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ct scan with field exposure > M Part I > Flashcards

M Part I Flashcards

1
Q

A precise step to be performed in a specific order to solve a problem
Basis for most computer programming

A

Algorithm

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2
Q

A mathematical method of creating missing data

A

Interpolation

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3
Q

Two types of data

A

Raw data
Image data

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4
Q

-have assigned value
-includes all measurements detailed from the detector array
-requires more storage space

A

Raw data

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5
Q

The reconstruction that is automatically produced during scanning

A

Prospective Reconstruction

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6
Q

The process of generating new image after scanning

A

Retrospective Reconstruction

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7
Q

Image data is also known as [..]

A

Reconstructed Data

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8
Q

Convolved data that have been back-projected into the image matrix to create CT images displayed on a monitor
Various digital filters are available to suppress noise and improved data

A

Image data

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9
Q

Factors that affect attenuation

A

Atomic no.
POI thickness
Energy of x-ray

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10
Q

Those which result once the computer has processed the raw data
One HU is assigned to each pixel

A

Image Data

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11
Q

IF ONLY IMAGE DATA IS AVAILABLE, DATA MANIPULATION IS [..]

A

LIMITED

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12
Q

Reconstruction that can make slices thinner/thicker using raw data

A

Retrospective Reconstruction

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13
Q

The part of the beam that falls one irection

A

Ray

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14
Q

The detector senses each arriving ray and measures how much of the beam has been attenuated

A

Ray Sum

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15
Q

A complete set of ray sums

A

View

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16
Q

The system accounts for attenuation properties of each ray sum and correlates it to the position of the ray

A

Attenuation profile

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17
Q

Reconstruction Algorithms (3)

A

Back Projection
Filtered Back Projection
Adaptive Statistical Iterative Reconstruction

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18
Q

Other names for Back Projecion

A

Summation Method/Linear Superposition Method

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19
Q

PROCESS of Back projection

A

Ray sum data acquired from each projection
Projected back onto the matrix

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20
Q

PROBLEM of Back Projection

A
  1. Low spatial resolution
  2. Bluming and produces star pattern artifact
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21
Q

Introduced to address the star pattern artifact

A

Filtered Back Projection

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22
Q

Process of applying a filter function to an attenuation profile

A

Convolution/Kernel Elements

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23
Q

Used in filtered back projection of reduce statistical noise

A

Fouler Theory

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24
Q

FILTER FUNCTIONS CAN ONLY BE APPLIED TO [..]

A

RAW DATA

25
Q

Starts with an assumption and compares this assumption with measured values, makes corrections to bring the two in agreement

A

Adaptive Statistical Iterative Reconstruction

26
Q

Used in an iterative manner to extract additional image clarity and suppress noise

A

Statistical noise profiles

27
Q

[adv] Adaptive Statistical Iterative Reconstruction

A

Improved image quality
Reduced image noise

28
Q

[importance] image display

A

Diff brightness- see pathologies in different configurations

29
Q

Patients couch inserted then rotate (in-out)

A

Step and Shoot Scanning (1980s)

30
Q

Continuous patient couch moving in while gantry rotates

A

Spiral/Helical CT Scanning

31
Q

Used and defined as table distance travelled in one 360 deg rotation divided by beam collimation

A

Pitch

32
Q

Refers to table movement (speed) in going in the gantry

A

Table feed per rotation

33
Q

Pitch [formula]

A

Table feed per rotation/section width

34
Q

[pitch] distance is enough
Can adjust to rotation of X-ray tube

A

Pitch I

35
Q

X-ray beam are contiguous for adjacent rotations

A

P = 1.0

36
Q

X-ray beams are not contiguous for adjacent rotations [gaps in x-ray helix]

A

P>1.0

37
Q

There is x-ray beam overlap

A

P<1.0

38
Q

Getting data from same structure more than once

A

Oversampling

39
Q

[disadv,adv] oversampling

A

Disadv: Increase pt dose
Adv: Increase image quality due to increase SNR

40
Q

Oversampling application

A

Facial bones
Paranasal bones - frontal, sphenoidal, ethmoidal, maxillary

41
Q

[adv,disadv] Of undersampling

A

Disadv. Lower pt does
Adv. decreased image quality due to decreased SNR, more artifact

42
Q

Undersampling application

A

Trauma
CT angiography (contrast quickly flushed

43
Q

Measure of the range of the CT number the image contains

A

Window Width (WW)

44
Q

ALL VALUES HIGHER THAN SELECTED VALUES WILL APPEAR [..]

A

WHITE

45
Q

ALL VALUES SELECTED LOWER THAN THE SELECTED VALUES WITHH APPEAR [..]

A

BLACK

46
Q

Term for increasing window width

A

Widening the width

47
Q

Selects which Hounsfield values are displayed as shades of gray
(Center of WW)
Roughly same value as tissue of interest

A

Window Level

48
Q

Manipulation of the window width and level to optimize contrast

A

Windowing

49
Q

COMPUTER CAN ASSIGN OVER [..] HU

A

2000

50
Q

COMPUTER CAN DISPLAY [..] SHADES OF GRAY

A

256

51
Q

NAKD EYE CAN ONLY DISTINGUISH ROUGHLY LESS THAN [..] SHADES OF GRY

A

40

52
Q

Best used in areas of acute differing values [lungs, air and vessels is side by side]

A

Wide window width

53
Q

excellent when examining areas of similar attenuation [soft tissue]

A

Narrow Window Width

54
Q

WW UL AND LL FORMULA

A

UL = WL + (WW/2)
LL = WL - (WW/2)

55
Q

Helpful in reporting size of abnormality
Essential for placement of biopsy needle or drainage apparatus

A

Distance Measurement

56
Q

Used to make original image appear larger to see relevant data
Clarify margins of abnormality

A

Image Magnification

57
Q

Graphical display showing how frequently a range of CT no occurs within an area

A

Histogram

58
Q

Allows more than one image to be displayed in a single frame

A

Multiple image display

ct scan with field exposure (5 decks)

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