SPI Exam Dumps - Sonography Principles and Instrumentation

Comprehensive and Detailed Explanation From Exact Extract:

Compression reduces the dynamic range of the returning echoes, which alters how many shades of gray are displayed. It compresses the range of signal amplitudes to fit into the grayscale display range.

According to sonography instrumentation reference:

“Compression alters the dynamic range, adjusting how many shades of gray are displayed to optimize image contrast.”

Therefore, the correct answer is B: The shades of gray displayed.

—

In the tissue-mimicking phantom image, Option D (blue box) is used to evaluate transverse distance measurement accuracy. Phantoms are used to simulate human tissue and provide a standardized way to test the accuracy and precision of ultrasound machines. Transverse distance measurement accuracy is assessed by measuring known distances between targets in the phantom. The blue box (Option D) typically contains targets positioned to specifically test the accuracy of transverse measurements, ensuring that the ultrasound system provides reliable and precise distance readings.

References

ARDMS Sonography Principles and Instrumentation (SPI) Exam Study Guide

"Quality Assurance for Ultrasound Imaging Systems" by AAPM (American Association of Physicists in Medicine)

Comprehensive and Detailed Explanation From Exact Extract:

In color Doppler, frequency shifts can be displayed either above or below the baseline in spectral Doppler. In spectral Doppler, a positive shift is displayed above the baseline by default (unless inverted). In color Doppler, red/blue assignments depend on color map orientation.

Principles and Instrumentation state:

"A positive Doppler shift (flow toward the transducer) is displayed above the baseline in spectral Doppler."

Red color (B) does not always correspond to positive shift; it depends on color map.

Negative shift (C) does not always indicate venous flow.

Wall filter settings (D) affect low-velocity signals, not shift direction.

Therefore, the correct answer is A: A positive shift is always above the baseline.

—

Autoclaving involves high-pressure steam at high temperatures, which can damage the delicate piezoelectric crystals within the ultrasound transducer. These crystals are responsible for converting electrical energy into sound waves and vice versa. Exposure to the extreme conditions of an autoclave can cause thermal and mechanical damage to the crystals, rendering the transducer ineffective.

ARDMS Sonography Principles and Instrumentation guidelines

Zagzebski, J. A. (1996). Essentials of Ultrasound Physics.

Comprehensive and Detailed Explanation From Exact Extract:

Higher frequencies are more attenuated than lower frequencies. When scanning calcified structures, increasing the frequency enhances attenuation, which makes posterior shadowing more pronounced and visible.

According to sonography instrumentation reference:

“Increasing frequency increases attenuation, thereby enhancing acoustic shadowing posterior to highly attenuating structures such as calcifications or bone.”

Therefore, the correct answer is D: Frequency.

—

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.

Sensitivity is the term for an ultrasound system's ability to display low-level echoes. It refers to the system's capacity to detect and accurately display weak echoes returning from tissues. High sensitivity allows the sonographer to visualize structures that produce faint echoes, such as small or low-contrast lesions. This parameter is critical for ensuring that subtle pathological changes are not missed during imaging.References:

ARDMS Sonography Principles and Instrumentation guidelines

"Sonography: Principles and Instruments" by Joan P. Baker and Marveen Craig

Comprehensive and Detailed Explanation From Exact Extract:

Mechanical Index (MI) is proportional to the peak negative pressure and inversely proportional to the square root of frequency. Lowering output power directly decreases the peak pressure, thus reducing MI.

Principles and Instrumentation state:

"Mechanical index decreases with lower output power, reducing the risk of mechanical bioeffects such as cavitation."

Lowering frequency (A) increases MI.

Tissue harmonics (B) improves image quality but does not reduce MI directly.

Increasing gain (D) affects displayed brightness, not acoustic power.

Therefore, the correct answer is C: Decreasing output power.

—