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Ultrasound Physics!
| Question | Answer |
|---|---|
| A____________ converts one form of energy into another. | transducer |
| a____________ naterial has the ability to ocnvert electrical energy into sound energy and sound energy into electrical energy. | peizoelectric |
| Clinical imaging ultrasound utilizes ____________ ultrasound to obtain images of structures. | Pulsed Wave |
| Sound energy travesl in a _________. | Medium |
| The acoustic characteristic of a medium is called: | Acoustic impedance |
| A reflection will occur at the coundary of two media if there is an________ ________ mismatch. | Acoustic Impedance |
| The greater the acoustic impedance mismatch, the _________ the amount of reflection. | Greater |
| The greater the acoustic impedance mismatch the greater the amount of reflection with ___________ sound energy transmitted. | Less |
| Soft tissue has an acoustic impedance value of 1.64 rayl x 10-5. Air has an acoustic impedance value of .0004 rayl x 10-5. Predict how much sound energy will be reflected at a soft tissue-air interface. | 99% |
| Approx. how much sound energy will be transmitted at a soft tissue- air interface? | 1% |
| The acoustic impedance value for fat is 1.38 rayl x 10-5. The acoustic impedance value for muscle is 1.70 rayl x 10-5. how much sound energy will be reflected at a fat-muscle interface? | 1% |
| Approx. how much sound energy will be transmitted at a fat-muscle interface? | 99% |
| To ensure the maximum amount of reflected sound energy be returned to the transducer, the best way to strike the boundary of two media is with ___________ incidence. | perpendicular |
| Displaying reflections as spikes is __________- mode. | A (amplitude) |
| _________ mode (displaying reflections as bright dots) is the preferred mode in modern clinical imaging ultrasound. | B |
| A reflection will be placed at the correct depth because the ultrasound machine will utilize the ___________ equation. | range |
| All of the following are excellent techniques to use to improve the image while scanning clinically except: | utilize A-mode |
| All of the following are true statements concerning ultrasound except: | can adjust for changes in the propagation speed of different tissues. |
| Sound waves are longitudinal and: | mechanical |
| A region of high pressure, high density is: | compression |
| A region of low pressure, low density is: | rarefraction |
| Which of the following is considered an acoustic variable? | Pressure |
| The units for pressure include all of the following except: | Kilograms per meter cubed |
| The units for density include which of the following: | kilograms per cubic meter |
| All of the following are true statements concerning sound waves except sound: | travels in avacuum |
| The frequency range for audible sound is: | 20 Hertz to 20,000 Hertz |
| The frequency range for ultrasound is: | greater than 20,000 Hertz |
| Acoustic relates to: | sound |
| All of the following are considered units for period except: | cycles per second |
| The formula used to calculate period is: | 1/F |
| Period ___________ with an increase in frequency. | decrease |
| Period ____________ with a decrease in frequency. | increases |
| The period for a 5 MegaHertz transducer is: | 0.2 us |
| The period for a 10 MHz transducer is: | 0.1us |
| Period is the reciprocal of: | F |
| By altering the iage depth, period: | unchanged |
| Period may be used to calculate: | pulse duration |
| Pulse duration is equal to the number of cycles in a pulse times: | period |
| Pulse duration in part determines: | axial resolution |
| The units for wavelength include all of the following except: | microseconds |
| The wavelength for a 3 MHz probe for soft tissue is: | 0.5mm |
| As frequency increases, wavelength: | decreases |
| As frequency decreases, wavelength: | increases |
| Spatial pulse legth is equal to the number of cycles in a pulse times: | wavelength |
| The spatial pulse length for a 3 cycle pulse for a frequency of 5 MHz in a medium with a propogation speed of 1.54mm/us is: | 0.9mm |
| Spatial pulse length in part determines: | axial resolution |
| Spatial pulse length divided by 2 equals: | axial resolution |
| Decreasing wavelength directly improves: | axial resolution |
| How may the wavelength and spatil pulse length be decrease and axial resolution be improved during an ultrasound scan? | increase frequency |
| The units for propagation speedinclude: | kilometers per second |
| propogation speed is determined by th: | medium |
| the propogation speed of sound in soft tissue is: | 1540 m/s |
| which of the following represents an increasin rate of propogation speed: | air, soft tissue, bone |
| which of the following has an AVERAGE propogation speed of 1.54 mm/us? | soft tissue |
| the propogation speed of ultrasound is directly proportional to the midiums: | stiffness |
| all of the following will effect propogation speed except: | period |
| all of the following are possible units for amplitude except: | watts |
| the initial amplitude of a wave is determined to be 100 pascals. this is a measurement of: | pressure |
| the maximum variation of a wave is 900. the mean variation of the same wave is 600. the minimum variation is 300. the amplitude is: | 300 |
| the sonographer may affect the amplitude of a sound wave by which of the following instrument controls. | transmit gain |
| what effect will increasing the voltage delivered to the transducer from the pulser have on amplitude? | increase |
| as a sound wave propogates through a medium, amplitude: | decreases |
| the sonographer increases the transmit gain. there will be an increase in all of the following except: | propogation speed |
| the units for power include all of the following except: | pascals |
| which of the following ultrasound machine controls affect power? | transmit gain |
| as sound propogates through a medium, power: | decreases |
| increasing frequency will increase all of the following except: | power |
| the units for intensity include: | milliwatts per centimeter squared |
| intensity is area divided into: | power |
| the highest measured intensity value is: | SPTP |
| the lowest measured intensity value is: | SATA |
| the AIUM has stated that there have been no proven biological effects for unfocused transducers for intensities below: | 100 m W/cm2SPTA |
| the AIUM has stated that there have been no proven biological effects for focused transducers for intensities below: | 1,000 m W/cm2 SPTA |
| the sonographer can affect intensity by changing which ultrasound instrument control? | transmit gain |
| as a sound wave passes through a medium, intensity: | decreases |
| increasing intensity by the transmit gain control increases all of the following except: | acoustic velocity |
| all of the following will increase with an increase in transmit gain except: | period |
| another tern for beam unifomity ratio is: | SP/SA factor |
| all of the following are unitless except: | frequency |
| the spatial average for an ultrasound beam is 30. the spatial peak intensity is 60. the beam uniformity ratio is: | 60/30 |
| a sound beam with equal intensities across the beam will have a beam uniformity ratio that is equal to: | 1 |
| untrasound transducer A has a beam uniformity ratio os 5. ultrasound trasnducer B has a beam uniformity ratio of 1. which ultrasound transducer has the brighter center? | transducer A |
| the _________ is a way to express the difference between two values. | decibel |
| decibels are the units for all of the following except: | frequency |
| for soft tissue, which of the following values would best represent a 75% decrease in intensity? | 6 dB |
| for soft tissue, a 90% decrease in intensity is: | 10 dB |
| ____________ allows for the comparison of power, intensity or amplitude of one signal relative to that of another signal. | decibel |
| if the intensity of one sound wave is 1,000 times greater than the intensity of a second sound wave, the ratio of the two intensities can be expressed as ________ decibels. | 30 |
| the amplitude of one sound wave is 1,000 times greater than the amplitude of a second sound wave, the ratio of the two amplitudes can be expressed as _______ decibels. | 60 |
| Mega means | million |
| the term micro means: | one millionth |
| the term kilo means: | thousand |
| the term milli means: | one thousandth |
| five thousand Hertz may be written as 5: | kHz |
| 5 million Hertz may be written as 5: | MHz |
| which of the following is arranged in the proper sequence from lowest to highest? | nano, micro, milli, centi, deci |
| which of the following is arranged in proper sequence form highest to lowest? | Giga, Mega, kilo, hecto |
| the period for a 2 MHz transducer is 0.5: | microseconds (us) |
| the pulse repetition period for a pulse repetition frequency of 2 kHz transducer is 0.5: | milliseconds |
| the circumference of the aorta is measured. the appropriate units would be: | cm |
| pressure is defined as force per unit of: | area |
| a mitral valve area is measured. the appropriate units for this valve area is: | cm2 |
| the appropriate units for density are mass per unit of: | volume |
| which of the following would be the correct way to express cardiac output? | 5 cm3 |
| the duration of blood flow is measured during a doppler wxam. the appropriate units would be: | milliseconds |
| the average speed of soft tissue is | 1,540 m/s |
| all of the following may be used to represent the propogation speed of sound in soft tissue except: | 15,400 cm |
| which of the following has the greatest effect on sound speed? | stiffness |
| what effect will an increase in a mediums elasticity have on the speed of sound? | decrease |
| what effect will an increase in a mediums compressibility have on the speed of sound? | decrease |
| the speed of sound in bone is greater that in air because bone is more: | stiff |
| an increase in the speed of sound will occur if there is an increase in: | bulk modulus |
| the boundary between two media with different acoustic impedances is called acoustic: | interface |
| thesymbold for acoustic impedance is: | Z |
| the units for acoustic impedance are: | m/sx k/gm3 (rayl) |
| acoustic impedance is equal to: | c x p |
| all of the following determine the percentage of reflection except: | frequency |
| how much sound energy will be reflected at a fat-muscle boundary? (assuem perpendicular incidence) | 1% |
| how much sound energy will be transmitted at a fat-muscle interface? (assume perpendicular incidence) | 99% |
| how much sound energy will be reflected at a soft tissue-air interface? (assume perpendicular incidence) | 99% |
| ow much sound energy will be transmitted at a soft tissue-air interface? (assume perpendicular incidence) | 1% |
| all of the following are true statements concerning acoustic impedance except: | less sound energy will be reflected whdn there is a significant acoustic impedance |
| a ___________ reflector is large (compared to the wavelength) and smooth surfaced. | specular |
| all of the following are considered specular relectors except: | red blood cell |
| to maximize reflections from a specular reflector, the sonographer should mainpulate the probe until the ultrasound beam strikes the interface at precisely: | 90 degrees |
| the _______ reflectors are small and/or are rough surfaced. | nonspecular |
| a sound beams wavelength is 0.5mm. which of the following would be an example of a scatter reflector? | 0.4 mm |
| a term used to describe a scatter reflector is: | nonspecular |
| all of the following will increase backscatter except increasing: | smoothness of relfector |
| which of the following is the best prediction of the size of a Rayleigh scatter reflector? | 1/4 wavelength |
| the folowwing are true statements concerning scatter reflectors except: | scatter reflectors boundary dimensions are large compared to specular reflectors |
| all of the following are examples of scatter reflectors except: | diaphragm |
| all of the following are associated with contrast agents except: | specular reflectors |
| the transmission of a fundamental frequency and the reception and processing of a second higher frequency is called: | harmonic imaging |
| a fundamental frequency of 1.6 MHz is transmitted. the second harmonic would be: | 3.2 MHz |
| the two types of harmonic imaging are: | tissue; contrast |
| tissue harmonic imaging improves imaging in all of the following ways except: | increase exam time |
| harmonics without pulse inversion or power modulation will improve all of the following except: | axial resolution |
| which of the following techniques is used to preserve axial resolution with harmonics on? | pulse inversion |
| when a sound beam is perpendicular or square to a specular reflector, it is considered: | normal incidence |
| in clinical ultrasound imaging, maximum reflection amplitude occurs with: | normal incidence |
| for specular reflectors, the brightest returning echoes will occur when there is: | perpendicular incidence |
| sound energy returning to the source is called: | reflection |
| sound energy that travels through a boundary is called: | transmission |
| all of the following may occur with perpendicular incidence except: | refraction |
| determine the intensity reflection coefficient when media A is 6 Mrayls and media B is 6 Mrayls. | 0 |
| at soft tissue interfaces, the percentage of energy reflected is approximately: | less than 1% |
| at soft tissue interfaces, the percentage of energy transmitted is: | 99% |
| at a soft tissue-air interface, the intensity reflection coefficient is equal to: | 0.99 |
| at a soft tissue-air interface, the transmission coefficient is: | 0.1 |
| at a soft tissue-bone interface, the percentage of energy reflected is approxmiately: | 60% |
| at a soft tissue-bone interface, the percentage of sound energy transmitted is approximately: | 40% |
| any incidence other than perpendicular incidence is called: | oblique |
| the incidence angle is 68 degrees. the incidence is: | oblique |
| as a sound wave crosses a boundary it may bend. this is called: | refraction |
| refraction will change: | wavelength |
| a change in the direction of the transmitted sound at a specular interface is called: | refraction |
| snells law governs: | refraction |
| the propogation speed in medium on eis 1,510 m/s. the propogation speed in medium two is 1,630 m/s. the incidence angle is 33 degrees. the reflected angle will be: | equal to 33 degrees |
| the propogation speed in medium two is 1,535 m/s. the propogation speed in medium one is 1,580 m/s. the incidence angle is 60 degrees. the transmission angle will be: | less than the incident angle |
| the propogation speed in medium one is 1,540 m/s. the propogation speed in medium two is 1,600 m/s. there is oblique incidence. the transmission angle will be: | greater than the incidence angle |
| the propogation speed in medium one is 1,540 m/s. the propogation speed in medium two is 1,530 m/s. the incidence angle is 60 degrees. the transmission angle will be: | 60 degrees |
| thereis normal incidence. the acoustic impedance in medium one is 1.3 Megarayls. the acoustic impedance of medium two is 1.3 megarayls. there will be no: | refraction, reflection |
| the loss of sounds amplitude and intensity is called: | attenuation |
| all of teh following are causes of attenuation in soft tissue except: | transmission |
| the conversion of sound energy into heat is called: | absorption |
| the portion of sound energy returned to the sound source is called: | reflection |
| the diffusion or redirection of sound energy in multiple directions is called: | scatter |
| the principle cause of attenuation in soft tissue is: | absorption |
| the amount of attenuation which occurs per cintimeter is called: | attenuation coefficient |
| the units for attenuation coefficient are: | dB/cm |
| the attenuation coefficient for soft tissue is approximately: | 0.5 dB/cm/MHz |
| determine the attenuation coefficient for a 2 MHz transducer assuming soft tissue. | 1.0 dB/cm |
| determine the atttenuation coefficient for a 5 MHz transducer assuming soft tissue. | 2.5 dB/cm |
| determine the attenuation coefficient for a 10 MHz transducer assuming soft tissue. | 5 dB/cm |
| as frequency increases, the attenuation coefficient: | increases |
| the attenuation coefficient is dependent upon the: | frequency |
| the attenuation coefficeint will increase if there is an increase in: | frequency |
| the total attenuation for a 2 MHz transducer at 3 cm in soft tissue is: | 3 dB |
| the total attenuation for a 4 MHz transducer at 3 cm in soft tissue is: | 6 dB |
| the total attenuation for a 10 MHz in soft tissue at 3 cm is: | 15 dB |
| as frequency increases, toatl attenuation: | increases |
| as image depth increase, total attenuation: | increase |
| total attenuation is directly proportional to: | frequency |
| total attenuation is directly proportional to: | image depth |
| the ultrasound instrument control which specifically compensates for attenuation is: | time gain |
| the useful frequency range for clinical imaging is: | 2 MHz to 15 MHz |
| increasing the frequency improves all of the following except: | depth of penetration |
| increasing the frequency decreases all of the following except: | attenuation |
| to improve resolution, the sonographer should increase: | frequency |
| to increase the depth of penetration, the sonographer should decrease: | frequency |
| which of the following transducer frequencies would be best to use for adult cardiac imaging? | 2.5 MHz |
| ________ is th ability to resolve structures in terms of space, time and or strength. | resolution |
| detail resolution is associated with: | lateral resolution, axial resolution |
| spatial resolution is associated with all of the following wxcept: | temporal resolution |
| __________ resolution is the ability to detect two closely spaced structures which lie parallel to the direction of sound travel. | axial |
| axial resolution is directly dependent upon: | spatial pulse length |
| ___________ resolution is the ability to resolve closely spaced structures which lie perpendicular to the sound beam. | lateral |
| lateral reaolution is dierctly dependent upon: | beam width |
| ____________ resolution is the ability to accurately depict moving structures. | temporal |
| temporal resolution is directly dependent upon: | frame rate |
| ____________ resolution is the ability to distinguish between echoes of slightly different intensities. | contrast |
| contrast resolution is dependent upon all of the following except: | postprocessing |
| ____________ resolution refers to the slice thickness in the plane perpendicular to the beam. | elevational |
| which peizoelectric effect does an ultrasound transducer use upon transmission? | reverse piezoelectric |
| which piezoelectric effect does an ultrasound transducer use upon reception? | piezoelectric effect |
| all of the following are natural occuring materials that possess the piezoelectric properly except: | chalk |
| the most common man-made material used today includes all of the following ingredients except: | quartz |
| the process by which man-made materials receive the piezoelectric effect is: | polarization |
| which of the following will neutralize property of ultrasound crystals? | excessive heat |
| the frequency at which the active piezoelectric element oscillates is called the: | fundamental frequency |
| the fundamental frequency of a pulsed wave transducer is determined primarily by the: | element thickness |
| for pulsed wave ultrasound transducers, thin piezoelectric elements produce: | high frequencies |
| the matching layers impedance value is: | between the impedance values of theelement and the skin |
| the matching layers optimal wavelength thickness is: | 1/4 |
| the damping materials impedance value is equal to the: | element |
| the damping material reduces all of the following except: | bandwidth |
| clinical imaging transducers are considered to have a: | wide bandwidth, low Q factor |
| ___________ principle explains why the piezoelectric elements are able to form a sound beam with a near field, natural focus and far field. | Huygen's |
| the frenel zone is the: | near field |
| the near field may be extended by increasing transducer: | diameter |
| which of the following has the greatesteffect on near field length? | transducer diameter |
| a continuous wave unfocused transducer diameter is 12mm. the sound beam width at one neat field length is: | 6mm |
| a continuous wave transducer is 12mm. the sound beam width at two near field lengths is: | 12mm |
| all of the following are true concerning sound beams generated by small aperature transducers except sound beams: | are generally low frequency |
| the far field of an ultrasound beam may be called: | Fraunhofer |
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