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ARDMS SPI STUDY GUIDE QUESTIONS
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In soft tissue, if the frequency of a wave is increased the Propagation Speed (PS) will... ✔✔Remain the Same because stiffness and density affect Propagation Speed.
What is the audible range? ✔✔ 20 - 20,000Hz
20,000Hz=Ultrasound
Frequency is measured in ✔✔Hertz (Hz)
is
Cycles per Second
Not affected by sonographer
Increase Frequency; Decrease Depth
A period is the length of time it takes for ✔✔one complete wavelength to pass a fixed point
PRP is determined by ✔✔Transmit time and receive time.
Period is measured in ✔✔Time (μs)
When the sonographer changes the imaging depth what parameters are changed? ✔✔PRP, PRF, Duty Factor
What is duty factor? ✔✔The percentage or fraction of time that the system is transmitting a pulse (Time Sound is ON or ON-Time).
Propagation Speed in SOFT TISSUE ✔✔1.54 mm/μs
(1540 m/sec)
Unit of measurement for Pulse Duration, Duty Factor, PRP, and Period ✔✔Time, (μs)
Pulse duration is determined by ✔✔Sound Source Only
(Directly Proportional means that increased SPL will increase both the number of cycles in the pulse and the wavelength if increased).
Spatial pulse length is inversely proportional to ✔✔Frequency (MHz)
(Inversely Proportional means that increased SPL will lower frequency. This is because axial resolution is better with lower frequency)
Pulse Duration (PD) ✔✔The actual time from the start of a pulse to the end of that pulse; a single transmit, talking, or "on" time.
Time the pulse is on typically measured in (ms).
Pulse Length ✔✔The distance of the pulse start to end or the
duration or length of a single pulse
Pulse Length is typically measured in (mm).
the ability of an object to resist compression and relates to the hardness of a medium? ✔✔Stiffness.
Think:
↑ Stiffness ↑ Speed
↓ Density ↑ Speed
An increase in pulse repetition frequency would lead to: ✔✔Increasing pulse repetition frequency, increases duty factor.
↑ PRF ↑ Duty Factor
Which of the following would have the highest propagation speed? ✔✔Bone has the highest propagation speed, at 2000-4000 m/s.
What has the lowest propagation speed? ✔✔air technically has the lowest propagation speed at 300 m/s
Which has the Slowest Propagation Speed?
Water
Soft Tissue
Bone
The typical range of frequency for diagnostic ultrasound imaging is ✔✔1-20 Mhz is the typical range of frequency for diagnostic ultrasound imaging.
The attentuation coefficient in soft tissue is equal to: ✔✔Attentuation Coeffcient = 1/2 (one half of the frequency in soft tissue)
The attentuation coeffcient (in dB/cm) is the rate at which sound is attentuated per unit depth.
Micro is denoted as: ✔✔Micro is denoted as millionth (μ)
What is described as the distance over which one cycle occurs? ✔✔Wavelength is distance over which one cycle occurs, or the distance from the beginning of one cycle to the end of the same cycle.
Remember, it asks for distance over which one cycle occurs.
Stiffness and propagation speed are ✔✔Directly Related
Also remember:
↑ Stiffness ↑ Speed
↓ Density ↑ Speed
Areas of high pressure and density are referred to as: ✔✔Compressions
What type of wave is sound? ✔✔Mechanical and Longitudinal Wave
The frequency ranges for ultrasound are: ✔✔Ultrasound frequency is 20 to 20,000 Hz
The speed of sound in soft tissue is ✔✔Speed of sound in soft tissue is 1540 m/s
Which transducer fires the elements in groups? ✔✔Linear sequenced array fires the elements in groups
The units for wavelength is ✔✔Wavelength units are (Millimeters)
Enhancement is caused by ✔✔Weakly attenuating structures
Ultrasound pulses contain a range of frequencies called ✔✔bandwidth
How is time related to frequency ✔✔inversely
What describes the percentage of time that sound is on? ✔✔Duty factor is the percentage of time the sound is being transmitted
A 3 dB gain would indicate an increase in intensity by: ✔✔Two Times
3 dB results in doubling of intensity (or power)
The intensity of the ultraosund beam is usually greater at the focal zone because of ✔✔the smaller beam diameter
Attenuation denotes ✔✔Progressive weakening of the sound beam as it travels
Which of the following has the lowest intensity ✔✔SATA is the lowest of the intensities
What is the definition of the beam uniformity ratio? ✔✔Beam Uniformity Ratio =
Spatial peak / Spatial average
Continuous wave Doppler has a duty factor of ✔✔100%
CW Doppler is always transmitting sound making it's duty factor 100%
The spatial pulse length is defined as: ✔✔the product of the wavelength and the number of cycles in a pulse?
SPL = wavelength x cycles
What term and philosophy relates the amount of exposure time for the sonographer and patient during a diagnostic ultrasound examination? ✔✔ALARA - As Low As Reasonably Achievable
What term is defined as the body's pathologic response to illness, trauma or severe physiologic or emotional stress? ✔✔Shock
What results in the most attenuation? ✔✔most attenuation occurs at the high frequency and long distance.
Which media has the greatest attenuation and the slowest speed? ✔✔Air
Air > Bone & Lung > Soft Tissue > Water
What type of wave is sound? ✔✔Mechanical and Longitudinal wave
The speed of sound in soft tissue: ✔✔1540 m/s
The unit for wavelength: ✔✔Distance (mm)
Enhancement is caused by: ✔✔weakly attenuating structures
Lowest attenuating to highest attenuation ✔✔Fat-Muscle-Bone-Air
List propagation speed from lowest to highest ✔✔Air-Fat-Muscle-Bone
Which of these media has the lowest attenuation and the greatest speed?
bone
tendon
lung
fat
air ✔✔Bone
Air > Bone & Lung > Soft Tissue > Water
Bone is more stiff than air
(remember ↑ stiffness, ↑ speed)
What describes the physics of refraction mathematically? ✔✔Snell's Law
What is a reflection arising from a rough boundary? ✔✔Non-specular
Along with image depth, which of the following also determines the frame rate? ✔✔Image depth and the number of lines per frame determines the frame rate.
Which type of resolution is an accurate representation of moving structures? ✔✔Temporal resolution, also known as frame rate, is the ability to display moving structures in real time.
What type of transducer that utilizes elements arranged in a concentric pattern? ✔✔The annular array transducer ultilizes elements arranged in concentric rings
What transducer would be considered an advantage of linear array over a phased array transducer? ✔✔The linear array has a wider near field of view compared to a phased array transducer
Mechanical Transducers: ✔✔Have moving parts
Uses a motor to steer the beam
Most transducers are no longer mechanical May be focused with a lens or phased focuses
Along with crystal diameter, the divergence in the far field is also determined by... ✔✔Frequency
and crystal diameter determines the divergence in the far field
What would cause an increase in frame rate? ✔✔Decreasing the imaging depthwould increase the frame rate
When you decrease the imaging depth it can work faster (increase frame rate) because it doesn't have to go as deep.
The diameter of the beam in the Fresnel zone/near zone does what? ✔✔Decreases
Which resolution is best in the clinical imaging? ✔✔Axial resolution is best in imaging
will increase the near zone length? ✔✔A large crystal diameter with high frequency would increase the near zone length
What will decrease beam divergence in the far field? ✔✔A large crystal diameter and high frequency would decrease the beam divergence in the far field
The ____ of a wave is the number of wavelengths that pass a fixed point in a second. ✔✔frequency
Frequency is the number of wavelengths that pass a fixed point in a second
A sound wave is traveling in the body and propagates from muscle to air. What percentage of the sound wave is most likely reflected at the muscle-air boundary? ✔✔75%
Which of the following lists is in decreasing order? ✔✔Mega, kilo, deca, milli, nano
The conversion of sound energy to heat ✔✔Absorption
Acoustic Speckle ✔✔the interference pattern caused by scatterers that produces the granular appearance of tissue on a sonographic image
Acoustic Variables ✔✔changes that occur within a medium as a result of sound traveling through that medium
Amplitude ✔✔The maximum or minimum deviation of an acoustic variable from the average value of that variable; the strength of the reflector
Attenuation ✔✔A decrease in the amplitude and intensity of the sound beam as sound travels through tissue.
Attenuation Coefficient ✔✔The rate at which sound is attenuated per unit depth
Axial Resolution ✔✔The ability to accurately identify reflectors that are arranged parallel to the ultrasound beam
Backscatter ✔✔Scattered sound waves that make their way back to the transducer and produce an image on the display
Beam Uniformity Ratio ✔✔The ratio of the center intensity to the average spatial intensity; also referred to as the SP/SA factor or beam uniformity coefficient
Capacitive Micromachined Ultrasound Transducers ✔✔Technology used to create comparable transducer technology to piezoelectric materials
