Ultrasound & Laser Flashcards
what is ultrasound
- therapeutic modality where high fq sound waves are transmitted through a wand or probe into the body
- sound waves lead to vibrations of the molecules in the body
- waves either reflected, refracted or absorbed
what equipment is used with ultrasound
- two main components
- generator and applicator
generator for ultrasound
- US device
- generates the high fq alternating current that is transmitted through the applicator
applicator for ultrasound
sound head and piezoelectric crystal
beam nonuniformity ratio
ratio of spatial peak intensity and spatial avg intensity
spatial peak intensity
power of beam at highest point of effective radiating area
spatial average intensity
W/cm^2
total power across the transducer head usually what is recorded for intenisty during treatment
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 toward the transducer
standing waves
- reflected waves interacting with waves going in and creates more energy
- reduced by keeping sound head moving
intensity
power of ultrasonic energy
attenuation
reduction of acoustical energy as it passes through soft tissue
what affects attenuation
absorption, reflection and refraction
when is absorption highest
in tissues of greater density
reflection of acoustic waves can create what
standing waves –> increasing intensity
frequency
of waves per second delivered
3 mHz =
up to 2.5cm deep
greater heat production in superficial layers due to increase in scatter of sound waves in superficial tissues
1 mHz
5cm deep
heats deep layers due to less scatter in superficial tissue, more energy able to penetrate deeper
duty cycle
mode
fraction of time the US energy is on over one pulse period
continuous US
thermal
US is applied at a constant energy level, duty cycle 100%
pulsed US
non-thermal
duty cycle range from 5-50%
indications for use for US
modulate pain increase connective tissue extensibility reduce muscle spasm increase tissue temp increase blood flow facilitate healing
contraindications for US (8)
impaired circulation impaired cognitive fxn absent sensation cancer joint cemet directly over plastic components over vital areas pregnancy
precautions (4)
acute inflammation
open epiphyseal plates
healing fx
breat implants
proposed impact for thermal US
increase pain threshold increased collagen extensibility alteration of nerve conduction velocity increased enzymatic activity increased tissue perfusion
cavitation
non-thermal
alternating compression and expansion of small gas bubbles in tissue fluids due to the mechanical pressure waves of the acoustic waves
stable cavitation
gas bubbles resonate without tissue damage; may be responsible for diffusional changes in cell membrane
unstable cavitation
severe collapse of gas bubbles during compression phase of pulsed US which can result in local tissue damage due to high temps
acoustic streaming
forward movement of fluid and ions along boundaries of cell membranes
when would you use immersion technique
- when criteria for direct contact can’t be safely met
- used on irregular surfaces, sensitive or broken integument
what is the immersion technique
- plastic container with water high enough to cover body part
- US head placed 1cm away from treatment area
- perform rhythmical movement over area maintaining perpendicular to treatment area
phonophoresis
using US sound waves to attempt to deliver meds through skin
if you have an impairment of soft tissue shortening or pain, what US would you use
thermal
thermal duty cycle:
100%
if thermal/nonthermal US, and depth is 1-2 cm what is the fq., intensity and duration
fq: 3MHz
intensity: 0.5-1.0 W/cm^2
duration: 5-10min
if thermal/nonthermal US, and depth is <5 cm what is the fq., intensity and duration
fq. : 1MHz
intensity: 1.5-2.0 W/cm^2
duration: 5-10min
if you have an impairment of delayed tissue healing or pronlonged inflammation, what US would you use
non thermal
non thermal duty cycle
20%, 50%
laser
light amplification by stimulated emission of radiation
low level lasers peak power is what
equal or less than 500mW
high intensity lasers peak power is what
greater than 500mW
laser physiological effects
improve mitochondrial fxn promote collagen production modulate inflammation inhibit bacterial growth promotes vasodilation increase nerve conduction
laser contraindications
direct eye exposure
pregnancy
malignancy
following acute injury where a hemorrhage is possible
open growth plates
over the thyroid or other endocrine gland
