Applying Image Operations

You can use the Overwrite option in the Image operations box to overwrite the values of a selected dataset that correspond to labeled voxels within a region of interest or the selected class(es) of a multi-ROI. You can perform this operation if you need to permanently remove unwanted markings, artefacts, or objects from an image, or if you need to create an image mask.

1. Select the required region of interest or multi-ROI class(es).
2. Select the dataset that you need to modify in the Image operations box in the ROI Tools panel.

   

3. Click the Overwrite button.

   The Set Value dialog appears.

4. Select the intensity value that will be applied to all voxels of the selected dataset that intersect with the region of interest or the selected class(es) of the multi-ROI.

   

5. Click OK to apply the change.

In the Otsu thresholding technique, the optimal value that minimizes the weighted within class variances of two basic classes — Foreground and Background — is computed. Splitting an ROI into these components, using the dataset values that correspond to the labeled voxels in the region of interest, can provide masks for further segmentation. You should note that minimizing the within class variance is the same as maximizing the between class variance.

1. Analyze the histogram of the region of interest, recommended (see Analyzing Histograms Extracted From ROIs).
2. Select the required region of interest or multi-ROI class in the Data Properties and Settings panel.
3. Select the required dataset in the Image operations box in the ROI Tools panel.

   

4. Click the Split at Otsu button.

   The region of interest is split into two ROIs that represent the two basic classes — foreground and background — and are added automatically to the Data Properties and Settings panel.

In cases in which it is necessary or useful to restrict measurements or processing to a subset of the data that needs to be analyzed, the Export option lets you extract a subset of a dataset that only includes data values that intersect with a selected region of interest.

1. Select the required region of interest in the Data Properties and Settings panel.
2. Select the required dataset in the Image operations box in the ROI Tools panel.

   

3. Click the Export button.

   The new dataset appears in the Data Properties and Settings panel.