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SonoPhysics unit 2
chp9-13
| Question | Answer |
|---|---|
| A device that converts one form of energy into another | Transducer |
| Electrical energy from the system is converted into sound | Transmission |
| Reflected sound pulse is converted into electricity | Reception |
| What effect describes the property of certain materials to create a voltage when they are mechanically deformed | piezoelectric effect |
| What is it called when piezoelectric materials change shape when voltage is applied to them? | Reverse piezoelectric effect |
| what is it called when materials which covert sound inot electricity and vice versa | piezoelectric or ferroelectric |
| what piezoelecgtric materials are manmade an?d found in clinical transducers | lead zirconate titanate or pzt |
| What is PZT in an ultrasound transducer also known as | ceramic, active element or crystal |
| Ultrasound transducer transmit what and coverts to what | from electrical and converts to acoustic |
| Ultrasound X receive from what and converts to what | Converts from acoustic to electrical |
| Car engine X converts from what to what | chemical to motion |
| electric motor converts from what to what | electrical to motion |
| lightbulb converts from what to what | electrical to light and heat |
| muscle converts to what to what | chemical to motion |
| Basic ultrasound X has the appearence of what | cylindrical tube |
| The cylindrical tube, constructed out of metal or plastic , that protects the internal components of the X from damage, and also insulates the pt. from electrical shock is known as | the case |
| what is the thin electrical barrier lining the inside of the case, that prevents spurious electrical signals in the air, unrelated to diagnostic info, from entering the X, also helping to prevent electrical noice from contaminating the the clinically impo | the electrical shield |
| What is the thin barrier of cork or rubber that isolates or uncouples the internal components of the X from the case | acoustic insulator |
| what prevents vibrations in the case from dnducing an electrical voltage in the pzt of the X | acoustic insulator |
| what color is the acoustic insulator in most diagrams | red |
| What is the PZT or active element | the crystal itself |
| in a simple probe, the active element is shaped like what | a coin |
| the characteristics of the sound beam emitted by the X are related to what | the dim of the active element |
| the pzt is how thick and what color | 1/2 wavelength thick, and is usually green |
| What provides an electrical connection btw the pzt and the system | the wire |
| how does the wire work | active element requires electrical contact so that during transmission the voltage from the US can cause the crystal to vibrate and produce an ultrasonic wave. |
| how does the crystal produce an image | crystals vibration produces a voltage that must return to the system for processing into an image |
| what is positioned in front of the pzt at the face of the X | the matching layer |
| what does the matching layer do | increase the efficiency of the sound energy transfer btw the active element and the body, and protects the active element |
| how thick is the matching layer and how does it appear | it is 1/4 thick and appears blue |
| what is bonded to the back of the active element? | backing material, also known as damping element |
| what is backing material commonly made of | epoxy resin impregnated with tungsten filaments |
| what happens when an electrical spike excites the PZT? | backing material restricts the extent of the pzt deformation, emitted sound pulse is dampened;making short in duration and length |
| what does crystal dampening enhance | axial res |
| what color does dampening material usually appear as | yellow |
| what is the basic us x appearence | cylindrical tube with sound pulse emitted from the front of the tube, which is placed on the skin and a wire connecting X to the US, extending from the back |
| What does the difference in impedance result from | reflection at boundries |
| do larger reflections occur with smaller or larger impedences | larger |
| how much greater is the impedence of the pzt vs the skin | 20 times greater |
| How does the impedence of the matching layer work | designed to be btw that of the active element and the skin, decreasing reflections at the skin/pzt boundry |
| what is the impedence btw the matching layer and the biologic media | gel, it further increases the travel of sound into and out of the body |
| what is the greatest to least order of impedence | pzt, matching layer, gel, skin |
| what is the backing materials essential role | pulse creation for imaging X |
| what do long pulses do to axial res | degrage them |
| what does damping material or backing material do to pzt crystal's ringing | reduces it, making sound pulse short in length and duration, providing enhanced axial res |
| what are two charecteristics of dampening material | high degree of sound absorption, and acoustic impedance similar to pzt |
| how does the damping element and pzt work | similar, the sound wave created by pzt moves into the damping material and away from teh pt. sound energy is absorbed into the backing material. |
| what are additional consequences to backing material | 1. decreased sensitivity 2. wide bandwidth 3. low quality factor |
| what is decreased sensitivity | means X with this are less likely toconvert low level sound reflections to meaningful elect signals during recpt |
| what else does backing material reduce besides active element vibration during transmisstion | vibration during reception too, making X less responsive |
| What is Resonant Frequency | thwn tone is pure because it vibrates freely for a long time at a single freq |
| what inhibbits the cystal from vibrating freely | backing material, it restricts the pzt |
| By the backing material restricting the pzt, what happens to the pulse emitted by the probe | makes the pulse short in duration sound of a click vs steady tone |
| Does the sound click that results from the backing material restricting the probe above or below the X main freq | both, sound at many different freq |
| what is bandwidth | the range or difference btw the highest and lowest freq in a pulse |
| what is an imaging probe considered or id'd as | with the bandwidth, short pulse, wide bandwidth, and sometimes appears green |
| Is Doppler short pulse and wide bandwidth | No, long pulse, narrow bandwidth |
| does doppler use backing material | no, that's what makes it have long pulses and narrow bandwidth |
| if a X has 3MHZ main freq that ranges 1MHZ to 5MHZ, what is the badwidth or range of freq | 4, 5-1 |
| what is the general rule for long and short duration events | long, narrow bandwidth, short wide bandwidth |
| What is the quality factor unit and what is it related to | unitless and related to bandwidth |
| what is the main freq divided by | q factor being the main freq, is devided by the band width, QF=MF/BW |
| do wide bandwidth probes have high or low QF | low |
| do narrow bandwidth X have high or low QF | high |
| are imaging probes considered to have high or low QF | |
| What does the difference in impedance result from | reflection at boundries |
| do larger reflections occur with smaller or larger impedences | larger |
| how much greater is the impedence of the pzt vs the skin | 20 times greater |
| How does the impedence of the matching layer work | designed to be btw that of the active element and the skin, decreasing reflections at the skin/pzt boundry |
| what is the impedence btw the matching layer and the biologic media | gel, it further increases the travel of sound into and out of the body |
| what is the greatest to least order of impedence | pzt, matching layer, gel, skin |
| what is the backing materials essential role | pulse creation for imaging X |
| what do long pulses do to axial res | degrage them |
| what does damping material or backing material do to pzt crystal's ringing | reduces it, making sound pulse short in length and duration, providing enhanced axial res |
| what are two charecteristics of dampening material | high degree of sound absorption, and acoustic impedance similar to pzt |
| how does the damping element and pzt work | similar, the sound wave created by pzt moves into the damping material and away from teh pt. sound energy is absorbed into the backing material. |
| what are additional consequences to backing material | 1. decreased sensitivity 2. wide bandwidth 3. low quality factor |
| what is decreased sensitivity | means X with this are less likely toconvert low level sound reflections to meaningful elect signals during recpt |
| what else does backing material reduce besides active element vibration during transmisstion | vibration during reception too, making X less responsive |
| What is Resonant Frequency | thwn tone is pure because it vibrates freely for a long time at a single freq |
| what inhibbits the cystal from vibrating freely | backing material, it restricts the pzt |
| By the backing material restricting the pzt, what happens to the pulse emitted by the probe | makes the pulse short in duration sound of a click vs steady tone |
| Does the sound click that results from the backing material restricting the probe above or below the X main freq | both, sound at many different freq |
| what is bandwidth | the range or difference btw the highest and lowest freq in a pulse |
| what is an imaging probe considered or id'd as | with the bandwidth, short pulse, wide bandwidth, and sometimes appears green |
| Is Doppler short pulse and wide bandwidth | No, long pulse, narrow bandwidth |
| does doppler use backing material | no, that's what makes it have long pulses and narrow bandwidth |
| if a X has 3MHZ main freq that ranges 1MHZ to 5MHZ, what is the badwidth or range of freq | 4, 5-1 |
| what is the general rule for long and short duration events | long, narrow bandwidth, short wide bandwidth |
| What is the quality factor unit and what is it related to | unitless and related to bandwidth |
| what is the main freq divided by | q factor being the main freq, is devided by the band width, QF=MF/BW |
| do wide bandwidth probes have high or low QF | low |
| do narrow bandwidth X have high or low QF | high |
| are imaging probes considered to have high or low QF | low because they have backing material and wide bandwidth |
| Does Doppler have high or low QF | High, no backing material and narrow bandwidth |
| if a 3mhz X with a band width of 4mhz, what is the qf | 3/4 or .75 main freq/bandwidth |
| parameters of imaging X | pulse with short duration and length, uses backing material to limit ringing, reduced sensitivity, wide BW, lower QF, improved axial res |
| non imaging X, like doppler | creates CW or pulses with long duration and lenth, no backing mat, inc sensitivity, narrow BW, high QF, does not even make an image |
| shorter pulses have lower or higher q factor | low |
| longer pulses have lower or hight qfactor | high |
| how are pzt created | expose material to a strong elect field at hi substantial temp, called polarization |
| what is polarization | exposing material to a strong electrical field while heating them at high temp |
| what is the temp that the pzt is poloarized | curie temp, or curie point |
| How do you destroy PZT | exposure to high temp, above the curie point |
| what is depolariztion | above the curie point, when the PZT properities are lost |
| Sterilization vs. Disinfection | sterilization is destroying all micro org, with heat, chem, radiation, disinfect chem agent attempts to reduce germs |
| what do you clean a X with | Cidex or other cold germacides |
| pulse length is directly or inversly related to pulse duration | directly |
| qfactor is directly or inversly related to bandwidth | inversley |
| pulse duration is inversley or directly related to bandwidth | inversely |
| CW wave X produces what kind of electrical signal | continuous that excites the active elem |
| is the freq of the cw probe equal to the freq of the electrical signal | yes elect freq = acoustic freq |
| a pw creates what kind of electrical spike | short duration electrical spike, travels thru the wire and strikes the cystals in the X |
| what does the freq of sound created by the active element of a pw depend upon | the charect of the active element in the X |
| what are the two Charect of pw X | speed of the sound in the pzt, and thickness of the pzt |
| what kind of relationship does sound have in pzt with the freq | direct relationship |
| if the sound in pzt is faster, what kind of freq of sound will the be pulsed by the pwX | will be higher |
| what is the range of osund in most pzt materials | 4-6mm/us, 4 times greater than the speed in soft tissue |
| can the speed be adjusted in the pzt | no |
| how does the thickness of the pzt crystal affect the freq | for pw, thinner creates higher freq, so they are inversly related, the thickness and freq |
| thinner active elements create what kind of wavelenths and pulses | higher freq sound pulses, shorter wavelengths |
| what are charact of high freq PW X | thinner pzt crystals, and pzt with higher speeds |
| what are charact of low freq PW X | thicker pzt crystals and pzt with lower speeds. |
| what is the math relationship | freq = sounds speed in pzt mm/us/2xthickness mm |
| what is the shape of the sound beam as it leaves the X | the same as the diam of the X |
| what happens to the shape of the sound beam as it leaves the X and progesses | it will narrow like a funnel until it reaches it's smallest diam, then it will start to expand or diverge |
| what are 5 terms that describe the shape of sound beam | focus, near zone, focal length, far zone, focal zone |
| focus is also called | focal point |
| where is the focus located | where the beam diam is the narrowest, for a round disc shape it's 1/2 the width of the beam as it was when it left X |
| What is the near zone also called | near field, or frenel zone |
| what is the region of the near zone | from the X to the focus, the beam will gradually narrow to the near zone |
| in a disc shaped crystal, the beam leaves the X as the same diam as the active elem, but what happens at the end of the near zone | the beam narrows to only 1/2 of the width of the active elem |
| is the focus located at the begining of the near zone or the end of the near zone | end |
| what else is focal point called | focal depth or near zone length |
| what is the focal length | the distance from the X to the focus |
| Far zone is also called | far field or Fraunhofer zone` |
| where is the far zone | region starting at the focus and extending deeper |
| what happens to the beam within the far zone | diverges or spreads out |
| what is the diam of the beam at the begininning of the far zone | beam is 1/2 as wide as it is at the X |
| what happens to the beam when it's 2 near zone lengths | beam is wider htan the active element |
| focal zone is what region | around the focus where the beam is relatively narrow |
| what kind of images does the focal zone derrive | more accurate images than those form other depths. |
| how much of the focal zone is located in the near field | half |
| how much of the focal zone is located in the far field | half |
| Focal zone can be known as a region where the beam is what an the image is what | narrow and the image detail is superior |
| when the sound beam exits the probe, it goes into what zone, and what is the beam diam | near or fresnal zone where the beam is exact the diam it was as it left the X |
| After the fresnal zone, what zone does the beam enter and what happens to the diam | enters the near zone and gets narrow |
| somewhere in the end of the near zone, what zone does the beam enter and what happens to the diam of the beam | initial port of the focal zone, where the beam cont to get narrow until it's narrowest pnt is reached, the focus |
| What marks the end of the near zone | the focus |
| what's the distance to the X to the focus called | focal length, focal depth, near zone length |
| What marks the begining of the far or fraunhofer zone | when the beam starts to diverge or widen, the beam is still considered to be in the focal zone |
| The focal zone is partially in what two zones | near and far zones |
| does the beams width eventually exceeds that of the X | yes |
| Can you change the location of the focus | yes, on some X |
| what are adjustable focal systems called | phased array |
| 2 charact of a fixed X | transducer diam, freq of the sound |
| What is the relationship between the X diam and the focal depth | directly related |
| will the beam of the larger active element have a deeper or shallow focus | deeper |
| what is the relationship btw freq and focal depth | directly related |
| 2 charact of shallow focus | smaller diam pzt and lower freq |
| 2 charact of deep focus | larger diam pzt and higher freq |
| the equation for focal depth | focal depth(cm)=diam(mm)^2xfreq/6.16 |
| another way equation for focal depth with wavelenth | focal depth,cm= diam,mm^2/40xwavelength,mm |
| what two factors determine the spread of the beam in the far field | 1. trans diam, 2. freq of the sound |
| do smaller diam crystals produce beams that spread out more or less in the deep far zone field | more |
| the relationship btw crystal diam and beam divergence is | inversely related |
| do larger diam crystals improve lateral resolution in the far field? | yes, becuase the diverge less |
| what is the relationship btw freq and beam divergence | inversely related |
| do high freq sound beams improve lateral res in the far field | yes because the diverge less |
| 2 factors of less divergence | larger diam and higher freq |
| 2 factors of more divergence | smaller diam and lower freq` |
| what is the shape of spherical waves | v shape, also known as diffraction patterns, and huygens wavelets. |
| hudgens wavelets are produced by what | hudgens sources |
| what does hudgens principle state | large active elem may be thought of as millions of tiny, distinct sound sources creating a v shape |
| hourglass shape is a result of what | interference of many huygnes sound wavelets emitted, constructive interfearence |
| no soundbeam is a result of what | deconstructive interference |
| huygens principle explains the shape of image X sound beam based upon what | inphase and out of phase wavelets interfering with ea other |
| Resolution refers to what | accuarcy in imaging, msr detail in an image |
| Lateral res id's what type of structures | structures that are perpendicular to the sound beam |
| Axial Res equals what | Longitudinal Res |
| Lateral Res | anything isn the path of the sound beam |
| what is real time known as | temporal |
| elevational is what | the thickness of the beam, sliced thickness |
| Lateral res can distinctly see two structures when they are | side by side or perp to the sound beam, in the sound beam's path |
| what question does lateral res answer | the dist two structures can be apart and sitll produce 2 dist echoes on an ultrasound image |
| what units is lateral res msr in | cm mm any unit of distance |
| what type of numbers are perfered in lateral res | smaller numbers b/c they indicate accuarte images |
| what determines lateral res | the width of the sound beam |
| do narrow beams have better lateral res | yes |
| does lateral res change with depth and if so why | yes because beam diam varies with depth causing lateral res to varie with with depth too |
| what are other names for lateral res | angular, transverse azimuthal res |
| what does LATA stand for | lateral, angular, transverse, azimuthal, all of the names for lateral res |
| when is lateral res the best | at the focus, at the end of the near zone |
| is lateral res good or poor in the focal zone | good |
| what is the math relationship btw lat res | lateral res, mm = beam diam, mm |
| what is better axial or lateral and why | axial, b/c shorter pulses than they are wide, making the numerical for axial less then lateral res |
| how many images will be observed if 2 reflectors are side by side and are closer than the beams width | only one image |
| do higher or lower freq improve axial and lateral res | higher freq |
| why do axial res improve with higher freq | because shorter pulses assoc with hi freq |
| why does lateral res improve in the far field | hi freq pulses diverge less than low freq, making hi freq sound beams narrower than low freq |
| how does focusing improve lateral res | by concentrating the sound energy into a narrower beam |
| what are 3 methods of focusing | 1. external focusing with a lens 2. internal focus, curved active element 3. phased array focus with the electronics of the us system |
| Phased array focusing is reserved for what types of X and is it adjustable | Array X with multiple active elem and very adjustable |
| Lens focusing is | external and fixed, conventional and or mechanical |
| curved active element is | internal, fixed, conventional or mechanical |
| electronicfocus is | phased array, and adjustable |
| can the focal depth and extent of focusing be changed with external and internal focusing methods | no, they are fixed |
| with exeternal focusing, where is the lens placed on the X | infront of the PZT |
| What narrows the beam in the focal zone with external focusing | the arc of the lens will become more prominent, causing the degree of focus to inc, and the beam narrowing in the focal zone |
| how does Curvature of PZT or internal focusing concentrate the sound energy inot a narrower or tighter beam | a curved pzt crystal, the curvature becomes more pronounced, the degree of focus inc, most common form of fixed focusing |
| how is internal focus achieved | with a curved pzt crystal |
| is electronic focusing, or phased array focusing used on single elem X | no only multi element transducers |
| which is more versatile fixed or phased | phased |
| what are 4dist. alterat | |
| Lateral res id's what type of structures | structures that are perpendicular to the sound beam |
| Axial Res equals what | Longitudinal Res |
| Lateral Res | anything isn the path of the sound beam |
| what is real time known as | temporal |
| elevational is what | the thickness of the beam, sliced thickness |
| Lateral res can distinctly see two structures when they are | side by side or perp to the sound beam, in the sound beam's path |
| what question does lateral res answer | the dist two structures can be apart and sitll produce 2 dist echoes on an ultrasound image |
| what units is lateral res msr in | cm mm any unit of distance |
| what type of numbers are perfered in lateral res | smaller numbers b/c they indicate accuarte images |
| what determines lateral res | the width of the sound beam |
| do narrow beams have better lateral res | yes |
| does lateral res change with depth and if so why | yes because beam diam varies with depth causing lateral res to varie with with depth too |
| what are other names for lateral res | angular, transverse azimuthal res |
| what does LATA stand for | lateral, angular, transverse, azimuthal, all of the names for lateral res |
| when is lateral res the best | at the focus, at the end of the near zone |
| is lateral res good or poor in the focal zone | good |
| what is the math relationship btw lat res | lateral res, mm = beam diam, mm |
| what is better axial or lateral and why | axial, b/c shorter pulses than they are wide, making the numerical for axial less then lateral res |
| how many images will be observed if 2 reflectors are side by side and are closer than the beams width | only one image |
| do higher or lower freq improve axial and lateral res | higher freq |
| why do axial res improve with higher freq | because shorter pulses assoc with hi freq |
| why does lateral res improve in the far field | hi freq pulses diverge less than low freq, making hi freq sound beams narrower than low freq |
| how does focusing improve lateral res | by concentrating the sound energy into a narrower beam |
| what are 3 methods of focusing | 1. external focusing with a lens 2. internal focus, curved active element 3. phased array focus with the electronics of the us system |
| Phased array focusing is reserved for what types of X and is it adjustable | Array X with multiple active elem and very adjustable |
| Lens focusing is | external and fixed, conventional and or mechanical |
| curved active element is | internal, fixed, conventional or mechanical |
| electronicfocus is | phased array, and adjustable |
| can the focal depth and extent of focusing be changed with external and internal focusing methods | no, they are fixed |
| with exeternal focusing, where is the lens placed on the X | infront of the PZT |
| What narrows the beam in the focal zone with external focusing | the arc of the lens will become more prominent, causing the degree of focus to inc, and the beam narrowing in the focal zone |
| how does Curvature of PZT or internal focusing concentrate the sound energy inot a narrower or tighter beam | a curved pzt crystal, the curvature becomes more pronounced, the degree of focus inc, most common form of fixed focusing |
| how is internal focus achieved | with a curved pzt crystal |
| is electronic focusing, or phased array focusing used on single elem X | no only multi element transducers |
| which is more versatile fixed or phased | phased |
| what are 4dist. alterations sound beams undergo | 1.beam diam in near field and focal zone narrows,2.focus moved closer to the X, reducing length of near field 3.beam diam beyond focal zone widens 4. size of the focal zone is reduced |
| when the beam in the cocal zone widens it does what to lateral res | focusing will improve later res in the near and focal zones and degrde lateral res beyond the focal zone |
| what determines Freq cw | electrical freq from us |
| what determines pw freq | thickness of the ceramic and speed of sound in ceramic |
| what dtermines focal length | diam of ceramic and freq of sound |
| what determines focal length | diam of ceram and freq of sound |
| what determines beam divergence | diam of ceramic and freq of sound |
| what determines lateral res | beam width |
| what are 4 effects of focusing | 1.beam diam in near and focal zone is reduced 2. focal depth is shallow 3. beam diam in far zone inc 4. focal zone is smaller |
| whast are 3 basic modes of display or formats | 1. amplitude mode 2. brightness mode 3. motion mode |
| Amode appears as a series of what | upward spikes |
| how does a mode work | sound pulse emitted from X, a dot moves at a constant speed across systme's display, reflection returns to the X, it's process and dot is deflicted upwards on the screen |
| The height of the upward deflection is proportional to what in a mode | amplitude of the returning echo |
| strong echos in a mode create what kind of spikes | strong spikes |
| what does the x axis on an amode represent | reflector depth, derived from the time of flight infor of the sound pulse |
| they y axis represents reflection of what | amplitude |
| what are a modes accurate in | determining the depth of reflectors |
| B mode appears as what | dots of varying brightness |
| what happens as a b mode emitts a sound pulse from the X | an invisible dot moves at a constant speed across system display, when reflection returns to the X,it's processed and the invisible dot is turned on |
| what indicates the strength of reflection in the B mode | the brightness of the dot, weaker reflections appear as dark gray dots, strong reflections are whiter bright dots. |
| the x axis of a b mode represents what | reflector depth, derived from time of flight info of the sound pulse |
| amplitude info on a b mode is routed to what axis | z |
| what is the first form of gray scale imaging and is the basis for all other grayscale imaging including real time | b mode |
| M mode appears as a group of what | horizontal wavy lines |
| what does m mode's lines represent on paper | the changes in depth |
| in m mode, a line that moves up and down represents what | moving towards and away from the X |
| a straight line in m mode represents what | stationary reflector |
| the x axis of the m mode represents what | time |
| y axis of the m mode represents what | depth, which is derived from the time of flight info |
| since m mode is arises from a singel penetration into the body, the sampleing rate of m mode is | very high and equal to pulse repetition frequency of the system |
| what is m mode used to detect | cardiac wall motion and it's use is declining |
| Bscan is when the X does what | paints w/ ea scan line, moving the X across the pt, articulator |
| What is C mode | constant depth mode, non depth adjustable, don't use this anymore |
| how many frames/sec is m mode | 1800 frame/sec, rapid moving structures |
| when the beam in the cocal zone widens it does what to lateral res | focusing will improve later res in the near and focal zones and degrde lateral res beyond the focal zone |
| what determines Freq cw | electrical freq from us |
| what determines pw freq | thickness of the ceramic and speed of sound in ceramic |
| what dtermines focal length | diam of ceramic and freq of sound |
| what determines focal length | diam of ceram and freq of sound |
| what determines beam divergence | diam of ceramic and freq of sound |
| what determines lateral res | beam width |
| what are 4 effects of focusing | 1.beam diam in near and focal zone is reduced 2. focal depth is shallow 3. beam diam in far zone inc 4. focal zone is smaller |
| whast are 3 basic modes of display or formats | 1. amplitude mode 2. brightness mode 3. motion mode |
| Amode appears as a series of what | upward spikes |
| how does a mode work | sound pulse emitted from X, a dot moves at a constant speed across systme's display, reflection returns to the X, it's process and dot is deflicted upwards on the screen |
| The height of the upward deflection is proportional to what in a mode | amplitude of the returning echo |
| strong echos in a mode create what kind of spikes | strong spikes |
| what does the x axis on an amode represent | reflector depth, derived from the time of flight infor of the sound pulse |
| they y axis represents reflection of what | amplitude |
| what are a modes accurate in | determining the depth of reflectors |
| B mode appears as what | dots of varying brightness |
| what happens as a b mode emitts a sound pulse from the X | an invisible dot moves at a constant speed across system display, when reflection returns to the X,it's processed and the invisible dot is turned on |
| what indicates the strength of reflection in the B mode | the brightness of the dot, weaker reflections appear as dark gray dots, strong reflections are whiter bright dots. |
| the x axis of a b mode represents what | reflector depth, derived from time of flight info of the sound pulse |
| amplitude info on a b mode is routed to what axis | z |
| what is the first form of gray scale imaging and is the basis for all other grayscale imaging including real time | b mode |
| M mode appears as a group of what | horizontal wavy lines |
| what does m mode's lines represent on paper | the changes in depth |
| in m mode, a line that moves up and down represents what | moving towards and away from the X |
| a straight line in m mode represents what | stationary reflector |
| the x axis of the m mode represents what | time |
| y axis of the m mode represents what | depth, which is derived from the time of flight info |
| since m mode is arises from a singel penetration into the body, the sampleing rate of m mode is | very high and equal to pulse repetition frequency of the system |
| what is m mode used to detect | cardiac wall motion and it's use is declining |
| Bscan is when the X does what | paints w/ ea scan line, moving the X across the pt, articulator |
| What is C mode | constant depth mode, non depth adjustable, don't use this anymore |
| how many frames/sec is m mode | 1800 frame/sec, rapid moving structures |
| Mechanical X contains what type of active elements | single, circular, disc shaped and it's physically moved |
| What is the min number of active elem in a mechanical X | 1 |
| what is the image created by a mechanical X | fan or sector shaped |
| How does the pzt crystal in a mech X work | rotate around a single point with a motor, scan plane is produced by the mech steering |
| do mech X have a fixed focal depth | yes |
| what is the focal depth of the mech X called | conventional, mechanical, or fixed focusing |
| what are the two methods of fixed focusing mechanical X uses | Internal focusing, with the use of a curved active element, or External focus, the use of acoustic lens |
| what planes does focusing happen on with mechanical X | both horizontal and vertical planes because fo the hourglass shape |
| what happens to the mechanical X if one of the crystals are damaged, | entire image is lost, since there is only one crystal |
| Array transducer contain how many active elements | many, moving parts w/in the X, collection of Active elem |
| Elements are what | a slab of pzt cut into a collection of seperate pcs |
| Ea active elem is connected by what in array X | A WIRE TO ITS OWN ELECTRONIC CIRCUITRY IN THE US SYS |
| what is a channel in an array X | combination of active elem, wire and syst electronics |
| how can array X excite single or groups of elements in various ways during trans | b/c ea elem has its own electrical connection |
| with array X, what happens during reception | ea individual crystal produces a small electronic signal that returns to the systems rcvr |
| what are 3 types of array X | linear, annular and convex |
| what are linear X arrangement | active elem are arranged in a straight line |
| annular active element arrangement | elem are arranged as circular rings with common center |
| convex active element arrangement | active element are arranged in a bowed or arched line. X could also be curved r curvilinear array |
| the footprint on a linear array x is how many cm on ea side | one |
| does the linear phase array have any moving parts | no |
| what is phasing | when a beam is steered and focused using an electrical technique |
| how many elements does the ftprint have on a linear phased array x | 100-300 elemen along the face of the probe, placed compactly side by side, the elem is rectangular and narrow |
| what is the width of the elements in a linear phased array x | 1/4 to 1/2 of the sound's wavelength |
| what is the image shape of the phased array X | fan or sector shaped, similar to that of a mechanical X |
| how is the 2d image built up with a phased array X | electronic steering process called phasing |
| how does phasing or electronic steering wk in a phased transducer | sound beams are elect transmitted in different directions w/out the use of moving parts, pulses are directed in a pattern similar to that of the sweeping of a windshiled wiper |
| how is the sound beem steered in a phased array X | electronically without use of moving parts |
| how are the sound beams focused in a phased array X | focused electronically |
| can the focus be altered in a phased array sound beam | yes, the system has controls that allow the sonographer to modify the depth and amt of focusing of the sound beam, which the tech can match teh beams parameters to the clinical circumstances |
| can the sonographer adjust the focal depth of phased array X | yes,can also transmit mult beams down the same scan line ea with different focal depth, providing multi focusing capability |
| what happens if one of the crystals are damaged | will make the x results inconsistant or erratic beam steering and focusing, hard to be determined because ea pulse emitted by many elements in the probe |
| how many crystals are fired in a phased X | all or many are fired to create ea sound beam |
| what type of interference does the phased X create | constructive and destructive to create a single sond pulse with particular characteristics |
| what determines the focus and direction of the sound beam in a phased X | the overall pattern of the electrical signals from the ultrasound system |
| how do electrical spikes form an ultrasound system steer the beam in different directions with a phased array X | 1.ea active elem creates a sm sound wavelet 2. the wavelets combine to form a single sound beam 3.electrical signals are lined up and will arrive at ea of their respective active elem@exactly the same time=soundbeam dir |
| what is the two step approach in determining the beams direction | 1. draw a line connecting the electrical spikes 2. draw another line that is perpindicular to the dotted line extending out from the X |
| how do we know when the sound beam is steered | when the spike line is sloped |
| what is the amt of time the electrical signals aree seperated | ten nanoseconds or ten billionths of a second, which createsa single unified sound beam that is directed downward |
| how does the pattern of phasing work | starts w/an elect spike that excites the upper active elem1st, followed instantly by a 2nd spike that strikes the next pzt cystal and so on |
| how does a slope pattern of phasing work | excites the lowest active element first,and the second happens instantly from bottom to top, the time difference is the same 10 nanosecs, directed upward direction |
| how is beam steering achieved with a phased X | ea electrical pattern creating ea pulse is slightly different than teh pattern be4 it, making it a vector shape |
| the electronics within the ultrasound system that create the sweep patteren is called what | beam former |
| when the spike line is straight in a phased X, what type of sound is produced | an unfocused sound beam is created. |
| how does the pattern of electrical spikes from the beam former focus the sound beam during transmission in a linear phased X | by using a curved pattern creates a focused sound beam, the outer cystals are excited earler than the inner cystals, making the beam straight ahead since there is no predominant slope |
| when is the sound beam focused with a phased X | when the spike line is curved |
| a beam with a more curved electrical pattern will have a deeper or shallower focus | shallower focus, but will be directed straight ahead |
| a phased patteren with an electrical outward or d shape will have what type of beam | a defocused beam, which has no application in diagnostic imaging |
| a beam with an electronic pattern of a slope does what to the sound beam of a phased X | steers the sound beam |
| an electronic pattern thats curvature with a phased X is doing what to the sound beam | focusing the sound beam |
| how does a phased array system create images with multiple foci transmitted | the system must send multiple sound beams down ea scan line |
| what happens when an image is created with three focal points with linear | three distinct sound pulses are transmitted in ea scan line, ea electrical spike will have diff degree of curvature; greatest curve creats the beam with the shallowest foci,least curve has the deeper focus |
| does focus occur during reception too wth linear | yes, during reception when sound arrives at the X, mult elements are xcted along the front of the probe,elements create elect signals that return via mult channels to us rcvr |
| when can the most accurate image be created when the ultrasound rcvr does what with linear | introduce time delays to some of the electrical signals during reception |
| what do optimal time delays used during receive focusing change depend on with linear | depth at which the reflection was created |
| as the transducer listens for reflections, what happens to the delay patterns during receive focusing witb linear phased arrays | they change continuously |
| does the sonographer control dynamic receive focusing with linear phased arrays | no, it's performed automatically by the system |
| how do the annular phased active elements appear | disc like |
| what type of steering does annular phased X use | mechanical steering |
| how is the 2d image built up with annular phased X | physically rotating the ringed element array so taht it transmits sound beams in different directions |
| is electronic steering possible with annular phased X | no |
| what is the primary advantage of annular phased X | multiple transmit focal zones creat ea scan line of the image |
| what does the term phased array mean | either adjustable or multi focus, multi focus is the term that applies to annular array |
| annular phased array means what | focused |
| what type of depths does the annular X collect finformation from | inner crystal of the annular phased array X creates a shallow focus beam and collects info only form the shallowest depths, all other info from the crystal's sound pulse is ignored |
| what part of the annular crystal sound pulse is where info is stored | info from the focal zone, which gets progressively deeper with every ring |
| an annular array compromising 4 ringed elements transmits how many pulses | 4 pulses down ea scan line, ea with a different focal depth, with an image compromised from only the focal zones of ea crystal |
| What is the image shape of an annular X | fan or sector shaped, b/c of the array X being mechanical |
| what happens when an array X has a damaged crystal | a sector of the image is droped, side to side |
| what happens if the inner most ring is lost in the image of an annular X | the most superficial region of the image is lost |
| what happens if the outer most ring is lost in the image of an annular X | a deeper horizontal band of the image is lost |
| which probe has the largest acoustic footprint and creates a rectangular iamge | a linear sequential array X |
| how many pzt does a linear sequential array have | 120 to 250 rectangular shaped strips of pzt arranged side by side in a line, and are much larger than those found in linear phased array |
| how big are the crystals in a linear sequential array | ea crystal is 1 in width, which is large, up to 10cm long |
| the beam steering in a linear sequential array works how | some but not all of the crystals are fired simultaneously to create ea sound beam |
| what is the usual direction of the linear sequential array | parallel to ea other and usually directed straight ahead |
| how does beam focusing work with lenear sequential array | it's achieved electronically, perform both transmit and rcv focusing using electronic time delays |
| how is transmit focusing achieved with linear sequential array | with curvature pattern phased excitation of the active element, where the outer elements are fired first b4 the inner crystals |
| how is recieving focus achieved with linear sequential array | dynamically by introducing electronic delays in the signals returning from the X elements to the US system following echo rcption, altering the rcv focal depth variably |
| what type of focus is commonly used with linear sequential array | electronic focusing |
| what was used in basic linear sequential array X | fixed focusing techniques, such as curved active elements |
| what is the image shape of a linear sequential array X | square, the image is never wider than the X |
| what happens to a linear sequential array X when a pzt is damaged | a section drops out of the image from top to bottom so only the pzt that's damaged are affected |
| Can a linear sequential array steer a sound beam electronically | yes, this creates a parallelogram-shaped image rather than a rectangular image |
| how do beam formers of linear sequential array steer sound beams | by introducing sloped-shaped delays in teh electical xcitation spikes of the elements creating the beam |
| how is a rectangular grayscale anatomic image created during color doppler exams | with a linear array |
| in a doppler exam with linear array, linear seq, does the electrical patterns creating the sound beams have a slope, and what direction is the sound beam directed | no they don't have a slope and they are directed straight down, however the color doppler image is parallelogram shaped, b/c the electrical spike patterns creating the doppler sound beams are sloped |
| how many crystals does a convex array X have and what is the shape, and how are they arranged | there are 120 to 250 rectangular shaped strips of pzt arranged side by side in a bowed line, making the array large |
| how long is the acoustic foot print on a convex footprint | 10 cm, ea crystal is 1 wavelength in width |
| how are the crystals fired in a conves array X | some but not all of the crystals are fired simultaneously to create a single sound beam |
| how do the crystals beam travel from a convex probe | b/c the crystals are arranged in an arc, the pulses travel in different directions as tehy radiate out from the X |
| are the sound beams parallel to ea other from a convex X | no |
| focusing in a modern convex X is acheived how | electronically |
| transmit focusing is achieved how with a convex X | curved spike line pattern, exciting the active elements in the fired group with appropriate delays in a curved spike line pattern |
| with a convex X, how is dynamic rcv focusing achieved | by introducing varying electrical delays in the signals returning from teh X to the us during echo rcptn |
| what is the image shape of a convex X | blunt sector shaped, the image appears to have a bite at the near field of the sector, the curvature corresponds directly to the convex array ftprint |
| what happens to the image of a convex X when a crystal is damaged | a drop out appears in the image from top to bottom |
| vector array is a combo of what technologies | linear sequential and linear phased |
| how is the sound beam steered in a vector array X | sloped electronical delay patterns can be intorduced that steer the sound beams of teh linaear array in a variety of directions |
| how many crystals and what are their shape and arrangement in a vector X | 120-250 reectanfular shaped strips of pzt material arranged side by side in a line |
| is the ftprint of a vector large or small | small, usually only a couple of cm |
| how does the linear technology apply to the vector X | some but not all crystals are fired simultaniously to create a single ssound beam |
| how does the phased array tech apply to the vector X | beam former are delayed in a sloped spike-line patternas they excite a group of elements in a vector, resulting in beams radiating out in dif directions from the face of the X |
| what type of beam focusing is used in vector array X | electronic focusing, both transmit focusing and dynamic rcv focusing improve image quality over a great range of depth |
| what is the image shape of a vector array X | trapezoidal images, at intermediate and deep depths appears like a sector but is flat on top |
| mechanical transducer has what type of effect on images when active element malfunciton | loss of entire image |
| linear and conves arrays transducer has what type of effect on images when active element malfunciton | drop out of image info from top to the bottom of the image, location of the line corresponds to broken crystal |
| phased arrays transducer has what type of effect on images when active element malfunciton | erratic steering and focusing, extent to which the image is affected is variable |
| annular phased arrays transducer has what type of effect on images when active element malfunciton | horizontal or side to side band dropout at a particular depth |
| mechanical transducer's image shape, steering technique and focusing technique | sector, mechanical, fixed |
| linear switched transducer's image shape, steering technique and focusing technique | rectangular, electronic, electronic |
| phased array transducer's image shape, steering technique and focusing technique | sector, electronic, electronic |
| annular phased transducer's image shape, steering technique and focusing technique | sector, mechanical, electronic |
| convex transducer's image shape, steering technique and focusing technique | blunted sector, electronic, electronic |
| vector transducer's image shape, steering technique and focusing technique | trapezoidal, electronic, electronic |
| what is resolution | accuracy in imaging |
| what else applies in addition to axial resolutiona and lateral res | slice thickness or elevational res |
| what does image res actually deals with 3-dim spaces | shallow to deep, side to side and above to below the imagin plane |
| slice thickness is measured in what direction | perpendicular to the imaging plane or above to below the imaging plane |
| a beams measurable thickness varies with what | depth |
| what shape of active elements provide the thinnest ultrasound slices and the best elevational res within a focal zone | disc shaped |
| where are disc shaped crystals found | mechanical and annular phased array |
| with disc shaped crystals, a circle is created when the sound beam is sectioned in what direction | perpindicular to the beam's main axis |
| with disc shaped crystals, what determines the lateral res | lateral res, or beams diam is the width of the circle in one direction |
| with disc shaped crystals, what determines the elevational res | the ht of the circle indicates the beam thickness, or the elevational res. elevational res is identical to teh lateral res with disc shaped crystals |
| is the sliced thickness affected in array probes like phased, linear and convex? | no, with phasing the beam is focused or narrowed only side to side in the imaging plane, which improves lateral res |
| how do you get a thinner slice with array probes such as phased, linear and convex array X | an acoustic lens is placed on the probe making the beam thickness =to active elem, @focal pnt beam is min value,greater depths beam gets substantially greater, thicker than it is wide |
| for the x, what res is the best, and what follows that res | axial is the best followed by lateral and then elevational res |
| what types of newer X create improved slice thickness resolution | 1-1/2 dim arrays, they create thinner beams with improved slice thickness res over greater range of depth |
| how does the new 1-1/2 d array X improve elevational res | by focusing the beam in the thickness plane |
| beams created by single element X are what shape | hourglass shape |
| off axis sound beams are called what | side lobes |
| reflections arising within the side lobes create what | degrade lateral resolution |
| grating lobes are smiliar to what | side lobes |
| grating lobes are created by what transducers | array transducers |
| what effects does grating lobes have on images | degrade lateral res and reuduce image quality |
| side lobes from mechanical scan heads do what to image quality | diminish image quality by degrading lateral res |
| what process can elliminate side and grating lobes | apodization, alters increased strength by firing central crystals with more force lessening side crystal firing |
| grating lobes can be eliminated if teh strength of electrical spikes does what | differ from element to element |
| how do modern X designed to keep the sound beam narrow over substantial depth range | by dynamic aperture, changing the number of crystals along the face of the probe used to tranxmit pulses and rcv reflections, also known as variable aperture or dynamic aperture |
| aperature means what | opening or hole, considered to be known as a listening hole or the number of rcv reflected echoes |
| dynamic aperature improves what resolution | lateral at wide ranges of depths |
| what is static scanning | one frame at a time |
| the ability to create a numerous frames ea sec is considered to be what | frame rate |
| what are the two factors that determine frame rate | sounds speed in the medium and the depth of imaging |
| speed of sound in soft tissue is | considered to be constant at 1.54 km/s |
| what determines the frame rate | the max imaging depth |
| what units msr frame rate | hz |
| temporal resolution is considered to be what | accuracy in time, describes the ability to accuratlyposition moving structures from instant to instant |
| temporal resolution is excellent when | when the system produces many framerates per sec |
| what determines temporal res | framerate |
| units for temporal res | hz |
| what is the relationship btw framerate and time for one frame | inversley related, and are recipricols |
| what are the 2 system controls responsible for setting ultrasound system frame rate | imaging depth, and nubmer of pulses in ea pic |
| how does imaging depth effect temporal res and frame rate | shallow imaging increases frame rate and temp res, they are inversly related |
| shallowing imagin depth short or long go-return time | shorta |
| shallowing imaging has shorter or longer t frame | shorter |
| is the frame rate lower or higher with shallow imaging | higher |
| superior temporal res happens in shallow or deep imaging | shallow |
| what depths create long go-return time | deep |
| what imaging depth creates longer Tframe | deep |
| lower frame rate happens in shallow or deep depths | deep |
| inferior temp res is present in what types of depths | deep imaging |
| Tframe = what | Tframe = #pulsesxprp |
| imaging depth and Tframe rate have what type of relationship | directly related |
| higher frame rates are possible with fewer or more pulses present | fewer pulses |
| pulses per frame and frame rate have what type of relationship | inversely related |
| what 3 factors effect the nubmer of pulses needed to create an image | number of pulses per scan line (multi vs single), sector size and lines per angle of sector(line density) |
| multi focusing does what to frame rate and temp res | decreases framerate and diminshes temp res |
| single focus has how many pulses per scan line | one |
| single focus has what type of Tframe | shorter |
| single focus has what kind of frame rate | higher |
| single focus has what type of temporal res | superior temp res |
| single focus has what type of lateral res | inferior lateral res |
| multi focus has how many pulses per scan line | many |
| multi focus has what length of Tframe | longer |
| multi focus has what level of frame rate | lower |
| multi focus has what type of temp res | inferior temp res |
| multi focu has what type of lateral res | superior lateral res |
| what negative effect does multi focal have | neg effect on temporal res |
| what benifits does multi focal have | improves the accuracy of teh individual images |
| what makes multi focal scan lines superior lateral res | b/c its narrow over a wide range of depths |
| what is the trade off with multi focal | balance btw temporal res and lateral res |
| what happens when the sector size, or field of view is expanded | number of pulses required to make an image increase, but temporal res decreases |
| narrow sector has how many pulses per frame rate | fewer |
| narrow sector has longer or shorter Tframe | shorter |
| narrow sector has whast type of frame rate | higher |
| narrow sector has what type of temp res | superior |
| wide sector has how many pulses per frame rate | more |
| wide sector has longer or shorter Tframe | longer |
| wide sector has what type of frame rate | lower |
| wide sector has what type of temporal lateral res | inferior |
| field of view and frame rate have what type of relationship | inversley |
| what is line density | when the systems can alter the spacing btw sound beams |
| what is the differnce btw low line density and high line density | low line is when lines are spaced far apart, high line density is when lines are packed closely together |
| what happens when there is a high line density | the number of pulses increase and temp res decreases |
| can you change the spacing between the lines | some systems allow you to, others do not |
| what is the plus to having high line density | even though it decreases temp res, it increases accuracy of the individual images |
| what is improved spatial res | with high line density, ea image contains more detail |
| facts about low line density | widely spaced lines, fewer pulses per frame, shorter Tframe, higher frame rate, superior temp res, inferior spatial res |
| facts about high line density | tightly packed lines, more pulses per frame, longer Tframe, lower frame rate, inferior temp res, super spatial res |
| when is temp res better, and how do you obtain better temp res | higher frame rate; shallow imaging, single focus, narrow sector, low line density |
| then is temp res poor and how is this achieved | lower frame rate; deeper image, multi foci points (which improves lateral res), wide sector, high line density (which improves spatial res, good for structures that don't move) |
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