Inobitec DICOM Viewer

4.3. Merge layers

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Functionality is available in the Pro edition
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Fused layers do not always coincide, particularly in cases when two different studies are fused (Fig. 4.2). In this case, you need to merge layers.

To merge layers:

  1. Open the fused series in the Multiplanar Reconstruction window by clicking the MPR reconstruction PIC button on the toolbar.

  2. In the Multiplanar Reconstruction tab, open the Layers list panel by clicking the Choose layer PIC button. There is the Layers Merge Panel at the bottom of the Layers list panel (Fig. 4.3).

  3. Select the layer which must be merged with the base one.

  4. Merge layers automatically (see Section 4.3.1), manually (see Section 4.3.2) or by points (see Section 4.3.3).





Depending on the size and resolution of the user’s monitor, some of the tools in the layers merge panel may be hidden. Hidden tools in the layers merge panel are indicated by the symbol "...". There are two ways to display tools hidden in the panel:

  1. Move the cursor to the panel border so that it would look like this PIC , and drag the border holding the left mouse button.

  2. Click on "..." and select a hidden tool from the drop-down menu.

4.3.1 Merge layers automatically

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Functionality is available in the Pro edition
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Attention! Automatically merge layers is not available for series with the same "FrameOfReferenceUID" tag values. Typically, series of the same study have the same value for tag "FrameOfReferenceUID".

To merge layers automatically:

  1. Click the Merge layers automatically PIC button on the Layers Merge panel (Fig. 4.3). This starts the merging process, the Optimizing correlation dialog will open.

  2. To cancel the merging process, click the Cancel button in the Optimizing correlation dialog.

  3. When the merging process is completed, click the Done button.

  4. Merging quality can be poor if the tissue density on the merged layers is very different. In this case, check the Gradient correlation box on the Layers Merge panel and repeat steps 1-3.

  5. To change the merge accuracy, move the Accuracy slider on the Layers Merge panel. Move the slider to the right for maximum quality. High accuracy requires more time to merge.

To merge layers by part of their volume:

  1. Choose a layer you need to merge with the base layer.

  2. Create a segmented structure for this layer. The mask of the structure should conform to the volume to be merged. The merge is performed by mask rather than by the created segmented structure volume.

  3. Click the Merge layers automatically PIC button.

4.3.2 Merge layers manually

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Functionality is available in the Pro edition
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Attention! Manually merge layers is not available for series with the same "FrameOfReferenceUID" tag values. Typically, series of the same study have the same value for tag "FrameOfReferenceUID".

To merge layers manually:

  1. Click on the left side of the Manual layer fusion PIC button.

  2. Match the images in three projections. To do this:

    • drag the selected slice, holding the left mouse button or pressing the cursor management keys PIC , PIC , PIC and PIC ;

    • rotate the selected slice, holding the right mouse button;

    • zoom the selected slice in and out, holding the Ctrl key and the left mouse button.

  3. To cancel all transformations, click the Reset layer transformations PIC button.

  4. To cancel zoom, click the Reset layer zoom PIC button.

  5. To set the displacement step, click on the arrow on the right side of the Manual layer fusion button and select the item Set step... and set the value.

  6. When the slices are matched satisfactorily, close the MPR reconstruction tab. The Series fusion tab will reappear on the screen.

  7. Browse the series fusion images to see the result. If the result is unsatisfactory, repeat the merging proccess.

4.3.3 Merge layers by control points

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Functionality is available in the Pro edition
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Attention! Merge layers by control points is not available for series with the same "FrameOfReferenceUID" tag values. Typically, series of the same study have the same value for tag "FrameOfReferenceUID".

To merge layers by control points:

  1. Select the base layer on the Layers list panel.

  2. Activate the Fit layers by points PIC tool on the Layers Merge panel.

  3. Make all the layers transparent except the base one. To do this, move the slider to the left of the layer thumbnail down. The transparency slider is highlighted in red in Fig. 4.4.

  4. Put at least three control points on the image. Each point has its own colour and number.

  5. Select the layer that you want to fit with the base. Make all the layers transparent except this one.

  6. Put on this layer the same number of control points in the same places as on the base layer. Point numbering starts over again. The colours of the corresponding points are the same.

  7. If necessary, adjust the position of points on all three orthogonal planes. When you locate the cursor on a point, it is highlighted on all three orthogonal planes.

  8. To delete point, locate the cursor on it, right-click the mouse and select the Remove point item.

  9. To switch to slices containing a point, move the cursor to this point, right-click the mouse and select the Go to point item. The point on the current slice is brighter than others.

  10. To delete all points, click on the arrow on the right side of the Fit layers by points button and select the Remove all points item. In the dialog box that opens, click Yes to confirm the deletion, or click No to cancel.

  11. To change the point properties, click on the arrow on the right side of the Fit layers by points button and select the Points properties item. In the window that opens, set the diameter of the points.

  12. Click on the arrow on the right side of the Fit layers by points button and select the Fit layers item. The second layer will be moved in such a way that the corresponding points are as close to each other as possible.

  13. If necessary, adjust the position of the points and repeat the previous step again.

  14. If necessary, add the same number of points on all the layers.



Fig. 4.5 illustrates the example of control points location. Red dots (#1) are located on the tip of the nose, green (#2) on top, blue (#3) on the right eye.



If the points are set correctly, they match with little margin of error. If the points are set inaccuratly, the result looks something like in Fig. 4.6.



4.3.4 Export and Import Matrices of Merge Layers

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Functionality is available in a separate module which is activated in the Pro edition for an extra fee
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The DICOM Viewer exports and imports matrices of merge of layers into DICOM Spatial Registration IOD (modality REG).

To export merge of series, click the arrow on the right-hand side of the Export series registration to DICOM object PIC button and choose the Export series registration to DICOM object option (Figure 4.7).



In the dialog box Export to DICOM Registration (Figure 4.8) add the description of the exported merged series. By default, the series description is "Registration". Click OK button to export series or Cancel to cancel.



The exported merged series will be saved in the local storage as a new series with REG modality. A thumbnail for the new series will be added to the series panel in the study containing the base layer.

To import a matrix merged layers:

  1. Make a series fusion from the series for which the object was exported DICOM Registration. Pay attention to the order of the series selection. Select the first (base) layer.

  2. Click the arrow on the right-hand side of the Export series registration to DICOM object PIC button and choose the Import series registration from DICOM object option (Figure 4.7).

  3. In the dialog box Import from DICOM Registration (Figure 4.9) select a REG modality series to import. Click OK button to import series or Cancel to cancel.



The layers are merged relative to the first (base) layer.