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D2: 621 Radiology > Exam 1.4: Principles of Radiography and Definitions > Flashcards

Exam 1.4: Principles of Radiography and Definitions Flashcards

1
Q

Physical properties of x-rays

A

Weightless and undetectable by human senses

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2
Q

What is notable about how x-rays travel?

A

Travel in straight lines

Cannot be focused on a convergent point

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3
Q

What allows x-rays to penetrate our tissues?

A

Short wavelength

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4
Q

What is the difference between diagnostic and therapeutic radiation?

A

Therapeutic radiation causes a biological change

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5
Q

What is the tube made up inside the tube head?

A

Pyrex glass

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6
Q

What is inside the pyrex glass tube

A

Two electrodes

Also, no air….vacuum tube

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7
Q

What is the negative electrode called

A

Cathode

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8
Q

What is the function of the cathode?

A

It is the source of electrons

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9
Q

What is the cathode made of

A

Tungsten filament wound up inside a Molybdenum cup

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10
Q

Is the cathode stronger when it is thick or thin?

A

Thin

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11
Q

How does the cathode “release” electrons

A

The cathode has a very high melting point, when heated the electrons boil off

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12
Q

What is the name of the positive electrode?

A

Anode

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13
Q

What is the function of the anode

A

It is the target of the electrons released by cathode. It releases the radiation

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14
Q

What is the anode made from

A

copper with a tungsten target

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15
Q

What percent of the energy produced by the anode is immediately lost as heat?

A

99%

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16
Q

What happens to the x-ray’s energy when it scatters?

A

It is lowered

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17
Q

What does scatter cause in terms of image errors?

A

Fog

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18
Q

What is dangerous about scatter?

A

It is a source of patient exposure

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19
Q

What does it mean when the x-ray is attenuated?

A

It has been absorbed by the tissue

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20
Q

What values are important when trying to determine if an x-ray will be attenuated?

A

Wavelength
Tissue thickness
Atomic number
Density

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21
Q

What is removed from the beam as it passes through, and is attenuated by tissue?

A

Photons

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22
Q

What is the result of attenuation on the image?

A

Radiopacity

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23
Q

What are the two most attenuating tissues in the body?

A

Enamel and Cortical Bone

24
Q

What results in complete attenuation of x-rays?

A

Metal restorations

25
Q

In a BW, what percent of x-rays pass through the tissue completely (transmitted) without any interaction at all?

A

9%

26
Q

If you want to increase the amount of x-rays in the beam (Cross sectional Density/Flux) what adjustment would you make to the machine?

A

Increase mA

27
Q

What value dictates the penetrating power of the beam?

A

kVp

28
Q

What is the primary safety feature of well designed x-ray systems?

A

Dead man switch

29
Q

What is the inverse square law?

A

Intensity (I) = 1/d^2

30
Q

What is the general idea of the inverse square law?

A

Intensity of radiation varies inversely with the square of the Source-Film Distance

31
Q

If you increase the Source to Film distance by 2x…what is the effect on the intensity of the beam?

A

The intensity of the beam is decreased by a factor of 4

32
Q

What is the purpose of the thin lead sheet in the film?

A

Receives radiation and protects patient from scatter

33
Q

Should the raised dot face the tube or the patient?

A

tube

34
Q

What are the three types of film?

A

Periapical (#1,2)
Bitewing (#2)
Occlusal (#4)

35
Q

What is determined by the film speed?

A

The efficiency with which a film responds to x-ray exposure

36
Q

If you increase the speed of the film, how would you adjust exposure time?

A

You would decrease it

37
Q

Which speed (High or Low) requires less radiation exposure for the patient?

A

Fast

38
Q

Film speed ratings are designated by the letters of the alphabet from A-F….is F the fastest or the slowest film?

A

F for Fast

39
Q

What does the sharpness of an image refer to?

A

AKA Definition, sharp images have a clear demarcation between all elements of the film

40
Q

What are some qualities that make an image “diagnostic quality”?

A

Exactness of anatomic detail

Proper balance of visibility and sharpness of redorded detail

41
Q

What is radiographic density?

A

White areas vs Dark areas on film

42
Q

What is the controlling factor of image density?

A

mAs

milliamperage seconds

43
Q

If you increase the mAs of the machine, what is the result (in terms of the beam)

A

The beam will now include more photons

44
Q

If you are going to increase mAs, try to do it by this amount

A

2x

45
Q

What is the controlling factor of contrast?

A

kVp

46
Q

What is the kilovoltage of the beam

A

The strength (not volume/amount) of x-rays. Increased strength means increased penetration of tissue

47
Q

What characteristic describes the diffusion of detail in an image?

A

Geometric unsharpness

48
Q

What would you call a fuzzy, unsharp margin around a structure on a radiograph

A

Penumbra

49
Q

What exactly is meant by image magnification?

A

EQUAL enlargement of all parts of the image.

The shape of the magnified image is in the same proportion as the original

50
Q

How does image shape distortion differ from magnification

A

It is enlargement without keeping the enlarged image in the same proportion as the original

51
Q

If the x-rays are traveling from their source in diverging straight lines, what type of image distortion will occur?

A

Magnification

52
Q

If the x-rays originate from an area rather than a point what type of distortion will occur?

A

Geometric Unsharpness

53
Q

Why might different parts of the tooth be magnified to different extents

A

Because the teeth have depth, meaning the buccal cusps will show more magnification than the lingual cusps because they are further away from the film

54
Q

What are some keys to getting an acute image?

A 
Small focal spot
Longest source to film distance
Shortest object to film distance
Long axis parallel to film
Central Ray perpendicular to film
55
Q

What will increasing the source to object distance and minimizing the film to object distance help mitigate?

A

Penumbra and Magnification

56
Q

What will keeping the film parallel to the long axis and the central ray perpendicular to the film help mitigate?

A

Geometric Distortion

D2: 621 Radiology (16 decks)

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