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The Sphere with Max Average (Peak VOI) function creates a sphere object VOI of well-defined volume and centers in such a manner in the selected VOI that the average is maximal. The fraction mode is always used for the pixels classification inside the sphere VOI, independently of the classification mode selected for the VOIs statistics.
The actual Sphere volume can be specified in the interface window.
With the Activity in the whole peak VOI enabled the activity calculation is performed using all the voxels inside the sphere when the center of the sphere is inside of the original VOI. In the voxels which are not fully inside the Peak VOI the average value is estimated using the fraction of the pixel value corresponding to a fraction of the surface area inside the Peak VOI. Note that the algorithm will consider only spheres with the center inside the original VOI.
With the Activity in common part of the parent and peak VOI enabled the activity calculation is performed using only the voxels in the common part of the parent and Peak VOI. For the voxels which are not fully inside the Peak VOI the average value is estimated using the fraction of the pixel value corresponding to a fraction of the surface area inside the Peak VOI. Note that with this option the center of the phere will always be inside the original VOI.
With the Background threshold box enabled, the algorithm compares the voxel value in the center of the Peak VOI with the specified value. The method will consider only the spheres which central values are greater than the specified threshold.
With the Inclusion of the Peak VOI box enabled, the algorithm is checking the overlapping percentage of the Peak VOI with the original VOI. Only the spheres with a percentage overlap value greater than the specified inclusion value will be considered by the algorithm.
The resulting sphere object is called Peak[enclosing-name].
