Imaging with Ultrasounds
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Questions and Answers

What determines the length of an ultrasound pulse?

  • The frequency of the transducer
  • The size of the piezoelectric crystal
  • The number of alternating voltage changes applied to the transducer (correct)
  • The bandwidth of the transducer

    • What happens to the transducer when the polarity of the voltage changes?

  • It changes in thickness (correct)
  • It stops producing ultrasound waves
  • It generates electric potentials
  • It remains the same size

    • What is the wavelength of the emitted ultrasound a function of?

  • The size of the transducer
  • The crystal size (correct)
  • The voltage applied to the transducer
  • The frequency of the transducer

    • What happens to the pressure changes caused by the returning ultrasound echoes?

    <p>They are converted back into electrical energy signals</p> Signup and view all the answers

    What type of material are transducers typically made of?

    <p>Synthetic ceramic (piezoceramic)</p> Signup and view all the answers

    What is the basis of measuring distance in diagnostic imaging?

    <p>The time from pulse creation to reception</p> Signup and view all the answers

    What is the average speed of sound in soft tissue?

    <p>1540 m/s</p> Signup and view all the answers

    What is the rule that applies when sound travels through soft tissue?

    <p>The 13 μs rule</p> Signup and view all the answers

    What is the formula to calculate the depth of a reflector?

    <p>𝒅𝒆𝒑𝒕𝒉 𝒎𝒎 = 𝟏.𝟒𝟒 ×𝒈𝒐 − 𝒓𝒆𝒕𝒖𝒓𝒏 𝒕𝒊𝒎𝒆 (𝝁𝒔)</p> Signup and view all the answers

    How far from the transducer are the interfaces in the given class example?

    <p>4 cm and 8 cm</p> Signup and view all the answers

    What is the main reason for differences in acoustic impedance in different tissues?

    <p>Variations in density and compressibility of different tissues</p> Signup and view all the answers

    What determines the brightness of the image in ultrasound imaging?

    <p>The echo magnitude</p> Signup and view all the answers

    What is the method used to determine the reflector's depth in ultrasound imaging?

    <p>Measuring the time-of-flight of the pulse</p> Signup and view all the answers

    What is the term for the elapsed time from pulse creation to pulse reception in ultrasound imaging?

    <p>Time-of-flight</p> Signup and view all the answers

    What is the purpose of the transducer in ultrasound imaging?

    <p>To transmit and receive ultrasound waves</p> Signup and view all the answers

    What property do piezoelectric crystals have?

    <p>Changing thickness with applied electric voltage</p> Signup and view all the answers

    What is the result of an alternating voltage applied to a piezoelectric crystal?

    <p>The crystal generates a sound wave</p> Signup and view all the answers

    What determines the resonant frequency of an ultrasound transducer?

    <p>Thickness and acoustic velocity of the piezoelectric crystal</p> Signup and view all the answers

    What happens when a sound wave causes a piezoelectric crystal to vibrate?

    <p>An electric voltage is generated</p> Signup and view all the answers

    What is the main function of an ultrasound transducer?

    <p>To convert sound waves to electric signals</p> Signup and view all the answers

    What is the process of creating piezoelectric properties in a material called?

    <p>Polarization</p> Signup and view all the answers

    What is the temperature at which PZT is polarized called?

    <p>Curie temperature</p> Signup and view all the answers

    What happens to the piezoelectric properties of PZT when it is heated above the Curie temperature?

    <p>They are destroyed</p> Signup and view all the answers

    How does the speed of sound in PZT affect the frequency of the sound created?

    <p>Faster speed of sound results in higher frequency</p> Signup and view all the answers

    What is the range of the speed of sound in most piezoelectric materials?

    <p>4-6 mm/μs</p> Signup and view all the answers

    How does the thickness of the PZT crystal affect the frequency of the sound created?

    <p>Thinner crystals result in higher frequency</p> Signup and view all the answers

    What is the mathematical relationship between frequency and PZT thickness?

    <p>f = 1/(2 × t)</p> Signup and view all the answers

    What range of thicknesses is typically used for PZT crystals in diagnostic imaging transducers?

    <p>0.2-0.1 mm</p> Signup and view all the answers

    Why do transducer manufacturers create PZT crystals of varying thickness?

    <p>To achieve different frequencies</p> Signup and view all the answers

    What is the purpose of controlling the thickness of PZT crystals in transducer design?

    <p>To control the frequency of the sound created</p> Signup and view all the answers

    What is the function of the transducer in ultrasound imaging?

    <p>To convert electrical energy into acoustic energy and vice versa</p> Signup and view all the answers

    What determines the width of the organ at a given point?

    <p>The difference between the distances to the front and rear interfaces of the organ</p> Signup and view all the answers

    What is the purpose of applying a high-amplitude voltage to the transducer?

    <p>To transmit the ultrasound pulse into the body</p> Signup and view all the answers

    What determines the field of view of a transducer?

    <p>The size and shape of its footprint</p> Signup and view all the answers

    What is the dimension of the organ along the ultrasound pulse's path?

    <p>3.1 cm</p> Signup and view all the answers

    What is the formula to calculate the distance traveled by the ultrasound pulse?

    <p>D = v × t</p> Signup and view all the answers

    What is the purpose of mapping the echo magnitude in an ultrasound image?

    <p>To display the echo magnitude as brightness</p> Signup and view all the answers

    What is the relationship between the time interval and the distance traveled by the ultrasound pulse?

    <p>The distance is directly proportional to the time interval</p> Signup and view all the answers

    What is the total distance traveled by the pulse if the go-return time is 26 μs?

    <p>3 cm</p> Signup and view all the answers

    What does the operator change when changing the image depth?

    <p>Spatial pulse length</p> Signup and view all the answers

    What is the effect of a smaller transducer diameter on the near field?

    <p>It shortens the near field and increases divergence in the far field.</p> Signup and view all the answers

    What is the effect of increasing the transducer diameter on the focal depth?

    <p>It increases the focal depth</p> Signup and view all the answers

    Why do higher frequency ultrasound waves produce better resolution of small structures?

    <p>They have a longer near field and less divergence in the far field.</p> Signup and view all the answers

    What is the trade-off when increasing the frequency in ultrasound imaging?

    <p>Improved axial resolution at the expense of reduced depth penetration</p> Signup and view all the answers

    What is the process called when an array of piezoelectric elements electronically steers and focuses acoustic pulses through the plane or volume being imaged?

    <p>Beamforming</p> Signup and view all the answers

    Why do transducer manufacturers create small diameter, high frequency crystals?

    <p>To displace the focus shallower despite the rule of physics</p> Signup and view all the answers

    What is the purpose of beamsteering in phased array transducers?

    <p>To focus the ultrasonic beam on a given point</p> Signup and view all the answers

    What is the mathematical relationship between diameter, frequency, and focal depth?

    <p>Diameter^2 × Frequency = Focal Depth</p> Signup and view all the answers

    What is the advantage of using phased array transducers over unfocused transducers?

    <p>Phased array transducers produce a narrower beam.</p> Signup and view all the answers

    What is the difference between mechanical focus and unfocused transducers?

    <p>Mechanical focus has a shorter focal length</p> Signup and view all the answers

    What is the beam diameter at the focus?

    <p>Narrower than the transducer diameter</p> Signup and view all the answers

    What happens to the sound beam in the far zone?

    <p>It starts to diverge or widen</p> Signup and view all the answers

    How are all diagnostic transducers focused?

    <p>Using a curved piezo electric crystal or an acoustic lens</p> Signup and view all the answers

    What is the distance from the transducer to the focus called?

    <p>Focal length or near zone length</p> Signup and view all the answers

    What happens to the beam diameter at a depth that is twice the focal length?

    <p>It becomes wider</p> Signup and view all the answers

    What is the primary reason for the attenuation of ultrasound signals with increasing frequency?

    <p>Increased absorption by tissues</p> Signup and view all the answers

    What is the purpose of time gain compensation (TGC) in ultrasound imaging?

    <p>To amplify echoes from deeper tissues</p> Signup and view all the answers

    How does the frequency of the ultrasound wave affect the resolution of the image?

    <p>Higher frequency waves provide better resolution but lower penetration</p> Signup and view all the answers

    What is the primary function of the receiver in ultrasound imaging?

    <p>To compress and remap returning data into a dynamic range</p> Signup and view all the answers

    What determines the shape of the ultrasound beam produced by the transducer?

    <p>The diameter of the transducer</p> Signup and view all the answers

    What is the advantage of using higher frequencies in ultrasound imaging?

    <p>To improve axial resolution</p> Signup and view all the answers

    What determines the axial resolution in ultrasound imaging?

    <p>The pulse length and number of cycles in the pulse</p> Signup and view all the answers

    What is the effect of increasing the transducer frequency on the axial resolution?

    <p>It improves the axial resolution</p> Signup and view all the answers

    Why are higher frequencies used in breast ultrasound imaging compared to abdominal imaging?

    <p>To improve axial resolution for shallower regions</p> Signup and view all the answers

    What is the advantage of introducing the transducer into the body near the tissues to be imaged?

    <p>To improve the axial resolution</p> Signup and view all the answers

    Why does a higher frequency pulse produce better lateral resolution in the far field?

    <p>Higher frequency pulses are narrower and diverge less in the far field</p> Signup and view all the answers

    What is the effect of a larger transducer diameter on the near field?

    <p>The near field is longer</p> Signup and view all the answers

    What is the advantage of phased array transducers over unfocused transducers?

    <p>Improved beam steering</p> Signup and view all the answers

    What is the mathematical relationship between diameter, frequency, and focal depth?

    <p>Focal depth is directly proportional to diameter and frequency</p> Signup and view all the answers

    What is the purpose of beamsteering in phased array transducers?

    <p>To steer the beam electronically</p> Signup and view all the answers

    What is the effect of increasing the frequency on image quality?

    <p>Image quality increases</p> Signup and view all the answers

    What is the advantage of using mechanical focus over unfocused transducers?

    <p>Improved lateral resolution</p> Signup and view all the answers

    What is the relationship between transducer diameter and near field length?

    <p>Near field length is directly proportional to transducer diameter</p> Signup and view all the answers

    What determines the field of view of a transducer?

    <p>Transducer diameter</p> Signup and view all the answers

    What is the purpose of focusing the ultrasound beam?

    <p>To improve lateral resolution</p> Signup and view all the answers

    What is the effect of a larger transducer diameter on the ultrasound beam?

    <p>It decreases the divergence of the beam</p> Signup and view all the answers

    Which of the following probes creates a beam with the least divergence?

    <p>6 mm diameter, 8 MHz</p> Signup and view all the answers

    What is the primary method of focus in ultrasound imaging?

    <p>Mechanical focus</p> Signup and view all the answers

    What is the mathematical relationship between the frequency and the diameter of the transducer in determining the beam's focal depth?

    <p>Focal depth is directly proportional to the diameter and inversely proportional to the frequency</p> Signup and view all the answers

    What is the advantage of using a higher frequency transducer in ultrasound imaging?

    <p>It decreases the beam's divergence</p> Signup and view all the answers

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