*5.PTA 200-Ultrasound Flashcards
16,000 – 20,000 Hz
Audible sound
10 MHz (10,000,000 Hz)
Diagnostic ultrasound
1-3 MHz (1,000,000 Hz – 3,000,000 Hz)
Therapeutic Ultrasound
Primary mechanism for energy transfer with ultrasound interventions is
CONVERSION
the control panel. Plugs into the wall and provides the electrical energy (alternating current) to be converted to sound energy.
Generator
inside the transducer of the ultrasound machine: converts electric energy into mechanical energy as sound waves via the reverse piezoelectric effect. Electrical energy causes rarefactions and compressions of the crystal which create the waves.
Crystal
transfers the acoustic energy created by the vibrating crystal to the skin and underlying tissues.
Soundhead
the “wand” that is held and moved to administer the ultrasound treatment. The “handle” of the machine. Houses the cable, crystal and soundhead.
Applicator
Affects the depth of penetration. -Amount of cycles of waves per second. (Hertz)
Frequency
*Increased intensity does not increase depth of penetration!!! - amount of energy being delivered per unit of area. (Watts per square centimeter.)
Intensity
can penetrate up to 6 cm deep.
*Remember: higher frequencies produce LESS penetration
*helpful memorization tool: “I’m #1!” The winner goes to the frequency that penetrates the most.
(Most effects at 1.25 cm) Energy is absorbed 3 x’s faster, therefore will heat superficial tissue more quickly and penetrate less.
1 MHz
can penetrate up to 2.5 cm deep
(Most effects at 1.25 cm) Energy is absorbed 3 x’s faster, therefore will heat superficial tissue more quickly and penetrate less.
3 MHz
conversion of the mechanical energy to heat energy; absorption increases with increased frequencies which is why higher frequencies penetrate less
Absorption
sound waves are absorbed by the tissues as they pass through and therefore the deeper they travel, the less intense they become. (thus the ½ value layer rule).
Attenuation
energy is directed away from the surface at an angle equal and opposite to the initial angle; 100% reflection of US waves in air therefore must use a coupling medium to transfer the waves to the tissue rather than being reflected away.
Reflection
when a reflected wave superimposes on the original wave; causes cellular damage of blood vessels *Will not happen if keep the sound head moving.
Standing wave
the alternating current is constant, therefore the stimulus is constant. This allows heat to be built up by the constant friction/vibration of the tissues. Causes thermal effects.
Continuous
the alternating current is intermittently interrupted. Less heat built up, therefore creates non-thermal effects. Recommended at 20% duty cycle (or 80% interrupted).
Pulsed
describes the physical area on the sound head that transmits the sound waves. *Treatment area should be no bigger than 2 x’s the ERA for the sound head! never 100%
ERA- effective radiating area
describes the uniformity of the sound waves being emitted; cannot be 100%, but closer to 1:1 ratio the more consistent the delivery of sound waves will be. Should not exceed 5:1 ratio. *Higher BNR’s require more movement of sound head to avoid developing “hot spots.”
BNR- beam nonuniformity ratio
- Increased tissue extensibility- only lasts approx 10 minutes, therefore must stretch with or immediately after
- Decreased muscle spasm
- Increased nerve conductivity
- Increased metabolism
- Increased circulation
- Decreased pain perception
Thermal Effects
- Increased histamine release
- Increased phagocytosis
- Increased fibroblasts
- Tissue regeneration
- Wound healing
- Cell membrane alteration- increased permeability from stable cavitation
- Acoustic microstreaming- improved cell membrane structure and function, helps with pain
Nonthermal effects
- Soft tissue repair/wound healing
- Resolving pitting edema
- Contractures/adhesions
- Pre-stretch or during stretch
- Chronic inflammation
- Bone healing
- Pain/spasm
Indications
- Malignancy
- Pregnancy
- Cardiac dysfunction
- Pacemakers
- Areas of impaired sensation
- Infected areas
- Over eyes/spine/heart/spinal cord/joint cement
Contraindications
Use of anti-inflammatory medicine as part of the medium. Sound waves penetrate skin and take medicine ions with them. *Medicine becomes systemic! Caution must be taken to not over-dose a patient who is already taking steroid anti-inflammatory medicines.
Phonophoresis
PULSED
Duty cycle (Phonophoresis)
LOW
Intensity (Phonophoresis)
