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  1. What can a sonographer use to obtain an accurate measurement of the Achilles tendon?
    Since the Achilles tendon is longer than the transducer face, use EFOV (extended field of view) or panoramic imaging. Achilles tendons with greater thickness measurements are at greater risk for tendinopathy.
  2. To avoid range ambiguity when imaging depth is decreased, what is also decreased: PRF or PRP?
    • Range ambiguity = imaging error. 
    • If PRF is too high while scanning a deep structure in the body.. range ambiguity may occur. 
    • PRF = number of pulses sent into the body every second (Hz).
    • Normal range of PRF = 1,000 - 10,000 Hertz. 
    • Increased imaging depth = PRF decreased to avoid range ambiguity. 
    • PRF inversely related to imaging depth. 
    • If the scan is twice as deep, the US system reduces PRF by 1/2
  3. Describe the 13-microsec rule.
    • If reflector depth is 1cm, time of flight = 13 microsec (μs)
    • Be aware of reflector depth and TOTAL distance traveled. 
    • At 13 μs, depth = 1cm but total distance would be 1cm + 1cm = 2cm
  4. Why does phased array technology use dynamic aperture?
    • If focus is shallow, PZT crystal diameter is small. 
    • Bigger PZT crystal diameter = deeper focus. 
    • Dynamic aperture is used to keep the beam narrow to improve lateral res. for reflectors located at more positions within the US beam. 
    • Dynamic aperture uses fewer crystals to identify echoes from superficial depths (close) and many more crystals to monitor echoes from greater depths (far).
  5. What is a focal zone?
    • It is a more generalized area than the focal point. 
    • Located in the near and far zones of the US beam. 
    • Focal zone is equally divided so half is in the near zone, other half in far zone. 
    • Better resolution here because the diameter of the US wave is fairly narrow in the focal zone. 
    • Focal POINT has the best resolution since beam diameter is tapered the most here.
  6. Which setting can you adjust while demonstrating ALARA (as low as reasonably achievable) in order to make the entire image darker?
    • ALARA is followed in order to reduce the possibility of bioeffects during an US exam. 
    • One way, decrease receiver gain to darken image
    • BEST option: decrease output power (acoustic power) to darken image while lessening patient exposure because the strength of the voltage applied to PZT crystal is weaker.
  7. What is the near field?
    • AKA the Fresnel Zone.
    • located between the transducer and the focus. 
    • The length of the near zone is known as the focal DEPTH, its the region from the transducer to the focus.
  8. When using a linear phased array, what pattern will focus the US wave?
    The beam former will have a curved pattern, when the spikes are in a curved formation.. the beam is focused. When the spikes form a straight line.. the beam is not focused.
  9. Will lateral resolution improve or decline when multiple focus points are used?
    • When sound beams are narrower, lateral res is improved. 
    • Lateral res is improved when multiple focal zones are used, but temporal resolution declines because more time is used to produce the image.
  10. If the focal depth and diameter of the transducer directly or indirectly related?
    • Focal depth = the region extending from the US probe to the focus 
    • PZT crystal = the active element in the transducer. If it has a large diameter, the focal depth will be longer. A transducer with a smaller diameter PZT crystal will have a shorter focal length. 
    • Focal depth and diameter of the active element have a direct relationship.
  11. How is sound able to travel through a vacuum?
    • It can't. Sound waves require a medium to carry the waves.
    • Example: tissue.. it allows the particles to move to help the sound propagate. 
    • Molecules oscillate to create compressions and rarefactions that change the molecule shape. 
    • Acoustic properties = effect of tissue (media) on sound waves
    • Biologic effects = sound beam effects on biologic tissue (media)
  12. The only factor that determines the PRF and PRP is:
    • Only determined by the sound source. 
    • The media has no effect on PRF or PRP. 
    • They are changed when imaging depth is modified. 
    • PRF & PRP are not determined by periods or frequency of the sound wave. 
    • PRF & PRP have an inverse relationship 
    • PRF & imaging depth are inversely related.. when depth increases, PRF decreases. 
    • PRP & scanning depth are directly related.. when depth increases, PRP increases because there is more listening time.
  13. What parameters are increased when the operator increases output power?
    • The brightness of the image is adjusted.
    • When output power is increased, image becomes brighter.
    • Increasing output power forces the pulser component of the US machine to increase the voltage that the PZT crystals receive in the transducers. - This creates stronger pulses sent into tissue, which makes a brighter image because of amplified signals.
    • Output power is also called acoustic power or output gain.
  14. What is adjusted when a sonographer changes the overall gain?
    • The amplification is being increased or decreased.
    • This takes place in the receiver and has a uniform effect on the image.
    • If receiver gain increases, q brighter image appears.
    • If gain decreases, the signal-to-noise ratio is not changed. Increase in power enhances the signal-to-noise.
  15. What effect does imaging depth have on frame rate?
    • FRAME RATE = capability of an US system to produce multiple frames per second.
    • Temporal Res = shows an object in motion, portrayed from one second to the next.. it is decided from the frame rate.
    • The frame rate depends on the imaging depth because a reflector that is deeper in the body will result in a longer time of flight to return to the transducer.
    • Deeper structure = lower frame rate
    • Depth can be controlled by the ultrasound user.
  16. You have a transducer giving off a 10MHz signal and the other giving off a 6MHz signal.. which will be able to focus at a greater depth?
    • 10MHz would be used to create a deeper focal depth.
    • Focal depth is directly related to frequency emanated from the probe.
  17. Two other names for overall GAIN:
    • RECIEVER GAIN and AMPLIFICATION of the sound beam.
    • The control on the US systems produces brighter or darker images.
    • Keep ALARA in mind b/c sonographer can lessen pt exposure if the image needs to be brightened by increasing gain instead of output power.
  18. The point of the sound beam that has been tapered as much as possible is called:
    • Tapered means narrowed in this context. It is called the FOCUS.
    • The width of the US beam is HALF the diameter of the sound beam that exits the probe.
    • The focal point AKA FOCUS, offers the best possible image resolution.
    • The region around the focus is the focal zone.
    • Focal point should be at the level of the anatomical structure of interest.
  19. What can you adjust to make the whole image brighter without adjusting the output power?
    Increase the GAIN. It does not expose the patient to more powerful voltages like the output power does.
  20. When the depth is changed (transmit or listening time), what portion of the PRP is affected?
    • Scanning depth and PRP = direct relationship.
    • If you're scanning something deep in the body, there is more listening time and a lower PRF. 
    • PRP and PRF have an INVERSE relationship.
  21. What is the Fraunhofer Zone?
    • The FAR zone. The area of the sound beam distal (beyond) the focus. 
    • The beam is the narrowest at the focus. 
    • At the focus, the beam is half of the diameter of the transducer. 
    • At the end of the far zone, the beam diverges to the same diameter of the transducer. 
    • The end of the Far Zone = Two Focal Depth
  22. What effects does focusing have on the US beam?
    • Focusing can optimize the lateral resolution. A focused beam moves closer to the face of the probe being used.. resulting in a near zone that is shorter compared to an unfocused beam. 
    • The beam's diameter diverges in the far field.
  23. What type of zoom is considered a postprocessing function because it can be used on a frozen image?
    • MAGNIFICATION. After the image is stored in the scan converter, and is magnified it is called read magnification. 
    • It enlarges the frozen image, spatial resolution stays the same - the zoomed image has the same number of pixels as original. 
    • This has no effect on frame rate (temporal resolution)
  24. What are the fundamental and harmonic frequencies that are created with a 6MHz transducer?
    • Fundamental frequency = 6MHz, it is produced by the transducer and imparted into the patient.
    • Harmonic frequency is 2 times larger than the fundamental frequency. So, 12MHz. 
    • An US beam created with harmonics is less likely to produce images with artifact and undergo LESS distortion.
  25. Can a sonographer change spatial pulse length by changing the scanning depth?
    • Normal value of SPL is 0.1-1mm.
    • SPL depends on sound source and the medium.. it can't be adjusted by sonographer. 
    • Scanning depth has NO EFFECT ON SPL. 
    • Shorter wavelengths = shorter pulses.
  26. How does applying multiple foci influence temporal resolution and frame rate?
    • Multiple foci zones = degrades temporal resolution because it slows down frame rate. 
    • More focal zones means more pulses through each scan line which increases the time to produce every single image. 
    • BUT this improves lateral resolution because the beam is tighter in the focal regions.
  27. Describe the beam diameter at the proximal portion of the far field.
    • Far field = Fraunhofer Zone (beyond the focus)
    • Proximal portion of the far field is the area located closest to the focus. 
    • This region offers the best image detail.
    • The beam is half as wide as the diameter of the transducer & offers the best detail.
  28. Which US (A, B, or M-Mode) offers more information pertaining to the fetal heart with regard to time?
    • M-Mode. 
    • This mode is mostly used in echocardiography to obtain the fetal heart rate. 
    • M-Mode allows greater temporal res.
  29. How is contrast related to dynamic range?
    • Dynamic range = ratio between the largest to smallest intensities that can be displayed by the US system.
    • Units of dynamic range = DECIBLES.
    • Numerous shades of gray on an US (more information) means it has a wide dynamic range. 
    • High contrast image = more black n white, less gray, considered to have narrow dynamic range.
  30. What can you change to optimize contrast resolution so the radiologist can visualize better uterine fibroids.
    • If TV approach, use coded excitation. This allows better penetration when high freq transducers are used so you can see structures in the far field more readily. (Improves image resolution)
    • Also, edge enhancement to delineate differences in gray scale to made edges of fibroid stand out. 
    • OR, use a different grayscale map all together. Resolution contrast will be increased or decreased with different selections.
  31. What is displayed on the X-axis in a B-mode image?
    • The X-axis correlates to the depth of the reflector signal that is being returned to the probe. This is determined by the time of flight. 
    • The 13 microsecond rule applies when the US beam travels in soft tissue. It takes 13us (microseconds) to travel 1cm. 
    • If the time of fight is 26us the depth of the object being imaged is cm.
  32. What information dos M-Mode US present? (amplitude, bandwidth, motion, frequency, time)
    • M-Mode = motion mode. 
    • Data acquired is axial.
    • Information pertaining to time is represented by the X-axis. 
    • Information if the object is moving toward or away from the transducer.
    • Y-axis represents the depth of the objects in the path of the US beam. 
    • Amplitude is reflected, some objects have stronger returning signals than others.
  33. What is the purpose of reject on an US system?
    • Reject is the last process that takes place in the receiver. It's typically offered in two forms: one that takes place automatically and one that can be controlled by the operator. 
    • The reject function enables the user to decide if low level echoes should be displayed in the image. 
    • Stronger signals are not affected by reject. 
    • Reject = suppression = threshold
    • Reject can decrease electronic noise that may be seen while imaging the gallbladder or urinary bladder.
  34. Why does increasing pixel density improve an image?
    • In order to gain an image with greater resolution, a higher pixel density is required. 
    • Pixel density is the number of boxes per inch on the display. 
    • Higher pixel density offers better resolution because there is more pixels in every inch of the image. 
    • Smaller pixels are desired when trying to improve spatial resolution.
    • Lower pixels = larger pixels = not so great spatial resolution = low pixel density image
  35. How can you adjust for echoes that are too bright 4cm from the surface?
    • The scale on the image correlates to how deep the reflectors are located. Every dot represents 1cm. 
    • Counting down 4cm from the top will locate the reflector that is appearing too bright. 
    • To adjust, use the TCG curve with/or the receiver gain (amplification) to provide an image with brightness being the same throughout the image.
  36. What are the regions of a TGC (time gain compensation) curve?
    • TGC has an X and a Y axis. X-axis refers to amount of compensation necessary for depth of object being imaged (Y-axis)
    • Near gain is located superficially near skins surface, there is not much attenuation here so little TGC is needed. 
    • The slope is the middle portion of the TGC where more compensation is necessary b/c greater depths.
    • The knee is located distal of the slope and demonstrates most compensation. 
    • Distal to the knee is the far gain at an even greater depth. This is where the greatest amount of compensation is offered by the machine.
  37. Where is tissue harmonics created?
    • Tissue harmonics are produced when the sound beam interacts with tissues that are deeper in the body in a nonlinear fashion. 
    • Tissue harmonics do not occur when the scanning depth is shallow.
    • Weak sound waves do not produce any tissue harmonics, the waves have to be strong. 
    • Tissue harmonics only emerge from the main axis and will create few imaging errors because of the strength of the beam.
  38. What components of an US transducer are needed to create a grayscale image?
    • Pulser, beam, former, receiver, memory, image display screen.
    • Pulser applies voltages to transducer to excite the active elements in the probe.
    • Beam former controls time delays when phased-array transducer is used. 
    • Receiver collects returning signals being imaged so data  can be viewed on the image display screen. 
    • Memory is where info is kept until it can be displayed on the image display screen.
  39. Compensation is the second process in the receiver.. discuss the functions  that take place in it (the receiver).
    • Compression, reject, amplification, demodulation. 
    • In order: 1. amplification = increases the size of the signals returned. 
    • 2. compensation = adjusts for attenuation that it encounters as it propagates thru the body.
    • 3. compression = helps differentiate between gray shades to determine what information is extracted from the image. 
    • 4. demodulation = can't be adjusted by the system, it has no effect on the image but it rectifies the negative voltages. 
    • 5. reject = final step, it affects only low-level echoes on the display
  40. What component should the sonographer change to demonstrate knowledge of attenuation with depth?
    • Attenuation = reduction of intensity of the US beam as it passes through tissue. 
    • TGC or DGC (depth gain compensation) can be adjusted.
  41. What type of magnification offers improved spatial resolution and is completed before data is stored in the scan converter?
    • WRITE magnification, it takes place before the data is stored in the scan converter. The area in the ROI (region of interest) is rescanned and old data is ignored to obtain new info.
    • This type of zoom increases # of pixels which increases the amount of spatial resolution. 
    • It can't be performed after the image is frozen and is considered a preprocessing technique.
  42. Why is harmonics useful when imaging the gallbladder?
    • The gallbladder is subject to image artifact during an US. 
    • Tissue harmonics eliminates some signals that are not pathological. 
    • Harmonic frequencies allow the songrapher to scan patients at higher frequencies that improve axial resolution and lateral resolution. 
    • Lateral res also improves because the wave is more narrow. 
    • Higher frequency beams produce narrower beam. 
    • Gallbladders imaged with harmonics have a decrease in signal to noise ratio, being able to see organs deeper in the body - also eliminates reverberation artifacts.
  43. What is meant by high contrast?
    • This means pixels are either black or white. Very few shades of gray are visible. 
    • Dynamic range = controls how the intensity of signals is transformed into shades of gray. 
    • If only black and white are created, there is narrow dynamic range. 
    • Many shades of gray = wide dynamic range = low contrast images
    • You can increase dynamic range on the US system, if grainy - increase dynamic range. If too smooth, increase dynamic range
  44. What is the most basic form of grayscale imaging?
    • Brightness mode = B-Mode
    • Pulses are sent into the body and when the signal returns, it appears as a dot on the screen. 
    • High amplitudes will appear as bright-white areas on the screen. 
    • Weaker signal areas will be gray dots.
  45. What units are used to measure compensation?
    • Amplification = refers to the brightness of an US signal. 
    • Amplification = measured in dB
    • Compensation is a type of amplification, so it is measured in dB. 
    • Normal range of amplification = 60 to 100 dB
    • When you change the amp, consider changing the compensation too to get the same brightness throughout. 
    • Compensation = 2nd process after amplification in the receiver used to demonstrate uniform brightness
  46. What is represented by the X-axis and Y-axis while M-Mode is being used?
    • X-axis = time
    • Y-axis = depth of the reflectors
    • Go return time is a way to calculate the depth of a reflector.
    • A higher go return time correlates to the deeper structures, shorter time of flight correlates to shallower structures. 
    • Right to left movement, tracing up = object closer to probe
    • Line moving down = moving away from probe
    • Line horizontal tracing = reflector is not in motion
  47. What control system will modify dynamic range?
    • Dynamic Range = COMPRESSION. 
    • It allows the sonographer to change the number of shades of gray available.
    • Compression has a greater effect on the reflections that are weaker & has a lesser effect on the reflections that are stronger.
  48. With regards to spatial res, should a sonographer choose a 2,000 x 2,000 analog display or a 400 x 400 display?
    • Pixel = the SMALLEST portion of an image in digital format. 
    • Pixel density  # of pixels combined in every inch of the image.
    • If better spatial res is desired, the user must use 2,000 x 2,000 display because of the higher pixel count.
  49. What is a disadvantage of storage that requires chemicals to process film?
    • A darkroom is required.
    • A lot of film is needed. 
    • A processor is needed with the darkroom. 
    • Chemicals must be purchased, stored, and refilled when exhausted. 
    • Artifacts can occur with films.
  50. What is the main disadvantage of persistence?
    • Persistence AKA temporal averaging or temporal compounding.
    • It can be used during grayscale or Doppler imaging. 
    • Image detail improves with temporal compounding, but temporal res is degraded because of additional processing. 
    • Rapid moving structures are difficult because there is a lag as temporal res is decreased. 
    • Persistence is best with structures that demonstrate slow motion.
  51. Which technology acquires data from multiple imaging angles and combines them into one image?
    • Spatial compounding. The frames are generated by the transducer then processed into one image. 
    • Steering is employed from the center of the beam and from the right and left sides of the transducer. 
    • Higher quality of spatial compounding = higher frame rate
    • Spatial compounding degrades temporal res.
    • Spatial compounding helps to reduce speckle and shadowing artifacts in exams like musculoskeletal, thyroid, vascular and breast US
  52. The purpose of DICOM is? (Digital Imaging and Computers in Medicine)
    • Its the link to an US machiene and picture archiving and commuinications system (PACS).
    • DICOM allows for integration between the networks, printing devices, workstations and PACS. 
    • DICOM not recognized by Microsoft Windows, images are extremely large.
    • DICOM browser is necessary so images can be seen on a workstation.
  53. How do you calculate the number of shades of gray in 4 bits?
    • A bit is equal to either 1 or 0 and refers to the smallest unit of info a computer can store. 
    • There are 8 bits in 1 byte. 
    • 2x2x2x2 = 16
    • 4 bits there will be 16 shades of gray. 
    • US images with many shades of gray offer better contrast resolution.
  54. Describe PACS (Picture Archiving and Commnications System)
    • PACS allows users to share and archive images so they can be viewed on a network. 
    • Clinicians and medical personnel can access imaging reports through PACS.
    • PACS has replaced films for facilities that have converted to digital imaging systems. 
    • Over time film studies deteriorate, this won't happen with studies archived with PACS
  55. What will a sonographer expect to see with post stenotic turbulence?
    • When PW Doppler is used, the sonographer can expect to obtain higher flow velocities within the stenosis and even GREATER measurement distal to the stenosis. 
    • It is located after the blood has been narrowed. 
    • Eddy currents will likely be visualized because the blood is no longer moving as smoothly as it was before the stenosis.
  56. What is the purpose of frequency compounding on an US system?
    • Frequency compounding = reduce amount of speckle in an US image.
    • Frequency compounding = averaging method to reduce noise and speckle artifact if present.
  57. What are the applications of 4D US in OB exams?
    • 4D is real time 3D and shows the movements of the fetus. 
    • 4D offers a more realistic portrayal of the fetus. 
    • 4D offers improved echocardiograms, viewing fetal spine, checking for skeletal dysplasia, measuring lung volumes, etc.. they can be studied in greater detail with 4D imaging.
  58. What can be adjusted when a sonographer wants to improve the image sharpness of a mass within the liver?
    • EDGE ENHANCEMENT can be applied. It allows better delineation of the border of structures by sharpening the edges of a mass. 
    • Edge enhancement produces edges that are more reflective to help the mass stand out against normal liver tissue.
  59. How does spatial compounding reduce shadowing and speckle artifact?
    • Spatial compounding requires process to average data obtained from multiple angles of interrogation.
    • Speckle artifact is created when the beam is scattered after interacting with different tissues. 
    • Noise from speckle makes the image grainy. Spatial compounding improves signal-to-noise ratio and suppresses shadowing that's apparent in the image. 
    • A single transducer can steer frames from multiple directions and decrease the amount of shadowing.
  60. What are the disadvantages of PACS (picture archiving and communications system)?
    • The cost and necessary equipment of a PACS system are the disadvantages. 
    • Since it is computerized, it needs  team of tech professionals to manage it. Protocols must be in place in case PACS is not accessible. 
    • User training is required for employees and providers. 
    • Physicians off site must have the system installed on their computers and be grated access to use PACS.
  61. What can the operator do to help the radiologist visualize as much of the aorta as possible?
    • EFOV extended field of view. 
    • Panoramic imaging, it replaces the split screen method by capturing objects longer than the transducer face. 
    • These applications can help visualize the aorta and can provide more information regarding exact location of aneurysms.
  62. Why can persistence be used to improve color Doppler images?
    • Persistence = averaging technique that combines older frames with those of newer data.
    • In grayscale, persistence can smooth out an image or reduce noise. 
    • In color doppler, persistence can identify vessels with slow moving blood, or an obstruction of a vessel. 
    • Temporal resolution is often decreased when persistence is applied to an image.
  63. What control lets the radiologist visualize fibroids by increasing far-field penetration and resolution?
    • CODED EXCITATION can help visualize fibroids. 
    • Higher resolution = uses shorter pulses.. this can increase bioeffects in the patient tho
    • Coded excitation = longer pulses across various frequencies to improve resolution and allow for deeper penetration. 
    • Only necessary for high freq transducers such as ones used for TV studies. 
    • Better penetration and increases res in the far field, fibroids more accurately diagnosed.
  64. What are the disadvantages of using laser discs or compact discs for storage?
    • ADVANTAGES = large storage capacities, won't be erased if next to a magnetic field. 
    • DISADVANTAES = require s browser to view the images on a computer. Must be kept in a safe place so they can be retrieved if necessary.
  65. What is 3D-rendering?
    • A POSTprocessing technique.. you can manage information AFTER it's been stored in the US scan converter. 
    • ex) manipulate the image after the original image is saved.. like adjusting the gain after the image is frozen or magnifying after frozen.
  66. How do you capture brief live clips?
    • CINE LOOP STORAGE. 
    • The can be saved and stored on PACS or CDs so surgeons can see exams in real time. 
    • It can increase confidence in exams requiring compression or Valsalva maneuver, pediatric exams or pyloric stenosis studies & renal exams. 
    • Can be useful if pt can't hold their breath.
  67. What effect does distance have on attenuation?
    • Attenuation is measure in dB. 
    • Attenuation = decrease in amplitude, power and intensity as sound travels through the body. 
    • Distance and frequency influence attenuation.
    • Attenuation and distance = direct relationship 
    • Attenuation and frequency = direct relationship

    • Longer distance = grater attenuation = WEAKER
    • Short distance = less attenuation = STRONGER
    • High freq = greater attenuation 
    • Low fre = less attenuation
  68. How do you optimize the temporal resolution while imaging the gallbladder (other than decreasing the depth) ?
    • High frame rate is ideal during an exam. 
    • Improve (increase) frame rate = decrease field of view (width of the sector).. when the field of view is smaller, fewer pulses needed to create the image, which takes less time. 
    • The frame rate (temporal resolution) is inversely proportional to sector size of the image. 

    For gallbladder, check how many focal zones. Reducing number of focal zone can improve temporal res.
  69. What happens to the duty factor if PRF is increased?
    • Duty factor = percentage of time the transducer is actively transmitting a signal.
    • PRF = number of pulses sent into the body in one second. 
    • Duty factor and PRF both affected by imaging depth and both have direct relationship. 

    • Decreased depth = increased PRF
    • Increased depth = decreased PRF b/c more listening time. 
    • Increased PRF = increased duty factor
  70. What is the relationship between penetration depth and frequency?
    • Greater depth = greater distance = greater attenuation
    • More attenuation = decrease in intensity of the sound beam. 
    • More attenuation = higher frequency
    • Attenuation is DIRECTLY related to distance n frequency.
    • To provide optimal images, use high frequency possible and visualize at the depth it's located.
  71. What is AXIAL RESOLUTION?
    • AXIAL RES = helps distinguish between 2 structure parallel to the US beam (located in front of each other).
    • Axial res determines how close the two can be.. it is measured in distance usually mm . 
    • Typically in the 0.1 to 1 mm range. 
    • Shorter pulses and pulse durations enhance axial res. 
    • Axial res superior to lateral res because pulse lengths are shorter than the width of the beam. 
    • Axial res AKA longitudinal = range = radial = depth resolution.
  72. Which beams have better lateral res = wider or narrower ?
    • NARROWER. 
    • Lateral res is controlled by the diameter of the US beam, focus the beam to improve lateral res. 
    • Axial res is superior to lateral res because pulses are shorter than the width of the beam.
  73. What happens to temporal res during an OB exam when the scan line density and imaging depth are decreased?
    • If scan line density and imaging depth are decreased, there will be a positive effect on temporal res. 
    • Increase in frame rate improves temporal res. 
    • Decreased scan line density = less pulses required for image. 
    • Decreased scan line density = degraded lateral res. 
    • Decreased imaging depth = increased frame rate.. reflectors are located at a shallow depth.
  74. What is duty factor and its units?
    • Duty factor = percentage or amount of time a system is transmitting sound. 
    • Duty factor = pulse duration/PRP x 100
    • Duty factor = calculation that HAS NO UNITS.
    • Ranges are: 0.2% to 0.5% or .002 - .005
    • For CW, if duty factor is 1% or 100% because a signal is always being sent. 
    • Duty factor of 0% = transducer is not being used.
  75. Which artifact has a "step-ladder" appearance?
    • Reverberation. It will be in a location parallel to the US beam. 
    • Also called venetian blinds. 
    • Artifacts will always be the same distance from each other.
  76. Which artifact can be identified when the speeds of 2 structures are vastly different with an oblique angle?
    • REFRACTION = oblique incidence. media at different speeds.
    • Refraction can't take place if they have identical speeds.
    • Tissue interfaces, US beam only bend slightly.
    • Bone has larger refraction angles.. speed in bone faster than soft tissues.
    • SNELL'S LAW calculates refraction.
  77. What are the 3 components of attenuation ?
    • REFLECTION, SCATTERING, and ABSORPTION. 
    • 2 types of reflection: Specular and diffuse.
    • - specular when there is a smooth boundary
    • - diffuse when its not smooth and reflection is in various directions AKA backscatter
    • SCATTERING - energy travels in many directions
    • ABSORPTION - when the energy is converted into heat
  78. How much of a beam's intensity is transmitted if 2 media have identical impedance and normal incidence?
    100% will be transmitted. The incident and transmitted intensities must always equal 100%
  79. Which transducer is best for small parts (thyroid, testes)?
    • LINEAR SQUENTIAL. 
    • Long and narrow allows for easy skin contact with the probe because these areas are smaller to reach. 
    • Lateral res changes with scanning depth.. better in FAR FIELD bc this probe has higher freq.
    • Lateral res is best at focal point where beam is the narrowest.
    • Optimize lateral res by using highest number of focal zones.
  80. How does low quality (Q-factor) transducers offer images with improved axial res?
    • Q-factor transducers are used for PW us because they offer improved axial res. 
    • They contain backing material which controls the amount of ringing.. less ringing = shorter pulses = better axial res = better image quality
    • Q-factor transducers offer multiple freq. because of their wide bandwidth. 
    • Axial res offers the most accurate image in modern transducers.
    • Accuracy of axial res is not affected by depth of the image.. in elevational and lateral res, ARE affected.
  81. What is lateral resolution?
    • A resolution that allows you to see 2 reflectors when they are perpendicular to the sound beam and lying beside each other. 
    • Lat res can determine how close 2 structures can be to each other. 
    • Units of lateral res can be any form of distance measurement.
    • The focus is where lateral res is the most optimal because it is the most narrow part. 
    • Lateral res = angular, azimuthal and transverse
  82. What is the effect on temporal res when a sonographer adds multiple focal zones during a study?
    • Using multiple focal zones improves the detail of an image. If single focus, the temporal res will be superior bc frame rate is higher. 
    • If multiple zones are added.. more pulses are required and extra pulses are needed in each scan line. This degrades temporal res bc frame rate is lower. 
    • Multifocus can improve lateral res bc the beam is narrowed over many depths.. but temporal res will suffer.
  83. What transducer will a sonographer use to perform a thyroid US?
    • A linear sequential array transducer AKA linear switched array 
    • It has a thin but wide footprint. 
    • Higher frequency bc the thyroid is superficial.
    • Active crystals arranged in a straight line.
  84. What is the most common step during an US to increase the temporal resolution?
    • To increase temporal res, increase frame rate.
    • On the US system, decrease the depth to increase the temporal res. 
    • A structure deeper in the body needs greater time of flight bc the system is transmitting pulses into the body then back to the transducer to be processed. 
    • Additional time decreased the frame rate and temporal res. 
    • To increase the temporal res, scanning depth should be as shallow as possible so there is less time required to process a signal.
  85. What is duty factor?
    Which does not belong: short PRP, high duty factor, low PRF, shallow imaging
    • Duty Factor = Pulse Duration/PRP x100
    • PRF does NOT belong. 
    • PRF and PRP are inversely related. 
    • shallow imaging = higher PRF
    • low PRP = high duty factor, they are inversely related
    • duty factor = inversely related to scanning depth
    • shallow depth = high duty factor
  86. What is the relationship of the attenuation coefficient in soft tissue and frequency?
    • Attenuation coefficient = frequency / 2
    • basically, attenuation coefficient is half of the frequency
    • Total attenuation = attenuation coefficient x distance
  87. What is the half-value layer thickness?
    • Penetration depth = 3/attenuation coefficient 
    • Half-value layer thickness refers to how far sound is transmitted so that the intensity of the wave can be reduced to half of the original intensity, 
    • Half-layer = penetration depth or half boundary layer
  88. What happens to impedance if density and speed increase?
    • If density and speed increase, impedance also increases. 
    • Acoustic impedance = a calculation that has an impact on the amount of reflection that occurs.
  89. What is Rayleigh scattering?
    • Erratic, unsystematic diversion of the US beam in multiple directions. 
    • It takes place because the actual size of the target is much smaller than the wavelength of the US beam.
    • Rayleigh scattering = proportional to the frequency to the 4th power.
  90. What can the sonographer do to boost axial resolution?
    • Short pulses will generate improved axial res. 
    • Axial res = longitudinal, range, radial, depth resolution. 
    • Higher freq transducers create shorter pulses, which result in shorter wavelengths.
    • Backing material in the transducer limits the amount of ringing in a pulse.
  91. Where in the sound beam is lateral resolution the best?
    • At the FOCUS. 
    • At the focus is where the beam is the narrowest.
    • Lateral res is equal to the beam diameter and smaller values imply better lateral res. 
    • If scan line density is increased, lateral res is enhanced.
  92. Why is axial res not enhanced when focusing is increased?
    • Shorter pulses = better axial res = less ringing
    • When focusing is increased with more focal zones, lateral res improves bc the width of the beam is narrow.
  93. Which controls affect the frame rate?
    • Frame rate controls temporal res. 
    • Changing the scanning depth. Deep structures have poorer temporal res bc there is more listening time = lower frame rate
    • Changing # of focal zones, adjusting field of view (sector size), adjusting the line density.
  94. What determines elevational resolution?
    Slice thickness. It determines if the returning signals are located above or below the imaging plane.
  95. What can the sonographer do to penetrate highly attenuating tissue more readily?
    • Reduce the frequency. 
    • Increase the frequency of the probe = increase attenuation. More absorption takes place with higher frequency probe.
  96. What type of resolution is affected when a radiologist can't determine that cystic structure is indeed a cyst?
    • Elevational resolution. AKA partial-volume imaging artifact. 
    • Elevational res refers to slice thickness of the US beam.
  97. Name an advantage and disadvantage of small footprint transducers.
    • Advantage: Since it's small it can be used to scan intercoastal spaces. ex) linear phased array
    • Disadvantage: Lateral res is reduced bc the beam  splays apart in the far field. Diversion occurs at the depth that is 2x's the length from the face of the transducer.
  98. What is the relationship between scattering and frequency?
    • DIRECT.  Lower freq result in less scatter.
    • Scattering can be random or organized. It alters the direction of the sound wave 360degrees. 
    • Rayleigh scattering = direct relationship with the frequency of the sound beam. Takes freq to the 4th power.
  99. What is the rate of attenuation in bone, lung and soft tissue?
    • Attenuation = weakening of sound through tissue. 
    • Lowest to highest = body fluids, soft tissues, bone, lungs.
  100. How do you calculate axial res while examining structures using a 3.5MHz transducer with a pulse of 6mm?
    • Axial Res = SPL/2
    • AR = 6/2 = 3mm

    AR = wavelength of # of cycles in the pulse / freq
  101. Is lateral res good in the far field if a low or high freq transducer is being used?
    • A high freq transducer would be narrower and reveal less expansion in the far field (Fraunhofer zone).
    • Beams with lower freq diverge more in the far field, creating an US beam that will demonstrate poorer lateral res.
  102. What is the relationship between attenuation and the speed of sound?
    • UNRELATED. 
    • High freq = more attenuation
  103. When using a linear phased array, how many active elements are used to create the beam if there are 110 crystals?
    • # of crystals in a linear phased array transducer = 100-300
    • 110 crystals = 110 active elements are used.
  104. What is the shape of the image when using a linear phased array probe?
    • FAN SHAPED. narrow at the top.
    • A convex phased array, curvilinear probe with be sector shaped and at the top, it would have a curved portion that matches the arc of the transducer face.
  105. Which will NOT produce an image similar to the others: linear phased array, mechanical, linear switched array, curvilinear, or annular phased array?
    Linear Switched Array. (AKA sequential) because it provides an image in the shape of a rectangle
  106. Which transducer component will improve axial res by diminishing the time that the PZT crystal is vibrating?
    • A 1/2 dimension array probe will provide improved elevational res. 
    • The arrangement of PZT crystals in vertical and horizontal planes allow focusing to occur in the plane that controls the thickness of the beam.
    • Thinner slice = better elevational res
  107. 8MHz to Hertz
    • M = mega = million
    • 8 times 1million = 8,000,000 Hz
  108. Which transducer would a CARDIAC sonographer likely choose?
    • Linear phased array transducers. Phased array allows higher frame rate.
    • Has a smaller footprint, allows for intercostal images so the heart can be visualized without rib shadowing.
  109. Why does a linear sequential probe provide identical line density in the near and far fields?
    • Linear sequential (switched) probes have a large footprint and the shape is a rectangle. Crystals are arranged beside each other. 
    • Since scan lines are evenly spaced and parallel, the line density in the near and far fields are identical
  110. Does the diameter of the PZT crystal determine the frequency?
    • NO. but the thickness of the active element does help to determine the frequency. 
    • Freq of sound wave is inversely related to PZT crystal.
    • Thicker crystals = longer wavelength = lower frequency. 
    • Diagnostic probes, thickness of active element = 0.2 to 1mm.
  111. Which phased array transducers will have crystals shaped like a disc?
    • ANNULAR PHASED ARRAY transducers. They are arranged in a concentric ring to look like a target. 
    • Steering with an annular phased array can't be performed electronically, it's considered mechanical.
  112. How is slice thickness and contrast affected with 2D array transducers?
    Thin slice enables better contrast res bc the beam is not wider than the structure, Contrast res is augmented due to diminished volume averaging.
  113. Why is lead zirconate titanate (PZT) used as the active element for transducers?
    • PZT is man made, it can easily be manufactured. This active element is polarized. 
    • Depolarization = if probe is exposed to too high temps. 
    • The thickness of PZT crystal = half of the wavelength found in the active element.
  114. When imaging the spleen, will sound return quicker using 2.5MHz, 3.5MHx or 5MHz freq?
    • If traveling through the same medium freq of sound will have the same speed. 
    • Speed only changes if going through different types of tissues.
  115. How will the US appear if PZT is damaged in a linear sequential array transducer?
    • You will see vertical dropout beneath the active element that is affected. 
    • The image is in the shape of a rectangle.
  116. What is the difference between fundamental frequency and harmonic frequency?
    • Fundamental freq = actual freq being imparted from the transducer to patient. AKA transmitted freq
    • Harmonic freq = 2x's higher than fundamental freq. Helps improve diagnostic capabilities.
    • Types of harmonics = tissue harmonics and contrast harmonics
  117. What is the difference between imaging and nonimaging transducers?
    • Imaging transducers contain a layer called backing material. It is used to create short pulses by inhibiting the amount of time that the PZT crystals are vibrating. 
    • Backing layer lessens the sensitivity.
    • Nonimaging transducers do not have backing material. They produce continuous waves or have very long pulses. 
    • Diagnostic quality exams are produced by probes with a wide bandwidth (Low Q factor)
  118. What component improves the propagation of sound into the body by lessening the impedance between crystals & the patient?
    • Matching layer is located in front of the transducers active element (PZT). Gel with the matching layer improves the propagation of sound into the body. 
    • Thickness of the matching layer is 1/4th of the wavelength of sound within the matching layer.
  119. What is a sonographer evaluating when using the ellipse feature to measure the perimeter or margins of a fetal head or abdomen during an OB exam?
    A circumference measurement. It can give important information pertaining to the weight, biparietal diameter, femur length, abdominal circumference, and information about brain development.
  120. How do you determine the frequency of the sound beam is you're using a 12MHz continuous wave transducer?
    • Electrical frequency = acoustic frequency
    • If the voltage is 12Mhz, the beam freq is also 12MHz.
  121. How is a linear sequential transducer steered?
    • It's in the shape of a rectangle bc the pulses are sent straight out from the transducer in groups. 
    • They are electronically steered. These transducers will never create images wider than the footprint.
  122. What will an operator encounter when a mechanical transducer has a faulty crystal?
    • This type of transducer only has one crystal. If it is damaged the sonographer will not see an image. 
    • In the modern transducers, there are multiple active elements.. if defective, you'll see a vertical (curvilinear or linear sequential) or horizontal (annular phased array) band of dropout.
  123. How do PZT crystals fire in a phased array?
    • Transducers that offer phased array are very advanced bc they offer focusing in all planes & at all depths. 
    • They are excited at time intervals that are close to the next group, creating very small time delays.
  124. If a 10MHz transducer can be bumped up to 12MHz and lowered to 8MHz, what will the main freq be?
    • Bandwidth = freq range within a sound beam.
    • 12Mhz - 8Mhz = 4MHz.. Imaging transducers can roduce many freq.. they tend to have a wide bandwidth.
  125. What are the advantages of using a linear phased array transducer?
    • Sonographer can electronically focus the US beam at all depths. 
    • Focusing can be optimized regardless of the depth of the structure. 
    • The transducer part that touches the pt is flat, but the beam sent out is nonlinear fashion so pulses can reach structures that are not directly in front of them. 
    • They have small footprints, great for cardiac or pediatric scanning or visualizing intercostal spaces.
  126. Why are endocavity transducers preferred during a pelvic exam?
    • They offer better spatial res bc of the close proximity to female organs. 
    • TV ultrasound transducers are high freq vs. the TA (transabdominal) transducers which are lower freq.
  127. How thick should the matching layer be?
    • 1/4th the wavelength of sound. The layer offers protection for the crystals. 
    • The matching layer is used with gel to increase transmission from the PZT crystals to the tissue being interrogated. 
    • Speed of Sound x Density of Medium = Impedance to Flow
  128. What units are used when calculating the volume of a pt's spleen?
    • The planes are used using 2D us. 
    • Volume is displayed in any units cubed.. calculated by multiplying length X width X height .
    • Organs are typically measured in centimeters.. volume is in cm3
    • 3D us is also used to calculate the volume of an organ
  129. What focusing techniques can US transducers use?
    • Focusing = used to improve resolution of an US image by creating a narrow sound beam.
    • External focusing using a lens can improve lateral res. 
    • Fixed focusing = using a lens in front of the active element, it'll provide a more narrow beam. 
    • Fixed focusing without a lens is called internal focusing.. a curve shaped crystal is used but resulted in a tapered US beam. 
    • Electronic focusing is caused by a phased array transducer and is only available on probes with many PZT crystals.
  130. Which measurement taken of the endometrial thickness will be the most precise (an oblique angle to the beam, parallel angle to the beam, or perpendicular angle).
    An angle parallel to the beam so axial res is most accurate

    • In grayscale imaging, axial res is superior to lateral and elevational res. 
    • Axial res = ability to correctly portray 2 objects located parallel to the main part of the US wave. 
    • Axial res not affected by the depth of the reflector, it relies heavily on SPL bc shorter pulses create better images. 
    • Lateral res = portray 2 objects lying NEXT to each other or perpendicular to the US beam. 
    • Elevational res = figures out if reflectors are within the beam of located above or below it.
  131. What can a sonographer do to ensure a radiologist is aware of acoustic shadowing in a patient w gallstones (when using a 3.5 MHz multifreq probe).
    • If gallstones are suspected, sonographer can increase the freq as high as it'll go.
    • Higher freq transducers create narrower US beams. 
    • Or sonographer can bump the freq to 5MHz.
  132. What is the shape of an US image when using a linear sequential array transducer?
    • A rectangular shape. 
    • The image will be wider than the probe's footprint. 
    • These transducers have a relatively small footprint and PZT crystals are located next to each other across the transducer face. They have approximately 120-125 pieces of the active element used to create the sound beam. 
    • Groups of crystals are fired together along the transducer face to steer the beam.
  133. What will a sonographer visualize when they attempt to use a phased array with a defective crystal?
    • If using a convex array transducer, it'll appear as a sector shape that's blunted at the top. If defective, the user will see a vertical band of dropout under the defective crysta. 
    • A curvilinear probe has 120-150 pieces of active elements arranged beside eachother in a curved line. 
    • Linear sequential are parallel to each other bc of the flat shape of the probe. 
    • If an annular phased array transducer, with one ring damaged.. there will be a horizontal band of dropout across the US image
  134. If the slope of the electrical spikes is increasing from left to right, will the beam be steered to the right, left, or not steered?
    • Straight line indicates no beam steering. 
    • In this case, a beam will be directed to the right. This method can be used even if the beam is focused.. however electrical spikes will not be in a straight line
  135. What type of transducer would a sonographer choose to create a 3 or 4D image?
    • 2D transducer. These probes contain thousands of PZT elements arranged in a checkerboard pattern. 
    • 3D rendering can be performed on data that's collected to create 3D images. 3D is considered to be postprocessing.
  136. What is the purpose of the backing layer?
    • AKA the damping element. It's used to optimize the axial res. 
    • It decreases the length of PD (pulse duration) bc it inhibits the amount of time that the crystal will vibrate.
    • Shorter pulses increase the axial res and create higher quality images. 
    • Backing material decreases sensitivity of the transducer and creates a wide bandwidth resulting in low quality factor. 
    • CW Doppler and Therapeutic US are considered high-Q because they have a narrow bandwidth
  137. What is the relationship bt the Q factor and Pulse Duration/Length in a nonimaging transducer?
    • Nonimaging transducers are not able to produce an US image.
    • Ex) CW Doppler, it's used to determine blood flow. Also, therapeutic US bc it doesn't provide an image during use. 
    • There is no backing material, so long pulses are created. 

    Nonimaging transducers considered to have high Q factor bc bandwidth tends to be narrow.
  138. What is the equation to calculate depth of an object?
    • Time of flight.
    • D = ct (c=speed of sound in soft tissue X t=time of flight)/2 

    speed of sound in soft tissue = 1540 m/s (1.54 mm/us)
  139. What happens to wavelength when freq is increased?
    • Wavelength and freq are inversely related as long as biologic tissue stays the same. 
    • Usual range of wavelength = 0.1-0.8mm 
    • If freq increases, wavelength gets shorter

    Wavelength in soft tissue = 1.54/frequency
  140. Can a 12cm image be created from a linear sequential transducer that is 10cm?
    No. Linear sequential transducers can not create images longer than its footprint which is 10cm.
  141. Why when scanning a thyroid, a sonographer would use a transducer with a thin crystal?
    • The thickness of a crystal for US purposes is 0.1-1mm. 
    • Thicker PZT crystals offer lower frequencies
    • Thin PZT crystals offer higher frequencies.
  142. How do linear sequential array transducers focused?
    • They used phased technology. The PZT crystal sends out pulses at different times. 
    • Returning reflections are postponed so they all don't return to the probe at the same time. 
    • Phasing allows for signals to be returned constantly, allowing focusing at all depths.
  143. Why would a convex-array transducer be selected over a linear sequential probe when wanting to obtain the largest possible field of view in the near and far fields?
    • Convex array transducer AKA curvilinear or curved array transducers. 
    • Linear sequential array transducers are in shape of a rectangle bc the arrangement of the active elements. Since curved transducers do not form a sharp peak at the top, they allow for a wider field of view in the near field and the far field.
  144. What is the importance of monitoring the thermal index (TI) during a sonogram?
    • Bioeffects can occur. An increase to as little as 2-4 degrees can cause bioeffects. 
    • TI is directly related to the acoustic output of the machine. 
    • 3 types of thermal indices serve the best in vivo indicators of a rise in temp: 
    • soft tissue thermal index (TIS) 
    • bone thermal index (TIB)
    • cranial bone thermal index (TIC)
    • Ob exams are of great concern bc adverse effects have been identified w an elevated TI value.
  145. What is the best method of obtaining the fetal heart rate during an 11week OB ultrasound?
    • M-Mode (motion mode)
    • Follow ALARA (as low as reasonably achievable) principle bc the intensity of M-Mode is less than what is obtained during PW Dopler 
    • Spectral display should NOT be used bc energy is only located within the sample gate which can lead to tissue heating. 
    • M-Mode does not let you hear the heartbeat but it is safer for early pregnancies.
  146. Why is Doppler flow phantoms used?
    • QA (quality assurance) assures the best image quality possible.
    • US Doppler flow phantoms asses all doppler methods including color, CW doppler, PW doppler and Power doppler imaging. 
    • These devices are used to mimic the cardiovas system.
  147. How can a sonographer clean up low-level reflections in the near field of a well distended urinary bladder?
    • To clean up the reflections, the sonographer would use the reject control on the US system. 
    • Reject AKA threshold, suppression - used to exclude weakened echoes on the US screen.
  148. Why should employers implement proper ergonomic techniques for the US lab?
    To prevent injuries. 20% of injuries are career ending. 75% of sonographers have symptoms of pain, numbness, tingling and swelling.
  149. What are the types of cavitation?
    • When force and freq are applied to tissues: stable cavitation and transient cavitation.
    • Smaller MI indicates stable cavitation will occur.
    • Stable cavitation = increasing, decreasing, and vibration of gas bubbles located within tissue when exposed to pressure of the sound wave. 
    • Transient (normal, inertial) occurs with higher MI readings. 
    • Microbubbles rupture, creating increased pressure and temp measurements.
  150. What is the most effective way to apply the ALARA principle to decrease pt exposure?
    • As low as reasonably achievable is associated with radiation. If the image is too bright, the most effective way to decrease pt exposure is to decrease the output power (aka acoustic power).
    • OR turn down the overall gain to prevent the image from being too bright.. this does not have any effect on pt exposure. 
    • If image is too dark, increase gain bc is does not affect the energy imparted to the pt.
  151. Which US application has shown the lowest levels of tissue heating?
    • When the output intensity is being used at its lowest numerical value. Grayscale imaging is the best method in which tissue heating is the lowest. 
    • It's at its highest when PW doppler is being used. 
    • Use a hydrophone to measure output intensities, it provides accurate values bc of its compact size.
  152. What is the importance of asking a patient is he/she had prior imaging studies?
    • To look at images and read the reports to the sonographer knows exactly what to interrogate. 
    • You can use results to compare. 
    • Fusion imaging allows side by side US imaging with CT or MRI studies. It allows more confidence in the lesion visualized.
  153. What are the applications of Tissue Doppler imaging?
    • This technique can be used as screening for pts with heart dysfunction. 
    • A TDI advantage is the sensitivity, it's useful when considering therapeutic intervention.
    • TDI allows for collection of quantitative data of myocardial function during stress and at rest. 
    • Helps to determine if a pt would be a candidate for a defibrillator or pacemaker.
  154. What artifact is the opposite of shadowing?
    • Enhancement artifact. These fluid filled structures visualized are the result of a lower rate of attenuation than the tissue surrounding them, so structures below may appear brighter. 
    • Enhancement can be of value because radiologists can reassure that a structure is cystic.
  155. What is the intensity limit in which bioeffects have not developed in unfocused and focused ultrasound?
    • SPTA (spatial peak temporal average) - the most pertinent intensity with regard to tissue heating. 
    • If an unfocused US beam, must be a lower intensity limit than if a focused transducer is used. 
    • Unfocused beam is wider, it allows more US energy to reach coss-sectional area of tissue. 
    • 100mW/cm2 is the intensity used for an unfocused beam.
    • Focused beam intensity limit = 1W/cm2 or 1000 mW/cm2.
  156. What is the component of an US system that presents the greatest risk of injury to a patient?
    • Equipment should be inspected on a regular basis. 
    • Machine should be plugged into the correct electrical outlets and cords do not present a trip hazard.
    • The TRANSDUCER accounts for the greatest risk of injury.
    • A damaged transducer can degrade the quality of the image, a cracked transducer can impart an electrical shock to the pt.
  157. Which resolution is being investigated when there are tiny cystic components visualized in a phantom?
    • Elevational res is best determined with a slice thickness phantom. 
    • To define small cystic components within certain depths of the phantom, slice thickness must be very thin.
    • Thicker slices degrade the image detail or res.
    • Fluid filled components may not be visualized at all or may look as they're filled in.
  158. What technique is used to discern a benign mass from a malignant mass by measuring the stiffness of the tissue?
    • Elastography = provides quick and painless measurements of the stiffness of an organ or tissue.
    • B-mode and Color Doppler can be used with the elastogram to provide more information.
    • Benign structures are softer than stiffer malignant structures.
    • Elastography if offered for breast lesions, liver fibrosis and musculoskeletal imaging.
  159. What artifact will appear deeper to a highly attenuating structure, but will offer useful data to help the radiologist make the correct diagnosis?
    • Shadowing artifact appears as hypoechoic or anechoic area deep to the structure that is highly attenuating. 
    • You may notice shadowing posterior to calcifications such as kidney stones.
    • Enhancement = hyperechoic region deep to a structure that is weakly attenuating. 
    • Appearance of enhancement artifacts is different, it provides a radiologist with helpful information when discerning tissues.
  160. What is the level of disinfection necessary for endocavity probes?
    • Use probe covers when using an endocavity transducer. 
    • HIGH LEVEL disinfection. 
    • CIDE OPA is a common disinfectant agent used in labs for endocavity transducers. 
    • For transducers not inserted, low level disinfection will suffice.
  161. What will the sonographer do to decrease the MI when necessary?
    • High MI = higher chance bioeffects will occur. 
    • If MI too high, decrease the output power to reduce the amount of voltage sent to the transducer.
    • Operator should increase the frequency of the transducer bc frequency and MI have an inverse relationship. Lower freq and pressure tend to raise the MI.
  162. What is the study used to identify possible associations between population exposure to a particular medium and hazardous effects?
    • EPIDEMIOLOGICAL studies. 
    • These studies evaluate if any associated bioeffect were found when the pt was exposed to US in utero.
  163. What is the speed of sound through soft tissue for a tissue-mimicking phantom to correctly calculate distance?
    • Sound travels at 1540 m/s in soft tissue or 1.54 km/s or 1.54 mm/us 
    • US travels slowest in gases, quicker in liquids and fastest in solids. 
    • Tissue equivalent phantom is used to calibrate US systems bc the embedded material has known acoustic properties. 
    • Grayscale can be evaluated with this phantom.
  164. What is fusion imaging?
    • aka Hybrid Imaging.
    • A technique that provides sonographers more diagnostic confidence when following up with MRIs or CT studies.
    • It reduces amount of radiation the pt is exposed to. 
    • Fusion imaging requires a sensor that is attached to the transducer that will be able to determine the probe location as well as a transmitter that is attached to the patient.
  165. Which US technique will have the greatest impact on pt exposure when in use (grayscale, color doppler, spectral doppler)
    • TI - thermal index = highest during exam with high frequency, high intensity beam. 
    • Heating depends on exposure time and temperature. 
    • Spectral Doppler exams have the greatest increase in temp. 
    • PW Doppler requires more energy than Bmode or grayscale 
    • TI should be 1.0 or less, time should be minimied to prevent tissue heating. 
    • If TI is 1.0 there is a possibility temp will increase by 1 degree.
    • Ti is expressed by soft tissue thermal index  (TIS), bone thermal index (TIB) and cranial bone thermal index (TIC)
  166. How do you make a pt feel comfortable during an exam?
    • Introduce yourself, explain the exam, answer any questions. 
    • Get through history of the pt, find out if any prior exams were done. Do not relay any information about the exam.
  167. What happens to intensity of the sound beam if its decreased by 3db?
    • When there is a +3db, the intensity is twice as large. 
    • If intensity is 10x's greater, +10dB change. 
    • If decrease in decibel change, signal is becoming weaker or decreasing. -3dB indicates signal decreasing by half of original intensity. 
    • -10dB = reduction by 1/10th.
  168. Which artifact is always visualized at a greater depth than the real structure being used?
    • MIRROR artifact.. a very strong reflector redirects sound waves as it strikes the mirror. 
    • Can occur in grayscale imaging and color doppler interrogation.
    • Color doppler can mirror vessels.
    • Abdominal imaging, lung tissue can be mirrored on either side of the diaphragm which is seen as a bright reflector.
  169. What is the specific intensity that the Merican Institute of Ultrasound in Medicine refers to in the Statement on Mammalian Biological Effects of US in Vivo?
    • In vivo means observing possible bioeffects. 
    • SPTA is the intensity referred to in the statement of mammalian biological effects. 
    • Lab mammals are used to comprehend associated risks that US has on the body.
    • As long as SPTA intensity does not exceed 1W/cm2 and an unfocused beams SPTA intensity stays less than 100mW/cm2 , bioeffects should not occur
  170. Why should a QA (quality assurance) program be implemented?
    • To decrease the # of times a pt must return for additional studies, minimize exams, ensure the machine is performing optimally.
    • QA should be performed routinely or after an upgrade on the machine. 
    • Sonographer should make sure QA exams are completed and a preventative maintenance program is in place.
  171. What are the recommended uses of contrast agents?
    • Orally or injected, used to highlight blood flow. Gas bubbles must transfer out of capillaries while allowing time for an exam to be performed. 
    • Intravenous contrast agents are extensively applied in imaging breast, renal, liver, pancreatic ovarian and prostate cancers.
  172. What type of artifacts are visualized on the edge of a curved reflector?
    • EDGE SHADOW
    • It protrudes from the edge of a curved structure parallel to the axis of the beam. 
    • These are often seen when performing an US of a cyst or during a testicular scan.
  173. Why does a highly focused beam produce greater heating of internal tissue?
    • The energy of the beam is condensed into a thin region, esp at the focus where the beam diameter is already the smallest.
    • May have a positive effect on image res but it can increase internal temp of tissue.
    • Tissue heating relates to SPTA intensity. 
    • Intensity limit of a focused beam is set to 1 W/cm2 or 1000mW/cm2
  174. If freq exceeds 1/2 of the PRF what event takes place?
    • ALIASING. It can also take place when using color doppler.
    • Nyquist limit = greatest velocity that can be tracked before aliasing occurs.
  175. If color map shows red on top, does this demonstrate negative or positive doppler shift?
    Positive bc red is at the top of the color map.
  176. Can PDI (power doppler imaging) be used to determine direction or speed of blood flow?
    • PDI represents if a doppler shift is taken place. 
    • PDI does not evaluate info pertaining to speed or direction of flow. 
    • Advantage  PDI neglects data pertaining to velocity of the signal, aliasing can not occur.
    • PDI aka color angio or energy mode.
  177. In an abdominal aortic doppler exam, why would you see a mirror image artifact of the waveform displays bidirectional flow when it is truly only one flow in direction?
    • If its truly unidirectional flow, the bidirectional flow is artifact. 
    • Crosstalk is a mirror artifact that only occurs during spectral doppler studies.
    • Electronic mirror imaging is associated with crosstalk and may occur if doppler gain is set too high.
  178. What is a corrective action that can be taken if aliasing is visualized with a structure that is at a deep location?
    • Find a different window that allows you to see the structure at a more superficial location.
    • This can eliminate aliasing bc when moving from a deeper to superficial location, PRF increases which raises the Nyquist limit.
  179. What can a sonographer do to the color gain if multiple speckled colors are shown in the color box after color doppler is turned on?
    • Turn the color gain down. 
    • The amplitude should be set at the highest level WITHOUT displaying color specks. 
    • Aliasing occurs when doppler gain is set too high.
  180. During color doppler exam, how can a sonographer eliminate aliasing artifacts?
    • CHANGE THE VELOCITY SCALE.
    • If scale is set too low but velocities are detected high flow vessels, then aliasing may occur.
    • Increase the velocity scale. 
    • OR switch to a lower freq transducer.. this will allow better penetration and be less likely to alias.
  181. What can the operator do to the color scale to correctly display color flow within a patent blood vessel in which aliasing is present?
    • Raise the scale for the color doppler. 
    • Increase in scale will most likely remove aliasing in this case.
  182. What is packet size?
    • Used in color doppler to get a precise measurement the velocities of moving blood cells. 
    • It's a collection of the number of pulses to examine a color scan line. 
    • AKA ensemble, shots per line
  183. What are the advantage of PDI (power doppler imaging)?
    • AKA energy mode or color angio. 
    • It determines that a doppler shift has taken place and shows amplitude of the moving blood. 
    • PDI has an increase sensitivity.. flash artifact can appear if the person moves or breathes. 
    • Compared to color doppler the temporal res is greatly reduced. 
    • PDI does NOT evaluate direction or velocity of blood flow.
  184. Which type of doppler uses two crystals?
    • CONTINUOUS WAVE doppler.  2 crystals to transmit and receive
    • the pulse.
    • It can be used when a sonographer is trying to eliminate aliasing.
  185. Which does NOT offer range resolution: 
    color doppler, cw doppler, or pw doppler?
    • CW DOPPLER. Spectral analysis obtained suffers from range ambiguity artifact. 
    • Very high velocities can accurately be measured w CW doppler, signals that are received arise from the entire line that was positioned on the screen.
  186. What can be done while using pulsed doppler if the entire spectral display shows too much noise?
    Reduce pulsed doppler gain. Turn the gain down so spectral window is clear.. systolic and diastolic components can be easily visualized along with forward flow patterns.
  187. Why is it important to understand the relationship bt the PRF and the Nyquist limit to eliminate aliasing?
    • Nyquist limit = greatest velocity of blood flow that can be measured just before aliasing occurs. 
    • PRF and Nyquist limit are directly correlated. 
    • Low set scale will have a lower Nyquist limit and greater chance of aliasing. 
    • High PRF = slim chance of aliasing
  188. Can color doppler exam exhibit aliasing?
    • YES. A color box can be layered on top of a Bmode image. 
    • Color doppler provides information regarding the direction of blood flow and is prone to aliasing.
  189. What can a sonographer do during a doppler exam that is picking up velocities from an artery and a vein?
    • PW doppler provides range resolution which lets users know precisely where velocity measurements are being taken. 
    • The size of the gate aka Sample Volume can be used to sample a portion of the vessel. 
    • Adjust the gate size!
    • Newer systems will allow you to display grayscale, color doppler and spectral doppler at the same time.
  190. How can the direction of blood flow be discerned in a sector shaped image with a vessel that is in a horizontal direction?
    • Color flow in a sector shaped image can not be steered as it can with a linear transducer.. Only size and location can be adjusted. 
    • Color beneath the black line on the color map refers to blood moving AWAY from the transducer.
  191. Does increasing the wall filter change the appearance of turbulent flow in an artery?
    • No. Increasing the wall filter will NOT remove the appearance of the turbulent flow. 
    • Wall filters help to eliminate ghosting artifacts that are visualized during color doppler exams. Ghosting is when color is seen outside of the vessel.
  192. When using color doppler, what does the packet size represent?
    • Packet size = ensemble length or shots per line. 
    • The level of the packet size can be raised when trying to image smaller vessels bc the US machine will be able to detect low-flow states more readily.
  193. What is the difference bt phasic and steady flow?
    • 3 types of blood flow = phasic, pulsatile, steady flow. 
    • Phasic is seen in veins.. it shows changes associated with breathing that causes blood cells to speed up or slow down.
    • Steady flow is constantly present in the venous system.. it happens when the pt holds their breath.
    • Steady flow moves at the same speed. 
    • No acceleration or deceleration is present due to the contraction of the heart.
  194. A color map displaying red at the top and blue at the bottom, what does a vessel with blue color indicate?
    • The black line between represents a doppler shift not present. The color on top is blood going towards the transducer, beneath is blood flow moving away from the transducer. 
    • Blue is at the bottom so it is moving away from the transducer.
  195. What are the advantages and disadvantages of a larger packet size?
    • Advantages = heightened receptiveness to blood vessels that have blood flow moving at a slower velocity. 
    • Larger packet size = more pulses sent out for every scan line available, velocity measurements more precise.
    • Disadvantages = since more pulses required, frame rate and temporal res re degraded bc more processing time is required.
  196. Why is doppler angle critical when measuring velocities during a carotid duplex exam?
    • The moving red blood cells should be parallel to the transducer. 
    • When it is not exactly parallel, the velocity measurement will not be as accurate.
    • If the angle cursor is larger than the actual doppler angle, the velocity will be too high.
    • If the angle cursor is lower than the angle that is parallel to the vessel wall, the velocity will be underestimated.
  197. Why can't a doppler shift be identified when the incident angle is 90 degrees to the vessel being imaged?
    • Ideal incident beam is when the transducer is placed 90degrees to the object being scanned. 
    • For doppler, max freq shift will be obtained with an incident angle of 0 degrees (blood being toward the transducer). or 180 degrees (blood moving away) 
    • The cosine of 90degrees is equal to 0
    • So, we can't measure any doppler freq when the incident beam is 90degrees (perpendicular) to the direction of blood flow.
  198. What happens to the PRF when scale is maximized to prevent aliasing?
    • Aliasing occurs when the freq shift is greater than the Nyquist limit. 
    • Nyquist limit = 1/2 of the PRF
    • If PRF increases, Nyquist limit increases.. so the chance of seeing aliasing is not as likely.
    • When maxing the PRF scale, the system might not recognize vessels with slower blood flow.
  199. Will a color Doppler exam be successful in a patient with anemia?
    • Anemia = lower than normal amount of red blood cells circulating in the blood.
    • Not enough hemoglobin in blood.
    • Hemoglobin = protein that has iron, transports oxygen from lungs to all cells in the body. 
    • Yes a pt that is anemic will have enough amt of red blood cells for a successful doppler exam.
  200. How can a sonographer discern the direction of blood flow in a vessel while using linear probe when steering is used?
    • Use the color box and angle it to the vessel. 
    • From the placement of the probe.. determine if color is moving toward or away.
  201. How can adjusting the baseline eliminate aliasing?
    • If flow is wrapping around the baseline, this is aliasing artifact. 
    • Adjust the baseline.. if flow is above the baseline but aliasing occurs, the user can move the baseline lower so the entire waveform is going in one direction.
  202. What can a user do to the color gain in order to optimize color flow of a patent carotid artery in which color is not immediately seen?
    • First determine the angle of the color box with the direction of blood flow. If the box is perpendicular (90degrees) to a vessel, color will NOT be visualized. 
    • Next, increase the color gain - this will show the amplification of signals within blood vessels, but it won't show if blood flow is actually present.
  203. When comparing the velocity scales of color and PW doppler, which requires more scan lines of information?
    • Velocity scale AKA PRF is what sonographers use during color and PW imaging. PRF controls how rapidly data sampling takes place.
    • High PRF allows more sampling bc less listening time bt the pulses being transmitted into the body. 
    • Color doppler requires 8 pulses/scan line. 
    • Spectral analysis can measure velocities and provide info about the direction of flow - it requires 256pusles/scan line.
  204. When using a variance mode map, what do the colors mean?
    • Directional flow. Velocity of red blood cells. Flow pattern of the blood.
    • Normal flow is laminar flow.. it is represented by flow on the left of the color map. 
    • Turbulent flow is the opposite and is found on the right of the color map.
    • Turbulent flow = blood in a stenotic vessel.
  205. Which artifact may be visualized bc of patient motion when using power doppler imaging (PDI)?
    Flash artifact - a burst of color visualized when there is motion taking place outside the blood vessels.. often caused by pt motion.
  206. How can you overcome aliasing with CW doppler?
    • Aliasing only occurs with pulsed doppler (color and pulsed wave spectral doppler). 
    • No listening time with CW transducers.. so there is no limit on the freq shift. 
    • CW doppler is important bc it accurately measures high velocity blood flow bs aliasing never occurs with this modality.
  207. What does a sonographer check if color is not displayed within a vessel after turning on color doppler?
    • Immediately consider the angle of incident beam with regard to flow angle. If angle is 90degrees, color will not be visualized. The cosine of 90degrees is 0 = no color. 
    • Angle the color box so the beam is not 90degrees. 
    • Increase the scale and color gain to increase amount of blood visualized.
  208. How can a sonographer differentiate bt flow reversal and aliasing during color doppler?
    • Pay attention to the color map. 
    • Increase velocity sale to remove aliasing artifacts from a color doppler exam. 
    • If colors wrap from top around outside and to bottom of the map, aliasing is present. 
    • Colors in the middle that mix with each other show bidirectional flow is present.
  209. Does aliasing occur during Power Doppler Imaging (PDI)?
    • No, there is no data pertaining to velocity.
    • PDI focuses on if a doppler shift is taken place. 
    • It does not tell if speed and direction (velocity) but rather AMPLITUDE. 
    • PDI is more sensitive than color doppler so its often used to visualize blood flow in smaller vessels or areas of low flow (venous)
  210. What's the next step a sonographer should take if its assumed that the measurements from a pulsed wave doppler is inaccurate?
    Switch to a continuous wave doppler. If user cannot eliminate aliasing after trying to change the scale or depth and switching to a lower freq probe.. CW doppler can be used.
  211. How does the velocity of blood correlate to spectral broadening?
    • Spectral broadening is typical when turbulent (high velocity) blood flow is sampled. 
    • It may be present when small vessels are being investigated or where a vessel bifurcates.
  212. How can the Nyquist limit be calculated when the imaging depth is 4cm using a 5MHz transducer & a pulse repetition freq (PRF) of 3000 Hz.
    Nyquist limit = PRF/2

    3000/ = 1500Hz or 1.5 kHz. 

    Imaging depth ad fundamental freq are not needed to solve this problem, that was extra info.
  213. What is the advantage of a CW doppler?
    • Precise measurements can be obtained bc 2 crystals are used instead of 1. One is always listening or receiving signal. 
    • CW never displays aliasin be only PW doppler will alias. 
    • Disadvantage = no sample gate..
  214. How can the user adjust the spectral doppler gain if spectral display can barely be visualized?
    • Turn up the PW doppler gain. If its turned up too high, noise may appear in spectral display. 
    • Increase the gain by turning up until noise appears.. then reduce til noise disappears.
  215. What do you do to the color box to improve frame rate?
    • Limit the size of the color box to location of interest. 
    • Color box size decreases = frame rate or temporal res increases bc less information needs to be processed.
  216. If wall filter increases using color doppler, does this affect the high or low velocity flow in blood vessels?
    • LOW VELOCITY. Venous flow is slower than arterial flow.. by changing the wall filter (high pass filter) to a high settig, it rejects color doppler from the vein. 
    • Wall filter does NOT affect vessels in high velocity flow. 
    • Can possibly eliminate ghosting artifacts
  217. How many crystals in transducers that offer PW doppler?
    • ONE. bc the sonographer places the sample volume (gate) in the precise position. 
    • Transducers that allow pulsed doppler are able to create a grayscale image. AKA duplex/triplex imaging. 
    • = gray scale, color doppler and pulsed wave doppler.
    • CW transducer has 2 crystals. Transmits & Receives.
  218. What method allows clinicians to study the individual velocities of blood cells in a sample?
    • Spectral analysis. 
    • It simplifies the many doppler shifts that are produced when blood travels through the body. 
    • It can help diagnose any vascular disease. 
    • When pathology is present, vessels change shapes and sizes, flow patters change.
  219. If the femoral artery is being imaged at 35 degrees but the waveform is aliasing, what do you do to the PRF?
    • Increase the PRF to unwrap the spectral display.
    • This will increase the nyquist limit aka aliasing freq.. it is equal to half of the PRF. 
    • Change the baseline or switch to a lower freq transducer.. or find a window at a shallower location. Angle of incidence can be increased to hep eliminate aliasing.
  220. Why is range res an advantage of pulsed wave doppler?
    • AKA range specificity bc a specific location is chosen. 
    • CW does NOT offer range res bc the sample is being obtained from every vessel in the path of the us wave. 
    • Range ambiguity occurs with CW doppler.
  221. Why is sensitivity so high with CW transducers?
    • High sensitivity to blood flow because these probes do not have a backing (damping) material. 
    • Backing material inhibits the amount of ringing. 
    • CW probes are helpful to detect doppler shifts in the foot. 
    • Matching layers RE present in CW probes to allow for propagation of sound.
  222. What role does wall filter play in color doppler?
    • It can remove doppler shifts below a certain freq during spectral and color doppler interrogations. 
    • It helps remove lower freq doppler signals that can arise from the heart or blood vessels. 
    • Wall filters = high pass filters 
    • Slower blood flow = lower freq doppler shifts
    • The system is less likely to detect blood thats moving slowly when the wall filter is set at a higher level.
  223. Why will a more superficial sample volume allow for a more precise velocity reading during a PW doppler exam?
    • If sample volume is shallow, more precise readings bc it can be sampled more times per second. 
    • Shallow samples create high PRF & high nyquist limit. 
    • Aliasing less likely at superficial depths. 
    • Deeper reflectors require lower PRF which lowers the Nysuist Limit. 
    • Nyquist limit = aliasing frequency
  224. How do you correct an aliasing artifact during a carotid duplex exam imaged at 35 degrees with a 10MHz transducer?
    • Reduce the transducers Doppler freq. PRF scale should be increased to raise the Nyquist limit & baseline could be moved down. 
    • Also you can increase the angle of incidence or switch to CW doppler.
  225. What will happen to the frame rate if the PRF is decreased during an exam using only B mode?
    • Scanning depth and temporal res have a direct correlation. 
    • PRF if adjusted when scanning depth is changed. (indirect relationship)
    • Increased depth = Higher PRF

    PRF is lower so the object is deeper in the body.. Greater depth = decrease of temporal res.
  226. Name the major disadvantage of PW Doppler?
    • Inability to accurately measure high velocity blood flow. 
    • To eliminate aliasing, set scale high, adjust baseline, select lower freq, find a window thats more shallow. 
    • Aliasing will NEVER take place when using CW doppler.
  227. Is a high or low freq transducer better at eliminating aliasing artifacts?
    • LOWER. Higher freq probes more prone to create aliasing. 
    • Doppler shifts are smaller when low freq probes are used so aliasing does not occur as often w/ lower freq transducers. 
    • Grayscale image nay suffer as a result of lower freq
  228. What role does intermittent sampling play in PW doppler aliasing artifacts?
    • Intermittent sampling = ocurrs if Doppler freq isn't evaluated correctly. 
    • Aliasing is common during PW doppler due to intermittent sampling.
  229. When using doppler, what parameters contribute to a patient's risk of bioeffects?
    • Sonographers should be aware of ALARA. 
    • Grayscale exposes the least amount of bioeffects. 
    • Increased PRF contributes to pt exposure the most bc more pulses being sent into the body.
  230. As long as aliasing is not present, what may be represented with velocities below the baseline?
    • Blood flowing away from the transducer. 
    • Color flow doppler allows users to determine which direction the blood is traveling.
  231. When imaging smaller vessels in the lower leg with slow blood flow, what do you do to the PRF in order to better visualize color doppler?
    • Adjust the PRF aka color scale.
    • Lower PRF enables system to recognize red blood cells that are moving slowly bc more time is allowed from one pulse to the next. This will increase the sensitivity of the color doppler. 
    • To iprove color dopper sensitivity to low flow.. increase doppler freq and decrease the value of the wall filter.
  232. What is the technique called when you use pulsed doppler to provide info about various velocities obtained in a sample volume?
    • Spectral analysis. 2 Types = FFT fast fourier transform & autocorrelation. 
    • FFT = method used to operate the spectral analysis during PW & CW doppler. It can determine if flow pattern is turbulent or normal (laminar) flow. 
    • Autocorrelation only used during color doppler but faster than FFT method.
  233. Does increasing wall filter affect the higher or lower velocity flows during spectral analysis?
    • It only removes the lower freq doppler shifts from slower blood flow. 
    • High wall filter level will decrease the ability to detect slower flow. 
    • In a carotid doppler study, if you can't measure the velocity of the end diastolic flow.. decrease the will filter.
  234. What do you do to the Nyquist limit to prevent aliasing during a pulsed dopper exam?
    • INCREASE the nyquist limit. Raise the PRF. Find a shallower window. 
    • PRF is determined by the depth of the reflector. 
    • Deeper depth = lower PRF = lower Nyquist limit.. decreased value makes US more susceptible to aliasing
  235. What is spectral broadening?
    A display of a range of doppler shifts that are apparent within the sample blood flow taken in a vessel. This can happen due to stenosis or tortuous vessel.
  236. What can be done to the PRF to help visualize rapid moving flow in vessels?
    • If fast flow, increase the PRF.. it raises the nyquist limit to avoid aliasing. 
    • Next increase color gain if the vessel isn't completely filled with color.
  237. What are the ranges of Reynolds #s for laminar and turbulent flow?
    • Reynolds # = predicts the onset of flow that is turbulent. It is a unitless value tht is calculated from this equation = 
    • Reynolds # = avg flow of speed X vessel diameter X density / viscosity
    • If less than 1,500.. laminar flow
    • If more than 2,000.. turbulent flow
    • If bt 1500-2000.. disturbed flow
  238. What angles provide the greatest doppler shift?
    • Doppler shift is its highest at 0 or 180 degrees. This parallel movement can be either toward or away from the transducer.
    • Anything other than 0 or 180 degrees the velocity is less precise. 
    • At a 90degree angle with pw doppler, no doppler shift will take place bc it is 0.
  239. Doppler interrogation of the same artery..
    What is the 2nd velocity measurement if a user takes the first measurement with 60degree angle and a velocity of 4m/s..
    The second angle is measured parallel to the blood flow (0degrees)
    • Cosine of 0 = 1. 
    • Cosine of 60 = 0.5
    • Multiply the first velocity by a factor of 2 to calculate the second velocity which equals 8cm/s .
    • The cosine of 90 degrees is equal to 0
    • Doppler shift cannnot be obtained when sound beam is perpendicular to blood flow.
  240. Which component of blood allows for the reflections to be seen by human eye with color doppler?
    • Life span of RBC = 120 days. 
    • Because rbc are traveling in the heart and blood vessels, they create reflections that are seen by the human eye when color doppler is turned on.
  241. Why does range ambiguity exist when the PRF is too high for the scanning depth?
    • Range ambiguity artifact = range specificity = range resolution is prevented when an US operator uses PW doppler. 
    • Sample volume is used to determine the exact location of a velocity measurement..
    • PRF (scale) is set too high in this example.. for the depth of the reflector.. range ambiguity exists bc the system will be directed to send out pulses before the earlier pulses have been returned. 
    • Aliasing will occur which can be fixed by increasing the scale.
  242. Describe a positive doppler shift.
    • Frequency reflected is greater than the transmitted frequency. 
    • If rbc moving in opposite direction of the transducer, a negative doppler shift would take place. 
    • Amount of doppler shift that occurs is directly proportional to the freq of the transducer. 
    • If repeated with a transducer with 2x's freq, doppler shift (freq) will be doubled.
  243. What is the new doppler shift if doppler freq was 4,000Hz in a vessel in which velocity increased from 3cm/s to 6cm/s ?
    • Velocity was doubled so the doppler freq shift follows.. 4,000 x 2 = 8,000 Hz. 
    • Doppler shift and velocity have a direct relationship.
  244. What flow is visualized during an echo?
    • PULSATILE. Since the heart is constantly contracting and relaxing.. velocities of blood flow will fluctuate bc the movement of the heart wall. 
    • Pulsatile flow is visualized in arteries bc blood is moving at a greater velocity than it is in the venous system.
  245. What is the method to measure the velocity of blood flow in the body?
    • DOPPLER principle. 
    • Higher velocity creates a greater doppler shift. 
    • Blood flow velocities reported in m/s
  246. What is laminar flow?
    • Normal flow. Laminar flow will not be heard.. this flow is layered, smooth, and travels parallel along the vessel. 
    • Plug flow = same velocities all throughout
    • Parabolic pattern = higher velocity in the middle of the vessel and lower velocity along the walls. 
    • Parabolic is similar to a bullet. 
    • Laminar flow has a Reynolds number less than 1,500. 
    • Turbulent flow Reybolds number is over 2,000.
  247. What is the range in which a Doppler shift takes place?
    • Doppler shift -= reflected freq - transmitted freq
    • Doppler shift = doppler freq.. provides info pertaining to VELOCITY

    Freq of transducers used during a doppler exam ranges from 2 to 10mHz.. the RANGE in which sound can be heard is 20Hz-20,000Hz.
Author
TiaTaxin
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358230
Card Set
Flashcard SPI Notes
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