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Radiology > Rad1 > Flashcards

Rad1 Flashcards

1
Q

X-rays are…

A

a form of electromagnetic radiation

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2
Q

X-rays are similar to visible light but…

A
  • Can not be seen, felt, heard

* Carry more energy-more likely to cause injury

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3
Q

Possible outcomes when living tissue is exposed to X-rays

A
  • X-rays pass through tissue w/ no effect
  • Produce cell damage that is repairable
  • Produce cell damage that is nor repairable
  • Kill cell
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4
Q

X-rays damage living tissue by …

A

imparting ionizing radiation that can alter the normal chemical structure of biological molecules

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5
Q

Types of radiation injuries

A
  • Skin burns, cataracts, anemia cancer (somatic damage)
  • Birth defects–>skeletal/dental malformation, mental retardation, microphthalmia (genetic damage)
  • Rapidly reproducing cells most commonly affected
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6
Q

Sources of radiation

A
  • X-ray machines
  • Radioactive materials from nuclear plants
  • Background–> Cosmic rays, building materials, earth’s crust, the body
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7
Q

RAD

A

(radiation absorbed dose)–

measure how much ionizing radiation is absorbed by an individual

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8
Q

REMs

A

(Roentgen equivalent man)
measure of the amount of ionizing radiation and it’s ability to cause tissue damage
– also known as radiation dose equivalent

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9
Q

Sievert (Sv

A

another unit used to express radiation dose equivalent measurements
1 Sv = 100 rem

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10
Q

gray units (Gy)

A

Radiation exposure can also be measured using gray units (Gy)
1 GY = 100 rad

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11
Q

Dosimeters

A

devices used to measure radiation exposure
o Film badge
o Thermo-Luminescent Dosimeter (TLD)
• Dosimeters must be worn when taking radiographic exposures

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12
Q

Basis of X-ray Radiation

A
  • X-rays are a form of energy
  • Part of the electromagnetic spectrum
  • X-rays can be produced in a laboratory by directing high speed electrons at a target atom
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13
Q

Maximum Permissible Dose (MPD)

A

amount of radiation an individual may receive w/o suffering appreciable bodily injury during a lifetime

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14
Q

Minimum safety standards

A 
•	set by federal government
•	Maximum Permissible Dose
       o	5 rem/yr (0.05 Sv/yr)
•	No one under 18 is allowed to work w/ ionizing radiation equipment
•	Pregnant women have lower limits
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15
Q

Physical properties of X-rays

A
  • Penetrate materials that absorb or reflect visible light
  • Travel in a straight line
  • Cause certain substances to fluoresce
  • Cause chemical changes on radiographic film that form a visible image after development
  • Cause injury to living tissue
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16
Q

Four components necessary for X-ray production

A
  1. Source of electrons
  2. Method of accelerating electrons
  3. Obstacle-free path for the passage of fast speed electrons
  4. A target w/ which electrons can interact to produce X-rays
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17
Q

Cathode

A

Made of molybdenum cup and tungsten filament

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18
Q

Anode

A

Beveled tungsten target on a copper base

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19
Q

Glass envelope

A

Creates vacuum between cathode and anode

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20
Q

Acceleration of electrons

A

Electrical potential difference created between cathode and anode

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21
Q

radiograph film

A
  • Polyester base w/ a gelatin emulsion cover
  • Exposure to visible light or X-rays causes chemical changes in silver halide crystals
  • Screen film is more sensitive to fluorescent light than X-rays
  • Nonscreen film is more sensitive to X-rays
  • Speed correlates with the amount of radiation necessary to make a radiograph
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22
Q

Intensifying screens

A
  • Used w/ screen film
  • Reduce the amount of radiation necessary to make a radiograph
  • Plastic base w/ a phosphor crystal layer cover
  • Emit a fluorescent light that causes 95% of screen film exposure
  • Screen speed correlates with the amount of radiation necessary to make a radiograph
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23
Q

Cassette

A

• Light-tight container that holds the film and intensifying screens in close contact
• Materials
o Front- polycarbonate, aluminum, magnesium, carbon fiber
o Back- a heavy material lined with lead

24
Q

Digital image receptors

A
  • Convert an analog signal (i.e. visible light produced by special intensifying screens) into a digital, electrical signal
  • The digital electrical signals are used to create pixels (picture elements) that form a visible radiographic image on a computer monitor
25
Q

CR systems

A

Digital image receptors may resemble and be used in the same manner as a conventional X-ray film cassette

26
Q

Advantages of digital image receptors over conventional X-ray film

A

o Eliminates the need of X-ray film processing
o Better images that are made faster with fewer mistakes (i.e. retakes)
o Images can be manipulated (size, degree of darkness, contrast, measurements can be made, images can be sent)

27
Q

CR vs. DR systems

A

o DR systems have a higher startup cost
o DR systems require no cassette handling faster image acquisition
o CR systems can be used for horizontal and vertical film images

28
Q

Controllable components of the X-ray machine that play a role in the formation of the radiographic image

A

o Milliamperage
o Exposure Time
o Kilovoltage Peak
o Focal-Film Distance

29
Q

Milliamperage (mA)

A

o Measure of the electrical current that is used to heat the wire filament at the cathode
o The temperature reached by filament is directly related to the # of electrons that are freed from their orbits to travel to the anode

30
Q

Exposure Time

A

o Controls the period of time during which X-rays are actually produced in the X-ray tube
exposure time ~ # of X-rays produced

31
Q

Both mA and exposure time control…

mA x exposure time =

A

• the # of X-rays produced during a radiographic exposure

= # of X-rays produced

32
Q

Kilovoltage Peak (kVp)

A

• Measure of the electrical potential difference between the cathode (-) and the anode (+)

33
Q

Focal-Film Distance (FFD)

A

o The distance between the focal spot in the X-ray tube and the X-ray film
o FFD affects the # of X-rays that reach the film during a radiographic exposure

34
Q

Inverse square law

A

The intensity of the beam is reduced by 1/4th when you double the distance from the source

35
Q

Visual quality of a radiograph image is assessed by looking at

A

o Radiographic density-
o Radiographic contrast
o Radiographic detail-
o Radiographic distortion

36
Q

Radiographic density

A

o Dependent on the # of X-rays reaching the film

o The more X-rays to reach the film, the greater the blackness and the greater the density

37
Q

Exposure Factors affecting radiographic density

A

o mA-s determines the number of X-rays produced, inc. mA-s inc. radiographic density
o kVp determines penetrating power of X-rays, inc. kVp inc. radiographic density
o FFD the farther the film is from the X-ray tube, the fewer the X-rays that reach the film and the lower the radiographic density

38
Q

Film processing and patient factors affecting radiographic density

A

 Developing time
 Developing temperature
 Tissue thickness and tissue density of subject being radiographed

39
Q

Radiographic contrast

A

visible difference between two adjacent structures on a film

o Dependent on variations in penetrating power of X-rays

40
Q

High contrast

A

black and white tones w/ very few gray tones

41
Q

Low contrast

A

many gray tones between black and white tones

42
Q

Exposure factors affecting radiographic contrast

A

kVp Variations in kVp and the penetrating power of X-rays can create more or fewer shades of gray on a radiograph

43
Q

Patient and other factors affecting radiographic contrast

A

 Differences in tissue thickness/density of the part being radiographed affect radiographic contrast
 Scatter radiation non-image forming X-rays that expose inappropriate area of the film and decrease radiographic contrast

44
Q

Radiographic detail

A

image sharpness, clarity

45
Q

Factors affecting radiographic detail

A

 Focal spot size
 FFD
 Animal motion
 Screen-Film contact

46
Q

Radiographic distortion

A

change from the original size and shape of the subject being radiographed

47
Q

Distortion is Prevent by

A

 Positioning subject as close to cassette as possible
 Positioning point of interest in the center of the X-ray beam
 Positioning subject parallel to cassette

48
Q

Technique Chart

A
  • A document that lists predetermined exposure factor settings based on the thickness of the region of the animal’s body being radiographed
  • Provides a consistent method for choosing the correct exposure factor settings
  • Avoids having to recalculate exposure factor settings each time a radiograph is taken
49
Q

Variables affecting technique chart formulation include:

A

o X-ray machine (calibration, line voltage)
o Animal species: Bird vs. Horse
o Anatomical Region
 Extremities Thorax, Abdomen

50
Q

Determine kVp requirement using Santes’ rule:

A

2 X tissue thickness in cm + FFD in inches + grid factor = kVp
o Grid factor must be added to compensate for primary X-rays absorbed by the grid during exposure

51
Q

Determine mA and exposure time settings

A

o mA typically set to highest setting to avoid motion artifact on radiograph
o Exposure time set based on mA-s requirement for region of body and the speed of intensifying screen/film being used

52
Q

Patient Restraint for Large animal

A

• Be careful when handling animal
o Introduce animal to X-ray machine, cassette
o Avoid sudden movement, loud noises
• Sedation, twitches, stocks can be used if necessary

53
Q

Equipment for Large animal

A
  • X-ray machine used must be maneuverable
  • Portable units
  • Mobile modular units
  • Mounted units
54
Q

Patient Preparation for Large animal

A 
•	Part of animal being radiographed must be clean and dry
•	For hoof radiographs:
o	Remove horseshoe
o	Pack sole with Play Doh
•	Positioning Devices
o	Wooden blocks, cassette tunnel
55
Q

Radiation Safety for Large animal

A
  • Safety rules discussed for small animals still apply
  • Use cassette-holding devices
  • Make sure assistants are not in the path of the primary beam

Radiology (4 decks)

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