Therapeutic Ultrasound Flashcards
What is therapeutic ultrasound?
High frequency mechanical waves delivered by acoustic energy
What is the advantage of therapeutic ultrasound?
depth of tissue penetration, heats tissue 2-5 cm deep
What structures does therapeutic US provide superior heating to?
structures with high collagen content
What is the frequency of US?
1 million - 3.3 million vibrations per second
What is the piezoelectric crystal inside the US made of?
synthetic plumbium zirconium titanate 2-3 mm thick
What does the crystal in US do?
- converts electric energy to acoustic energy using high frequency AC current applied
- mechanically deformed
What is special about piezoelectric?
ability to change shape in response to electric current
- expands and contracts at the same frequency as applied current
- when expands - molecules in front of it are compressed
- when compressed - molecules are rarefied
What does piezoelectric travel as?
a longitudinal wave
What is the effective radiating area?
- don’t cover an area greater than 2x the sound head surface for treatment (2-3 times the ERA)
What is the spatial peak intensity regarding the beam nonuniformity ratio? Where is it greatest? lowest?
- peak intensity of the US output over the area of the transducer
- usually greatest in the center of the beam and lowest at the edges
What is the spatial average intensity regarding the beam nonuniformity ratio?
- average intensity of the US output averaged over the on/off time of the pulse
What is the BNR?
the peak/avg of the spatial average intensity
What is the max BNR of the transducer?
between 5:1 and 6:1
What happens to the body’s absorption of the US with wave frequency with 3 MHz?
increases
What tissue does less energy go to with 3MHz?
deeper tissues
What depth are US wave absorbed at with 3MHz?
2-3 cm
What is the rate of absorption with 3MHz compared to 1MHz?
3-4x faster
What type of frequencies penetrate deeper?
LOWER
What is the effective treatment depth of 1MHz>
6 cm
What is the rate of absorption with 1MHz?
slower
What is attenuation?
as US enters the body, it gradually decreases in intensity due to attenuation
- frequency and tissue dependent
- increases with collagen content of tissue and higher frequencies
What does attenuation occur due to?
- absorption, reflection, or refraction of the wave
What happens to the mechanical energy when US is absorbed into tissues?
converted to heat
What is the heat produced dependent on?
- energy delivered and absorption coefficient
What is the energy delivered depend on?
US intensity and duty cycle
What does the absorption coefficient depend on?
collagen content and US frequency
What is responsible for around half of attenuation?
absorption
What is the other half of US attenuation due to (aside from absorption)?
- reflection and refraction
What is reflection?
- US beam redirected from a surface at angle equal and opposite of the original beam
When does reflection usually occur?
at tissue interfaces where impedance to sound changes
- WHY WE NEED US GEL
Where is the most reflection in the body?
Between bone and soft tissue
- MORE HEAT ACCUMULATES HERE
What are thermal effects of US?
- increased metabolic rate
- decreased pain and muscle spasms
- change of nerve conduction velocity
- improved circulation
- increased soft tissue extensibility
What is US good for healing thermally?
- tendons
- lig
- joint capsule
- fascial
- scar tissue
What is heating in muscle tissue defined as ? ___ degrees celcius
4
How long do clinicians usually treat muscle?
8 mins
How long does it take to get to 3.5 degrees celsius with US?
11 mins
How fast can superficial muscles be heated using 3MHz?
in 6 mins
What is cavitation? (non thermal effect of US)
alternating compression and expansion of gas bubbles in tissue fluids caused by mechanical pressure, makes cell membranes more permeable
What is microstreaming? (nonthermal effect of US)
eddying that occurs around any vibrating object
What is acoustic streaming? (nonthermal effect of US)
movement of fluids along boundaries of cell membranes resulting from mechanical pressure waves
- produces alterations in cell membrane activity
- increased cell wall peremability
- increased intracellular calcium
- increase macrophage response
- increased protein synthesis
What are nonthermal effects of US?
- increase intracellular calcium levels
- increase skin and cell membrane permeability
- mast cell degranulation
- promotes macrophage responsiveness (good for inflammatory phase)
- promotes protein synthesis by fibroblasts
- accelerates tissue healing and reduces the length of the inflammatory process
What should we be aware of with thermal US?
- continuous frequency
- cautious of hotspots
- use primarily before stretching of shortened soft tissue, before scar tissue mobilization and for pain control
What should we be aware of with non-thermal ultrasound?
- pulsed frequency (20% duty cycle)
- no concern for hotspots
- used for alternating membrane permeability to accelerate tissue healing
What are some clinical uses of US?
- soft tissue shortening (apply with tissue in lengthened position, continuous)
- tendon and lig healing
- bone fx
- joint inflammation (pulsed)
- phonophoresis
When would we do soft tissue shortening US?
- due to immobilization after casting or sx
- shortened joint capsule, ligs, tendons
- do stretch while US applied and stay in stretch after
- 10 min US at 1.5 W/cm2
- better ROM than without
How much do we want to heat the tissue with soft tissue shortening?
dosage that increases tissue temp by 3-8 degrees C
What are parameters for US for soft tissue shortening?
1MHz continuous at 1.5-2.5W/cm2 or 3MHz at 0.5-1.0 W/cm2
How can US assist in altering pain transition or perception?
- stimulation of thermal receptors
- increased soft tissue extensibility
- change in nerve conduction through increased temp
- modulation of inflammation (nonthermal)
What are the treatment parameters for US for pain control?
- continuous duty cycle
- 1MHz or 3MHz depending on tissue depth
- 0.5-3.0 W/cm2 intensity for 3-10 mins
- 8 min rule for billing
What is the conflicting evidence for US for soft tissue healing and inflammation?
on efficacy of applying US to peri wound area
- reduction in wound size
What is the strong evidence for soft tissue healing and inflammation?
- US promoted healing of surgical incisions and relieve pain from scars when applied to chronic tissue injuries month or years after surgery
What is the treatment parameters for US for soft tissue healing and inflammation?
- indirect or peri wound technique
- pulsed duty cycle
- 3MHz
- 0.5-1.0 W/cm2 fo 3-10 mins
3x a week for 6-16 weeks
What has US been reported to do for tendinopathies?
reduce tendon inflammation
- very effective for med/lat epicondylitis
- US and cross friction massage more effective than laser therapy
What is the treatment parameters for US for tendon inflammation during acute phase?
- dont aggravate and increase inflammation
- pulsed (nonthermal)
- 0.5-1.0 W/cm2 for 3-10 mins
What are the treatment parameters for US for tendon inflammation during the chronic/subacute phase?-
- continuous
- increase in intensity as tolerated
- combine with stretching assist in resolving chronic tendinosis
What type of US is good for healing bone fractures?
low-intensity pulsed US (LIPUS?) can reduce fracture healing time
- very safe
What are the treatment parameters of US for healing bone fx?
- pulsed (nonthermal)
- 1.5 MHz (DEEP)
- 0.15 W/cm2 intensity for 15-20 mins per day
What is phonophoresis?
- application of US in conjunction with a topical drug preparation as the US transmission medium
What are the benefits of phonophoresis? How does it work?
- higher initial drug concentration at the delivery site initially, quickly moved around the body by vascular system
- avoids stomach problems
- avoids initial metabolism by the liver
- works by thermal/nonthermal effect of increased permeability of the stratum corneum
What types of medicines is phonophoresis mainly used by the therapist to deliver?
corticosteroids and local analgesics
What conditions can phonophoresis be used to treat?
such as tendinitis, CTS, etc.
What number of treatments is phonophoresis limited to?
6
What are the treatment parameters for phonophoresis?
- medication mixed in with US gel
- pulsed duty cycle (nonthermal)
- 3MHz (superficial)
- 0.5-1.0 W/cm2 for 5-10 minutes
- low intensities and longer time more effective for medication into skin
What are contraindications for US?
- malignant tumor
- pregnancy
- CNS issue if exposed by laminectomy above L2
- Over methyl Methacrylate cement or plastics in joint replacement components
- pacemaker or implantable cardiac rhythm device
- thrombophlebitis
- over the eyes
- near the reproductive organs
What are the precautions for US on epiphyseal plates?
- high dose US will damage the open epiphyseal places, low dose at up to 0.5 W/cm2 was found to be safe
What are the precautions for US on acute inflammation?
no US settings that could create heat
What are the precautions for US for fractures?
- only as described in fracture healing
What are the precautions on US in breast implants?
- high dose US should not be applied over a breast implant
What are adverse effects of US?
- burns if high intensity US is being used and the head is not used - KEEP THE HEAD MOVING, dont apply to areas with impaired sensation
- standing waves if the US wave is reflected back and superimposed on the incident wave entering the tissue, avoid by moving US head throughout
- Cross contamination of bacteria - clean heads and gel bottle
Why do we need to move the US head at all times?
- if stationary, center gets more US transmission, can overheat and burn patient
What is the rate at which we need to move the US head to avoid burns?
- ~4cm/sec
- between 2-8 cm/sec and equal amount of US is absorbed
How many treatments should we have before an effect should be able to be seen?
1-3 treatments an effect should be detectable
How often can we use nonthermal US for earlier stages of healing?
daily if needed
What is the recommended times per week for thermal US during the subacute/chronic healing stages?
3x/week
What is the intensity for 1MHz frequency?
1.5 W/cm2- 2.5 W/cm2
What is the intensity for 3MHz frequency?
0.5 to 1.0 W/cm2
Greater frequency requires ________ intensity to achieve similar heat
less
What is used to determine the final US intensity for thermal US?
The patients self report of warmth
What will the patient complain of if the intensity is too high? Why?
a deep ache from overheating the periosteum = reduce intensity to avoid burns
After __ - __ minutes if the patient does not feel heat, the intensity is too LOW
2-3
