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X-ray Physics > Test #3 > Flashcards

Test #3 Flashcards

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0
Q

Why do you use intensifying screens?

A

Because they amplify the remnant radiation & they decrease pt dose

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1
Q

These convert the energy of the x-ray beam into visible light by utilizing certain chemical compounds which produce light when expose to x-ray photons

A

Intensifying screens

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2
Q

This covers & protects the phosphor layer. Helps resist abrasions & static electricity

A

Protective Coating

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3
Q

This is the active layer that emits light when stimulated by x-rays

A

Phosphor

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4
Q

Type of active layer that emits blue light. Used w/ blue sensitive film. Oldest type.

A

Calcium tungstate

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5
Q

Type of active layer that emits green light. Used w/ green sensitive film

A

Rare earth

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6
Q

Why are rare earth screens better than calcium tungstate screens?

A

3-4x better at converting photon energy into light = decrease pt. dose.
Better light producing charac. over the range of kilovolt values.

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7
Q

What is the reflective layer made out of?

A

Magnesium oxide or titanium oxide

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8
Q

What does the reflective layer do?

A

Redirects the light toward the film - double the photons reaching the film

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9
Q

This layer provides the mechanical support for the phosphor

A

Base

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10
Q

What is the base layer made out of?

A

Polyester, metal, or card board

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11
Q

This is the relative number used to quantitate the efficiency of conversion of x-rays to light

A

Screen speed

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12
Q

What are the charac. of a faster screen speed?

A

More light emitted for the same exposure
Decrease pt dose
Have poorer recorded detail
Increase density

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13
Q

Angiography rare earth screens have what two advantages?

A

Require less exposure time = decrease pt dose & decrease pt. motion
Increase tube life

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14
Q

Holder that contains the screens & holds the film

A

Cassettes

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15
Q

What are the front & back of cassettes made of?

A

Front - plastic or graphite

Back - lead lined to prevent back scatter

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16
Q

What are examples of how to care for screens & cassettes?

A 
Mark the outside of cassette & inside of screen w/ #
Mark date of purchase on cassette (last 7 yr)
Use proper film/screen combo
Do screen test
Clean screens at least every 3 mos.
Don't touch screens
Don't stand on plastic cassettes
Light leaks indicate black edges on film
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17
Q

What is involved in image acquisition in CR?

A

Filmless cassette
Imaging plate: latent image is formed in the photostimulable phosphor
Wider latitude than conventional x-ray = better visualization of soft tissue & bone

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18
Q

What are the 3 primary stages of computed radiography (CR)?

A

Image acquisition
Image processing
Image display

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19
Q

What is the advantages of image display in CR?

A

Displayed on a high resolution monitor
Can print onto film
Can send to distant location
Can store on a disc

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20
Q

What are the steps involved in manual (hand tanking) processing?

A 
Wetting
Developing
Stop Bath
Fixer
Wash
Dry
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21
Q

What is the purpose of wetting during manual processing?

A

Causes the emulsion to swell allowing for chemicals to penetrate

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22
Q

What occurs during the developing step of manual processing?

A

Converts the latent image to manifest image
Chemically reduces the silver ions to metallic silver
If film oxidizes w/ air, it turns brown

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23
Q

What is the active ingredient in the Stop Bath?

A

Acetic acid

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24
Q

This stops development by neutralizing the developer & removes excess chemicals from the emulsion

A

Stop bath

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25
Q

This treats films so the image will not fade & will remain permanent. Ammonium thiosulfate clears undeveloped silver halide.

A

Fixer

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26
Q

During this step, water removes any residual fixer.

A

Wash (if fixer isn’t completely removed film could turn brown)

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27
Q

What steps are different b/w automatic processing & manual processing?

A

Wetting occurs during the Developer step
Acetic acid is in the fixer so no Stop Bath step
Overall, automatic occurs much faster than manual (90secs vs 1hr)

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28
Q

The removal of silver from the used fixer solution as fixer removes the unexposed silver halide from the film

A

Silver Recovery

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29
Q

What are the two types of Silver Recover?

A

Metallic replacement: steel wool or foam that is impregnated w/ steel wool
Electrolytic: Electrically charged disc or drum to attract the silver (most efficient & expensive type)

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30
Q

Type of artifact that run the length of the travel direction of the film, usually 1” apart

A

Guide shoe marks

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31
Q

What causes Guide Shoe Marks?

A

Rough handling of rollers during cleaning, warped plastic rollers
Lines are black = developer section
Lines are white = fixer or wash section

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32
Q

This artifact is caused by kinking film w/ finger or fingernail

A

Crescent moon marks

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33
Q

This artifact is caused by inadequate or improper chemistry

A

Chemical Fog

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34
Q

This artifact is when there are yellow, green, blue, or purple runs on the film. It is caused by chemistry not being squeezed from film d/t warped rollers or processor is running to slow

A

Curtain effect

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35
Q

This artifact causes tree-like black jagged lines or smudges.

A

Static (caused by static in the room, carpet)

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36
Q

This artifact is caused by light leaks, primary beam, safe light too close

A

Light or radiation fog

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37
Q

This artifact is when there is greater density (darker) than the area of the x-ray surrounding it

A

Plus density

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38
Q

This artifact is when there is less density (lighter) than the area of the x-ray surrounding it

A

Minus density

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39
Q

What is Emulsion Pick Off (artifact) caused by?

A

Dirty rollers

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40
Q

This artifact is when yellow/brown stains appear over time. Caused by not all of the (fixer) thiosulfate is removed in the wash. Wash-water contaminated, not clean

A

Hypo/Hyporetention

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41
Q

What equipment is used to monitor the processor?

A

Thermometer
Sensitometer
Densitometer
Dedicated film supply

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42
Q

This measures the light transmitted through the tablet (film). It detects small changes in optical density that occur when the film is fogged.

A

Densitometer

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43
Q

This places a known light exposure onto the film & results in an image gradient of 21 different steps/degrees on the film

A

Sensitometer

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44
Q

What 3 factors are used when analyzing the tablet?

A

Base + fog density
Speed index
Contrast index

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45
Q

What is involved w/ base + fog density?

A

Read at the zero exposure step (step #1)
Normal should not be >0.30 OD
If > 0.25 the problem may be in the imaging system itself or the film storage facilities

46
Q

What is involved w/ the Speed Index (Mid density)?

A

Record the step # that reads 1.00-1.20 OD (should #11)

Same step should be used each time that you do the test

47
Q

Increasing what processing factors will increase density?

A

Processing temp

Development time

48
Q

What processing factors would decrease density?

A

Under replenishment of the developer
Oxidation of processing chemicals
Too low processing temp.
Too short development time

49
Q

This artifact occurs every 3.14”. Caused by dirty rollers or flat edge on roller.

A

Pi Lines

50
Q

Increasing what technical factors would increase density?

A

mAs
kVp
Film screen speed

51
Q

Increasing what factors would decrease contrast?

A

kVp
mAs
Development time

52
Q

Unit of radiation exposure that will liberate a charge of 2.58x10(-4) coulombs per kg of air. It is the approx. exposure to the body surface for a radiographic view. Intensity of the beam

A

Roentgen (R)

53
Q

Radiation measuring instruments are calibrated in what? Output of x-ray machines are also specified in this unit of measure

A

Roentgens

54
Q

This is the amount of radiation energy absorbed into a given mass of tissue.

A

Rad (Radiation absorbed Dose)

55
Q

1 Rad is equal to what?

A

Radiation necessary to deposit 100 ergs(?) in 1 gram of irradiated material

56
Q

The number of Rads deposited per roentgen of exposure varies w/ what two factors?

A

Energy of the x-ray beam

Composition of the absorber

57
Q

1 joule/kg is equal to how many Grays?

A

1 Gray (gy)

58
Q

1 Gray is equal to how many Rads?

A

100 Rads

59
Q

The avg CXR gives a dose of what?

A

10 millirads (mrad)

60
Q

What amount of Grays delivered to the whole body over a short period of time can be deadly?

A

3-4 Gray

61
Q

The unit of absorbed dose equivalent. Measures the energy per unit mass times adjustments for the type of radiation involved (quality factor) & the biological response in the tissue (a weighted factor)

A

REM (Rad Equivalent Man)

62
Q

What are 3 features of REM (Rad Equivalent Man)?

A

It converts dose into a measured risk
It is only used in radiation protection
It is a measure of biological effectiveness of radiation

63
Q

Why are personnel monitoring devices (Dosimeters/film badges) analyzed in REMs?

A

b/c it takes into account the biological effects of different types of radiation

64
Q

1 Sievert (Sv) is equal to how many mrem?

A

100,000 mrem

65
Q

This is a device used for the measurement of exposed dose

A

Dosimeter

66
Q

The effectiveness of a dose is dependent on what?

A

Dose-rate

67
Q

This is a dose of radiation that in light of presnet knowledge would not expect to produce significant radiation effects

A

MPD (maximum permissible dose)

68
Q

Cumulative MPD is equal to what?

A

5(n-18)rem n=age in years

69
Q

What is the annual MPD?

A

5 rem = 5000mrem = 50m SV/year

70
Q

This is a unit of radioactivity. It quantifies the amount of radioactive material & not the radiation emitted. It is the amount of material in which 3.7x10(10) atoms disintegrate every second

A

Curie (C)

71
Q

This type of radiation is somewhat shielded by the atmosphere so the dose is higher at higher altitudes

A

Cosmic Radiation

72
Q

For every 200ft increase in altitude, cosmic radiation dose increases to what?

A

Increase dose of 1 mrem/yr

73
Q

What are 3 types of rocks that emit radiation?

A

Uranium
Coal
Granite

74
Q

What is an example of a nutrient that emits radiation?

A

Potassium

75
Q

This is a radioactive gas that comes from inside the earth. Sometimes it gets trapped inside of homes coming through foundations & basements

A

Radon

76
Q

What are examples of things that cause man-made background radiation?

A 
X-rays
Medical isotopes
TV
Smoke detectors
Nuclear fuel
Weapons fallout
77
Q

What is the normal annual exposure from natural radiation?

A

300 mrem/yr

78
Q

What is the normal annual exposure from man-made radiation?

A

70 mrem/yr

79
Q

The biological effect of radiation is what?

A

Ionization (free radicals which can change chemicals in the body)

80
Q

What are effects of DNA damage sustained from radiation?

A 
Gene expression
Gene mutation
Chromosome Aberrations
Genomic Instability
Cell killing
81
Q

This type of DNA damage from radiation is when the gene responds by changing its signal to produce protein; this may be protective or damaging

A

Gene expression

82
Q

This type of DNA damage from radiation is when a gene may be changed so that it can’t make its corresponding protein properly

A

Gene mutation

83
Q

This type of DNA damage from radiation may trigger programmed cell death. If only a few cells are affected, this prevents reproduction of damaged DNA & protects the tissue

A

Cell Killing

84
Q

This is caused by damage to organs or systems after very high whole body doses. The symptoms depend upon the dose & time of exposure

A

Radiation Sickness

85
Q

Give examples of the effects of radiation sickness based on time of exposure i.e. minutes, days, weeks, months, years

A 
Minutes = CNS Syndrome
Days = GI Syndrome
Weeks = Hematopoietic Syndrome
Months = Birth defects, LD 50
Years = Cancer
86
Q

According to the U.N. Health Agency, this poses a greater long term health risk than radioactive particles in the air

A

Contaminated food

87
Q

What are some effects of fetal radiation?

A 
Prenatal death
Neonatal death
Congenital malformation
Childhood malignancy
Diminished growth & development
88
Q

What is the Law of Bergonie & Tribondeau?

A

Radiosensitivity is a function of the metabolic state of the tissue being irradiated

89
Q

What are examples of cells/tissues that are more radiosensitive than other?

A

Stem cells as compared to mature cells
Younger tissues & organs
Cells w/ high metabolic activity
Cells w/ a high rate of proliferation

90
Q

What are 4 cell types that have a high radiosensitivity?

A

Lymphocytes
Spermatogonia
Erythroblasts
Intestinal crypt cells

91
Q

What are 4 cell types that have an intermediate radiosensitivity?

A

Endothelial cells
Osteoblasts
Spermatids
Fibroblasts

92
Q

What are 3 cell types that have a low radiosensitivity?

A

Muscle cells
Nerve cells
Chondrocytes

93
Q

This is the dose of radiation to the whole body that will result in death w/i 30 days to 50% of the subjects irradiated

A

LD 50/30

94
Q

What is the LD 50/30 for a human?

A

300 rad

95
Q

This is the rate energy is deposited in tissue as ionizing radiation

A

L.E.T. (Linear Energy Transfer)

96
Q

What is the L.E.T. of diagnostic x-rays?

A

3 ke V/um

97
Q

Why is it difficult to determine if low doses cause cancer?

A

Background radiation is often higher than the level of added exposure
There is a high & variable rate of cancer in human populations
There is no way to tell a radiation induced cancer from a spontaneous cancer

98
Q

Low doses show different biological responses than high doses. Name 3

A

Increased activity of repair genes
Adaptive response
Cell/cell communication

99
Q

What are 3 cardinal principles of radiation protection?

A

Time: keep the time of exposure as short as possible
Distance: maintain a large distance b/w the exposed person & source of radiation
Shielding: Insert shielding b/w the source & exposed person (lead/concrete)

100
Q

10 rads during the first 2 wks of pregnancy can have what effect?

A

1/10 will experience spontaneous abortion, if not, preg. goes to term w/o ill effects

101
Q

10 rads during the 2-8 wks of pregnancy can have what effect?

A

1% will have congenital abnormalities

102
Q

At what dose of rads should a pregnant woman consider an abortion?

A

> 25 rads

103
Q

When a x-ray tech. becomes pregnant, what should they do?

A

Inform employer ASAP

Wear lead apron w/ monitoring badge on collar & one under apron to record fetal dose

104
Q

What are some preventative measures used to protect pregnant women?

A 
Have a consent signed for preg. release by all females of childbearing age
Practice 10 day rule
Gonandal shielding
Control access to x-ray room
Preg. tests
Post signs in the x-ray room
105
Q

What is the 10 day rule?

A

10 day interval following the onset of menstruation is the only time when it is most unlikely a woman could become preg. It is only during this time that you should x-ray the Lsp, pelvis, hips, sacrum or coccyx

106
Q

When should gonadal shielding be used?

A

When the gonads lie w/i the primary x-ray field or w/i 5cm off the edge of colimation

107
Q

What level of attenuation of x-rays should gonadal shielding provide?

A

At least equivalent of .25mm of lead

108
Q

Increasing what technical factors would decrease density?

A 
Body part thickness
Mass density of body part
Grid ratio
SID
Collimation
109
Q

Increasing what factors would increase contrast?

A

Film speed
Collimation
Grid ratio

110
Q

This type of DNA damage from radiation is when the entire chromosome may break, recombine in an abnormal way or sometimes parts of two different chromosomes may be combined

A

Chromosome aberrations

111
Q

This type of DNA damage from radiation may produce later changes that contribute to cancer

A

Genomic Instability

112
Q

What are the 10 basic radiation control principles?

A

Understand & apply the principles of time, distance, & shielding
Don’t allow familiarity to result in a false sense of security
Never stand in the primary beam
Always wear protective apparel when not behind a barrier
Always wear a personnel monitoring device
Never hold a pt
Person holding a pt should wear a lead apron
Used gonadal shielding
Observe 10 day rule
Always collimate to the smallest field size

X-ray Physics (4 decks)

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