FIGURE 1.

Example of absorbed dose and total lesion glycolysis (TLG) calculation. (A) Threshold-based mask on baseline ¹⁸F-FDG PET to delineate 3 lesions and determine baseline TLG; lesion 3 had volume < 5 cm³ and was excluded. (B) VOIs registered to posttreatment ⁹⁰Y PET/CT to determine individual tumor-absorbed dose. Dose distribution was more heterogeneous in lesion 1. (C) TLG measurement on 3-mo follow-up ¹⁸F-FDG PET. Lesion 2 had decrease in metabolic activity of 96% (PR), whereas lesion 1 had only 53% decrease (PR). (D) Healthy liver–absorbed dose as measured on posttreatment ⁹⁰Y PET/CT. Liver contour was manually delineated; this VOI was subsequently expanded by 10 mm in all directions to include all hepatic activity. Healthy liver VOI was achieved by subtracting all lesion VOIs.