Prognostic Value of Intratumor Metabolic Heterogeneity Parameters on ¹⁸F-FDG PET/CT for Patients with Colorectal Cancer

Figure 2

Process of measuring metabolic heterogeneity indices on ¹⁸F-FDG PET/CT. Fused PET/CT image showing an ¹⁸F-FDG avid tumor in the colon. A circle (pink) was drawn to include the whole tumor, and an isocontour volume of interest (VOI; pink) was automatically generated by using a 40% SUVmax cutoff (a). Heterogeneity index-1 was defined as the coefficient of variance, which was calculated as the SD of the SUV divided by SUVmean. Metabolic tumor volume (MTV) was assessed according to three thresholds (SUV 2.5, 3.0, and 3.5, resp.), and linear regression analysis was performed to find the slope. Heterogeneity index-2 was the negative form of the slope (b).

(a)

(b)