How to Analyze the Centerline of the Aorta with Materialise Mimics Core

Select a solid anatomical part for the analysis. Note: Hollow models that only contain vessel walls will result in a centerline within the walls rather than the lumen.

Initiating the Fit Centerline process:

1. Navigate to the Analyze menu.
2. Select Fit Center Line to launch the tool.

Configuring the parameters:

1. Adjust Smoothing to control the smooth factor. Higher values (default 0.3) result in lower curvature variability, while lower values are better for geometry with very short turns.
2. Set Branch filtering to remove segments shorter than a specified length (set to 0 to keep all branches).
3. Set the Noise threshold (typically between 0.005 and 0.06) to filter out side branches caused by surface noise. Use small increments of 0.01 or less when adjusting this sensitive parameter.

Selecting the mode and resolution:

1. Choose Automatic mode for the software to determine resolution based on part volume, or Manual mode for custom control.
2. In manual mode, you can specify the Resolving resolution. Smaller values increase detail but lead to longer calculation times.
3. Adjust the slider for Angle threshold in manual mode to influence curve interpolation and branch point positions.
4. Optionally, you can check the Equidistant control points box to resample the line with evenly spaced points for standardized measurements. Specify your preferred distance in the field below.

Performing the initial fit:

1. Click Apply to execute the first stage of the calculation.
2. Adjust the transparency of the model in the Object Properties window, located on the right side of your screen, to better view the resulting line in the 3D viewport.

Real-time refinement:

1. Use the Smoothing and Branch filtering sliders to see instant changes to the calculated line.
2. Click Reset if you need to go back to the first stage to modify locked parameters.
3. Click OK once satisfied to add the centerline to your Object List.

Post-processing:

1. Right-click the centerline in the object list to access Centerline post-processing for further iterations of smoothing or filtering.

Editing control points:

1. Select Edit Centerline Control Points from the right-click menu.
2. Click and drag any point to a new location as needed.
3. Check Allow control point editing beyond part boundaries if you need to move points outside the object surface for simulations like catheters or stents.

Combining advanced operations:

1. Use the Grow segment of the centerline tool to extend branches. First, click the segment you want to grow, then click the target location in the 3D view.
2. Remove unwanted branches by using the Delete Centerline Part operation or by selecting segments within the Edit Branches tool.

Performing measurements:

1. Open the Measure menu in the top navigation bar.
2. Select Best Fit diameter and click any point on the centerline to see the local vessel diameter.
3. Select Tortuosity and click a start and end point to calculate the complexity of the path between them.
4.  Refer to the user manual under the Help menu to learn how to perform other measurements.

Exporting measurement data:

1. Select the centerline and open the Edit Branches tool.
2. Select the specific branch you wish to analyze.
3. Click Export, choose your desired measurement types, and Save the data as a text file.
4. Refer to the legend at the top of the document to help you understand the findings.

Summary and Python API automation:

1. Alternatively, you can use the Fit Centerline Python API in the scripting module to automate the centerline fitting process.
2. Consult the Scripting guide under the Help menu for more information.