Podcast
Questions and Answers
What defines the width of a crystal in the ultrasound probe anatomy circa 1988?
What defines the width of a crystal in the ultrasound probe anatomy circa 1988?
- 1/4 wavelength ($ rac{1}{4} imes ext{λ}$)
- Full wavelength ($2 imes ext{λ}$)
- 1 wavelength ($1 imes ext{λ}$)
- 1/2 wavelength ($ rac{1}{2} imes ext{λ}$) (correct)
What factor primarily causes the issue of unfocused ultrasound transducers?
What factor primarily causes the issue of unfocused ultrasound transducers?
- Lack of backing layer
- Fraunhofer diffraction (correct)
- Narrow aperture size
- High frequency output
Which statement correctly describes the Near Field Depth (NFD)?
Which statement correctly describes the Near Field Depth (NFD)?
- It has a dependency on the crystal diameter and wavelength. (correct)
- It is constant and does not vary with aperture size.
- It can only be calculated with digital systems.
- It is directly proportional to the frequency.
In the context of the pure analogue AAA systems, what is a key component that plays back the recorded sound?
In the context of the pure analogue AAA systems, what is a key component that plays back the recorded sound?
Which reason is commonly given for not relying on analogue systems in ultrasound technology?
Which reason is commonly given for not relying on analogue systems in ultrasound technology?
What role does the user play in the functioning of an ultrasound probe?
What role does the user play in the functioning of an ultrasound probe?
Which component of the ultrasound probe is essential for converting electrical energy to mechanical energy?
Which component of the ultrasound probe is essential for converting electrical energy to mechanical energy?
What is a disadvantage of using P.Z.T. in ultrasound probes?
What is a disadvantage of using P.Z.T. in ultrasound probes?
What is meant by 'ringing' in the context of ultrasound probes?
What is meant by 'ringing' in the context of ultrasound probes?
How does the matching layer in an ultrasound probe function?
How does the matching layer in an ultrasound probe function?
Which aspect of the ultrasound probe does the backing layer influence?
Which aspect of the ultrasound probe does the backing layer influence?
What is one advantage of using digital probes in ultrasound technology?
What is one advantage of using digital probes in ultrasound technology?
What happens to the ultrasound waves if the P.Z.T. has high acoustic impedance?
What happens to the ultrasound waves if the P.Z.T. has high acoustic impedance?
What is the purpose of the matching layer in an ultrasound probe?
What is the purpose of the matching layer in an ultrasound probe?
How does a phased array probe achieve beamforming?
How does a phased array probe achieve beamforming?
What is the role of the backing layer in an ultrasound probe?
What is the role of the backing layer in an ultrasound probe?
Which control adjusts the image depth in ultrasound scanning?
Which control adjusts the image depth in ultrasound scanning?
What happens when sound reflects off both the front and back of the matching layer?
What happens when sound reflects off both the front and back of the matching layer?
What is indicated by the order of firing in crystals of an ultrasound probe?
What is indicated by the order of firing in crystals of an ultrasound probe?
Which aspect is NOT a pre-send control in ultrasound technology?
Which aspect is NOT a pre-send control in ultrasound technology?
What type of crystals are used in an ultrasound probe's array?
What type of crystals are used in an ultrasound probe's array?
What is the first function of a receiving beam former?
What is the first function of a receiving beam former?
Which of these components affects the scan image width?
Which of these components affects the scan image width?
What role does the transmit beamformer play in an ultrasound machine?
What role does the transmit beamformer play in an ultrasound machine?
Which component is responsible for pre-processing the ultrasound signals?
Which component is responsible for pre-processing the ultrasound signals?
What are some of the disadvantages of ultrasound machines mentioned?
What are some of the disadvantages of ultrasound machines mentioned?
How does the receive beamformer differ from the transmit beamformer?
How does the receive beamformer differ from the transmit beamformer?
What is one of the functions of the pre-send controls in ultrasound machines?
What is one of the functions of the pre-send controls in ultrasound machines?
What is the purpose of the digital analogue converter (DAC) in ultrasound technology?
What is the purpose of the digital analogue converter (DAC) in ultrasound technology?
What does the amplitude processing of received signals involve?
What does the amplitude processing of received signals involve?
Why are some components of ultrasound machines considered fragile?
Why are some components of ultrasound machines considered fragile?
What pattern can be identified in the binary sequences presented?
What pattern can be identified in the binary sequences presented?
What is the role of increasing ‘different greys’ as mentioned in the content?
What is the role of increasing ‘different greys’ as mentioned in the content?
How do the sequences relate to digital output?
How do the sequences relate to digital output?
Which characteristic is shared by all the binary sequences in the content?
Which characteristic is shared by all the binary sequences in the content?
What can be inferred about the structure of the binary sequences?
What can be inferred about the structure of the binary sequences?
What is the significance of the repeated elements in the sequences?
What is the significance of the repeated elements in the sequences?
Which of the following best describes a possible application of the binary sequences?
Which of the following best describes a possible application of the binary sequences?
What type of information can the binary sequences potentially encode?
What type of information can the binary sequences potentially encode?
How might the differentiation in greys be significant in terms of graphic representation?
How might the differentiation in greys be significant in terms of graphic representation?
What does the variety in binary sequences suggest about encoding efficiency?
What does the variety in binary sequences suggest about encoding efficiency?
What is the primary function of the analogue digital controller (ADC)?
What is the primary function of the analogue digital controller (ADC)?
What does the T.EQ setting accomplish in the signal processing chain?
What does the T.EQ setting accomplish in the signal processing chain?
In coherent signal processing, what is the primary objective once the signal is digitized?
In coherent signal processing, what is the primary objective once the signal is digitized?
What is the purpose of scan conversion in the signal processing workflow?
What is the purpose of scan conversion in the signal processing workflow?
During which stage is incoherent signal processing executed?
During which stage is incoherent signal processing executed?
Which of the following describes demodulation in the context of signal processing?
Which of the following describes demodulation in the context of signal processing?
What does cine memory store in ultrasound systems?
What does cine memory store in ultrasound systems?
Which control options are available post-digital receive?
Which control options are available post-digital receive?
What is the output of the ADC typically represented as?
What is the output of the ADC typically represented as?
What role do user controls provide in the ultrasound system processes?
What role do user controls provide in the ultrasound system processes?
What does the term 'coherent signal processing' refer to?
What does the term 'coherent signal processing' refer to?
In the context of signal processing, what is TGC primarily used for?
In the context of signal processing, what is TGC primarily used for?
What type of signal does demodulation typically produce?
What type of signal does demodulation typically produce?
Flashcards
Near Field Depth (NFD)
Near Field Depth (NFD)
The distance from the center of the ultrasound transducer to the point where the beam begins to diverge significantly.
Diffraction
Diffraction
The phenomenon where an ultrasound beam spreads out as it travels through tissue, causing a loss of resolution.
Annular Array Transducer
Annular Array Transducer
A type of ultrasound transducer that uses multiple crystals arranged in a circle to create a focused beam.
Rayleigh Distance
Rayleigh Distance
The distance between the center of an ultrasound crystal and the point where the beam begins to significantly diverge due to diffraction.
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Analogue Probe
Analogue Probe
A type of ultrasound probe that uses a single, fixed element to transmit and receive ultrasound waves.
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Transmit beamformer function
Transmit beamformer function
The process of combining the preset electrical output from the ultrasound machine with user controls to create the correct electrical profile for exciting the crystals in the probe array.
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Crystal array
Crystal array
A collection of crystals within the ultrasound probe that generate and receive ultrasound waves.
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Fan (Scan image width)
Fan (Scan image width)
The ability to adjust the width of the ultrasound beam, affecting the area of the scan.
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Frequency
Frequency
The frequency of the ultrasound waves emitted by the probe, influencing the depth of penetration and image resolution.
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Focus
Focus
The process of focusing the ultrasound beam to improve the image quality in a specific area.
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Digital-to-analog converter (DAC)
Digital-to-analog converter (DAC)
The electronic component that converts digital data from the ultrasound machine to analog signals that can be sent to the probe.
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Receive processing
Receive processing
The processing of signals after they are received by the probe before they are displayed on the screen.
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Receive beamformer
Receive beamformer
Part of the ultrasound machine that receives the echoes from the tissues and converts them into digital signals.
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Binary sequence
Binary sequence
A binary sequence, often used in computer science to represent data, instructions, and other types of information.
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Bit
Bit
A single 0 or 1 in a binary sequence representing a bit of data.
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Decoding
Decoding
The process of converting a binary sequence into human-readable characters or symbols.
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Binary Code
Binary Code
A specific combination of bits representing a particular character, instruction, or value.
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Encoding
Encoding
Converting information from a human-readable format into a binary sequence.
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Binary System
Binary System
The representation of information using a combination of two distinct states, typically 0 and 1.
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Calculating possible combinations
Calculating possible combinations
Determining how many unique possibilities or combinations can be represented by a given number of bits.
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Signal Amplitude
Signal Amplitude
A variation in the intensity of a signal, often used to represent data in digital systems.
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Signal Frequency
Signal Frequency
The frequency of a signal, often used to represent data in digital systems.
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Voltage Level Representation
Voltage Level Representation
The representation of data using varying voltage levels, often used in digital circuits.
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Beam forming
Beam forming
The process of manipulating the signals sent to the transducer crystals within an ultrasound probe to generate a focused and specific ultrasound beam. It involves coordinating the timing and intensity of signals to achieve precise targeting and imaging.
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PZT (Piezoelectric Transducer)
PZT (Piezoelectric Transducer)
A key component of an ultrasound probe, responsible for converting electrical signals into mechanical vibrations (sound waves) and vice versa. It is made of piezoelectric material.
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Backing Layer
Backing Layer
A layer behind the PZT crystal in an ultrasound probe designed to absorb sound waves after they have travelled through the crystal. This reduces 'ringing' and improves image quality.
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Matching Layer
Matching Layer
A layer placed in front of the PZT crystal in an ultrasound probe. It helps to match the impedance of the crystal to the impedance of the tissues being imaged, improving the transmission of ultrasound into the body.
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Acoustic Window
Acoustic Window
The outermost layer of an ultrasound probe that allows ultrasound waves to pass through it and into the body. It's often made of a material that is acoustically transparent, such as plastic.
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PZT's Efficiency for Energy Conversion
PZT's Efficiency for Energy Conversion
A property of PZT (Piezoelectric Transducer) that makes it efficient at converting electrical energy into mechanical energy (sound waves) and vice versa, making it ideal for ultrasound probes.
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PZT's Impedance Disparity
PZT's Impedance Disparity
A property of PZT where its acoustic impedance is significantly higher than that of soft tissue. This can cause unwanted 'ringing' in the crystal, leading to prolonged vibrations after the signal is sent. This is usually addressed by the backing layer.
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Crystal (in ultrasound probe)
Crystal (in ultrasound probe)
A piezoelectric crystal, often made of PZT, that converts electrical energy into mechanical vibrations, generating ultrasound waves. These crystals are responsible for transmitting and receiving the sound waves used in ultrasound imaging.
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Array (Ultrasound probe)
Array (Ultrasound probe)
A collection of multiple crystals in an ultrasound probe that allows for focusing, steering, and imaging in various directions. This technique is known as beamforming.
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3D Ultrasound Scanning
3D Ultrasound Scanning
The use of a phased array probe to create 3D images of the body by sequentially emitting and receiving sound waves from multiple angles. This allows for volumetric visualization of organs and structures.
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Focus (Pre-send control)
Focus (Pre-send control)
The ability to change the focal point of the ultrasound beam to focus on different depths within the body. This allows for selective imaging of specific areas of interest.
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Frequency (Pre-send control)
Frequency (Pre-send control)
The frequency of the sound waves emitted by the ultrasound probe, which determines the resolution and imaging capabilities. Higher frequencies provide better resolution but penetrate less deeply.
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Auto Gain
Auto Gain
A system that automatically adjusts the gain of the ultrasound signal to optimize the image quality.
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User Gain Control
User Gain Control
The user-adjustable gain control that allows the sonographer to amplify the ultrasound signal selectively to enhance specific areas of the image.
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Time Gain Compensation (TGC)
Time Gain Compensation (TGC)
The user-adjustable gain control that allows the sonographer to enhance the signal strength at various depths within the image.
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T.EQ. (Time & Equalization)
T.EQ. (Time & Equalization)
A function that helps to re-balance the ultrasound signal within the optimal range for processing, often used after the Auto Gain and TGC settings have been applied.
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Analog-to-Digital Conversion (ADC)
Analog-to-Digital Conversion (ADC)
The process of converting the analog electrical signals from the ultrasound transducer into a digital format, which can be processed by the ultrasound machine.
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Coherent Signal Processing
Coherent Signal Processing
A system within the ultrasound machine that processes and organizes the digital ultrasound signals from all transducer elements to create a coherent image.
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Demodulation
Demodulation
The process of converting the coherent ultrasound signal into a signal with a value independent of its phase or amplitude, allowing for display on a screen.
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Image Formation
Image Formation
The process of taking the raw ultrasound data and transforming it into a digital image ready for display.
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Scan Conversion
Scan Conversion
A system that converts the analog electrical signals received from the image former into a digital format.
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Cine Memory
Cine Memory
Digital storage of the image data, including the raw data captured during the scan.
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Post-Processing
Post-Processing
A feature that allows the user to manipulate the image data after it has been acquired, including adjusting gain, changing contrast, and applying other image enhancement techniques.
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Digitization
Digitization
The process of converting the ultrasound signal into a digital format.
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Pre-Digital Receive Controls
Pre-Digital Receive Controls
A system that controls the acquisition parameters before the ADC conversion, such as depth, gain, and TGC settings.
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Post-Digital Receive Controls
Post-Digital Receive Controls
A system that controls the image parameters after the ADC conversion, such as gain, contrast, and color settings.
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Image Building
Image Building
The process of collecting ultrasound reflections from the body and applying them to the appropriate digital pixel location.
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Ultrasound Probe Anatomy
- Ultrasound probes, circa 1988, used annular arrays.
- Crystal width was ½λ (lambda).
Problems of Unfocused Ultrasound Transducers
- Fresnel Diffraction (plane wave) occurs in the near field.
- Fraunhofer Diffraction (spherical spreading) occurs in the far field.
- Near field depth (NFD) is calculated by NFD = D2/4λ or π2/λ.
- D is diameter or radius of crystal aperture
- λ is wavelength
Pure Analogue (AAA) Systems
- Ultrasound signals received by electromagnetic microphones were recorded onto vibrational devices.
- Signals were played back through another vibrational device (a speaker).
- Issues included high interference, inability to manipulate signals, and expensive/fragile components.
Ultrasound Machine Anatomy (Basic)
- A basic ultrasound machine has transmit and receive beam formers.
- There's transmit power control, digitisation, amplitude processing, and image formation.
- Post-processing, cine memory, and output to the screen complete the process.
Ultrasound Transducer Array Block Diagram
- Components include pre-send controls, beam former, transmit beam former, receive beam former, amplitude and phase processing, coherent image former, demodulation/compression, non-coherent image former, display, post-processing, cine memory, and scan conversion.
Transmit Beam Former
- The transmit beam former takes the preset electrical output from the machine.
- It combines this with user controls to form the correct electrical signals to excite the crystals in the probe array.
- The electrical output from the machine and the user selection are combined.
Digital-Analogue Converter (Coordinator)
- The digital-analogue coordinator coordinates the analogue response.
- The response from crystals within the probe produces the correct beam of ultrasound.
- This combines the beam formed by the transducer and user selection settings.
Ultrasound Probe Anatomy - Digital Probes
- Digital probes have ultrasound insulation, a backing layer, a PZT crystal array, a matching layer, and an acoustic window.
Ultrasound Probe Anatomy – PZT Advantages
- Efficient conversion between electrical and mechanical energy, relatively easy machining.
- Relatively easy to manufacture in various shapes and sizes.
Ultrasound Probe Anatomy – PZT Disadvantages
- Impedance drastically different from soft tissue, leading to extensive ringing.
Ultrasound Probe Anatomy – Backing Layer
- Ideally, the backing layer has a lower impedance than the PZT material to reduce ringing.
- This material should ideally have high acoustic impedance to absorb reflected ultrasound waves, reducing unwanted ringing.
Ultrasound Probe Anatomy – Matching Layer
- A matching layer is also needed to help transmit sound.
- The layer's impedance is chosen to be a square root of that of the PZT and the human tissue.
Ultrasound Probe Anatomy – Acoustic Window
- A protective layer, the acoustic window, comes between the matching layer and the human body.
- Its impedance helps transfer sound efficiently to the body while being a transparent barrier.
Ultrasound Probe Anatomy - Different Probe Types
- There are various probe types, including those with linear and array crystal distributions.
Ultrasound Probe Anatomy– Beamforming Phased Array
- It clarifies how phased array probes work and how 3D scanning is executed.
- Electrical current sequentially activates crystals for precise beam formation and focusing.
Ultrasound Probe Anatomy– Receiving Beam Former
- It takes raw analogue electrical signals and amplifies them into usable output.
- It enables user control of gain settings and TGC adjustments for improved signal balance.
Ultrasound Probe Anatomy – Analogue Digital Converter
- It converts the raw analogue signals into suitable digital outputs for the display.
Ultrasound Probe Anatomy – Coherent Signal Processing
- The scanner digitizes and processes signals from multiple crystals to create a coherent signal.
Ultrasound Probe Anatomy – Demodulation and Incoherent Signal Processing
- Demodulation converts the processed coherent signal into an incoherent signal for display output.
Ultrasound Probe Anatomy – Cine Memory
- Stores the raw digital data from the ultrasound imaging process.
Ultrasound Probe Anatomy – Scan Conversion
- Takes each scan line and displays results as part of the image.
- Analogue-to-digital converters (ADCs) convert output from image formers into digital outputs suitable for display.
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