Ultrasound Imaging Concepts Quiz
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Questions and Answers

The product of the ______, ______ and the number of transmit pulses is limited by a physical constant.

frame rate, depth of penetration

The frame rate of an ultrasound image is directly proportional to the number of transmit pulses.

False (B)

What happens to the maximum possible frame rate if the depth of penetration is increased while the number of transmit pulses remains constant?

  • The frame rate remains the same.
  • The frame rate fluctuates.
  • The frame rate increases.
  • The frame rate decreases. (correct)

    • What is the relationship between the maximum allowable PRF and the depth of penetration?

    <p>The maximum allowable PRF is inversely proportional to the depth of penetration.</p> Signup and view all the answers

    Match the following terms to their respective definitions:

    <p>PRF = The number of transmit pulses per second Frame Rate = The number of images produced per second Depth of Penetration = The maximum distance the ultrasound wave travels in the body Echo = The signal due to an individual structure reflecting back to the probe</p> Signup and view all the answers

    The ______ of an ultrasound image is the defined pathway the ultrasound travels through the patient's body.

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

    What is the significance of measuring the arrival time of an echo?

    <p>Measuring the arrival time allows the machine to calculate the depth of the structure which generated the echo.</p> Signup and view all the answers

    Why might a higher frame rate be desired in echocardiography compared to an abdominal scan?

    <p>Echocardiography involves faster-moving structures. (C)</p> Signup and view all the answers

    The aperture of a standard linear or curved array probe is significantly smaller in the elevation plane than in the scan plane.

    <p>True (A)</p> Signup and view all the answers

    Which of the following contributes to slice thickness artifact in standard array probes?

    <p>Smaller aperture in the elevation plane compared to the scan plane (A)</p> Signup and view all the answers

    The beam width at focus in the scan plane can be calculated using the formula: beam width = (2.44 ⨉ λ ⨉ F)/______

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

    How does a standard array probe focus the beam in the elevation plane?

    <p>A lens is used to focus the beam.</p> Signup and view all the answers

    Match the following features with their corresponding type of ultrasound probe:

    <p>Standard array probe = Fixed focal depth in the elevation plane Matrix probe = Wider transducer compared to standard probes</p> Signup and view all the answers

    Which of the following statements about matrix probes is TRUE?

    <p>Matrix probes achieve significantly better focusing in the elevation plane (B)</p> Signup and view all the answers

    Ultrasound machines utilize exclusively digital electronics for their processing and image formation.

    <p>False (B)</p> Signup and view all the answers

    What is the primary goal of this module?

    <p>To explain how ultrasound machines process echoes to create images and describe the available user controls for optimizing image quality</p> Signup and view all the answers

    When ultrasound passes through a region with a propagation speed higher than 1540 m/sec, the tissues are displayed deeper than their actual position.

    <p>False (B)</p> Signup and view all the answers

    What is the typical appearance of a linear structure, such as the diaphragm, when imaged through a region with a different propagation speed?

    <p>The structure appears displaced locally in the area behind the region. (A)</p> Signup and view all the answers

    What is the primary cause of reverberation in ultrasound?

    <p>The reflection of ultrasound repeatedly between two strongly reflective parallel tissue interfaces.</p> Signup and view all the answers

    Reverberation is similar to the reflection of ______ between parallel surfaces, like the walls of a room.

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

    Match the following ultrasound artifacts with their descriptions:

    <p>Reverberation = The reflection of ultrasound waves repeatedly between two strongly reflective parallel tissue interfaces. Distortion = Changes in the shape or size of structures due to variations in propagation speed. Shadowing = A reduction of signal behind a strongly attenuating structure. Enhancement = An increase in signal behind a weakly attenuating structure.</p> Signup and view all the answers

    What kind of tissue interface is a common cause of reverberation?

    <p>Tissue-bone interface (C)</p> Signup and view all the answers

    Reverberation can only occur when ultrasound strikes the tissue interfaces at 90 degrees.

    <p>True (A)</p> Signup and view all the answers

    What distinguishes the appearance of reverberation in ultrasound images?

    <p>A series of equally spaced echoes, progressively weakening in brightness with depth.</p> Signup and view all the answers

    What is the primary factor that determines whether two objects in an ultrasound image are seen as separate entities?

    <p>The distance between the objects (B)</p> Signup and view all the answers

    Axial resolution is primarily determined by the ultrasound beam width.

    <p>False (B)</p> Signup and view all the answers

    What is the formula for calculating axial resolution in an ultrasound image?

    <p>(cτ/2)</p> Signup and view all the answers

    To improve axial resolution, the _____ should be as short as possible.

    <p>pulse duration</p> Signup and view all the answers

    Which of the following is NOT a component of spatial resolution in ultrasound imaging?

    <p>Frame rate (A)</p> Signup and view all the answers

    A higher ultrasound frequency generally leads to better axial resolution.

    <p>True (A)</p> Signup and view all the answers

    Match the following terms with their corresponding definitions:

    <p>Axial resolution = The minimum separation in depth between two objects that can be resolved Lateral resolution = The minimum separation in the direction perpendicular to the beam that can be resolved Slice thickness = The thickness of the ultrasound beam that results in echoes from objects within that thickness being received together Pulse duration = The length of time that the ultrasound pulse is emitted</p> Signup and view all the answers

    Why is it important to consider slice thickness when interpreting ultrasound images?

    <p>Slice thickness can affect the accuracy of measurements and the visibility of small structures, as objects within the slice thickness may appear as a single object.</p> Signup and view all the answers

    Which of the following statements is TRUE about beam width and its effect on ultrasound image quality?

    <p>Beam width degrades image resolution and reduces the accuracy of measurements. (A)</p> Signup and view all the answers

    Sidelobes are a desirable artifact that improves the detail in ultrasound images.

    <p>False (B)</p> Signup and view all the answers

    Match the following terms with their correct definitions:

    <p>Sidelobe artifact = Artifact caused by the beam hitting a strong reflector outside of the main beam, resulting in echoes being displayed incorrectly. Apodisation = Technique used in ultrasound machines to reduce the amplitude of sidelobes by lowering the transmit pulse and receive gain for outer elements. Slice thickness artifact = Artifact arising from the beam's limited focus in the direction across the transducer, resulting in a thicker slice than ideal, affecting image quality.</p> Signup and view all the answers

    The ______ of sidelobes can be reduced by using a technique called apodisation.

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

    Why are sidelobe artifacts more commonly visible in liquid-filled areas?

    <p>Liquid-filled areas tend to have strong reflectors, which, when encountered by sidelobes, can produce detectable echoes that appear as artifacts.</p> Signup and view all the answers

    Beam width effects are minimized when tissues are scanned at 90° (perpendicular incidence).

    <p>True (A)</p> Signup and view all the answers

    What is the consequence of reducing the amplitude of sidelobes using apodisation?

    <p>The width of the main beam is increased. (A)</p> Signup and view all the answers

    What is the primary factor determining slice thickness?

    <p>The focus of the beam in the direction perpendicular to the transducer face.</p> Signup and view all the answers

    Shadowing occurs when a region has lower attenuation than the surrounding tissues.

    <p>False (B)</p> Signup and view all the answers

    What is the term used to describe a darkened line cast behind a region with high tissue attenuation?

    <p>Shadowing (D)</p> Signup and view all the answers

    What is the primary factor that determines the effectiveness of shadowing as a diagnostic sign?

    <p>The width of the ultrasound beam relative to the attenuating object.</p> Signup and view all the answers

    Shadowing is always in the direction of the ______ beam.

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

    Match the following ultrasound phenomena with their descriptions:

    <p>Shadowing = Darkened area behind a region of high attenuation Enhancement = Brightened area behind a region of low attenuation Edge Shadowing = Shadowing caused by the edge of a structure Artifact = False echoes appearing in an image</p> Signup and view all the answers

    Study Notes

    Introduction to Diagnostic Ultrasound Technology

    • Course aims to provide a fundamental understanding of diagnostic ultrasound physics
    • Course structure parallels textbook "The Physics and Technology of Diagnostic Ultrasound"
    • Online course is an introduction; use textbook for detailed information

    Chapter 1: Ultrasound Interaction with Tissue

    • Ultrasound is a high-frequency sound
    • Frequencies range from 2 MHz to 20 MHz
    • This is much higher than audible sound (20 Hz to 20 kHz)
    • Higher frequencies improve image resolution
    • Ultrasound waves consist of oscillating pressures
    • Oscillations cause tissue compression and rarefaction
    • Ultrasound travels at a constant speed through tissues
    • Amplitude (A) represents the maximum pressure change from the mean pressure; this determines energy level
    • Period (T) is the time occupied by one cycle; inversely related to frequency (T = 1/f)
    • Wavelength (λ) is the physical length of a single cycle; shorter wavelengths mean better image resolution; the relation between speed, frequency, and wavelength: c = fλ
    • Typical ultrasound frequencies used and corresponding wavelength in soft tissue
    • Higher frequency leads to better resolution, but there's a limit

    Lesson 2: Attenuation

    • Attenuation is the progressive weakening of the ultrasound wave as it passes through tissue.
    • The primary cause of attenuation is energy absorption by the tissue due to friction.
    • Other factors causing attenuation include reflection and scattering from structures in the body; energy is lost from the beam resulting in attenuation.
    • Defocusing spreads the ultrasound beam over a wider area, reducing its intensity.

    Lesson 3: Reflection and Scattering

    • Reflection is the interaction of ultrasound with large, smooth surfaces
    • Scattering is the interaction of ultrasound with small structures like blood cells
    • Reflection coefficient (R) measures the fraction of ultrasound energy reflected; it depends on the difference in acoustic impedance between two tissues.
    • When acoustic impedance values of tissues are similar, reflection is reduced, and vice versa

    Lesson 4: Refraction

    • Refraction is the bending of ultrasound as it passes through an interface between different tissues.
    • The amount of refraction depends on propagation speeds and the angle of incidence
    • If ultrasound strikes the interface at 90 degrees (perpendicular incidence) there is no refraction.

    Lesson 1 - Transmit Pulse

    • Ultrasound pulse is a burst of energy that starts and stops, and it's the opposite of continuous wave ultrasound.
    • The pulse duration is determined by the number of cycles in the pulse and the frequency, and shorter durations are better for resolution;
    • The period corresponds to 1/frequency

    Lesson 2 - Pulse Repetition Frequency (PRF)

    • Describes the rate at which the ultrasound machine transmits pulses to scan the body.
    • It's important for generating real-time images (movie-like), so the machine must create images at a rate of 15-20 per second.
    • High PRF is essential for real-time imaging, but there's a limit to how fast the machine can transmit pulses. The maximum limit is determined by the 'depth of penetration'. Deeper areas = Lower PRF to avoid range ambiguity artifacts.

    Lesson 3 – Pulse-Echo Principle

    • Ultrasound machine measures the time between transmitting a pulse and receiving the echo.
    • By knowing the time, machine calculates the echo's origin depth within the body.
    • Propagation speed is assumed at 1540 m/sec for all tissues. This calculates depth of the reflector.

    Lesson 4 - PRF Limitations

    • The maximum allowable PRF is limited by the depth of penetration of the ultrasound beam.
    • If the machine transmits pulses before all prior echoes are received, creates a range ambiguity, causing an artifact in the final image.

    Lesson 6 – Principles of Image Formation

    • Ultrasound probe transmits a pulse of ultrasound which travels through the body.
    • Structures within the beam scatter some of the transmitted energy, which returns to the probe as an echo signal.
    • Machine processes the echo arrival times to calculate the distance of the structure in the body from the probe.
    • The machine uses the echo intensity (strength) to determine the brightness of the dot on the image (grey scale). Black is for no echo detected.
    • The location of the echo within the image depends on the position of the probe's emitted beam, and so if the emitted beam is not aligned with the reflected/scattered echo, the position displayed on the image will be inaccurate.

    Lesson 7 - Transducer Principles

    • The transducer in the probe generates the transmit pulse and receives returning echoes
    • It is made from piezoelectric materials which change shape when an electrical voltage is applied.

    Lesson 2 - Focussing

    • Beam width is a problem; the beam is not perfectly narrow; the width is a function of the transducer aperture and wavelength.
    • The beam width is equal in the focal zone, when it is at its narrowest.
    • Away from the focus, the beam is wider.
    • The wider the beam, the more blurry the image.

    Lesson 3 - Electronics Focussing

    • The machine sends electrical voltages to the transducer elements at specific times to steer the beam.
    • Precise delays in the voltages allow better focussing.
    • The user can adjust focal depth in the image, affecting image sharpness/focus.

    Lesson 3 - Amplifier, TGC

    • The amplifier boosts weak returning signals into higher voltage signals.
    • TGC corrects for attenuation of ultrasound signals throughout the image depth. Increased gain = brighter image

    Lesson 4 - Dynamic Range Compression

    • Dynamic range is the ratio of the strongest to the weakest echo in an image. Range is wide (60dB or more) whereas in the displayed image, the range is much narrower (30 dB).
    • The machine compresses the dynamic range of the echo signals to create an image that shows a range of brightness intensity.

    Lesson 5 - Scan Converter

    • Processes echo arrival times to place echoes in the correct position in the image memory. Factors like probe geometry, beam direction, and depth are considered in placing the echo.

    Lesson 6 - Image Memory

    • The ultrasound image is stored in the image memory as a 2D array of pixels; the value stored in each pixel determines the grey scale colour.
    • Several images from recent scanning are often stored, allowing you to go back to capture a specific image.

    Lesson 7 - Pre-processing

    • Changes to the echo data before it's stored as an image, such as zoom or frame averaging.
    • Changes are not reversible.

    Lesson 8 – Post-processing

    • Changes to the stored image data for display, which are reversible, and give the user control of the image for display clarity (e.g. zoom)
    • Include measurements, colour mapping, curves, and zoom

    Lesson 9 - Image Display & Storage

    • The display of ultrasound images is similar to computer screens, and stable and reliable.
    • Includes various image storage options such as short term memory, PACS, removable media, or hard copy (film).

    Lesson 1 - Image Artifacts

    • Artifacts are false images or distortions of actual body structures
    • Caused by factors like poor image forming mechanisms, and equipment malfunctions.
    • Artefacts may also be caused by faulty equipment, or incorrect user settings or procedures.
    • Artefacts can cause problems when interpreting and reading an image.

    Lesson 2 - Attenuation Artifacts

    • Attenuation is the weakening of an ultrasound wave as it travels through tissues
    • Varying tissue attenuation can cause shadowing and enhancement artifacts.

    Lesson 3 - Depth Artifacts

    • Propagation artifacts occur when tissue propagation speed differs from the assumed 1540 m/sec. This leads to inaccurate measurements of depth.
    • Reverberation artifacts occur when sound reflects between strong interfaces. Multiple echoes create a series of regularly spaced layers.

    Lesson 4 - Beam Dimension Artifacts

    • Beam width artifacts occur because the ultrasound machine displays an object as if it were in the middle of the beam.
    • The actual lateral resolution is reduced because the width of the beam is greater than the distance between individual echoes in the image, leading to blurring around the edges of structures.

    Lesson 5 - Beam Path Artifacts

    • Mirror image artifacts occur when an interface is encountered at an oblique angle. The machine assumes the returning echo comes from a straight path and displays it in a different position to its actual location.
    • Refraction artifacts happen when the ultrasound beam changes direction at tissue interfaces when the ultrasound speed changes. If the angle of incidence is not near 90 degrees, the image will be affected.

    Ultrasound Instrumentation

    • Understanding basic operational components of ultrasound machines (Probe, Transmitter, Beam-former, Amplifier, TGC, Scan Converter)
    • The workflow & function, use and controls of ultrasound machines.

    Historical Overview of Ultrasound

    • Historical development of X-Rays & ultrasound
    • Understanding how the development of ultrasound has shaped the current safety guidelines
    • Recognizing the limitations of current knowledge about possible long-term harmful effects of certain medical procedures.

    Doppler Ultrasound

    • Doppler ultrasound can detect moving tissues and provide information about the flow of blood.
    • Doppler effect causes the frequency of a returning signal to change if the moving tissue is towards or away from the sound probe; this shift in frequency gives information about the velocity of the moving tissue.
    • Understanding the Doppler equation and factors that affect Doppler shift (e.g., Doppler angle)

    Doppler Artifacts

    • Frequency aliasing is an issue where the velocity of the moving tissue (e.g., blood) is too high compared to the pulse repetition frequency (PRF) of the machine.
    • Intrinsic spectral broadening is due to the fact that the Doppler ultrasound can travel through a range of angles and not directly, and this causes the shift in the Doppler signal to be spread over a wider range of frequencies.

    3D/4D Imaging

    • Imaging technology that allows the display of an object in 3D to be more easily understood
    • How this technique differs from 2D imaging
    • Methods used for 3D/4D creation (including rendering methods for creating the actual image)
    • Applications of 3D/4D technology

    Synthetic Aperture Imaging

    • A technology for 3D imaging where the different ultrasound beam directions are combined to generate a complete image.

    Harmonic Imaging

    • Using harmonic imaging, the machine does not transmit or receive the fundamental frequencies, it only works with the second or third harmonic frequencies, reducing artifacts.
    • Images created are more accurate and clearer than ordinary images.

    Ultrasound Contrast Agents

    • Agents in medical imaging that enhance tissue features in an ultrasound image.
    • These agents are used in the bloodstream, and they are more echogenic, allowing for easier visualization of the tissues and organs
    • The contrast agent is administered intravenously and this method is followed by a low mechanical index.

    Bioeffects and Safety

    • The physical effects of ultrasound on tissue and organs, mainly from thermal and mechanical effects, or those from the use of contrast agents.
    • Guidelines and safety standards relating to proper ultrasound usage
    • Considerations for equipment and user settings for safe operation.

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    Related Documents

    Introduction to Diagnostic Ultrasound Technology PDF

    Description

    Test your knowledge on essential concepts in ultrasound imaging, including frame rates, depth of penetration, and beam characteristics. This quiz covers key terms and relationships that affect image quality and diagnostic practices. Ideal for students and professionals in the field of medical imaging.

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