ARRT Vascular Sonography Study Guide

1. Confirm the patient and examination

Before choosing views, match two patient identifiers against the request and the patient record. Then confirm the vascular territory, side, and clinical question. A venous examination for suspected thrombosis answers a different question from an arterial examination for reduced perfusion, even when both involve the same leg. Ask when symptoms began and where they occur; that history can expose an order discrepancy, but it does not authorize changing the requested study yourself. If the request and history conflict, resolve the intended examination with the ordering team and record the clarification. Accurate identification also keeps images, measurements, and any urgent communication attached to the correct patient. The American Registry of Radiologic Technologists is a credentialing organization; these bedside checks are part of performing a defensible vascular examination.

Worked example: The request specifies a left leg venous duplex, but the patient points to new right calf pain. You match name and date of birth to the request, confirm that the patient means the right calf, and pause before scanning. The ordering team clarifies that the intended study is right sided and updates the request. Record that clarification and label every acquired image right leg.

Watch the distinction: A patient's symptom location does not silently replace the ordered laterality. Scanning the painful side without resolving the mismatch risks an incorrectly labeled or unauthorized examination.

Reference: [1]

2. Build a useful vascular history

A focused history tells you where to look and how to interpret anatomy that no longer follows the usual route. Establish symptom onset, location, triggers, and change over time. Ask about prior thrombosis, bypass, stenting, endarterectomy, access surgery, and relevant imaging, then identify the treated segment and its inflow and outflow. Medications such as anticoagulants may affect clinical context but do not prove that a vessel is patent or free of thrombus. Diabetes, smoking history, and kidney disease can shape the differential and the reliability of physiologic tests. Compare prior images when available because a stable altered waveform differs from a newly changed one. Keep the history tied to the requested clinical question, and document the source of important details when records and patient recollection differ.

Worked example: A patient reports new calf pain and a previous popliteal bypass. The operative record describes a graft from the distal femoral artery to the below-knee popliteal artery. You locate both anastomoses, trace the superficial conduit, and sample native inflow, graft, and runoff. An unfamiliar channel alongside the native artery is therefore labeled as graft, while the painful region and distal flow receive targeted assessment.

Watch the distinction: A surgically created conduit can resemble a native vessel in one image. Labeling it from position alone can hide an anastomotic lesion or misplace a velocity measurement.

3. Explain and adapt the examination

Explain what the examination will feel like and which movements help answer the question. For venous imaging, the patient may feel brief probe pressure during compression; arterial Doppler may require stillness or a short breath hold. Describe these steps before touching or repositioning the patient, expose only the area needed, and ask about pain, breathing difficulty, and mobility. Position changes should preserve the diagnostic purpose: a different window may still show a vessel, but a segment that cannot be compressed has not received the same direct assessment as one that can. Use supports, shorter intervals, and assistance when needed. If the adapted examination leaves a gap, name the affected vessel segment and the reason in the technical record so the interpreting clinician can judge what remains uncertain.

Worked example: A patient becomes breathless while supine during a leg venous study. With the patient supported in a tolerable reclined position, you obtain serial compression images of accessible femoral and popliteal segments and add color and spectral observations where useful. The proximal thigh remains inaccessible. You record the position, the segments examined, and that the proximal thigh could not be adequately assessed.

Watch the distinction: A comfortable alternate position does not guarantee an equivalent examination. If pain or positioning prevents adequate compression, a color-filled image alone should not be recorded as complete exclusion of thrombus.

4. Prevent contact transmission

Contact precautions follow the way the transducer and its accessories are used. Perform hand hygiene before and after patient contact, use gloves when contact with blood, drainage, or nonintact skin is possible, and keep clean controls and supplies away from contaminated gloves. A probe cover reduces exposure but can tear or become contaminated during removal; it never replaces cleaning. After use, remove visible soil first because retained material interferes with disinfection. Apply the disinfection level appropriate to the probe's contact with intact skin, nonintact skin, or mucous membranes, using the device and disinfectant instructions. Clean shared equipment such as cables and the bed as indicated. The reasoning sequence is exposure, containment, cover removal, cleaning, then the required disinfection before the next patient.

Worked example: You scan beside an open leg wound using a covered probe and gloves. After imaging, remove the cover so its soiled outer surface folds inward, discard it, and inspect the probe for gel or contamination. Clean the probe and complete the disinfection required for its contact circumstances before reuse. Remove gloves, perform hand hygiene, and clean touched equipment surfaces.

Watch the distinction: A cover is a barrier with possible leaks and removal contamination. Reusing the probe after peeling off the cover, without cleaning and the appropriate disinfection, leaves a transmission route.

5. Protect the scanning arm

Scanning injuries often arise from repeated force in a fixed posture. A distant target makes the shoulder abduct and the trunk lean, while a deep vessel may tempt sustained pressure through the wrist and fingers. Bring the patient close, set bed height so the scanning arm can remain near the body, and place the monitor where the head can face forward. Support the forearm when practical and use a balanced grip rather than pinching the probe tightly. Move the patient or change sides to improve access before increasing force. For a difficult view, alternate windows and release pressure between acquisitions. These adjustments can improve image quality as well as reduce strain: steadier contact and a less awkward wrist often make the Doppler angle easier to maintain.

Worked example: The abdominal vessel is visible only when you reach across the patient, raising your shoulder and bending your wrist. You move the bed toward you, bring the monitor into your line of sight, and try the nearer scanning side. A small patient turn opens the window. You obtain the Doppler sample with the elbow closer to your torso and release pressure between measurements.

Watch the distinction: A short difficult scan can still involve high force and awkward reach. Holding that posture to save repositioning time increases strain and may make the sample angle less stable.

6. Manage acoustic exposure

Ultrasound output can deposit energy in tissue, and strong acoustic pressure can produce mechanical effects. The displayed thermal index estimates potential heating under a model; the mechanical index relates to the possibility of nonthermal effects. Neither display is a measured patient temperature or a guarantee of safety. Output power and time at one location matter, particularly when a mode repeatedly insonates the same region. Use the lowest output and shortest dwell that still produce the needed diagnostic information. First improve factors that do not require more acoustic output: probe contact, window, depth, focal placement, color box, gain, and Doppler scale. Gain amplifies received signals, whereas output changes transmitted energy. The American Institute of Ultrasound in Medicine provides ultrasound practice resources, while the practical scanning decision remains tied to image adequacy and exposure.

Worked example: A deep artery has patchy color fill. You reduce unnecessary depth, narrow the color box, adjust scale and color gain, and try a better window. The channel becomes visible without raising output. You then acquire a brief spectral sample and move on instead of holding the beam over the same spot while repeatedly testing settings.

Watch the distinction: Turning up receiver gain and increasing transmitted output are different actions. Treating the displayed thermal or mechanical index as an exact patient dose also overstates what those estimates measure.

Reference: [2]

7. Respond to concerning changes

The patient's condition can change faster than an examination can be completed. Watch for new neurologic symptoms, severe pain, faintness, breathing difficulty, or other acute distress, and distinguish these from a technical image problem. When a concerning change occurs, stop the acquisition, keep the patient safe, and summon the designated clinical response immediately. Give a concise account of the new symptom, its onset, the patient's current condition, and any relevant observations; the receiving clinician decides diagnosis and treatment. Significant imaging findings without visible distress also need timely communication through the established pathway, with the finding and recipient documented. Do not delay escalation to finish measurements or construct a definitive interpretation. A technically complete image set has little value if it postpones care for a changing patient.

Worked example: Midway through a carotid examination, the patient suddenly has difficulty speaking. You stop scanning, note the time the change was first observed, remain with the patient, and call the designated clinical response. You report the sudden speech change and the patient's current responsiveness. After the handoff, document the interrupted examination and the communication rather than filling in missing velocities.

Watch the distinction: Finishing the carotid velocity set before calling for help reverses the priority. A sonographer should communicate the observed acute change promptly, without assigning a stroke diagnosis.

8. Document limits and communication

An examination record should let another clinician distinguish what was seen from what was inferred. Identify examined segments, measurements, Doppler observations, and relevant comparison studies. For each limitation, state the affected segment and cause, such as bowel gas, depth, bandaging, pain, or inability to position; a broad statement that the study was difficult gives little guidance. Indirect evidence can narrow possibilities but does not prove direct patency. For example, an intrarenal waveform shows perfusion within the kidney, while a proximal renal artery hidden by gas remains unassessed for focal narrowing. Record patient tolerance and any adapted technique that affects confidence. When a significant finding is communicated, document what was conveyed, to whom, and when, without replacing the interpreting clinician's final assessment.

Worked example: Bowel gas hides the proximal right renal artery despite repositioning. You obtain mid and distal renal views plus intrarenal waveforms, each labeled by site. The technical note states that the proximal segment was not visualized because of gas and lists the measurements actually obtained. If you communicate a concerning waveform pattern, record the recipient and time; do not label the unseen origin patent.

Watch the distinction: Flow downstream proves that blood reaches the organ, not that every upstream segment is normal. Calling an unseen renal origin patent turns indirect evidence into an unsupported direct finding.

9. Choose frequency for the target

Frequency controls a tradeoff that begins with wavelength: at the same sound speed, higher frequency means shorter wavelength. Shorter wavelengths can separate smaller structures, making a superficial vessel wall or narrow channel easier to resolve. Higher-frequency sound also attenuates more rapidly in tissue, leaving less returning signal from deep vessels. Start with the highest frequency that adequately reaches the target, then lower frequency when penetration is insufficient. Depth, body habitus, and the intervening tissue all influence that choice. A low-frequency probe can reveal a deep vessel but may lose fine wall detail; a high-frequency probe can show a shallow artery sharply while failing to display deep flow. The same tradeoff appears in broader sonography study topics, but vascular work adds the need for usable Doppler signals.

Worked example: A high-frequency linear probe clearly separates the near and far walls of a radial artery at shallow depth. At the iliac artery, the same probe produces weak echoes and incomplete color fill. You change to a lower-frequency probe, adjust depth and focus, and obtain a continuous lumen and spectral signal. You accept less fine detail because penetration now answers the deep-vessel question.

Watch the distinction: The probe with the sharpest superficial image is not automatically best for a deep artery. Increasing gain cannot restore echoes that were too attenuated to return.

10. Read echoes through tissue

An echo forms when sound meets a change in acoustic impedance, the product of tissue density and sound speed. A large mismatch returns more energy and transmits less beyond the interface. As sound travels, absorption and scattering reduce its strength; greater depth therefore usually requires compensation. Calcified plaque can reflect and attenuate so strongly that a dark acoustic shadow hides the lumen behind it. Darkness in that shadow is missing information, not evidence that the lumen is empty or occluded. Seek a different probe angle or window to move the shadow, then use color and spectral Doppler where sound can reach the flow channel. Compare proximal and distal waveforms for functional evidence. A true conclusion about obstruction should rest on visible anatomy and flow findings together, with the hidden segment documented.

Worked example: A bright calcified plaque produces a dark band across the posterior carotid lumen. From the first window, color appears absent behind the plaque. You rotate or move the probe and obtain a partial alternative view showing residual color flow, then sample the accessible channel spectrally. The lumen cannot be called occluded from the shadowed image; the residual flow and visualization limit are recorded.

Watch the distinction: An acoustic shadow is a failure to see through a strong reflector. Interpreting its black interior as thrombus or absent flow confuses an imaging limitation with a vascular finding.

11. Separate anatomy from artifacts

Several artifacts change apparent vessel anatomy without changing the vessel itself. Reverberation occurs when sound bounces between strong reflectors, creating repeated echoes at deeper displayed positions. Refraction bends the beam at an angled boundary, so returning echoes may be placed along an assumed straight path and appear as duplicated or displaced structures. Scattering from small or irregular interfaces sends energy in many directions, contributing texture and reduced clarity. Test a suspicious finding by changing the insonation angle, position, or acoustic window and checking whether the apparent structure stays attached to the anatomy. Confirm a suspected second lumen in two planes and examine whether each channel has coherent flow. A feature that appears only along one beam path deserves an artifact explanation before a vascular diagnosis.

Worked example: A longitudinal image seems to show two parallel arterial lumens. In transverse view, only one continuous vessel is found. When you heel and rotate the probe, the extra channel shifts and disappears while the true vessel remains fixed and has consistent Doppler flow. That beam-dependent behavior favors refraction artifact. You retain images from both planes and do not report a second artery.

Watch the distinction: One convincing longitudinal frame does not establish a duplicated vessel or dissection channel. A real structure should remain anatomically consistent across views and have corresponding flow when appropriate.

12. Optimize grayscale detail

Grayscale settings should make the vessel occupy a useful portion of the display while preserving its wall and lumen. Set depth just beyond the relevant anatomy; excess depth wastes pixels and can reduce frame rate. Place the focal zone near the vessel because lateral beam width is narrowest around the focus. Adjust overall gain until fluid appears dark without erasing low-level intraluminal echoes, then use time-gain compensation to balance near and far fields. Dynamic range controls how many echo strengths map into visible gray levels: a broader range can show subtle texture, while a narrower range increases contrast but may hide nuance. Optimize these settings before measuring wall or lumen boundaries. Excess gain can make a clear lumen look filled, and insufficient gain can make real wall or thrombus echoes disappear.

Worked example: A superficial artery occupies a thin strip at the top of a deep image, and the lumen looks gray. You reduce depth until the artery fills more of the screen, position the focus at its far wall, and lower overall gain. A small near-field time-gain adjustment evens the brightness. The near and far walls become distinct, while the lumen remains dark enough to assess visible intraluminal material.

Watch the distinction: Increasing brightness does not necessarily reveal more anatomy. Excess gain can create apparent material inside a clear vessel, while too narrow a dynamic range can erase subtle wall detail.

13. Tune color Doppler

Color Doppler estimates flow from frequency shifts and displays the result within a selected box. Start with a box just large enough for the vessel and surrounding context; a smaller box usually improves frame rate. Steer the beam to produce a usable angle with flow. Set scale so ordinary flow displays without needless aliasing, but retain sensitivity to slower flow. A wall filter that is too high removes low-frequency signals from slow blood as well as motion. Raise color gain until background speckle begins, then back off until noise and color spill outside the wall disappear. A focal mosaic may reflect disturbed high-velocity flow, but gain bloom and aliasing can look similar. Compare the color pattern with grayscale narrowing and targeted spectral samples before assigning it to disease.

Worked example: Color fills beyond the carotid wall at a high gain setting, obscuring the true channel. You lower gain until the spill disappears, narrow the box, and adjust scale so the normal segment remains readable. A small mixed-color area persists at visible plaque. You sample that site and an adjacent segment spectrally; only the persistent focal pattern, not the earlier spill, informs lesion assessment.

Watch the distinction: Color outside the vessel wall at excessive gain is not proof of a leak or wider lumen. The color display must be optimized before its boundaries are interpreted anatomically.

14. Use power Doppler selectively

Power Doppler displays the strength of moving-blood signals rather than encoding the usual directional velocity information of color Doppler. This can help reveal a small or slow-flow channel when conventional color fill is weak. Optimize depth, gain, motion control, and box size because tissue motion and excessive gain can also produce power signal. A filled channel establishes detectable motion at that location, but it does not tell you whether flow is toward or away from the probe or supply a velocity for stenosis grading. Once the channel is found, place a spectral sample within it and obtain a waveform if technically possible. Cross-check with grayscale anatomy and adjacent segments. Power Doppler is particularly useful for the question of whether residual flow exists, provided the display is not mistaken for a complete hemodynamic assessment.

Worked example: A small distal artery shows intermittent conventional color despite a suitable window and low-flow settings. Power Doppler reveals a continuous narrow channel beside the bone shadow. You use that channel to guide a spectral sample, obtaining forward pulsatile flow with a measurable waveform. The record distinguishes flow detection by power Doppler from direction and waveform information supplied by spectral Doppler.

Watch the distinction: A bright power Doppler channel does not quantify velocity or establish flow direction. Calling a lesion severe from power brightness alone assigns meaning that this mode does not encode.

15. Acquire defensible spectral velocities

A spectral velocity is useful only when its sample represents the intended flow stream and its angle correction follows actual flow direction. Place the gate within the lumen, usually in the region of interest rather than across the wall or adjacent vessel. In a bend or stenotic jet, the flow vector may differ from the visible vessel wall; use color and multiple views to align the cursor with the jet. Doppler shift depends on the cosine of the insonation angle, so angle error can produce a substantial velocity error, especially at steep angles. Set scale and baseline to display the full waveform without wrapping, and adjust gain enough to reveal the envelope without filling the spectral window with noise. Ultrasound physics review reinforces the angle relationship; vascular interpretation requires matching that physics to lesion location.

Worked example: A curved arterial segment gives an unexpectedly high peak reading while the angle cursor follows the outer wall. Color shows that the jet crosses the lumen at a different direction. You reposition the probe, align correction with the visible jet, center the gate in that stream, and reacquire the waveform with an adequate scale. The revised value is compared with a nearby reference sample acquired under comparable conditions.

Watch the distinction: Angle correction is not valid merely because the cursor lies along a vessel wall. At a bend, wall direction and blood direction can differ enough to distort velocity comparisons.

16. Recognize resolution and equipment limits

Spatial resolution describes the ability to separate nearby structures; temporal resolution describes how well the system follows change over time. Higher line density or a broad color region may improve displayed detail or coverage while reducing frame rate. A narrow color box and sensible depth can improve depiction of a pulsating vessel because fewer lines must be processed per frame. Image defects require a different reasoning path. A dropout that tracks a patient's calcification or gas may be acoustic, while a repeatable vertical defect at a fixed screen or probe position may suggest an equipment problem. Test a suspected defect by changing window, preset, and probe where available, then document its persistence for quality-control evaluation. Do not let a recurring machine artifact masquerade as a reproducible vessel abnormality.

Worked example: A wide color box blurs changes in a pulsating artery. You narrow it around the vessel and the frame rate improves while adequate context remains. Separately, a vertical dropout persists at the same display location in different patients and with another probe. You save representative images, note the conditions, and request equipment evaluation rather than labeling each affected vessel occluded.

Watch the distinction: Better frame rate does not automatically mean better spatial detail. Likewise, a defect repeated across unrelated patients is a reason to check equipment, not repeated evidence of disease.

17. Link pressure, resistance, and flow

Flow requires a pressure difference, and vascular resistance opposes it. In a simplified steady-flow model, flow equals pressure gradient divided by resistance: Q = ΔP/R. The model helps predict direction of change, though living arteries are pulsatile and their resistance varies with vessel geometry and tissue demand. Narrowing increases resistance sharply because a smaller radius leaves much less space for flow; severe lesions may also waste energy through disturbed flow. Distal arterioles can dilate, lowering downstream resistance and increasing diastolic flow when perfusion demand rises. Pressure, flow, and velocity are related but distinct: velocity through a narrow jet can rise even while total volume flow falls. Use the equation for defined hypothetical inputs and use duplex waveforms to assess how a real vascular system responds.

Worked example: In a hypothetical steady-flow circuit, the pressure gradient is 40 mm Hg and resistance is 10 mm Hg per flow unit. Flow is 40/10 = 4 flow units. If resistance doubles to 20 mm Hg per flow unit while the gradient remains 40 mm Hg, flow becomes 40/20 = 2 flow units. The calculation predicts reduced volume flow under those stated assumptions.

Watch the distinction: A faster focal jet does not mean the entire limb receives more blood. A stenosis can accelerate blood locally while raising resistance and reducing total downstream flow.

18. Follow collateral pathways

When a main artery is blocked, pressure upstream can drive blood through connecting branches into a lower-pressure distal segment. This collateral route may preserve detectable distal flow, but it often adds resistance and changes the arrival pattern. The reconstituted waveform may have lower amplitude and a slower systolic rise than a waveform supplied through a direct open channel. Flow direction within a collateral can differ from the expected direction in the neighboring native segment, so trace the connection rather than labeling vessels from one color frame. Identify the point where the main lumen loses flow, follow any collateral, and document the level where distal native flow reappears. Distal patency answers a different question from patency across the occluded segment; both should be reported separately.

Worked example: The superficial femoral artery loses color and spectral flow over a defined segment. A branching vessel carries flow around that region and joins the distal popliteal artery, where a low-amplitude, delayed waveform is present. You document the absent signal in the main segment, the visible collateral route, and the reconstitution level. The distal signal indicates maintained perfusion, not continuous patency through the occlusion.

Watch the distinction: Detecting flow beyond an occlusion does not disprove the occlusion. Collateral vessels can supply that distal segment and produce a waveform unlike direct, unobstructed inflow.

19. Interpret arterial resistance patterns

Waveform shape reflects the resistance of the vascular bed as well as upstream supply. A resting limb artery supplying relatively inactive muscle often has a sharp systolic forward peak, brief early diastolic reversal, and sometimes a small late forward component. In a low-resistance bed, forward flow persists through more of diastole because downstream arterioles are open. Exercise increases muscle demand and promotes distal vasodilation, so a limb waveform may temporarily gain forward diastolic flow without a new arterial lesion. Warmth, inflammation, or an arteriovenous connection can also lower distal resistance. Interpret a waveform in its anatomical and physiologic setting, then compare adjacent levels and the opposite side when relevant. A delayed systolic rise points more toward impaired inflow than isolated loss of diastolic reversal does.

Worked example: At rest, a leg artery has a brisk systolic peak and brief early diastolic reversal. After walking, the patient has no new focal jet, but the same artery shows sustained forward diastolic flow and retains a brisk systolic rise. Increased muscle demand lowers distal resistance and explains the change. You record the exercise state so the postexercise trace is not mistaken for a resting abnormality.

Watch the distinction: Loss of early diastolic reversal alone does not identify proximal stenosis. Distal vasodilation can create forward diastolic flow, so examine systolic rise, lesion-site velocities, and testing conditions.

20. Trace the effects of stenosis

A narrowing reduces cross-sectional area, so blood passing through the residual lumen accelerates. At and beyond the jet, different flow speeds and directions can broaden the spectral display and create poststenotic disturbance. Farther downstream, a lesion that substantially limits pressure transmission may produce a rounded, delayed systolic upstroke and reduced pulsatility. Follow the sequence in anatomical order: normal reference segment, visible narrowing, focal velocity rise, immediate disturbance, then distal waveform. Spectral broadening by itself is weak evidence because a large sample gate, poor angle, or excessive gain can widen the display. Likewise, a high velocity at a bend may reflect geometry rather than plaque. The combined pattern helps localize and characterize a lesion while leaving final diagnostic interpretation to the responsible clinician.

Worked example: A limb artery measures 60 cm/s before a visible narrowing and 210 cm/s in its jet, a local ratio of 210/60 = 3.5. Flow immediately beyond the narrowing is disturbed, and the more distal waveform has a rounded systolic rise. Under a hypothetical case rule requiring a ratio above 3.0 plus supporting findings, the sequence supports a significant focal lesion at that site.

Watch the distinction: A broad spectrum alone is not a stenosis measurement. Gate size, gain, and beam alignment can broaden it, so seek a focal jet and downstream effects before locating disease.

21. Calculate ankle-brachial indices

The ankle-brachial index compares ankle systolic pressure with arm systolic pressure, so both measurements must be taken under comparable resting conditions. Use the higher valid brachial pressure as the denominator and, for each leg, the higher of its dorsalis pedis and posterior tibial pressures as the numerator. Divide pressures in the same units; the resulting index has no units. A lower ratio can indicate a pressure loss along the arterial path to that ankle, but it does not identify the lesion's location. Check cuff fit, limb position, and whether the artery actually became silent during inflation before trusting the arithmetic. If ankle arteries resist compression, the apparent pressure may be falsely high. Interpret a calculated value using the criteria supplied with the case and compare it with waveforms and symptoms. This is a useful calculation for an ARRT vascular sonography candidate to work through step by step.

Worked example: At rest, brachial systolic pressures are 132 and 128 mm Hg. The right dorsalis pedis and posterior tibial pressures are 90 and 96 mm Hg. Select 132 mm Hg for the denominator and 96 mm Hg for the right ankle numerator: 96/132 = 0.727, or 0.73. Under this hypothetical case's rule that an index below 0.90 is abnormal, the right result supports reduced arterial perfusion.

Watch the distinction: Using the lower ankle pressure may exaggerate disease when calculating the standard limb index. Record both ankle pressures, then select the higher valid one for that leg.

22. Localize with segmental testing

Segmental testing seeks the first level where several independent signals worsen together. Systolic cuff pressures estimate pressure delivered to each level. Pulse volume recordings show how the arterial pulse expands the limb; a healthy contour has a brisk rise and a distinct peak, while significant upstream disease can flatten or delay it. Continuous-wave Doppler adds flow direction and waveform shape. Compare levels within one limb and with the opposite side, allowing for cuff placement, cuff width, and measurement error. A drop in pressure plus a newly rounded pulse contour between adjacent sites points toward disease in that intervening arterial region. A waveform that is already damped at the highest sampled site directs attention farther upstream. Collaterals and multilevel disease can blur localization, so duplex imaging helps establish the anatomy.

Worked example: Suppose the thigh pressure is 130 mm Hg with a brisk pulse volume contour. At the calf it is 86 mm Hg with a flatter contour, and the ankle tracing has a slow systolic rise. The first paired deterioration occurs between thigh and calf. Investigate the arterial path across that interval, including the distal femoral and popliteal region, while checking for additional distal disease.

Watch the distinction: An abnormal ankle tracing does not automatically place a lesion at the ankle. Follow the pressure and contour changes upward to find where deterioration first appears.

23. Handle noncompressible vessels

An ankle pressure is valid only if cuff inflation stops flow through the measured artery and deflation reveals its return. Stiff, calcified arteries may remain open under the cuff, producing an artificially high pressure and ankle-brachial index. An implausible value, persistent Doppler signal during inflation, and discordantly abnormal pulse waveforms should prompt scrutiny. Toe arteries are often more compressible, so a toe systolic pressure and toe-brachial index can supply additional evidence. Divide the toe pressure by a valid brachial systolic pressure, using the same pressure units. Warmth, cuff size, edema, and positioning also affect toe measurements; record the conditions and inspect the toe waveform. Neither a toe ratio nor a waveform alone maps the obstructed segment. Duplex and segmental findings can then help localize disease.

Worked example: An ankle signal never disappears during cuff inflation, and the displayed ankle index is 1.62 despite a damped foot waveform. Do not use 1.62 as evidence of normal perfusion. With a hypothetical toe pressure of 72 mm Hg and higher brachial pressure of 144 mm Hg, the toe-brachial index is 72/144 = 0.50. Record the toe waveform and interpret this ratio under the case's supplied criteria.

Watch the distinction: A very high ankle index is not proof of unusually good flow. Failure to occlude a stiff artery can make the numerator, and therefore the index, unreliable.

24. Compare rest and exercise results

Resting pressure can look preserved when collateral pathways meet ordinary demand. Exercise increases muscle demand and flow, making a flow-limiting lesion more likely to produce a measurable distal pressure loss. Record symptoms, workload, and the interval between stopping exercise and each pressure measurement; an early decline may recover quickly. Compare the same artery and cuff site before and after exercise, and ensure that brachial pressure, body position, and measurement technique are considered. A falling ankle pressure with reproduced limb symptoms supports impaired flow reserve, while a stable resting value alone cannot exclude it. Duplex can locate a plausible lesion, and serial recovery measurements show how long the pressure deficit persists. The sonographer documents these observations for clinical interpretation rather than assigning a diagnosis from one number.

Worked example: A patient develops familiar calf pain during a hypothetical exercise test. Ankle systolic pressure is 118 mm Hg at rest and 78 mm Hg immediately afterward: 118 - 78 = a 40 mm Hg fall. It rises on repeat measurement several minutes later. Record the exact measurement times and symptoms; the transient exercise-related pressure loss supports limited flow reserve when the rest and duplex findings are considered.

Watch the distinction: Comparing a late postexercise pressure with the resting value can miss a brief decline. Measure promptly, record timing, and follow recovery rather than relying on one delayed reading.

25. Map neck vessel anatomy

Begin at the common carotid artery and follow it to the bulb, then trace each daughter vessel in longitudinal and transverse planes. The internal carotid artery usually has no visible neck branches and supplies a low-resistance cerebral bed. The external carotid artery gives off neck and face branches and commonly shows a more resistant resting waveform. Position varies, especially where vessels twist or cross, so branch pattern and continuity matter more than a single screen location. Find the vertebral artery between cervical transverse processes and establish its direction relative to the subclavian circulation. Trace the subclavian artery proximally when its origin or a suspected inflow lesion is relevant. Variants and limited windows can alter the usual picture; label only what you can follow anatomically and support with Doppler evidence.

Worked example: Near the bifurcation, one vessel runs superficially and gives off two visible neck branches. Its waveform has relatively little forward diastolic flow. The deeper vessel is branch-free over the sampled length and shows sustained forward diastolic flow. The combined course, branches, and waveforms favor external carotid identity for the first vessel and internal carotid identity for the second.

Watch the distinction: Calling the vessel nearest the transducer the external carotid can fail when anatomy rotates. Trace branches and compare waveforms before assigning either carotid label.

26. Identify internal versus external carotid

Vessels immediately beyond the carotid bifurcation can exchange apparent positions as they curve through the neck. Identify them by following continuity from the bulb, looking for branches, and comparing their downstream resistance patterns. Cerebral circulation normally maintains forward flow through much of diastole, which helps explain the internal carotid waveform. The external carotid supplies more muscular and superficial beds, giving it a comparatively sharper systolic peak and less diastolic flow at rest. These are tendencies, not absolute identifiers: disease, collateral flow, or altered systemic hemodynamics can change either waveform. A branch seen directly is strong anatomical evidence, while a waveform provides a second check. If image quality is poor, document uncertainty and obtain another plane instead of assigning a vessel from one Doppler trace.

Worked example: Two arteries cross shortly after the bifurcation, making their screen positions misleading. Follow both through transverse and longitudinal views. One remains branch-free and carries sustained forward diastolic flow; the other gives off a visible branch and has relatively less diastolic flow. Label the branch-free vessel internal carotid and the branching vessel external carotid, noting the crossover in the images.

Watch the distinction: Sustained diastolic flow is helpful but cannot identify the internal carotid by itself. Altered resistance can change waveforms, so confirm the vessel's course and branch pattern.

27. Sample the carotid examination

A reviewable carotid examination links anatomy, lumen appearance, and measured flow at each important site. Survey the common carotid, bulb, and proximal through distal internal and external carotid segments with grayscale and color imaging. Grayscale shows plaque texture, wall changes, and visible residual lumen; color locates the flow channel and helps target spectral sampling. Place the sample volume within the stream, align angle correction with its local direction, and save representative waveforms from appropriate segments. At a suspected lesion, record the jet and a nearby reference measurement, then show the downstream pattern. Document where the measurements were made, especially if tortuosity or shadowing limits confidence. The Society for Vascular Ultrasound offers further professional vascular ultrasound education; a complete image set still needs to support the specific findings reported.

Worked example: Plaque lies just beyond the left carotid bulb. Save longitudinal and transverse grayscale views, show the narrowest color channel, and sample its peak flow with the cursor aligned to that channel. Obtain a nearby common carotid reference velocity and a distal internal carotid waveform. Together, these images let the reader assess plaque, focal acceleration, and downstream effect at identified sites.

Watch the distinction: A single high velocity without its sampling location or vessel image is difficult to interpret. Preserve the lesion view, Doppler alignment, reference site, and distal waveform.

28. Assess plaque and narrowing

Plaque can narrow a carotid lumen and accelerate blood through the remaining channel, but velocity depends on more than diameter. Cardiac output, tandem lesions, tortuosity, and a very small residual channel may change the measured speed. Describe plaque and visible lumen on grayscale, use color to seek the narrowest flow path, and sample peak systolic velocity with defensible angle correction. Divide internal carotid peak systolic velocity by a valid common carotid reference velocity when the case asks for a ratio; both velocities must use the same units. Compare velocity and ratio with the exact categories supplied in the question, then check distal flow and technical limits for agreement. The sonographer's job is to acquire and document evidence that supports physician interpretation, including discordant measurements.

Worked example: A hypothetical case gives an internal carotid peak velocity of 210 cm/s and a common carotid reference of 70 cm/s. The ratio is 210/70 = 3.0. Suppose the case defines category B as velocity at least 200 cm/s and ratio at least 2.5, with visible plaque. All three conditions are met, so classify this measured site as category B under that supplied rule.

Watch the distinction: A ratio can look impressive when the common carotid reference velocity is unusually low. Check the reference site, plaque, jet, and distal waveform before relying on the quotient.

29. Separate occlusion from near-occlusion

Absent color in a carotid segment means flow was not displayed under the chosen settings; it does not, by itself, establish an occlusion. A threadlike residual channel may carry slow flow that a high color scale, wall filter, poor angle, or insufficient gain misses. Revisit the suspected lumen in multiple planes, lower the scale and filter appropriately, raise gain short of background noise, and try power Doppler when useful. Place spectral Doppler in any suspected channel to confirm actual flow. Trace the distal internal carotid and assess its caliber, since distal collapse can accompany near-occlusion. Calcific shadowing may prevent direct visualization, and collateral vessels can be mistaken for the native lumen. Record what is seen and the technical limits so the interpreting physician can distinguish residual flow from complete occlusion.

Worked example: Initial color imaging shows no flow at the internal carotid origin. After reducing scale and optimizing gain, a thin channel appears through the plaque. A spectral sample in that channel confirms arterial flow, and the distal vessel is small. Document the residual channel and distal caliber. These observations argue against calling the origin completely occluded on the initial color image.

Watch the distinction: Turning up color gain until random speckle fills a suspected lumen can create false reassurance. Confirm any apparent channel in multiple views and with a reproducible spectral signal.

30. Recognize steal physiology

A narrowing proximal to the vertebral artery origin can lower pressure in the ipsilateral subclavian artery. Blood may then be drawn through the vertebral pathway toward the arm. Early in this process, the vertebral waveform can develop a systolic notch or brief reverse component while net flow remains forward. Greater pressure diversion may produce alternating or fully reversed flow. Establish the transducer's directional convention before labeling flow toward or away from the head, and sample the proximal subclavian artery for a focal jet or downstream damping. Compare both sides and note arm symptoms or pressure differences when available. Other causes of unusual vertebral waveforms exist, so the pattern should be tied to the subclavian findings and vessel anatomy. Report the observed directions and waveform phases for interpretation.

Worked example: The left vertebral spectrum has forward flow in part of each cycle and a reverse systolic component. The left proximal subclavian artery has a focal high-velocity jet with disturbed flow beyond it; the right vertebral remains forward. After confirming probe orientation, document bidirectional left vertebral flow and the subclavian lesion. The combination supports partial steal physiology caused by a proximal pressure drop.

Watch the distinction: A reverse-looking color alone does not prove steal. Confirm orientation and spectral direction, then examine the ipsilateral subclavian inflow and compare the opposite vertebral artery.

31. Examine dissection and repaired carotids

A dissection can separate blood within the arterial wall and create a flap or two channels with different flow. Seek a persistent flap in more than one plane, assess whether each apparent channel has flow, and trace where the abnormality begins and ends. Artifacts can imitate a flap, so reproducibility matters. After endarterectomy, the bulb may have a changed contour and surgical wall appearance. A stent adds a visible framework and can alter local flow and measured velocity, making an unqualified native-vessel category unreliable. Map the repair, sample inflow, repaired segment, and outflow, and compare the same sites with prior examinations. Document focal narrowing, jet location, and distal changes. The interpreting physician can then judge progression using the appropriate repaired-vessel context.

Worked example: A patient has a carotid stent. Color shows a focal narrow channel inside its middle third, with a local velocity rise and disturbed flow immediately beyond it. The prior study showed a wider channel at that site. Record the stent segment, current and prior measurements, and distal waveform; the combined change is more informative than applying a native-carotid category to one velocity.

Watch the distinction: A bright line beside the lumen is not automatically a dissection flap. Check whether it persists in another plane and separates reproducible flow channels.

32. Resolve carotid velocity conflicts

A carotid velocity should fit its anatomy and neighboring waveforms. At a sharp bend, flow direction can diverge from the vessel wall; placing the angle cursor along the wall may inflate the calculated velocity. Reimage the bend, align the cursor with the local color stream, and sample straight segments on either side. Calcific plaque may hide a true jet, making distal disturbance more revealing than the obscured lumen. Tandem lesions can reduce flow through one another and distort simple velocity expectations. High or low systemic flow can shift velocities across both sides. Compare plaque, color channel, ratios, distal waveforms, and prior studies before describing the conflict. State any shadowed or inaccessible segment plainly; uncertainty in a measurement is useful information for physician interpretation.

Worked example: A high internal carotid velocity occurs at a tight curve, but no plaque or postbend disturbance is visible. The angle cursor originally follows the wall rather than the color stream. After realignment, the velocity falls and adjacent straight segments remain unremarkable. Document the corrected sample and curve. The original isolated value does not support a focal plaque-related stenosis.

Watch the distinction: Treating the largest displayed number as the best measurement can overstate disease. Check angle alignment, visible plaque, nearby samples, and downstream flow before choosing a representative velocity.

33. Trace lower-limb arterial pathways

For lower-limb duplex, follow arterial continuity from inflow to runoff rather than treating each visible Doppler signal as proof of a continuous native channel. The common femoral divides into profunda and superficial femoral arteries; the latter continues through the adductor canal to the popliteal artery, which supplies tibial pathways. The profunda and genicular networks can bypass an obstructed segment and reconstitute flow farther down. At an apparent interruption, search for plaque or thrombus, confirm absent flow with suitable settings, then trace collateral entry and the level where native flow returns. Compare waveforms before and after reconstitution: distal flow may be slower and have a delayed systolic rise despite remaining detectable. Document vessel identity, occlusion length when measurable, collateral route, and distal runoff for interpretation.

Worked example: The distal superficial femoral artery contains no detectable flow despite optimized color and spectral settings. A collateral from the profunda pathway approaches the popliteal region, where arterial flow reappears with a delayed systolic upstroke. Record the native artery's last patent point, its nonflowing segment, and popliteal reconstitution. Distal flow does not make the intervening native artery patent.

Watch the distinction: Finding a popliteal signal does not rule out a femoral occlusion. Collaterals can restore distal flow, so trace the vessel continuously and identify the reconstitution point.

34. Trace upper-limb arterial pathways

Upper-limb arterial assessment begins with the subclavian artery, then follows axillary and brachial segments to the radial and ulnar arteries. A proximal inflow lesion can change every sampled artery below it, while a focal forearm lesion may affect one distal branch more than the other. Compare waveform shape, systolic rise, and relative velocities at successive levels, using grayscale and color to inspect a suspected site. The brachial bifurcation can vary in level, so confirm anatomy rather than assuming a fixed branching point. Hand perfusion can also depend on communication between radial and ulnar pathways; distal signals should be interpreted alongside symptoms and the larger arterial survey. A damped pattern appearing first at the axillary or brachial level directs scanning toward proximal inflow, including accessible subclavian segments.

Worked example: A patient has a cool hand. Brachial, radial, and ulnar spectra all show slow systolic upstrokes, with no focal jet in the forearm. Their shared abnormal pattern points upstream of the brachial sampling site. Extend the examination through the axillary and accessible subclavian arteries, recording any focal acceleration and how the waveform changes beyond it.

Watch the distinction: Abnormal radial and ulnar waveforms do not necessarily mean two separate forearm lesions. Similar changes in both branches may reflect one shared proximal inflow problem.

35. Plan a limb duplex survey

A limb duplex survey should answer where blood enters, where it is disturbed or interrupted, and how much flow pattern remains distally. Begin with the relevant proximal inflow and trace named arteries through the symptomatic territory to runoff. Grayscale reveals wall disease, lumen changes, and calcification; color helps locate a narrow jet or small residual channel; spectral Doppler compares velocity and waveform shape before, within, and after a suspected lesion. Reduce depth and color-box size for smaller distal arteries, and set scale low enough to show slow flow without confusing noise with a lumen. Sample a focal abnormality and an adjacent reference segment at comparable angles. If shadowing or wounds block a segment, use another window and state the limit. Preserve a representative distal waveform to show the lesion's functional effect.

Worked example: A patient with a calf ulcer has a patent femoral artery but weak foot signals. Survey the popliteal artery and each accessible tibial runoff vessel rather than stopping at femoral patency. Adjust depth, color scale, and sample size for the small arteries. Document any focal jet, occluded segment, collateral reconstitution, and distal waveform so the poor foot signal has an anatomical context.

Watch the distinction: A normal proximal image cannot explain distal perfusion by itself. Continue into runoff and document the distal waveforms, especially when symptoms or physiologic findings suggest disease.

36. Characterize focal limb stenosis

A focal narrowing reduces the available flow area, often producing a local high-velocity jet. Compare peak systolic velocity at the jet with velocity in a nearby, reasonably normal prelesion segment: jet velocity divided by reference velocity gives a unitless local ratio. Keep Doppler angles and sampling methods consistent, since a poor reference can distort the quotient. Grayscale plaque or lumen narrowing, color aliasing at the jet, poststenotic spectral disturbance, and a changed distal waveform provide independent support. A ratio describes the sampled lesion under the interpretation rule supplied with the case; it is not a complete statement about the entire limb. Diffuse disease, collateral inflow, or tandem lesions may complicate the comparison. The same measurement logic is useful in RVT study examples.

Worked example: A hypothetical superficial femoral lesion has a prelesion peak velocity of 55 cm/s and a jet velocity of 220 cm/s. The local ratio is 220/55 = 4.0. This case defines a ratio above 3.5 as severe. Visible plaque, focal color aliasing, and postjet disturbance agree, so classify the measured lesion as severe under the supplied rule and document distal flow.

Watch the distinction: Dividing by a distant or already diseased reference can misclassify a focal lesion. Choose a nearby valid segment and explain when diffuse disease prevents a trustworthy ratio.

37. Distinguish inflow, diffuse, and outflow disease

The distribution of abnormal waveforms helps decide where to search next. A slow systolic rise throughout a limb suggests reduced proximal inflow, particularly when the pattern begins at the first sampled artery. A focal jet with immediate postjet disturbance favors a local stenosis. Widespread plaque and changing velocities across many segments suggest diffuse disease, where one clean reference site may be hard to find. Distal outflow obstruction can increase resistance upstream or alter diastolic flow, so waveform shape must be read with the visible anatomy and symptoms. Compare proximal, mid, and distal sites, plus the opposite limb when useful. If the common femoral waveform is already damped and no femoral jet appears, extend the survey toward iliac inflow. Document the first abnormal level and any technically inaccessible region.

Worked example: Common femoral, popliteal, and tibial arteries all have delayed systolic upstrokes. No focal velocity jump appears within the visible femoral or popliteal course. Because the common femoral signal is abnormal before those distal segments, investigate iliac inflow and compare the other side. Multiple rounded limb waveforms alone do not establish separate stenoses at every sampled site.

Watch the distinction: Assigning each damped distal waveform to a separate distal lesion ignores shared inflow. Find where the abnormal pattern first appears, then search proximal to that level.

38. Recognize aneurysm and pseudoaneurysm

An aneurysmal artery is enlarged along its vessel course, with the lumen and wall assessed in perpendicular planes. Mural thrombus may occupy part of the dilated segment, leaving a smaller flowing channel. A pseudoaneurysm instead forms when blood escapes through a defect and remains connected to the artery by a neck, creating a sac outside the expected arterial wall. Grayscale shows sac and neck geometry; color may show swirling within the sac; spectral Doppler at the neck can show flow entering and leaving during different parts of the cardiac cycle. Measure relevant dimensions consistently and distinguish flowing lumen from surrounding thrombus or tissue. A nearby hematoma may lack internal flow, so color alone should be confirmed by careful grayscale and spectral views. Document the communication and surrounding structures for physician interpretation.

Worked example: After femoral arterial puncture, a rounded sac sits beside the artery rather than along its expanded wall. Color shows swirling flow, and spectral sampling in a narrow connecting neck shows flow into and out of the sac. Record sac dimensions, neck location, and the parent artery. This anatomy supports pseudoaneurysm, whereas uniform dilation of the arterial segment would favor aneurysm.

Watch the distinction: A colorful mass near an artery is not automatically a pseudoaneurysm. Demonstrate a reproducible neck connecting the sac to the parent artery and sample flow there.

39. Assess arterial injury and fistula

An arteriovenous fistula allows arterial blood to enter a vein without passing through the usual high-resistance small-vessel network. The feeding artery may therefore carry increased, low-resistance flow, while the draining vein becomes unusually pulsatile and may show turbulent, arterialized signals. Trace both vessels toward the point of communication with grayscale, color, and spectral Doppler; high color gain alone can make them appear connected when they are separate. After injury or a procedure, also inspect for pseudoaneurysm, thrombosis, and altered distal arterial flow. Symptoms such as swelling, bruit, pain, or hand or foot perfusion change give context, but ultrasound should document the actual anatomy and hemodynamics. Compare distal waveforms and any available physiologic measurements so a possible diversion of flow is described, not assumed.

Worked example: Following a procedure, the brachial artery has increased forward diastolic flow, and an adjacent vein has strong pulsations. A short color channel connects them, with turbulent flow at the junction. Document the connection, feeding artery, draining vein, and distal radial and ulnar waveforms. The paired arterial and venous changes support an arteriovenous communication; distal measurements show whether hand flow is also altered.

Watch the distinction: A pulsatile vein alone does not locate a fistula. Trace it to a reproducible arterial connection and examine the feeding artery and distal perfusion pattern.

40. Map lower-limb veins

Name a calf vein by its course and connections, because thrombus extent depends on the actual vessel involved. Deep axial veins include the paired posterior tibial and peroneal veins, which accompany arteries and lead toward the popliteal vein. Gastrocnemius and soleal muscular veins drain the calf muscles and can connect with the deeper system. The great and small saphenous veins are superficial; their junctions with deep veins matter when describing extension. Follow a suspected abnormality in transverse and longitudinal planes, use compression where accessible, and identify the nearest junction and the most proximal observed extent. A superficial-looking vessel can be a collateral, and anatomical variants occur. Record the exact named segment and whether adjacent deep veins compress, leaving clinical risk assessment and treatment decisions to the interpreting clinician.

Worked example: In a painful calf, intraluminal material occupies a gastrocnemius muscular vein that does not fully compress. The adjacent paired posterior tibial veins coapt with compression, and the popliteal vein is patent on the obtained views. Document the involved muscular vein, its observed extent, and the compressible deep axial veins. Calling all of these structures simply “calf veins” would obscure where the finding lies.

Watch the distinction: A muscular calf vein and an adjacent paired deep vein are not interchangeable labels. Trace their courses and junctions so the reported location and extent are clear.

41. Map upper-limb veins

Begin with the paired brachial veins beside the brachial artery, then follow their drainage into the axillary and subclavian veins. The internal jugular vein joins the subclavian vein to form the brachiocephalic vein. The basilic and cephalic veins are superficial pathways; identifying them matters when symptoms, a catheter, or a visible abnormality extends beyond the deep system. Confirm vessel identity with its course, neighboring structures, compressibility, and Doppler flow rather than color alone. Compress accessible veins in transverse view, using enough pressure to bring normal walls together. The clavicle blocks direct compression of much of the subclavian vein, so evaluate that segment with grayscale, color filling, and spectral flow. These observations supply indirect evidence, but they cannot recreate a compression test beneath bone.

Worked example: The axillary vein closes fully under transverse probe pressure. Beneath the clavicle, the subclavian vein is visible with color flow, but the probe cannot compress it. Record axillary compressibility and the subclavian color and spectral findings separately. A flowing subclavian segment is observed; complete compressibility of that hidden segment has not been demonstrated.

Watch the distinction: A colored subclavian lumen does not prove that every part of the vein is free of thrombus. Partial obstruction may permit flow, and bone prevents direct compression.

42. Use systematic venous compression

Compression is the central direct test for thrombus in veins that can be reached by the probe. In transverse view, apply controlled pressure at successive points along the named segment and verify that the anterior and posterior walls meet. Scan the entire accessible course rather than sampling only its ends, since a short abnormal segment can sit between normal ones. If the walls fail to meet, look for intraluminal material, a duplicated vein, or a nearby structure that might explain the image. Adjust depth and probe position before concluding that coaptation failed. Color and spectral Doppler help describe residual flow and extent, but flowing blood can pass beside nonocclusive material. Document where normal compression ends and resumes so the interpreting physician can locate the finding. The Society for Vascular Ultrasound provides broader vascular ultrasound education resources.

Worked example: During serial transverse compression, a femoral vein closes above a 2 cm segment and again below it. Within that segment, its walls remain apart and grayscale shows internal material. Save images of the noncompressible span and adjacent normal sites, then assess color flow through or around it. Describe the involved vein and measured extent for interpretation.

Watch the distinction: A single compressible image cannot clear an entire vein. Short thrombotic segments may be missed unless compression proceeds systematically along the accessible vessel.

Reference: [3]

43. Investigate proximal venous obstruction

Respiration changes abdominal and thoracic venous pressure, producing phasic flow in unobstructed proximal pathways. A common femoral waveform that stays unusually continuous can therefore raise concern for obstruction farther upstream, especially when the opposite side shows clear respiratory variation under comparable conditions. First check that the patient is breathing normally and that Doppler scale, wall filter, sample position, and gain allow variation to appear. Compare sides, inspect the vein directly where possible, and follow the iliac pathway if accessible. Distal augmentation can demonstrate a response to a controlled squeeze below the probe, but its presence alone cannot exclude a proximal lesion. Indirect signs localize a question for further scanning; they do not identify a clot's exact site or cause. Record both the waveform difference and any unseen segments.

Worked example: The right common femoral vein shows nearly constant forward flow, while the left waveform varies with ordinary breathing. Both samples use similar settings, and the patient is breathing evenly. Recheck the right trace, inspect the accessible right iliac vein with color and spectral Doppler, and document where bowel gas prevents assessment. Report the asymmetry as an indirect proximal clue.

Watch the distinction: Continuous femoral venous flow does not by itself prove iliac thrombosis. Breathing, positioning, settings, and other causes of impaired outflow can alter respiratory variation.

44. Describe thrombus-related changes

Describe what the vein looks like and how it behaves before suggesting a thrombus pattern. A distended vein that will not compress and contains relatively soft appearing material can be associated with more recent thrombosis. A narrowed, irregular vein with wall thickening, internal bands, partial reopening, or collateral channels can reflect chronic postthrombotic change. Echo brightness alone is unreliable because machine settings and clot composition affect appearance. A patient may also have new material superimposed on older damage, making a single age label misleading. Compare prior images for changes in caliber, compressibility, and flow channels. Trace the proximal and distal extent and note whether any channel remains patent. Your sonographic record gives the physician observable evidence; ultrasound cannot determine a precise date when thrombus formed.

Worked example: One segment is small, has thickened walls, and drains through visible collaterals; a prior study shows similar findings. An adjacent segment is newly distended and noncompressible. Document each segment separately, including its current flow and comparison with the prior study. The pattern raises a question of new change beside older disease without assigning either finding an exact age.

Watch the distinction: Calling bright material old and dark material new oversimplifies thrombus assessment. Echogenicity varies with equipment and tissue, so use structure, flow, and prior studies.

45. Test venous reflux

Venous valves should limit backward flow when pressure reverses. To test them, position the patient so the vein is adequately filled, identify the precise segment and junction, and provoke flow with a controlled distal compression and release or another suitable maneuver. Sample the resulting spectral waveform and measure the duration of reverse flow from its onset to return toward baseline. A brief reverse component can follow a maneuver even when a valve functions, so interpret duration using the criterion supplied for that vein and examination. Keep the Doppler angle and sample position stable, and avoid mistaking probe motion or an adjacent artery for reflux. Document patient position, maneuver, direction, duration, and named vein. A comparison across visits is meaningful only if testing conditions are reasonably comparable.

Worked example: In a hypothetical case, a standing great saphenous segment shows 1.2 seconds of reverse flow after distal compression release. The case defines reflux as reverse flow longer than 0.8 seconds for that segment. Because 1.2 exceeds 0.8 by 0.4 seconds, classify this measurement as reflux under the supplied rule, and record the site, position, and maneuver.

Watch the distinction: Any visible color reversal is not automatically reflux. The maneuver can cause brief backward flow, and a defensible conclusion needs a measured duration and the stated criterion.

46. Separate venous disease from mimics

Pain and swelling near a vein may come from tissue outside it. A popliteal fluid collection, hematoma, enlarged node, or soft tissue edema can resemble venous disease clinically and may distort the sonographic view. Locate the finding relative to the vein in two planes, assess its internal echoes and any color flow, and then examine the venous segments independently. A compressible vein with appropriate flow argues against thrombus in that examined segment; it does not clear veins that were not adequately seen. Conversely, an extravascular collection does not explain away a noncompressible vein elsewhere. Save images showing both the abnormal tissue and the assessed vein, and describe the scan limits. This lets the interpreting physician separate a vascular observation from an incidental or competing explanation for symptoms.

Worked example: A patient reports pain behind the knee. Ultrasound shows a fluid collection beside the popliteal vessels, while the popliteal vein compresses fully and has flow on color imaging. Document the collection's location and appearance, and record the venous segments actually examined. The collection is an extravascular finding; it does not establish popliteal venous thrombosis.

Watch the distinction: A painful lump beside a vein is not necessarily thrombus. Confirm whether the abnormality is inside the vessel and test the vein itself.

47. Orient the abdominal vascular survey

Use the aorta and inferior vena cava as central landmarks, then follow their branches and tributaries rather than identifying vessels from one image. The aorta divides into common iliac arteries; the renal arteries arise laterally, while the celiac and superior mesenteric arteries arise anteriorly. The renal veins drain toward the vena cava, and portal blood enters the liver through a separate venous pathway. Grayscale shows the vessel course and wall, color establishes a flow channel, and spectral Doppler helps confirm arterial or venous character. Deep targets and bowel gas weaken the beam or hide origins, so change the probe window, patient position, depth, or frequency as needed. Breathing may briefly improve a window but can shift the sample. Record a segment as limited when its lumen remains unseen.

Worked example: Bowel gas hides the celiac origin in a supine longitudinal view. After turning the patient slightly and scanning through a different window, the origin is still not visible, although the more distal vessel shows flow. Save the obtainable images and state that the origin was not assessed directly. Distal flow does not establish that the hidden origin has no narrowing.

Watch the distinction: Seeing flow beyond a gas obscured origin does not prove the origin is normal. A stenosis may allow downstream flow while the decisive segment remains hidden.

48. Measure aortic and iliac dilation

An aortic or iliac diameter is most useful when the calipers, plane, and measurement location are reproducible. Find the widest visible segment and measure from outer wall to outer wall, perpendicular to the vessel's long axis. Obtain orthogonal views where possible, because an oblique cut through a round vessel stretches its apparent diameter. Distinguish the outer sac boundary from the remaining flow channel: mural thrombus can make the patent lumen much smaller than the full vessel. State which segment was measured and compare the same type of measurement with earlier examinations. A change may reflect true growth or differences in angle and wall definition, so check the images before interpreting a small difference. The sonographer records the dimensions and related flow findings for physician interpretation.

Worked example: An oblique image gives an apparent aortic width of 4.8 cm. A carefully aligned view perpendicular to the vessel axis measures 4.2 cm outer wall to outer wall. The apparent values differ by 0.6 cm, but the perpendicular 4.2 cm measure is the defensible diameter. Document its plane and location for comparison with a prior study.

Watch the distinction: Measuring only the color filled lumen can understate aneurysm size when mural thrombus is present. Use the outer walls and a perpendicular plane.

49. Evaluate abdominal arterial lesions

Evaluate an abdominal arterial abnormality as a sequence: structural change at the suspected site, local flow behavior, and downstream consequence. Plaque or narrowing may produce a focal velocity rise and color disturbance; flow beyond a substantial lesion may become delayed and damped. An occluded segment lacks demonstrable flow despite appropriate settings, and collateral pathways may restore a distal signal. Mural thrombus sits within a dilated or diseased vessel while leaving a smaller flowing channel. A suspected dissection calls for views of a flap and any separate flow channels, with attention to their extent. Do not assign all downstream waveform changes to the first visible plaque, since multiple lesions or altered cardiac output may coexist. Label each sampled level and record technical gaps so the physician can connect anatomy to physiology.

Worked example: A left iliac artery contains visible plaque and a focal high velocity jet. Immediately beyond it, color shows disturbed flow; the left common femoral waveform has a slower, rounded systolic rise compared with the right. Document the jet, nearby reference flow, and femoral waveforms. Their sequence supports a left proximal inflow lesion, while the precise severity depends on applicable criteria.

Watch the distinction: A damped femoral waveform alone does not locate the lesion exactly. Trace the upstream pathway and look for a focal abnormality and intervening flow changes.

50. Assess renal artery flow

Trace each renal artery from its aortic origin toward the kidney, sampling accessible proximal, middle, and distal segments. Record aortic reference flow when a renal to aortic velocity ratio is requested; calculate the ratio only when both measurements are technically sound and taken under comparable conditions. Align the Doppler cursor with the actual flow stream, since angle error can exaggerate a velocity. Intrarenal waveforms add downstream context: a delayed systolic rise may support a proximal flow limiting lesion, but can also reflect other hemodynamic factors. A focal jet, grayscale narrowing, poststenotic disturbance, and intrarenal change form stronger evidence together than one number. If bowel gas hides the origin, state that limitation rather than treating a distal sample as proof of origin patency. Review SPI Doppler physics when checking angle and velocity measurements.

Worked example: In a hypothetical study, renal peak systolic velocity is 240 cm/s and the valid aortic reference is 80 cm/s. The ratio is 240 ÷ 80 = 3.0, with units canceling. If the case defines a positive ratio as greater than 3.5, this result does not meet that rule. Check for a focal jet and intrarenal waveform changes before describing the overall evidence.

Watch the distinction: A renal velocity ratio is not meaningful if the aortic reference is unreliable or the renal sample is misaligned. Validate both measurements before dividing.

51. Assess mesenteric arterial flow

Identify the celiac and superior mesenteric arteries by their origins and branching course before comparing velocities. Mesenteric flow responds to digestive demand: after a meal, more blood may move forward during diastole, particularly in the superior mesenteric artery. Respiratory motion changes vessel position and can alter sampled angle or compression, while a deep vessel challenges beam alignment. Record whether the patient was fasting or had eaten, the sampled segment, and the breathing condition when a difference matters. At a suspected lesion, compare focal velocity, nearby reference flow, color disturbance, and downstream waveform rather than interpreting a single peak in isolation. A longitudinal comparison is strongest when patient preparation and sampling conditions match. If the origin remains hidden, describe the accessible portion and the limitation.

Worked example: A prior fasting superior mesenteric study shows relatively little forward diastolic flow. Today's study, obtained soon after a meal, shows more forward diastolic flow without a focal jet or visible narrowing. Record the feeding state and comparable vessel segment. The changed waveform can reflect increased digestive demand, so it does not by itself establish progression of stenosis.

Watch the distinction: Higher postmeal diastolic flow is not automatically a new lesion. Interpret mesenteric waveforms alongside meal state, vessel identity, focal anatomy, and sampling conditions.

52. Interpret hepatic flow direction

Direction is anatomical, not a color name. Establish the probe marker, vessel course, and Doppler baseline before calling flow toward or away from the liver. Portal venous flow normally carries blood from the splanchnic circulation toward the liver and has a largely continuous waveform with gentle variation. Hepatic veins drain from the liver to the vena cava and show stronger variation from cardiac pressure changes. The hepatic artery supplies pulsatile inflow toward the liver. Color red or blue only describes motion relative to the transducer under the current map, so reversing probe orientation can reverse the displayed color without changing true flow direction. Use spectral Doppler to confirm the waveform and direction, then label the sampled vessel and anatomical direction. Report a reversed portal direction clearly for physician interpretation.

Worked example: A portal branch displays color that seems reversed from an earlier image. After checking the probe marker and tracing the branch to the main portal vein, spectral Doppler confirms flow away from the liver. A nearby hepatic artery remains pulsatile toward the liver. Document both vessels and their directions; the arterial signal does not cancel the reversed portal finding.

Watch the distinction: Red does not always mean flow toward the liver. Color depends on transducer orientation and map settings, so confirm anatomical direction with vessel tracing and spectral Doppler.

53. Follow abdominal venous collaterals

When a major abdominal vein carries little or no detectable flow, first make low flow visible: reduce an excessive color scale, adjust gain and wall filter, and search from another window. Then trace the vein and its expected drainage to see whether blood has found alternate channels. Small vessels around a poorly flowing portal segment may represent collateral pathways formed around obstruction. Enlarged alternate drainage can also accompany raised portal pressure, while abnormal hepatic venous or caval outflow may redirect flow through other veins. The location and direction of each channel matter more than a single colorful image. Distinguish vessels from adjacent ducts with continuity and spectral character. Document direct lumen findings, collateral courses, flow direction, and obscured segments; the physician integrates these with clinical history and other imaging.

Worked example: A portal vein segment has no detectable color or spectral signal after low flow settings and alternate windows are tried. Multiple small channels around that segment carry venous flow toward the liver. Save images of the expected main lumen and the collateral network, including directions and settings. Report the absent detectable main-lumen flow and alternate channels for interpretation.

Watch the distinction: No color in the main portal vein is not enough to declare occlusion. Slow flow, depth, and settings may conceal a patent channel.

54. Map a bypass before measuring it

Reconstructed arterial pathways need a map before velocity measurements make sense. Review the operative description or prior imaging for the graft's source artery, conduit type, course, and target vessel. Then trace native inflow, proximal anastomosis, the entire accessible graft, distal anastomosis, and runoff. A vein graft may have variable caliber or valves; a synthetic graft has different wall echoes. Both can run superficially or cross where a native artery would not. Label spectral samples by their actual position so a later focal change can be compared with the same site. Sample across anastomoses and any color disturbance, while noting bends that can elevate measured speed through geometry. If a segment cannot be followed, record the gap and avoid describing continuous patency through it.

Worked example: A femoral to popliteal bypass runs just under the skin while the native artery follows a deeper route. Starting at the inflow artery, trace the graft through its proximal anastomosis, conduit, distal anastomosis, and popliteal runoff. Label each saved image and velocity by location. The superficial channel is thereby identified as the graft rather than mistaken for native anatomy.

Watch the distinction: A patent signal in one graft segment does not establish patency through both anastomoses and runoff. Trace the whole accessible reconstruction before summarizing it.

55. Surveil grafts and stents

Surveillance asks whether flow through a known reconstruction has changed and where. Record grayscale lumen appearance, color filling, and spectral velocities at inflow, throughout the graft or stent, at both ends, and in outflow. A focal acceleration relative to a nearby reference sample suggests narrowing, especially when color disturbance and a changed distal waveform accompany it. Ratios require comparable Doppler angles and correctly labeled sites; a bend, caliber change, or stent geometry can alter velocity without the same implication as native artery plaque. Compare with earlier studies using the same segments to identify a new or worsening pattern. Also look for very low flow or absent flow, since threatened or established graft failure may have no high velocity jet. Apply only the interpretation rule provided for that reconstruction.

Worked example: Hypothetical graft velocities are 60 cm/s in an adjacent segment and 240 cm/s at a visible focal narrowing. The local ratio is 240 ÷ 60 = 4.0. If the case defines a ratio above 3.5 as severe graft stenosis, this meets that rule. Record the jet, reference site, color disturbance, distal waveform, and change from prior imaging.

Watch the distinction: A single high graft velocity can result from a bend or altered conduit size. Compare an adjacent valid reference, visible lumen, and downstream flow.

56. Recognize reconstruction complications

A new mass or absent signal near a reconstruction has several distinct explanations. Thrombosis fills or blocks the graft lumen and removes expected flow through the affected segment. An anastomotic pseudoaneurysm is an extraluminal sac communicating with the artery through a neck; color may show circulating flow and spectral Doppler may show changing direction at the neck. A perigraft fluid collection can be clear or complex on grayscale yet lack internal blood flow. Check gain and scale before calling a structure avascular, and search for a connection in more than one plane. Record whether the graft itself remains patent, the size and site of a sac or collection, and any adjacent flow disturbance. Describe these observations promptly when they may change care, leaving the final diagnosis to the interpreting clinician.

Worked example: Near a distal anastomosis, one mass contains color flow entering through a narrow connection to the artery. A separate nearby collection has internal echoes but no flow after Doppler settings are checked. Image the neck, sac, graft lumen, and avascular collection separately. The connected flowing sac supports pseudoaneurysm, while the second finding needs its own structural description.

Watch the distinction: Every perigraft mass is not a pseudoaneurysm. Demonstrate a vascular connection and internal flow before using that description; an avascular collection has a different pattern.

57. Trace dialysis access anatomy

Dialysis access creates a new low resistance path, so native vessel names alone do not describe its circulation. First determine whether the access is a surgically joined native vein or a synthetic graft. Trace the feeding artery, anastomosis, conduit, draining vein, and more central venous outflow. Note usable straight segments for diameter and volume flow measurements, and distinguish expected high flow near the anastomosis from a focal jet at a narrowed segment. Inspect any aneurysmal enlargement, mural material, or abrupt caliber change. A palpable thrill can help locate the access but cannot establish that every downstream segment is open. Label each image by its place in the circuit, because a stenosis in inflow, conduit, or outflow has different hemodynamic effects.

Worked example: An upper arm fistula has a strong thrill near its arterial connection, but the outflow vein becomes less prominent farther up the arm. Trace from the inflow artery through the anastomosis and along the draining vein, sampling before, within, and after any focal change. Document where the outflow is poorly seen; the thrill alone does not clear that segment.

Watch the distinction: A strong thrill near an access does not prove unobstructed venous drainage. High local flow may coexist with a downstream outflow lesion.

58. Calculate access volume flow

Volume flow estimates the amount of blood passing a chosen access segment per minute. For a nearly circular lumen, area equals π times radius squared, or πd²/4. Multiply that area in cm² by the time averaged mean velocity in cm/s to obtain cm³/s, then multiply by 60 to obtain mL/min. Use a straight, representative segment and a diameter measured perpendicular to its walls; avoid a focal stenosis, marked turbulence, or an irregular aneurysmal section. Keep the Doppler sample across the flowing lumen and correct its angle to the flow stream. Diameter error is amplified because diameter is squared, while peak systolic velocity is not a substitute for time averaged mean velocity. Repeated measurements help reveal instability. Practice calculations in ARRT VS practice questions.

Worked example: For a hypothetical diameter of 0.60 cm and time averaged mean velocity of 40 cm/s, radius is 0.30 cm and area is π × 0.30² = 0.283 cm². Flow is 0.283 × 40 × 60 = about 679 mL/min. Measuring diameter as 0.66 cm instead gives about 821 mL/min, roughly 21% higher.

Watch the distinction: Using peak systolic velocity in the flow equation overstates mean volume flow. The formula requires time averaged mean velocity and a carefully measured lumen diameter.

59. Assess access dysfunction and steal

Access dysfunction can arise at several points in the circuit. Inflow narrowing limits blood entering the access; an outflow stenosis produces a local jet and may raise venous pressure, with swelling or collateral veins. Thrombosis can remove expected flow and thrill. Repeated puncture or altered wall stress may produce aneurysmal enlargement, which requires measurement and assessment for mural material or adjacent narrowing. Hand pain, coolness, or weakness raises a different question: whether the access diverts enough arterial flow to impair distal perfusion. Examine distal arterial waveforms and direction along with access flow and symptoms. These patterns can coexist, so a conspicuous outflow lesion should not end the hand assessment. Document anatomy, velocities, flow direction, and relevant symptoms for physician evaluation.

Worked example: A fistula patient has new arm swelling and hand discomfort. Duplex shows a focal venous outflow jet with reduced flow beyond it, supporting an outflow problem. Because hand symptoms coexist, assess the feeding artery and distal handward arterial flow as well. Record the outflow lesion and distal perfusion findings separately; swelling alone does not establish access related steal.

Watch the distinction: Hand pain in a patient with an access is not automatically steal physiology. Correlate symptoms with distal arterial flow and consider concurrent outflow disease.

60. Surveil endovascular aneurysm repair

After endovascular aneurysm repair, surveillance follows both the aneurysm sac and the graft that excludes it. Measure the maximum outer wall sac diameter in a reproducible plane, comparing the same region with earlier studies. Trace the main graft and each limb for color filling, focal velocity changes, and distal flow. Search around the graft for flow within the excluded sac, using settings sensitive enough for slow signals and more than one view to confirm location. Such flow raises concern for an endoleak, but Doppler appearance alone may not establish its source or type. A sac change can be important even if no flow is detected, because deep or slow flow may escape ultrasound detection. Record the measurement method, change, flow site, and visibility limits for physician assessment.

Worked example: A hypothetical repaired sac measures 5.1 cm today and 4.7 cm on a comparable prior image, an increase of 0.4 cm, or 4 mm. Both graft limbs show flow, while color appears outside the graft lumen within the sac. Confirm the color location in another view, record the measurement planes, and report the sac change and possible endoleak signal.

Watch the distinction: Patent graft limbs do not rule out flow into the excluded sac. Inspect outside the graft and compare sac size with earlier measurements.