Modalities: Ultrasound Flashcards
To achieve thermal effects, should continuous or pulsed ultrasound be used?
Continuous Ultrasound
How is US energy/intensity distributed on the surface over of the transducer?
Not uniformly distributed
- causes a higher energy in the center of the US beam relative to the surrounding areas.
How to reduce the effects of a hot spot?
Continuously moving the sound head.
How is Spatial Average Intensity measured?
Intensity - Total Power (Watts) divided by the area (cm2)
What is Beam Nonuniformity Ratio (BNR), relation to tissue damage?
Ratio of spatial peak intensity to spatial average intensity; don’t think that is important tbh
[important maybe]
- Lower the BNR the more uniform the energy distribution, less risk for tissue damage
What is the ideal BNR?
Between 2:1 and 6:1
(an ideal 1:1 is not technically feasible)
To achieve nonthermal effects, should continuous or pulsed ultrasound be used?
Pulsed Ultrasound (acute soft tissue injuries)
What is the Duty Cycle?
Percentage of ON Time to the Total Time; (time on + time off)
e.g:
- 2 msec on / (2 on + 8 0ff msec = 20%)
- 20% duty cycle = on time 2 msec and off time 8 msec.
What is Attenuation
Reduction of acoustical energy as it passes through soft tissue.
What tissue type produces the highest absorption?
Tissues with high collagen and protein content
- muscles
- tendon
- ligaments
- joint capsules
Depth of penetration at 3 MHz?
Greater heat production in superficial layers. (TMJ)
- 1-2 cm
Depth of penetration at 1 MHz?
Increased heat production in deep layers/tissues.
- </= 5 cm
What intensity range will result in desired thermal effects?
Continuous US: Range 0.5 - 3 w/cm2
What can cause undesirable effects to thermal US?
- Excessive high temperatures may produce overheating of periosteal tissue.
- Insufficient coupling agent may produce discomfort “hot-spot”.
What to do in the instance of periosteal pain
- Reduce intensity (w/cm2)
- Increase surface area of treatment if periosteal pain is expressed.
- Add more coupling agent
Typical duty cycle for nonthermal intervention?
20-50% duty cycles.
What may cause diffusional changes in cell membranes?
Stable Cavitation
Goals and Indications of US?
- Modulate pain
- increase tissue extensibility
- Reduce soft-tissue inflammation
- Accelerate tissue healing
Precautions to US?
- Healing Fractures
Contraindication to US: Physiological
- Impaired circulation
- Impaired sensation and cognitive functions
- Malignant tumors
- Over area of thrombophlebitis
- Active Bleeding
Contraindications to US: Surgical
- Joint cement
- Plastic components
- Cardiac Pacemakers
Contraindications to US: body regions/part, areas to avoid during pregnancy?
- Abdomen, low back, uterus during pregnancy
- Vital areas; brain, ears, eyes, cervical ganglia, carotid sinus, reproductive organs
How to select the appropriate sound head size
Effective Radiation Area (ERA) 1/2 the size of the treatment area
What area size should we not cover/treat with US?
2-3 times the size of the ERA
