L4/5: Therapeutic ultrasound Flashcards
What are the 3 uses of ultrasound?
- Therapeutically used for real‐time imaging
- Medical uses for destroying tissue
- Similar to laser (search for kidney stones)
It was shown that patients who already knew about ultrasounds had ____ (better/worse) outcomes.
better
What is ultrasound?
sound energy of frequencies <20,000Hz mechanical energy produced by longitudinal waves which compress and rarefy materials

Therapeutic US has frequencies between____ and ____ MHz
0.75; 3

What are 5 things that US produce?
- Piezo‐electric crystals (e.g. Quartz) are crystalline solids which respond by changing thickness in response to an applied voltage
- Thickness changes in an oscillatory manner
- Crystal cut in thickness to naturally vibrate as a desired frequency
- Held in contact with metal faceplate of transducer
- Transforms electric to mechanical energy

What are the 2 types of ultrasound?
- Therapeutic
- Diagnostic
What are 4 characteristics of ultrasound?
- Longitudinal waves
- Mechanical compressions and rarefaction
- Requires a medium for transmission e.g. water, gel
- Follows same rules of reflection, absorption, refraction and dispersion

What does ultrasound reflection and refraction look like? How does this help therapeutically?
Access deep tissue

What does the absorption of US look like? What does this lead to?
leads to heat generation in the tissue
Can penetrate deeper than hot packs..etc - ~5 cm

What are 4 features that the ultrasound units consist of?
- Oscillating voltage to drive the transducer
- Controlling circuit which can turn on oscillator on or off to give pulsed US (2ms)
- Resistance circuit to control the amplitude (w/cm2)
- Meter which measures electrical oscillations NOT the vibration of the crystal
What does an ultrasound head look like?
ADD

Sound waves need a _____ to be conducted.
medium
___ is a poor conducting medium. _____ and ____ are the best mediums.
Air; US gel; water
What is ultrasound attenuation?

What is acoustic impedence?
How much is absorbed by the tissue
The transmission of sound waves depends on on the _____ of the tissue and the _____ of the beam
acoustic impedance; direction
At boundaries between tissues – some _____ and ______ occurs, which may May alter both the intensity and direction of the beam
reflection; refraction
Bone or tissue that are full of protein absorb ultrasound ____ (more/less) readily. Why must we be careful?
more
Must be careful if bone is superficial can heat up
Sound waves can pass _____ (well/poorly) through fatty tissue
well
Clinical implication ensure sound head is ______ (parallel/perpendicular) to skin to ensure maximum penetration
perpendicular
What are the 5 treatment parameters of US?
- Mode
- Frequency
- Intensity
- Duration
- Treatment area size
What are the 2 types of mode for US?
- Continuous
- Pulsed
What are 2 characteristics of the continuous mode of US?
- Sound energy remains constant
- US energy produced 100% of time

What are 2 characteristics of the pulsed mode of US?
- Energy is periodically interrupted
- No US energy during ‘off’ period



















