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Physics > Chapter 18 > Flashcards

Chapter 18 Flashcards

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1
Q

Resolution

A

The ability to image fine detail

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2
Q

____ resolution is better

A

Smaller

Tinier details can be discerned

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3
Q

If two reflectors are not seperated sufficiently they produce

A

Overlapping echoes

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4
Q

Axial resolution aka

A

Longitudinal, radial, depth and range

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5
Q

Axial resolution is

A

Minimum reflector seperation along scan line to produce separate echoes

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6
Q

Axial resolution = ____ mm

A

2mm

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7
Q

Structures place 1 mm apart will be seen as a

A

Single structure

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8
Q

Axial resolution equation

A

AR= SPL/2

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9
Q

The smaller the AR the

A

Better

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10
Q

To improve AR we need to

A

Reduce SPL

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11
Q

Lateral resolution aka

A

Angular, transverse, azimuthal

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12
Q

Lateral resolution is

A

Minimum reflector seperation perpendicular to scan line to produce separate echoes

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13
Q

Lateral resolution occurs when _____=____

A

LR=Wb

Lateral resolution = width of beam

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14
Q

LR=3mm

A

Reflector seperation is less than Wb

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15
Q

LR=1mm

A

BEAM IS NARROWER THAN REFLECTOR SEPERATION

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16
Q

WHAT IS BETTER SMALL OR LARGE LR

A

Smaller

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17
Q

LR is improved by

A

Reducing the wb

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18
Q

Elevation resolution

A

Minimum reflector separation perpendicular to scan plane to produce separate echoes

Operates in 3 dimension

19
Q

Elevational resolution has ____

A

Slice thickness aka section thickness / elevational plane

20
Q

Elevational resolution can preoduce

A

Section thickness artifact aka partial volume artifact

Can fill in cysts or other anechoic structures

21
Q

Poor elevation resolution will show

A

Echoes from outside the intended scan plane

Especially within anechoic structures

22
Q

HOW DO WE FIX elevational resolution artifact

A

THI—> narrower and thinner beam

Less likely to pick up echoes from other plane

Spatial compounding

23
Q

AR is less than _____mm to distinguish two seperate objects

A

1mm

24
Q

Temporal resolution

A

Being able to separate echoes in time

Poor temporal resolution is visualized as lag

25
Q

Contrast resolution

A

Being able to separate two different shades of grey

26
Q

Usefull frequency range

A

2 to 20 MHz

27
Q

Higher freq increase _____ and decrease ________

A

Resolution

Max imaging depth

28
Q

Up to _____ Mhz can be used for ophthalmologic, dermatologic, and intravascular imaging

A

50 MHz

29
Q

Focus can be achieved in the third dimension by

A

Lens or curved elements

30
Q

What is third dimension

A

Perpendicular to the scanning plane

31
Q

How many rows of elements needed for phasing to be applied to focus the third dimension electronically

A

At least three

32
Q

Electronic focusing eliminates the need for

A

A lens or curved elements

33
Q

2D arrays have the ability to _____ and _____ in two dimensions

A

Steer and focus

34
Q

1D array =

A

2D imaging

35
Q

2D array ->

A

3D imaging

36
Q

3D imaging aka

A

Volume imaging

Volumetric scanning

37
Q

3D imaging mainly used for

A

OBSTETRICS AND BREAT

38
Q

4D imaging =

A

3D imaging + time

39
Q

Echoes arriving to the transducer can be ________ as well

A

Delayed or phased

40
Q

Reception steering

A

Listening from a particular direction

41
Q

Dynamic focusing

A

Continual change of the focus with increasing depth

42
Q

Dynamic aperture

A

As the focus continues to change during echo reception, the aperture will increase to maintain a constant focus with

43
Q

Annular arrays

A

Concentric rings
Piezoelectric material carved out in rings

Go from smallest to largest

Not used anymore

Physics (32 decks)

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