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CT > System Components > Flashcards

System Components Flashcards

1
Q

-ring /donut shaped
Aperture (internal opening / center) : 70-90cm
Can be tilted forward & backward
Has a laser light for positioning
Control panel on sides (can also be in control console)
Contains : embedded microphone and speaker

A

Gantry

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2
Q

Control panel of gantry controls:

A

Alignment of lights
Tilt of gantry
Table movement of gantry

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3
Q

Gantry houses imaging components:

A

Slip ring s
Xrt
High voltage generator
Collimators
Detectors

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4
Q

Other than ct what are other machines that also have their generators inside

A

Portable xray

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5
Q

Muo: carbon fiber

A

Patient table or couch

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6
Q

Why carbon fiber

A

Lightweight (to not absorb or attenuate much of the xrays)
Strong and rigid
Best material
Provide comfort

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7
Q

2 division of xray system

A

Generator
CT scan xray tube

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8
Q

Uses 3 phase power for the efficient production of xrays
Located inside the gantry
The voltage ripple from a high frequency generator is 1%

A

Generator

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9
Q

Generator of ct before

A

High voltage generator
- generator was outside before

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10
Q

Generator of ct now and its benefits

A

High frequency generator
-small
-comoact
-more efficient

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11
Q

Problem w ct generator before

A

Can’t rotate normally due to wiring of cables and generator outside

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12
Q

Fluctuations of current after being rectified

A

Voltage ripple

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13
Q

Current in xray system

A

Direct current
(always in one direction)
Never in Ac cuz it can cause tube failure and no efficiency of xray production

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14
Q

Ac to dc

A

Rectified

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15
Q

Momentarily stores energy

A

Capacitor

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16
Q

Permits gantry to rotate continuously eliminating the need to straighten turned system cable

Use a brush-like apparatus = to provide continuous electric power

A

Slip ring

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17
Q

Component of tube enclosure of ct scan xrt

A

Metal instead of glass
Cuz of electrical arcing

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18
Q

Component fo glass enclosures

A

Borosilicate

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19
Q

Explain electrical arcing

A

When there’s too much heat - that damages or melts the target material - which will vaporate - as tube also rotates it will splatter around the xr and can attach to the enclosure = as cathode continues to produce electrons - electricity flow or induced current would be distracted will it go to the filament or the follow material of the target was melted ===tube arcing / tube failure

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20
Q

Consists of tungsten filaments positioned in a focusing cup

A

Cathode assembly

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21
Q

Muo: barium
Coil of wire
Fx: absorbs gas in a vacuum cud the presence of gas decreases efficiency of tube / xray production cuz it interfered flow of electrons

A

Internal getter

22
Q

Appearance of Barium

A

Not pressured or is contaminated = WHITE
Vaccuum maintained =silver

23
Q

Anode assembly consists

A

Disk
Rotor stud
Hub
Rotor
Bearing assembly

24
Q

Small target angle around 12 deg

A

Anode assembly

25
Q

Small focal spot = higher spatial resolution

A

Cuz it limits the size of the usable xray field
Anode heel effect - angulated therefore less surface exposed

26
Q

Relevance of fast xray tube / high rotational anode

A

= heat dissipation is not concentrated on 1 area / for cooling

27
Q

CT XRT uses?

A

Ceramic insulator
- so it would not involve the current on the cathode side
So that if you touch the xrt you won’t be electrocuted

28
Q

Uses thicker (5cm) larger diameter anode disk (200mm)

A

Ct xrt

So that if projectile electrons Hit the focal spot the heat will be shared on the external structure (heat transfer by conduction)

29
Q

Energy transfers

A

Conduction
Induction
Convection

30
Q

3 basic designs of anode disk

A

All metal disk design
Braced graphite anode disk
Chemical vapor deposition

31
Q

Base bodies of all metal like design

A

Titanium
Zirxonium
Molybdenum

32
Q

Focal track layer

A

10% rhenium
90% tungsten

33
Q

Advantage and disadvantage of all metal disk design

A

Adv: quick heat transfer
Disad: heavy weight (can’t rotate efficiently)

34
Q

BASE BODY of Braced graphite anode disk

A

Majority graphite (10x higher heat capacity(ability to absorb heat) than tungsten)

35
Q

FOCAL TRACK LATER of Braced graphite anode disk

A

Tungsten rhenium

36
Q

Advantage of Braced graphite anode dism

A

High heat storage capacity
Faster anode cooling

37
Q

BASE BODY of chemical vapor deposition graphite disk

A

Graphite

38
Q

FOCAL TRACK of chemical vapor deposition graphite disk

A

TUNGSTEN - RHENIUM
can accommodate large, lightweight disks w/ large heat storage capacity

39
Q

Helps reduce the radiation dose to the patient and
Improves image quality

A

Filtration

40
Q

Purpose of filtration

A

Removed long wavelength (lowenergy) xrays

Shares the energy distribution across the radiation beam by using shaped filter

41
Q

Controls slice thickness
Restricts xr beam to specific area

A

Collimator

42
Q

2 types of Collimators

A

Prepatient Collimators
Postpatient Collimators

43
Q

Determine rad dose profile and pt rad dose

A

Prepatient /Postpatient source Collimator

44
Q

Determine sensitivity profile and improves image contrast
Higher tendency of scatter after passing thru the patient

A

Predetector Collimator

45
Q

Lighter than peripheral cuz head is thicker
Peripheral or sides is dark cuz not the same thickness
Homogenous beam
Eliminate scatter

A

Bow tie filter

46
Q

Capture the rad Beam from pt and convert it into electrical signals, which are subsequently converted into binary coded information

A

Ct detector

47
Q

2 types of Detectors accdg, to material

A

Xenon gas detector
Solid-state crystal detector

48
Q

Adv: ability to remain stable under pressure, cheaper, easier to calibrate

Disadv: xenon gas must be kept under pressure in an aluminum casing

A

Xenon has detector

49
Q

Adv: higher absorption coefficient (100%)(xenon - 60-87%)
Disadv: sensitive to fluctuatkonin temperature & moisture

A

Solid-state crystal detector (scintillating detectors

50
Q

Composition of solistate detector

A

-cadmium tungstate
Bismuth germinate
Cesium iodide
Gadolinium or yttrium

CT (3 decks)

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