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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
Grid frequency
The number of strips per centimeter
26
The fuzzy edge of an image
Penumbra
27
Grid Conversion Factor
Used to determine the new technique when changing grid ratio (new grid) mAs1/mAs2 = GCF1/GCF2
28
Exponential Absorption
For every increment of thickness, the x-rays decrease in number, by a certain percentage
29
Filament electrons that stray and hit the anode at different spots
Off-focus radiation
30
What must you have to produce X rays?
- Source of electrons - Means to accelerate electrons - Means to decelerate electrons - Vacuum
31
Air Gap Technique
Method used to reduce scatter without using grids | IR is moved 10-15cm away from part-increased OID
32
Functions of the Anode
Electrical Conductor Thermal Dissipator Mechanical support for target
33
Grid errors
- 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
Increase OID allows _____ scatter to reach the IR resulting in _______ density
Less scatter reaches the IR with increased OID resulting in decreased density
35
Ways to extend tube life
- Minimum exposure factors - Faster image receptors - Warming up anode - Use shortest exposure time
36
Types of Interactions (with target)
Bremsstrahlung radiation | Characteristic Radiation
37
mA
Milliamperes: the number of electrons available to move from cathode to anode
38
How does increased scatter affect image density and image contrast?
Increase overall density | Decrease contrast
39
What does the parallel and crossed grids do that is undesirable?
Grid cutoff
40
Components of the Anode
Anode target Stator Rotor Anode stem
41
Tungsten
Atomic #74 Boiling point: 3410C K shell binding energy: 69.5 kEv
42
Types of Beam Restrictors
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
What is the anode target made out of?
Tungsten with a Molybdenum core to reduce weight and withstand heat expansion/contraction
44
When kVp is increased there are: (with regards to interactions and scattering)
Fewer reactions overall, but of the reactions that occur, more are scatter
45
The density produced on a radiograph remains the same for any combo of mA and time
Reciprocity Law
46
Normal range of optical density that humans see
0.25-2.5 OD >3=black <0.2=white
47
Contrast
The difference in OD between adjacent structures High contrast: short scale Low contrast: long scale
48
Contrast improvement factor equation
k = image contrast with grid/image contrast without grid
49
The probability of PE interactions increased if
Energy levels are closer together (binding and photon)
50
How does kVp effect x rays?
It affects the quality and the quantity
51
What is the filament made out of?
Thoriated Tungsten: High boiling point (3410C) Thorium extends filament life and increases thermionic emission Doesn't vaporize easily
52
When kVp is increased, fog is _______
Increased
53
Body Habitus
Sthenic: average, muscular Hyposthenic: thin, slim, healthy Hypersthenic: large Aesthenic: small, frail
54
Another name for the direct square law
Density Maintenance Formula
55
What happens to the density as the SID is increased?
Same number of photons covering a bigger area=less density

MRT Year 1 Semester 1 (9 decks)

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