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Therapeutic Ultrasound Chapter 7. © 2005 – FA Davis Description Acoustical energy (sound waves) above the range of human hearing Acoustical energy (sound.

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Presentation on theme: "Therapeutic Ultrasound Chapter 7. © 2005 – FA Davis Description Acoustical energy (sound waves) above the range of human hearing Acoustical energy (sound."— Presentation transcript:

1 Therapeutic Ultrasound Chapter 7

2 © 2005 – FA Davis Description Acoustical energy (sound waves) above the range of human hearing Acoustical energy (sound waves) above the range of human hearing –Therapeutic range: 0.75 to 3.3 MHz Effects: Effects: –Thermal –Nonthermal (mechanical)

3 © 2005 – FA Davis Uses Calcific bursitis Calcific bursitis Inflammatory conditions Inflammatory conditions Joint contractures Joint contractures Pain Pain Muscle spasm Muscle spasm Acute orthopedic injuries (low pulses, low intensity) Acute orthopedic injuries (low pulses, low intensity)

4 © 2005 – FA Davis Production of Ultrasound An alternating current is passed through a crystal An alternating current is passed through a crystal The current causes the crystal to vibrate The current causes the crystal to vibrate –Electropiezo effect Vibrating crystal produce high-frequency sound waves Vibrating crystal produce high-frequency sound waves

5 © 2005 – FA Davis Effective Radiating Area (ERA) Area of the crystal that actually produces sound waves 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 ERA is always smaller than the transducer face Energy is concentrated near the center Energy is concentrated near the center ERA

6 © 2005 – FA Davis Beam Profile Multiple waves emerge from the head Multiple waves emerge from the head Energy diverges as it moves away from the source Energy diverges as it moves away from the source Energy is uniform close to the head Energy is uniform close to the head –Near zone (Fresnel zone) Becomes less consistent farther away from the head Becomes less consistent farther away from the head –Spatial peak intensity Spatial Peak Intensity

7 © 2005 – FA Davis Beam Nonuniformity Ratio (BNR) Describes the amount of variation in the beam Describes the amount of variation in the beam Ratio between: Ratio between: –Spatial peak intensity (SPI) –Average intensity (SAI - metered output) –BNR = SPI/SAI Perfect beam would have a BNR of 1:1 Perfect beam would have a BNR of 1:1 Minimally acceptable BNR is 8:1 Minimally acceptable BNR is 8:1 The actual peak output is equal to the SAI * the BNR The actual peak output is equal to the SAI * the BNR –10 W total output * 6:1 BNR –60 watt SPI Spatial Peak Intensity Spatial Average Intensity (Displayed on the unit)

8 © 2005 – FA Davis Modes of Application Continuous Ultrasonic energy is constantly produced Ultrasonic energy is constantly produced Can produce thermal effects based on: Can produce thermal effects based on: –Output intensity –Treatment duration Pulsed Ultrasonic output is regularly interrupted Ultrasonic output is regularly interrupted Produces nonthermal effects Produces nonthermal effects

9 © 2005 – FA Davis Pulsed Output Ultrasonic output is cycled On and Off Ultrasonic output is cycled On and Off –On = Pulse length –Off = Pulse interval Expressed as a Duty Cycle 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 © 2005 – FA Davis Output Frequency Measured in megahertz (MHz) Measured in megahertz (MHz) –1 MHz = 1,000,000 waves per second Determines the depth of effects Determines the depth of effects 1 MHz Output 1 MHz Output –Penetrates 5 to 7 cm –Thermal effects last longer –More divergent beam 3 MHz Output 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 © 2005 – FA Davis Spatial Average Intensity (SAI) Describes the energy per unit of area Describes the energy per unit of area Total output (watts)/area Total output (watts)/area –Watts/effective radiating area (cm 2 ) –W/cm 2 15 watts being applied with a 10 cm 2 ERA 15 watts being applied with a 10 cm 2 ERA –15 Watts / 10 cm 2 –1.5 W/cm 2

13 © 2005 – FA Davis Power Measures – Pulsed Output Spatial Average Temporal Peak Intensity (SATP) The average energy delivered during the On time of the duty cycle. The average energy delivered during the On time of the duty cycle. Spatial Average Temporal Average Intensity (SATA) Energy delivered over time Energy delivered over time –Spatial Average Intensity * Duty Cycle Meaningful only during pulsed output Meaningful only during pulsed output

14 Biophysical Effects Thermal

15 © 2005 – FA Davis Thermal Effects Increased sensory nerve conduction velocity Increased sensory nerve conduction velocity Increased motor nerve conduction velocity Increased motor nerve conduction velocity Increased extensibility of collagen-rich Increased extensibility of collagen-rich Increased vascular permeability structures Increased vascular permeability structures Increased collagen deposition Increased collagen deposition Increased blood flow Increased blood flow Reduction of muscle spasm Reduction of muscle spasm Increased macrophage activity Increased macrophage activity Enhanced adhesion of leukocytes to damaged endothelial cells Enhanced adhesion of leukocytes to damaged endothelial cells

16 © 2005 – FA Davis Heating Classifications IncreaseUsed For Mild1°CMild inflammation Accelerate metabolism Moderate2° – 3°CDecreasing muscle spasm Decreasing pain Increasing blood flow Chronic inflammation Vigorous3° – 4°CTissue elongation Scar tissue reduction

17 © 2005 – FA Davis Heating Rate Heating rate and magnitude is based on: Heating rate and magnitude is based on: –Duty cycle –Output frequency –Intensity –Target tissues –Size of the treatment area

18 © 2005 – FA Davis Thermal Effects Same as other heat modalities Same as other heat modalities –Smaller volume of tissue –Shorter duration of effects Preheat the skin with a moist heat pack Preheat the skin with a moist heat pack –Decreases the time to reach vigorous heating Poorly vascularized, collagen-rich tissues are preferentially heated Poorly vascularized, collagen-rich tissues are preferentially heated –Fascia, tendon, scar tissue Tissues containing an increased proportion of fluid do not heat as well Tissues containing an increased proportion of fluid do not heat as well –Adipose tissue, articular fluid

19 Biophysical Effects Nonthermal

20 © 2005 – FA Davis Nonthermal Effects Increased cell membrane permeability Increased cell membrane permeability Altered rates of diffusion across the cell membrane Altered rates of diffusion across the cell membrane Increased vascular permeability Increased vascular permeability Secretion of cytokines Secretion of cytokines Increased blood flow Increased blood flow Increased fibroblastic activity Increased fibroblastic activity Stimulation of phagocytosis Stimulation of phagocytosis Granulation tissue production Granulation tissue production Synthesis of protein Synthesis of protein Synthesis of collagen Synthesis of collagen Reduction of edema Reduction of edema Diffusion of ions Diffusion of ions Tissue regeneration Tissue regeneration Formation of stronger deformable connective tissue Formation of stronger deformable connective tissue

21 © 2005 – FA Davis Nonthermal Application Pulsed output Pulsed output –20 to 25% duty cycle –Nonthermal output intensity Continuous output Continuous output –100% duty cycle –Output intensity of less than 0.3 W/cm 2

22 © 2005 – FA Davis Acoustical Streaming Ultrasound causes interstitial fluids to flow Ultrasound causes interstitial fluids to flow Fluids strike cell membranes Fluids strike cell membranes Produce eddy currents Produce eddy currents Eddy currents displace ions and molecules Eddy currents displace ions and molecules Alter: Alter: –Cell membrane permeability –Cellular function

23 Effect on Injury Response

24 © 2005 – FA Davis Cellular Response Acoustical streaming: Acoustical streaming: –Increases cell membrane permeability –Alters cell membrane diffusion rate –Increased histamine release –Mast cell degranulation –Increased rate of protein synthesis Thermal effects: Thermal effects: –Increased cell metabolism –Increased rate of inflammation

25 © 2005 – FA Davis Inflammation May lead to an earlier onset of proliferation May lead to an earlier onset of proliferation –Increased fibroblast proliferation –Release of growth factors and platelets Increased macrophage activity Increased macrophage activity Leukocytes bind to damaged endothelial cells Leukocytes bind to damaged endothelial cells Cell division is increased Cell division is increased

26 © 2005 – FA Davis Inflammation Frequency Specificity 1 MHz Output 1 MHz Output –Release of preformed fibroblasts 3 MHz Output 3 MHz Output –Increased synthesis and secretion of fibroblast precursors Increased in areas of high collagen concentration Increased in areas of high collagen concentration

27 © 2005 – FA Davis Blood and Fluid Dynamics May increase blood flow for 45 minutes May increase blood flow for 45 minutes –Thermal effects –Decreased vascular tone –Histamine release Causes vasodilation Causes vasodilation Moist heat application prior to treatment decreases net increase in blood flow Moist heat application prior to treatment decreases net increase in blood flow

28 © 2005 – FA Davis Pain Control Direct Pain Reduction Increased nerve cell sodium permeability Increased nerve cell sodium permeability Alters nerve function Alters nerve function Increases pain threshold Increases pain threshold Indirect Pain Reduction Increased blood flow Increased blood flow Increased capillary permeability Increased capillary permeability Increased oxygen delivery Increased oxygen delivery Decreased muscle spasm Decreased muscle spasm

29 © 2005 – FA Davis Muscle Spasm Reduced secondary to: Reduced secondary to: –Decreased pain –Altered nerve conduction velocity –Increased temperature (counterirritant effect) –Muscle relaxation

30 © 2005 – FA Davis Tissue Elasticity Ultrasound preferentially heats collagen-rich tissues (tendon, fascia, scar tissue) Ultrasound preferentially heats collagen-rich tissues (tendon, fascia, scar tissue) Temperature must be increased 7.2°F Temperature must be increased 7.2°F Stretching window lasts approximately 3 minutes following the treatment 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 Multiple treatments are required to gain length

31 © 2005 – FA Davis Wound Healing Tendon Healing Continuous US application may: Continuous US application may: –Increase tensile strength –Increase collagen deposition Skin Ulcers 3 MHz, low-intensity pulsed output may assist the healing process 3 MHz, low-intensity pulsed output may assist the healing process Cover the wound with an occlusive dressing Cover the wound with an occlusive dressing

32 © 2005 – FA Davis Fracture Healing Low-intensity pulsed output Low-intensity pulsed output Accelerates rate of fracture healing for: Accelerates rate of fracture healing for: –Acute fractures –Nonunion fractures –Stress fractures Requires specialized unit Requires specialized unit Biophysical Effects: Biophysical Effects: –Mechanical (sound) energy strikes bone –Microvibration of bone triggers growth (osteogenesis) PARAMETERS Frequency1.5 MHz ERA3.88 cm 2 Intensity30 mW/cm 2 Treatment Duration20 minutes Daily

33 © 2005 – FA Davis Contraindications Acute conditions (thermal mode) Acute conditions (thermal mode) Ischemic areas Ischemic areas Areas of impaired circulation Areas of impaired circulation Over areas of deep vein thrombosis Over areas of deep vein thrombosis Anesthetic areas Anesthetic areas Over cancerous tumors Over cancerous tumors Sites of active infection or sepsis Sites of active infection or sepsis Over the spinal cord or large nerve plexus in high doses Over the spinal cord or large nerve plexus in high doses Exposed penetrating metal (eg, external fixation devices) Exposed penetrating metal (eg, external fixation devices) Around the eyes, heart, skull, or genitals Around the eyes, heart, skull, or genitals Over the thorax in the presence of an implanted pacemaker Over the thorax in the presence of an implanted pacemaker Pregnancy when used over the pelvic or lumbar areas Pregnancy when used over the pelvic or lumbar areas Over a fracture site before healing is complete Over a fracture site before healing is complete Stress fracture sites or sites of osteoporosis Stress fracture sites or sites of osteoporosis Over the pelvic or lumbar area in menstruating female patients Over the pelvic or lumbar area in menstruating female patients


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