PAM Ultrasound & Phonophoresis 2 — Questions and Answers
Question 1: Which tissue type has the highest ultrasound absorption coefficient?
- Adipose tissue
- Cortical bone (Correct answer)
- Skeletal muscle
- Articular cartilage
Correct answer: Cortical bone
Cortical bone has the highest absorption coefficient because its density and protein content cause maximal attenuation of ultrasound energy.
Question 2: When using ultrasound over a superficial metal implant, the clinician should:
- Avoid the area entirely due to risk of overheating (Correct answer)
- Apply standard continuous US directly over the implant
- Use pulsed US at low intensity over the implant site
- Increase intensity to compensate for metal reflection
Correct answer: Avoid the area entirely due to risk of overheating
Metal implants can reflect and concentrate ultrasound energy, creating dangerous hot spots; the area should be avoided.
Question 3: The term 'cavitation' in therapeutic ultrasound refers to:
- Formation and oscillation of gas bubbles in tissue fluids (Correct answer)
- Conversion of acoustic energy to heat
- Reflection of sound waves at tissue interfaces
- Piezoelectric crystal vibration
Correct answer: Formation and oscillation of gas bubbles in tissue fluids
Cavitation involves the formation and oscillation (stable) or collapse (unstable) of gas-filled bubbles in biological fluids exposed to ultrasound.
Question 4: For phonophoresis to be effective, the drug vehicle (gel/cream) must:
- Contain alcohol as a base for better penetration
- Be acoustically transparent and allow US transmission (Correct answer)
- Have high viscosity to hold the medication on the skin
- Be pre-warmed to body temperature before application
Correct answer: Be acoustically transparent and allow US transmission
The coupling medium must be acoustically transparent so ultrasound energy is not absorbed by the vehicle before reaching the target tissue.
Question 5: A 1-MHz ultrasound unit will penetrate to approximately what tissue depth?
- 1–2 cm
- 2–5 cm (Correct answer)
- 5–7 cm
- 8–10 cm
Correct answer: 2–5 cm
1-MHz ultrasound penetrates to approximately 2–5 cm, making it suitable for deeper structures than the 3-MHz frequency.
Question 6: Which duty cycle is considered 'pulsed' ultrasound?
- 100%
- 75%
- 20% (Correct answer)
- 50% or less
Correct answer: 20%
A duty cycle of 20% (or any value below 50%) is typically classified as pulsed, significantly reducing the thermal effect.
Question 7: Stable (non-inertial) cavitation is considered therapeutic because it:
- Destroys cell membranes to release cytokines
- Increases cell membrane permeability and microstreaming (Correct answer)
- Generates extreme local temperatures exceeding 100°C
- Causes permanent disruption of collagen cross-links
Correct answer: Increases cell membrane permeability and microstreaming
Stable cavitation produces rhythmic bubble oscillations that enhance membrane permeability and drive acoustic microstreaming, facilitating cellular repair processes.
PAM Ultrasound & Phonophoresis 2
Which tissue type has the highest ultrasound absorption coefficient?