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
What happens to the Doppler angle as it approaches 90 degrees relative to blood flow?
Answer: Measured velocity approaches zero regardless of true velocity
The Doppler equation includes the cosine of the angle; at 90°, cos(90°) = 0, so the detected Doppler shift becomes zero regardless of actual blood velocity.
Which transducer type is most commonly used for adult transthoracic echocardiography?
Answer: Phased array
Phased array transducers use electronic steering to create a small footprint with a wide sector image, making them ideal for imaging through narrow intercostal spaces.
In color flow Doppler, the variance map (green) indicates:
Answer: Turbulent or disturbed flow
Green color or color variance in the color flow map indicates turbulent or disturbed flow with multiple velocities present within the sample volume.
The lateral resolution of an ultrasound beam is primarily determined by:
Answer: Beam width at a given depth
Lateral resolution equals the beam width at the depth of the target; objects closer together than the beam width cannot be resolved as separate structures.
Which statement about continuous wave (CW) Doppler is correct?
Answer: It can measure very high velocities without aliasing
CW Doppler continuously transmits and receives without pulsing, so it has no PRF limit and can accurately measure very high velocities without aliasing.
Acoustic shadowing distal to a calcified structure occurs because:
Answer: The structure absorbs and reflects most of the incident sound energy
Dense calcified structures have very high acoustic impedance and absorb or reflect nearly all incident ultrasound, leaving a hypoechoic (shadow) region posterior to the structure.
The 'dead zone' near-field artifact is caused by:
Answer: Transducer ringing after pulse transmission that obscures shallow structures
After each transmitted pulse, the transducer crystals continue to vibrate briefly (ring-down), masking echoes from very shallow structures during this dead zone period.