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Ultrasound 3
- 1. Ultrasound
- 25. Summary of Effects of US Effect Temperature inc Application Non thermal None 37.5 baseline Acute inj, edema, healing Mild thermal 1C Subacute inj, hematoma Mod thermal 2C Chronic itis,pain, TP Vigorous 4C Stretch collagen
- 28. Indications Ultrasound Acute/subacute cond Soft tiss heal/repair Scar tissue Jt.contracture Chr itis Inc collagen extensibility Dec m spasm Pain Inc bl fl Soft tiss repair Inc Pr- syn Tiss regen Bone healing Repair non-union fx Inflamm assoc Myos. Ossificans Plantar warts Myofascial trigger points
- 29. Contraindications Acute/post acute cond.(Thermal) Areas of decreased temp sensation Areas dec circ Vasc. Insuff Thrombophleb Eyes Reproductive organs Pelvis immed after menses Pregnancy PPM Malignancy Growing epiphysis TJR Precaution not directly over Infection tumors
Notas del editor
- Think of how a stone can skip through the water creating waves or ripples. Or think of a boat with an outboard motor. Look at the wake even at slow speeds. Ultrasound is a mechanical wave in which energy is transmitted by the vibrations of the molecules of the biologic medium through which the wave is traveling.
- Since soft tissues are mostly like liquids, therefore US travels primarily as a longitudinal wave, except when in contact with bone, a transverse wave results.
- US has a frequency of >20KHz
- In our bodies structures naturally have different densities. For example the US will travel at 1540 m/s through soft tissue. Through bone it travels at 4000m/s
- Tissues with high fluid content such as blood plasma US penetrates. Tissues with high protein contents such as skeletal m, peripheral n the US will have its greatest absorption and greatest heating potential
- Sound passing from the transducer to air will be almost completely reflected. Never hold the transducer in the air because it will damage the crystal. The possibility of standing waves is minimized by assuring that you either use pulsed wave US or continually move the sound head.
- High frequency generator that is connected via an oscillator circuit. Transformer is attached via a coaxial cable to a transducer housed in a type of insulated applicator. The oscillator circuit produces a sound beam at a specific frequency. Frequency is reached by the transformation of household current of 60Hz/100v Acto 500v or more by electronic components in the US apparatus. The higher voltage is then applied to oscillators or vibrators that boost the household frequencies to the desired level of 1 or 3 MHz. DEMONSTRATION
- Two types of piezoelectric effects: 1. Direct the generation of an electric voltage across the crystal when it is compressed or expanded. 2. Reverse piezoelectric effect or indirect. This occurs when the AC moves through the crystal producing compression or expansion. This change in voltage polarity causes the crystal to expand and contract and thus vibrate at the frequency of the electrical oscillation. The reverse piezoelectric effect is used to generate US at a desired frequency
- Ideally matches the diameter of the transducer faceplate. The acoustic energy is contained w/I a focused cylindrical beam that is ~ the same diameter as the sound head. This will assure the maintenance of the best coupling. The appropriate size of area to be treated using US is 2-3 x the size of the ERA of the crystal.
- AT 1Mhz US is transmitted through superficial tissues and absorbed primarily at 2-5 cm. 1 Mhz is beneficial for fatter pts., and whenever the desired effects are in deeper tissues. I.e.. Piriformis, Soleus At 3 MHz energy is absorbed in superficial tissues and absorbed with a depth of penetration between 1-2 cm. Ideal for plantar fascitis, patella tendonitis, and epicondylitis. As the frequency of the US increases, the rate of absorption and attenuation increases. 3 MHz frequency US is absorbed more superficially and 3x faster than 1 MHz US. Faster absorption causes faster peak heating. 3Mhz US heats human m 3x faster than 1 MHz
- Collimated means the beam is focused, less divergent and generally produced by a large diameter transducer. As the beam moves away from the transducer the waves eventually become indistinguishable and arrive at a certain point simultaneously. This creates a point of highest acoustic intensity. Maximum Acoustic intensity can e determined by calculating the distance L from the surface of the transducer. L = D2/ 4 W Where D squared is the diameter of the transducer and w is the wavelength.
- Some units are as high as 8 to 1. Peak intensities of 8w/cm2 have been shown to damage tissue. Therefore the pt. runs the risk of tissue damage at intensities > 1w/cm2 are used. Lower BNR’s allow you to lower the chance of developing “Hot Spots” of concentrated energy
- If during a 40 ms time period the US was on for 10ms and off for 30 ms you would say that this is a 25% duty cycle. Formula for Duty Cycle: on time x 100 on time + off time Another example if the pulse duration = 1 ms and the total pulse period is 5 msec. The duty cycle is 20%. Take home message: Continuous US is used most for thermal effects. Pulsed US causes decreased heating. At a low intensity, US pulsed and continuous will produce nonthermal mechanical effects that are desirable for soft tissue healing.
- Spatial averaged intensity: Intensity if the US beam averaged over the area of the transducer Spatial peak intensity: Highest beam value over time range bet 2.5-3.0 w/cm2 Temporal peak- pulsed US, max intensity during on phase w/cm2 Temporal averaged intensity: only pulsed US,average power of both on and off periods Spatial averaged temporal peak- max intensity occurring in time of the spatial averaged intensity. Spatial average during a single pulse. - Regardless of whether the US is pulsed or continuous if the spatial averaged temporal intensity is in the .1 to .2 w/cm2 range the intensity is too w to produce tissue temperature increase and only nonthermal effects will occur
- Some say that tissue temp Increases of 1C increase metabolism and healing, Increases of 2-3 C decrease pain and m spasm, Increases of 4 C or > increase the extensibility of collagen and decrease joint stiffness. Temperatures greater than 45C may damage tissues, pt will experience pain prior to extreme temps
- Acoustic microstreaming may cause high viscous stresses, which may in turn alter cell permeability to Na+ and Ca++ ions– important for the healing process
- Tx area ~ sound head. Larger areas Increase time. The > intensity the less time Frequency determines depth of penetration, and rate of healing. # Mhz is absorbed 3x faster than 1 which means faster healing.
- Coupling agents should not absorb US energy. Medium should be free of air bubbles. Medium shuld act like a lubricant, the transducer should have coupling medium on it before the unit is turned on. If the head is held away from the body part the crystal may be damaged and the transducer may overhead. Water soluble gels are most desirable.
- Move the transducer slowly @ ~4cm/sec cover an area ~ 2-3 x greater than the ERA of the transducer. Overlapping circular motions or longitudinal are acceptable. The higher the BNR the more important it becomes to move the head faster. If the pt c/o pain, decrease the output but increase the duration
- Meds anti inflamm., cortisol, salicates, dexamethosone, analgesics, lidocaine. Thermal effects will increase permeability and the acoustic pressure the us beam creates, will drive the meds in. So the medication will follow the path of the beam. When you do phonophoresis, Us can be pulsed or cont. Potential depth of phonophoresis is > than Ionto