SPI Exam Dumps and Practice Questions

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.

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Comprehensive and Detailed Explanation From Exact Extract:

Interpolation estimates pixel values between scan lines by averaging adjacent data, filling in gaps to create a smoother, more complete image without additional scanning.

According to sonography instrumentation reference:

''Interpolation is a post-processing technique that fills gaps between scan lines by estimating values based on surrounding echoes, improving image smoothness.''

Therefore, the correct answer is D: Interpolation.

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Comprehensive and Detailed Explanation From Exact Extract:

Continuous wave (CW) Doppler utilizes two separate crystals: one constantly transmitting and one constantly receiving. This setup allows CW Doppler to measure very high velocities without aliasing, but at the cost of losing range specificity (no depth resolution).

According to sonography instrumentation reference:

''Continuous wave Doppler uses two separate elements for continuous transmission and reception of sound waves, allowing for detection of very high velocities but without depth specificity.''

Therefore, the correct answer is D: Dedicated transmit and receive crysta

Comprehensive and Detailed Explanation From Exact Extract:

Low PRF reduces the Nyquist limit, making the system more susceptible to aliasing when Doppler shift frequencies exceed this limit.

Principles and Instrumentation state:

'Aliasing occurs when Doppler shifts exceed half the PRF (Nyquist limit). Lowering PRF increases aliasing susceptibility.'

Spectral broadening (A) results from turbulence or poor angle.

Range ambiguity (B) occurs at high PRF.

Dropout (D) refers to signal loss, not aliasing.

Therefore, the correct answer is C: Aliasing.

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Comprehensive and Detailed Explanation From Exact Extract:

Ensemble length, also known as packet size, refers to the number of ultrasound pulses sent along each scan line when performing color Doppler or power Doppler imaging. Increasing the ensemble length allows for more accurate velocity estimation and improved sensitivity to low flow but comes at the expense of decreased frame rate.

Official sonography instrumentation reference states:

''Ensemble length refers to the number of pulses per scan line used in color Doppler imaging. A larger ensemble improves sensitivity to slow flow and provides more accurate frequency (velocity) estimates but reduces temporal resolution.''

Thus, the correct answer is B: Number of pulses along a scan line.

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