Ultrasound Flashcards
Indications for Ultrasound
Soft tissue shortening Pain control Repair of soft tissue injuries Dermal ulcers/Plantar warts Tendon injuries Resorption of calcium deposits Bone fractures Carpal tunnel syndrome Anti-inflammatory
Advantage
Primary advantage of US over other nonacoustic heating modalities is that TISSUES HIGH IN COLLAGEN (tendons, ligaments, fascia )AND OTHER DEEP TISSUES MAY be selectively heated to a therapeutic range without causing a significant tissue temperature increase in skin or fat
minimum desired tissue temp for thermal effects
104 F (40C)
what is ultrasound
Ultrasound is an oscillating sound pressure wave with a frequency greater than the upper limit of the human hearing range, which is usually 20KHz
Therapeutic US emits high frequency acoustic energy to produce thermal and non-thermal also called mechanical effects in tissue
Ultrasound waves cause
cellular vibration of molecules, increasing friction, causes increase in kinetic molecular energy within the tissues
Attenuation
absorption, reflection, and refraction of the wave
absorption- responsible for half of the loss of energy
Attentuation is greatest in what types of tissues
with high collagen content
tendon, cartilage, bone
Absorption
conversion of mechanical energy into heat
high collagen tissue absorb the most soundwaves
as you increase protein content you increase absorption
Continuous US effect
thermal effects
increasing tissue temperature
Pulsed US effect
non thermal (mechanical)
acoustic streaming
microstreaming
cavitation
Clinical effects of thermal US
Increased extensibility of collagen fibers tendons joint capsule Decreased joint stiffness Reduction in muscle spasm Pain modulation Increased blood flow Increased metabolic rate Increased nerve conduction velocity
Primary advantage of US vs superficial heat
selective heating of tissues high in collage
US heats deeper
US heats smaller area
Stable Acoustic Cavitation
Formation, growth and pulsation of gas or vapor filled bubbles caused by US; bubbles oscillate in size do not burst
Microstreaming
Microscale eddying that takes place near any small, vibrating object
Occurs around the gas bubbles set into oscillation by cavitation
Acoustic microstreaming
Unidirectional movement of fluids along cell membrane boundaries
Produces high viscous stresses
Alters membrane structure & function
Increased permeability to ionic influx
Effects from cavitation and microstreaming
Stim. of fibroblast activity … increases protein synthesis & tissue repair
-Increased blood flow
-bone healing & repair of non-union fractures
Inc in nitric oxide synthesis
Inc in intracellular calcium levels
Inc cell permeability
Ultrasound Intensity
0 - 3 W/cm2
The amt. of acoustic power per unit area of the sound head
Expressed in watts per centimeter squared ( W/cm2 )
Lower Intensity & pulsed US used for
acute conditions/ thin tissue
produces nonthermal effects
if superficial bone- lower intensity
High Intensity and continuous US used for
chronic conditions& thick tissue
Ultrasound Frequency
Determined by number of times crystal deformed/sec. 2 most common utilized in U.S. 1.0 MHz 3.0 MHz Determines depth of penetration
relationship between frequency and depth of penetration
inverse relationship
Penetrating depths:
1.0 MHz Frequency: 2-5 cm
3.0 MHz Frequency: 1-2 cm
Lower sound frequency penetrates deeper secondary to having a longer wavelength vs. higher sound frequency
Absorption rate increases with higher frequency
Effective Radiating Area- ERA
Total area on surface of transducer producing soundwave
Ideally ERA should match size of transducer
Treatment area should not exceed 2 times ERA
Beam Non Uniformity Ratio - BNR
The ratio of the spatial peak intensity to the spatial average intensity
The higher the piezoelectric quality of the transducer embedded in the sound head, the lower the BNR should be
Can form hotspots that can cause tissue damage- move sound head around area throughout application to avoid this
Continuous Delivery
100%
Uninterrupted emission of acoustic waves over time
Intensity remains the same
Induces a higher thermal effect in the tissue over time
Pulsed Delivery
20%
Periodic interruption or pulsing of such waves
Avg intensity reduced over time
The longer the inter-pulse duration, the less thermal heating in the tissues
US used for:
Soft tissue shortening Pain control Dermal ulcers Surgical skin incisions Tendon and ligament injuries Bone fractures Carpal tunnel syndrome Phonophoresis
Phonophoresis
Application of US in conjunction with a topical drug preparation as the US conduction medium
Generally used in rehabilitation for treatment of tissue inflammation, such as tendonitis or bursitis
US enhances delivery of drug through the skin, thereby delivering the drug for local and systemic effects
Hydrocortizone/Dexamethasone (anti-inflammatory) and Lidocaine (analgesic)
US increases __ of __ viathe process of __
US increases permeability of STRATUS CORNEUM via process of cavitation
how US alters pore size
US alters pore size and creates more pores, drug is transported thru pores secondary to difference in concentration on either side of skin
Recommended Tx Parameters for Phono
Frequency: 3MHz to optimize absorption through the skin
Pulsed 20% Duty Cycle :to avoid heating of any inflammatory condition
Intensity: 0.5 - 0.75 W/cm2
Time:5- 10 minutes
Be sure drug preparation used should transmit US effectively
10% hydrocortizone more effective than 1% in relieving pain associated with tendonitis and bursitis
US Contraindications
Malignancy Pregnancy CNS tissue Joint cement Plastic components Pacemaker Thrombophlebitis Eyes and reproductive organs
US Precautions
Acute inflammation
Epiphyseal plates
Fractures
Breast implants
When does Patient start feeling warmth from US
When Tx goal is to increase tissue temp, pt should report feeling of “warmth” within 2-3 minutes
Frequency of 1 MHz @ intensity of 1.5 - 2.0 W/cm2
Frequency of 3 MHz@ intensity of 0.5 W/cm2
Parameters for Soft Tissue Shortening
Thermal Duty Cycle 100% Depth of problem 1-2 cm Ultrasound frequency- 3 MHz Ultrasound intensity- 0.5 W/cm2 Duration of Tx- 5-10 min/2 x ERA
OR Duty Cycle 100% Depth of problem <5 cm Ultrasound frequency- 1 MHz Ultrasound intensity- 1.5 - 2 W/cm2 Duration of Tx- 5-10 min/2 x ERA
Parameters for Delayed soft tissue healing or Prolonged inflammation
Nonthermal Duty Cycle 20% Depth of problem 1-2 cm Ultrasound frequency- 3 MHz Ultrasound intensity- 0.5 -1 W/cm2 Duration of Tx- 5-10 min/2 x ERA
OR Duty Cycle 20% Depth of problem <5 cm Ultrasound frequency- 1 MHz Ultrasound intensity- 0.5 -1 W/cm2 Duration of Tx- 5-10 min/2 x ERA
