Deep Heating Agents: Therapeutic Ultrasound and Diathermy Flashcards
human ear can hear sound waves
16- 20,000 Hz
ultrasound
any sound wave ABOVE 20,000Hz
THERAPEUTIC US : range 750,000 - 3,000,000 Hz
most frequently used: 1 MHz and 3 MHz
imaging us: 3.5 MHZ - 10 MHZ
acoustic energy
- different than electromagnetic energy
- must travel through a medium
- like electromagnetic energy: can be reflected, refracted, and absorbed
therapeutic ultrasound
- deep heating agent
- thermal and non-thermal effects
- converts electrical energy into acoustical energy
transducer
converts one form of energy into another
Piezoelectric crystal
crystal capable of contracting and expanding –> creates “piezoelectric effect”
- -> electric current
- —-> mechanical vibration of crystal
- ——–> wave of acoustic energy results
- if damaged, can cause “hot spots” irregular sound waves, burn athletes
Reverse piezoelectric effect
as the AC reversed polarity, the crystal expands and contracts, producing US energy
- –> high frequency sound waves (acoustical energy) delivered to the body
- —> travels through tissues and is absorbed
Effective Radiating Area (ERA)
the area of the sound head that produces ultrasonic waves (expressed in cm squared)
- energy output is greater at the center of ERA
- temp is greater at the center of the ERA
- always less than actual sound head
Beam profile
beam of energy emitted from crystal is NOT uniform
- multiple waves emerge from head (areas of high and low intensity)
- energy is more uniform closer to head
- energy diverges as it moves away from source
- becomes less consistent farther from head
- –> spatial peak intensity: most energy in far field
2 TYPES:
- divergent: goes out at angles
- collimating: lines up, parallel, straight down
Beam Nonuniformity Ratio (BNR)
- the consistency (uniformity) of the US output
- ratio between the highest intensity in and ultrasound beam and the output reported on the meter
- lower ratio = more uniform beam = 1:1 perfect
- 8:1 ratio = unsafe
lower ratio =
- more comfortable
- less hot spots
- less risk of periosteal pain
- cost more
- safer, more effective
because of hot spots, keep head moving
Sound Energy Absorption
- higher protein density = more absorption
ex: tendon, ligaments, muscles - high water and low protein content = less absorption
ex: blood, fat
*although cartilage and bone have lots of protein, the majority of US energy striking the surface of either of these tissues is likely to REFLECT
Parameters: Frequency
determined DEPTH of treatment
depth inversely related to frequency
higher frequency = less depth of penetration
of waves per second
Hertz: cycles per second
Megahertz: 1 million cycles per second
1 MHz = low frequency = greater depth of penetration = deep tissue ~4cm (5 or more cm) = .2 deg C per minute per w/cm2 SLOW = heating effects last 2x longer = relatively divergent beam profile
3 MHZ = high frequency = less depth of penetration = superficial tissue 2 cm (0.8 - 3cm) = heats tissue 3 x faster than 1 MHz - .6 deg C per minute per w/cm2 FAST = absorption occurs faster --> danger of burn = relatively collimating beam profile
Parameters: Dosage
Watts/ surface area (cm2)
higher dose = more sound energy delivered to tissues in less time
—> longer tx time for lower intensities
common dose: 1.5 w/cm2
doses greater than 2.5-3 may cause tissue damage
- depends on type of tissue, condition, duration
Rate of Ultrasound Heating
Temperature Increase per Minute
INTENSITY 1 MHz 3 MHz
(TISSUE DEPTH) (5cm) (1.2 cm)
0.5 0.04 deg C 0.3 deg C
1.0 0.2 deg C 0.6 deg C
1.5 0.3 deg C 0.9 deg C
2.0 0.4 deg C 1.4 deg C
treatment area
no greater than 2-3 times the ERA
- keep sound head moving, slowly
- maintain good contact with skin
- larger area = less energy reaching tissue = less temp increase
coupling methods
US requires medium for energy to be transmitted from sound head to body tissue
1) direct coupling - transducer and gel in direct contact with skin
2) pad/bladder method - conforms to irregular shaped areas and limits treatment area size to allow more energy to be transmitted
3) immersion (water) - for treating irregularly shaped areas, sound head ~1” away in ceramic/plastic/rubber tub
If patient complains of pain or excessive heat
DECREASE intensity
INCREASE time
Parameters: Duration
5-10 min (not <3min)
time based on treatment area
larger = longer
daily, decrease with improvement
Parameters: Duty Cycle
continuous vs pulsed
continuous (100%) = thermal effects
pulsed (50%, etc.) = non thermal effects at cellular level, maybe some thermal effects but not as much as continuous
Thermal Effects
MILD heating of 1 deg C
- -> increased metabolic activity, initiation of inflammatory process
- subacute phase (instead of pulsed)
MODERATE heating of 2-3 deg C
- -> increased blood flow
- -> decreased pain
- -> decreased muscle spasm
- -> decreased chronic inflammation
- used most often (ex: tendonitis)
VIGOROUS heating of 3-4 deg C
- -> improved viscoelastic properties of collagen
- used post surgical, when trying to break up scar tissue
Non Thermal Effects
- primarily occur with pulsed US
- little heat is produced due to dissipation that occurs during off time
CAVITATION - stable = Good
- unstable = bad
ACOUSTIC MICROSTREAMING
Cavitation
formation of gas filled bubbles that expand and compress –> pressure changes in tissue fluids
(1) stable cavitation: rhythmic contaction and expansion of gas bubbles
- facilitate fluid movement and membrane transport
- -> GOOD
(2) unstable cavitation: formation of bubbles at the low pressure part of the US cycle
- results in bubble collapse and tissue damage
- -> BAD
Acoustical Microstreaming
unidirectional movement of fluids along the boundaries of cell membranes
- us causes interstitial fluids to flow
- fluids strike cell membranes
- -> altering cell membrane permeability to Na and Ca ions important in the healing process
- –> altering cell function
CELLULAR RESPONSE:
- increases cell membrane permeability
- alters cell membrane diffusion rate
- increased histamine release
- mast cell degranulation
- increased rate of protein synthesis
Indications
- maybe prior to stretching and manual therapy when pt has restricted ROM
- calcific tendonitis of the shoulder
- scar tissue and joint contracture
- -> inc tissue temp = inc elasticity
- nontherapeutic use: identifying stress fx
- continuous at 1 MHz, move slow, gradually increase intensity to 2.0 w/cm2
Precautions
- always use the lowest intensity to produce a therapeutic response
- keep sound head moving
- educate pt on what to feeel
- caution with pacemaker or implanted electronic device
- –> continuous not advised over metal implants
- NEVER go over spine or face
Contraindications
- acute conditions
- ischemic areas
- impaired circulation
- anesthetic areas
- DVT
- over active infection
- over spinal cord
- around hear, eyes, skull, or genitalia
- over thorax in patient with pacemaker
- over abdomen during pregnancy
- over fx sites
- over pelvic or lumbar area during menstruation
- cancer
- joint replacement (not continuous over metal)
Combo: US and Stim
- used to tx trigger points and muscle spasms
- thermal US and motor level estim
phonophoresis
US used to deliver a medication via safe, painless, noninvasive technique
- opens pathways to drive molecules into tissues
- not likely to damage or burn skin like ionto
- ex: dexamethasone (analgesic) and hydrocortisone (anti-inflammatory), script required
- little evidence to support tx
Short wave diathermy
therapeutic generation of local heating by high frequency electromagnetic waves
- shortwave or microwave diathermy
- continuous or pulses
primary benefit: increase local blood flow (delivery of nutrients and oxygen) from tissue heating
–> facilitating tissue repair
continuous diathermy
- used mainly with CHRONIC injuries
- increases tissue temp
- increases risk of burns
pulsed diathermy
- may or may not increase temp
- –> higher pulse frequency = more tissue heating
- –> heats to depth of 3-5cm
- –> tissue temp controlled by duration (max 4-6 deg C increase)
- transfers energy via high frequency current
- pulse allows for increased tx intensity and duration
- not the same as “non thermal”
Advantages of Diathermy
- thermal effects similar to US, but effect DEEPER tissue
- heats larger area of tissue
- doesn’t reflect from bone so less likely to create “hot spots”
- pulsed can create thermal effects as week
- heat retained 3 x longer
Disadvantages of Diathermy
- expensive
- can only treat one pt at a time
- potential for burns
Disadvantages of Diathermy
- expensive
- can only treat one pt at a time
- potential for burns
Types of Shortwave Diathermy
(1) Induction field generators
- places pt IN the electromagnetic field
- magnetic waves generated as electric current is conducted through coiled wire
- produces greatest heat within the muscle directly beneath the coil
- induction cable or induction drum (most common)
- greatest heating in tissues with good electrical conductance (muscles, blood vessels, nerves)
- safer than capacitive fg
(2) capacitive field generators
- body is actually place IN the electric field as part of the circuit: pt place between 2 electrodes of opposite charge
- affects tissue under each plate
- electrical signals sent through body, acts as resistor
- tissues with greatest resistance create most heat as current flows through path of least resistance
- -> not recommended for pts with thick layer of adipose
Types of Shortwave Diathermy
(1) Induction field generators
- places pt IN the electromagnetic field
- magnetic waves generated as electric current is conducted through coiled wire
- produces greatest heat within the muscle directly beneath the coil
- induction cable or induction drum (most common)
- greatest heating in tissues with good electrical conductance (muscles, blood vessels, nerves)
- safer than capacitive fg
(2) capacitive field generators
- body is actually place IN the electric field as part of the circuit: pt place between 2 electrodes of opposite charge
- affects tissue under each plate
- electrical signals sent through body, acts as resistor
- tissues with greatest resistance create most heat as current flows through path of least resistance
- -> not recommended for pts with thick layer of adipose
US vs Diathermy
- acoustical vs electromag energy
- collagen rich vs good conductors tissue heated
- small vs. large tx area
- diathermy has greater temp increase
- diathermy has deeper heat retention
indications of diathermy
- skin or underlying soft tissue is tender
- areas where subcutaneous fat is thick and deep heating is required (induction)
- when tx goal is to increase tissue temp over LARGE area
indications of diathermy
- skin or underlying soft tissue is tender
- areas where subcutaneous fat is thick and deep heating is required (induction)
- when tx goal is to increase tissue temp over LARGE area
biophysical effects of diathermy
TISSUE ELASTICITY
- can vigorously heat tissue
- alters collagen properties –> elongate
- requires stretching during and/or immediately after tx
- multiple tx required
Contraindications of Diathermy
- metal implants or metal jewelry
- cardiac pacemakers
- ischemic areas
- peripheral vascular disease
- perspiration and moist dressings (water concentrated heat)
- tendency to hemorrhage (menstruation)
- pregnancy
- fever
- sensory loss
- cancer
- areas of sensitivity (epiphyseal plates in kids, genitals, sites of infection, abdomen with an implanted intrauterine device, eyes and face, application through skull)
