1. Therapeutic Ultrasound
Chapter 8

2. Description
Acoustical energy (sound waves) above the range of human hearing
Therapeutic range: 0.75 to 3.3 MHz
Effects:
Thermal
Nonthermal (mechanical)

3. Uses Calcific bursitis Inflammatory conditions Joint contractures Pain
Muscle spasm
Acute orthopedic injuries (low pulses, low intensity)

4. Production of Ultrasound
An alternating current is passed through a crystal
The current causes the crystal to vibrate
Electropiezo effect
Vibrating crystal produce high-frequency sound waves

5. Effective Radiating Area (ERA)
Area of the crystal that actually produces sound waves
Produces more than 5% of the energy at 5 mm from the transducer face
ERA is always smaller than the transducer face
Energy is concentrated near the center
ERA

6. Beam Profile Multiple waves emerge from the head
Energy diverges as it moves away from the source
Energy is uniform close to the head
Near zone (Fresnel zone)
Becomes less consistent farther away from the head
Spatial peak intensity
Spatial Peak Intensity

7. Beam Nonuniformity Ratio (BNR)
Spatial Peak Intensity
Describes the amount of variation in the beam
Ratio between:
Spatial peak intensity (SPI)
Average intensity (SAI - metered output)
BNR = SPI/SAI
Perfect beam would have a BNR of 1:1
Minimally acceptable BNR is 8:1
The actual peak output is equal to the SAI * the BNR
10 W total output * 6:1 BNR
60 watt SPI
Spatial Average Intensity (Displayed on the unit)

8. Modes of Application Continuous
Ultrasonic energy is constantly produced
Can produce thermal effects based on:
Output intensity
Treatment duration
Pulsed
Ultrasonic output is regularly interrupted
Produces nonthermal effects

9. Continuous Output (100% Duty Cycle) Pulsed Output (67% Duty Cycle)
Ultrasonic output is cycled “On” and “Off”
On = Pulse length
Off = Pulse interval
Expressed as a Duty Cycle
ON/(ON+OFF) * 100
20mSec/(20mSec+10mSec) * 100
20/30 * 100
67%
Continuous Output (100% Duty Cycle)
Pulsed Output (67% Duty Cycle)

10. Output Frequency Measured in megahertz (MHz)
1 MHz = 1,000,000 waves per second
Determines the depth of effects
1 MHz Output
Penetrates 5 to 7 cm
Thermal effects last longer
More divergent beam
3 MHz Output
Penetrates 2 to 3 cm
Heats 3 times faster than 1 MHz output
More collimated beam

11. Power and Intensity Spatial Average Intensity
Spatial Average Temporal Peak Intensity
Spatial Average Temporal Average Intensity

12. Spatial Average Intensity (SAI)
Describes the energy per unit of area
Total output (watts)/area
Watts/effective radiating area (cm2)
W/cm2
15 watts being applied with a 10 cm2 ERA
15 Watts / 10 cm2
1.5 W/cm2

13. Power Measures – Pulsed Output
Spatial Average Temporal Peak Intensity (SATP)
The average energy delivered during the “On” time of the duty cycle.
Spatial Average Temporal Average Intensity (SATA)
Energy delivered over time
Spatial Average Intensity * Duty Cycle
Meaningful only during pulsed output

14. Biophysical Effects
Thermal

15. Thermal Effects Increased sensory nerve conduction velocity
Increased motor nerve conduction velocity
Increased extensibility of collagen-rich
Increased vascular permeability structures
Increased collagen deposition
Increased blood flow
Reduction of muscle spasm
Increased macrophage activity
Enhanced adhesion of leukocytes to damaged endothelial cells

16. Heating Classifications
Increase Used For
Mild 1°C Mild inflammation Accelerate metabolism
Moderate 2° – 3°C Decreasing muscle spasm Decreasing pain Increasing blood flow Chronic inflammation
Vigorous 3° – 4°C Tissue elongation Scar tissue reduction

17. Heating Rate Heating rate and magnitude is based on: Duty cycle
Output frequency
Intensity
Target tissues
Size of the treatment area

18. Thermal Effects Same as other heat modalities
Smaller volume of tissue
Shorter duration of effects
Preheat the skin with a moist heat pack
Decreases the time to reach vigorous heating
Poorly vascularized, collagen-rich tissues are preferentially heated
Fascia, tendon, scar tissue
Tissues containing an increased proportion of fluid do not heat as well
Adipose tissue, articular fluid

19. Biophysical Effects
Nonthermal

20. Nonthermal Effects Granulation tissue production Synthesis of protein
Increased cell membrane permeability
Altered rates of diffusion across the cell membrane
Increased vascular permeability
Secretion of cytokines
Increased blood flow
Increased fibroblastic activity
Stimulation of phagocytosis
Granulation tissue production
Synthesis of protein
Synthesis of collagen
Reduction of edema
Diffusion of ions
Tissue regeneration
Formation of stronger deformable connective tissue

21. Nonthermal Application
Pulsed output
20 to 25% duty cycle
Nonthermal output intensity
Continuous output
100% duty cycle
Output intensity of less than 0.3 W/cm2

22. Acoustical Streaming Ultrasound causes interstitial fluids to flow
Fluids strike cell membranes
Produce eddy currents
Eddy currents displace ions and molecules
Alter:
Cell membrane permeability
Cellular function

23. Effect on Injury Response

24. Cellular Response Acoustical streaming: Thermal effects:
Increases cell membrane permeability
Alters cell membrane diffusion rate
Increased histamine release
Mast cell degranulation
Increased rate of protein synthesis
Thermal effects:
Increased cell metabolism
Increased rate of inflammation

25. Inflammation May lead to an earlier onset of proliferation
Increased fibroblast proliferation
Release of growth factors and platelets
Increased macrophage activity
Leukocytes bind to damaged endothelial cells
Cell division is increased

26. Inflammation Frequency Specificity 1 MHz Output 3 MHz Output
Release of preformed fibroblasts
3 MHz Output
Increased synthesis and secretion of fibroblast precursors
Increased in areas of high collagen concentration

27. Blood and Fluid Dynamics
May increase blood flow for 45 minutes
Thermal effects
Decreased vascular tone
Histamine release
Causes vasodilation
Moist heat application prior to treatment decreases net increase in blood flow

28. Pain Control Direct Pain Reduction
Increased nerve cell sodium permeability
Alters nerve function
Increases pain threshold
Indirect Pain Reduction
Increased blood flow
Increased capillary permeability
Increased oxygen delivery
Decreased muscle spasm

29. Muscle Spasm Reduced secondary to: Decreased pain
Altered nerve conduction velocity
Increased temperature (counterirritant effect)
Muscle relaxation

30. Tissue Elasticity
Ultrasound preferentially heats collagen-rich tissues (tendon, fascia, scar tissue)
Temperature must be increased 7.2°F
Stretching window lasts approximately 3 minutes following the treatment
Place tissues on stretch during application
Perform stretching/mobilization immediately following the treatment
Multiple treatments are required to gain length

31. Wound Healing Tendon Healing Continuous US application may:
Increase tensile strength
Increase collagen deposition
Skin Ulcers
3 MHz, low-intensity pulsed output may assist the healing process
Cover the wound with an occlusive dressing

32. Electromagnetic Field
In vitro bone deformation produces piezoelectric currents and streaming potentials
Electromagnetic (EM) devices are based on Wolff’s Law that bone responds to mechanical stress: Exogenous EM fields may simulate mechanical loading and stimulate bone growth and repair
Clinical efficacy very controversial
Buckwalter, Einhorn, Simon (ed.) Orthopaedic Basic Science 2nd ed. AAOS, 1999.

33. Types of EM Devices Microamperes Direct electrical current
Capacitively coupled electric fields
Pulsed electromagnetic fields (PEMF)
Buckwalter, Einhorn, Simon (ed.) Orthopaedic Basic Science 2nd ed. AAOS, 1999.

34. PEMF Approved by the FDA for the treatment of non-unions
Efficacy of bone stimulation appears to be frequency dependent
Extremely low frequency (ELF) sinusoidal electric fields in the physiologic range are most effective (15 to 30 Hz range)
Specifically, PEMF signals in the 20 to 30 Hz range appear more effective than those below 10 Hz
Buckwalter, Einhorn, Simon (ed.) Orthopaedic Basic Science 2nd ed. AAOS, 1999.

35. Ultrasound
Low-intensity ultrasound is approved by the FDA for stimulating healing of fresh fractures
Modulates signal transduction, increases gene expression, increases blood flow, enhances bone remodeling and increases callus torsional strength in animal models

36. Ultrasound
Human clinical trials show a decreased time of healing in fresh fractures
Has also been shown to decrease the healing time in smokers potentially reversing the ill effects of smoking

37. Fracture Healing Low-intensity pulsed output
Accelerates rate of fracture healing for:
Acute fractures
Nonunion fractures
Stress fractures
Requires specialized unit
Biophysical Effects:
Mechanical (sound) energy strikes bone
Microvibration of bone triggers growth (osteogenesis)
PARAMETERS
Frequency 1.5 MHz
ERA 3.88 cm2
Intensity 30 mW/cm2
Treatment Duration 20 minutes Daily

38. Contraindications Acute conditions (thermal mode) Ischemic areas
Areas of impaired circulation
Over areas of deep vein thrombosis
Anesthetic areas
Over cancerous tumors
Sites of active infection or sepsis
Over the spinal cord or large nerve plexus in high doses
Exposed penetrating metal (eg, external fixation devices)
Around the eyes, heart, skull, or genitals
Over the thorax in the presence of an implanted pacemaker
Pregnancy when used over the pelvic or lumbar areas
Over a fracture site before healing is complete
Stress fracture sites or sites of osteoporosis
Over the pelvic or lumbar area in menstruating female patients

39. Where are we going?

40. Ultrsound Ultrasound uses: Therapeutic US widely used for deep heat
Diagnostic (low intensity)
Fracture
Surgical (high intensity)
Therapeutic
Therapeutic US widely used for deep heat

41. Ultrasound Primary clinical use: Soft tissue repair
Pain relief (analgesia)

42. Effective Radiating Area (ERA)
Total area on surface of transducer producing soundwave
Ideally ERA should match size of transducer
Treatment area should not exceed 2-3 times ERA

43. Frequency of Ultrasound
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, unlike ES

44. Frequency of Ultrasound
Inverse relationship between frequency and depth of penetration
Penetrating depths:
1.0 MHz: 2-5 cm
3.0 MHz: 1-2 cm
Absorption rate increases with higher frequency

45. Pulsed vs Continuous Most new generators produce both
Both produce thermal & nonthermal effects

46. Pulsed vs Continuous Continuous: Sound intensity remains the same
Commonly used for thermal effects

47. Pulsed vs Continuous Pulsed: Intensity periodically interrupted
Average intensity reduced over time

48. Physiological Effects of Ultrasound
Thermal effects
Non-thermal effects
Cavitation
Acoustic microstreaming

49. Thermal Effects Clinical effects:
Increased extensibility of collagen fibers
tendons
joint capsule
Decreased joint stiffness

50. Thermal Effects Clinical effects: Reduction in muscle spasm
Pain modulation
Increased blood flow
Increased nerve conduction

51. Thermal Effects Primary advantage of US
Selective heating of tissues high in collagen
Non-thermal effects are occurring

52. Non-thermal (Mechanical) Effects
Primary physiological effects are cavitation and acoustic microstreaming
Cavitation:
Formation of gas-filled bubbles in tissue fluids
Expansion/compression of bubbles either stable or unstable

53. Non-thermal (Mechanical) Effects
Acoustic microstreaming:
Unidirectional movement of fluids along cell membrane boundaries
Produces high viscous stresses
Alters membrane structure & function
Increased permeability to ionic influx

54. Non-thermal (Mechanical) Effects
Potential therapeutic effects from cavitation & microstreaming
Stim. of fibroblast activity increases protein synthesis & tissue repair
Increased blood flow
bone healing & repair of non-union fractures

55. Ultrasound Indications Contraindications Increase deep tissue heat
Decrease inflammation
Decrease muscle spasms
Decrease pain
Increase extensibility of collagen tissue
Decrease pain of neuromas
Decrease joint adhesions
Treat myositis ossificans
Contraindications
Hemorrhage
Infection
Thrombophlebitis
Suspected malignancy
Impaired circulation or sensation
Stress fracture sites
Epiphyseal growth plates
Over the Eyes, Heart, Spine, or genitals

56. Treatment Frequency Ultrasound has cumulative effects
· Daily for 10 days – low irritability and scar
· 3-4 times/week – moderate irritability for weeks
· 2 times /week – high irritability 4-5 weeks
· If no change after 3-4 sessions, change settings or discontinue.
· Stop after treatments

57. Sound Head Movement Never stay stationary
Keep it moving, slow and gentle with constant pressure.
This will minimize the risk of creating unstable cavitation and
Standing waves that is detrimental damaging to soft tissue
1 inch = 1 second

58. Movement of the Transducer
4 cm2/sec
Remaining stationary can cause problems
Moving too rapidly decreases the total amount of energy absorbed per unit area
May cause clinician to treat larger area and the desired temps. May not be attained
Slower strokes can be easier maintained
If patient complains of pain or excessive heat, then decrease intensity but increase time
Apply constant pressure – not too much & not too little

59. Coupling Agents Optimal agent – distilled H20 (.2% reflection)
Modern units have a shut down mechanism if sound head becomes too hot (Dynatron beeps; red lights on Chattanoogas)
Improperly coupled head causes  temp.
Types of agents:
Direct
H20 immersion
Bladder
Reduce amount of air bubbles

60. Direct Coupling
Effectiveness is  if body part is hair, irregular shaped, or unclean
Must maintain firm, constant pressure
Various gels utilized

61. Water Immersion Used for odd shaped parts
Place head approx. 1” away from part
Operator’s hand should not be immersed No metal on part or operator’s hand
Ceramic tub is recommended
If nondistilled H20 is used, intensity can be  .5 w/cm2 because of air & minerals
Don’t touch skin except to briefly sweep skin when bubbles form

62. Bladder H20 filled balloon or plastic bag coated with coupling gel
Use on irregular shape part
Place gel on skin, then place the bladder on the part, and then place gel on bladder
Make sure all air pockets are removed from bladder

63. US Specifics Burning Tissue Density Gel application
Burning the US head with no tissue contact

64. Phonophoresis

65. Description
Use of therapeutic ultrasound to assist in diffusion of medication through the skin
Increases the diameter of skin portals to allow the medication to pass
Pores
Hair follicles

66. Biophysical Effects Medication is introduced over a large area
Relative to an injection
Noninvasive
Medication may not be filtered by the liver
Reducing metabolic elimination of the medicine

67. Transdermal Application
Medication must diffuse through:
Enzymatic barrier of the epidermis
Stratum corneum
Rate-limiting barrier to absorption
Medications must be able to diffuse across this barrier
Medication is stored in subcutaneous tissues for some time before being diffused deeper

68. Skin Influences Medication uptake is improved when the skin is:
Well hydrated
Has a high density of skin portals
Highly vascularized
Relatively thin
“Younger” skin tends to have better diffusion characteristics than “older” skin.

69. Ultrasound Influences on Diffusion
Thermal Effects
Increase kinetic energy
Increase portal cross-section
Increase circulation
Increase capillary permeability
Nonthermal Effects
Altered cell resting potential
Increased cell membrane permeability
Increased molecular permeability

70. Phonophoresis Medications
Either prescription or nonprescription
Low molecular size and weight
Most medications used can be applied transdermally without ultrasound
Controlled medications require a prescription for the patient being treated
Medication is often mixed in an inert base
Base must be able to transmit ultrasonic energy

71. Common Medications Type Indications Example
Corticosteroid Inflammation Hydrocortisone
Dexamethasone
Salicylates Inflammation
Pain
Anesthetic Pain Lidocaine
Trigger points

72. Application Tips Moist heat pack prior to application:
Increase blood flow
Increase kinetic energy
Increase skin portals
Following treatment
Leave medication on skin
Cover with an occlusive dressing
Moist heat pack re-application may assist in further absorption

73. Low-frequency US Phonophoresis
Parameters:
20 kHz output frequency
125 mW/cm2
Pulsed output
Benefits:
Allows medications with a larger size and weight to diffuse
More efficient medication delivery