Chapter 15 Flashcards
(132 cards)
1
Q
Images composed of only 2 shdes: black and white
A
Bistable
2
Q
_ presents multiple levels of brightness (white, light gray, medium gray, etc.)
A
Gray scale
3
Q
In gray scale, the numerous levels allows the system to _
A
assign different gray shades to different echo amplitudes and differentiate biologic tissues of different reflectivity.
4
Q
Two user controls on video monitors can
alter characteristics of displayed images
A
- Contrast
2. Brightness
5
Q
Determines the range of brilliancies within the displayed image.
A
Contrast
6
Q
Bistable images (only black and white) are _ contrast
A
High
7
Q
Determines the brilliance of the displayed image
A
Brightness
8
Q
Functions of scan convertors
A
Store digital image information to later display it.
Change format of data; translate data
9
Q
Scan converters _ and then later _
A
Store information
Display it
10
Q
Storage of information is called
A
Writing
11
Q
Image data is _ for display on the monitor.
A
“read” from the scan converter
12
Q
scan convertors used to be _, now they use _
A
Analog
Digital technology
13
Q
scan converters:
Ultrasound information is obtained from the body from
A
multiple scan lines (spokes)
14
Q
Monitors display video information as
A
Horizontal lines
15
Q
Scan converter translates the information from _ format into the _ format
A
“Spoke”
Video
16
Q
Data stored in the scan converter can be altered between
A
the writing process and the reading process.
17
Q
_ numbers are real world numbers
found in our everyday lives
A
Analog
18
Q
Numbers with unlimited and continuous range of values
A
Analog
19
Q
_ numbers are associated with computer devices and have discrete values
A
Digital
20
Q
_ scan converter:
Funnel-shaped vacuum tube with an electron gun
located within its smaller end.
A
Analog
21
Q
Analog Scan Converter:
_ containing the image information are shot out of the electron gun
A
Electrons
22
Q
Analog Scan Converter:
The larger end of the tube contains
A
a dielectric matrix or silicon wafer.
23
Q
Analog scan converter:
The electrons strike the _ and are _
A
Matrix
Stored
24
Q
Analog scan converter:
The matrix is divided into _
A
Millions of tiny storage elements
25
Analog scan converter:
| The stored electrons are _
Read to retrieve the image info
26
Analog Scan Converter has _ spatial resolution
Excellent
26
Limitations of analog scan converteers
Image fade – stored charges on the silicon wafer dissipate
over time
Image flicker – caused by switching between read and wrote modes
Instability – picture quality depends on many different factors
Deterioration – image degrades as the device ages
27
_ scan converters use computer technology to convert images into numbers (_)
Digital
Digitizing
28
Digital scan converter:
| Image is stored in _ as _
Computer memory
Series of zeroes and ones
29
Digital scan converters:
| The numerical representation of the image is _ and then _
Processed
then retranslated into an image displayed on a monitor.
29
Advantages of digital scan converters:
```
Uniformity – consistent gray scale quality throughout the image
Stability – does not fade or drift
Durability
Speed
Accuracy
```
29
Two important elements of digital scan converters
1. Pixel
| 2. bit
30
Smallest building block of a digital picture
Pixel
31
At any instant in time, the entire pixel is _
A single shade of gray
31
number of pixel elements per inch
Pixel density
31
```
Low pixel density:
_ pixels per inch
_ pixels
_ detailed image
_ spatial resolution
```
Few
Larger
Less
Lower
32
```
High pixel density:
_ pixels per inch
_ pixels
_ detailed image
_ spatial resolution
```
Many
Smaller
More
Higher
33
Smallest amount of computer memory
Bit
34
A bit is _, has a value of _
Bistable
| Either 0 or 1
35
a group of bits; simply a series of zeroes and ones.
Binary number
36
group of eight bits of computer memory
Byte
37
Two bytes (16) bits
Word
37
Each pixel’s shade of gray is determined by _
the cluster of bits assigned to it.
37
Fewer bits per pixel:
_ shades of gray
_ contrast resolution
Fewer
Degraded
38
More bits per pixel:
_ shades of gray
_ contrast resolution
More
| Improved
39
To determine the number of gray shades that can be represented by a cluster of bits, _
multiply the number 2 by itself the same number of times there are bits: 2^n
40
Number of bits:5
| Number of shades: _
32
41
digital information is _ susceptible to noise contamination
Less
42
Information is taken from the transducer in _ form. It is then changed into _ form for _. It then must be _ for display.
Analog
Digital
Computer storage
Analog
43
Step 1. electrical signals created by the transducer during reception are converted from _ to _ form by the _
Analog
Digital
Analog to digital converter
44
Step 2:
| The digital information is stored in the _. Any processing of the reflected signals before storage is called _
scan converter’s computer memory
Preprocessing
44
Step 3:
The image information (digital form) is processed by the _. Any processing after storage in the digital scan converter is called
US systems computer
Postprocessing
45
Step 4:
| Digital signals are translated _ to be displayed on the analog display devices by a
back into analog form
| digital-to- analog (D-to-A) converter.
46
Step 5:
| The signal is now in _ form and can be displayed on the analog display.
Analog
46
Modern flat-panels are _ display devices
Digital
47
cases of digital display devices, step _ is unnecessary.
4
48
the manipulation of image data before
| storage in the scan converter.
Preprocessing
49
Preprocessing is controlled by _
Sonographer
50
_ alters image data forever and cannot be reversed or undone
Preprocessing
51
manipulation of image data after storage in the scan converter
Postprocessing
51
Postprocessing is controlled by
Sonographer
52
Pre or postprocessing:
Changes can be reversed
Alterations to a frozen image
Postprocessing
52
Functions of Image Processor:
```
◼ Preprocessing
◼ Persistance
◼ 3-D acquisition
◼ Storing imaging frames
◼ Cine loop
◼ Post processing
◼ Grayscale
◼ 3-D presentation
◼ D-A conversion
```
52
Enlarging a portion of the image to fill the entire screen
Magnification/zoom
53
Selected part of image is called
Region of interest (ROI)
54
Two types of magnification
Read
| Write
55
_ magnification occurs after the image data is stored in the scan converter
Read
56
Read magnification: 3 steps:
1. US System scans the anatomy
2. Image is converted from analog to digital form and stored in the scan converter
3. Sonographer identifies the ROI and the system reads and displays only the original data that pertains to that area. The ROI is not rescanned.
56
Read magnification:
| Number of pixels or scan lines in the magnified image is
the same as the original image
57
Does spatial resolution change with read magnification
No
57
Read magnification:
| Are the pixels larger, smaller, or the same size in the zoomed image
Larger
58
_ magnification can be used on a frozen image
Read
59
Is read magnification pre or postprocessing
Postprocessing
60
_ magnification is applied during data acquisition, before data is stored in the scan converter
Write
60
Write magnification: 4 steps:
1. The US system scans the anatomy and creates an image
2. Image is converted from analog to digital and is stored in the scan converter
3. Sonographer identifies the ROI. The US system then discards all the existing data in the scan converter
4. The US System then rescans only the region of interest and writes new data into the scan converter.
61
Write magnification: the image used to identify the _ is discarded and _ is acquired
ROI
| All new image info
61
_ magnification:
| The number of pixels or scan lines in the ROI image is greater than that in the ROI’s portion of the original image
Write
62
_ magnification has increased number of pixels which improves _
Write
| Spatial resolution for the ROI
62
Can write magnification be used on a frozen image?
No
63
Is write magnification pre or postprocessing
Preprocessing
64
Sophisticated method of improving image quality. Developed within the context of bioeffects due to high intensity levels of short sound pulses
Coded excitation
65
Coded excitation creates _ sound pulses containing _.
Very long
| A wide range of frequencies
66
Long pulses distribute energy _
Over a broad frequency range
67
Does coded excitation improve penetration
Yes
68
Coded excitation occurs in
The pulser
68
Special mathematical techniques alter the long reflected pulses into a form suitable for high image quality
Coded excitation
68
The coding of the excitation _ the pulse mathematically and _ resolution
Shortens
Improves
69
Produces image with a wider field of view
Panoramic imaging
70
Panoramic imaging is achieved by
sliding transducer parallel to the scan plane
| [extending the scan plane]
71
Panoramic imaging: old information from previous frame are _ and _
Retained
| New echoes are added to the image in the same direction the scan plane is moving
71
Is panoramic imaging pre or postprocessing
Preprocessing
71
A method of using sonographic information from several different imaging angles to produce a single image
Spatial compounding
72
_ compounding:
| Number of frames and steering angles varies
Spatial
73
Spatial compounding has _ frames= _ compound image quality
More
| Better
74
Does spatial compounding reduce speckle and shadowing artifact?
Yes
74
Spatial compounding reduces _
Speckle and shadowing artifacts
74
Speckle reduction improves
dynamic range and contrast resolution.
75
_ compounding reduces speckle artifact and noise in ultrasound images
Frequency
76
All reflected sound pulses contain
a large range of frequencies.
76
Frequency compounding:
| Reflected signal is divided into _ and an image is created from_. Images from the sub-bands are then _
sub-bands of limited frequencies
Each sub-band
combined into a single image.
77
Frequency compounding: Noise components of the reflections are _ and _
different for each sub-band
| Noise is reduced when they are combined
78
Image processing method that
| makes pictures look sharper
Edge enhancement
79
Edge enhancement: the computer identifies and _
emphasizes sharp edge boundaries in the image
80
Increases the image contrast in the area immediately around the edge
Edge enhancement
81
Creates subtle bright and dark highlights on either side of these boundaries to make them appear more defined
Edge enhancement
82
An image processing technique that continues to display information from older images. A number of previous frames are superimposed on the most current frame.
Temporal compounding
83
Temporal compounding creates _
smoother image with reduced noise and improved image quality
84
Temporal compounding aka
persistence, temporal averaging
85
Temporal compounding: reduction of _
Frame rate/temporal resolution
85
Temporal compounding is most effective with
Slowly moving structures
86
With sector shaped images, the scan lines _. This creates _.
Separate at increasing depths.
| Gaps between the scan lines
87
_ method of constructing new simulated data points to fill in the gaps.
Interpolation
88
Fill in interpolation: the know gray scale level of neighboring pixels are used to _
Predict the missing info
88
Is fill in interpolation pre or postprocessing
Preprocessing
88
Fill in interpolation: _ resolution is improved
Spatial
89
Dynamic technique that produces images from sound reflections in an entirely new way.
Elastography
90
Elastography is related to _. Tissue will _
the mechanical properties of the tissue
| Deform differently following the application of a force
91
Elastography: _ are obtained and combined with US reflections into images called _
Estimates of tissue stiffness
| Elastograms
91
_ is potential as a complementary tool for the diagnosis of cancer
Elastography
92
2 [general] methods for performing elastography
Strain elastography and shear weave elastography
93
Strain elastography:
_ dependent
Measures _
Qualitative or quantitative?
Operator
Tissue strain
Qualitative
94
Aka transient elastography
Shear wave elastography
94
Shear wave elastography:
Compressions applied by _
Measures _
Qualitative or quantitative?
Sound pulse
Stiffness
Quantitative
94
PACS
Picture Archiving and Communications System
94
Digital ultrasound lab where images and additional medical information are digitized and stored on a computer network
PACS
95
3 major advantages of PACS
1. Virtually instant access to archived studies
2. No degradation of data
3. “store and forward” telemedicine – can electronically transmit images and reports to remote sites
96
_ are the primary digital storage devices used in PACS
Computer hard drives
97
DICOM
Digital Imaging and Computers in Medicine
97
A set of rules that allows imaging systems to share information on a network
DICOM
98
If an US system adheres to _, the system can successfully connect to a PACS network
DICOM standards
99
DICOM guarantees _
that all devices developed in the future will work with PACS as well.
100
Developed within the context of bioeffects
Coded excitation
