Ultrasound Physics and Instrumentation Flashcards
7 cards from real CCI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Ultrasound Physics and Instrumentation flashcards as text
The mechanical index (MI) displayed on an ultrasound machine is most closely associated with the risk of:
Answer: Cavitation and non-thermal mechanical bioeffects
MI = peak negative pressure / √frequency; higher MI values indicate greater potential for cavitation and non-thermal mechanical bioeffects.
When sector width is reduced on a 2D echocardiographic image, the primary benefit is:
Answer: Increased frame rate
A narrower sector requires fewer scan lines per frame, allowing the system to update the image more frequently and increasing frame rate.
Which artifact causes a structure to appear duplicated and displaced laterally in an ultrasound image?
Answer: Refraction artifact (ghost image)
Refraction at curved tissue interfaces bends the sound beam, causing the machine to misplace the returning echo and display a duplicate or displaced ghost image.
In the context of transesophageal echocardiography (TEE), the higher image quality compared to transthoracic echo is mainly due to:
Answer: Elimination of chest wall and lung attenuation by placing the probe adjacent to the heart
The esophagus lies directly posterior to the heart, eliminating lung and chest wall attenuation and allowing higher frequency transducers that provide superior resolution.
The Doppler shift frequency is directly proportional to which of the following?
Answer: The velocity of the moving reflector (blood cells)
The Doppler equation shows that Doppler shift = (2 × f × v × cos θ) / c; shift is directly proportional to velocity of the reflector.
Increasing pulse repetition frequency (PRF) in pulsed wave Doppler will:
Answer: Increase the Nyquist limit, allowing measurement of higher velocities before aliasing
Higher PRF means more samples per second; since the Nyquist limit = PRF/2, higher PRF raises the aliasing threshold and allows measurement of faster velocities.
A 'comet-tail' artifact seen posterior to a small hyperechoic focus is most likely caused by:
Answer: Reverberation between closely spaced strong reflectors creating a bright tapering trail
Comet-tail artifacts arise from reverberation between the near and far walls of a small metallic or calcified reflector, producing a bright tapering trail of echoes distal to the focus.