The VOI toolbar
supports operations related to the entire VOI definition. Note that all the contours are affected, not just the ones in the visible slice images.
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VOI Action. If this button is selected, a VOI can be selected and then moved or scaled as described below. |
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Clear. Clears all ROIs and contours of the selected VOI, leaving empty definitions. |
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Copy. Copies the VOI to the buffer. |
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Paste. Pastes the VOI from the buffer into the current VOI (which must be empty). |
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Mirror. Opens a sub-menu for mirroring the selected VOI relative to the image center in the three directions. The clone variants first create a VOI copy, which is then mirrored. |
The down arrow button allows to select a variety of further tools.
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Propagate and Apply option buttons. Propagation for VOIs means copying a VOI from one time frame to another. This function is only available for dynamic series and VOIs which have the property set to dynamic. The different propagation variants are described below. |
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Center VOI to Min. Positions the center of the VOI bounding box at the pixel within the current VOI which has the minimal value. Note that multiple activations of the button may result in different positions. |
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Center VOI to Max. Positions the center of the VOI bounding box at the pixel within the current VOI which has the maximal value. This function can be applied during a PERCIST evaluation to center the spheres at the lesion maxima. |
VOI Action
With the VOI Action mode all contours of a VOI can be modified at the same time. In most cases it will be advisable to use the orthogonal layout as illustrated below. After selecting the VOI by clicking at its contour or the entry in the VOIs list, several elements are shown in the overlay: the bounding box of the contours in the active slice, the bounding box of the VOI (maximum of the contour bounding boxes in all slices), and a handle for moving and rotating.
To move the VOI, drag the handle in the center with the left mouse button. Use the small rectangle for a rotation. To scale the VOI, drag the bounding box lines. After releasing the result will be updated in the other views. Note that not all operations are available in all directions:
▪Scaling is only supported within the primary plane which was used for the contour definition. The reason for this behavior is the lack of contour interpolation across slices.
▪Rotation is also only supported within the primary plane.
▪Moving is supported in all directions. While it is arbitrary within the primary plane, shifts in the orthogonal direction (across the slices) are only possible in increments of the slice thickness.
Referring to the example above, the frontal VOI can only be scaled in the L/R and A/P directions, but not in the H/F direction. In the sagittal plane, there is no rotation handle, and the scaling is only active for the bounding box lines indicated in the illustration below (A/P).
VOI Propagation
The VOI Propagate multi-function button serves for propagation over time and is therefore only active if
▪the study is dynamic,
▪and the properties of the VOI have been set to dynamic (
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In this case, the VOI can consists of a differing definition at the different times. The button has the following options:
VOI Propagate - |
Copies the current VOI, goes to the prior acquisition of the dynamic series, paste the VOI. |
VOI Propagate + |
Copies the current VOI, goes to the following acquisition of the dynamic series, and paste the VOI. |
VOI ApplyToAll |
Copies the current VOI and pastes it into all acquisitions. |
VOI SmartApply |
Copies the current VOI and pastes it into all subsequent acquisitions until an acquisition is encountered which already contains a VOI definition. |
4D VOI Operations
When working with dynamic VOIs in dynamic series, an additional dimension needs to be considered, the time. Therefore, an area is available with similar tools as described above for the ROIs and VOIs. It is located on the Tools pane and allows a dynamic VOI to be cleared, copied, pasted, and mirrored in all frames at once. The load button allows inserting a static VOI in the currently selected frame.
