Week 3- Ultrasound and Laser, Thermo/Cold Therapy and Short Wave Diathermy Flashcards
ULTRASOUND AND LASER
ULTRASOUND AND LASER
What is ultrasound?
- Therapeutic modality where high-frequency sound waves are transmitted through a wand or probe into the body.
- Sound waves lead to vibrations of the molecules in the body.
Sound waves can be either _______,__________, or ____________.
- reflected
- refracted
- absorbed
What are the 2 main equipment components for ultrasound?
- generator
- applicator
The generator is the “___ ____” of the US device that generates the high-frequency alternating current that is transmitted through the applicator.
“big box”
The applicator is composed of __________ and ___________ crystal in the soundhead.
- soundhead
- piezoelectric
What does the piezoelectric crystal do?
Expansion and compression of the crystal produces the sound waves.
What does the soundhead do?
Acoustic energy from the crystal is conducted to the sound head then through a conductive gel into the skin.
Is the crystal perfectly uniform? What does this lead to?
- No
- Leads to nonuniformity of the intensity of the beam (beam nonuniformity ratio (BNR))
What is spatial peak intensity?
Power of beam at highest point of effective radiating area.
What is spatial average intensity?
total power (watts) across the transducer head (cm²) usually what is recorded for intensity during treatment. (W/cm²)
What is beam non-uniformity ratio?
Ratio of spatial peak intensity and spatial average intensity.
What does a beam non-uniformity ratio of 1:1 mean?
Means the beam is close to uniform throughout.
- What is absorption?
- What is refraction?
- What is Reflection?
Absorption
-When the kinetic energy of movement is absorbed by tissue and transformed into thermal energy.
Refraction
-Ultrasound signal is deflected from a straight path and the angle of deflection is away from the transducer.
Reflection
-Ultrasound waves are deflected towards the transducer.
What are standing waves? What reduces them?
- Standing waves are when reflected waves interact with waves going in and creates more energy.
- This is reduced by keeping the sound head moving.
Intensity is the power of the ultrasonic energy and is expressed as __/____. There are no difinitive guidelines for intensity but continuous (thermal) is typically __-__ W/cm².
- W/cm²
- 0.5-3 W/cm²
What is attenuation in regards to US?
-Reduction of acoustical energy as it passes through soft tissue.
- Do absorption, reflection, and refraction affect attenuation?
- Absorption is highest in tissues of ________ density.
- Reflection of acoustic waves can create ________ waves and thus an increased intensity.
- Yes
- greater
- standing waves
Rate these in order from low attenuation to high attenuation:
- Muscle
- Skin/Tendon
- Bone
- Cartilage
- Blood/Fluids
LOW 1.) Blood/Fluids (3%) 2.) Muscle (24%) 3.) Skin (39%)/Tendon (59%) 4.) Cartilage (68%) 5.) Bone (96%) HIGH
- Frequency is the _______ of waves per second delivered.
- What are the 2 most common frequencies and how deep do they penetrate?
-number
- 3MHz (UP TO 2.5cm DEEP)
- 1MHz (UP TO 5cm DEEP)
3MHz leads to greater heat production in _________ layers due to increase in scatter (________) of sound waves in superficial tissue.
- superficial
- attenuation
1MHz heats _______ layers due to less scatter in superficial tissue, thus more energy able to penetrate deeper.
deep
What is duty cycle (mode) of US?
Fraction of time the US energy is on over one pulsed period (time on + time off)
What are the types of duty cycles (modes)?
- Continuous (thermal)- US is applied at a constant energy level; duty cycle 100%
- Pulsed (nonthermal)- duty cycle range usually 5%-50%.