Knobology Flashcards

1
Q

Velocity of sound in soft tissue

A

1540 m/s

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2
Q

M-mode

A

Brightness mode vs time

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3
Q

2D grayscale imaging

A

Multiple M-mode scan lines spliced together to form a sector

Multiple pulses from multiple crystals

Phased array allows electronic focusing and beam steering

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4
Q

3D Imaging

A

Pyramid of M-mode scan lines

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5
Q

Wave properties — time

A

Period — amount of time to complete a single cycle

Frequency — number of cycles / second
• u/s > 20 KHz
•increased frequency —> better axial resolution (decreased SPL)
•increased frequency —> more attenuation

Pulse duration — time to complete an entire pulse
•PD = period x # cycles

Pulse repetition period — time from beginning of one pulse to beginning of another pulse
•includes pulse duration and listening time
•depends on depth of object

Pulse repetition frequency — # pulses / second
•inverse of PRP
•important for temporal resolution
•determines the Nyquist limit (1/2 PRF)

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6
Q

Wave properties — length (distance)

A

Wavelength — length of a single cycle

Spatial pulse length — length of an entire pulse
•determines axial resolution —> 1/2 SPL
•”LARD” - longitudinal, axial, radial, range, depth

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7
Q

Wave properties — strength

A

Amplitude — difference between the average and max acoustic variable

Power — amount of work the u/s beam can do

Intensity — amount of power per unit area
•determines the bio effects of u/s

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8
Q

Spatial resolution

A

Ability to discern the correct space/place of a structure

•axial (pulse length) > lateral (beam width) > elevational (beam height)

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9
Q

Temporal resolution

A

Ability to accurately determine the position of a structure at a particular instant in time

Determined by:
•how much something moves
•frame rate = # frames / second
# pulses / scan line
Line density
Image depth (listening time)
Sector width
PRF proportional to frame rate — as PRF increases the temporal resolution improves
Nyquist limit = 1/2 PRF
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10
Q

Gain

A

Amplifies returning signals

•post processing function

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11
Q

Power

A

Transducer output

•increases amount of energy transmitted to the body

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12
Q

Time/depth gain compensation

A

Compensation for attenuation with depth

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13
Q

Lateral gain compensation

A

Compensation for attenuation laterally

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14
Q

Compression

A

Compresses the range of signals and decreases the dynamic range
•dynamic range is the inverse of compression and can be thought of as the # shades of gray

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15
Q

Focus

A

When beam is narrowest there is the best lateral resolution

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