CT Flashcards

1
Q

proposed a method to represent a single slice of the body on the radiographic film (topography)

A

Allesandro Vallebona

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2
Q

first demonstrated CT technique

A

Godfrey Newboid Hounsfield

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3
Q

1st CT scan Machine; 180 translation/ 1 degree rotation

A

EMI Scanner

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4
Q

1st CT system that could make an images of any part of the body; did not require water tank

A

ACTA

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5
Q

slice/section

A

tomos

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6
Q

produces sagittal and coronal images

A

axial tomography

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7
Q

produces transverse images

A

computed tomography

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8
Q

it refers to movement of source-detector assembly across the px; results in a projection

A

translation or sweep

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9
Q

represents the attenuation pattern of the px profile

A

projection

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10
Q

has a pencil beam and one detector; 5 mins scan time

A

1st Generation CT

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11
Q

has a narrow fan beam and has multiple detectors; bow tie filter

A

second generation CT

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12
Q

has a wide fan beam

A

third generation CT

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13
Q

with a detector ring

A

fourth generation CT

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14
Q

electron beam CT

A

fifth generation CT

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15
Q

helical (spiral) CT

A

sixth generation CT

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16
Q

multidetector row CT

A

seventh generation CT

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17
Q

3 major components CT

A
  1. Gantry
  2. Operating Console
  3. Computer
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18
Q

Gantry subsystems

A
  1. x-ray tube
  2. detector array
  3. HVG
  4. px couch
  5. mechanical support
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19
Q

group of detectors

A

detector array

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20
Q

gas detectors

A
  1. proportional counter
  2. ionization chamber
  3. geiger-muller counter
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21
Q

scintillation detectors

A
  1. sodium iodide
  2. BGO, CsI
  3. CdWO4; special ceramics
22
Q

photodiode

A

converts light into electrical signal

23
Q

3 factors; Detector efficiency

A
  1. geometric efficiency
  2. conversion efficiency
  3. quantum efficiency
24
Q

area of the detectors sensitive to radiation as a fraction of the total exposed area

A

geometric efficiency

25
Q

ability to accurately convert absorbed x-ray signal to electrical signal

A

conversion efficiency

26
Q

fraction of incident x-rays on the detector are absorbed and contribute to the measured signal

A

quantum efficiency

27
Q

refers to the ability with which the detector obtains photons that have passed through the px

A

capture efficiency

28
Q

refers to the number of photons absorbed by the detector

A

absorption efficiency

29
Q

ratio of maximum signal to minimal signal the detectors can measure

A

dynamic range

30
Q

DAS consists of:

A

amplifier
ADC
multiplexer
preamplifier
logarithmic
integrator

31
Q

px couch is made of

A

carbon fiber

31
Q

collimation purpose

A
  1. reduce px dose
  2. improve image contrast
32
Q

to decrease px dose

A

prepx collimator

33
Q

to improve image contrast

A

predetector collimator

34
Q

heart of the computer

A

microprocessor and primary memory

35
Q

electromechanical device that conducts electricity and electrical signals thru rings and brushes

A

slip ring

36
Q

made of silver graphite alloy; used as sliding contact

A

brushes

37
Q

picture element

A

pixel

38
Q

volume element

A

voxel

39
Q

the numeric information contained in each pixel

A

CT Number/ Hounsfield Units

40
Q

rows and columns of pixels contained in digital image

A

Matrix

41
Q

the diameter of the image reconstruction

A

FOV

42
Q

principal algorithm used in CT scan

A

Filtered back projection

43
Q

3 3D MPR algorithms

A

“SM”
SSD (shaded surface display)
SVD (shaded volume display)
MIP (maximum intensity projection)

44
Q

5 principal characteristics of CT image

A
  1. SR
  2. CR
  3. noise
  4. linearity
  5. uniformity
45
Q

factors affecting SR

A
  1. PS
  2. ST
  3. VS
  4. design of prepx and predetector collimator
  5. DS
46
Q

physics based artifacts

A
  1. beam hardening
  2. partial volume
  3. photon starvation
  4. undersampling
47
Q

beam hardening artifacts

A

“sc”
streaking artifact
cupping artifact

occurs at bone and metal implants

compensation: beam hardening correction

48
Q

partial volume artifacts “pva”

A

critical region: posterior cranial fossa

compensation: thin slice selection/incrementation

49
Q

patient-based artifacts

A

“IM”
incomplete projection
motion
metallic materials

50
Q

scanned based artifact

A

ring artifact

51
Q

helical and MS artifacts

A

cone beam = helical
stair-step = MSCT
Zebra or windmill = MSCT