ARDMS SPI Exam Dumps

Continuous wave Doppler uses two crystals -- one for transmitting and one for receiving ultrasound waves continuously. This allows for the measurement of high velocities without aliasing, a common limitation in pulsed wave Doppler. However, continuous wave Doppler does not have range specificity, meaning it cannot precisely determine the depth from which the Doppler signal is returning. Reference: ARDMS Sonography Principles and Instrumentation, Chapter on Doppler Ultrasound.

Comprehensive and Detailed Explanation From Exact Extract:

Veins generally exhibit low-velocity flow. The color scale (or velocity range) must be low enough to detect these slow flows. Decreasing the scale lowers the Nyquist limit, allowing the machine to display lower velocities that may otherwise be undetectable.

Principles and Instrumentation state:

'Reducing the scale increases sensitivity to low-velocity flows such as venous flow, while high scales may suppress these signals.'

Therefore, the correct answer is A: Decreasing scale.

Comprehensive and Detailed Explanation From Exact Extract:

Acoustic impedance (Z) is determined by the product of tissue density () and propagation speed (c), expressed as:

Z = c

According to Principles and Instrumentation:

'Acoustic impedance is a property of the tissue, determined by its density and the speed of sound through it.'

Penetration depth (A) does not affect impedance directly.

Attenuation coefficient (B) affects signal loss, not impedance.

Transducer frequency (D) is independent of tissue impedance.

Therefore, the correct answer is C: Tissue density.

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Overall gain controls the amplification of all the received ultrasound signals uniformly. This adjustment affects the brightness of the entire image by increasing or decreasing the amplification of the echoes returning from all depths. It is a primary control for adjusting image brightness. The overall gain should be set to an appropriate level to ensure that the ultrasound image is neither too bright (over-gained) nor too dark (under-gained), allowing for optimal visualization of the anatomical structures.

American Registry for Diagnostic Medical Sonography (ARDMS). Sonography Principles and Instrumentation (SPI) Examination Review Guide.

Spatial compounding involves acquiring multiple frames from different angles and averaging them. This technique reduces speckle noise, which is a granular interference pattern, and enhances the visualization of specular reflectors (smooth surfaces that reflect sound in a single direction) and attenuated structures (structures that reduce the intensity of the sound beam). By averaging frames from different angles, spatial compounding improves image quality and contrast resolution.

ARDMS Sonography Principles and Instrumentation guidelines

Hedrick, W. R., Hykes, D. L., & Starchman, D. E. (2005). Ultrasound Physics and Instrumentation.