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MRT Year 1 Semester 1 > Apparatus and Image Management > Flashcards

Apparatus and Image Management Flashcards

1
Q

When the field size is decreased, what happens to the density?

A

Density is decreased because there are fewer photons (less scatter) reaching the IR. Scatter still contributes to density although not useful

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2
Q

Latent Image

A

the image before it is processed-invisible

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3
Q

Interspace material is made out of what?

A

Usually aluminum or plastic fibre

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4
Q

Types of Exposure timers

A
  • synchronous timer
  • electronic timer
  • mAs timer
  • AEC: photodiode/phototimer, ionization chamber
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5
Q

Types of Filtration

A

Inherent: can’t be adjusted
Added: can be adjusted
Compensating: for different body part thickness

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6
Q

How does scatter affect contrast?

A

More scatter=less contrast

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7
Q

Density

A

The amount of blackness produce on an image after processing

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8
Q

As we increase the atomic number of the target material, the efficiency of the characteristic and bremsstrahlung radiation____________

A

Increases: because the binding energy for each shell increases

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9
Q

Positive Beam Limitation

A

When an exam is selected, the field size will automatically change or when an IR is place in the Bucky tray the collimators automatically adjust to the size

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10
Q

How do grids affect radiographic density?

A

Decrease because less photons reaching the IR

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11
Q

Grid (Bucky) Factors

A

No grid-1

5: 1- 2
8: 1- 3
12: 1- 4
16: 1- 5

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12
Q

What is the Line Focus Principle?

A

The relationship between the actual and effective focal spot

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13
Q

Types of stationary grids

A
  • Linear: parallel, focused

- Crossed/ cross hatched

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14
Q

Limitations of the Air Gap technique

A
  • increased technique
  • magnification on part of the image
  • increased image blur
  • not as effective with high kVp setting
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15
Q

Primary factors that affect scatter reaching the IR

A

kVp
Field size
Patient thickness

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16
Q

Grid ratio equation

A

Grid ratio = h/D

Height of grid divided by interspace width

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17
Q

3 disadvantages of crossed grids

A
  • positioning of grid is critical
  • tilt-table techniques are only possible if tube and table are properly aligned
  • higher exposure technique required
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18
Q

What happens when the exposure switch is pressed half way?

A

The rotor is brought up to speed

The filament is energized and begins to boil off electrons

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19
Q

Attenuation consists of:

A

Absorption
Scattering
Transmission

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20
Q

Less scatter reaching the IR=________ in radiographic density

A

Decreased

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21
Q

Components of the Cathode

A

Filament

Focusing cup

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22
Q

Factors that affect optimal radiographic technique

A
  • Image Quality Factors (density, contrast)
  • Exposure Technique Factors (kVp, mAs, SID)
  • Patient Factors
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23
Q

Types of moving grids

A
  • Reciprocating: motor driven, moves back and forth

- Oscillating: spring like mechanism, circular motion

24
Q

The contrast improvement factor is high for _____ ratio grids

A

Higher ratio grids

25
Q

Grid frequency

A

The number of strips per centimeter

26
Q

The fuzzy edge of an image

A

Penumbra

27
Q

Grid Conversion Factor

A

Used to determine the new technique when changing grid ratio (new grid)

mAs1/mAs2 = GCF1/GCF2

28
Q

Exponential Absorption

A

For every increment of thickness, the x-rays decrease in number, by a certain percentage

29
Q

Filament electrons that stray and hit the anode at different spots

A

Off-focus radiation

30
Q

What must you have to produce X rays?

A
  • Source of electrons
  • Means to accelerate electrons
  • Means to decelerate electrons
  • Vacuum
31
Q

Air Gap Technique

A

Method used to reduce scatter without using grids

IR is moved 10-15cm away from part-increased OID

32
Q

Functions of the Anode

A

Electrical Conductor
Thermal Dissipator
Mechanical support for target

33
Q

Grid errors

A
  • Off Level: x ray beam is angled across grid, grid is angled
  • Off Center: CR is not aligned side to side with the center of focused grid
  • Off Focus: SID out of focal range for grid
  • Upside Down: grid is used upside down
34
Q

Increase OID allows _____ scatter to reach the IR resulting in _______ density

A

Less scatter reaches the IR with increased OID resulting in decreased density

35
Q

Ways to extend tube life

A
  • Minimum exposure factors
  • Faster image receptors
  • Warming up anode
  • Use shortest exposure time
36
Q

Types of Interactions (with target)

A

Bremsstrahlung radiation

Characteristic Radiation

37
Q

mA

A

Milliamperes: the number of electrons available to move from cathode to anode

38
Q

How does increased scatter affect image density and image contrast?

A

Increase overall density

Decrease contrast

39
Q

What does the parallel and crossed grids do that is undesirable?

A

Grid cutoff

40
Q

Components of the Anode

A

Anode target
Stator
Rotor
Anode stem

41
Q

Tungsten

A

Atomic #74
Boiling point: 3410C
K shell binding energy: 69.5 kEv

42
Q

Types of Beam Restrictors

A

Aperture Diaphragms: flat piece of lead or lead lined metal that fits onto the x ray tube head
Cones/Cylinders:
Variable Aperture Collimators: two sets of shudders

43
Q

What is the anode target made out of?

A

Tungsten with a Molybdenum core to reduce weight and withstand heat expansion/contraction

44
Q

When kVp is increased there are: (with regards to interactions and scattering)

A

Fewer reactions overall, but of the reactions that occur, more are scatter

45
Q

The density produced on a radiograph remains the same for any combo of mA and time

A

Reciprocity Law

46
Q

Normal range of optical density that humans see

A

0.25-2.5 OD
>3=black
<0.2=white

47
Q

Contrast

A

The difference in OD between adjacent structures
High contrast: short scale
Low contrast: long scale

48
Q

Contrast improvement factor equation

A

k = image contrast with grid/image contrast without grid

49
Q

The probability of PE interactions increased if

A

Energy levels are closer together (binding and photon)

50
Q

How does kVp effect x rays?

A

It affects the quality and the quantity

51
Q

What is the filament made out of?

A

Thoriated Tungsten:
High boiling point (3410C)
Thorium extends filament life and increases thermionic emission
Doesn’t vaporize easily

52
Q

When kVp is increased, fog is _______

A

Increased

53
Q

Body Habitus

A

Sthenic: average, muscular
Hyposthenic: thin, slim, healthy
Hypersthenic: large
Aesthenic: small, frail

54
Q

Another name for the direct square law

A

Density Maintenance Formula

55
Q

What happens to the density as the SID is increased?

A

Same number of photons covering a bigger area=less density

MRT Year 1 Semester 1 (9 decks)

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