Ultrasound Flashcards
T/F: Ultrasound uses sound waves at high frequencies?
True
What type of modality is ultrasound?
Deep heating
Can ultrasound penetrate fat?
Yes, it can be used to heat muscles, tendons, ligaments, joint capsules, scar tissue etc
What is the most common heating modality used by chiropractors in the US?
Moist hot packs ( 71%)
What is the most common heating modality used by chiropractors of all nations?
Ultrasound
Electrical current is passed through _________ causing it to vibrate?
a crystal
What is the frequency range of musculoskeletal treatments?
800,000 Hz to 3.3MHz
How do you calculate duty cycle?
Dividing time sound is delivered by the total treatment time
What does a duty cycle of 100% mean?
Continuous Ultrasound
What is the result of continuous ultrasound?
Tissue heating
What is the result of pulsed ultrasound?
Mechanical/non-thermal effects
What is the Piezoelectric effect?
Mechanical deformation of a crystal causes an electrical current to form
Explain the Reverse Piezoelectric effect
AC current is passed through a crystal, results in very fast contraction and expansion of the crystal, this vibration produces high frequency sound waves.
What is ERA?
Effective Radiating Area: Area of the sound head that produces sound energy. Always smaller than the size of the ultrasound head!
What is BNR?
Beam Nonuniformity Ratio: Ultrasound beams are not uniform across the US head.
BNR= the amount of variability of the beam.
Ratio between the peak intensity of the US beam divided by the average intensity of the US beam.
Used to compare quality of machines.
What is the Ideal BNR?
1:1 but within range of 2:1-8:1.
What does a 2:1 BNR mean?
At 1W/cm^2, the peak intensity is 2 W/cm^2
T/F: Lower the BNR the more uniform the intensity of the sound wave
True!
What is PAMBNR?
Peak area of the Maximum beam nonuniformity
Describes the area of the sound head covered by the peak intensity
Does a LARGE or small PAMBNR mean less uniform heating?
LARGER
What is the best conducting media for ultrasound?
Gel and Gel pads specifically designed for US
T/F:Underwater is a type of direct ultrasound?
False; It is a type of indirect ultrasound
Why do you not want to use a metal bucked for underwater US?
Because it will cause reflection of the sound waves.
What do you need change about your technique when going from standard US to underwater US?
Increase intensity or Increase time of treatment.
Is it normal for bubbles to form on patients skin during underwater US?
Yes, wipe them off from skin and sound head occasionally during the treatment.
Which frequency of US is more superficial?
High Frequency (3MHz): absorbed more rapidly therefore affects superficial tissues
Which frequency is for deeper tissues?
Low Frequency (1MHz): absorbed at a
slower rate therefore affects deeper
tissues
What type of tissues absorb most sound energy from US?
Bone, tendon, cartilage, ligaments, and joint
capsules absorb most
Which type of tissues absorb the least amount of sound energy from US?
Skin and fat absorb the least
More Watts = ???
More heating NOT greater penetration
Frequency affects what two things?
Depth and Time
What is reflection in terms of US scattering?
Reflection: the reversal of the direction of
propagation of the ultrasound wave
What is refraction in terms of US scattering?
Refraction: change of ultrasound wave from a
straight path when passing obliquely from one
medium to another
T/F: Tissues close to the bone: periosteum, tendons,
and aponeurotic attachment of muscle,
cartilaginous coverings of joint surfaces, and
peripheral nerves lying close to bones receive
increased dose (increased heating)
TRUE
T/F: The bending of US energy within tissue can lead to concentrations of US at the point of refraction
TRUE
What is the main effect of US?
Tissue heating
What are the Therapeutic Effects of US?
• Increase extensibility of collagen fibers of tendons and joint capsules • Increase blood flow • Increase cell metabolism • Increase collagen synthesis • Decreased joint stiffness • Decreased muscle spasm • Enhanced tendon, ligament, and muscle healing
Do superficial or deep tissues cool more rapidly?
Superficial!
Any tissue manipulation or stretching should
be performed when?
Immediately after ultrasound treatment
What is acoustical streaming?
Movement of fluids along cell membranes
due to mechanical pressure exerted by the
sound waves
What is cavitation?
– Formation of gas filled bubbles from pressure
changes in tissue fluids
– Bubbles expand and contract with ultrasound waves
What are the different types of Cavitation?
Stable and Unstable
Define Stable cavitation
Rhythmic expansion and contraction of bubbles
during repeated pressure changes over many
acoustic cycles
– Facilitates fluid movement and membrane transport
Define Unstable cavitation
– Collapse of gas bubbles which may cause tissue
damage
– Associated with low frequency high intensity
ultrasound (not therapeutic)
What are the contraindications for US?
- Malignancy
- Hemorrhage
- Ischemia
- Thrombus
- Infection
- Gonads
- Eye
- Pelvic, abdominal, and lumbar areas of pregnant women
- Spinal cord after laminectomy
- Plastic and cemented implants (metal is OK)
- Near or over electronic implants
- Unknown etiology
What are the risks associated with US?
May alter bone growth.
Avoid bony prominences..
Describe the movement of the US head when apply therapy
• Slow controlled movement of the US head
– 2–4 cm2/s (2 inches per sec)
What is the treatment time for US?
Generally 5-8 minutes.
What is the maximum time you can treat someone with US?
NEVER treat for more than a total of 15
minutes (several treatment areas)
What do you do if you have a large treatment area?
– break it up into 2 or 3 smaller areas and treat
for 5 minutes per region
Phonophoresis is AKA what?
Sonophoresis
What is Phonophoresis/Sonophoresis?
Uses sound energy to drive medication
into the tissue
Why would someone use Combo US therapy?
Research is lacking but claims for use include: – trigger points – epicondylitis – superficial pain areas – decrease adhesions
What is combo US therapy?
Theoretically to create effects of both US and
electrical stimulation
Ultrasound head becomes the treating
electrode when used with a dispersal pad
LIPUS stands for what?
Low intensity Pulsed US
When would you use LIPUS?
To stimulate the healing of a fracture.
• Good evidence for effectiveness
What is NCLFUS?
Noncontact Low-Frequency US
When would you use NCLFUS?
Wound cleaning and debridement
• US propels sterile saline across wound
• Stimulates healing
