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Ultrasound Flashcards

1
Q

Definition of deep heating agent

A

 Capable of causing tissue temperature change at depths of 2 cm or >
 Capable of causing tissue temperature changes in deep tissues without causing excessive overheating of superficial tissues

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2
Q

models for deep heating agents

A

 Ultrasound
 Shortwave diathermy
 Microwave

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3
Q

definition of ultrasound

A

A molecule set to vibrate will cause its neighbor to vibrate also; the neighbors will then cause their neighbors to vibrate and so on until the vibration has passed through the entire material (propagation of vibratory motion is sound)

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4
Q

what really iiiissssss ultrasound

A

soundwaves occurring at a frequency greater than can be heard by the human ear

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5
Q

compression phase

A

molecules compress

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6
Q

rarefaction

A

molecules spread out again

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7
Q

sound wave motion/ dispersion - longitudinal wave

A

Molecules are compressed in the direction the wave travels from its source

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8
Q

sound wave motion/dispersion - shear wave

A

Molecule movement is at a right angle or perpendicular to the source of the wave
Dominant in liquid

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9
Q

1 cycle of ultrasound =

A

1 compression phase + 1 rarefaction phase

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10
Q

definition of attenuation

A

the reduction of energy as it travels through the medium

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11
Q

scattering

A

 Deflection of soundwave from its path by reflection/refraction at interfaces
 Overall effect is that US beam is decreased in intensity the deeper it passes

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12
Q

what happens as a sound wave hits a boundary

A
  • it loses energy
  • some of this energy loss is due to reflection of the sound wave
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13
Q

reflection

A

redirection of an incident beam away from a
reflecting surface at an angle equal and opposite to the angle of incidence

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14
Q

refraction

A

The redirection of a wave at an interface continuing through the tissue at a different angle than the angle of incidence

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15
Q

standing wave

A

Incoming and reflected waves hit each other
- why it hurts when you stop moving

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16
Q

absorption

A

 US is absorbed by tissue, and converted to heat at that point
 The lower the frequency of the soundwave the lower the absorption
 Velocity increases as material density increases

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17
Q

3 MHz

A

most sound waves are absorbed within the 1st cm of penetration

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18
Q

1 MHz

A

most sound waves are absorbed within the first 5 cm of penetration

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19
Q

Absorption of 1 MHz from least to most

A

blood
fat
muscle
blood vessel
skin
tendons
cartilage
bone

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20
Q

acoustical impedance

A

resistance of a medium to passage of sound waves

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21
Q

clinical implications of attenuation

A

• Low frequency for deeper tissues
• High frequency for superficial tissues
• Bone is very absorbent — want little exposure
• Travels well through fat

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22
Q

Frequency

A

 # of wave cycles per second
 Wave duration/length decreases as frequency increases
 Therapeutically 1-3 MHz are used

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23
Q

Near field

A

before the beam becomes divergent –> before it hits its first interface

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24
Q

far field

A

after the beam becomes divergent

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25
what causes changes in distribution of energy?
 Uneven pressure  Size of soundhead (central 1/3 is primary area of energy)  Interface in near field  Average intensity
26
spatial peak intensity
 Maximum intensity appearing at any point in the beam
27
Spatial average intensity
The intensity measured within 5mm of the transducer and averaged over the effective radiating area of the transducer
28
BNR
- beam non uniformity ratio - relationship of SPi and SAi (SPi:SAi)
29
clinical significance of BNR
- want a small BNR - spatial average is what we put into the units - characteristics of different machines may make it feel more or less warm
30
PAMBNR
- peak area of maximal BNR - the area of SPi is not equal among US manufacturers - Difference in the area of SPi may alter how warm the sonation is perceived
31
Temporal Peak Intensity (TPi)
- Peak intensity during a cyclic period - In continuous mode it is = to the average intensity
32
Temporal Average Intensity (TAi)
- pulse (going to be half of what we put in) - the average amount of energy delivered to the tissue during the application of ultrasound per unity of time
33
Duty Cycle (Mark:Space ratio)
percentage of time the ultrasound intensity is on during a cycle
34
duty cycle vs mark:space ratio
- duty cycle: 50%= 1/2 - mark:space ratio: 50% = 1:1
35
when duty cycle is high....
the temporal peak intensity can also be high
36
thermal effects of ultrasound are dependent on:
 Absorption characteristics of the tissue  The number of times the transducer passes over the part  The efficiency of the circulation through the insonated area  The amount of heat developed is directly proportional to the intensity and duration of insonation in continuous use  The thermal effect is less in the pulsed mode  Reflection of soundwaves at tissue interfaces
37
clinical significance of thermal effects
- too big of an area won't have thermal effects - time - how much energy is really getting through - no one responds to the same intensity of US in an identical fashion
38
thermal effects - increased collagen tissue extensibility
 High ultrasound uptake (absorption) occurs in tissues with high collagen content  Tissue temperature needs to be maintained for at least 5 minutes for increased extensibility
39
clinical significance of increased collagen tissue extensibility
- US penetrates superficial tissue with only minimal attenuation so can get to collagen and protein rich tissue easily - need to maintain tissue temp for 5 minutes to gain increased extensibility
40
thermal effects - reduction in muscle spasm
- ask Daniela - decreased spindle activity - increased blood flow and metabolism - if you are doing it long enough
41
thermal effects - altered blood flow
at 2.0 w/cm2, 1 MHz, 10-20 mins see increase blood flow, but other studies show decrease or no change in BF
42
Ultrasound change in nerve conduction velocity - sensory nerve
decrease in distal latency and increased velocity
43
ultrasound change in nerve conduction velocity - motor nerve
- pulsed mode decrease/no change in velocity - continuous mode increased velocity
44
increased pain threshold
- as seen with any thermal agents - full understanding of mechanics causing increased pain threshold are unclear
45
US effect on bone growth
Short term therapeutic joint temperature elevation, used as part of the treatment of contractures, are not harmful to bone growth provided that no thermal damage is done and no pain is observed. However, low-level temperature elevation applied over a prolonged period of time may accelerate bone growth
46
clinical significance of US on bone growth
- short term temperature elevation is not dangerous to growing bone - no US over epiphyseal plate
47
what are mechanical effects
effects not explained by tissue rise
48
cavitation
- stimulation of gas bubbles in the fluidous tissues - stable cavitation may attentuate micro streaming
48
cavitation
- stimulation of gas bubbles in the fluidous tissues - stable cavitation may attentuate micro streaming
48
cavitation
- stimulation of gas bubbles in the fluidous tissues - stable cavitation may attentuate micro streaming
48
cavitation
- stimulation of gas bubbles in the fluidous tissues - stable cavitation may attentuate micro streaming
49
cavitation
- stimulation of gas bubbles in the fluidous tissues - stable cavitation may attentuate micro streaming
49
cavitation
- stimulation of gas bubbles in the fluidous tissues - stable cavitation may attentuate micro streaming
50
cavitation
- stimulation of gas bubbles in the fluidous tissues - stable cavitation may attentuate micro streaming
51
unstable cavitation
- Dangerous effect where the bubbles collapse on themselves - The “implosion” creates waves of tissue, which may also further increase tissue temperature - can release free radicles (never use on pts with cancer)
52
What is acoustical streaming?
 Movement of fluids along the boundaries of cell membranes as a result of the mechanical pressure wave  May cause changes in ion fluxes with subsequent changes in cellular activity  Increased cell membrane permeability and vascular wall permeability found with application in therapeutic ranges
53
what has US been shown to cause a leakage of?
potassium from RBC, increases in fibroblastic activity (i.e. protein synthesis) and increase in calcium fluxes across smooth muscle membranes of a mouse uterus
54
what is micro streaming
- Eddy or circular currents that take place around the vibrating object - Occurs outside of the gas bubbles caused by cavitation
55
Clinical significance of mechanical effects of US
- allows medicinal ions to pass - improves healing environment - movement of fluids in the interstitial space may create a massage like effect
56
Contraindications for US
- same as for superficial heat - pregnancy - over low back and uterus - over heart, eyes, spinal cord, carotid sinuses - laminectomy (cavitation of CSF) - malignancy - metal (prothesis) - growth plates
57
Principles of Application of US - Frequency
 The # of oscillations a molecule undergoes in 1 second  Most therapeutic ranges are 1-3 MHz  Vibration for frequency is achieved using either a quartz or synthetic crystal (barium titinate) and utilizes a reverse piezoelectric effect across its face
58
Principles of Application of US - Transducer (applicator)
 Treatment head containing the crystal  Come in many sizes. Some of the smaller sizes can only be used at 3 MHz  Area to be treated should NOT be larger than 2-3X the ERA of the transducer and definitely not larger than 4X the ERA
59
Principles of application of US - coupling media
 Ultrasonic waves do not transmit through air, therefore some sort of coupling agent is necessary
60
most to least transmitting couplant
aquaponic gel glycerol distilled water air
61
should you pre-heat gel before use?
you can, but it breaks down the viscosity
62
what if you are applying US to an irregular shape?
go underwater or use gel pad
63
Diagnostic Intensity
< .1 W/cm2 Frequency of .5-5 MHz
64
therapeutic intensity
.25 – 2.0 (3.0) W/cm2 Frequency of .8 – 3 MHz
65
high intensity - liposuction
> 10 W/cm 2 Frequency of .1-5 MHz
66
Duration according to Michlovitz
2-3X the size of the ERA for every 5 minutes of exposure
67
Definition of Phonophoresis
- the application of US with a topical drug in order to facilitate transdermal drug delivery - increased drug transmission occurs due to increased permeability of the stratus corneus - might be another bullet here
68
Medications commonly used for phonophoresis
- local analgesics - lidocaine - local anti-inflammatory medications - steroidal medications or non-steroidal medications - counterirritants - menthol
69
review mechanisms for ion transfer
70
what do studies using corticosteroid drug report?
positive drug enhancement with US, but questions remain about the transmission properties of hydrocortisone
71
most studies agree that what?
US can enhance drug delivery to the subcutaneous level, but have not found increases in penetration at the level of the muscle or joint
72
when can maximum local effects of US be recorded?
in 2 hours systemic effects can be measured at 12-24 hrs
73
for phonophoresis, what intensity should you use?
- in the thermal range unless contraindicated - 1.5 w/cm2 or higher
74
what intensity should you use for open wound?
- pulsed US at 0.5-1.0 W/cm2
75
what does an open wound increase?
rate of diffusion

Physical Agents (11 decks)

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