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104- Ultrasound Physics > Chapter 11, 15-17, 22 > Flashcards

Chapter 11, 15-17, 22 Flashcards

1
Q

Is old fashioned or modern b-mode bistable?

A

Old-fashioned is bistable. Modern is greyscale.

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2
Q

Is bistable imaging high or low contrast? How does this relate to Dynamic range?

A

Contrast is the range of brilliance in an image. Bistable is high contrast and decreased DR.

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3
Q

What is brightness? Does this change with contrast?

A

Brightness is light or dark. It does not change dynamic range or contrast at all.

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4
Q

What are advantages to digital scan converters?

A

Uniformity, stability, durability, and accuracy

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5
Q

What is a pixel? What is pixel density?

A

Each picture element is one pixel and each is a shade of grey. Pixel density is the numberof pixels per inch.

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6
Q

How is a high pixel density related to spacial resolution?

A

More pixels per inch = high spatial resolution

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7
Q

What is a bit?

A

the smallest amount of computer memory. Either 0 or 1

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8
Q

What is a byte?

A

A group of 8 bits. Example 01100101

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9
Q

What is a word?

A

two bytes or 16 bits.

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10
Q

A higher number of bits per pixel creates more shades of grey, How does this affect contrast resolution.

A

It imporoves contrast resolution.

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11
Q

How are bits mathematically related to shades of grey?

A

They are exponential. 3 bits = 8 shades because 2 to the 3rd power = 8

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12
Q

Computer memory, grey shades, and contrast resolution have to do with..?

A

bits

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12
Q

Image element, image detail, and spatial resolution have to do with..?

A

pixels

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13
Q

TGC, write magnification, and log compression are related to what kind of processing

A

Pre-Processing

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14
Q

black and white inversion, read magnification, and contrast variation are related to which type of processing

A

Post-Processing

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15
Q

What kind of magnification expands the chosen ROI and has the same number of pixels as the original image?

A

Read magnification- zoom after the image is stored. It cannot be changed.

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16
Q

What kind of magnification re-assigns pixels in the ROI? Does this create a better or worse image?

A

Write magnification. It is a better image because more pixels are assigned in the area, they are not expanded, since that is the only area being processed.

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17
Q

Which type of magnification improves spatial and temporal resolution?

A

Write magnification

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18
Q

A method of reporting the extent to which a signal can vary and still be accurately measured is called..?

A

Dynamic Range

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19
Q

explain dynamic range

A

Comparison or ratio between the largest and smallest signals or the number of available choices

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20
Q

Signals that are too weak to be accurately displayed are called..?

A

below the threshold

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21
Q

Signals that are too strong to be accurately displayed are called..?

A

saturating the system

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22
Q

Does dynamic range increase or decrease as it is processed? What does this mean for components that are processed earlier?

A

It decreases. Components early on have a wider dynamic range.

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23
Q

How do you calculate a component’s dynamic range?

A

Divide the bigger voltage by the smaller. For every zero, count a 20dB change.

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24
What are the three rules of the compression of dynamic range?
Largest number remains largest, lowest remains lowest, and range between is reduced
25
How are bistable images related to dynamic range?
Bistable images are high contrast and therefore have a narrow dynamic range.
26
What is coded excitation? How is it safer?
Creating longer pulses with a large range of frequencies in the pulser. The energy is distributed over a large range, so the peak intensity is within safe limits.
27
What are the benefits of coded excitation?
It improves axial, spatial, and contrast resolutions. it also penetrates deeper and improves SNR
28
What is spatial compounding?
Using multiple angles of sound beams to produce a single image.
29
What are the advantages and disadvantages of spatial compounding?
It reduces speckle and shadows, but it also reduces the frame rate and temporal resolution.
30
What is frequency compounding
a reflected signal is split into several sub-bands of frequencies. Each sub-band produces an image which are combined to make one image.
31
What are advantages of frequency compounding?
It reduces noise and speckle and SNR
32
What is edge enhancement
A processing method that makes images sharper by adding contrast immediately around an image's edge.
33
What is temporal compounding, persistance, or temporal averaging
information from older images is displayed and overlapped onto the current frame.
34
What are the advantages and disadvantages of temporal compounding?
a smoother image, decreased noise, improved SNR, but it also decreases frame rate and temporal resolution
35
what is fill-in interpolation
computer program predicts the grey scale level of the missing data between the scan lines during pre-processing.
36
What are the advantages of fill-in interpolation
increased line density and spatial resolution
37
Elastography estimates tissue stiffness. How is this possible?
Images are related to the mechanical properties of tissue and tissues deform slightly with force.
38
What is Picture Archival and Communications System?
Archival system that stores ultrasound images and medical information on a large computer network
39
What is Digital Imaging and Computers in Medicine
Set of rules that allows imaging systems to share information on a network
40
What are advantages and disadvantages of paper media such as written charts?
it's portable and doesn't require a computer to read, but it is difficult to store and cannot display moving images.
41
What are advantages and disadvantages of magnetic media such as CDs?
They can store large amounts of data including videos and color. They can sometimes be erased by strong magnetic fields.
42
What are advantages and disadvantages of chemically mediated photographs or film?
They are high resolution and can produce color. They are difficult to store, require chemical processing, and can be contaminated which could create artifacts.
43
What are advantages and disadvantages of optical media like laser or compact discs?
They store large amounts of data and cannot be erased by magnetic fields. They require a display system.
44
What is the relationship between fundamental and harmonic frequency?
Fundamental frequency is created by the transducer and harmonic is twice that frequency.
45
What is tissue harmonics created by?
non-linear behavior during transmission.
46
What are the 5 requirements of contrast harmonics?
Safe, metabolically inert, long lasting, strong reflector, small enough to pass through capillaries
47
Where in the body are tissue harmonics created?
They are created deep in the body and get a "free ride" through superficial structures.
48
What is contrast harmonics created by?
non-linear behavior of microbubbles during reflection.
49
How does high frequency relate to mechanical index and pressure?
High frequency has a lower MI and small variation of pressure.
50
How does a high mechanical index relate to bubble disruption?
the bubble disruption creates more harmonics.
51
What is quality assurance
A medical and legal necessity. Routine evaluation of an ultrasound system to guarantee optimal image quality.
52
What are the 4 requirements of quality assurance?
assessment of system components, repairs, preventative maintenance, record keeping
53
What is the speed of sound in an AIUM 100 mm Test Object?
1540 m/s
54
What is the dead zone?
The area closest to the transducer where the images are innaccurate.
55
what does slice thickness determine?
elevational resolution
56
What is sensitivity of an ultrasound system?
the system's ability to display low-level echoes
57
What is the difference between normal and maximum sensitivity?
Normal sensitivity is where the pins and masses in a test phantoms are diaplayed. Maximum is where output power and amplification are sent to the maximum level.
58
Which transducer type has a thinner dead zone and is therefore better for superficial scanning?
High frequency transducers
59
What is range accuracy
the vertical depth calibration accuracy placing reflectors parallel with the beam.
60
what is horizontal accuracy?
system's accuracy placing reflectors perpendicular with the beam.
61
What is distance measurement accuracy?
the evaluation of distance that should be checked in vertical and horizontal directions
62
What is amplitude or A-Mode imaging?
a series of upward spikes as the reflection returns. strong echoes create taller peaks.
63
What is brightness or B-Mode imaging?
A line of dots of varying brightness depending on the strength of the reflection. B-mode is the first form of grey scale imaging
64
What is motion or M-Mode imaging?
a group of horizontal wavy lines that show motion over time.

104- Ultrasound Physics (8 decks)

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