Measure the Intensity Average and Standard Deviation in Space

9.10 Measure the Intensity Average and Standard Deviation in Space

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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 VOI Sphere tool is similar to the ROI tools described in section 2.19, but the measurements are performed in the space bounded by a sphere.

9.10.1 Create sphere

To create a sphere:

Select a series to measure, go to the image in which the center of the sphere should be located.
Activate the VOI sphere tool by clicking the button on the toolbar. To continue work with this tool, use the button with which the tool was activated. To learn more about tool control, see Section 1.14.
The VOI sphere can be built in two ways:
- Move the cursor to the point where the center of the sphere should be located. Click mouse button. Choose the desired sphere diameter by moving the mouse. To complete the drawing, click the mouse button.
- Click the mouse button at the point where the center of the sphere should be located and set the desired sphere diameter while holding the mouse button. Release the mouse button to ﬁx the sphere diameter.
To cancel creation, press the Esc button on the keyboard.

The following parameters are displayed near the sphere (Fig. 9.5):

minimum intensity value;
maximum intensity value;
average intensity value;
standard deviation;

The results only for the corresponding series are displayed in the CT and PET windows, the results for both series are displayed in the PET+CT window.

9.10.2 Sphere location in space

All spheres are always displayed in the MIP window. The line of the intersection of the sphere with the image plane and the measurement results are displayed in the other windows. As the distance from the center of the sphere increases, the diameter of this circle decreases. If the sphere does not intersect with the image plane, the measurement results for the sphere are not displayed in this window.

If the center of the sphere is in the current image and the VOI Sphere tool is activated, crosses are displayed in the center of the sphere and on its border.

9.10.3 Actions with the sphere

To edit a sphere:

Go to the image that contains the center of the sphere. To do this, slide the images until the crosses appear in the center and on the border of the sphere.
To move the sphere, move the cursor over the cross in its center and move the mouse holding down any mouse button. When you locate the cursor over the cross it increases.
To change the radius, move the cursor over the cross on the sphere border and move the mouse, holding down any mouse button. When you locate the cursor over the cross it increases.

To move the block with the measurement results, locate the cursor over it and move the mouse, holding down the left mouse button or the button to which this tool is assigned. For this, it is not necessary that the center of the sphere be on the current image.

To remove a sphere move the cursor over the block with the measurement results or on the cross in the center or on the border of the sphere and press the Delete key on the keyboard, or right-click the mouse and select the Remove object command.

9.10.4 Drawing Parameters

To change the drawing parameters:

Locate the cursor over the block with the measurement results or on the cross.
Right-click.
Select the item Tool options... on the context menu.
In the dialog box that appears, set the color by clicking on the color box.
Set the object name, the line thickness and the font size.
To connect the block with the measurement results and the sphere of the dotted line, check the Footnote line box.
To use these settings by default, check the Set as default box.
To apply the settings, click OK. To cancel, click CANCEL.

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