ARDMS SPI - Sonography Principles and Instrumentation

When a reflector (such as red blood cells) is moving toward the sound source, the frequency of the reflected sound waves increases. This phenomenon is known as the Doppler effect. The frequency shift occurs because the motion of the reflector compresses the sound waves, leading to a higher frequency than the emitted frequency. This increased frequency is what the Doppler ultrasound system detects and uses to calculate the velocity of the moving reflector.

ARDMS Sonography Principles and Instrumentation guidelines

Hoskins, P. R., Thrush, A., Martin, K., & Whittingham, T. A. (2010). Diagnostic Ultrasound: Physics and Equipment.

Comprehensive and Detailed Explanation From Exact Extract:

Power Doppler detects the strength (amplitude) of returning Doppler signals, which reflects the presence of flow regardless of direction or velocity. It is more sensitive to low-velocity flow and is less angle-dependent than conventional color Doppler.

Principles and Instrumentation state:

"Power Doppler displays the amplitude of Doppler shifts, representing the presence of flow. It does not display direction or velocity."

Laminar flow (A) and velocity (C) are not specifically measured by power Doppler.

Viscosity (D) cannot be assessed by Doppler ultrasound.

Therefore, the correct answer is B: Presence of flow.

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Comprehensive and Detailed Explanation From Exact Extract:

Aliasing happens in Doppler ultrasound when the Doppler shift frequency exceeds half of the pulse repetition frequency (the Nyquist limit). When PRF is too low for the measured Doppler shift, the signal wraps around, producing aliasing.

According to sonography instrumentation reference:

“Aliasing occurs when the Doppler shift frequency exceeds one-half the pulse repetition frequency (Nyquist limit). This results in incorrect display of flow direction and velocity.”

Therefore, the correct answer is C: Aliasing.

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Comprehensive and Detailed Explanation From Exact Extract:

Lateral resolution is determined by the beam width perpendicular to the ultrasound beam’s axis. As depth increases, the beam width changes due to beam divergence after the focal point. Narrower beams (better focusing) provide improved lateral resolution at specific depths.

According to sonography instrumentation reference:

“Lateral resolution depends on the width of the ultrasound beam. The narrower the beam at a particular depth, the better the lateral resolution.”

Therefore, the correct answer is A: Beam width.

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The dead zone in ultrasound imaging refers to the region closest to the transducer where imaging is not possible due to the high amplitude of the initial pulse. In a tissue-mimicking phantom, this is the area where no useful imaging data can be obtained. The purpose of evaluating the dead zone is to ensure that it is as small as possible to maximize the usable imaging depth. In the provided image, Option A represents the area closest to the transducer face, which is typically used to evaluate the dead zone. The other areas are further away and are used for evaluating other parameters such as resolution or depth penetration.

Comprehensive and Detailed Explanation From Exact Extract:

In pulsed-wave transducers, the thickness of the piezoelectric element primarily determines the fundamental operating frequency. Thinner elements produce higher frequencies, while thicker elements produce lower frequencies.

According to sonography instrumentation reference:

“The operating frequency of a pulsed-wave transducer is primarily determined by the thickness of the piezoelectric crystal. Thinner crystals vibrate at higher frequencies.”

Therefore, the correct answer is A: Element thickness.

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The image shown is typical of an abdominal ultrasound, which commonly utilizes a curvilinear transducer. Curvilinear transducers have a wider field of view at depth, making them ideal for imaging large structures within the abdomen. These transducers emit a curved beam, allowing for better penetration and a broader field of view, which is necessary for comprehensive abdominal examinations. The curvature of the image, the wide field of view, and the depth of penetration all suggest the use of a curvilinear transducer.

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

The resonant frequency of a pulsed wave transducer is determined by the thickness of the piezoelectric element and the speed of sound within that element. The resonant frequency is inversely proportional to the element thickness and directly proportional to the speed of sound in the material. Thinner elements and higher sound speeds result in higher resonant frequencies, while thicker elements and lower sound speeds result in lower resonant frequencies.

ARDMS Sonography Principles and Instrumentation guidelines

Kremkau, F. W. (2015). Diagnostic Ultrasound: Principles and Instruments. Elsevier.

Comprehensive and Detailed Explanation From Exact Extract:

The primary purpose of compression is to reduce the dynamic range of received echoes, making the image more visually interpretable by adjusting contrast without losing diagnostic information.

According to sonography instrumentation reference:

“Compression reduces the dynamic range of the signal amplitudes to fit within the display range of the monitor while preserving important differences in tissue echogenicity.”

Therefore, the correct answer is D: Reduce the dynamic range.

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Comprehensive and Detailed Explanation From Exact Extract:

Lateral resolution depends on beam width, which is narrowest at the focal zone. Therefore, positioning the focal zone at the area of interest improves lateral resolution.

According to sonography instrumentation reference:

“Lateral resolution is primarily determined by beam width, which is narrowest at the focus. Optimal lateral resolution occurs at the focal zone.”

Therefore, the correct answer is B: Focal zone.

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