SPI Practice Questions
Prepare for SPI with more than an answer.
- Exam fee
- $250 USD
- Level
- Entry-Level Physics Requirement
- Valid for
- Lifetime (when paired with specialty certification)
Domains covered on the exam 5
- Perform Ultrasound Examinations23%
- Manage Ultrasound Transducers7%
- Optimize Sonographic Images26%
- Apply Doppler Concepts34%
- Provide Clinical Safety & Quality Assurance10%
- 1
The Mechanical Index (MI) displayed on the ultrasound system is an indicator of the potential for what type of bioeffect?
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Correct answer: B
The Mechanical Index (MI) is a calculated value that estimates the potential for non-thermal bioeffects, specifically cavitation. Cavitation is the production and interaction of microscopic gas bubbles in tissue due to the pressure fluctuations of the sound wave. The MI is proportional to the peak negative pressure and inversely proportional to the square root of the frequency. Tissue heating is indicated by the Thermal Index (TI).
- 2
A phased array transducer steers the ultrasound beam by applying small time delays to the electrical signals exciting the individual crystal elements. This process is known as:
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Correct answer: C
Phasing is the technique of applying minute time delays (on the order of nanoseconds) to the excitation pulses sent to each element in an array transducer. By controlling the pattern of these delays, the resulting wavefront can be steered in different directions and focused at various depths. This is the fundamental principle behind electronic beam steering in phased array transducers.
- 3
What is the primary determinant of the propagation speed of sound in a medium?
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Correct answer: C
The propagation speed of sound is an intrinsic property of the medium through which it travels. It is determined solely by the medium's stiffness (or bulk modulus) and density. Sound travels faster in stiffer media and slower in denser media. It is not affected by the frequency or intensity of the sound wave itself.
- 4
A sonographer is adjusting the Time Gain Compensation (TGC) controls. What is the primary purpose of this function?
Below is an ASCII diagram representing the TGC curve on a display:
Gain (dB) ^ | /----- | / | / | / |-----/ +------------------> Depth (cm) Near Mid FarShow answer details
Correct answer: B
As the ultrasound beam travels through tissue, it weakens or attenuates. This means echoes from deeper structures are weaker than those from superficial structures. Time Gain Compensation (TGC), or Depth Gain Compensation (DGC), allows the sonographer to selectively amplify the echoes based on their depth of origin. The goal is to create an image with uniform brightness from the near field to the far field by counteracting the effects of attenuation.
- 5
The Doppler shift frequency is directly proportional to which of the following? (Select ALL that apply)
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Correct answer: A, B, D
The Doppler equation shows that the Doppler shift is directly proportional to the operating frequency of the transducer. Higher frequency transducers will produce a larger Doppler shift for the same blood flow velocity.
The Doppler equation demonstrates a direct relationship between the velocity of the red blood cells and the magnitude of the Doppler shift. Faster flow produces a larger shift.
The Doppler shift is directly proportional to the cosine of the angle between the sound beam and the direction of blood flow. The shift is maximal when the angle is 0 degrees (cosine=1) and zero when the angle is 90 degrees (cosine=0).
- 6
A sonographer is performing a carotid artery duplex exam and observes spectral broadening in the internal carotid artery waveform. Which of the following is the LEAST likely cause for this observation?
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Correct answer: C
Spectral broadening is the filling of the spectral window, indicating a wide range of velocities. A large sample volume, high gain, and turbulent flow (stenosis) are all common causes. However, a 90-degree angle of insonation would result in no detectable Doppler shift, producing a flat line or no signal at all, not spectral broadening. Therefore, it is the least likely cause.
- 7
While imaging the liver, a sonographer encounters a highly echogenic, well-defined mass that causes a significant decrease in the amplitude of the sound beam, resulting in a dark area posterior to the structure. This artifact is best described as:
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Correct answer: C
Acoustic shadowing occurs when a sound beam encounters a highly attenuating or reflecting structure (like a calcification or gallstone). The structure blocks the sound from passing through, creating a signal void or 'shadow' deep to it. Enhancement is the opposite, where a weakly attenuating structure causes increased brightness behind it. Reverberation involves multiple echoes between strong reflectors.
- 8
The acoustic impedance of a medium is a critical factor in determining the amount of reflection at an interface. It is calculated as the product of which two properties of the medium?
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Correct answer: B
Acoustic impedance (Z) is an intrinsic property of a medium and is defined as the product of the medium's density (ρ) and its propagation speed (c). The formula is Z = ρc. The greater the difference in acoustic impedance between two media, the stronger the reflection at their boundary.
- 9
A sonographer is using a transducer with a wide bandwidth. Which of the following characteristics is most associated with this type of transducer?
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Correct answer: B
Wide bandwidth transducers have a low quality factor (Q factor), meaning they produce a wide range of frequencies around the center frequency. This is achieved using a backing material that dampens the crystal's ringing, resulting in a short pulse duration and a short spatial pulse length (SPL). A short SPL is essential for good axial resolution.
- 10
In accordance with the ALARA (As Low As Reasonably Achievable) principle, which TWO of the following actions should a sonographer prioritize to minimize patient exposure to ultrasound energy? (Select TWO)
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Correct answer: A, C
Increasing gain amplifies the returning echoes without increasing the transmitted energy, thus having no impact on patient exposure. This should always be done before increasing output power.
Total exposure is a function of intensity and time. Minimizing the duration of the exam, especially dwelling in one spot, directly reduces the patient's overall exposure to ultrasound energy.
