The Sphere with Max Average (Peak VOI) function creates a sphere object VOI of defined volume and places it in the bounding VOI such that the average is maximal. Beyond specification of the Sphere volume (default: 1ccm = PERCIST peak), the appearing dialog window offers additional options.
With Activity in entire peak VOI, the average calculation uses all the voxels intersecting the sphere. With Activity in intersection of parent and peak VOI, the average calculation is performed using only the voxels intersecting both parent and peak VOI. The average calculation always uses the fraction mode which weighs the voxel value by the included fraction (see Inclusion Criteria for Pixels).
With Background threshold enabled, the algorithm only considers spheres centered a voxels with value above the threshold. With Minimal Peak VOI inclusion [%] enabled, only spheres with sufficient overlap with the bounding VOI will be considered.
The resulting sphere object is called Peak[enclosing-name].