Definition of ROIs used for18F-FDG uptake quantitation in the axillary LN. CT, PET, and fused CT/PET images of the same LN obtained on day 3 (b) and day 8 (a,c) postinoculation of monkeypox virus. (a) SUVmean (i), SUVthreshold (ii), mSUVthreshold (iii), and SUVfixed volume (iv) (see "Methods" for details). (b) An example of inclusion of the voxels (chartreuse) from surrounding tissue with higher SUVs compared to the voxels (black) within the LN when SUVthreshold metrics was applied to PET image. (c) Delineation of a LN center and dimensions for VOIs placement within the LN edges. Images represent a middle slice of a LN in sagittal, transaxial, and coronal views showing the long and a short axis dimensions. The intersection of the two axes identifies a LN center.