Ultrasound

vibrate

sound waves cause molecules to ______

medium

sound needs to pass through a ______ (solid, liquid, gas)

longitudinal and transverse

types of sound waves

longitudinal wave

parallel to sound wave, pass through liquids and solids, doesn’t work on bone

transverse wave

perpendicular to sound wave, pass through solids but not liquids

cylindrical

what shape beam does the sound head produce?

3 cm

how deep does 3 MHz go?

5 cm

how deep does 1 MHz go?

more focused

the larger the sound head, the ________ the beam

when beams pass through tissue

when does divergence occur?

the crystal in the sound head

what propagates sound?

reflection, refraction, absorption

three types of scattering

reflection

wave strikes and reverses direction, happens when there is no medium

refraction

wave bends, happens when there is a damaged crystal

absorption

transfer of energy, less energy is transmitted by each layer of skin as it goes deeper and deeper

hot spot

caused by a standing wave

large amount of heat absorption

standing wave - reflected sound waves and new sound waves coming into contact and lead to a _________

move sound head continuously, not too slow

how to avoid hot spots?

16-20 kHz

audible sound frequency

20 kHz

greater than _____ is ultrasound

less

higher frequency » ____ divergence

more

lower frequency » ____ divergence

superficial tissue

when to use a higher frequency?

use medium, keep head directly on skin

how to reduce scattering?

acoustical impedance

determines the amount of energy that will be scattered or absorbed at different boundary levels

deep tissue

when to use a lower frequency?

mild warming sensation

what should the patient feel during ultrasound tx?

5 minutes

rule of thumb length of tx time for 3 MHz

7-8 minutes

rule of thumb length of tx time 1 MHz

increase tissue elasticity, blood flow, pain threshold, enzymatic activity, improve conduction velocity, decrease spasms

physiologic responses

104-113 degrees

For therapeutic affects the tissue temp must be raised to _______ for at least 5 minutes

effective radiating area

area under the part of the sound head that actually produces waves

if too large blood rushes into area and cools it off

why is the ERA small?

vibration

what should the patient NOT feel?

no

does ultrasound increase skin temperature?

increase temperature, affect viscoelasticity of collagen, easier to stretch, good prior to friction massage

how does ultrasound help with joint contracture and scar tissue

heat activates large diameter fibers, gate control theory

how does ultrasound help with pain reduction

reduces muscle spindle activity

how does ultrasound reduce muscle spasm

brings nutrients into area, flushes out toxins and bacteria

how does ultrasound help with chronic inflammatory conditions

creep

muscle length can change under low loads over long periods of time

phonophoresis

use of ultrasound to drive medication through skin

less burning or damage, penetrates deeper

advantages of phonophoresis over iontophoresis

ultrasound gel, mineral oil, glycerol

good mediums to use

direct, immersion, bladder

exposure techniques

increase by 0.5

how does intensity change for immersion ultrasound

0.5-0.75

intensity for knee, iliac crest, elbow

0.75-1

intensity for forearm, anterior leg, gastroc, upper arm, lateral leg

1-1.5

intensity for gastroc, upper arm, lateral leg

1.5-2

intensity for thigh, buttocks

2-2.5

intensity for thigh, buttocks (large mammals)

eyes, acute injuries, poor circulation, thromboflombitis, genitals, pregnant uterus, pacemaker, tumor, epiphyseal plates, total joint replacements, infection

contraindications

2-3 times the head

treatment area size