# 555ultrasound1

55 cards

555ultrasound1

Created Feb 27, 2012
by
aftonw

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 Side A Side B 1 ultrasound creates a series of ____ and ____ in the medium which it is applied compressions and refractions 2 what type of energy is US mechanical kinetic energy 3 when was US first used 1938 4 how is ultrasound produces by a piezoelectric crystal inside a metal casing 5 what do the electrodes do to the crystal apply alternating currents 6 ultrasound transducer = sound head 7 piezoelectric phenomenon some solid metals can be electrically charged on their opposite surfaces when they are subjected... 8 reverse piezoelectric phenomenon when a high frequency alternating current is applied to a crystal at rest a mechanical deformation... 9 peizoelectricity crystal at rest + mechanical stress = electric charge 10 reverse piezoelectricity crystal at rest + alteranating high freq currents = mechanical deformation = cycles of expansion... 11 compression (_____) expansion 12 rarefraction (______) contraction 13 what creates waves directed at the tissues compression and rarefraction 14 ultrasound waves (2) 1. compression waves2. rarefraction waves 15 compresion waves are ____ pressure waves high 16 compression waves do what to molecules push them closer together 17 rarefraction waves are ____ pressure waves low 18 rarefraction waves do what to molecules allows them to move farther apart 19 what do compression and rarefaction waves do to particles makes them oscillate about a fixed point 20 US wave properties (4) 1. velocity2. frequency3. wavelength4. amplitude 21 what is the velocity of US in solution, and in air solution = 1500 m/sair = 350 m/s 22 US travels more rapidly in which type of mediums dense 23 the expansions/contractions per second frequency 24 what are the 2 US frequencies 1 MHz, or 3 MHz 25 amplitude aka intensity 26 3 MHz is for what depth 1-2 cm 27 1 MHz is for what depth 4-5 cm 28 what does it mean that 3 MHz is used at 1-2 cm that half the value of Energy at the surface is available at 1-2 cm 29 What is the beam non-uniform ratio (BNR) - waves do not arrive at target at same time- near field - ratio between peak intensity... 30 BNR should be lower than 6 31 BNR = peak intensity / average intensity 32 how do you compensate for the BNR movement of sound head during Tx 33 how do you calculate duty cycle on / (on+off) 34 SATA = intensity (W/cm2) x duty cycle (%) 35 determines the amount of energy delivered by the machine at the surface, but not all of this... SATA 36 decrease in sound energy as the sound wave travels attenuation 37 attenuation is due to (3) 1. refraction2. reflection3. absorbtion 38 amount of impedence by a tissue depends on its ____ and _____ density and elasticity 39 where is the greatest point for impedence steel/air interface of sound head 40 what is the gel for more effective transmission 41 increase ______ content = increase absorption protein 42 best absoprtion tissue (5) 1. tendon 2. ligament3. scar tissue4. fascia5. joint capsule 43 best reflection tissue (2) (high density) 1. bone2. cartilage 44 the greater the difference in _____ the greater the amount of US energy is reflected density 45 what is a standing wave reflected wave interacts with incoming wave 46 what does a standing wave have the potential to create hot spots of high energy or cancel eachother out 47 considered a sationary wave pattern standing wave 48 how are standing waves prevented keep the sound head moving 49 what are 2 cautions for US bony areas, metal implants 50 change in direction of the path of the wave refraction 51 what is refraction a result of changes in velocity from tissue to tissue 52 the greater the change in the _____ of the tissue the greater the change in angle of path density 53 similar densities of tissue = no refraction 54 a scattering of wave as it crosses the interface of 2 different tissues refraction 55 how can you minimize refraction keep sound head perpendicular to surface