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Ultrasonography > ATTENUATION > Flashcards

ATTENUATION Flashcards

1
Q

Other term for acoustic boundaries

A

tissue interface

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2
Q

Difference between acoustic impedance from one to another

A

acoustic boundaries

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3
Q

 Position within the tissue where the values of acoustic impedance change.

A

acoustic boundaries

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4
Q

 Weakening of the sound as it propagates through a medium

A

attenuation

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5
Q

factors affecting attenuation

A

medium and frequency

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6
Q

unit of attenuation

A

decibel

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7
Q

↑ densely packed = _ attenuation

A

high

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8
Q

low frequency = _ penetration = _attenuation

A

high, low

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9
Q

unit of attenuation coefficien

A

dB/cm

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10
Q

For soft tissues, the typical value for attenuation coefficient is

A

0.5 db/cm

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11
Q

Process by which energy in the ultrasound beam is transferred to the propagating medium

A

absorption

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12
Q

converted to heat

A

absorption

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13
Q

concepts that affect attenuation

A

absorption, reflection, refraction, scattering, divergence

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14
Q

 The major interaction of interest for diagnostic ultrasound

A

reflection

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15
Q

 Occurs when two large structures of significantly different acoustic impedance form an interface

A

reflection

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16
Q

sound that hits an acoustic interface

A

incdent energy

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17
Q

reflected beam is called

A

echoes

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18
Q

factor of strength of reflection

A

size of reflector

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19
Q

small difference on the acoustic impedance makes _ echoes

A

small

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20
Q

two types of reflectors

A

speculative and diffuse

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21
Q

occurs when the boundary is smooth and larger than the beam.

A

specular reflector

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22
Q

in specular reflector, the angle of incidence is equal to

A

the angle of reflection

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23
Q

Terms to describe when the beam is perpendicular to the interface

A

normal incidence

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24
Q

Denotes a direction of travel of the incident ultrasound that is
not perpendicular to the boundary between two media

A

oblque incidence

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25
- Incident beam is reflected in many different directions.
diffuse reflector
26
reflecting interface is irregular in shape and its dimensions are smaller than the diameter of the ultrasound beam.
diffuse reflector
27
 Is responsible for providing the internal texture of organs in the image
scattering
28
 Occurs when an ultrasound wave strikes a boundary or interface between 2 small structures and the wave is scattered in different directions
scattering
29
scatter in equal direction
rayleigh scattering
30
redirection of beam
refraction
31
what happens to refraction when angle of incidence is 90 °
none
32
gives the relationship between the angle of incidence and the angle of refraction when a beam of sound passes through an interface between two tissues where the speed of sound is different
snell's law
33
what happens when p2>p1?
angle of transmission is higher than the angle of incidence
34
two requirements for refraction
1. Oblique incidence 2. Different propagation speed on either side of the boundary
35
 Power spread over a large area
divergence
36
↑area = _ divergence = _ intensity
high, low
37
transducers convert _ energy to _ energy
electrical to ultrasound
38
general compositions of transducer
physical housing, electrode, piezoelectric element, backing material, matching layer
39
 Contains all the individual components including the crystals, electrodes, matching later, and backing material.
physical housing
40
 Provides structural support and acts as an electrical and acoustic insulator.
physical housing
41
o Protects patients from electric shock.
outside electrodes
42
other term for outside electrons
grounded electrode
43
inside electrodeis also
live electrode
44
o Abuts against a thick backing block
inside electrode
45
are connected to the UTZ machine which generates the short burst of electrical pulses to excite the crystals
electrodes
46
size of piezoelectric element
6-19mm diameter, 0.22mm thickness
47
most commont type of pizeoelectric element
lead zirconate titanate PZT
48
piezo means
to press
49
 Eliminate the vibrations from the back face and to control the length of vibrations from the face of the crystals.
backing material
50
 Sandwiched between the piezoelectric crystal and the patient
matching layer
51
Region nearest the transducer face, characterized by a highly collimated beam with more uniform intensity
near field
52
aka nearfield
fresnel zone
53
aka far field
fraunhofer zone
54
 Region farthest from the transducer and characterized by the divergence of the beam with great variation in intensity.
far field
55
The location where the beam reaches its minimum diameter
focus points
56
Energy from the transducer that radiates at various angles from the transducer face
Side lobes
57
The arrangement of crystals within the transducer
array
58
types of electronic array
linear, curvilinear, phased
59
PROBE REFERS TO THE PHYSICAL SIZE OF THE PART OF THE ULTRASOUND THAT CONTACTS THE PATIENTS.
foot print
60
THE WIDTH OF THE IMAGE THAT IS SEEN ON THE SCREEN.
field of view
61
 Produces parallel scan lines and has a rectangular field of view
linear
62
linear array is Used to image superficial structures and vessels and therefore operate at frequencies above
4MHz
63
Extensively used for vascular, small parts and musculoskeletal applications.
linear
64
other term for curvilinear
sector
65
Similar to the linear array but the transducer face is formed into a curve (convex in shape) which provides a wide field of view which diverges with depth
curvilinear
66
 Operate at lower frequencies, typically around 3.5 MHz and are best suited to image deep lying structures
curvilinear
67
 Main application are in abdominal and obstetric scanning
curvilinear
68
commonly used in echocardiography
phased
69
similar to curvilinear transducers, they are used to image deep-lying structures and perform trans-cranial investigation
phased
70
smaller and flatter footprint, which allows the users to maneuver more easily between the ribs and small spaces
phased
71
 Transducers designed to enter the body via the vagina, rectum, esophagus or a blood vessel (catheter-mounted type)
invasive
72
use __ for cleaning
transeptics
73
 Improves sound transmission into and out of the patient by eliminating air reflection.
coupling medium
74
coupling medium is also referred to as
aqueous gel

Ultrasonography (5 decks)

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