Which adjustment is needed to optimize the waveform below?
Answer(s): A
The waveform in the image shows spectral Doppler signals that are pushed against the upper limit of the display, indicating that the baseline is too high. Lowering the baseline allows for a better visual representation of the entire Doppler signal within the available display range. This adjustment prevents the waveform from being cut off and helps in accurately interpreting the blood flow characteristics.
ARDMS Sonography Principles & Instrumentation GuidelinesKremkau FW. Sonography Principles and Instruments. 9th ed. Philadelphia, PA: Elsevier; 2016.
Which component of a contrast agent causes a marked mismatch in impedance between the agent and blood?
Answer(s): D
Contrast agents used in ultrasound imaging typically consist of microbubbles filled with gas. The significant mismatch in acoustic impedance between the gas in the microbubbles and the surrounding blood creates strong reflectors of the ultrasound waves, enhancing the echogenicity of blood and improving the visibility of blood flow and tissue perfusion. The high contrast provided by the gas-filled microbubbles makes them particularly effective as ultrasound contrast agents.
What is the primary factor that improves lateral resolution?
Answer(s): B
Lateral resolution refers to the ability of the ultrasound system to distinguish two structures that are side by side, perpendicular to the direction of the sound beam. This resolution is primarily improved by reducing the beamwidth. A narrower beamwidth allows for better differentiation between adjacent structures, enhancing the lateral resolution. Higher frequency transducers can also help achieve a narrower beamwidth, but beamwidth is the primary factor.
ARDMS Sonography Principles & Instrumentation GuidelinesHagen-Ansert SL. Textbook of Diagnostic Ultrasonography. 8th ed. St. Louis, MO: Mosby; 2017.
Which is a method to reduce noise?
Persistence is a form of temporal averaging where consecutive frames are averaged to reduce random noise, resulting in a smoother image. Increasing persistence effectively reduces noise by averaging out transient noise artifacts while preserving the true signal. This improves image quality, although it may also reduce the temporal resolution, making it less suitable for rapidly moving structures.
ARDMS Sonography Principles & Instrumentation GuidelinesHedrick WR, Hykes DL, Starchman DE. Ultrasound Physics and Instrumentation. 4th ed. Philadelphia,PA: Elsevier Saunders; 2005.
Which setting can be increased to correct for clutter artifact when using pulsed-wave Doppler?
Answer(s): C
The wall filter, also known as the high-pass filter, is used in Doppler ultrasound to remove low- frequency signals, which are typically associated with clutter artifacts. Clutter artifacts can be caused by tissue motion or vessel wall movement, and they appear as low-frequency signals that can obscure the desired blood flow signals. By increasing the wall filter setting, these low-frequency signals are filtered out, thus reducing the clutter artifact and providing a clearer depiction of the blood flow.
American Registry for Diagnostic Medical Sonography (ARDMS). Sonography Principles and Instrumentation (SPI) Examination Review Guide.
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