# Ultrasound Physics Final.txt

 Name the Metric System from Billion to Billionth 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 is an appropriate unit for area? sqaure yards What is an appropriate unit for volume? cm^3 How many milliliters are in 8 liters? 8000 ml How many centimeters are in 3 meters? 300 cm How many kilometers are in 3000 meters? 3 km What is the reciprocal of 100? 1/100 or 0.01 What is the reciprocal of 1/8? 8 How many hertz is 3 MHz? 3,000,000 hertz How many milliliters are contained in a jar filled with 5 liters of fluid? 5000 ml How many liters are contained in 80 ml of fluid? 0.080 L How many times bigger is a thousand than ten? 100 times How much bigger is a billion than a million? 1000 times How much smaller is a hundred than a thousand? one-tenth Def. biologic tissue media All waves carry _____ from one location to another. energy Sound is a _____ wave in which particles in the medium move. mechanical Def. Area of increased pressure (squeezed together) compressed Def. Area of decreased pressure (stretched apart) rarefied Sound waves travel in _____ lines. straight Sound waves are ______ waves. longitudinal Def. the effects of the medium upon the sound wave acoustic propagation properties Def. the effects of the sound wave upon the biologic tissue through which it passes biologic effects Name the acoustic variables pressure, density, distance What is pressured measured in? Pascals (Pa) Def. concentration of force in an area pressure Def. concentration of mass in a volume density Def. measure of particle motion distance What is density measured in? kg/cm^3 What is distance measured in? ft, cm, mile, etc... What are the acoustic parameters? periodfrequencyamplitudepowerintensitywavelengthpropagation speed Def. particles that move in a direction that is perpendicular to the direction that the wave propagates transverse wave Def. particles that move in the same direction that the wave propagates longitudinal Def. when the peaks or troughs of a pair of waves occur at the same time In-Phase Waves Def. when the peaks or troughs of a pair of waves occur at different times Out-Of-Phase Def. when a pair of waves lose their individual characteristics and combine to form a single wave interference Def. the interference of a pair of in-phase waves constructive interference Def. the interference of a pair of out-of-phase waves destructive interference Waves of with different ______ will undergo constructive and destructive interference. frequencies Two waves are traveling in a medium and arrive at a location at the same time. What event takes place? interference (we don't know if they are in-sync) What is the source of a sound wave? 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 What is period measured in? seconds, ms, hours, etc... What are the typical values for period? .1µs to .5µs Def. the number of particular events that occurs in a specific duration of time frequency What is frequency measured in? Hertz What are the typical values for frequency? 2 MHz to 10 MHz Def. less than 20 Hz infrasound Def. between 20 Hz to 20 kHz audible sound Def. greater than 20 kHz ultrasound What are the relationships between period and frequency? inversely relatedreciprocals What are the bigness parameters? amplitudepower intensity Def. the difference between the maximum or minimum value and the average or undisturbed value of an acoustic variable Amplitude What units can amplitude be measured in? pascalsg/cm^3distancedecibels (dB) What are the typical values of amplitude? 1 MPa to 3 MPa Def. the difference between maximum and minimum values of an acoustic variable peak-to-peak amplitude Def. the rate of energy transfer or the rate at which work is performed power What is power measured in? watts What are the typical values of power? 4 - 90 milliwatts How is power and amplitude related? power is proportional to amplitude squared How is intensity and amplitude related? intensity is proportional to amplitude squared How is intensity and power related? intensity is proportional to power Amplitude has increased by a factor of 3. How much has the power changed? 9-fold Amplitude has decreased by 1/2. How much has power changed? 1/4 Def. the concentration of energy in a sound beam intensity What is intensity measured in? W/cm^2 What are the typical values of intensity? .01 - 300 W/cm^2 What is the formula for intensity? intensity (W/cm^2) = power (w) / area (cm^2) Def. the distance or length of one complete cycle wavelength What is wavelength measured in? meters, inches, cm, etc... What are the typical values of wavelength? .15 - .8 mm What determines wavelength? sound source and medium What is the formula between wavelength and frequency? wavelength (mm) = 1.54 mm/µs / frequency (MHz) What type of wavelength creates better images? shorter wavelength Def. the distance that a sound travels through a medium in 1 second propagation speed What is propagation speed measured in? meters per second, mm/µs What are the typical values of propagation speed? 500 m/s to 4000 m/s What determines the propagation speed? medium What is the speed of sound in soft tissue? 1,540 m/s What is the formula for speed of sound? speed (m/s) = frequency (Hz) x wavelength (m) What two characteristics of a medium effect the speed of sound? stiffness and density Def. describes the ability of an object to resist compression stiffness Def. describes the relative weight of a material density What is the relationship between stiffness and speed? directly related What is the relationship between density and speed? inversely related What terms can describe stiffness? They are opposite of stiff. elasticity and compressiblity What acoustic parameters are determined by the sound source? period, frequency, amplitude, power, intensity, wavelength What acoustic parameters are reciprocals? period and frequency What acoustic parameters can be adjusted by the sonographer? amplitude, power, intensity What acoustic parameter is determined by both the sound source and the medium? wavelength What acoustic parameter is determined by the medium only? propagation speed T/F A wave with a frequency of 15,000 MHz is ultrasonic? true T/F If amplitude is increased to 3 times it's original value, intensity is increased 6-fold. false 9-fold T/F If power is halved intensity is reduced by 1/4. false it's halved T/F propagation speed increases as frequency increases. False Medium 1 has a density of 9 and a stiffness of 6. Medium 2 has a density of 8 and a stiffness of 6. Which medium will be slower? Medium 1 If the power in a beam is 1 watt and the area is 5 cm^2, what is the beam's intensity? .2 W/cm^2 If intensity remains the same while the power is doubled, what has happened to the beam area? doubled A sound beam travels a total of 10 cm in 2 seconds. What is the speed of sound? 5 cm/sec T/F Propagation speed increases as frequency increases. false T/F Propagation speed increases as frequency decreases. False T/F Propagation speed does not change as frequency increases. True What is the wavelength of 3 MHz sound in soft tissue? .51 mm The effects of sound waves on tissue in the body are called ______. bioeffects The effects of tissue on sound waves are called ______. Acoustic propagation properties The effects of a medium on an ultrasound wave are called ________. acoustic propagation properties T/F Continuous wave sound can create diagnostic images. false pulse sound What is pulsed sound? a collection of cycles that travel together 2 components of pulsed sound transmit, talking, "on" timereceive, listening, "off" time Def. the actual time from the start of a pulse to the end of that pulse Pulse duration What is pulse duration measured in? seconds, µs, ms, etc... What are the typical values of pulse duration? .3µs to 2µs What are the formulas for pulse duration? pulse duration (µs) = # of cycles x period (µs)pulse duration (µs) = # of cyles / frequency (MHz) What are the 2 characteristics of long duration pulses? many cycles in the pulse individual cycles with long periods What are the 2 characteristics of short duration pulses? few cycles in the pulse individual cycles with short periods Which type of pulse duration is desirable for imaging? shorter duration pulses improve image accuracy Def. the distance from the start to the end of a pulse Spatial Pulse Length What is spatial pulse length measured in? mm, inches, etc... What are the typical values for spatial pulse length? .1 to 1 mm What is the formula for spatial pulse length? spatial pulse length (mm) = # of cycles x wavelength (mm) What are 2 characteristics of long pulse length? many cycles in the pulse cycles with longer wavelengths What are the 2 characteristics of short pulse length? fewer cycles in the pulse cycles with shorter wavelengths Which type of spatial pulse length is more desirable? shorter pulses create more accurate images Def. the time from the start of one pulse to the start of the next pulse Pulse Repetition Period What is pulse repetition period measured in? units of time, ms What are the typical values for pulse repetition period? 100µs to 1 ms Pulse repetition period is controlled by what? Sound source specifically imaging depth Def. the maximum distance into the body that an ultrasound system is imaging Depth of View What are the 2 components of pulse repetition period? transmit timereceive time What is transmit time also known as? pulse duration What happens to the depth of view when the listening time and pulse repetition period lengthen? deeper imaging What happens to the depth of view when the listening time and pulse repetition period shorten? shallower imaging Def. the number of pulses that an ultrasound system transmits into the body each second Pulse Repetition Frequency What is pulse repetition frequency measured in? hertz What are the typical values of pulse repetition frequency? 1000 to 10000 hertz How is pulse repetition frequency and depth of view related? inversely What are the relationships between pulse repetition frequency and pulse repetition period? inversely related and reciprocals What is the easiest formula to remember PRF and PRP? PRF x PRP = 1 T/F Two waves can have identical pulse repetition frequencies , even if their pulse repetition periods are different. False T/F Two waves can have identical PRFs, even if their periods are different. True T/F PRF and PRP are determined only by the imaging depth. True Def. the percentage or fraction of time that the system is transmitting a pulse Duty Factor What is unit for duty factor? none. it's a percentage therefore dimensionless What are the typical values for Duty Factor? .2% to .5% What is the relationship between depth of view and duty factor? inversely related What is the formula for duty factor? duty factor (%) = (pulse duration / PRP) x 100 What are the factors that determine shallow imaging? less listeningshorter PRPhigher PRFhigher duty factor What are the factors that determine deeper imaging? more listeninglonger PRPlower PRFlower duty factor Def. refers to the intensity of the beam at different locations or distances Spatial Intensity Def. the maximum intensity peak intensity Def. the mathematical middle intensity Average Intensity Def. refers to the intensity at all time, transmit and receive Temporal Intensity Def. refers to the intensity at the transmit time Pulsed intensity Def. the beams intensity at the location where it is maximum spatial peak intensity Def. the beams intensity across the entire cross-sectional area spatial average intensity Def. the beams intensity at the instant in time of its maximum value temporal peak Def. the average intensity during the most intense half-cycle I max Def. the average intensity during the pulse duration pulse average intensity Def. averaging the intensity during the entire PRP (includes both the transmit and recieve times) temporal average intensity T/F Intensities may be reported in various ways with respect to time and space. True The different measurements of intensities are important in the study of ________. bioeffects ______ intensity is the most relevant intensity with respect to tissue heating. SPTA What units are all intensities are measured in? watts/cm^2 What intensity if the highest and which is the lowest? SPTP is the highestSATA is the lowest Def. describes the spread of a beam in space beam uniformity coefficient or SP/SA factor Def. describes the relationship of beam intensities with time duty factor Continuous wave ultrasound. The pulse average and temporal average intensities are the ______. Same T/F For continuous wave ultrasounds, SPTA = SPPA and SATA = SAPA. True T/F When pulsed and continuous waves have the same SPTP, the continous wave will have the higher intensity. True T/F When pulsed and continuous waves have the same SATP intensities, the continuous wave will have the higher SPTA intensity. True Rank the types of intensities from largest to smallest. SPTP > Im > SPPA > SPTA > SATA Def. the weakening of sound as it travels in the body attenuation Def. strengthening of the ultrasound signal amplifying Def. the unit that quantifies the strength of sound beams as they are created by tranducers and travel through the body Decibels Def. Decibels that are increasing in strength or getting larger. Positive Decibels Def. decibels that are decreasing in strength or getting smaller negative decibels The 3 decibel rule. a change of 3 decibel is equal to doubling or having the intensity of the ultrasound beam The 10 decibel rule. a change of 10 decibels it equal to 10-fold or one-tenth of the intensity of the ultrasound beam A reduction in the intensity of a sound beam to one-half of its original value is _____dB. -3 dB A reduction in the intensity of a sound beam to one-quarter of its original value is ______ dB. -6 dB -10 dB means that the intensity is reduced to ______ of its original value. one-tenth dB is a mathematical representation with a ______ scale. logarithmic and relative T/F We need one intensity to calculate dB. False A wave's intensity is 2mW/cm^2. There is a change of +9 dB. What is the final intensity? 16 mW/cm^2 2 factors determine attenuation path lengthfrequency of sound 3 processes contribute to attenuation reflectionscatteringabsorption Def. when the wave's energy strikes a boundary and is redirected back toward the sound source Reflection 2 types of reflection specular and diffuse Def. type of reflection when sound is reflected back by a smooth boundary and in only one direction Specular reflection Def. type of reflection when sound is reflected back by and irregular surface and radiates in more than one direction Diffuse reflection Def. random redirection of sound in many directions that occurs when the tissue interface is smaller or equal to the wavelength of the sound beam Scattering Def. a special form of scattering that occurs when the structure's dimensions are much smaller than the beam's wavelength and the sound wave is redirected equally in all directions Rayleigh Scattering Def. occurs when ultrasonic energy is converted into another energy form, such as heat absorption Def. the number of decibels of attenuation that occurs when sound travels one cm Attenuation coefficient What is the attenuation coefficient measured in? dB/cm What is the formula for total attenuation? total attenuation (dB) = atten coefficient (dB/cm) x distance (cm) What is the formula for attenuation coefficient in soft tissue? atten. coef. (dB/cm) = frequency (MHz) / 2 Def. the distance that sound travels in a tissue that reduces the intensity of sound to one-half its original value half-value layer thickness What are typical values for half-value layer thickness? .25 - 1 cm What are synomyns for half-value layer? penetration depth, depth of penetration, half-boundary layer 2 factors that determine half-value layer thickness the mediumthe frequency of sound Def. the acoustic resistance to sound traveling in a medium impedance What is the formula for impedance? impedance (rayls) = density (kg/m^3) x prop. speed (m/s) What unit is impedance measured in? rayls What are the typical values for impedance? 1.25 to 1.75 Mrayls What is another name for acoustic impedance? characteristic impedance Authorachimb ID124808 Card SetUltrasound Physics Final.txt Descriptionultrasound physics final Updated2011-12-22T02:06:40Z Show Answers