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87 Cards in this Set

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 Give the formula for propagation speed C= frequency * wavelength Propagation speed is dependent on what? The medium If density increases what happens to the propagation speed? decreases Give the formula for wavelength wavelength= c/ frequency give the units for frequency Hz or MHz Give the units for Period seconds or microseconds Give the units for wavelength meters or millimeters Give the units for propagation speed m/sec or mm/microsecond Give the units for PRF H or kHz Give the units for PRP seconds or microseconds Give the units for Pulse Duration seconds or milliseconds Give the units for Duty Factor Duty factor is unitless! Give the units for SPL millimeters Give the units for Amplitude Megapascals (MPa) Give the units for Power Watts or milliwatts Give the units for Intensity watts/cm^2 Give the units for the Beam Uniformity Ratio (BUR) BUR is unitless! Give the units for Attenuation Decibels Give the units for the attenuation coefficient dB/cm Give the units for Impedence Rayls Give the formula for SPL SPL= n * wavelength OR SPL= (n*c)/frequency Give the formula for Pulse Duration PD= n * T Give the formula for Duty Factor DF= (PD/PRP) * 1000 OR DF= (PD*PRF)/1000 Give the formula for Intensity Intensity= Power/Area Describe the Temporal average intensity to the Peak average intensity Intensity TA = Intensity PA * DF Give the formula for Beam Uniformity Ratio BUR= SP/ SA Give the formula for Attenuation coefficient Ac= 1/2 frequency Give the formula for Attenuation Attenuation= Ac * Length OR Attenuation= 1/2frequency * length Give the formula for the Half Value Thickness Layer HVTL = 3/ Ac OR HVTL = 6/ frequency Give the formula for Impedence Z= density * c Give the formula for the Intensity Reflected Coefficient IRC= [(Z2-Z1)/(Z2+Z1)]^2 Give the formula for the Intensity Transmitted Coefficient ITC= 1- IRC Give the formula for Snell's Law [sine incident angle/ sine transmitted angle]= c1/c2 Give the formula to solve for the distance of the reflector D= 1/2 [c * time] t represents round trip time The average round trip distance of a reflector can be solved using which rule? 13microseconds/1cm Rule aka the rule of 13 Define frequency number of cycles per second Define period time it takes for one cycle to occur Define wavelength The length of one complete cycle Define PRF the number of pulses per second Define PRP Time from the begin of one pulse to the beginning of the next pulse Define PD time it takes for one pulse to occur Define Duty Factor Fraction of time the transducer is generating a pulse (when it's on) Define SPL Length of a pulse Define Amplitude Variation of a given sound wave, indicates strength Define Power Rate at which energy is transferred Define Intensity Rate at which energy passes through an area Define the Beam Uniformity Ratio unitless ratio that describes the distribution of the sound beam intensity Define Attenuation weakening of a sound beam Define the Half Value Thickness Layer distance intensity must travel to be reduced by half the original intensity Define Backscatter sound travels back in the direction it came from How many pulses are in a pulsed wave cycle? 2-3 How many pulses are in a Doppler wave cycle 5- 30 Describe the relationship between power, intensity, and amplitude Power is congruent to Intensity Power is congruent to Amp^2 Intensity is congruent to Amp^2 Describe the purpose of Focusing a beam Decreases the area of the sound beam therefore increases the intensity Where is the Spatial Peak intensity found At the beam center What is the most common intensity used in pulsed wave? SPTA Where is SPTP used? In continuous wave, is the highest intensity What is the purpose of a hydrophone? measures the intensity of a sound beam When does a specular reflection occur? When the wavelength is larger than the boundary and the surface is smooth What kind of boundary does perpendicular incidence encounter? A 90 degree angle What kind of boundary does an oblique incidence encounter? Any angle other than 90 degrees Give the 3 criteria for Snell's Law 1. need 2 different c 2. need to hit at oblique angles 3. incident angle = reflected angle Give the 2 requirements for Refraction to occur 1. oblique incidence 2. different propagation speeds on each side of the boundary Refraction is strongly dependent on? Impedence What will cause scattering? 1. size of reflector is equal or less than the wavelength 2. a rough surface List the contrast agents used in the U.S 1. Definity 2. Imagent 3. Optison What are the purposes of contrast agents 1. improve lesion detection 2. improves weakened Doppler signals List the acoustic variables 1. Pressure 2. Density 3. Particle vibration Give the formula for NZL NZL= (apeature)^2/(4*wavelength) OR NZL= (aperature)^2*freq/4*c Give the formula for Q Factor Q= operating freq./ Bandwidth What is the purpose of damping material? used to reduce number of cycles in a pulse to improve resolution What is sacrificed with damping material sensitivity What is the damping material composed of? epoxy resin and metal powders What is another name for damping material? Backing material How thick are ultrasound elements typically? 0.2-1mm Describe the relationship between crystal thickness and frequency The thicker the crystal the lower the frequency The thinner the crystal the higher the frequency Describe the matching layer in relation to the crystal wavelength matching layer = 1/4 wavelength of the crystal What determines the Near Zone Length? aperature and operating frequency What is another name for near zone? Fresnel zone Describe the relationship between NZL, aperature, and frequency Increase aperature, increase NZL Increase frequency, increase NZL What is another name for the far zone? Fraunhofer zone Describe the width of the transducer element at the end of the NZL and at double the NZL End of NZL beam width= 1/2 transducer element width Double NZL beam width = transducer element width Focusing can only be accomplished in what zone? Fresnel zone aka near zone Annular array transducers are __ steered and __ focused mechanically steered, electronically focused Define aperature Size of the ultrasound element Define apodization outer elements are driven at lower amplitudes than inner elements to reduce grating lobes Define matching layer Placed in front of transducer to reduce reflection at the transducer/element interface