact with a patient?

A

Scattered
Absorbed
Transmitted

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12
Q

Why are scattered x rays bad?

A

They produce fog on a film

They are a source of exposure for patients

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13
Q

What happens when an x ray scatters?

A

It changes direction and has its energy lowered

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14
Q

What is another word to describe an absorbed xray?

A

Attenuated

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15
Q

What determines an xray’s absorbtion?

A

Wavelength/kilovoltage
Tissue thickness
Atomic Number
Density

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16
Q

What color does an absorbed x-ray produce on the film?

A

White

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17
Q

What measurement refers to the amount of x-rays being directed at the patient?

A

mA

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18
Q

What measurement is the penetrating power of the x-ray beam?

A

kVp

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19
Q

What is meant by the term “dead man switch”

A

It means you have to depress the button to make x-rays….you can’t leave the switch on passively

20
Q

What is the formula for the inverse square law?

A

I = 1/d^2

21
Q

What is the inverse square law?

A

The intensity of the radiation varies inversely with the square of the source-film distance

22
Q

What is SFD?

A

Source-Film Distance

23
Q

According to the inverse square law, what happens to the intensity of the beam if the SFD is doubled?

A

Intensity decreases by 4x

24
Q

Why does the intensity of the beam lessen as the SFD is increased?

A

There is more time for the x-rays to disperse which makes the beam less focused.

25
Q

What happens that causes dark/black areas to develop on image?

A

Primary photons are transmitted through the tissue and are received by the film

26
Q

Why are absorbed x-rays also called attenuated x-rays?

A

Because the intensity of the beam is reduced as it passed through tissues. Photons are absorbed by the tissue thereby removing them from the beam

27
Q

What will result in full beam attenuation

A

Metallic restorations

28
Q

What are the two most attenuating natural tissues

A

Enamel and Cortical bone

29
Q

What is the letter designating the fastest speed film?

A

F

30
Q

What determines the diagnostic quality of Radiographs

A

The balance between the visibility and sharpness of the image

31
Q

What does sharpness actually mean

A

The distinctness between all elements in the film

32
Q

what does mAs stand for?

A

Millamperage seconds

33
Q

What do the mAs of the beam control?

A

The density, increasing the mAs will increase the quantity of x-rays produced

34
Q

What is the general rule when adjusting density of the beam?

A

Increase the mAs by factors of two

35
Q

what does kVp stand for?

A

Kilovoltage Pontential

36
Q

What does the kVp of the beam control?

A

The strength and penetrating power. Increases the kVp will allow the x-rays to penetrate deeper into tissue

37
Q

What does Geometric Unsharpness mean

A

Diffusion of detail

38
Q

What is Penumbra or Edge Gradient?

A

Fuzzy margin around a structure on a radiograph

39
Q

What is Image Magnification vs. Image Shape Distortion?

A

Magnification is the equal enlargement of all parts of the radiographic image. Distortion is unequal enlargement

40
Q

Why is there magnification and/or shape distortion?

A

Because x-rays arise from a field instead of a point and they travel in diverging lines

41
Q

Which cusps are more magnified and distorted? Buccal or Lingual

A

Buccal

42
Q

What are the five keys to an accurate image?

A

Small focal spot
Source to object distance as long as possible
Object to Film distance as short as possible
Long axis of object parallel to film
Central x-ray perpendicular to film

43
Q

What size focal spot will result in a small penumbra?

A

Small

44
Q

What magnification results in less penumbra? High or Low

A

Low

45
Q

What distances should you strive for to minimize both penumbra and magnification?

A

Maximize Source to Object

Minimize Object to Film

46
Q

What steps should you take to minimize geometric distortion?

A

Keep film parallel to object

Keep film perpendicular to central x-ray

D2: 621 Radiology (16 decks)

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