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CAQ-CVTS practice questions

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Question 1Vascular Physics and Instrumentation

In a pulsed-wave Doppler system, what does the pulse repetition frequency (PRF) primarily determine regarding the maximum detectable velocity?

  1. The axial resolution of the B-mode image
  2. The wall filter cutoff frequency
  3. The Nyquist limit and therefore the aliasing threshold Correct answer.
  4. The thermal index of the transducer

Explanation

PRF sets the Nyquist limit, which equals half the PRF; velocities producing Doppler shifts above that limit alias. Because maximum detectable velocity scales directly with PRF, increasing PRF raises the aliasing threshold but reduces the maximum unambiguous depth.

Question 2Vascular Physics and Instrumentation

A continuous-wave Doppler probe insonates a vessel with a 5 MHz beam and detects a Doppler shift of 3.2 kHz. Using the Doppler equation with a 60-degree angle and assumed soft-tissue speed of 1540 m/s, which velocity is closest?

  1. 0.99 m/s Correct answer.
  2. 1.97 m/s
  3. 3.94 m/s
  4. 0.49 m/s

Explanation

The Doppler equation gives v = (fd × c) / (2 × f0 × cos θ). Substituting 3200 Hz, 1540 m/s, 5×10^6 Hz and cos 60° = 0.5 yields approximately 0.99 m/s.

Question 3Vascular Physics and Instrumentation

Which statement correctly describes how the Doppler angle affects the measured velocity when the true velocity is held constant?

  1. The measured shift decreases as the angle approaches 90 degrees Correct answer.
  2. The measured shift is independent of angle below 60 degrees
  3. The measured shift is maximal at 90 degrees and minimal at 0 degrees
  4. The measured shift increases as the angle approaches 90 degrees

Explanation

The cosine of the Doppler angle scales the measured frequency shift, and cosine falls toward zero as the angle approaches 90 degrees. Thus a near-perpendicular beam underestimates velocity, while angles near 0 degrees (parallel to flow) maximize the shift.

Question 4Vascular Physics and Instrumentation

Color Doppler shows a vessel filled with a mosaic of red and blue pixels that change rapidly frame to frame, with no clear flow direction. If this pattern is due to color aliasing, which adjustment most directly addresses it?

  1. Lower the color PRF to increase sensitivity
  2. Increase the color PRF or increase the displayed velocity scale Correct answer.
  3. Increase the color gain until the vessel is uniformly filled
  4. Decrease the wall filter to zero

Explanation

When the mosaic is caused by color aliasing, the detected Doppler shifts exceed the Nyquist limit. Raising the color PRF, represented by a higher displayed velocity scale, raises that limit and reduces aliasing. Gain and wall-filter adjustments do not correct the underlying sampling limit.

Question 5Vascular Physics and Instrumentation

Which transducer design produces the narrowest slice thickness (elevation resolution) at a given depth?

  1. A 1.5-dimensional array with electronic elevation focusing Correct answer.
  2. A linear array with a short elevation aperture
  3. A mechanical probe with a weakly focused lens
  4. A phased array with electronic elevation focusing

Explanation

Slice thickness is governed by the elevation (out-of-plane) beam width. A 1.5D or 2D array uses multiple elevation elements with electronic focusing, giving a narrower slice than fixed mechanical lenses or single-row arrays.

Question 6Vascular Physics and Instrumentation

What is the primary effect of increasing the transmit frequency on spatial resolution and penetration?

  1. Has no effect on either resolution or attenuation
  2. Improves axial resolution and reduces penetration Correct answer.
  3. Improves lateral resolution only, with no change in attenuation
  4. Worsens axial resolution and increases penetration

Explanation

Higher frequency shortens wavelength, improving axial resolution, but attenuation in tissue increases roughly with frequency, so penetration decreases. This trade-off drives frequency selection based on depth of interest.

Question 7Vascular Physics and Instrumentation

A sonographer increases the wall filter on a spectral Doppler tracing of a low-velocity venous flow. What is the expected result?

  1. The sample volume depth increases
  2. Low-velocity components near the baseline are removed Correct answer.
  3. The peak velocity reading increases
  4. Aliasing is eliminated

Explanation

The wall filter is a high-pass filter that removes low-frequency Doppler shifts from moving walls and slow flow. Raising it eliminates signals near the baseline, which can hide genuine low-velocity venous flow.

Question 8Vascular Physics and Instrumentation

Which factor most limits the maximum depth at which pulsed-wave Doppler can operate without range ambiguity?

  1. The transducer element count
  2. The display frame rate
  3. The color box width
  4. The pulse repetition frequency Correct answer.

Explanation

In pulsed Doppler, echoes must return before the next pulse is emitted, so maximum depth is inversely related to PRF. High PRF improves velocity detection but shortens the unambiguous range.

Question 9Vascular Physics and Instrumentation

A vessel with a 4 mm diameter shows a parabolic velocity profile in a steady-flow phantom. Compared with the centerline velocity, the mean spatial velocity across the lumen is approximately:

  1. Twice the centerline velocity
  2. One-half of the centerline velocity Correct answer.
  3. Equal to the centerline velocity
  4. One-quarter of the centerline velocity

Explanation

For fully developed laminar flow in a circular tube, the velocity profile is parabolic and the cross-sectional mean is half the centerline maximum. This relationship underpins volume-flow calculations from mean velocity.

Question 10Vascular Physics and Instrumentation

Which Doppler modality is least affected by aliasing because it does not rely on discrete range gating?

  1. Duplex color Doppler
  2. Continuous-wave Doppler Correct answer.
  3. Power Doppler
  4. Pulsed-wave Doppler

Explanation

Continuous-wave Doppler transmits and receives continuously, so it has no Nyquist limit from pulse repetition and can measure very high velocities without aliasing. Its trade-off is the loss of depth discrimination.

Question 11Vascular Physics and Instrumentation

Power Doppler imaging is best described as displaying which parameter of the Doppler signal?

  1. Integrated Doppler signal amplitude Correct answer.
  2. Mean velocity direction
  3. Peak systolic frequency shift
  4. Spectral broadening width

Explanation

Power Doppler encodes the integrated power (amplitude) of the Doppler signal rather than mean velocity or direction. This gives greater sensitivity to slow flow but sacrifices directional information.

Question 12Vascular Physics and Instrumentation

Which artifact appears as a mirrored vessel on the opposite side of a strong reflector such as the diaphragm?

  1. Reverberation
  2. Mirror-image artifact Correct answer.
  3. Refraction artifact
  4. Shadowing

Explanation

Mirror-image artifact occurs when a strong reflector redirects echoes so a structure appears duplicated on the far side of the reflector. It is common near the diaphragm and can mimic a second vessel.

Question 13Vascular Physics and Instrumentation

A spectral Doppler tracing shows spectral broadening across the entire cardiac cycle. Which technical factor most likely explains this finding?

  1. Sample volume too large relative to the vessel Correct answer.
  2. Wall filter set too low for venous flow
  3. PRF set too high for the velocity
  4. Transducer frequency too low for the depth

Explanation

A large sample volume captures a wide range of velocities across the velocity profile, producing spectral broadening. Reducing the sample volume to fit within the vessel narrows the spectral trace.

Question 14Vascular Physics and Instrumentation

How does increasing the number of focal zones affect the B-mode image?

  1. Improves lateral resolution over a wider depth range and lowers frame rate Correct answer.
  2. Reduces penetration and increases frame rate
  3. Improves axial resolution and increases frame rate
  4. Has no effect on frame rate but worsens contrast

Explanation

Multiple focal zones sharpen the beam over a greater depth range, improving lateral resolution, but each zone requires additional transmit-receive cycles, reducing frame rate. This is a classic resolution versus temporal trade-off.

Question 15Vascular Physics and Instrumentation

Which parameter of the ultrasound pulse determines the axial resolution?

  1. Beam width at the focus
  2. Spatial pulse length Correct answer.
  3. Acoustic power output
  4. Pulse repetition frequency

Explanation

Axial resolution equals half the spatial pulse length, which depends on wavelength and the number of cycles per pulse. Shorter pulses and higher frequencies improve the ability to separate reflectors along the beam.

Question 16Vascular Physics and Instrumentation

A time-gain compensation (TGC) curve is set too high in the far field of a vascular image. What is the most likely consequence?

  1. Reduction of aliasing in color Doppler
  2. Improved axial resolution at depth
  3. Uniform brightening of the near field
  4. Excessive amplification producing noise and loss of far-field detail Correct answer.

Explanation

TGC compensates for depth-dependent attenuation; setting it too high in the far field over-amplifies deep echoes, adding noise and degrading contrast. Correct TGC keeps similar tissue echogenicity across depths.

Question 17Vascular Physics and Instrumentation

Which statement about the relationship between frame rate and color box size is correct?

  1. Enlarging the color box increases frame rate
  2. Color box size has no effect on frame rate
  3. Frame rate depends only on transducer frequency
  4. Enlarging the color box decreases frame rate Correct answer.

Explanation

A larger color box requires more scan lines and more processing per frame, lowering frame rate. Reducing the box to the region of interest improves temporal resolution.

Question 18Vascular Physics and Instrumentation

A high-PRF pulsed Doppler setting is used to resolve a high-velocity jet. What trade-off is accepted?

  1. Loss of axial resolution
  2. Increased wall filter requirement
  3. Reduced Doppler angle accuracy
  4. Range ambiguity from multiple sample gates Correct answer.

Explanation

High-PRF pulsed Doppler samples faster to raise the Nyquist limit but allows echoes from more than one depth to be received per cycle, creating range ambiguity. The displayed velocity may originate from an unintended gate.

Question 19Vascular Physics and Instrumentation

Which of the following best explains why a calcified plaque produces acoustic shadowing?

  1. The plaque generates harmonic frequencies
  2. The plaque has a lower attenuation than soft tissue
  3. The plaque refracts the beam away from the region
  4. The plaque reflects and absorbs most of the sound, leaving little energy beyond it Correct answer.

Explanation

Calcification has a large acoustic impedance mismatch and high attenuation, so most energy is reflected or absorbed at the surface. The region deep to the plaque receives little sound and appears dark.

Question 20Vascular Physics and Instrumentation

When harmonic imaging is used, which frequency is received to form the image?

  1. Half the transmitted fundamental frequency
  2. A frequency independent of the transmitted beam
  3. The transmitted fundamental frequency
  4. Twice the transmitted fundamental frequency Correct answer.

Explanation

Tissue harmonic imaging receives the second harmonic, approximately twice the transmit frequency, generated by nonlinear propagation. Because harmonics arise mainly in the main beam, side-lobe and clutter artifacts are reduced.

Question 21Vascular Physics and Instrumentation

Two vessels lie at the same depth, but one shows a color Doppler signal and the other does not despite similar flow. Which factor most likely explains the difference?

  1. The Doppler angle relative to the beam differs between vessels Correct answer.
  2. The display depth is the same
  3. The PRF is identical for both
  4. The wall filter is set to zero

Explanation

Doppler shift depends on the cosine of the angle between the beam and flow. A vessel oriented near 90 degrees to the beam produces little or no detectable shift, so color may be absent despite real flow.

Question 22Vascular Physics and Instrumentation

Which processing step in a modern ultrasound system converts received radiofrequency echoes into the displayed B-mode image?

  1. Doppler demodulation and wall filtering
  2. Time-gain compensation and frame averaging
  3. Harmonic subtraction and pulse inversion
  4. Beamforming, envelope detection, and scan conversion Correct answer.

Explanation

B-mode formation involves beamforming to align echoes, envelope detection to extract amplitude, and scan conversion to map data to the display geometry. These steps produce the gray-scale image.

Question 23Vascular Physics and Instrumentation

Which condition favors the use of a lower transmit frequency during a vascular examination?

  1. Imaging a deep abdominal aorta in an obese patient Correct answer.
  2. Measuring a high-velocity stenosis near the skin surface
  3. Imaging a superficial carotid artery in a thin patient
  4. Requiring the best possible axial resolution

Explanation

Lower frequency penetrates deeper tissue because attenuation is reduced, making it preferable for deep structures in obese patients. The cost is poorer axial resolution.

Question 24Vascular Physics and Instrumentation

What is the main advantage of a linear array transducer for vascular imaging?

  1. The lowest possible cost per element
  2. Electronic steering over a large sector
  3. A rectangular image with uniform high resolution in the near field Correct answer.
  4. A wide field of view at great depth

Explanation

A linear array fires elements in sequence to produce a rectangular field with uniform, high resolution near the surface, ideal for superficial vessels. Its limitation is a narrower field at depth.

Question 25Cerebrovascular Testing and Interpretation

A continuous-wave Doppler probe insonates the internal carotid artery. Which Doppler waveform finding is most characteristic of a hemodynamically significant stenosis at that site?

  1. Spectral broadening limited to the diastolic phase only
  2. Symmetric broadening in both internal and external carotid arteries
  3. Marked spectral broadening with loss of the systolic window Correct answer.
  4. Broadening confined to the spectral window with a normal peak systolic velocity

Explanation

A hemodynamically significant stenosis produces turbulent, high-velocity flow that fills the spectral window, so the clear systolic window disappears and spectral broadening becomes marked. Broadening confined to a normal window, or isolated diastolic broadening, does not indicate significant stenosis.

Question 26Cerebrovascular Testing and Interpretation

During a carotid duplex examination, the technologist cannot obtain a Doppler signal from the internal carotid artery despite an apparently patent lumen on B-mode. Which technical factor should be checked first?

  1. Color box steering direction only
  2. Patient's fasting status
  3. Doppler sample volume depth and angle of insonation Correct answer.
  4. Room lighting level

Explanation

Absent Doppler signal with a patent lumen usually reflects incorrect sample volume depth or an inappropriate Doppler angle. Checking depth and angle of insonation is the first technical step before assuming true occlusion.

Question 27Cerebrovascular Testing and Interpretation

Which parameter is used as the primary criterion for grading internal carotid artery stenosis by duplex ultrasound?

  1. Mean arterial pressure
  2. Resistive index
  3. Peak systolic velocity Correct answer.
  4. Pulsatility index

Explanation

Peak systolic velocity is the primary duplex criterion used to grade internal carotid stenosis, with supporting ratios such as ICA/CCA peak systolic ratio. Resistive and pulsatility indices describe waveform shape rather than stenosis severity.

Question 28Cerebrovascular Testing and Interpretation

In a normal carotid duplex examination, which waveform pattern is expected from the external carotid artery?

  1. Low-resistance waveform with continuous diastolic flow
  2. Reverse flow throughout the cardiac cycle
  3. High-resistance waveform with low or absent diastolic flow Correct answer.
  4. Monophasic waveform with no systolic peak

Explanation

The external carotid artery supplies the face and scalp, a high-resistance vascular bed, so its waveform shows a sharp systolic peak with low or absent diastolic flow. The internal carotid supplies the low-resistance cerebral circulation and shows continuous diastolic flow.

Question 29Cerebrovascular Testing and Interpretation

Which vessel is typically identified by its position medial to the internal carotid artery and by branches in the neck?

  1. Subclavian artery
  2. Internal carotid artery
  3. Vertebral artery
  4. External carotid artery Correct answer.

Explanation

The external carotid artery lies anteromedial to the internal carotid and gives off cervical branches, which helps distinguish the two vessels. The internal carotid has no cervical branches and is usually posterolateral.

Question 30Cerebrovascular Testing and Interpretation

A vertebral artery waveform shows a brisk systolic peak with continuous forward diastolic flow. Which statement best describes this finding?

  1. It indicates subclavian steal
  2. It indicates vertebral artery occlusion
  3. It indicates a high-resistance external carotid pattern
  4. It is a normal low-resistance vertebral waveform Correct answer.

Explanation

The vertebral artery supplies the low-resistance posterior cerebral circulation, so a normal waveform has a systolic peak with continuous forward diastolic flow. Occlusion would show no flow, and subclavian steal would show reversed or alternating flow.

Question 31Cerebrovascular Testing and Interpretation

Which finding on duplex ultrasound most strongly suggests a near-occlusion (string sign) of the internal carotid artery?

  1. Absent color flow with a normal spectral waveform
  2. Very high peak systolic velocity with a narrow color lumen
  3. Normal peak systolic velocity with a wide color lumen
  4. Low peak systolic velocity with a thin color flow channel and distal dampening Correct answer.

Explanation

Near-occlusion can paradoxically show low peak systolic velocity because flow is severely limited through a tiny residual lumen, with a thin color channel and dampened distal waveform. Extremely high velocity is more typical of a severe but not near-occlusive stenosis.

Question 32Cerebrovascular Testing and Interpretation

A patient has a peak systolic velocity of 260 cm/s in the internal carotid artery with an ICA/CCA ratio of 4.2. How should this be interpreted?

  1. Complete occlusion
  2. Severe stenosis, likely 70% or greater Correct answer.
  3. Mild stenosis, less than 50%
  4. Normal velocity

Explanation

A peak systolic velocity above roughly 250 cm/s with an ICA/CCA ratio above 4 is consistent with severe stenosis of 70% or greater. Mild stenosis would show much lower velocities, and occlusion would show no flow.

Question 33Cerebrovascular Testing and Interpretation

Which condition can produce a falsely elevated peak systolic velocity in the internal carotid artery?

  1. Contralateral carotid occlusion with compensatory flow Correct answer.
  2. Systemic hypotension
  3. Severe distal intracranial stenosis
  4. Atherosclerotic plaque with heavy calcification causing acoustic shadowing

Explanation

Contralateral occlusion can increase flow demand through the patent carotid, raising peak systolic velocity and potentially overestimating stenosis. Distal stenosis, hypotension, and heavy calcification tend to reduce or obscure the measured velocity rather than elevate it.

Question 34Cerebrovascular Testing and Interpretation

A carotid duplex shows a focal color aliasing region in the internal carotid artery. What is the most appropriate next step?

  1. Increase the color velocity scale and obtain spectral Doppler through the region Correct answer.
  2. Assume the aliasing represents artifact and ignore it
  3. Reduce the color velocity scale further to enhance aliasing
  4. Switch immediately to continuous-wave Doppler only

Explanation

Focal aliasing may represent true high-velocity flow from stenosis, so the color scale should be increased to reduce aliasing and spectral Doppler should be obtained through the region. Ignoring the finding risks missing significant stenosis.

Question 35Cerebrovascular Testing and Interpretation

Which finding is most consistent with a hemodynamically significant stenosis in the vertebral artery origin?

  1. Focal velocity increase with post-stenotic turbulence at the V1 segment Correct answer.
  2. Uniform low velocity throughout the vertebral artery
  3. Absent diastolic flow in the vertebral artery
  4. Reversal of flow in the contralateral vertebral artery

Explanation

A significant vertebral origin stenosis produces a focal velocity increase with turbulence just beyond the narrowing. Uniform low velocity or absent diastolic flow does not localize a focal stenosis.

Question 36Cerebrovascular Testing and Interpretation

A patient presents with transient monocular blindness on the right side. Which carotid finding is most relevant to this symptom?

  1. Right external carotid artery stenosis
  2. Left internal carotid artery stenosis
  3. Bilateral vertebral artery hypoplasia
  4. Right internal carotid artery stenosis Correct answer.

Explanation

Transient monocular blindness (amaurosis fugax) is typically caused by emboli from ipsilateral carotid disease affecting the ophthalmic circulation. Right-sided symptoms therefore point to right internal carotid artery stenosis.

Question 37Cerebrovascular Testing and Interpretation

Which duplex finding suggests a subclavian steal phenomenon?

  1. High-resistance flow in the ipsilateral internal carotid artery
  2. Increased diastolic flow in the ipsilateral vertebral artery
  3. Reversed or alternating flow in the ipsilateral vertebral artery Correct answer.
  4. Absent flow in the contralateral vertebral artery

Explanation

Subclavian steal occurs when proximal subclavian stenosis causes blood to flow retrogradely down the vertebral artery to supply the arm. Duplex shows reversed or alternating vertebral flow on the affected side.

Question 38Cerebrovascular Testing and Interpretation

Which factor most limits the accuracy of duplex ultrasound in the very proximal internal carotid artery near the bifurcation?

  1. Patient's hair color
  2. Use of a linear transducer
  3. Deep location and vessel tortuosity Correct answer.
  4. Presence of continuous diastolic flow

Explanation

Very proximal segments near the bifurcation can be deep or tortuous, making angle correction and insonation difficult and reducing measurement accuracy. Hair color, transducer type, and diastolic flow pattern do not limit accuracy in this way.

Question 39Cerebrovascular Testing and Interpretation

A carotid duplex demonstrates a peak systolic velocity of 120 cm/s in the internal carotid artery with an ICA/CCA ratio of 1.8 and no plaque. How should this be categorized?

  1. Near-occlusion
  2. Normal to mild disease Correct answer.
  3. Complete occlusion
  4. Severe stenosis

Explanation

A peak systolic velocity of 120 cm/s with a ratio of 1.8 and no plaque falls within the normal to mild range. Severe stenosis would require much higher velocities, and occlusion or near-occlusion would show absent or markedly reduced flow.

Question 40Cerebrovascular Testing and Interpretation

Which waveform change in the internal carotid artery distal to a severe stenosis is expected?

  1. Increased peak systolic velocity with a sharp upstroke
  2. Reversal of diastolic flow
  3. Dampened systolic peak with prolonged acceleration time Correct answer.
  4. Normal triphasic waveform

Explanation

A severe proximal stenosis reduces distal pressure and flow, producing a dampened, tardus-parvus waveform with a prolonged acceleration time. High velocity with a sharp upstroke occurs at the stenosis itself, not distally.

Question 41Cerebrovascular Testing and Interpretation

Which parameter helps distinguish a high-resistance external carotid waveform from an internal carotid waveform when both are insonated near the bifurcation?

  1. Doppler gain setting
  2. Color box size
  3. Peak systolic velocity alone
  4. Presence of a temporal tap response Correct answer.

Explanation

A temporal tap produces oscillations in the external carotid waveform because the superficial temporal artery is a branch of the ECA. This maneuver helps separate ECA from ICA when anatomy is ambiguous.

Question 42Cerebrovascular Testing and Interpretation

A patient has a history of neck radiation. Which technical consideration is most important during carotid duplex?

  1. Use only continuous-wave Doppler
  2. Assume velocities are falsely low and multiply by a correction factor
  3. Skip color Doppler entirely
  4. Anticipate altered anatomy and possible acoustic attenuation from fibrosis Correct answer.

Explanation

Neck radiation can cause fibrosis and altered anatomy, making vessels harder to insonate and attenuating the acoustic signal. The technologist should anticipate these difficulties and adjust technique rather than apply arbitrary corrections.

Question 43Cerebrovascular Testing and Interpretation

Which duplex measurement is most useful for confirming that a stenosis is hemodynamically significant when peak systolic velocity is equivocal?

  1. Vessel diameter on B-mode alone
  2. Patient's heart rate
  3. Resistive index of the external carotid
  4. ICA/CCA peak systolic velocity ratio Correct answer.

Explanation

The ICA/CCA peak systolic velocity ratio provides an internal reference that helps confirm significance when absolute velocity is equivocal. B-mode diameter alone, ECA resistive index, and heart rate do not reliably confirm hemodynamic significance.

Question 44Cerebrovascular Testing and Interpretation

A carotid duplex reveals a plaque with a large anechoic region and irregular surface in the internal carotid artery. Which characteristic is most associated with increased embolic risk?

  1. Irregular, ulcerated surface Correct answer.
  2. Vessel tortuosity
  3. Small focal calcification
  4. Uniformly echogenic and smooth surface

Explanation

Irregular or ulcerated plaque surfaces are associated with a higher risk of embolization and ischemic events. Smooth, uniformly echogenic plaque and small calcifications are less strongly linked to embolic risk.

Question 45Cerebrovascular Testing and Interpretation

Which finding on duplex ultrasound would most likely be seen in a patient with a documented carotid dissection?

  1. A normal triphasic waveform throughout
  2. Symmetric high-resistance flow in both carotids
  3. A focal high-velocity stenosis at the bifurcation
  4. A tapered stenosis with an intimal flap and reduced distal flow Correct answer.

Explanation

Carotid dissection typically produces a tapered narrowing, sometimes with a visible intimal flap, and reduced distal flow. A focal bifurcation stenosis or symmetric high-resistance flow does not describe dissection.

Question 46Cerebrovascular Testing and Interpretation

A patient with a suspected carotid-cavernous fistula undergoes carotid duplex. Which finding is most consistent with this diagnosis?

  1. Reversed flow in the external carotid artery
  2. Normal triphasic flow in the common carotid artery
  3. Absent diastolic flow in the internal carotid artery
  4. High-velocity, low-resistance flow in the internal carotid artery with increased diastolic flow Correct answer.

Explanation

A carotid-cavernous fistula creates a low-resistance shunt, producing high-velocity flow with increased diastolic flow in the feeding internal carotid artery. High-resistance patterns and normal triphasic flow do not fit this physiology.

Question 47Cerebrovascular Testing and Interpretation

A duplex examination shows a peak systolic velocity of 180 cm/s in the internal carotid artery with a ratio of 2.5 and moderate plaque. Which interpretation is most appropriate?

  1. Severe stenosis of 70% or greater
  2. Complete occlusion
  3. Moderate stenosis, approximately 50-69% Correct answer.
  4. Normal vessel

Explanation

A peak systolic velocity around 180 cm/s with a ratio near 2.5 and moderate plaque is consistent with a moderate stenosis of roughly 50-69%. Severe stenosis would show higher velocities and ratios.

Question 48Cerebrovascular Testing and Interpretation

Which combination of findings best supports a diagnosis of internal carotid artery occlusion rather than near-occlusion?

  1. High-velocity flow with a focal color aliasing region
  2. Very low velocity with a thin color channel and dampened distal flow
  3. Absent color and spectral flow in the ICA with a normal-appearing distal waveform from collateral supply Correct answer.
  4. Reversed flow in the external carotid artery

Explanation

True occlusion shows no detectable flow in the ICA, while the distal segment may fill via collaterals. Near-occlusion instead shows a thin residual channel with low velocity and dampened distal flow.

Question 49Cerebrovascular Testing and Interpretation

A patient has a peak systolic velocity of 90 cm/s in the internal carotid artery but a markedly dampened waveform with prolonged acceleration time. What is the most likely explanation?

  1. Artifact from excessive Doppler gain
  2. Normal variation in a young patient
  3. Proximal common carotid or aortic arch stenosis reducing inflow Correct answer.
  4. Focal severe stenosis at the insonated segment

Explanation

A low velocity with a dampened, tardus-parvus waveform suggests reduced inflow from a proximal lesion such as common carotid or aortic arch stenosis. A focal stenosis at the insonated site would produce high velocity, not low velocity.

Question 50Cerebrovascular Testing and Interpretation

During carotid duplex, the ophthalmic artery is interrogated with the probe. Which Doppler finding indicates that flow in the ophthalmic artery has reversed direction?

  1. The signal is pulsatile and synchronous with the contralateral ophthalmic artery
  2. The waveform shows a high-resistance signal with a sharp systolic upstroke and absent diastolic flow
  3. The waveform is continuous and non-pulsatile with low velocity
  4. The spectral trace lies above the baseline and shows flow directed away from the probe toward the orbit Correct answer.

Explanation

The ophthalmic artery normally carries blood from the internal carotid toward the orbit, so its flow is directed toward the probe and displayed above the baseline when the vessel is insonated from the orbital approach. Reversal of ophthalmic flow, seen as a trace below the baseline, is an indirect sign of severe ipsilateral ICA stenosis or occlusion with collateral supply from the external carotid. Recognizing the direction relative to the baseline is the key step.