# US Physics

 Which axis on a graph runs horizontally? x-axis Which axis on a graph runs vertically? y-axis Def. two items that are not associated unrelated Def. two items that are associated such that when one item increases, the other increases directly related or directly proportional Def. two items that are associated or affiliated. However, the relationship between the two does not have to be specified related or proportional Def. two items are associated such that when one item increases, the other decreases inversely related or inversely proportional Def. when two numbers with a reciprocal relationship are multiplied together, the result is one. This is a special form of inverse relationship. Reciprocal relationship Name the Powers of Ten for the metric system up to billion and billionth. Include the Exponent, Prefix, Symbol, and Meaning 10^9 giga G billion10^6 mega M million10^ 3 kilo k thousand10^2 hecto h hundred10^1 deca da ten10^-1 deci d tenth10^-2 centi c hundredth10^-3 milli m thousandth10^-6 micro µ millionth10^-9 nano n billionth What units correspond with length? cm, feet, etc. What units correspond with area? cm^2, ft^2, etc. What units correspond with volume? cm^3, ft^3, etc. What type of energy are sound waves? mechanical Pressure is measured in what units? pascals (Pa) Density is measured in units of what? kg/cm^3 Distance is measured in units of what? cm, mm, ft, miles, etc. Name are the 3 accoustic variables. pressure, density, distance What are the 7 accoustic parameters? periodfrequencyamplitudepowerintensitywavelengthpropagation speed Def. particles move in a direction that is perpendicular (at right angles) to the direction that the wave propagates transverse waves Def. particles move in the same direction the the wave propagates longitudinal waves Def. when a pair of waves peak (maximum value) occur at the same time and at the same location. similarly, the troughs (minimum values) occur at the same time in-phase Def. peaks or troughs of two waves occur at different times out-of-phase Def. when two waves combine to form a single wave interference Def. the interference of a pair of in-phase waves results in the formation of a single wave of greater amplitude than either of its components constructive interference Def. the interference of a pair of out-of-phase waves results in the formation of a single wave of lesser amplitude than either of its components destructive interference What type of interference occurs when the frequencies of the waves differ? both constructive and destructive interference will occur What do waves transfer from one location to another? energy Describe sound waves. sound waves are a series of compressions and rarefactions Two waves are traveling in a medium and arrive at a location at the same time. What event takes place? interference Which types of waves will exhibit both constructive and destructive interference? waves of different frequency Def. describe the features of a sound wave. parameters What is the source of a sound wave in US? the ultrasound system and transducer Def. the time it takes a wave to vibrate a single cycle, or the time from the start of a cycle to the start of the next cycle Period Period is reported in units of what? milliseconds What are the typical values for period in ultrasound? .1-.5 µs What determines the period? the sound source only Can the period be adjusted by the sonographer? no Def. the number of particular events that occurs in a specific duration of time frequency What does hertz mean? per second Frequency is reported in what unit? hertz which = 1 cycle/per second What are the typical values for hertz in ultrasound? 2 MHz - 10 MHz Frequency is determined by what? the sound source only Can the sonographer adjust frequency? no What is the audible range of human hearing? 20 Hz to 20,000 Hz Def. sound below 20 Hz which is below the threshold for human hearing infrasound Sound above 20,000 Hz which is above the threshold for human hearing ultrasound Why is frequency important in diagnostic sonography? frequency affects penetration and image quality What is the relationship between period and frequency? inversely related and they are also reciprocals What 3 parameters describe the size, strength, or magnitude of the sound wave? amplitude, power, intensity Def. describes the "bigness" of a wave. it is the difference between the maximum value and the average or undisturbed value of an acoustic variable. (also the difference of the minimum value and average value) amplitude Amplitude can be in units of what? any of the acoustic variables (pressure, density, particle motion) also relatively in decibels What is the typical value in ultrasound for pressure amplitude? 1 MPa to 3 MPa Amplitude is determined by what? initially the sound source but it decreases as the sound propagates which depends on the characteristics of the medium and sound wave Can the sonographer adjust amplitude? yes How is amplitude measured? it's measured from the middle value to the maximum value How is peak-to-peak amplitude measured? the difference between maximum and minimum values of an acoustic variable Def. the rate of energy transfer or the rate at which work is performed describes the "bigness" of the sound wave power Power is measured in what? watts What is the typical value for power in ultrasound? 4 to 90 milliwatts What determines power? initially the sound source but it decreases as the sound propagates which depends on the characteristics of the medium and sound wave Can the sonographer adjust power? yes What is the relationship between power and amplitude? direct relationshippower is proportional to the wave's amplitude squared Def. the concentration of energy in a sound beam. it relates to how the power in a wave spreads or is distributed in space. describes the sounds "bigness" intensity Intensity is measured in units of what? watts/square centimeter What are the typical values for intensity in ultrasound? .01 to 300 W/cm^2 How is intensity determined? initially the sound source but it decreases as the sound propagates which depends on the characteristics of the medium and sound wave Can the sonographer adjust intensity? yes All three "bigness" parameters (amplitude, power, intensity) are ______ related. directly What is relationship between intensity and power? power and intensity are directly proportional What is the relationship between intensity and amplitude? intensity is directly proportional to amplitude squared Def. the distance or length of one complete cycle wavelength Wavelength is measured in units of what? mm, meters, etc. What are typical values for wavelength? .15 to .8 mm What determines wavelength? source and medium Can the sonographer adjust wavelength? no What is the relationship between wavelength and frequency? inversely proportional What is the rule that defines the relationship between frequency and wavelength of sound in soft tissue? To find wavelength of a sound wave in soft tissue, divide 1.54 mm by the frequency in MHz Why is wavelength important in diagnostic ultrasound? shorter wavelengths produce higher quality images with greater detail Def. the distance that a sound wave travels through a medium in 1 second propagation speed Propagation speed is measured in units of what? meters per second, mm/µs, etc. What are the typical values for propagation speed in ultrasound? 500 m/s to 4000 m/s depending on the tissue What determines propagation speed? determined by the medium only Can the sonographer adjust propagation speed? no What is the speed of sound in soft tissue? 1,540 m/s What characteristics of a medium determine the speed of sound in that medium? stiffnessdensity Def. describes the ability of an object to resist compression. stiffness Def. describes the relative weight of a material density How does stiffness affect speed? stiffness and speed are directly related How does density affect speed? density and speed are inversely related Elasticity and compressiblity refer to what type of media? non-stiff What 5 additional parameters describe pulsed sound? pulse durationpulse repetition periodpulse repetition frequencyduty factor spatial pulse length Def. a collection of cycles that travel together with a beginning and move as a single unit pulsed sound What are the two components of pulsed ultrasound? transmit, talking, "on" timereceive, listening, "off" time Def. the actual time from the start of a pulse to the end of that pulse with a fixed duration pulse duration What are typical values for pulse duration? .3 to 2 µs What determines pulse duration? the sound source What are the formulas for pulse duration? pulse duration (µs) = # cycles X period pulse duration (µs) = # cycles / frequency (MHz) What characteristics create pulses with long durations? many cycles in a pulseindividual cycles with long periods What characteristics create pulses with long durations? few cycles in the pulseindividual cycles with short periods Which type of pulse is more desirable in diagnostic imaging, and why? shorter duration pulses because they create images with greater accuracy Def. the distance a pulse occupies in space from the start to the end of a pulse spatial pulse length What are typical values for spatial pulse length? .1 to 1 mm What determines spatial pulse length? sound source and medium What is the formula for spatial pulse length? SPL (mm) = # cycles X wavelength (mm) Spatial pulse length is:  ______ proportional to the number of cycles in the pulse ______ proportional to wavelength ______ proportional to frequency directly directly inversely What are the characteristics of short and long pulses? Long:many cycles in the pulsecycles with longer wavelengths Short fewer cycles in the pulsecycles with shorter wavelengths Which type of pulse is the most desirable in diagnostic imaging? shorter pulses because they create more accurate images Def. the time from the start of one pulse to the start of the next pulse pulse repetition period What units are pulse repetition period reported in? units of time (ms) What are some typical values of pulse repetition period? 100 µs - 1 ms What determines pulse repetition period? sound source specifically imaging depth How are pulse repetition period and depth of view related? directly relatedprp increases depth of view increases What are the two components of pulse repetition period? transmit time receive time What is the other name for transmit time? pulse duration When sonographers adjust the depth what are they actually adjusting? listening time How does listening time change with depth? depth increases listening time increases Def. the number of pulses that an US system transmits into the body each second  Pulse Repetition Frequency PRF units? Hz hertz Typical value of PRF? 1000 - 10,000 hertz PRF determined by? sound sourcespecifically max imaging depth PRF and imaging depth are ____ related. inversely Increasing depth will do what to PRF? lower PRF An US machine is imaging to a depth of 2 cm. How would the PRF be described? high  When the depth is increased to 20 cm, what happens to PRF? PRF is reduced How are PRP and PRF related? inversely and reciprocals  Formula for PRF and PRP PRF X PRP = 1 AuthorQwizdom100 ID107473 Card SetUS Physics DescriptionNotes Updated2012-08-26T17:15:14Z Show Answers