Modalities Ch. 14 Flashcards
(67 cards)
1
Q
what is sound
A
form of vibrational or acoustic energy
sounds travel in waves
2
Q
what sounds can we hear?
A
16,000 - 20,000 Hz
3
Q
ultrasound
A
inaudible, acoustic vibrations
high frequency
may produce thermal and/or nonthermal physiologic effects
4
Q
types of ultrasound
A
diagnostic -internal structure imaging -5MHz, 3.4 mW/cm2 surgical -tissue destruction owing to thermal and mechanical effects -0.10 MHz, 20-100 W/Cm therapeutic -thermal and subthermal effects -0.75 to 3 MHz,
5
Q
therapeutic ultrasound
A
advantage over other nonacoustic heating modalities
tissues high in collagen (tendons, muscles, ligaments, joint capsules, meniscus, and cortical bone) can be heated to a therapeutic range
6
Q
anatomy of an ultrasound machine
A
generator -where electrical current is generated applicator transducer -converts electrical energy to acoustic energy -houses the crystal crystal
7
Q
how does ultrasound work
A
generator produces a high-frequency alternating current
current travels through the coaxial cable
crystal in the transducer converts electrical energy to sound energy
-reverse piezoelectric effect
8
Q
reverse piezoelectric effect
A
mechanical energy being produced by electric energy
9
Q
what happens to the crystal
A
crystal expands and contracts
- rarefaction - crystal expands
- neutral
- compression - crystal has a high molecular density
- neutral
- rarefaction
- etc.
10
Q
attenuation
A
decrease in energy as ultrasound passes through various tissue layers
Law of Grotthus-Draper
-the more energy that is absorbed by superficial leaves less energy to be absorbed by deeper tissues
11
Q
ultrasound effects on tissue
A
penetrates through tissues high in water content -fat absorbed in tissues high in protein -muscles -nerves refracted at joints reflects or bounces off bone -certain degree is absorbed in superficial bone
12
Q
how is tissue heated
A
ultrasound is absorbed by tissue
causes molecules to rotate and bounce off one another
results in heat or nonthermal effects
13
Q
Effective Radiating Area (ERA)
A
portion of the sound head that is producing the therapeutic effect
14
Q
ERA determinants
A
size of sound head
size of crystal
quality of crystal
15
Q
beam nonuniformity ration (BNR)
A
amount of variable intensity within the ultrasound beam
Ratio = variability:average output intensity
should be as close as possible to 1:1
most manufacturers accept <6:1
8.5 w/cm2 can damage tissue
16
Q
PAMBNR
A
peak area of the maximum BNR
17
Q
ultrasound parameters
A
duty factor frequency intensity treatment length treatment size application technique
18
Q
duty factor
A
pulsed or continuous
19
Q
frequency
A
1 and 3 MHz
20
Q
intensity
A
power
21
Q
treatment length
A
depends on treatment goals
22
Q
treatment size
A
depends on area you are treating and sound head size
23
Q
continuous ultrasound
A
sound waves are delivered continually at the determined frequency
24
Q
pulsed ultrasound
A
sound waves are delivered in pulses
25
pulse period
length of entire pulse including the off time
26
pulse duration
length of the on time of the pulse
27
duty cycle ratio
% "on time" (pulse duration) in relation to "pulse period"
28
when do you use pulsed?
when you do not want the therapeutic effects
29
frequency
how many times does the crystal change shape
determines depth of treatment
-3 MHz: surface to 2.5 cm
-1 MHz: 2.5-5 cm
30
power
the total amount of ultrasound energy produced by the generator
measure of pulse width and frequency
measures in watts
31
intensity
the rate at which power is delivered to the tissue
determined by power and ERA
measured in W/cm2
greater intensity = greater rate of heating
32
what should the patient feel?
heat
| warming
33
treatment length depends on
goals
size of area to be treated
intensity used
frequency (MHz)
34
rate of heating (per minute)
0.5 intensity (W/cm2) - 0.04 C at 1 MHz and 0.3 C at 3 MHz
35
dose according to goals
subacute inflammation
| -
36
thermal effects
```
increased
-extensibility of collagen fibers
-metabolism
-blood flow
decreased
-muscle stiffness
-pain perception
-muscle spasm
altered nerve conduction velocity
```
37
thermal effects
| -duration determined by
desired tissue temp. increase
frequency
intensity (patient comfort)
duty cycle of ultrasound: continuous
38
nonthermal/mechanical effects
```
calcium ion influx
cell membrane alteration
attraction of immune cells to the injured area
vascular regeneration
tissue regeneration
wound healing
increased
-histamine release
-phagocytic activity of macrophages
-protein synthesis
-capillary density of ischemic tissue
-fibroblasts
```
39
mechanical effects
another name for thermal effects
mechanical vibrations occurring at the cellular level owing to
-stable cavitation
-acoustic streaming
40
cavitation
result of the physical forces of the soundwaves on microenvironmental gases within a fluid
compression and rerefaction cause these bubbles to expand and contract
good: stable cavitation (no tissue damage)
bad: unstable or transient cavitation (tissue damage from implosion or collapse of bubbles)
41
stable cavitation
compression and expansion of small gas bubbles in the blood and tissue
- cellular effects
- -increase in cell membrane diffusion
- -increased cellular activity
42
unstable cavitation
| -occurs when
intensity is too high
when the soundhead is not moved
from a high BNR
43
acoustic microstreaming
mechanical pressure applied to the sound wave produces unidirectional movement of fluid along and/or around the cell membrane
can alter the cell membrane's structure and function
44
acoustic microstreaming cellular effects
```
stimulates protein synthesis
increases capillary density
increases ion flux
stimulates serotonin release
pain control
```
45
thermal effects
```
increased
-extensibility of collagen fibers
-metabolism
-blood flow
decreased
-muscle stiffness
-pain perception
-muscle spasm
altered nerve conduction velocity
```
46
thermal effects
| -duration determined by
desired tissue temp. increase
frequency
intensity (patient comfort)
duty cycle of ultrasound: continuous
47
nonthermal/mechanical effects
```
calcium ion influx
cell membrane alteration
attraction of immune cells to the injured area
vascular regeneration
tissue regeneration
wound healing
increased
-histamine release
-phagocytic activity of macrophages
-protein synthesis
-capillary density of ischemic tissue
-fibroblasts
```
48
mechanical effects
another name for thermal effects
mechanical vibrations occurring at the cellular level owing to
-stable cavitation
-acoustic streaming
49
cavitation
result of the physical forces of the soundwaves on microenvironmental gases within a fluid
compression and rerefaction cause these bubbles to expand and contract
good: stable cavitation (no tissue damage)
bad: unstable or transient cavitation (tissue damage from implosion or collapse of bubbles)
50
stable cavitation
compression and expansion of small gas bubbles in the blood and tissue
- cellular effects
- -increase in cell membrane diffusion
- -increased cellular activity
51
unstable cavitation
| -occurs when
intensity is too high
when the soundhead is not moved
from a high BNR
52
acoustic microstreaming
mechanical pressure applied to the sound wave produces unidirectional movement of fluid along and/or around the cell membrane
can alter the cell membrane's structure and function
53
acoustic microstreaming cellular effects
```
stimulates protein synthesis
increases capillary density
increases ion flux
stimulates serotonin release
pain control
```
54
US indications
```
soft tissue healing and repair
resolving pitting edema scar tissue and joint contracture
heat and stretch routine
chronic inflammation
bone healing
assessing stress fractures
pain
effects of deep heat
```
55
low intensity US for bone
```
unadjustable preset low intensity pulsed US parameters
-1.5 MHz frequently
-20% duty cycle
-0.15 W/cm2
20-30 minutes daily
may or may not work
```
56
US contraindications
heart disease and pacemakers
pregnant uterus
testes
directly over the heart, eyes, spinal cord, carotid sinus, cervical stellate ganglion, or vagus nerve
directly over areas of absent or diminished sensation
57
more contraindications
malignant tumors or cancerous lesions
over areas of circulatory insufficiency
acute or severe sepsis or local infection
over epiphysis in growing bones (calcium influx)
-females 15.5 years old
-males 17.5 years old
danger of hemorrhage immediately after injury
58
size of the treatment area
should be limited to an area no more than twice the size of the soundhead
59
transducer movement
use slow strokes covering about 4 cm/sec.
- can use back and forth or circular strokes
- keep the faceplate flat on the surface being treated
60
application technique - coupling medium
ultrasound requires a medium or couplant to be placed between the soundhead and the skin so that air does not interfere with transmission of ultrasound
gel: most common
water: water immersion technique over bony prominences
gel pads: over bony prominences
61
immersion technique
used to treat small areas when soundhead cannot lie flat on the tissue surface (bony prominences)
soundhead does not touch tissue, but is held 0.5 cm away from and perpendicular to the target tissues
may need to increase intensity by as much as 50%
62
ultrasound gel pads
small areas
bony prominences
use gel between both soundhead and pad and pad and skin
63
other uses of US
phonophoresis
- ultrasound to increase cell membrane permeability
- facilitates the delivery of medication molecules to precise locations in the body
64
common medications used in phonophoresis
```
anti-inflammatories
-cortisol
-salicylates
-dexamethasone
analgesics
-lidocaine
```
65
heat and stretch
heat the area before
- or during stretching
- joint mobilizations
- friction massage
66
stretching window
```
time period (window of opportunity) of vigorous heating when stressed tissues undergo their greatest extensibility and elongation
tissue heated to 40C will drop to 38C within 5-10 minutes after an ultrasound treatment has terminated
```
67
guidelines for use
```
obtain history
determine goal
position patient comfortably
inspect treatment area
obtain appropriate size of the soundhead
determine frequency
set duty cycle
apply couplant
set treatment time
maintain contact
adjust intensity to perception of heat
terminate treatment
assess efficacy
record treatment response and parameters
```
