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Sciences Fall '13 > Ch.28 > Flashcards

Ch.28 Flashcards

1
Q

This is made up of individual picture elements each designed by its column and row number

A

Digital image Matrix

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2
Q

This determines the spatial resolution.

A

Pixel size

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3
Q

The smaller the pixels visibility =?

A

smaller structures, increased recorded detail

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4
Q

Nuclear medicine = what pixels? Ultrasound?

A
  • -64x64

- -128x128

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5
Q

A matrix is made up of ____ within each column/row?

A

pixels

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6
Q

MRI and CT =what pixels? DR and CR?

A
  • -512x512

- 1024x1024

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7
Q

This is a measure of spatial resolution or image sharpness.

A

Spatial Frequency

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8
Q

Spatial Frequency is measured with what units?

A

Line pairs per millimeter (LP/mm)

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9
Q

How many pixels are required to record a line pair from a resolution template?

A

at least 2

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10
Q

When pixel size is reduced to .1mm actual resolution is what?

A

6 LP/mm

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11
Q

What is the formula relating spatial frequency to the pixel size of the image acquisition system.

A

SF= 1/2 (PS)

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12
Q

This is the portion of the image receptor plate that contains relevant anatomical information and is displayed on the monitor screen. (Size of collimation you use)

A

Displayed Field of View

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13
Q

Since both small and large anatomy are displayed on the monitor using the same matrix, a _____ (smaller, larger) field of view will consists of more pixels in a given display area.

A

Smaller

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14
Q

What is the pixel size formula?

A

PS= FOV/matrix

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15
Q

What are the 3 steps in digitizing an analog image?

A
  1. Scanning
  2. Sampling
  3. Quantizing
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16
Q

What is scanning in an analog image

A

Image is divided up into matrix of pixel cells

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17
Q

Sampling is what in an analog image?

A

Intensity of light (or X-rays) is measured for each cell

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18
Q

Quantizing is what in an analog image?

A

A discrete numerical value is assigned to each cell from a predesignated gray scale.

19
Q

This is the maximum range of pixel values the computer can store and is expressed as an exponent of base 2.

A

Bit Depth-Number of bits per pixel
6 bits deep=64 values (2^6)
7 bits deep= 128(2^7)
8 bits deep = 256 (2^8)

20
Q

The human eye can discern how many levels of brightness?

21
Q

This is the number of gray shades with which each pixel can be represented by the system.

A

Dynamic Range

22
Q

This is the range of pixel values actually present in a displayed image.

A

Gray Scale

23
Q

When many thousands of images are stored, the large file size of medical images can become a problem for the PACS administrator

24
Q

What is the formula for File Size?

A

File Size= Matrix Size x Bit Depth

25
This is the ratio or percentage of original x-ray beam intensity absorbed by a particular tissue area in the patient.
Attenuation Coefficient
26
This can be changes by window level or by applying a different procedure algorithm.
Resolution
27
This type of Imaging system has a maximum subject detectability of 10%.
General Film Screen
28
This type of imaging system has a maximum subject contrast detectability of 1%.
Computerized Radiography
29
If a cassette is run without a name assignment it will automatically be processed as what type of procedure?
A chest
30
Reprocessing the image after the initial recording by lower the algorithm to change the gray scale will make what structures better visualized?
soft tissue
31
What are special features available in post processing?
Rotation, Black bone, Masking, edge enhancement
32
This is the overall brightness of the image called center in some modalities.
Window level
33
Increasing the window level will do what to the brightness of the image?
Decrease the brightness, image becomes darker.
34
Decreasing the window level will do what to the brightness of the image?
Increases the brightness, image becomes darker
35
This controls the length of the gray scale in the image.
Window Width
36
Increasing window width will do what to the image?
lengthens the gray scale but does not alter the average brightness.
37
Decreasing window width will do what to the image?
Shortens gray scale but does not alter the average brightness.
38
In a PAC system the control computer allows universal access to images through what? and uses this to allow access to doctors homes and offices?
LANS- Local Area Networks | WANS- Wide Area Networks
39
The LAN and WAN communicates with what systems?
RIS and HIS
40
This was established in the 1970s to ensure compatibility between all components of PACS by sharing a common high level computer language. It specifies only the transmission behavior of the various devices not the specific architecture or terminology between different makes.
Dicom Standard
41
This distributes copies of the same data files across several computer hard drives which are independent of each other to assure that medical information or images are not lost by electrical failure file corruption or software failure in a single system.
Raid System
42
What are the 3- essential components of lasers?
1. Medium providing the atoms to be stimulated 2. A power source or pumping source to stimulate the atoms 3. A resonant cavity to amplify and synchronize the lightwaves.
43
What is the medium of a laser made of?
helium neon gas
44
What reasons are there lasers in medical imaging?
- Reading and writing of optical discs for storage - CR readers and processors - Laser film digitizers and printers

Sciences Fall '13 (7 decks)

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