Vascular Ultrasonography

Vascular Ultrasonography

Vascular Ultrasonography

On this page

Doppler Fundamentals - Wave Wisdom

  • Doppler Effect: Frequency shift from moving RBCs.
  • Doppler Equation: $f_D = \frac{2 \cdot f_t \cdot v \cdot \cos\theta}{c}$
    • $f_D$: shift; $f_t$: transmitted freq; $v$: velocity; $c$: sound speed (1540 m/s).
    • $\theta$: Doppler angle. Optimal $\le \textbf{60}^\circ$; $\textbf{90}^\circ \implies$ no shift.
  • Modes:
    • CW: No aliasing/range gate. For high velocities.
    • PW: Range-gated; aliasing if $f_D >$ Nyquist Limit ($PRF/2$).
  • Color Doppler: Mean velocity & direction. 📌 BART: Blue Away, Red Towards.
  • Power Doppler: ↑ sensitivity for low flow; no direction/velocity info.
  • Spectral Doppler: Velocity-time waveform. Doppler angle error in vascular ultrasound

⭐ Velocity accuracy depends on Doppler angle ($\theta$); $> extbf{60}^\circ$ causes significant error. At $\textbf{90}^\circ$, no shift detected.

Arterial Assessment - Plaque Patrol

  • Plaque Morphology:
    • Echogenicity: Hypoechoic (lipid-rich, higher risk ⚠️), isoechoic, hyperechoic (fibrous), calcified (acoustic shadowing).
    • Surface: Smooth, irregular, ulcerated (embolic risk ↑).
    • Location & Extent.
  • Stenosis Quantification:
    • B-mode: Direct visualization.
    • Color Doppler: Flow acceleration, aliasing.
    • PW Doppler: ↑PSV, spectral broadening. PSV ratio: $PSV_{stenosis} / PSV_{pre-stenosis}$.
  • Carotid Stenosis Grading (SRU Consensus Criteria Simplified):
    • <50%: PSV <125 cm/s.
    • 50-69%: PSV 125-230 cm/s, ICA/CCA PSV ratio 2.0-4.0.
    • 70% (but not near occlusion): PSV >230 cm/s, ICA/CCA PSV ratio >4.0.
    • Near Occlusion: Markedly reduced lumen, low velocity flow ("string sign").
    • Total Occlusion: No flow.
  • Peripheral Arterial Disease (PAD):
    • Waveform changes: Triphasic (normal) → Biphasic (mild/mod) → Monophasic (severe).

⭐ Distal to significant stenosis, a "Tardus Parvus" waveform (slow systolic upstroke, low amplitude) is characteristic.

Venous Evaluation - Clot Quest

Error: Failed to generate content for this concept group.

Specialized Scans - Vascular Virtuoso

  • Transcranial Doppler (TCD):
    • Assesses intracranial arteries (MCA, ACA, PCA, VA, BA).
    • Indications: Vasospasm (post-SAH; Lindegaard ratio >3), sickle cell stroke risk (MCA TAMMV >200 cm/s), brain death, PFO detection. TCD waveform analysis for high ICP and vasospasm
  • Contrast-Enhanced Ultrasound (CEUS):
    • Microbubble contrast improves vessel/perfusion imaging, lesion characterization.
    • Uses: TIPS patency, endoleak detection (post-EVAR).
  • Intravascular Ultrasound (IVUS):
    • Catheter-based, detailed vessel wall/plaque imaging. Crucial for guiding interventions (stenting).
  • Specific Applications:
    • Popliteal Artery Entrapment (PAES): Dynamic scan with flexion.
    • Thoracic Outlet Syndrome (TOS): Positional Doppler.
    • Erectile Dysfunction: Penile Doppler (PSV <30 cm/s = arterial insufficiency).

⭐ TCD in sickle cell: MCA TAMMV >200 cm/s indicates high stroke risk, guiding prophylactic transfusions.

High‑Yield Points - ⚡ Biggest Takeaways

  • Doppler effect is fundamental for assessing blood flow direction and velocity.
  • Color Doppler visualizes flow: BART (Blue Away, Red Towards transducer).
  • Spectral Doppler quantifies flow velocity and displays characteristic waveforms (e.g., triphasic).
  • Primary diagnostic tool for DVT (deep vein thrombosis) - non-compressibility of vein is key.
  • Crucial for carotid artery stenosis assessment (PSV, EDV, ICA/CCA ratio).
  • Evaluates peripheral arterial disease (PAD), often correlating with Ankle-Brachial Index (ABI).
  • Monitors renal transplant vascularity for complications like stenosis or thrombosis.

Practice Questions: Vascular Ultrasonography

Test your understanding with these related questions

Investigation of choice for screening of proximal internal carotid artery stenosis is :

1 of 5

Flashcards: Vascular Ultrasonography

1/10

Ultrasound elastography is used to assess the _____ of tissue.

TAP TO REVEAL ANSWER

Ultrasound elastography is used to assess the _____ of tissue.

hardness

browseSpaceflip

Enjoying this lesson?

Get full access to all lessons, practice questions, and more.

Start Your Free Trial