The Smoothing Tool offers a variety of smoothing filters with configurable input parameters and can be applied to either the Reference or input studies or both.
The Smoothing Tool can be accessed via the tool pull-down menu on the IVS front panel.
Upon selection of the Smoothing Tool, the Smoothing Operator window is displayed. Using this tool, any loaded data can be selected for smoothing by checking the appropriate Data boxes: Reference, Input 1 and Input 2 select the first three datasets loaded, and Input * selects the remaining datasets beyond those (see Data Manager for more information on manipulating more than three data sets simultaneously).
Select the desired smoothing algorithm from the available options in the Smoothing drop-down menu. Use the parameter fields to set appropriate values. The effect of the chosen smoothing filter will be previewed in 2D in the slice views; to remove the 2D preview, go back to 'None' in the drop-down menu of smoothing filters.
Currently available filters include:
Each filter uses a different subset of the configurable parameters; consult the table below if parameters other than the default settings are desired.
| Parameter | Description | Used by | Default Value |
| FWHM | Full-width half-maximum kernel size | Gauss | 1.00mm |
| Conductance | Parameter governing sensitivity to edge contrast | Gradient Anisotropic Diffusion, Curvature Anisotropic Diffusion | 1.00 |
| Iter | Number of iterations | Curvature Flow, Gradient Anisotropic Diffusion, Curvature Anisotropic Diffusion, Positivity Smoothing | 5 |
| CutOffFrac | If the fraction of voxels that are negative falls below this value, further iterations of the filter will not be performed. | Positivity Smoothing | 0.005 |
| Time Step | Stepsize, effectively analogous to kernel width | Curvature Flow, Gradient Anisotropic Diffusion, Curvature Anisotropic Diffusion | 0.125 |
After a left-click on OK, the smoothing function is executed; depending on the image size and filter selected this could take several seconds or more. Once the smoothing function is applied, any subsequent operations will be based on the smoothed images.
Each filter will have different edge-preserving and noise-reduction properties; choose the one that suits your application best.
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The positivity smoothing filter will typically take longer to run than the other smoothing filters, up to several minutes for larger images. This filter was specially designed to redistribute the activity across neighboring voxels such that the total sum of the image is preserved but the number of voxels with negative values is reduced. It is intended to be used to correct images reconstructed with FBP.
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