SPI Premium Exam Questions

The Mechanical Index (MI) is related to the likelihood of cavitation, which is the formation of gas bubbles in a liquid due to the low-pressure regions of the ultrasound wave. MI is a parameter that predicts the potential for mechanical bioeffects, including cavitation. A higher MI indicates a greater likelihood of cavitation occurring. It is calculated based on the peak negative pressure and the frequency of the ultrasound wave.

ARDMS Sonography Principles and Instrumentation guidelines

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

Enhancement is an artifact that results from decreased attenuation. When an ultrasound wave travels through a medium with lower attenuation compared to surrounding tissues, it loses less energy. Consequently, the structures located deeper than the low-attenuation medium appear brighter on the ultrasound image. This artifact is commonly observed behind fluid-filled structures, such as cysts or the urinary bladder, where the sound waves encounter minimal resistance and thus less attenuation.References:

ARDMS Sonography Principles and Instrumentation guidelines

"Diagnostic Ultrasound: Principles and Instruments" by Frederick W. Kremkau

Comprehensive and Detailed Explanation From Exact Extract:

The matching layer is placed between the transducer’s piezoelectric element and the patient’s skin. Its primary function is to improve the transmission of sound energy into the body by reducing the acoustic impedance mismatch between the crystal and tissue, minimizing reflection at the transducer surface.

According to sonography instrumentation reference:

“The matching layer improves transmission of ultrasound energy by reducing impedance mismatch between the transducer and soft tissue, thus increasing the efficiency of sound energy transfer.”

Therefore, the correct answer is D: Increase sound transmission.

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When the depth of imaging is increased, the time it takes for the ultrasound pulses to travel to and from the deeper structures also increases, which can reduce the frame rate. To maintain the same frame rate, one effective adjustment is to decrease the image width. Narrowing the image width reduces the number of scan lines required to create each frame, allowing the system to maintain a higher frame rate despite the increased depth.

ARDMS Sonography Principles and Instrumentation guidelines

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