What is ultrasound?
Deep heating modality that uses sound waves to produce thermal & mechanical effects.
What sets ultrasound apart from other types of heating modalities?
- Has the DEEPEST effects
- Up to 5cm below the skin
Why can't the pressure & sound be detected from ultrasound?
Because the level of intestity is so low at a frequency that is high enought to go undetected
What is the range of frequency in the sound waves of US?
How are ultrasound waves generated?
- Therapeutic ultrasound machines generate pressure waves by causing a crystal to vibrate.
- The quartz crystal responds to AC current by contracting during one phase of the current and expanding during the next phase when the polarity is reversed.
- When the rapidly alternating current of electricity is applied, the effect is a vibration caused by molecules bumping into each other in waves.
- The 2 phases of of ultrasound determined by the contraction & expansion of the crystal
- Compression Phase: molecules are squeezed together
- Refraction Phase: molecules spread out even more than before they were compressed
How is ultrasound energy transported to the tissues.
-do the sound waves travel?
-where are the waves absorbed?
-what are the 2 things required for the waves to travel to the tissues?
- Soundwaves do not travel
- Only the energy is transmitted
- The waves are absorbed in the air
- They require a medium & continual contact to travel to the tissues
Sound waves are delivered through the ________ ______, also called the applicator or the transducer.
Ulrasound waves are applied to the skin through a ___________, also called a coupling agent that is specially designed for used with therapeutic ultrasound.
Synonym for MEDIUM (related to US)
Synonym for SOUND HEAD (related to US)
-2 different ones
- Produces heat
- greatest in tissues w/ highest protein content (muscle)
- absorbed most where there is a difference in tissues (interfaces, joints)
- Inverse relationship between absorption & penetration
-what's the most effective depth
-how does depth relate to frequency?
-Must identify _______ _________
- Effective depth of penetration= 3-5cm or 1-2in
- Depth of penetration is inversely proportional to the frequency
- Low frequency provides greater penetration
- High frequency provides more superficial penetration (need to identify target tissue)
1 MHz Sound Head
- Penetrates about 5cm (2 inches)
- Treats deeper structures
3 MHz Sound Head
- penetrates about 3 cm (1 inch)
- Focus on more superficial structures
Frequency refers to the _______ of penetration
waves are reflected back to the original medium when waves cross boundaries from one tissue to another resulting in a loss of energy
Energy loss due to US application in a non-perpendicular fashion.
What problems may be created from reflection & refraction of waves?
- Causes summation of waves if the sound head is not moved constantly.
- These "standing waves" can lead to tissue damage as well as the damage in the crystal.
-what are the 2 types
-how does each affect the tissue
- Continuous=100%: magnifies heating effects & reduces mechanical effects
- Pulsed=ration of on to off: magnifies the mechanical effects & diminishes heating effects (normal=20%-50%)
- expressed in W/cm or W/cm2
- Relates to the output of the unit to the size of the transducer
- Acute conditions: .1 - .5 w/cm
- Sub Acute Conditions: .5 - 1 w/cm
- Chronic Conditions: 1 - 2 w/cm
- Most common intesity= 1.5 w/cm
Intesity when treating small areas w/ little movement?
Intesity should be LOWER.
Which intensity would be used when treating thin tissues?
Which intensity is used for thick tissues or shortened muscle?
How is absorption affected if the US is deep?
Beam Nonuniformity Ratio
- How well the sound head makes the beam coming out uniform and have equal temperature all around.
- Characteristic of each individual machine
- A very high percentage of the aplied intensity lies in the central 1/3 of the beam.
- The BMR compares thw average beam pwer to the peak beam power. It is a characteristic of each individual transducer.
What are the varieties of transducers? (sizes)
-the size of the sound head should reflect the size of the ______ ___________.
- 1-10cm diameter
- Reflects the size of the area treated
Difference in frequency options of older vs. newer US machines
- Older have a prset frequency of 1 MHz or 3 MHz
- New units to provide BOTH frequencies.
Most US units provide what range of intensity?
0.1 to 3.0 W/cm
Thermal Effects of US
- Increased tissue temp. up to 5cm
- Increased collagen tissue extensibility
- Increased blood flow
- Increased pain threshold
- Increase in local tissue metabolism
- Muscle relaxation
- The thermal effects of US can be altered by duty cycle, intesity, duration, frequency, & size of treatment area
- May be conduction and convection from one tissue to another (step effect to warm tissues under actual penetration)
How can thermal effects of US be altered?
- Duty Cycle
- Size of the area treated
Non-thermal effects of US
- Micromassage: caused by the oscillatory movement of tissues and cells
- Stable Cavitation: bubbles from vibration augments effects of treatment
- Acoustic Streaming: Fluid movement in the sound field sets up currents (Eddy currents)
- STIMULATES CELLS & TISSUES (INCREASES METABOLISM)
caused by the oscillatory movment of tissues and cells
Vibration of small gas bubbles on cell membrane augment the mechanical effects of the treatment
- When bubbles on the cell membrane enlarge due to high intesity
- May rupture & cause cell damage
- Fluid movement in the sound field sets up currents (Eddy Currents).
- Eddy Currents: undirectional & have an effect on the cell wall
CLINICAL DECISION MAKING FOR US TREATMENT
--long card, broken down elsewhere--
- Clear treatment goals when considering US
- Is tissue Repair indicated? If so, use pulsed ultrasound
- Is heat & stretch indicated? If so, use high intensity, continuous ultrasound
- HOT PACK-->ULTRASOUND-->EXERCISE used for ROM impairment
- Is there a large treatment area? US is inefficient in treating large areas (must have target tissue)
- What frequency is best? 1 MHz for deeper tissues, 3 MHz for trigger points & wound healing
If tissue repair is indicated, which intensity of US would be used?
If heat & stretch is indicated, which type of intensity would be used?
High intensity, continuous US
Which type of US is used for acute & subacute conditions?
low intensity, PULSED US for tissue repair
Which type of US is used for Chronic conditions involved loss of ROM?
Continuous, HIGH intensity US
How long is US usually applied? (duration)
5-10 minutes (realistically 5-8 min)
What is SAI?
- Spacial Average Intensity
- Expressed in W/cm2
- Used in continuous US
What technique is used when applying US?
- Rhythmic patter of circular movements at at rate of 4cm (1.6 in.) per second.
- Each circle should cover about 1/2 of the area of the previous circle (overlapping)
What are some indications to discontinue US treatment? (4 things)
- If complete relief is achieved
- No relief after 3 or 4 treatments
- After a course of 12-15 treatments
- Anytime progress is not noted (pain relief, decrease in mm spasm) <-- I think mm means muscle??
Why would you modify US treatment? (2 things)
- Painful treatment
- Symptoms are exacerbated
What must be included in US documentation
- Specific area treated (target tissue)
- Transducer head size
- Machine settings (frequency, pulse rate or duty cycle, intensity, duration)
- Patient Position
- Patient response to treatment