Effects of ROI Placement on PET-Based Assessment of Tumor Response to Therapy
Both tumors and normal tissues may shrink and shift during the treatment. The coregistered PET/CT images of Pre-Tx (a) and Intra-Tx (b) are cross-sectional images of a patient with a primary tumour of the tonsil. The patient’s left parotid gland in Intra-Tx (yellow contour) shows volume loss and shift relative to that in Pre-Tx (red contour). Similarly, the gross tumour volume for one nodal disease site in Intra-Tx (dotted green contour) shows volume loss and shift relative to that in Pre-Tx tumour (dotted blue contour).