80 Questions
What determines the length of an ultrasound pulse?
The number of alternating voltage changes applied to the transducer
What happens to the transducer when the polarity of the voltage changes?
It changes in thickness
What is the wavelength of the emitted ultrasound a function of?
The crystal size
What happens to the pressure changes caused by the returning ultrasound echoes?
They are converted back into electrical energy signals
What type of material are transducers typically made of?
Synthetic ceramic (piezoceramic)
What is the basis of measuring distance in diagnostic imaging?
The time from pulse creation to reception
What is the average speed of sound in soft tissue?
1540 m/s
What is the rule that applies when sound travels through soft tissue?
The 13 μs rule
What is the formula to calculate the depth of a reflector?
𝒅𝒆𝒑𝒕𝒉 𝒎𝒎 = 𝟏.𝟒𝟒 ×𝒈𝒐 − 𝒓𝒆𝒕𝒖𝒓𝒏 𝒕𝒊𝒎𝒆 (𝝁𝒔)
How far from the transducer are the interfaces in the given class example?
4 cm and 8 cm
What is the main reason for differences in acoustic impedance in different tissues?
Variations in density and compressibility of different tissues
What determines the brightness of the image in ultrasound imaging?
The echo magnitude
What is the method used to determine the reflector's depth in ultrasound imaging?
Measuring the time-of-flight of the pulse
What is the term for the elapsed time from pulse creation to pulse reception in ultrasound imaging?
Time-of-flight
What is the purpose of the transducer in ultrasound imaging?
To transmit and receive ultrasound waves
What property do piezoelectric crystals have?
Changing thickness with applied electric voltage
What is the result of an alternating voltage applied to a piezoelectric crystal?
The crystal generates a sound wave
What determines the resonant frequency of an ultrasound transducer?
Thickness and acoustic velocity of the piezoelectric crystal
What happens when a sound wave causes a piezoelectric crystal to vibrate?
An electric voltage is generated
What is the main function of an ultrasound transducer?
To convert sound waves to electric signals
What is the process of creating piezoelectric properties in a material called?
Polarization
What is the temperature at which PZT is polarized called?
Curie temperature
What happens to the piezoelectric properties of PZT when it is heated above the Curie temperature?
They are destroyed
How does the speed of sound in PZT affect the frequency of the sound created?
Faster speed of sound results in higher frequency
What is the range of the speed of sound in most piezoelectric materials?
4-6 mm/μs
How does the thickness of the PZT crystal affect the frequency of the sound created?
Thinner crystals result in higher frequency
What is the mathematical relationship between frequency and PZT thickness?
f = 1/(2 × t)
What range of thicknesses is typically used for PZT crystals in diagnostic imaging transducers?
0.2-0.1 mm
Why do transducer manufacturers create PZT crystals of varying thickness?
To achieve different frequencies
What is the purpose of controlling the thickness of PZT crystals in transducer design?
To control the frequency of the sound created
What is the function of the transducer in ultrasound imaging?
To convert electrical energy into acoustic energy and vice versa
What determines the width of the organ at a given point?
The difference between the distances to the front and rear interfaces of the organ
What is the purpose of applying a high-amplitude voltage to the transducer?
To transmit the ultrasound pulse into the body
What determines the field of view of a transducer?
The size and shape of its footprint
What is the dimension of the organ along the ultrasound pulse's path?
3.1 cm
What is the formula to calculate the distance traveled by the ultrasound pulse?
D = v × t
What is the purpose of mapping the echo magnitude in an ultrasound image?
To display the echo magnitude as brightness
What is the relationship between the time interval and the distance traveled by the ultrasound pulse?
The distance is directly proportional to the time interval
What is the total distance traveled by the pulse if the go-return time is 26 μs?
3 cm
What does the operator change when changing the image depth?
Spatial pulse length
What is the effect of a smaller transducer diameter on the near field?
It shortens the near field and increases divergence in the far field.
What is the effect of increasing the transducer diameter on the focal depth?
It increases the focal depth
Why do higher frequency ultrasound waves produce better resolution of small structures?
They have a longer near field and less divergence in the far field.
What is the trade-off when increasing the frequency in ultrasound imaging?
Improved axial resolution at the expense of reduced depth penetration
What is the process called when an array of piezoelectric elements electronically steers and focuses acoustic pulses through the plane or volume being imaged?
Beamforming
Why do transducer manufacturers create small diameter, high frequency crystals?
To displace the focus shallower despite the rule of physics
What is the purpose of beamsteering in phased array transducers?
To focus the ultrasonic beam on a given point
What is the mathematical relationship between diameter, frequency, and focal depth?
Diameter^2 × Frequency = Focal Depth
What is the advantage of using phased array transducers over unfocused transducers?
Phased array transducers produce a narrower beam.
What is the difference between mechanical focus and unfocused transducers?
Mechanical focus has a shorter focal length
What is the beam diameter at the focus?
Narrower than the transducer diameter
What happens to the sound beam in the far zone?
It starts to diverge or widen
How are all diagnostic transducers focused?
Using a curved piezo electric crystal or an acoustic lens
What is the distance from the transducer to the focus called?
Focal length or near zone length
What happens to the beam diameter at a depth that is twice the focal length?
It becomes wider
What is the primary reason for the attenuation of ultrasound signals with increasing frequency?
Increased absorption by tissues
What is the purpose of time gain compensation (TGC) in ultrasound imaging?
To amplify echoes from deeper tissues
How does the frequency of the ultrasound wave affect the resolution of the image?
Higher frequency waves provide better resolution but lower penetration
What is the primary function of the receiver in ultrasound imaging?
To compress and remap returning data into a dynamic range
What determines the shape of the ultrasound beam produced by the transducer?
The diameter of the transducer
What is the advantage of using higher frequencies in ultrasound imaging?
To improve axial resolution
What determines the axial resolution in ultrasound imaging?
The pulse length and number of cycles in the pulse
What is the effect of increasing the transducer frequency on the axial resolution?
It improves the axial resolution
Why are higher frequencies used in breast ultrasound imaging compared to abdominal imaging?
To improve axial resolution for shallower regions
What is the advantage of introducing the transducer into the body near the tissues to be imaged?
To improve the axial resolution
Why does a higher frequency pulse produce better lateral resolution in the far field?
Higher frequency pulses are narrower and diverge less in the far field
What is the effect of a larger transducer diameter on the near field?
The near field is longer
What is the advantage of phased array transducers over unfocused transducers?
Improved beam steering
What is the mathematical relationship between diameter, frequency, and focal depth?
Focal depth is directly proportional to diameter and frequency
What is the purpose of beamsteering in phased array transducers?
To steer the beam electronically
What is the effect of increasing the frequency on image quality?
Image quality increases
What is the advantage of using mechanical focus over unfocused transducers?
Improved lateral resolution
What is the relationship between transducer diameter and near field length?
Near field length is directly proportional to transducer diameter
What determines the field of view of a transducer?
Transducer diameter
What is the purpose of focusing the ultrasound beam?
To improve lateral resolution
What is the effect of a larger transducer diameter on the ultrasound beam?
It decreases the divergence of the beam
Which of the following probes creates a beam with the least divergence?
6 mm diameter, 8 MHz
What is the primary method of focus in ultrasound imaging?
Mechanical focus
What is the mathematical relationship between the frequency and the diameter of the transducer in determining the beam's focal depth?
Focal depth is directly proportional to the diameter and inversely proportional to the frequency
What is the advantage of using a higher frequency transducer in ultrasound imaging?
It decreases the beam's divergence
Understand the basics of ultrasound imaging, including the production of ultrasound beams, detection of echoes with a transducer, and how images are produced. Learn about the role of acoustic impedance in displaying tissue differences.
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