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[Introduction to the study of the Willis circle with transcranial color Doppler: methodological notes and preliminary
R Lagalla1, G Caruso, S Pappalardo
1Instituto di Radiologia P. Cignolin, Policlinico Universitario, Palermo.
Insights
Transcranial color-Doppler (TCD) imaging visualizes intracranial blood flow, effectively imaging the middle cerebral artery. However, TCD shows limited success in visualizing the anterior and posterior cerebral arteries within the Willis circle.
Area of Science:
- Neurology
- Medical Imaging
- Vascular Ultrasound
Background:
- Intracranial circulation assessment traditionally relies on pulsed-wave Doppler US, facing limitations due to the skull's barrier effect.
- Transcranial color-Doppler (TCD) utilizes specialized transducers to overcome the skull barrier, enabling direct visualization of intracranial vessels.
Purpose of the Study:
- To evaluate the feasibility and initial experience of transcranial color-Doppler (TCD) for imaging the Circle of Willis in healthy volunteers.
- To assess the visualization rates of major intracranial arteries using TCD.
Main Methods:
- Employed an ATL Ultramark 9HDI with a 3.5 MHz phased array transducer and 2 MHz Doppler frequency.
- Performed TCD imaging on 30 healthy volunteers (17-75 years) to visualize the Circle of Willis.
- Utilized specific settings: 3000 Hz PRF, 80% color gain, and 100 Hz wall filters.
Main Results:
- Successfully visualized the middle cerebral artery in all subjects.
- Demonstrated limited visualization of the posterior cerebral artery (23.3%) and anterior cerebral artery (10%).
- TCD is valuable for assessing normal intracranial blood flow and speed values.
Conclusions:
- TCD is a promising technique for studying intracranial hemodynamics, particularly the middle cerebral artery.
- Further advancements are needed to improve visualization rates for other components of the Circle of Willis.
- TCD shows limited utility in characterizing intracranial tumor tissue.
Abstract:
To date, adult intracranial circulation has been studied only with pulsed-wave Doppler US, which is a useful diagnostic tool even though several technical and practical limitations are related to the difficult location of intracranial vessels. Recently, dedicated color-Doppler transducers have been proposed, which can pass through the skull which makes a physiologic barrier for the US beam: this technique has been called transcranial color-Doppler (TCD). We report on our personal experience with TCD in 30 healthy volunteers (12 men and 18 women, age range: 17-75 years) submitted to TCD for Willis circle imaging. We used an ATL Ultramark 9HDI unit with a phased array transducer (3.5 MHz) and 2 MHz Doppler frequency; the PRF was 3000 Hz, with 80% color gain. 100 Hz wall filters were used. The middle cerebral artery was always shown correctly in all subjects, while the posterior one was depicted only in 7 cases (23.3%); in contrast, the anterior cerebral artery was demonstrated in 3 cases only (10%). Nowadays, TCD is mostly applied to normal intracranial circle studies, to assess normal blood speed values more accurately. To this purpose, both the direct visualization of blood vessels and the flowmetric values obtained measuring the incidence angle are useful pieces of information. TCD permits a more accurate study of intracranial local blood flow in the Willis circle and of its changes in pathologic conditions. In contrast, TCD yield is poor in characterizing intracranial tumor tissue.