1. Four-Dimensionally Guided Three-Dimensional Color-Doppler Ultrasonography (4D/3DC-US) to Quantify Carotid Artery Stenosis
Animated illustration of sequential steps (please click to stop and to proceed): 1. live (4D) gray-scale preview (.mp4 movie file), 2. 3D image adjustment and multiplanar rendering (this step needs to be done separately for the minimal lumen and the distal vessel segment), 3. stenosis measurement.

2. Step 1: On-line orientation with 4D gray scale live previewsB
A: Sagittal
B: Transverse
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Sagittal
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Transverse C
C: Coronal
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Coronal
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4D live images shown in 3 perpendicular planes are focused on the center of a stenotic plaque at the origin of the right internal carotid artery (planes A-C). View A displays the longitudinal-, view B the transverse and C the coronal section. Sections A, B and C were used to position the probe at an appropriate angulation around the neck and to decide on sufficient image quality (e.g. no shadowing) for the following acquisition of corresponding 3D color-Doppler views of internal carotid arteries (see steps 2 and following). Aim: to localize stenosis and optimize the probe angulation around the neck.
Time demanded : < 30 seconds.

3. Step 1: On-line orientation with 4D gray scale live previews
A: Sagittal
B: Transverse
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Sagittal
Z axis
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Transverse
C: Coronal
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Coronal
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Probe
orientation
See Online Video 1
4D live images. Please click to stop and to proceed.

4. Step 2 A: Acquisition of a static 3D color-Doppler volume datasetB
A: sagittal
B: transverse
C: coronal
D: volume rendered view 1 2 3 4 5
1 cm
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Transverse
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Sagittal
Z axis C
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Coronal
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The 3D color-Doppler volumetric raw dataset of the same carotid stenosis was acquired at the same probe angulation as adjusted with the 4D previews. Static images A (saggital), B (transverse) and C (coronal) are judged for sufficient image quality. Note the color aliasing phenomenon (very bright colors) within the narrowed lumen in A and B (red arrow). 1 = skin level, 2 = internal jugular vein, 3 = internal carotid artery middle segment outflow, 4 = narrowed stenotic lumen at the origin of the internal carotid artery, 5 = common carotid artery.
Aim: to illustrate the same views of 4D B-mode imaging with luminal color filling.
Time demanded: < 30 seconds.

5. A B 1 cm Step 2 B: Panning of still-frames to the stenosis
Further adjustment and rendering is displayed for sections A and B. Images were focused and zoomed on the center of the stenosis. The red arrow points at the minimal lumen of a transverse view (section B), yet not coaxially rendered in plane A so the true minimal lumen is not displayed. An analogous adjustment for the distal vessel segment is displayed at the end of the slide show.
Aim: to center on the middle of the lumen at the selected measurement location.
Time demanded : < 10 seconds.

6. Step 2 C: Completion of multiplane rendering at the minimal lumenB
1 cm
Image rotation around the z-axis in image A and exact centering to the middle of the lumen at the measurement location in A and B (red arrows). This results in an orthogonal view to the centerline (dashed white line in image A), controlled by the perpendicular transverse view B. Note that the MLD is little smaller in B after completion of this rendering step than shown after step 2B.
Aim: to render images strictly perpendicular to the centerline at the measurement location and to depict the true minimal vessel diameter at the adjusted location.
Time demanded: < 10 seconds.

7. A B 1 cm Step 3: Luminal measurement
The red arrow points at the minimal lumen of a coaxially rendered sagittal view (A and B). Luminal measurement is displayed (yellow crosses, MLD = 0.7mm).
Aim: To measure diameters at the minimal lumen diameter and separately at the distal vessel segment (shown on next slides).
Time demanded: < 10 seconds.

8. A B 1 cm Analogous imaging and rendering of the distal vessel segment
A healthy segment with no plaques and parallel vessel walls distal to the stenosis is displayed. It was equivalently adjusted to the center as in step 2B. The cross section (image B) was coaxially rendered according to the longitudinal section similar to step 2C. Note that the vessel is curved in the longitudinal section A, so it disappears on the left border of the image. Note that there is no color aliasing within the decelerated distal segment.
Aim: To measure diameters of the healthy distal vessel segment.
Time demanded for 3D adjustment and rendering: < 20 seconds.

9. B A 1 cm Measurement of the distal vessel segment
After coaxial rendering of the longitudinal section controlled by the perpendicular cross section (image B) the inner diameter of the healthy vessel segment within parallel vessel walls was measured (yellow crosses, distal diameter = 4.2mm). A 84% NASCET stenosis is calculated according to the formula: NASCET (%) = (1 – minimal lumen / distal lumen) x 100; [( /4.2) x 100] = 84%.
Aim: To measure diameters of the healthy distal vessel segment and calculate NASCET stenosis.
Time demanded: < 10 seconds.