ARDMS 2

Card Set Information

Author:
Joy
ID:
23831
Filename:
ARDMS 2
Updated:
2011-08-27 14:04:36
Tags:
ARDMS
Folders:

Description:
Ardms 2
Show Answers:

Home > Flashcards > Print Preview

The flashcards below were created by user Joy on FreezingBlue Flashcards. What would you like to do?


  1. What is the average velocity of ultrasound in soft tissue at 5 MHz
    1540 Meters per second
  2. Red Blood cells are an example of
    Non-specular reflector
  3. Which has a higher acoustic impedance coefficient
    Solid
  4. A hyperechoic Region
    Echogenic
  5. The angle of refraction is described by
    Snells Law
  6. What is reflection in multiple directions from a reflector that is small relative to the wavelength?
    Rayleigh Scatttering
  7. Receiver demodulation can not be controlled by the sonographer?
    True
  8. Reflection at a tissue interface depends primarily on
    Impedance
  9. Azimuthal resolution is also known as
    Lateral Resolution
  10. What is the Doppler shift frequency in soft tissue if the transmitted frequency is 3 MHz and the velocity of a reflector is 20 cm/s
    780 Hz
  11. True or False...Intensity of the ultrasound beam is proportional to the square root of the acoustic pressure
    False
  12. True or false...Aliasing is not a problem with color flow imaging?
    False
  13. True or false...Density is an acoustic variable
    True
  14. If th PRF increases, duty factor ____
    Increases
  15. True or false...A-mode is mainly used to measure distance?
    True
  16. Period is
    The time it takes to complete a single cycle
  17. Spatial pulse length is determined by the
    Oscillator
  18. Transmission angle is less than the incident angle if the propagation speed of
    Medium 2 is less than that of medium 1
  19. Diffraction is the
    Spreading out of an ultrasound beam
  20. Annular array transducers steer the beam
    Mechanically
  21. ____ is a Rayleigh Scatter
    Red cell
  22. True or false...A bit is the smallest part of digital "word"
    True
  23. Velocity times density equals
    Impedance
  24. What is the pulse duration for five cycles of 5 MHz ultrasound?
    1.0 microsecond
  25. Aliasing artifacts are unique to
    Pulsed Doppler
  26. True or false...Intensity reflection coefficient depends on acoustic impedance mismatch
    True
  27. True or False...Velocity of sound in a medium is constant regardless of frequency?
    TRUE
  28. Density is not an acoustic variable
    False
  29. If the PRP increases, duty factor
    Decreases
  30. True or False...A high PRF is needed to image deep structures
    False
  31. Longitudinal waves are
    Parrallel to the axis of the wave propagation
  32. Wavelength has the greatest effect on
    Axial Resolution
  33. What is necessary to calculate distance to a reflector?
    Propagation speed and round trip time
  34. Scattering is
    Redirection of the sound beam in many directions
  35. The percentage of ultrasound reflected at an air/liquid interface is
    High
  36. A specular reflector has surface texture___ the wavelength of the incident wave
    Irrelevant to
  37. In a cathode ray tube displays device the electron beam is steered by
    Deflection plates
  38. If it takes 50 microseconds for a pulse to return as an echo, how deep is the reflector?
    3 cm
  39. Q value is determined by
    Frequency and bandwidth
  40. Shadowing artifacts are
    Caused by differences in attenuation
  41. True or False...A-mode scanning represents the depth of the signal in the horizontal dimension
    True
  42. Poiseuille's equation states that the volume rate of flow through a vessel is inversely proportional to
    Blood viscosity
  43. True or False...Temperature is an acoustic variable
    True
  44. Spatial pulse lengh ___ if the frequency is increased
    Decreases
  45. The Reynolds number predicts aliasing
    False
  46. Transverse waves are
    Perpendicular to the axis of the wave propagation
  47. Beam diameter determines
    Lateral Resolution
  48. Mirror image artifact is sometimes seen near the
    Diaphragm
  49. The Binary number 1011000 equals the decimal number
    88
  50. Low Frequency transducers have
    Longer wave lengths and greater penetration
  51. ALARA PRINCIPLE
    Use minimum output power and highest receiver gain required to produce optimal images
  52. AIUM Suggest
    • -Do not perform studies without reason
    • -Do not prolong studies without reason
    • -Minimize exposure time
  53. Transverse Wave
    Particles move in a perpendicular direction or to the direction of the wave
  54. Longitudinal wave
    Particles move in the same direction as the wave
  55. Compressions are regions of
    higher density and pressure
  56. Rarefaction are regions of
    lower density and pressure
  57. Acoustic Variables inform us of which waves are
    sound waves
  58. Acoustic Parameters describe the features of
    a particular sound wave
  59. Period is
    The time required to complete a single cycle
  60. Frequency is $
    Number of certain events that occur in a particular time duration
  61. Ultrasound is $
    • A wave with a frequency exceeding 20,000 Hz (20 KHz)
  62. Audible Sound is $
    Heard by man, frequencies between 20Hz and 20,000Hz
  63. Infrasound is $
    Sound with frequencies less than 20 Hz
  64. As frequency increases period,
    decreases
  65. As frequency decreases period
    increases
  66. Amplitude is
    The difference between the average value and the maximum value of an acoustic variable. The variation of an acoustic variable.
  67. Units of Amplitude, Those of acoustic variables
    • Pressure
    • Density
    • Particle motion
  68. Relationship between Power and Amplitude
    Power is proportional to the waves amplitude squared
  69. If the Amplitude is doubled, the power is increased by a factor of four (quadrupled)
    2x2=4
  70. Wavelength is
    • The length or distance of a single cycle.
    • Determined by source and medium
  71. Which intensity has the lowest power?
    SATA
  72. Propagation Speed is
    The rate that sound travels through a medium. Also called velocity or speed
  73. Speed and wavelength are directly related
    remember
  74. Stiffness and speed
    same direction
  75. Density and speed
    opposite directions
  76. Bulk modulus is the same as
    stiffness
  77. Interference is
    when two waves overlap at the same location and at the same instant in time, they combine into one new wave
  78. Constructive interference $
    Occurs when the amplitude of the new, combined wave is greater than the original two waves. In phase waves interfere constrctively
  79. Destructive interference $
    The amplitude of the new wave is less than one of the original waves. Out of phase waves interfere destructively.
  80. The effects of ultrasound upon tissues are called
    bioeffects
  81. Pulsed sound $
    • in diagnostic imaging, short burts or pulses, of acoustic energy are used to create anatomic image.
    • A pulse is a collection of cycles that travel together.
  82. Pulse Duration $
    The time from the start of a pulse to the end of that pulse, the actual time. that the pulse is on
  83. In clinical imaging, a pulse is comprised of $
    2-4 cycles
  84. Pulse repetition period
    is the time from the start of one pulse, to the start of the next pulse. It includes one pulse duration and one "listening time"
  85. As imaging depth increases $
    Pulse Repetition period increases
  86. Pulse repetition Frequency
    Is the number of pulses that occur in one second
  87. Typical values for PRF $
    1,000 to 10,000 Hz (1-10 kHz)
  88. Shallow image
    Higher Pulse Repetition Frequency
  89. Deep image
    Lower image, lower PRF
  90. As imaging depth increases, PRF
    decreases (inverse relationship)
  91. Duty factor
    The percentage or fraction of time that the system transmits sound. Important when discussing intensities.
  92. Typical values for duty factor $
    from 0.1% to 1% or 0.001 to 0.01
  93. CW sound cannot be used to make $
    anatomical images
  94. Important concept
    Terms that have the same meaning
    • shallow imaging Deep Imaging
    • high pulse repetition Frequency Low pulse repetition frequency
    • short pulse repetition period long pulse repetition frequency
    • high duty factor low duty factor
  95. Spatial Pulse Length
    The length or distance that a pulse occupies in space. The distance from the start to the end of one pulse.
  96. By adjusting the imaging depth, the operator changes the
    pulse repetition period, pulse repetition frequency, and duty factor
  97. Intensity is
    the concentration of the power in a beam
  98. Units for intensity
    Watts/square cm, w/cm2
  99. SPTP
    Spatial Peak
  100. SATP
    Spatial average, temporal peak
  101. SPTA $
    • Spatial peak, temporal average
    • most important for thermal bioeffects
  102. Three commandments on Intensity
    • 1. Intensities may be reported in various ways with respect to time and space
    • 2. Intensity is the key parameter with regard to bioeffects
    • 3. The different intensities are important in the study of bioeffects. SPTA intensity is the most relevant intensity with respect to tissue heating.
  103. Decibels
    • A logarithmic scale
    • A relative scale- ratio of the final to the initial strengths
    • A comparision, therefore, two intensities are needed to calculate decibels
  104. What are the units of relative amplitude?
    dB
  105. Positive decibels means getting bigger. The intensity is
    increasing
  106. Negative decibels
    means getting smaller. The intensity is increasing
  107. Attenuation is
    The decrease in intensity, power and amplitude of a sound wave as it travels. This unrelated to speed! The further US travels, the more attenuation occurs.
  108. Attenuation units
    dB, decibels (must be negative)
  109. Three components of Attenuation
    • Absorption (sound energy converted into heat energy)
    • Scattering
    • Reflection
  110. Attenuation in different media
    AIR
    much, much more attenution than in soft tissue. GEL is used to remove air from the path of ultrasound.
  111. Attenuation in different media
    LUNG AND BONE
    More than soft tissue, bone absorbs and reflects. Lung scatters.
  112. Attenuation in Different Media
    WATER
    Water much, much less than soft tissue
  113. Attenuation in blood is equal to that in
    Soft tissue
  114. Attenuation is unrelated to propagation speed. Attenuation increases with
    • Higher frequency or
    • Longer path length
  115. A 3 MHZ sound beam travels through two media. It attenuates 5 dB in medium A and 6 dB in medium B. what is the total attenuation that the sound beam undergoes as it travels through both media?
    11 dB
  116. A 10 MHZ sound beam travels through two media. It Attenuates 5 dB in medium A and 1 dB in medium B. What is the total attenation that the sound beam undergoes through both media?
    6 dB
  117. A 3 Mhz sound beam travels 10cm, 6 cm in medium A and 4 cm in medium B. The total attenuation is 14 dB. If the sound beam attenuated 4 dB in medium A, then how much attenuation occured in medium B.
    10dB
  118. A 3 MHz sound beam travels 7cm in a medium. The total attenuation is 5 dB. How much attenuation will a 6 Mhz sound beam undergo when traveling 3.5cm in the same medium
    5 dB
  119. Reflection $
    Occurs when propagating sound energy strikes a boundary between two media and some returns to the transducer.
  120. Specular Reflection
    • Reflections from a smooth reflector (mirror) are specular and return in one direction.
    • Specular reflection also occur when the wavelength is much smaller than the irreugularities in the boundary.
  121. Rayleigh Scattering $
    If a reflector is much smaller than the wavelength of sound, sound is uniformly distributed in all directions (omnidirectional) Higher frequency sound undergoes more Rayleigh scattering. A red blood cell is a Rayleigh scattering.
  122. Rayleigh scattering is related to $
    Frequency
  123. Attenuation Coefficient
    the amount of atttenuation per centimeter. A way to report attenuation without dealing with distance.
  124. Units for Attenuation Coefficient
    dB/cm
  125. Impedance is calculated not $
    measured
  126. Reflection of an ultrasound wave depends upon different acoustic impedances of the media on $
    either side of the boundary
  127. Two media a & b, have the same propagation speed. Medium a's density is 10% higher than medium B's.
    Therefore medium A's impednace is 10% higher than medium B's
  128. In soft tissue, attenuation coefficient is directly related to
    • Frequency
    • if frequency doubles, atten. coeff. will double
  129. Rayleigh scattering is related to
    Frequency 4
  130. Normal incidence
    • Perpendicular, Orthognonal, Right angle, ninety deggres
    • Remember PORNN
  131. Oblique incidence
    Anthing other than 90 degrees, not at right angles.
  132. Acute angle
    less than 90 degrees and are oblique
  133. Obtuse Angle
    are greater than 90 degrees and are oblique
  134. A sound wave with an intensity of 50 w/cm 2, strikes a boundary and is totally reflected. What is the intensity reflection coefficient
    100%
  135. A sound wave, with an intensity of 50w/cm2, strikes a boundary and is totally reflected. What is the reflected intensity?
    50w/cm2
  136. The intensity reflection coefficient of sound beam is 99.9% . what percent of sound is transmitted into the body?
    0.1%
  137. Reflection occurs only
    if two media at the boundary have different acoustic impedances
  138. Transmission and reflection may or may not occur with oblique incidence, but there are no simple
    rules to predict if so.
  139. Refraction is
    transmission with a bend. Refraction is a change in direction as sound transmits from one medium to another.
  140. Refraction requires
    • occurs when two conditions are met.
    • 1. Oblique incidence and
    • 2. different propagation speeds
  141. Snells Law
    The physics of refraction are described by Snells law
  142. Sound wave strikes a boundary at normal incidence. The impedances of the two media are indentical. What percentage of the sound wave is refracted?
    0%
  143. Range equation
    since the average speed of US in soft tissue (1.54 km/s) is known the time of flight and distance that US travels in the body are directly related.
  144. Time of flight is the time needed for a pulse to travel to and from the transducer and the reflector is called
    go return time or time of flight or round trip time
  145. When one reflector is twice as deep as another reflector, the pulses time of flight is doubled for the deeper reflector. In other words
    The time of flight will be increased by a factor of two
  146. In soft tissue, every 13 micro seconds of go return time means the reflector is
    1cm deeper in the body
  147. Transducer is
    any device that converts one form of energy to another.
  148. Piezoleletric Effect is
    A property of certain materials to create a voltage when pressure is applied or when they are mechanically deformed.
  149. Piezoelectric materials
    • also called ferroelectric material
    • Man made-lead zirconate titanate
  150. PZT is also called
    ceramic, active element, or crystal
  151. Curie temperature or curie point
    if PZT is heated above this temperature, it loses its piefzoelectricity. the PZT is depolarized
  152. Sterilization
    The complete destruction of all living microorganisms by means of exposure to heat, chemical agents or radiation.
  153. Disinfection
    Refers to the application of a chemical agent to reduce or eliminate infectious organisms on an object, such as a transducer.
  154. The piezoeletric crystal. Also called the ceramic, PZT or crystal. It is 1/2
    wavelength thick
  155. DO not use a transducer with a
    cracked housing or with a frayed wire
  156. Short pulses create
    better images
  157. Bandwidth is
    • it is uncommon for a transducer to emit a sound beam with only a single pure frequency. Rather the pulse is more like a sound, "click" and contains a range of frequencies below and above the main frequency.
    • The bandwidth is the range of frequencies between the highest and lowest frequency emitted from the transducer.
  158. Compared to therapeutic transducers, imaging transducers are
    wide bandwidth or broadband
  159. The main frequency emitted by the transducer is called the
    center, resonant, primary or natural frequency
  160. quality factor is
    a unitless number
  161. Continuous wave transducer
    sound waves frequency equals the frequency of the voltage applied to the PZT by the machines electronics.
  162. Pulsed transducer
    the main or center frequency of the US for a pulsed txr is determined by 2 characteristics of the crystal
    • Thickness and
    • propagation speed
  163. When a PZT crystal is half as thick, the sounds frequency is
    twice as high
  164. Pulsed transducer, the thinner the active element the higher
    • the transducers resonant or natural frequency
    • (think of an hour glass)
  165. THe thickness of the PZT crystal equals
    1/2 of the wavelength of sound in the crystal.
  166. The thickness of the matching layer is
    1/4 of the wavelength of sound in the matching layer.
  167. When a transducer is covered with a sterile cover with gel on the inside, what can the transducer not come into contact with in order to create an image?
    talcum powder
  168. Beam width
    Narrow beams create
    better images
  169. Beam Width
    As sound travels, the width of the beam changes
    • starts out at exactly the same size as the transducer diameter
    • gets progressively narrower until it reaches its smallest diameter then it
    • diverges
  170. Focal Depth is
    the distance from the transducer face to the focus. also called the focal length or near zone length
  171. Near zone
    Fresnal zone
    The region or zone in between the transducer and the focus. sound beams converge in the near zone
  172. Far zone
    Fraunhofer zone
    The region or zone deeper than the focus, beyond the near field. Sound beams diverge in the far zone.
  173. All numerical values have $
    Corresponding units
  174. How many hertz is 3MHz?
    3,000,000
  175. How much bigger is a billion than a million
    1,000 times
  176. How many milliliters are contained in a jar filled with 5 liters of fluid?
    5,000
  177. How many liters are in 80ml of fluid?
    0.080
  178. Acoustic Propagation Properties
    the effects of the medium upon the sound wave
  179. Biologic effects is $
    the effects of the sound wave upon the biologic tissue
  180. Sound is $
    • Comprised of compressions (increase in pressure or density) and rarefractions (decrease in pressure or density)
    • *Sound must travel through a medium, cannot travel through a vacuum.
    • *Sound is a mechanical, longitudinal wave
    • *Sound travels in a straight line
  181. Acoustic Variables IDENTIFY $
    certain waves as sound waves.
  182. Three acoustic variables $
    • Pressure-concentration of force within an area force/area units Pascals
    • Density
    • Distance
  183. Transverse wave $
    Particles move in a perpendicular direction or to the direction of the wave
  184. Longitudinal wave $
    Particles move in the same direction as the wave
  185. Compressions are $
    Regions of higher density & pressure
  186. Rarefractions are $
    regions of lower density & pressure
  187. Period is
    the time required to complete a single cycle
  188. Frequency is
    the number of certain events that occur in a particular time duration
  189. Ultrasound is $
    a wave with a frequency exceeding 20,000 Hz (20KHz). This frequency is so high that it is not audible.
  190. Audible Sound $
    Heard by man, frequencies between 20Hz and 20,000Hz
  191. Infrasound $
    Sound with frequencies less than 20Hz
  192. Amplitude
    The difference between the average value and the maximum value of an acoustic variable. The variation of an acoustic variable.
  193. Units of Acoustic variables $
    • Pressure-Pascals
    • Density-Grams/cubic cm
    • Particles motion-cm, inches, units of distance
  194. Amplitude may be expressed in $
    Decibels dB
  195. Power
    The rate that work is performed, or the rate of energy transfer
  196. Relationship between power and amplitude $
    Power is proportional to the waves amplitude squared
  197. If the amplitude is doubled, the power is increased by a factor of $
    • quadrupled
    • 2x2=4
  198. Intensity is
    The concentration of energy in a sound beam
  199. Intensity is proportional to the amplitude of the wave $
    squared
  200. Wavelength $
    the length of distance of a single cycle
  201. In Soft tissue, sound with a frequency of 1MHz has a wavelength of $
    1.54mm
  202. In sound tissue, sound with a frequency of 2MHz has a wavelength of $
    0.77mm
  203. In soft tissue, divide 1.54mm by $
    frequency in MHz
  204. Propagation speed
    the rate that sound travels through a medium. Also called velocity or speed.
  205. Remember $ 1.54kms=1,540m/s=1.54mm/micros
    ,
  206. Remember $
    Lung (air)<<fat<soft tissue<<bone
  207. Tendon $
    about 1,850 speed
  208. Stiffness and Speed $
    Same direction
  209. Density and Speed $
    Opposite directions
  210. Bulk modulus is the same as $
    stiffness
  211. Interference
    when two waves overlap at the same location and the same instant in time, they combine into one new wave.
  212. Constructive interference $
    In-phase waves interfere constructively
  213. Destructive Interference $
    Out of phase waves interfere destructively
  214. Pulsed sound: In diagnostic ultrasound imaging, short burts, or pulses of acoustic energy are used to create $
    anatomic images
  215. Pulse duration $
    the time from the start of a pulse to the end of that pulse, the actual time, that pulse is on
  216. Remember: A pulse is a pulse, the talking time
    does not change
  217. as imaging depth increases $
    PR period increases
  218. as imaging decreases $
    PR period decreases
  219. Pulse Repetition Frequency
    is the number of pulses that occur in one second
  220. as imaging depth increases Pulse repetition Frequency
    Pulse repetition Frequency decreases
  221. Duty Factor is UNITLESS
    .
  222. Spatial Pulse Length is
    The length or distance that pulse occupies in space. the distance from the start to the end of one pulse.
  223. Intensity is
    the concentration of the power in a beam.
  224. units for intensity$
    watts/square cm, w/cm2
  225. Which intensity has the lowest point $$
    • SATA
    • Spatial average, temporal average
  226. which intensity is most important for thermal bioeffects$
    • SPTA
    • Spatial peak, temporal average
  227. Three commandments of Intensity$
    • Intensities may be reported in various ways with respect to time and space
    • Intensity is the key parameter with regard to bioefftects
    • The different intensities are important in the study of bioefftects. SPTA intensity is the most relevant intensity with respect to tissue heating.
  228. Logarithms is
    a novel way of rating numbers
  229. Decibels
    • a logarithmic scale
    • a relative scale- RATIO$
  230. What are the units of relative amplitude$
    dB
  231. Positive decibels means getting bigger. the intensity is
    increasing
  232. 10db means ten times bigger.
    The final intensity is 10 times bigger than the original intensity
  233. Negative decibels means getting smaller. The intensity is $
    decreasing.
  234. Attenuation is
    The decrease in intensity, power and amplitude of a sound wave as it travels. This is unrelated to speed.
  235. Attenuation in blood is equal to tha in$
    soft tissue
  236. Reflection is $
    occurs when propagating sound energy strikes a boundary between two media and some returns to the transducer.
  237. Specular Reflection$
    Reflection from a smooth reflector (mirror) are specular and return in one direction
  238. Specular reflectors also occur when the wavelength is$
    much smaller than the irregularities in the boundary.
  239. A red blood cell is $
    a Rayleigh scatterer
  240. Rayleigh Scattering is related to $
    frequency
  241. Impedance is calculated not $
    measured
  242. Range equation $ since the average speed of US in soft tissue (1.54km/sec) is known, the time of flight and distance that US travels in the body are
    directly related
  243. The time needed for a pulse to travel to and from the transducer and the reflector is called$
    go return time or time of flight or round trip time
  244. In soft tissue, every 13microsecond of go-return time means the reflector is $
    1cm deeper in the body.
  245. Transducers is$
    any device that converts one form of energy to another
  246. Piezoelectric effect $
    A property of certain materials to create a voltage when pressure is applied or when they are mechanically deformed
  247. Piezoelectric materials also called ferroelectric material $
    • Natural-quartz, Rochelle salts, tourmaline
    • man-made-barium titanate, lead metaniobate, lead titanate, lead zirconate tianate (PZT)
  248. PZT is also called$
    ceramic, active element, or crystal
  249. Sterilization$
    the complete destruction of all living microorganisms by means of exposure to heat, chemical agents, or radiation.
  250. Disinfection$
    refers to the application of chemical agent to reduce or eliminate infectious organisms on an object, such as a transducer
  251. Do not use a transducer with a $
    cracked housing or frayed wire
  252. Bandwidth is$
    the range of frequencies between the highest and the lowest frequency emitted from the transducer
  253. Continuous wave transducers <3
    sound waves frequency equals the frequency of the voltage applied to the pzt by the machine electronics.
  254. Pulsed transducers $
    The main or center frequency of the US for a pulsed txr is determined by 2 characteristics
    Thickness and Propagation speed
  255. when a transducer is covered with a sterile cover with gel on the inside, what can the transducer not come into contact with? $
    talcum powder
  256. Beam width RULE
    Narrow beams create better images
  257. Focus or Focal point is
    the location where the beam reaches its minimum diameter
  258. Focal depth $
    the distance from the transducer face to the focus. Also called focal length or near zone length
  259. Near zone (fresnal zone) is $
    the region or zone in between the transducer and the focus. Sound beams converge in the near zone.
  260. Far zone (Fraunhofer Zone)$
    the region or zone deeper than the focus, beyond the near field. Sound beams diverage in the far zone.
  261. Focal Zone $
    the region surrounding the focus where the beam is "sort of narrow" and the picture is relatively good.
  262. At the end of the near zone, the beam diameter is $
    1/2 the transducer diameter.
  263. At two near zone lengths, the beam diameter is $
    equal to the transducer diameter.
  264. Focal depth
    distance from the transducer to the focal point.
  265. Focal depth is determined by$
    transducer diameter and frequency
  266. Sound beam divergence
    describes the spread of the sound beam in the deep far zone.
  267. Sound beam divergence is determined by $
    transducer diameter and the frequency
  268. Diffraction$
    V-shaped wave also called a Huygens wavelet.
  269. Huygens Principle $
    This principle explains the hourglass shape of an imaging transducer sound beam
  270. Resolution
    the ability to image accurately
  271. Axial resolution
    the ability to distinguish two structures that are close to each other front to back, parallel to, or along the beams main axis
  272. Lateral Resolution $
    the minimum distance that two structures are separated by side to side or perpendicular to the sound beam that produces two distinct echoes.
  273. Lateral resolution is approximately equal to $
    beam diameter
  274. Focusing alters beam 3 ways
    • narrower waist in the US beam
    • shallower focus
    • smaller focal zone
  275. A-mode X-Axis-reflector depth $
    measured by
    pulses time of flight
  276. A-mode Y-axis-amplitude echo
    measured by
    echo strength
  277. B-mode z-axis $
    brightness of dot
  278. Mechanical scanning element shape$
    the crystal is circular and disc shaped like a coin
  279. Mechanical scanning Defective crystal $
    destroys entire image
  280. Phased Arrays$
    adjustable focus or muti-focus; achieved electronically
  281. Mechanical scanning image shape $
    fan or sector shaped, scan lines diverge or separate with depth.
  282. Transducer arrays$
    collection of active elements in a single transducer.
  283. Transducer array element $
    a single slab of PZT cut into separate pieces called elements.
  284. Transducer array-channel$
    combination of electronic circuitry, the wire and the element.
  285. Linear swtiched or sequntial arrays-Crystals $
    large transducers with multiple, approximately 200 elements arranged in a line.
  286. Linear switched-element shaped$
    each element in a linear switched array is rectangular
  287. Linear switched-steering$
    no steering, pulses sent down parallel lines. the scan lines are parallel and are equally shaped.
  288. Linear switched-image shaped $
    rectuangular image shape, no wider than the transducer.
  289. Phased arrays-meaning$
    adjustable focus or multi-focus; achieved electronically.
  290. Phased array$-Crystal, steering and focusing
    a collection of electric pulses is delivered to all of the transducers elements in various patterns.
    The patterns focus and steer the US beam during transmission, Thus, focus and steering are electroinic.
  291. Phased array-$ approximately 100-500 crstyals are in
    the transducer
  292. Annular phased arrays crystals$
    concentric rings The array looks like a bulls eye target.
  293. Annular phased array STEERING $
    Steering is performed mechanically. HINT this is unlike other phased array transducers
  294. Dynamic Aperture$
    a form of electronic receive, electronic focusing.
  295. Two dimensional arrays creates$
    3d ultrasounds images. 3-D imaging measures volumes (such as a cyst)
  296. Real time imaging is $
    The production of a motion picture
  297. Temporal Resolution $
    • The ability to accurately locate moving structures at any particular instant in time
    • ex. How good is my movie?
  298. Temporal Resolution is determined by:$
    Temporal resolution depends only upon frame rate. More images per second improves temporal resolution
  299. what does not decrease temporal resolution $
    narrower sector
  300. a sonographer, using a phased array ultrasound system, turns off the multi-focus feature. What is the most likely consequence of this action?$
    the temporal resolution improves
  301. pulser $
    creates the firing pattern for phased array systems. This is called the beam former
  302. THE AIUM SUGGESTS $
    • Do not perform studies without reason
    • Do not prolong studies without reason
    • Minimize exposure time
    • Use minimum output power and highest receiver gain required to produce optimal image. ALARA principle
  303. Mechanical Index is higher (more likely to produce cavitation) with
    • higher pressure -beams and
    • lower frequency -sound
  304. A structure that produces more echoes than surrounding soft tissue is said to be
    Hyperechoic
  305. The piezoelectric effect was discovered by
    Pierre and jacques curie
  306. a statement that describes an ultrasound
    Display of physical interaction of sound energy and matter
  307. Unit measure of frequency is
    Hertz
  308. Red blood cells are an example of
    non-specular reflector
  309. The angle of refraction is described by
    Snells Law
  310. What is reflection in multiple directions from a reflector that is small relative to the wavelength.
    Rayleigh scattering
  311. Receiver demodulation can not be controlled by the sonographer
    TRUE
  312. Reflection at at tissue interface depends primarily on
    impedance
  313. Azimuthal resolution is also known as
    lateral resolution
  314. Intensity of the ultrasound beam is proportional to the square root of the acoustic pressure
    FALSE
  315. Aliasing is not a problem in color flow imaging
    false
  316. Density is an acoustic variable
    true
  317. Period is
    the time it takes to complete a single cycle
  318. Diffraction is the
    spreading of an ultrasound beam
  319. Annular array transducers steer the beam
    Mechanically
  320. a bit is the smallest part of a "digital word"
    TRUE
  321. Velocity times density equals
    impedance
  322. Aliasing artifacts are unique to
    Pulsed doppler
  323. Compensation is $
    used to create image of uniform brightness from top to bottom
  324. Compression $
    reducing the total range, the smallest to largest signal
  325. purpse of compression is$
    to allow us to see all gray shades
  326. Demodulation$
    changes the signals form to one more suitable for TV display
  327. we use REJECT to$
    eliminate low level noise in our images
  328. Output Power$
    when the image is too bright due to high output power, the lateral and longitudinal resolution degrade
  329. Harmonics$
    are multiples of the transducer frequency
  330. Harmonics are created in the TISSUES, not
    in the transducer or receiver
  331. Sound travels slightly faster in regions of$
    COMPRESSION
  332. Sound travels slightly slower in regions of
    rarefraction (lower pressure)
  333. Bistable
    only 2 choices:white or black, on or off, high contrast narrow dynamic range, poor contrast resolution
  334. Gray scale-
    many levels of brightness (white, light gray, medium gray, dark gray, black etc.
  335. Controls-BRIGHTNESS
    determines the brillance of the signals displayed
  336. Controls-Contrast
    determines the range of brilliances that are displayed. Bistable images are high contrast
  337. Pixel$
    The smallest element of a digital picture
  338. Pixel density$
    The more pixels per inch, the greater the detail in the image. The detail is called spatial or detail resolution
  339. The best spatial resolution is obtained with more elements or pixels in the matrix.
    d
  340. Spatial resolution on a digital display is determined by
    the pixels density (the number of pixels per inch)
  341. Postprocessing$
    is performed on frozen images
  342. Read Magnification$
    Occurs after the image is in the scan converter. POST PROCESSING.
  343. Write magnification$
    occurs upon azquisition of the ultrasound reflections. Preprocessing
  344. Longitudinal waves are
    parallel to the axis of the wave propagation
  345. Wavelength has the greates effect on
    axial resolution
  346. What is necessary to calculate distance to a reflector?
    propagation speed and round trip time
  347. In a cathode ray tube display device the electron beam is steered by
    deflection plates
  348. shadowing artifacts are caused
    by differences in attenuation
  349. Mirror images are seen near the
    diaphragm
  350. Edge enchancement$
    Most useful to emphasize the boundary between different tissues
  351. Dynamic range$
    the ratio of the largest to the smallest signal strength that each component processes
  352. PACS$
    Picture Archiving and communications System
  353. Laminar flow may have
    parabolic or plug patterns
  354. small regions of laminar flow will have$
    similar velocities and narrow doppler spectra
  355. Turbulent flow
    small regions of turbulent flow have vastly different velocities (doppler spectral broadening)
  356. Energy
    blood flows when the total fluid energy at one location differs from the total fluid energy at another location. this is called an energy gradient.
  357. Velocity changes
    at a stenosis
  358. Anemia reduces $
    viscosity because the blood is thinner
  359. Stenosis cause$
    • changes in flow direction
    • increased velocity in the stenosis, highest velocity at the point of maximum narrowing
    • turbulence at exit
    • pressure gradient across the stenosis
    • arterial flow loses its pulsatile nature and becomes more continous
  360. Doppler shift$ or doppler frequency
    the change in variation, in the frequency of sound as a result of motion between the sound source and the receiver. Greater velocities create greater doppler shifts.
  361. Doppler measures
    frequency shift, not amplitude
  362. Typical values for doppler shift
    20HZ-20 kHz
  363. flow towards transducers increased
    frequency
  364. flow away from transducers
    decreased frequency
  365. Doppler measures$
    Velocity not speed
  366. Non-coherent processing used with
    uni-directional doppler
  367. Phase quadrate processing used in
    bidirectional doppler
  368. Continuous wave doppler
    Number of crystals
    Two crystals in the transducer
  369. Advantage of Continuous wave doppler
    able to measure very high velocities accurately
  370. Pulsed wave doppler $
    Number of crystals
    one, crystal, alternates between sending and receiving
  371. Pulsed wave doppler$ Advantage
    Echoes arise only from the area of interrogation, the sample volume or gate. we adjust the receive gate
  372. Eliminating aliasing "improves $
    the ability to measure the maximum veloctiy with doppler
  373. The horizontal axis or X-axis of a doppler spectrum is
    time
  374. The vertical or Y-axis of a doppler spectrum is
    Doppler shift or Velocity
  375. Gray shades on a doppler spectrum are related to
    • 1. Amplitude of the reflected signal or
    • 2. number of red blood cells creating the reflection
  376. Color flow doppler is$
    • pulsed ultrasound technique and is subject to
    • range resolution or specificity
    • aliasing
  377. Color doppler reports
    average velicities also called mean velocities
  378. color jet size is most affected by
    color dopper gain setting
  379. Color Power doppler Advantages
    Increased sensitivity to the low flows, e.g. venous flow, flow in small vessels
  380. Hyperechoic$
    portions of an image that are brighter than surrounding tissues, or tissues that appear brighter than normal.
  381. Shadowing
    There are occasions when the US beam is unable to pass through a structure because the structure has a higher than usual attenutaion. When this occurs, any structures that lie deeper than the initial structure are not imaged or displayed. This is a shadow-aechoic or hypoechoic
  382. Edge shadowing or shadowing by refraction
    refraction at the edge of a circular structure can also create an artifact. This is called shadowing by refraction or edge shadow
  383. Enhancement
    Hyperechoic occurs when
    the medium through which the sound travels has a lower attenutation rate than soft tissue
  384. Mirror image $
    sound may bounce off of a strong reflector, called a mirror, in its path and be directed.
  385. Ultrasound$ systems assume that sound travels directly to a reflector and back to the transducer$
  386. Speed errors appear as a $
    step off, split or cut
  387. Grating lobe artifact can be reduced or cured by dividing each element into even smaller, miniature pieces. This is called
    Subdicing
  388. Lobe artifacts degrade
    Lateral resolution
  389. Speckle
    • grainy appearance not directly from reflections from tissues.
    • Created by interfence effects of scattered sound, both constructive and destructive, from the many tissue reflectors
  390. Artifacts are created when$
    • the sound beam is larger than the reflector
    • "small sound is good"

What would you like to do?

Home > Flashcards > Print Preview