Non-Systems: Therapeutic Modalities: UltrasoundL Biophysics Flashcards
Spatial Characteristics: Continuous
- Spatial characteristics predominant
Spatial Characteristics: Continuous US applied to achieve
- Thermal effects
Spatial Characteristics: Energy Intensity: Hot Spot
- Not uniformly distributed over the surface of the transducer and typically concentrated more the one area developing a hot spot
Spatial Characteristics: Energy Intensity: Hot Spot: Mitigation
- Moving the sound head
- Pulsed ultra sound
Spatial Characteristics: Spatial average intensity
- Total power watts divided by area cm^2
- Typically the measurement used to document ultrasound treatments
Spatial Characteristics: Beam non-uniformity ratio
- Ratio of spatial peak intensity to spatial average intensity
- Low BNR=More uniform
- High BNR=Less uniform
- Low BNR is more desirable
- BNR should be between 2:1 and 6:1
Temporal Characteristics: Pulsed
- Temporal characteristics predominant
Temporal Characteristics: Pulsed ultrasound used when
- Non thermal effects are desired
Temporal Characteristics: Duty Cycle
- The fraction of time the ultrasound energy is on over one pulse period
Temporal Characteristics: Duty Cycle Examples
- 20% duty cycle= 2 msec on to 8 seconds off (2/(2+8)
- Less than 50% duty cycle (5 msec) is generally considered pulsed ultrasound
Temporal Characteristics: Temporal Peak intensity
- The peak intensity of ultrasound during the on-time phase of the pulsed period
Temporal Characteristics: Attenuation
- The reduction of acoustic energy as it passes through soft tissue
Temporal Characteristics: Absorption
- Highest in tissues that contain collagen and protein
Depth of Penetration: 3MHz
- Greater heat production in superficial layers
- Tissues 1-2.5 cm deep
Depth of Penetration: 1MHz
- Increased heat production in deep layers
- Tissues up to 6cm deep
