Ultrasound

What is ultrasound?

High frequency

Mechanical energy (sound waves)

Components of ultrasound transducer

Alternate current from electric source applied to piezoelectric material

• Responds to electrical current by contact

Very thin

Drop head can break it- test it

What does the piezoelectric material do?

Expands and contracts @ 1 MHz or 3 MHz in response to applied electric current

Btwn head and metal plate that goes onto of skin

Do dense tissues absorb energy?

YES

Tendons and ligaments

Do low density tissues absorb energy?

NO

They transmit energy

Blood and fat

What happens @ high intensity

Energy converted to heat

Tissues that absorb ultrasound well?

Tendon, ligaments, fascia, joint capsule, scar

Ultrasound treats dense tissues

Stable cavitation

Gas mol move back & forth as sound waves push them

Expand and contract W/O exploding

Cell layer deforms, causing cellular rxn

Gas + solid vibrate & oscillate

Acoustic streaming

Fluid moves around mol

Facilitates movement of Ca2+, K+ and other ions into + out of cells

Effect of acoustic streaming and stable cavitation

Solid molecules (i.e. cells) deform, rotate and oscillate

Mechanical pressure

Gas mol expand and contract but NO explode

Deform and rotate

Fluid moves around cells

Continuous ultrasound effects

ON all the time

Thermal + cellular effects

Pulsed ultrasound effects

Intermittent on/off cycles

Off for longer periods of time: 2 ms on, 8ms off

Heat accumulated dissipates

ONLY CELLULAR EFFECTS - ATHERMAL

Pulsed ultrasound on Collagen

PROMOTES TISSUE HEALING

More DNA synthesis/cell proliferation

• Tenocyte proliferation

• Angiogenesis (blood vessel formation)

• Vasodilate in small arterioles in ischemic tissues

• Peripheral nerve regeneration + AP → fxnl recovery

Enhanced type 1 + 3 fibres

Better collagen organization/alignment → CONGRUENT Organization

• More extensible and mobile scar

Increased tendon strength

Less inflammatory cells → speeds up inflammatory process to get to next phase

OPTIMAL ENVIRONMENT FOR HEALING

Athermal/Pulsed ultrasound treats what injuries

• Sprain

• Strains

• Tissue & wound healing

• Delivery of drug across tissue (phonophroesis)

• Hematoma (early phase)

• Fx

• Remodel scar tissue

• Surgical scar

• Ulcers/wounds (pressure injuries, venous and arterial ulcers)

• Calcific tendinitis (could also use thermal dose)

Thermal Effects of ultrasound

Absorbed energy in tissues → heats dense tissues

↑ blood flow

↑ tissue extensibility of collagen tissue, mm, trigger points + skin

Sedate sensory nerves to reduce pain

Less reflex activity + mm spasm

Heat gain modified by conduction and convection

• Absorbed by tissue around → proximity to bone

• circulation/vascularity

What does thermal ultrasound used for

Improve extensibility

Decrease pain

If ppl have contraindications for heat packs: I.e. lots of adipose tissue

When to use athermal ultrasound?

Promote tissue healing

Good for later stages of healing

If doing exercise/activity after treatment

If cold averse/allergy

Injuries thermal ultrasound used for

Chronic inflammation

Tendinopathy, tendinosis

Adhesions

Contractures

Calcific tendinitis (can use high-dose ATHERAMAL too)

Late-phase hematoma

Nerve pain

Mm guarding/mm spasm

Arthrosis

How to effectively transmit energy to tissues?

Maintain good contact btwn head and tissue by:

• Crystal and metal plate: test regularly

• Continuity btwn plate and tissue: FLAT no edge!

• Coupling agent btwn plate + tissue (low acoustic impedance)

How fast to move head?

2-3cm/s

Slow-moderate rate

How does energy refract?

Poor contact (using edge of head): less energy absorbed

What agents can ultrasound pass thru?

Gel (low impedance)

Water: in contact or slightly above

• Need adequate gel bc body hair traps air

Offloading Gel Pad: for bony, irregular, incongruent structures [i.e. fingers]

NOT AIR!

Does oil/creams transmit energy?

Biofreeze doesn’t

Don’t assume all do!

Frequency

How often /second mechanical vibration is delivered to tissues

1 MHz= vibrates 1 million cycles in 1 cycle

Determined based on depth of tissue treating

At 3 MHz, what depth of tissue is energy absorbed?

1-2 cm

At 1 MHz, what depth of tissue is energy absorbed?

>2 cm (3-5 cm)

Higher frequency, superficial tissues absorb the energy

Intensity/amplitude (W/cm2)

How strong sound wave is delivered to tissue per surface area of transducer head RELATIVE to sound head

Effective radiating area

Intensity + beam area

Head size: small one for fingers

Intensity in Watts

Energy expressed relative to beam area (W/cm2)

• Intensity relative to sound head

Duty cycle

% of time ultrasound energy is delivered

100% = continuous all the time on

20%= 20% on

Phonophoresis/Sonophoresis

Deliver drug across tissue

Drug dissolved in transmissive gel/cream

[Drug] is important

Ultrasound ↑ permeability bc disrupts lipid bilayer of stratum corneum, makes more and larger microchannels

Common duty cycle for pulsed ultrasound

1:4 [on:off], 20%

Other settings: 1:1, 50%, 1:9, 10%

Temporal Peak Intensity

Max intensity delivered by wave when on

Temporal average Intensity

Average ultrasound intensity over time when pulse delivered (over pulse repetition/On/off time)

Fxn of temporal peak intensity + duty cycle

Temporal Average equation

TA = TP X duty cycle

What parameter do machines show?

Spatial average

Temporal peak intensity

Parameters for phonophoresis

1 MHz

Pulsed 1:4

10 min for 10 cm2 area

When to use phonophoresis

If liver/organ can’t process meds thru stomach

Poor circulation in tissues

Osteoporosis can’t tolerate steroids

Condition exacerbated by medication

Athermal ultrasound for fx (LIPUS)

Low-intensity pulsed ultrasound

Stimulates bone healing

Frequency: 1x/day for 20 min through hole in cast

Exogen Parameters: 1.5 MHz, 1000 Hz, SATA 0/03 W/cm2. 10% at 0.3W average

Benefits of ultrasound for tennis elbow (lateral epicondylitis)

Less pain

Better grip strength

Les thickness of tendon

Higher fxnl score w/ pulsed & continuous ultrasound

Benefits for ultrasound for Knee OA

Less pain

Higher fxn

Benefits of Ultrasound for Frozen shoulder (adhesive capsulitis)

Less pain

Higher ROM

What to avoid when applying ultrasound?

STATIONARY HEAD

• Standing waves; keep head moving 2-4 cm/s

• Unstable cavitation

• Uneven distribution of energy intensity

  • Want to deliver spatial average intensity!

Standing waves

Stationary head

• Incident + reflected waves coincide (waves penetrate tissue + waves bounce back)

• Additive effect of tissue

Resultant energy is sum of 2 waves

Risk overheat, pain, tissue damage

Unstable cavitation

Gas bubbles implode

Release free radicals

Heat tissues, pressure, pain

Spatial peak intensity

Max intensity delivered over beam

• Most intense part of the beam

Peak is in the middle of head

• Sides are weakest/lower in periphery

Spatial average intensity

Average intensity of ENTIRE transducer

W/cm2

What parameter is recorded in SOAP note?

SATP

Spatial-average temporal peak intensity

Limitations of soft tissue healing?

Loss of contact over contours

Inefficient to treat small areas >10 cm2

Heating hard underwater → may increase dosage

How does temp of tissues affect ultrasound?

Cool/dense tissues absorb MORE ultrasound energy

Less absorbed when tissue temp less than physiological temp

• Don’t cool tissue before ultrasound if trying to target deep tissue

  • MORE ultrasound absorbed in cool area

Treatment parameters for ATHERMAL

Mode: PULSED 1:4 (20% duty cycle)

Intensity: 1.0 W/cm2 (SATP)/0.2 W/cm2 (SATA)

Frequency: 3 MHz for 2 cm deep, 1 MHz for > 2cm

Time: 15 min per 10-15cm2 surface

Speed of head: 2-4cm/s

Frequency: 5x/week for 2-3 weeks

• Then 3x/week for 2-3weeks

Treatment parameters for THERMAL healing

Intensity: 0.8-2.0 W/cm2 (SATP continuous based on body comp)

• Upper range if deep to large mm of fat

• Lower range if superficial

  • Bone heats up adjacent tissues by conduction

Frequency: 1 MHz for tissues > 2cm

Time: 10 min when client feels heat

Max size of treatment area: 10 cm2

ALWAYS SEEK FEEDBACK + SENSORY TEST

Warm as if blow back of hand

Treatment parameters for wound healing

Treat around periphery (periskin area)

Frequency: 3 MHz

Duty cycle: 1:4 20%

Intensity: 0.2 W/cm2 SATA

• SATP: 1.0W/cm2

Time: 5 min per 2.5 cm2 wound area

• +1 min for each additional 0.5 cm2 of wound area

Frequency of treatment: 3x/week until healed

Treatment parameters for Calcific tendinitis

Rotator cuff/biceps tendon

Frequency: 0.89 MHz

Intensity: 2.5 W/cm2 (SATP), 1:4 (20% duty cycle) = 0.5 W/cm2 SATA

Duration: 15 mins

Frequency of treatment: 5x/wk for 3 weeks

• 3x/week for 3 weeks

• Ebenbichler dose be4 shockwave

Shockwave > ultrasound

Where to document in SOAP Note

Under objective

When NOT to use ultrasound:

• On eyes, pregnant ppl, testes

• Over known malignancy/cancer

• Over known vascular insufficiency

• Over HEART

• Over areas w/ lack of thermal sensation (for continuous)

• Over infection/sepsis

• Over bleeding (hemophiliacs not covered by factor replacement)

• Unreliable patients (language barrier, kids, confused ppl)

Precautions for ultrasound use

Always move head

Sensory deficits, patient preferences

Lowest intensity that elicits therapeutic response

Caution over implanted devices

Continuous ultrasound over superficial metal implants

Avoid plastic joint implants

• Loosen it. Confirm w/ doc

METAL NOT A CONTRAINDICATION

Considerations for which modality to use LFT POP

• Patient preference

• Sensory deficits

• Way to position patient comfortably

Location

Frequency per week

Timing in management plan: phase of healing, fits w/ other management

Parameters: dosage, intensity, frequency

Objective measure: baseline + post-treatment

Progression: parameters/type change as patient’s symptoms progress?