Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MRT Year 1 Semester 1 > Midterm Review Apparatus And Image > Flashcards

Midterm Review Apparatus And Image Flashcards

1
Q

What is mA? mAs?

A

mA: the number of electrons available to move from cathode to anode
mAs: the # of electrons sent in 1 second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why does the x-ray tube require DC current?

A

Electrons must only flow in one direction (cathode to anode)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the main cause/factor of tube failure?

A

Heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

When electrons stray and hit the anode in a different spot

A

Off-focus radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

“Any combo of mA and time (as long as mAs is the same) will produce the same density”

A

Reciprocity law

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

The invisible image before its processed

A

Latent image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Purpose of glass/metal envelope

A

Maintain vacuum in the tube

Metal envelope extends tube life/avoids arcing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is a beam restrictor? Types?

A

Device that attached to the opening in the x ray tube housing to regulate the size and shape of the beam. Control and minimize scatter

  • Aperture diaphragm: flat piece of lead or lead lines material that fits onto x-ray tube head
  • Cone and Cylinders: extension code or cylinder attached to an aperture diaphragm
  • Variable Aperture Collimator: 2 sets of shutters. 2 set can be adjusted to restrict beam
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Function of the step up transformer

A

Increases voltage from the autotransformer to the kV needed for x-ray production
Increases by a fixed amount

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How does an electronic timer work?

A
  • a capacitor takes a preprogrammed charge, once it is charged the exposure stops
  • the resistance changes in order to charged the capacitor faster/slower for a longer/shorter exposure time
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Types of body habitus

A
  • Sthenic- average, muscular
  • Aesthenic- small, frail
  • Hypersthenic-large
  • Hyposthenic- thin, slim, healthy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Types of pathologies

A
  • Destructive: increases radiolucency

- Constructive: increases radiopacity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

To produce x-rays you must have…

A
  • source of electrons (cathode)
  • means to accelerate electrons
  • means to decelerate electrons (anode target)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Differential absorption

A

The difference in how different body tissues/parts absorb the beam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Advantages of less ripple

A
  • greater radiation quantity and quality
  • higher energy of x-rays
  • high efficiency of x-rays
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Factors affecting OD

A
  • mAs

- SID

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Components of the filament circuit

A

Rheostat, step down transformer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

keV vs. kVp

A

keV: measurement used for binding energies and energy of the incident electron
kVp: the forces with which incident electrons interact with the tungsten target

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What happens when the exposure switch is pressed halfway?

A
  • electricity goes to induction motor and bring rotor up to speed
  • selected filament in energized and electron cloud is built up
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Focal Distance/ Grid Radius

A

Distance between grid and convergent line

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Types of x ray tubes

A

Crookes tube: no vacuum, gas filled, on mA station

Coolidge tube: vacuum, glass/metal envelope, various mA stations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is another name for Off center grid error

A

Lateral decentering

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is another name for the characteristic x-ray spectrum?

A

Discrete emission spectrum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Functions of the autotransformer

A

Provides voltage to the step up transformer depending on what kV is set. Different combos of the secondary connections allow for increasing sand decreasing voltage
Step up: more coils used
Step down: less coils used

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Contrast improvement factor and formula

A

The ability of a grid to improve contrast

K= image contrast with grid/ image contrast without grid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Table characteristics

A 
Shape: flat, curved
Uniform Radiolucency
Durable
Easy to clean
Hard to scratch
High weight limit
No crevices
Can include cassette holder or detector
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

The absorption of the beam by the lead strips of a grid

A

Grid cut off

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Functions of rectifier. Types of rectified voltage

A

Converts AC to DC to keep electrons flowing only from anode to cathode

Unrectified voltage: x-rays not made during second half of cycle

Half wave rectification: inverse voltage is removed, the rectifier does not conduct during the negative cycle, gaps when current is not being conducted

Full wave rectification: inverts the negative half so the anode is always positive 0-100% ripple

Three phase power: used 3 AC waveforms at the same time but out of sync 3 phase 6 pulse (4-14%ripple), 3 phase, 12 pulse (4% ripple)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

The relationship between the actual and effective focal spots is direct or indirect?

A

Direct

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

APR and how it works

A

Anatomically programmed radiography

-Preprogrammed set of exposure factors for different body parts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Grid (Bucky) Factor

A

No grid- 1

5: 1- 2
8: 1- 4
12: 1- 5
16: 1- 6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Function of timer circuit

A

makes or breaks high voltage across tube

Located in primary circuit because it is easier to control low voltage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What does “quality” mean in regards to radiation?

A

Strength of radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Increasing mAs had what affect on scatter?

A

No affect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Principle Components of the equipment

A
  • operating console
  • x-ray tube
  • high voltage generator
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What will happen if the field size is too big when using AEC? Too small?

A

Too much scatter will reach the cell and cause the AEC to shut off prematurely

Too small: AEC will take longer to receive enough radiation to end exposure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Types of timing circuits

A
  • Synchronous
  • Electronic
  • mAs
  • AEC
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Types of Anodes

A

Stationary: target doesn’t move, electrons always heating up same spot-heat builds up faster-limited to small exposures

Rotating: allows electron beam to interact with a greater target area (500x bigger)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What type of x-rays form a continuous emission spectrum?

A

bremsstrahlung

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Probability of PE interactions increases when…

A

-Energy levels are closer (binding energy and photon energy)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Advantaged of high frequency generators

A
  • less than 1% ripple
  • smaller, lightweight
  • less costly
  • better exposure reproducibility
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What does kVp control

A

Radiographic contrast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Factors that affect radiographic density

A

“Prime exposure factors”

-kVp, mA, exposure time, SID

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What is the purpose of the back up timer?

A

To protect patient from overexposure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What happens to the emission spectrum with a high voltage waveform?

A
  • Increased amplitude

- Increased average energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Forces holding electrons in orbit?

A

Centrifugal: outwards force
Centripetal: center seeking

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Function of step down transformer

A

Reduce voltage going and increase current going to filament so it doesn’t break

48
Q

By what percent do we increase kVp to double the amount of photons hitting the IR?

A

15%-not directly proportional

49
Q

What is the air gap technique?

A

A method to reduce scatter. Move IR 10-15cm away from body part.

50
Q

How does a synchronous timer work?

A

Electric motor turns shaft at 60rpm. Exposure time selected determines the time it takes to go from the on switch to the off switch.

  • shortest time is 1/60s and timing intervals increase by multiples thereof
  • has to be reset in between
51
Q

What if an image is to light?

A
  • Low OD
  • underexposed
  • anatomy never there to begin with
52
Q

When SID is increased, radiographic density is ________?

A

Decreased

53
Q

Factors that affect scatter reaching IR

A
  • kVp
  • Field Size
  • Patient Thickness
54
Q

Function of tube housing

A
  • Hold and protect tube
  • Dissipate heat
  • Reduce leakage radiation
55
Q

Interactions that produce heat

A
  • excitation

- ionization of an outer shell electron

56
Q

Types of tube supports

A
  • ceiling
  • floor-to-ceiling
  • floor
  • c-arm
57
Q

How does mA affect the spectrum?

A

Increasing mA increases the # of photons at all energy levels, increasing the amplitude of the spectrum

58
Q

When do we use the reciprocity law?

A
  • Motion (trauma/peds)
  • Focal spot size
  • Breathing technique (4-6 seconds long when you want to blur out something)
59
Q

Anode heel effect is most apparent with…?

A
  • larger IR size

- smaller SID

60
Q

Parts of the induction motor

A

Stator: electromagnets arranged in pairs outside the envelope

Rotor: shaft made of iron surrounded by a copper cuff inside the envelope

Operated through mutual induction-stators create a magnetic field that the rotor follows/turns in sequence to

61
Q

What affect does kVp have on the spectrum?

A

The peak moved up and to the right because the average energy is higher and more x rays are being produced (incident electrons hitting anode at greater speed)

62
Q

Functions of the Anode

A
  • Electrical Conductor
  • Mechanical Support
  • Thermal Dissipator
63
Q

Types of tables

A
  • fixed: height adjustable

- tilting: move to 90 degrees upright and 15-30 degrees head down, fixed height

64
Q

What are grid frequency and ratio?

A

Grid frequency: # of lead lines per unit length

Grid Ratio: height of lead strips vs. distance between them

65
Q

Factors affecting density

A
  • Image quality factors (density, contrast)
  • Exposure Technique factors (kVp, mAs, SID)
  • Patient factors (cast?, size, pathology)
66
Q

What is the most effective means to reduce scatter hitting the IR?

A

Grids

67
Q

What is the k shell binding energy in tungsten (atomic #74)?

A

69.5 keV

68
Q

What is the function of the cathode? Parts? What is it made out of?

A

To provide a source of electrons.
Filament and focusing cup
Made out of thoriated tungsten because high atomic # (74) and high melting point (3410C)

69
Q

What does FFD stand for?

A

Focus to Film Distance

70
Q

What is positive beam limitation?

A

“Automatic collimation”
Automatic collimators adjust to size of cassette put in tray to ensure field size is not larger than IR
Does not replace manual collimation

71
Q

By how much do we need to change kVp to double density?

A

15%

72
Q

Disadvantages of filtration

A
  • more scatter (more matter more scatter)

- decreased image contrast

73
Q

How does the air gap technique affect density and contrast?

A

Decreases density

Increases contrast

74
Q

Grid Patterns

A
  • Linear: Parallel, focused

- Crossed/Cross hatched

75
Q

Types of radiation formed from interactions at target

A

Characteristic

Bremsstrahlung

76
Q

How does a mAs timer work?

A

It monitors the current passing through the tube and will terminate the exposure when the set mAs has been achieved.
located in secondary circuit in order to measure actual tube current

77
Q

Focal range

A

Recommended SIDs that can be used with a focused grid

78
Q

Types of moving grids

A
  • Reciprocating: motor driven, moved back and forth

- Oscillating: spring-like mechanism, moves in a circular motion

79
Q

How does increased fog affect density and contrast?

A
  • increase density

- decrease contrast

80
Q

Types of Filtration

A
  • Inherent: can’t be adjusted, built in
  • Added: can be adjusted
  • Compensating
81
Q

Function of the rheostat

A

Controls filament temperature and rate at which electrons are boiled off, the higher the mA the lower the resistance

82
Q

Define exponential absorption

A

As x-rays pass through tissue, for every increment of thickness, the x-rays are decreased in number by a certain percentage, never reaches zero

83
Q

What factors can influence the effectiveness of the focusing cup?

A
  • size
  • shape
  • charge
  • size of filament
  • shape of filament
  • how filament is sitting in focusing cup
84
Q

What is the density maintenance formula and when do we use it?

A

mAs1/mAs2 = SID1^2/SID2^2

  • Portables
  • To fit larger parts to a receptor
  • Patient condition
85
Q

What if an image is too dark?

A
  • High OD
  • Overexposed
  • anatomy will still be there, just not visible
86
Q

What causes the anode heel effect?

A

Line focus principle

87
Q

What is the anode target shaft made out of? Why?

A

Molybdenum with a copper coating

Copper is a good thermal/electrical conductor. Molybdenum has a LOW THERMAL CONDUCTIVITY and it light weight

88
Q

How is grid performance measured?

A

With the “K” contrast improvement factor

89
Q

The fuzzy-edge of the image

A

Penumbra

90
Q

What is an Atom?

A

Smallest particle that has all the properties of an element

91
Q

Falling load generators

A

Initial tube load is higher and drops during exposure

Achieved mAs set in a shorter exposure

92
Q

What is the limiter of the line focus principle?

A

Heat

93
Q

When SID is increased, scatter is ________?

A

Not change

94
Q

Moving grid errors

A
  • incorrect grid installation

- grid movement is same direction as grid lines: grid lines will show

95
Q

The area of the target where x-rays are emitted

A

Focal spot

96
Q

Function of the line compensator

A

Automatically adjusts power supply to 220V

97
Q

Why do we use filtration?

A
  • Increase x -ray beam quality

- increase penetrability (higher strength photons)

98
Q

How does AEC work? Types of AEC?

A

It measures the quantity of radiation reaching the IR and terminates the exposure when the required amount of radiation has been received

  • Photodiode/Phototimer: behind IR (Exit), converts light to electrical energy, once certain charge is reached exposure is terminated
  • Ionization Chamber: located between patient and IR (entrance), air inside cell becomes ionized as it is hit by radiation, ionization is directly proportional to amount of radiation. When predetermined charge has been reaching the exposure is terminated
99
Q

What happens to the emission spectrum when filtration is added?

A
  • Decreased amplitude

- Increased average energy (peak shifts right)

100
Q

Types of electric current

A

Alternating Current: changes direction in cycles as electric potential changes

Direct Current: flows in only one direction

101
Q

Ways to extend tube life

A
  • Minimize exposure factors for each exam
  • Utilize faster image receptors
  • Warm up anode (small warm up exposures)
  • Use shortest exposure times possible
102
Q

What is tube current?

A

The movement of electrons from cathode to anode

103
Q

What is the anode target made out of? Why?

A

Molybdenum core with a tungsten coating

Would be too heavy if all tungsten. Tungsten adds mechanical strength

104
Q

Attenuation consists of

A
  • Absorption
  • Scatter
  • Transmission
105
Q

What is the line focus principle?

A

The relationship between the actual and effective focal spot.
Allows for a larger area for heating while maintaining a small focal spot-angling target

106
Q

Components of main X-Ray circuit

A

Primary side: main power switch, line compensator, circuit breakers, autotransformer, step up transformer, timer circuit

Secondary side: mA meter, rectifier

107
Q

Stationary grid errors

A
  • off level: grid or tube is angled
  • Off focus: SID out of focal range
  • Upside down: grid is upside down
  • Off center: grid/tube not centered
108
Q

What is the autotransformer sometimes referred to as, and why?

A

-kVp selector
It directly impacts the voltage being supplied to the primary side of the step up transformer. The kVp selected on the console controls the autotransformer

109
Q

What is a Bi-Angle target

A

2 target angles on anode = 2 focal tracks

Filaments stacked on top of one another instead of parallel

110
Q

Imaginary lines drawn up from each of the lead lines on a focused grid, where they connect

A

Convergent point

If all the point were connected: convergent line

111
Q

How is radiographic density measured?

A

By optical density: scale of 0-4 (human vision 0.25-2.5)
>3 will be seen as black
<0.2 will be seen as clear

112
Q

What is the effective focal spot controlled by? What is the actual focal spot controlled by?

A

Effective focal spot controlled by actual focal spot. Actual focal spot controlled by:

  • Filament length
  • target angle
  • charge on the focusing cup
  • depth of filament in focusing cup
  • shape and size of focusing cup
113
Q

How is visibility achieved

A

The balance of contrast and density

114
Q

How does increasing atomic # affect compton interactions?

A

There is no change

115
Q

What is the main reason for using the line focus principle?

A

To decrease the size of the focal spot

MRT Year 1 Semester 1 (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions