Ultrasound Flashcards
Define ultrasound
Sound traveling through a medium at frequencies above the upper-limit frequency of human audibility
What is the upper (max) limit of the human auditory range
20 kilohertz (20,000 Hz)
Define sound
A form of mechanical acoustic energy, or pressure waves, that propagates through vibration in the air and in other media such as water and soft biologic tissues.
What is meant by therapeutic ultrasound
Use of mechanical acoustic energy for treating variety of soft tissue pathologies, including bone fractures and dermal wounds
List some uses of ultrasound
- diagnosis
- destruction of tissue
- therapeutic agent
Diagnostic ultrasound can be used for
Imaging :
-internal structures
- fetus during pregnancy
Ultrasound therapy is classified into 3 categories; what are they
- CUS
- LIPUS
- MIST therapy
Conventional ultrasound (CUS)
- oldest and most conventional type of therapeutic ultrasound
- delivered at low and high frequencies and intensities
- continuous or pulsed
- application method : dynamic + contact or non contact
- common coupling agents : aquasonic gel and tap water
- used for its thermo-mechanical effects on tendon, ligament, and muscle disorders
What is the oldest and most conventional therapeutic type of ultrasound
Conventional ultrasound CUS
Method of application for CUS
Dynamic
Contact or no contact
Common coupling agents for CUS
Aquasonic gel and tap water
CUS is used for its ______________ effects.
Thermo-mechanical effects
What does LIPUS stand for
Low-intensity pulsed ultrasound
Low-intensity pulsed ultrasound (LIPUS)
- ultrasonic energy
- delivered at MEDIUM frequency (1-1.5 MHz)
- delivered at LOW intensity (0.03 W/cm2)
- application method: stationary with contact
- PULSED
- coupling medium : ultrasonic gel
- used for its MECHANICAL effect on fresh and slow-to-heal bone fractures
Which therapeutic ultrasound is ideal for fresh and slow-to-heal bone fractures?
LIPUS
Which therapeutic ultrasound is applied using stationary applicator ?
LIPUS
LIPUS is used for its ____________ effect.
Mechanical
Conventional US induces thermal and mechanical effects in pathological soft tissues especially those that are rich in ______________.
Proteins
Examples of tissues rich in protein
- tendons
- ligaments
- muscles
- joint capsules
Noncontact low-frequency ultrasound (NCLFUS) is also known as _______________.
MIST Therapy System
Noncontact low-frequency ultrasound (NCLFUS)
- most recent therapeutic ultrasound
- delivered at LOWER frequency (40kHz)
- delivered at LOWER intensity (0.5 W/cm2)
- PULSED
- application technique: dynamic + noncontact
- coupling medium: sterile saline water
- promotes dermal wound healing through its mechanical cleansing, debridement, and antibacterial effects
Which therapeutic ultrasound heals dermal wounds through its mechanical cleansing , debridement, and antibacterial effects?
NCLFUS (MIST)
Between LIPUS and CUS, which is delivered at a lower intensity?
LIPUS
What is the most widely used EPA
Conventional US
What type of waves are sound waves ?
Longitudinal waves
(NOT TRANSVERSE)
Sound waves consist of areas of _________ and ____________.
Compression
Rarefactiion
What happen to particles of materials when exposed to sound waves?
Oscillate about a fixed point
True or false
When exposed to sound waves, particles move with the wave itself .
False!
They oscillate about a fixed point
Relationship between molecular vibration and heat
Increase in molecular vibration = increase in heat generation
(More oscillation = more heat)
Therapeutic ultrasound is produced at a frequency of ________ to _____ MHz
0.7 - 3.3 MHz
(But on machines its usually 1-3 MHz)
NOTE: increases depth of absorption by 2-5 cm
How does therapeutic ultrasound transmit energy?
By compressing and rarefying materials
What happens to intensity as it travels deeper in the tissue
Decrease
True or false
Ultrasound is inaudible
True
How is the ultrasonic beam energy formed ?
High frequency electric current is applied to the surface of a piezoelectric material (crystal) called a transducer , causing mechanical deformation of this transducer, leading to cycles of expansion and contraction that produce compressions and rarefactions of the beam.
What is a transducer
A piezoelectric material or crystal that is usually a fragile quartz. This crystal when exposed to an electrical current can expand or contract; thus, producing compressions and rarefactions.
IT CONVERTS ELECTRICAL ENERGY INTO ACOUSTIC ENERGY
Expansion of the transducer causes __________.
Compression
Contraction of the transducer causes ___________.
Rarefaction
Ultrasound waves created by repeated cycles of micro-expansion and micro-contraction of the transducer have what shape ?
Sinusoidal shape
What happens during the expansion phase of the transducer
- high pressure in soft tissues
- molecules closer together
- compressions
What happens during the contraction phase of the transducer ?
- low pressure in soft tissues
- molecules further apart
- rarefaction
Compression and rarefaction and compression and rarefaction again and again cause …
heat due to oscillation
The applicator is made out of 2 parts :
- Transducer
- Sound head (metal plate/ faceplate)
How thick is the transducer ?
2-3 mm
Purpose of the transducer
Converts electrical energy into acoustic energy
What is the purpose of the sound head on the applicator
Transfers acoustic energy from transducer to soft tissues through a medium
Describe the near field
- closest to the transducer
- less divergent
- more focused beam
AKA : Fresnel zone
Describe far field
- immediately follows near field
- more divergent
- less focused beam
AKA: Fraunhofer zone
Which field is referred to as the Fresnel zone
Near field
Which field is referred to as Fraunhofer zone
Far field
Two types of delivery modes
Continuous mode
Pulsed mode
Define continuous mode
Uninterrupted (continuous) flow of acoustic energy during the whole treatment duration
Is continuous mode thermal or athermal
Thermal
Is continuous used for acute or chronic conditions
Chronic
What is pulsed mode
Acoustic energy that is periodically interrupted (rhythmic flow) where ultrasound is delivered for a given duration (ON time) followed by a period of no delivery (OFF time)
Is pulsed used mainly for acute or chronic conditions
Acute
Does pulsed mode produce a thermal or athermal effect
Athermal
But high intensity may produce a slight thermal effect
What is duty cycle
Period of time, measured in percentage, during which acoustic energy is delivered
How to calculate duty cycle
ON-time / (ON-time + OFF-time) x 100
What is the duty cycle for continuous mode
100%
What is the most commonly used duty cycle for pulsed mode
20%
What does it mean to have an on and off ratio of 1:4
The time during which US is delivered ON is four times shorter than the time value during which it is OFF
What is meant by pulse frequency
The number of compressions and rarefactions or the number of wave cycles completed each second
How to calculate pulse frequency
f= 1 / (ON time + OFF time)
Which frequency is suitable for superficial heating
3 MHz
Which frequency is suitable for deep heating
1 MHz
Relationship between wavelength and frequency
Inversely proportional
Which heating involves higher frequency and lower wavelength according to this picture?
Superficial heating :
- higher frequency
- lower wavelength
Deep heating :
- lower frequency
- higher wavelength
What is the effective radiating area ERA?
Total area of the surface of the transducer that actually produces the sound wave
Unit of ERA
cm2
The ERA is ___% smaller than the transducer faceplate area
10%
True or false
The ERA is 10% bigger than transducer faceplate ?
False
(Smaller)
Relationship between treating area and ERA
The larger the treating area the larger the ERA
(NOTE: the ERA and treating area have a ratio of 1:3)
What is intensity
The amount of acoustic power (measured in Watts W) per unit area of the transducer ERA (measured in cm2) used to deliver this energy to tissue
How to calculate intensity
Acoustic power (W) / ERA (cm2)
Unit of intensity
(W/cm2)
What terms are used to describe intensity ?
Spatial
Temporal
What is meant by beam non uniformity ratio (BNR)
Amount of variability of intensity within the ultrasound beam
True or false
The higher the quality of the crystal (transducer) = the better the beam
True
Physiological THERMAL effects of therapeutic ultrasound
Athermal (mechanical) therapeutic effects
- acceleration of healing process
- wound healing
- acceleration of bone growth
Physiological ATHERMAL effects of therapeutic ultrasound
What two things occur during athermal ultrasound that promote therapeutic effects
Stable cavitation
Acoustic microstreaming
What is meant by acoustic cavitation
Formation of empty spaces or cavities resulting from the formation of micro bubbles which expand and contracts under the influence of acoustic radiation
What are the two types of acoustic cavitations
Stable (good)
Unstable (bad)
Describe stable cavitation and microstreaming
Occurs when the bubbles begin to pulsate, meaning it compresses during high pressure and expand during low pressure waves.
This triggers MOLECULAR MOVEMENT as molecules come closer together during compression and further apart during rarefaction
This movement of the fluid is called MICROSTREAMING
Microstreaming causes movement and transfer of intracellular and extracellular ions affecting cellular membrane permeability
Describe unstable cavitation
Occurs when the bubbles, subjected to strong cycles of compression and expansion, collapse or implode, releasing very high temperature and pressure changes in their surrounding
How to prevent unstable cavitations
With dynamic application technique (constantly moving the head)
Define acoustic microstreaming
The Unidirectional movement of fluids along the boundaries of cell membrane resulting from stable cavitation
True or false
Stable cavitation leads to microstreaming
True
Indications of ultrasound therapy
Inflammatory conditions (acute, subacute, chronic)
Swelling and effusion
Pain relief
Soft tissue healing and repair
Wound management
Bony fracture management
Ultrasound is a mechanical wave in which energy is transmitted by _____________.
Vibration
What is meant by absorption
Conversion of mechanical energy into heat
In what tissue is absorption rate the highest
Tissue with high protein content
In what tissue is absorption rate the lowest
High water content tissue
Get a good look at this slide, containing tissue with the highest and lowest rates of absorption
What is reflection
The amount of energy transmitted determined by the acoustic impedance of the two materials on either side of interface
(From my understanding its basically the amount of acoustic waves reflected and not absorbed)
Reflection and absorption at soft tissues such as bony interface
35 % reflection
65 % absorption
Reflection and absorption of skin interface with medium
0.1% reflection
99.9% absorption
Reflection and absorption of skin interface at air (without coupling medium)
100% reflection
0 % absorption
What is meant by refraction
Ultrasound energy enters the tissue at an angle and transmitted at a different angle
What is meant by standing wave “HOT SPOT”
We have some of the waves are reflected correct?
The reflected energy can combine with new transmitted energy, causing the intensity of the energy to INCREASE.
This can cause tissue damage
Can be avoided by moving head throughout treatment
What happens to intensity in the case of a standing wave “hot spots”?
Increases
General contraindications of US
- Impaired mentation
- Over infected lesions
- Cardiac pacemaker or other electronic devices (implanted or external)
- Over thrombosis areas
- On CNS tissue (brain and spinal cord after laminectomy)
- Malignant areas
- Ischemic areas
Local contraindications
Adverse effects of ultrasound
Burn
Blood cell stasis
Why is burn an adverse reaction
How does blood cell stasis occur as a side effect
List some dosimetric parameters
- coupling method
- delivery mode
- frequency
- ERA
- intensity
- application duration
- frequency of treatment
How is the ultrasound head properly placed on treated area?
90 degrees and parallel to the skin with moderate pressure
Two types of delivery modes
Continuous mode
Pulsed mode
Large duty cycle will __________ the thermal effect and _________ the mechanical effect.
Maximize thermal effect
Minimize mechanical effect
What is the depth of superficial heating with a frequency of 3MHz
2-3 cm depth
What is the depth of deep heating with a frequency of 1MHz
5 cm depth
In terms of sizes, the treated area should be no more than ____________________ than the ERA.
3 times greater (max)
Stationary application may cause _____________,
Hot spot
The intensity set for the treatment depends on what
Size, depth, nature of treated area, mode, frequency of ultrasound and time of application
Read these numbers below
What is the application duration of therapeutic ultrasound
5 to 10 minutes
What are the different delivery methods of ultrasound
- direct contact application
- water immersion (water bath application)
- cushion contact (water bag application)
- phonophoresis
Direct contact application
- contact between the skin and applicator with THIN layer of gel
- MOST convenient and efficient method
- move head in SLOW parallel strokes with LIGHT pressure at 90 degrees
- used to treat flat surfaces
Water immersion (water bath application)
- non contact method
- treated surface area and applicator are immersed in a plastic bath filled with tap water
- sound head is over and close to the skin (without contact)
Why should stainless-steel baths be avoided during water immersion application ?
It has a high capacity to reflect ultrasonic waves back to the operator immersed hand during therapy
Cushion contact (water bag application)
- soft ultrasonic gel pad is placed between the sound head faceplate and the skin, overlying the treatment area
- used is treated area cant be immersed in water and irregular and sensitive to pressure
- a thin layer of ultrasonic gel is required at both faceplate-pad interface and pad-skin interface
What are two application techniques
Dynamic technique
Stationary technique
Dynamic technique can be done by __________ displacement or _____________ displacement
Manual
Automatic
Why shouldn’t the movement of the applicator be too fast?
Because the faster the movement, the less the absorption of the ultrasonic energy into the soft tissue per unit of time
What are the parameters that should be documented and recorded
What is phonophoresis
-A technique in which ultrasound is used to enhance delivery of a selected medication into the tissue
- safe, painless and non invasive technique
- thermal and athermal mechanisms are used
- used to decrease pain and inflammation
If there is improvement, what do you do to the parameters ?
Continue using the same parameters
If there is no improvement after 3-4 treatments , what do you do to the parameters ?
Change the parameters or discontinue treatment with US
Read and understand these points
👍🏻
Can US be applied along with other agents ?
Yes !
What other agents can we apply in conjunction with US
- US with hot packs to relieve pain
- with ice packs to promote soft tissue healing and produce analgesic effect
What happens if we do skin cooling BEFORE ultrasound application?
Less heating effect in deeper tissues
Should Thermotherapy and cryotherapy be applied before or after ultrasound?
AFTER
(NِِEVER BEFORE)
