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CT COMPONENTS Flashcards

1
Q

the ring-shaped part of the CT scanner. It houses many of the components necessary to produce and detect x-rays.

A

Gantry

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2
Q

Characteristics of Gantry

A

APERTURE / BORE

TILTING RANGE

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3
Q

Most of the scanners have ____ aperture

A

70 cm

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4
Q

There are also scanners that have an ___ bore.

A

85cm

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5
Q

Tilting range of most scanners

A

+30 TO -30 DEGREES

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6
Q

tubes produce the x-ray photons that create the CT image

A

X-ray Tube

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7
Q

Atomic number of Tungsten

A

74

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8
Q

Anode Material used in xray tube for ct

A

Tungsten

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9
Q

Contain more than one size of focal spot

A

0.5 and 1.0 mm are common sizes

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10
Q

Because of ______ small focal spots in CT tubes produce sharper images

A

reduced penumbra

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11
Q

used to shape the x-ray beam

A

Filters

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12
Q

Reduce the radiation dose to the patient and help to minimize image artifact

A

Filters

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13
Q

helps to reduce the range of x-ray energies that reach the patient since xrays are polychromatic

A

Filters

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14
Q

Creates a more uniform beam intensity improves the CT image by reducing artifacts that result from beam hardening

A

Filters

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15
Q

Collimation in CT serves two purposes:

A

To reduce unnecessary dose to the patient

To ensure good image quality by reducing scatter radiation.

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16
Q

two types of collimation

A

prepatient collimation

postpatient collimation

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17
Q

In CT, we use ____ to collect the information.

A

detectors

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18
Q

a single element or a single type of detector used in a CT system

A

detector

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19
Q

used to describe the entire collection of detectors included in a CT system.

A

detector array

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20
Q

optimal characteristics of a detector

A 
High detector efficiency
Low, or no afterglow
High scatter suppression
High stability
High reproducibility
Wide dynamic range
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21
Q

TYPES OF DETECTORS

A

Xenon gas detector

Scintillation (solid-state) detectors

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22
Q

use high-pressure (about 25 arm) nonradioactive xenon gas, in long thin cells between two metal plates.

A

Xenon detectors

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23
Q

The long, thin ionization plates of a xenon detector

A

highly directional

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24
Q

must be positioned in a fixed orientation with respect to the x-ray source.

A

xenon detectors

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25
is composed of a scintillator coupled tightly to a photodetector.
solid-state CT detector
26
emits visible light when it is struck by x-rays, just as in an x-ray intensifying screen
scintillator
27
an electronic device that converts light intensity into an electrical signal proportional to the light intensity.
photodiode
28
SCINTILLATION CRYSTALS USED WITH PM TUBES
Sodium iodide –afterglow + low dynamic range ( used in the past) Calcium fluoride Bismuth germanate
29
SCINTILLATION CRYSTALS USED WITH PHOTODIODE
Calcium tungstate Rare earth oxides Yttrium and gadolinium ceramics
30
, to reduce crosstalk between adjacent detector elements
a small gap between detector elements is necessary
31
DETECTOR EFFICIENCY | Gas detector
50% - 60%
32
Scintillation detectors
95% - 100%
33
X-ray photons that strike the detector must be measured, converted to a digital signal, and sent to the computer. Positioned within the gantry near the detectors.
DAS (DATA ACQUISITION SYSTEM)
34
Set of electronics between detectors and host computer
DAS (DATA ACQUISITION SYSTEM)
35
DAS contains
``` Amplifier ADC, DAC, Generator S/H. ```
36
Signal from detectors goes to amplifiers for signal magnification and then is sent to sample/hold unit
Amplifier
37
Located between amplifier and adc performs sampling and assigns shades of gray to the pixels in the digital matrix corresponding to the structures
Sample/Hold Unit (S/H)
38
Converts analog signal output from the scanning equipment to a digital signal so it can be processed by a computer.
ADC
39
shows the reading of the gantry tilt, table height, position of landmark, latch status, scannable range and tilt range
Display panel
40
pressing this button will immediately stop every mechanical movement and X-ray emission
Emergency button
41
incorporates several buttons mainly to control the movements of the gantry and table. Each front and rear cover has control panels.
Control panel
42
this uses a halogen based laser beam marker to assist in proper patient positioning; breath navi is used to give visual breathing instructions to patients with hearing problems
Positioning light and breath navi
43
for interacting with the patient
Microphone
44
patient lies on the table (or couch, as it is referred to by some manufacturers) and is moved within the gantry for scanning.
Patient Table/Couch
45
table is made up of a material with low atomic number such as _____ to avoid x-ray attenuation from the table itself.
carbon fiber
46
The process of moving the table by a specified measure is most commonly called
incrementation
47
incrementation is also referred to as
feed, step, or index
48
Patient Table/Couch | DISTRIBUTED WEIGHT LIMIT
450 LBS (204 KG)
49
Patient Table/Couch | COVERAGE FROM HEAD TO THIGH
162cm
50
this moves in and out of the gantry aperture
Cradle
51
this is used to latch and unlatch the cradle and table accessories such as the head cradle and table extensions
Latch button
52
is used to deliver oral instructions to the patient.
Speaker
53
placed at the foot of the table to control table movement.
Mat switch
54
used as a patient restriciting device
Velcro straps
55
OPERATOR’S CONSOLE
``` Scan/Display monitor Main Switch Keyboard and Mouse Optical Disk Drives Magnetic Disk Drives ```
56
Used for patient scanning and image display
Scan/Display monitor
57
CT Operating System
Windows | Linux
58
Host Computer
Control of all components Control of data acqusition, processing, display. Data flow direction
59
Image Display, Recording, Storage
Displays image ( output from computer) Provides hard copy of the image Facilitates the storage and retrieval of digital data Communicates images in the network
60
IMAGE RECORDING SYSTEMS (LASER PRINTERS)
Solid state laser printers | Gas laser printers
61
Image Storage Media
Magnetic tapes Magneto-optical disk (MOD) CD

CT Scan (8 decks)

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