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SU14 Oral Radiology > EX1; Podcast - Principles of X-Ray Production > Flashcards

EX1; Podcast - Principles of X-Ray Production Flashcards

1
Q

When is an X-ray produced

A

when highly accelerates electron are suddenly brought to a stop by hitting a stationary object

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2
Q

What specifically is converted into X-rays via the high speed electrons

A

kinetic energy

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3
Q

This mechanism for production involves electron to nucleus interaction

A

bremsstrahlung

“braking radiation”

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4
Q

What are the three requirements for x-ray production

A

electrons
high velocity (electrons)
high Z-number absorbing material/target (i.e Tungsten 74W)

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5
Q

The higher the what, the greater the kinetic energy of the electron

A

velocity

KE = 1/2mV^2

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6
Q

True or False

All the electrons move at the same velocity

A

False; some move at high velocity than others

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7
Q

What occurs when some electrons striking the nucleus suddenly stop and give off all their KE

A

a single high energy x-ray photon is produced

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8
Q

Most electrons pass close to the nucleus, decelerate and give up some of their KE and produce this

A

x-ray photons with various energies

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9
Q

This mechanism for production involves electron to electron interaction

A

characteristic radiation (K-radiation)

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10
Q

How does characteristic radiation cause ionization

A

incident electrons interact with K (or L) shell electrons of target (tungsten) atoms

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11
Q

What is the result from characteristic radiation

A

heterogenous x-ray beam but much narrower energy spectrum than Bremsstrahlung

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12
Q

What is the target/focal spot made of

A

tungsten embedded within the copper anode

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13
Q

What are the actual dimensions of the target/focal sport

A

1x3mm

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14
Q

What are the effective focal spot dimensions; it is angulated (20º) to produce a beam from a smaller area

A

1x1mm

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15
Q

Why is tungsten used as a target

A

high melting point and heat stability
high ductility
produces predictable and optimal energy x-rays
high atomic numbers
high thermal conductivity
low vapor pressure (don’t want vapor in vacuum)

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16
Q

What percentage of diagnostic x-ray beam is characteristic radiation

A

30%

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17
Q

This is a significant byproduct of X-ray production (over 99%)

A

heat

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18
Q

What is used to reduce overheating of the target

A

copper stem of anode and oil immersion

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19
Q

The heterogenous x-ray beam produced at the anode is net out of a lined tube through what

A

the portal; a channel for the passage of X-rays

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20
Q

This absorbs less penetrating (long wavelengths) x-rays which are harmful

A

the filter; made of aluminum

21
Q

X-rays with longer wavelengths are mostly absorbed by what and do not reach the target tissues

A

skin

22
Q

What is the half valve of the filter

A

the thickness of it; reducing number of X-rays passing

23
Q

This is “shaping of the beam”

A

collimation

24
Q

What does x-ray beam collimation greatly reduces what

A

unnecessary exposure to patients

25
Q

Most x-ray tubes have which type of collimation

A

round (7cm)

26
Q

This type of collimation is slightly larger than the size of the image receptor

A

rectangular

27
Q

This shaped diaphragm limits the size of divergent beam

A

doughnut

28
Q

This farther reduces the beam size providing mean of aiming the beam

A

external collimator

29
Q

What are the necessary conditions for x-ray production involving electrons

A

separation of electrons
concentration of electrons
imparting high speed to the electrons
sudden stopping of the electrons stream to produce x-rays

30
Q

The purpose of this is to supply electrons through a heated filament cathode is the negate electrode

A

cathode

31
Q

The cathode filament is recessed into what to help contain and direct electrode

A

molybdeum focusing cup

32
Q

The purpose of this is to stop the high energy electrons and to convert their kinetic energy into x-rays and the positive electrode

A

anode

33
Q

This is low-voltage circuit, filament made of tungsten, molybdenum focusing cup, and electron cloud

A

cathode

34
Q

This is high-voltage circuit, angled tungsten target/focal spot, heat absorber/radiator (copper)

A

anode

35
Q

The production and separation is much like this

A

like a light bulb

“thermionic emission”

36
Q

The electron cloud is produced at what

A

the filament

37
Q

The electrons become more active by what

A

random collisions producing more free electrons

38
Q

Theis located at the cathode serves to concentrate the electrons

A

molybdenum collar (focusing cup)

39
Q

When the high voltage circuit (at the anode) is activated, these concentrated electrons form a beam that does what

A

hits the focal spot located on the face of the copper anode

40
Q

What activates the high voltage circuit at the anode

A

high potential difference created between the filament cathode and target anode

41
Q

These parts of the control panel influence radiographic imaging

A

millamperage (number of electrons)
exposure time (between cathode/anode)
kilovoltage

42
Q

These are factors influencing radiographic image

A

density, contrast, resolution
distortion
filtration and collimation

43
Q

True or False

The distance from source to receptor and the distance from object to receptor can play a roll in radiographic image

A

True

44
Q

Object attenuation (absorption) depends on what

A

density (of bone and such)
atomic number
thickness

45
Q

The permeability of x-rays depends on what

A

photon energy
thickness of object
density of the object being radiographed

46
Q

This is the complete absorption of the beam of object (like amalgam)

A

photoelectric absorption

47
Q

This is almost complete absorption (like cortical bone)

A

coherent/thompson scattering

48
Q

True or False

There is no such thing a complete penetration to receptor

A

False; there is in air filled spaces like the maxillary sinus

49
Q

This is scatter-partial/tangential exposure of receptor; undesirable but always occurs

A

compton scattering

SU14 Oral Radiology (22 decks)

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