Ultrasound 10cm 2 Ultrasound (US) Therapeutic ultrasound Uses acoustic energy, delivered at high frequencies for therapeutic purposes Electrical current creates a mechanical vibration in a crystalline material housed in a head of the unit Vibration of this material produces acoustic energy Energy emitted from the head travels through tissues and is absorbed Sound energy used for diagnostic imaging differs in amplitude and pulse characteristics Ultrasound (US) Crystal quality and size: BNR and ERA Effective radiating area (ERA)the area that receives at least 5% of the peak sound energy Beam nonuniformity ratio (BNR)ratio between peak amplitude and the average amplitude of the ultrasound beam across the ERA The lower the BNR, the more uniform the intensity of the sound wave Lower BNR minimizes the risk of hot spots and allows for higher doses to be applied Acceptable BNR range is between 2 and 6 (must be listed on all units) Ultrasound (US) Conducting media Substances used to conduct US US gel and gel padseffective conductors Mineral oilpoor Lotionspoor Watermay attenuate as much as 66% of sound waves; not very good Ultrasound (US) Parameters of treatment with US Amplitudeclinician controlled Sound energy emitted by crystal measured in watts (W) Dose of sound energy delivered is based on amount of energy being emitted divided by the radiating area of the crystal, which is measured in square centimeters US dose is measured in W/cm2 Duty cycle Ratio of on time to off time (pulsed) No interruption: 100% duty cycle or continuous US Ultrasound (US) Duration of treatment Frequency Affects the depth at which greatest amount of US energy is absorbed Typically either 1 MHz (deeper) or 3 MHz (superficial) Most older units have a single fixed frequency of 1 MHz, but those offering more than one are now common Ultrasound (US) Sound energy absorption in tissues Tissues with greater protein density have a higher rate of US absorption Tendon, ligament, and muscle tissue Superficial bones and nerves absorb the most energy Tissues with higher water content have a lower absorption rate (skin and adipose tissue) US at a higher frequency (3 MHz) is absorbed more rapidly than at a lower frequency (1 MHz) Ultrasound (US) Thermal effects of US Potential to increase local blood flow Increases in collagen elasticity Analgesic and antispasmotic responses not as great as those following cryotherapy, superficial heating, and TENS Ultrasound (US) Tissue heating and cool-down Duty cycle Continuous US results in therapeutically beneficial amounts of tissue heating Total energy delivered during pulsed US is less at the same intensity and duration Dose The greater the dose of sound energy, the greater the amount of energy delivered to the tissues With continuous US, higher dose results in greater tissue heating in less time Treatment time Interaction among frequency, dose, and time required to increase tissue temperature Longer applications needed when lower intensities of US are used Ultrasound (US) Treatment area When larger areas are treated, the amount of acoustic energy reaching any single area is decreased Best recommendation suggests treatment area of two to three times the ERA Sound head movement Moving sound head slowly prevents hot spots and helps to maintain good surface contact Rapid, sloppy movement of the sound head with infrequent surface contact decreases thermal response Thermal response to US is short-lived Superficial tissues cool more rapidly Stretching or manual therapies should be performed immediately for benefits of US to be realized Interferential Is used to Reducing pain Uses 4 electrodes to deliver 2 currents, one current w/ a constant frequency and the other current w/ a variable frequency Frequency of over 4000 Hz = comfortable & able to pass through the skin surface Where they cross is called the beat General accepted range is 80 to 150 Hz, w/ low 0 to 10Hz Low range is to increase local blood circulation High range for pain relief Premodulated (Bi-Polar) Therapy Reduces pain and increases R.O.M. Used for treating small areas where 4 electrodes cannot be placed Uses one output jack w/ a waveform identical to interferential current while only using 2 electrodes Russian Stimulation The output of this is a 2,500 Hz sinusoidal wave. Russian stimulation currents produce strong muscle contractions. Allows the user to choose muscle contraction/relaxation cycle from a preset option of 10/10, 10/20, 10/30, 10/40 & 10/50 or user-defined or continuous Russian Stimulation Ultrasound 2cm 2