FIGURE 3.

Lesions from 2 patients exhibiting different ¹⁸F-FGln pharmacokinetics despite having very similar SUV corrected by body weight (SUV_bw) as measured at 190 min after injection. In both cases, axial view of last dynamic PET frame (5-min acquisition time, 25–30 min after injection) and last imaging frame (∼190 min after injection), fused with corresponding CT, is displayed. Gadolinium-enhanced T1-weighted MRI is included for comparison. Three time–activity curves are shown: for whole lesion; image-derived input function scaled by whole-blood activity concentration as measured from blood samples, patient-specific plasma fraction, and population-based metabolite fraction; and normal brain tissue. Contributions to total PET signal for tumor time–activity curves are shown for first compartment (C₁) and second compartment (C₂). (A) 52-y-old woman with confirmed diagnosis of astrocytoma. ¹⁸F-FGln PET/CT shows 2 cm³ lesion in right frontotemporal region. Mean intratumor K₁, k₂, k₃, k₄, and V_T were 0.28 mL/min/g, 0.08 min⁻¹, 0.002 min⁻¹, 0.001 min⁻¹, and 3.9 mL/cm³, respectively. Corresponding values for normal brain tissue were 0.02 mL/min/g, 0.09 min⁻¹, 0.001 min⁻¹, 0.001 min⁻¹, and 0.5 mL/cm³, respectively. SUV_bw at 30, 90, and 190 min was 4.0, 3.1, and 2.1, respectively. At these 3 time points, signal from second compartment contributed 3%, 14%, and 32% of total PET activity concentration. (B) 70-y-old woman with confirmed diagnosis of non–small cell lung cancer that metastasized to brain. PET image shows metastatic lesion in right parietal region. Mean intratumor K₁, k₂, k₃, k₄, and V_T were 0.13 mL/min/g, 0.13 min⁻¹, 0.09 min⁻¹, 0.02 min⁻¹, and 5.1 mL/cm³, respectively. Corresponding values for normal brain tissue were 0.01 mL/min/g, 0.05 min⁻¹, 0.04 min⁻¹, 0.004 min⁻¹, and 0.7 mL/cm³, respectively. SUV_bw at 30, 90, and 190 min was 1.9, 3.1, and 2.1, respectively. At these 3 time points, signal from second compartment contributed 66%, 82%, and 83%, respectively, of total PET activity concentration.