Chap 5 Lvl 2 Exam Study Guide Flashcards
What is another name for the Pedof transducer?
Pencil probe or blind Doppler probe
The Pedof is a type of transducer commonly used in medical imaging.
What type of transducer is the Pedof?
Single Element, Blind, Doppler Only Transducer
This indicates its specific design and functionality.
What are the key characteristics of the Pedof transducer?
Simple round design, blind functionality, Doppler only
These features make it distinct in its applications.
What is a key advantage of Pedof transducers in Doppler?
Usually extremely sensitive in Doppler since designed specifically
This sensitivity is crucial for accurate measurements in Doppler ultrasound applications.
What is a physical characteristic of Pedof transducers?
Small footprint allowing for insonation in smaller areas such as between ribs and suprasternal notch
This feature is particularly beneficial for accessing challenging anatomical regions.
What is the speed of sound in tissue?
High enough for many beams to be transmitted and received quickly
This rapid transmission allows for real-time image generation.
What is repeated continuously until the desired region of the patient is scanned?
The process of transmitting and receiving sound beams to create image lines
This results in a single image or frame being constructed.
What occurs once a frame is completed in the imaging process?
The process can be started over to create more frames over time
This allows for dynamic imaging of the patient’s region.
Fill in the blank: The process of generating images involves transmitting and receiving _______.
[narrow beams of sound]
True or False: The beams used in the imaging process can be pointed in various directions.
True
Different techniques exist for directing the beams.
How is a mechanical image produced?
By actuating the motor to point the transducer crystal in different directions over time
What happens at Time 1 in the mechanical steering process?
The crystal is pointed to the farthest left of the image
What happens when the entire frame is produced (Time N)?
The motor returns the crystal to pointing in the first direction and the entire process is repeated
Fill in the blank: A mechanical image is produced by _______.
[actuating the motor to point the transducer crystal in different directions over time]
What is a sector in the context of imaging?
A wedge of a circle.
Why is the “sector” shape used in imaging?
To deal with issues of limited access because of the presence of ribs.
What type of transducer footprint is used to overcome imaging issues?
A small transducer footprint.
What is the result of the sector imaging approach in terms of field?
A narrow near field and a much broader far field.
What type of imaging is a mechanical curved array transducer used for?
2D imaging, M-mode, Doppler, and color Doppler
These are essential modalities in ultrasound imaging.
What shape does the sector image created by a mechanical curved array transducer have?
Curved top
The curved shape aids in visualization of anatomical structures.
What is the configuration of the crystal in a mechanical curved array transducer?
Single crystal, sometimes split into two halves for CW Doppler or a second small crystal for Doppler
This configuration allows for versatile imaging capabilities.
How is the transducer steered in a mechanical curved array transducer?
By a wobbling motor, rotating crystal, or mirrors
Steering mechanisms enable the transducer to direct the ultrasound beam effectively.
In which planes is the beam of a mechanical curved array transducer symmetric?
Elevation and lateral planes
Symmetry in beam directionality is crucial for accurate imaging.
What is designed to have a broad depth of field in a mechanical curved array transducer?
The transducer
A broad depth of field improves the clarity of structures at varying depths.
What characteristic of the focus is emphasized in a mechanical curved array transducer?
Very deep focus
Deep focus contributes to the ability to visualize deeper structures clearly.
What is a disadvantage of a Mechanical curved Annular Array transducer related to focus?
Fixed focus for transmit and receive
This means that the transducer cannot adjust its focus dynamically during imaging.
What is a disadvantage of a Mechanical curved Annular Array transducer related to durability?
Parts wear out (mechanical wear) and parts break (somewhat fragile)
This indicates that the components of the transducer may degrade over time or may be susceptible to damage.
What type of artifacts can a Mechanical curved Annular Array transducer produce?
Motion artifacts
These artifacts can occur due to patient movement or transducer motion during imaging.
What is a limitation of the Mechanical curved Annular Array transducer regarding imaging quality?
Limited temporal resolution
This affects the ability to capture rapid changes in the imaged area.
What is a disadvantage of the Mechanical curved Annular Array transducer related to imaging flexibility?
Very little imaging flexibility
This means that the transducer has constraints on the imaging angles and areas that can be effectively visualized.
What can cause acoustic shadowing in a Mechanical curved Annular Array transducer?
Air pockets in gel
The presence of air can interfere with the transmission of ultrasound waves, leading to areas of reduced signal.
What is an annular array?
A transducer design where a single round crystal is diced into concentric rings to vary focus.
The focus is adjusted by activating different rings.
How does varying the diameter of the crystal affect focus in an annular array?
Varying the diameter changes the focus depth.
A smaller diameter results in a shallow focus, while a larger diameter results in a deeper focus.
What happens when only the center disc of an annular array is activated?
The focus is very shallow.
This is due to the small diameter of the activated area.
What effect does activating the next outer ring in an annular array have?
It increases the diameter and results in a deeper focus.
Each subsequent ring activated allows for a progressively deeper focus.
What is the significance of the fourth ring in an annular array?
Activating the fourth ring produces a considerably deeper focus.
This illustrates the concept of variable focus in annular arrays.
Fill in the blank: An annular array produces images by ______ the crystal.
mechanically steering
This steering allows for focus adjustments based on which rings are activated.
What imaging modalities does a mechanical annular array transducer support?
2D imaging, M-mode, Doppler, and color Doppler
The transducer is versatile, allowing for various imaging techniques.
What shape does the image created by a mechanical annular array transducer have?
Sector image with a ‘curved top’
This shape is similar to that of a simple mechanical sector.
What are the structural components of a mechanical annular array transducer?
Multiple concentric ‘ring’ elements
These rings contribute to the transducer’s functionality.
How is the transducer steered in a mechanical annular array transducer?
By a wobbling motor, rotating crystal, or mirrors
This steering mechanism allows for flexible imaging angles.
What is the beam symmetry characteristic of a mechanical annular array transducer?
Symmetric in elevation and lateral
This symmetry aids in consistent imaging quality.
What is a disadvantage of mechanical annular array transducers related to durability?
Parts wear out due to mechanical wear
This can lead to decreased performance over time.
What is a disadvantage concerning the fragility of mechanical annular array transducers?
Parts break and are somewhat fragile
This fragility can result in higher maintenance costs.
What type of artifacts are common with mechanical annular array transducers?
Motion artifacts and excessive grating lobe artifacts
Grating lobes are discussed in Chapter 8: Artifacts.
What is a limitation of mechanical annular array transducers in terms of image quality?
Limited temporal resolution
This can affect the clarity of moving images.
What is a financial disadvantage of mechanical annular array transducers compared to single element transducers?
More expensive to make and require more expensive electronics
Each ring element requires its own channel.
What advantage does a mechanical annular array transducer have in terms of focusing?
Variable focus in lateral direction, variable focus in elevation direction, variable depth of field
These focusing capabilities enhance imaging versatility.
What is sequencing in the context of image generation?
Sequencing refers to exciting groups of elements in a specific pattern to scan a region.
It is commonly used with large linear and curved linear arrays.
What is a key characteristic of the transducers used in sequencing?
The geometry of these transducers is large in the lateral direction.
This allows for the lateral dimension of the scan to be accomplished without transducer movement.
True or False: Sequencing requires movement of the transducer to scan a region.
False
The lateral dimension of the scan can be accomplished without transducer movement.
Fill in the blank: Sequencing is commonly used with large __________ and curved linear arrays.
[linear arrays]
What does the term ‘lateral dimension’ refer to in the context of sequencing?
The lateral dimension of the scan that can be accomplished without transducer movement.
This is a result of the large geometry of the transducers.
How does sequencing differ from traditional moving parts methods in image generation?
Sequencing does not involve moving parts and allows for effective scanning using fixed transducer arrays.
This approach enhances efficiency in image generation.
What is a linear switched array?
A group of elements that can be turned on or off through electronic switches.
How many elements did linear switched arrays typically consist of?
Generally 200 elements or more.
What type of image shape did linear switched arrays produce?
Rectangular.
What was the purpose of the large lateral dimension in linear switched arrays?
To provide a large field of view.
Are linear switched arrays still in use today?
No, they are no longer used.
What principle used in linear switched arrays is still commonly used in newer transducers?
The principle of sequencing.
True or False: Linear switched arrays have steering capability.
False.
Fill in the blank: Linear switched arrays were one of the first transducers to employ the _______ approach for image generation.
[sequencing]
What types of newer transducers utilize the principle of sequencing?
Phased array linear and curved linear transducers.
What is the primary use of a linear switched array?
Used for vascular 2D imaging, Doppler, and color Doppler
Linear switched arrays are now considered obsolete.
What type of image does a linear switched array create?
Creates a rectangular image
How are the crystals arranged in a linear switched array?
Multiple rectangular crystals arranged linearly
How are elements fired in a linear switched array?
Elements fired in a specific sequence to create image
Is the beam of a linear switched array symmetric in elevation and lateral planes?
No, beam is not necessarily symmetric in elevation and lateral planes
What is an array in the context of steering electronically?
A transducer comprised of multiple ‘elements’ which can operate together or be controlled separately to transmit and receive signals.
Arrays are commonly used in various applications, including telecommunications and radar systems.
What is the process of cutting a block of piezoelectric crystal into smaller elements called?
‘Dicing’.
Dicing allows each smaller element to function independently in signal transmission and reception.
What is the gap generated by the dicing process referred to as?
‘Kerf’.
The kerf represents the material removed during the dicing process, affecting the overall dimensions of the elements.
How can each element in an array function?
As both a transmitter and a receiver.
This dual functionality is crucial for applications requiring bidirectional communication.
Fill in the blank: The ability to steer electronically requires an _______.
[array].
Arrays enhance the precision and control of electronic steering mechanisms.
What is a phase difference in waves?
The amount of time shift necessary to make two waves align.
Phase difference is crucial in understanding wave behavior and interference patterns.
What happens when two waves are in phase?
The resulting wave has a significantly higher amplitude due to constructive interference.
Constructive interference occurs when the peaks of two waves align.
What occurs when two waves are completely out of phase?
There is cancellation or destructive interference.
Destructive interference happens when the peaks of one wave align with the troughs of another.
What is the result when two waves are partially out of phase?
The resultant wave has an amplitude somewhere between the sum of the two individual waves.
This results in a wave that is weaker than constructive interference but stronger than destructive interference.
What is necessary to create constructive and destructive interference?
Multiple waves.
Interference patterns depend on the interaction of two or more waves.
What is a transducer array?
A collection of smaller transducers used together to form a dynamic system.
Transducer arrays are commonly used in applications like ultrasound imaging.
What is electronic steering in ultrasound?
Electronic steering is achieved by using small phase delays between the excitation pulses that drive the elements of a phased array transducer.
This technique allows for adjusting the direction of the ultrasound beam.
How is electronic receiving achieved in phased array transducers?
Electronic receiving is achieved by applying phase delays to signals received by each of the active elements of the phased array transducer.
This process enhances signal processing and image quality.
What impact did electronic steering have on ultrasound technology?
The advent of electronic steering revolutionized ultrasound and is still the basis of many imaging techniques today.
It marked a significant advancement in medical imaging capabilities.
What are the benefits of electronic steering in ultrasound imaging?
Benefits include:
* Varying incident angles
* Improved image acquisition
* Control of imaging artifacts
These enhancements lead to more accurate diagnostic imaging.
How does electronic steering affect Doppler and color Doppler performance?
Electronic steering allows for significantly improved Doppler and color Doppler performance when flow is parallel to the skin surface.
This is critical for assessing blood flow dynamics.
What technique is used for electronic focusing in phased array transducers?
Varying time delays for electronic steering
This technique allows the system to adjust the focus based on user input.
How does the system primarily change the transmit focus in phased array transducers?
By changing the applied delay profile
This allows the focus to be adjusted to the desired depth.
What additional method can change the focus in phased array transducers?
Changing the number of active elements
This method involves adjusting the transmit aperture.
Fill in the blank: The focus in electronic focusing can be adjusted by changing the _______.
[applied delay profile]
True or False: The transmit focus in phased array transducers can only be changed by varying time delays.
False
The focus can also be changed by altering the number of active elements.
What is a sector transducer used for?
2D imaging, M-mode, Doppler, and color Doppler
Sector transducers are versatile and commonly used in various ultrasound imaging applications.
What type of image does a sector transducer create?
Sector image with small footprint for rib access
This feature allows for better access in certain anatomical regions.
How many elements do sector transducers typically have?
64 to 128 elements common
The number of elements can affect image resolution and quality.
How is a sector transducer steered?
Electronically by phasing in lateral dimension
This allows for real-time imaging adjustments.
What allows for variable transmit focus in a sector transducer?
Electronic phasing in lateral dimension
This capability enhances image clarity at different depths.
What is used to create the appropriate fixed elevation focus in a sector transducer?
Lens
The lens design is crucial for optimizing imaging performance.
What is a disadvantage of sector transducers compared to mechanical transducers?
More expensive to make
The complexity of design and manufacturing contributes to higher costs.
What is a disadvantage of sector transducers compared to 2D arrays?
Fixed elevation focus
This limits the flexibility in imaging compared to 2D arrays.
True or False: Sector transducers can steer in the elevation dimension.
False
To perform 3D imaging, elevation must be manually or mechanically steered.
What type of electronics is necessary for sector transducers?
More expensive electronics (potentially one channel for each element)
This requirement can increase overall system costs.
What dimension is the beam usually not symmetric in for sector transducers?
Elevation and lateral dimensions
Asymmetry can affect image interpretation and quality.
What are the advantages of TEE over single element mechanicals?
Advantages of TEE include:
* Variable focus in the lateral dimension
* Elimination of motion artifacts and problems related to mechanical parts
* Flexibility to perform parallel processing and other advanced processing techniques
TEE stands for Transesophageal Echocardiography, which is a type of imaging technique used in medical diagnostics.
What types of imaging are linear transducers used for?
2D imaging, Doppler, and color Doppler
What type of image is created by sequencing in a linear transducer?
Rectangular image
What type of image is produced by phasing each group of sequenced elements in a linear transducer?
Parallelogram image
How many elements are common in a linear array transducer?
200 to 300 elements
How is the transducer steered in a linear transducer?
Electronically by phasing in the lateral dimension
What type of focus can be achieved through electronic phasing in the lateral dimension?
Variable receive focus
What is used to create the appropriate fixed elevation focus in a linear transducer?
Lens
True or False: The beam in a linear transducer is symmetric in elevation and lateral dimensions.
False
What is a disadvantage of linear transducers relative to mechanical transducers?
More expensive to make than single element mechanical transducers
What type of electronics is necessary for linear transducers?
More expensive electronics (potentially one channel for each element)
What is a disadvantage of linear transducers relative to 2D arrays?
Fixed elevation focus
What limitation is present in elevation steering for linear transducers?
No steering in elevation direction (must manually or mechanically steer for 3D)
What is an advantage of linear transducers relative to single element mechanicals?
Variable focus in the lateral direction
What capability does a linear transducer provide in the near field?
Creation of a wide linear image
What advanced processing techniques can linear transducers perform?
Parallel processing and other advanced processing techniques
What is trapezoidal scanning?
Trapezoidal scanning results in an extended field of view by creating an image that is trapezoidal in shape.
How is trapezoidal scanning produced?
Trapezoidal scanning is produced by treating the linear array as if it were two different transducers.
What is the role of the sector transducer in trapezoidal scanning?
A portion of the array is treated as a sector transducer to produce the left and right ‘wings’ of the image.
What type of transducer is used for the center portion of the trapezoidal image?
The array is treated as an unsteered linear transducer for the center portion of the image.
True or False: Trapezoidal scanning only produces a trapezoidal image.
False
What additional feature does the trapezoidal image demonstrate?
The image demonstrates a steered image (color Doppler).
Fill in the blank: Trapezoidal scanning creates an image that is _______ in shape.
trapezoidal
What is the primary use of a Curved Linear Array?
Used for 2D imaging, Doppler, and color Doppler
Curved Linear Arrays are versatile tools in medical imaging technology.
How is a curved image created in a Curved Linear Array?
By sequencing
Sequencing involves activating multiple elements in a specific order to create the desired image shape.
What type of elements are found in a Curved Linear Array?
Multiple rectangular elements
The arrangement of these elements allows for the curved imaging capability.
Is steering necessary in a Curved Linear Array?
No steering necessary
The geometry of the array itself creates the desired scan shape.
What feature allows variable receive focus in a Curved Linear Array?
Electronic phasing in lateral dimension
This allows for adjustments in focus depending on imaging needs.
What is dynamic receive focus?
Focus that can change in the lateral dimension
This improves image quality by allowing adjustments during imaging.
How does the beam symmetry behave in a Curved Linear Array?
Beam usually not symmetric in elevation and lateral dimensions
This asymmetry can affect the quality of the images produced.
What is a disadvantage of Curved Linear Arrays compared to mechanical transducers?
More expensive to make
The manufacturing process of Curved Linear Arrays is more complex and costly.
What is another disadvantage of Curved Linear Arrays compared to mechanical transducers?
More expensive electronics necessary
Potentially one channel is required for each element, increasing costs.
What is a disadvantage of Curved Linear Arrays compared to 2D arrays?
Fixed elevation focus
This limits the ability to adjust focus in the elevation dimension.
Is steering possible in the elevation dimension with Curved Linear Arrays?
No steering in elevation dimension
To perform 3D imaging, manual or mechanical steering must be implemented.
What is the near field in the context of transducers?
The area between the face of the transducer and the beam focus.
This region is critical for understanding how the transducer interacts with the medium.
What is the far field in relation to transducers?
The region past the focus.
This area is important for analyzing the behavior of the wave as it propagates away from the transducer.
What is the focus in terms of transducers?
Where the beam reaches its minimum diameter.
This point is essential for maximizing the intensity of the sound wave in applications.
What is the focal region?
Region over which the beam is most tightly focused.
Define Detail Resolution.
Ability to distinguish between two objects in any of the three dimensions:
- axial
- lateral
- elevation
What does operating frequency (f.) refer to?
The center frequency of the transmit bandwidth.
How is f. (pulsed mode) determined?
Determined by crystal thickness and speed of sound in crystal material:
Fo = c / 2 (thickness)
What determines f. (continuous mode)?
Determined by the frequency of the drive (transmit) voltage.
