Ultrasound Flashcards
What do we utilize ultrasound for? *Therapeutic modalities
- Thermal
- Non-thermal
What are the common transducer frequencies?
- 1 MHz
- 3.3 Mhz
What is the Reverse Piezo Electric effect?
The application of an electric field to a crystal causes a realignment of the internal dipole structure
What is an ERA?
Effective Radiating Area
The area of a therapeutic ultrasound head that produces useful ultrasonic energy, measured in square centimeters (cm2)
What is a BNR?
Beam Nonuniformity Ratio
- The ratio of the average intensity of the ultrasound beam across the ERA divided by the peak intensity of the ultrasound beam
- This is essentially the amount of error in the sound wave field
What is the smallest ERA multiple you should use when treating an area with ultrasound?
Never go below 1.5x ERA of the sound head.
What is the maximum area you should treat based on a given ERA?
Never exceed 4x ERA recommendation
It’s not that it is dangerous it just becomes highly ineffective.
In what structure is the velocity of the sound waves generated by Ultrasound the greatest?
- Velocity is greatest in dense tissue
- Collagen
When ultrasound waves pass through a tissue there is a “split” in the wave, one is called the transmitted wave, the other the refracted wave. Explain what those terms mean.
- Refracted Wave - Refraction is the change in direction of a wave as it passes from one medium to another
- Transmitted Wave - The remaining wave that continues on to the target area
What is the relationship between temperature and frequency?
Temperature increase is proportional to frequency
What depth does a 1MHz frequency reach?
5cm
What depth does a 3MHz frequency reach?
1-2cm
What is spatial averaged temporal peak intensity? (SATP)
This is what the machine reports to you as the average intensity in Watts/cm2
What is a duty cycle?
How long an ultrasound machine is on during its on/off time
What are the two modes for the duty cycle?
- Continuous
- Pulsed
What is needed to calculate Spatial Average Temporal Average?
You need the Duty cycle x SATP
So if you have a pulsed duty cycle @ 20% at an average intensity of 1.0W/cm2
20% * 1.0 = 0.2W/cm2
What are the thermal effects of ultrasound?
- Increased metabolism
- Increased collagen extensibility
- Increased blood flow
- Decreased joint stiffness
- Decreased muscle spasms and pain
- Creates a mild inflammatory response as the result of mast cells
- Could cause a periosteal burn
What factors affect temperature increases in ultrasound?
- Frequency
- Intensity
- Duration
- Area
- Tissue Type
- ERA
- Speed of movement
- Individual person
- Machine
What are the contraindications for both thermal and non-thermal ultrasound?
- Implanted electronic devices
- Cancer
- Acute DVT
- Pregnancy
- CNS Tissue
- Eyes
- Male/Female reproductive organs
What are the contraindications for thermal ultrasound?
- Acute inflammation
- Joint cement & plastic
- EPiphyseal plates
- Fractures
- Breast Implants
What are the adverse reactions of ultrasound?
- Burns due to standing waves
- Cross-contamination infection
- Blood vessel endothelial lining damage
A patient walks in and requests an ultrasound treatment, what are your setting considerations when setting up the ultrasound to use?
- Frequency
- Duty Cycle
- Intensity
- Time/Duration
- Positioning
What is the general guideline for intensity settings in ultrasound when treating acute inflammation?
20% pulsed @0.5-0.8W/cm2
What is the general guideline for intensity settings in ultrasound when treating subacute inflammation/proliferation?
0.5-1.5 W/cm2 Mild Warmth- Moderate Warmth
What is the general guideline for intensity settings in ultrasound when treating Chronic inflammation?
1.0-2.0 W/cm2 Strong Heat, NO PAIN
