Which factor causes posterior acoustic enhancement?
Answer(s): D
High-Frequency Transducer: These provide better resolution but do not directly cause posterior enhancement.Low-Frequency Transducer: These provide better penetration but are not the cause of posterior enhancement.Strongly Attenuating Structure: This would cause acoustic shadowing rather than enhancement.Weakly Attenuating Structure: Structures that attenuate the ultrasound beam less than the surrounding tissues allow more sound waves to pass through, resulting in increased brightness or "enhancement" behind the structure.
"Ultrasound Physics and Instrumentation" by Frank MieleARDMS Sonography Principles and Instrumentation study materials
Which control should a sonographer use to change contrast resolution?
Reject: This control eliminates low-level noise and weak signals, affecting image quality but not primarily used for contrast resolution.Output Power: This adjusts the intensity of the transmitted ultrasound waves but does not directly change contrast resolution.Gain: This control amplifies all signals equally, affecting brightness but not specifically the contrast resolution.Dynamic Range: Adjusting the dynamic range changes the range of grayscale that the ultrasound system displays, which directly affects the contrast resolution by altering how many shades of gray are visible between the black and white extremes.
"Understanding Ultrasound Physics" by Sidney K. EdelmanARDMS Sonography Principles and Instrumentation study materials
What information does the ultrasound system calculate to display color flow?
Answer(s): B
Color flow Doppler imaging displays the mean Doppler frequency shift, which represents the average velocity of blood flow within a sample volume. The ultrasound system uses autocorrelation to process Doppler signals and compute the mean frequency shift. This provides a color-coded map of blood flow velocities, allowing for visualization of flow direction and speed. The mean Doppler frequency is displayed as different colors, with each color representing a range of velocities.
ARDMS Sonography Principles & Instrumentation GuidelinesKremkau FW. Sonography Principles and Instruments. 9th ed. Philadelphia, PA: Elsevier; 2016.
Which action would increase the frame rate?
The frame rate in ultrasound imaging is influenced by several factors, including the number of focal zones. Each focal zone requires additional transmission and reception cycles, thus decreasing the frame rate. By decreasing the number of focal zones, the system requires fewer cycles per frame, which increases the frame rate. This enhances the temporal resolution, making it easier to capture fast-moving structures in real-time imaging.
ARDMS Sonography Principles & Instrumentation GuidelinesHagen-Ansert SL. Textbook of Diagnostic Ultrasonography. 8th ed. St. Louis, MO: Mosby; 2017.
Which resolution can be evaluated in the area indicated by the red oval in this image of a tissue- equivalent phantom?
The tissue-equivalent phantom image with the red oval indicates an area where axial resolution can be evaluated. Axial resolution refers to the ability to distinguish between two structures that are close together along the axis of the ultrasound beam. It is determined by the spatial pulse length (SPL) of the ultrasound wave. In phantoms, this is typically tested by observing the ability to separate closely spaced targets along the beam's path.
ARDMS Sonography Principles & Instrumentation GuidelinesHedrick WR, Hykes DL, Starchman DE. Ultrasound Physics and Instrumentation. 4th ed. Philadelphia,PA: Elsevier Saunders; 2005.
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