Fig. 2

Coronal slice extracted from PET volume: (left) original intensity values saved in jpg format, which does not take into account the physical spacing between sample (right) intensity values isotropically resampled and then saved in jpg format. To resample the original intensities onto an isotropic grid, we use the image’s spatial information. The resampled image should occupy the same physical region in space as the original. The code above illustrates that resampling takes this into account by specifying that both images have the same origin and axes direction but different pixel spacings (4.0 × 2.5 vs. 2.5 × 2.5 mm) and consequentially grid sizes (168 × 344 vs. 273 × 344)