Fig. 2From: Voxel-based identification of local recurrence sub-regions from pre-treatment PET/CT for locally advanced head and neck cancersIntra-individual differences that can be found in CT images acquired at different time points. Left: pre-treatment CT. Right: post-treatment CT. a Red arrow: changes of patient anatomy after the treatment. Blue arrow: intensity differences due to the injection of a contrast agent in the post-treatment CT (right). b Differences in the position of the patient between pre- and post-treatment CT. Here, the inclination of the head has changedBack to article page