Ultrasound

What does attenuation mean?

as ultrasound travels through material, it decreases in intensity

What is periosteal burning?

when the periosteum lining of the bones is burned due to the US waves focusing on the periosteum for a long period of time

How can a PT decrease risk of periosteal burning?

always keep the US want moving around

How does ultrasound work?

-applies a high-frequency, alternating electrical current to the crystal in the transducer of the US unit

-the current causes the crystal to expand and contract, thus causing compression-rarefaction to form the ultrasound wave

Are thermal or non thermal effects felt with pulsating US? What about continuous?

thermal = continuous

non-thermal = pulsating

What size of an area can you treat with US?

an area that is twice the size of the US head

T or F: The thermal effects elicited by continuous setting of US are the same as the effects achieved by superficial heating modalities

True (just smaller area)

What does having a high absorption coefficient mean? What type of tissue have this?

it means that US can heat this tissue more than those with low absorption coefficients; EX) tendons, ligaments, joint capsules, fascia

T or F: Fat and muscle have low absorption coefficients

True

What is the speed of the transducer?

2-8 cm / second

T or F: Speed will alter the effects of ultrasound, thus changing its efficacy as a modality

False; will still have the same effect, but the speed will influence the likelihood of burning

What is the frequency of US?

1MHz or 3MHz

What does frequency mean for US?

the number of compression-rarefaction cycles per unit of time (expressed in Hz)

Describe the frequencies' depth for US

1MHz = up to 5cm

3MHz = 1-2cm

What frequency is used for more superficial structures?

1-2cm; 3Hz

What intensity and duration combination produces the greatest temperature increase?

high intensity; long duration

If the US intensity is too high, what will the pt c/o?

deep ache (probably from overheating the periosteum)

What is the duty-cycle?

the proportion of treatment time that the ultrasound ison

If the duty cycle is 1:1, what it the effect on tissue?

thermal effect

If the duty cycle is 75%, what is the effect on tissue?

thermal effect

If the duty cycle is 1:5, what is the effect on tissue?

non-thermal effect

If the duty cycle is <50%, what is the effect on tissue?

pulsated US causes non-thermal effects

What is the most common pulsed ultrasound duty cycle?

20%

What are the therapeutic effects of pulsed US?

-aids in wound healing (via increased mast cell degranulation)

-promotes macrophage responsiveness (helps decrease inflammation as macrophages are responsible)

-increases tissue repair (via increasing protein synthesis via fibroblast and tendon cells)

What are the clinical indications for US?

-thermal effects used primarily before stretching soft AND/OR to reduce pain

-non-thermal effects used for altering membrane permeability to accelerate tissue healing, decreasing inflammation

What are precautions for US?

-on epiphyseal plates (young children)

-fractures (in low doses is safe)

-breast implants (increased pressure can cause rupture)

What are contraindications for US?

-malignant tumor

-pregnancy

-joint cement (replacement of joint)

-plastic components (prosthetics)

-pacemaker, defibrillator

-DVT

-on eyes

-reproductive organs

-over spinal cord

What could be some adverse effects of US?

-periosteal burning

-standing waves can cause blood cell stasis because of the collection of gas bubbles damaging endothelial lining of blood vessels; if the US waves stay in one spot, it causes lack of blood flow

How can all adverse effects of US be avoided?

both periosteal burning and standing waves will be avoided if he transducer head is constantly moving

What are stable and unstable cavitations?

stable = bubbles oscillate in size throughout many cycles but do not burst (non-thermal)

unstable = bubbles grow and suddenly burst producing large, brief, local pressure and temperature increases (thermal)

What type of cavitations are associated with continuous ultrasound?

unstable (thermal)

What type of cavitations are associated with pulsed ultrasound?

stable (non-thermal)

If a pt has a bruising on their lateral epicondyle, what are the general parameters for US that will be indicated?

-20% duty cycle

-3MHz

- .5W/cm then go to 1.0W/cm

-8 minutes

What is the parameter for intensity when 1MHz frequency is used for thermal effect?

1.5 - 2.0 W/cm^2

What is the parameter for intensity when 3MHz frequency is used for thermal effect?

0.5 W/cm^2

What is the parameter for intensity when 3MHz frequency is used for non thermal effect?

0.5 - 1.0 W/cm^2

What is the parameter for intensity when 1MHz frequency is used for non thermal effect?

0.5 - 1.0 W/cm^2

How long should US be applied for therapeutic effects?

5-10 minute; HOWEVER MUST BE 8 MINUTES TO BE BILLABLE

How many treatments might it take before a pt feels the effects of US?

several

After how many treatments without any therapeutic effects does it take that it becomes unethical to continuing with US treatment?

6-8 treatments

If a pt has a levator scapulea that is spastic for 8 months, what are the US parameters?

-duty cycle 100% (for thermal effects because the pt has chronic inflammation)

-1MHz for a 5cm treatment because muscle is deeper

-1.5 W/cm^2 to start for thermal effects

-8 minutes

-3x per week

How is US utilized for wound care?

the US is utilized 5-15mm from them wound edge and then multiple horizontal and vertical passes are made over the wound which is covered with a gel dressing

What is the time parameter for US on wounds?

10cm^2 for 3 minutes

10-19cm^2 for 4 minutes

and then 1 additional minute for every additional 10 cm^2

How long would a US go for when doing wound care with a size of 25cm^2?

5 mintues

When are thermal effects used on a wound? What about non-thermal effects?

-non thermal on acute wounds

-thermal on chronic wounds

What are the parameters for wound care US on acute wounds?

20% duty cycle (non thermal), 0.5W/cm^2 intensity, and then 1MHz to 3MHz depending on depth, and 3-10 minutes depending on size

What are the parameters for wound care US on chronic wounds?

100% duty cycle (thermal), 0.5W/cm^2 intensity, 1MHz to 3MHz depending on depth, 3-10 minutes depending on size

Why might US be used on scars?

used for scar pain relief on scars, particularly scars that occur during vaginal tears

What parameters of US is safe to use over bone fractures?

1.5 MHz frequency

0.15 W/cm^2

20% duty cycle (non thermal)

15-20min daily

Why would US on bone fracture be indicated?

facilitates bone growth with acute fractures in coinciding with Wolfe's law.... the bone can get strong via tensile movement with the US and cavitation can cause bubbles to vibrate on the bone

What is phonophroresis?

the application of US in conjunction with a topical medication to drive the medication transdermally through he skin via US waves

What are the parameters for phonophoresis?

20% duty cycle (non thermal)

0.5 - 1.0 W/cm^2

3MHz frequency

5-10 minutes

Why would a pulsating setting on the US be utilized for phonophoresis instead of continuous?

if it is continuous, the medication will get absorbed too quickly

What is the application technique of ultrasound? What is the order of steps?

1. consent and confirm there are no contraindications

2. clean transducer head with alcohol to avoid cross contamination before/after

3. apply gel

4. select sound head size with an appropriate ERA which should be about half the size of the treatment area

5. select tx parameters

6. place sound head on the pt and begin to move the sound head

7. turn on the machine, keeping the transducer moving at 2-8 cm/second

What does ERA mean?

effective radiating area

How does delivering medication through the skin via phonophoresis cause its effect throughout the body?

although drugs delivered via phonophoresis are initially more concentrated at the delivery site, they are quickly distributed around the body by the vascular system