Inflammation and Infection: Imaging Properties of ¹⁸F-FDG–Labeled White Blood Cells Versus ¹⁸F-FDG

(A) Time course retention of ¹⁸F-FDG in WBCs incubated in 0.9% NaCl for extended periods at 37°C. Percentage cell-bound activity (labeling) is expressed as pellet activity/total activity ratio. (B) TLRC at 90 min after WBC labeling. Dotted lines indicate retention factor, R_f = 0 (left) and R_f = 1 (right). Center panel: ¹⁸F-FDG (R_f = 0.37) contains trace of ¹⁸F-fluoride not migrating with the mobile phase. Right panel: Lysed ¹⁸F-FDG–WBCs (similarly as ¹⁸F-fluoride, ¹⁸F-FDG-6P used as standard does not migrate with the mobile phase).

(A) Tissue biodistribution of ¹⁸F-FDG–WBCs and ¹⁸F-FDG in turpentine model 1 h after radiotracer injection. Values are expressed as % DPG (mean ± SE). (B) Coronal images of turpentine model obtained 1 h after radiotracer injection. Arrow indicates inflammation site (animals positioned prone on imaging table). (C) Microscopic images of Giemsa-stained sterile inflamed muscle sample, collected 1 h after radiotracer injection. Abscess is characterized by central necrosis (N) and a surrounding wall (W) mainly consisting of granulocytic cells and normal muscle tissue (MT). (D) Phosphorimaging of frozen section from turpentine-injected muscle (IM) and normal muscle (NM), collected 1 h after radiotracer injection. Standard: ¹⁴C standard activity values were converted to ¹⁸F activity in MBq/g by using a calibration curve. Control: NM ¹⁸F-FDG–WBC, tissue uptake = 0.22 kBq/g. ¹⁸F-FDG–WBC: IM ¹⁸F-FDG–WBC, tissue uptake = 8.14 kBq/g. ¹⁸F-FDG: IM ¹⁸F-FDG, tissue uptake = 3.07 kBq/g. DPG = (injected dose/gram of tissue) × 100; GI = gastrointestinal; Inf. = infected; Uninf. = uninfected.

(A) Tissue biodistribution of ¹⁸F-FDG–WBCs and ¹⁸F-FDG in E. coli model 1 h after radiotracer injection. Values are expressed as % DPG (mean ± SE). (B) Coronal images of E. coli model obtained 1 h after radiotracer injection. Arrow indicates infection site (animals positioned prone on imaging table). (C) Microscopic images of Giemsa-stained E. coli-injected septic muscle sample, collected 1 h after radiotracer injection. Necrosis (N) and abscess architecture showed a different organization compared with the sterile model. Numerous inflammatory cells were present in surrounding wall (W) infiltrating muscle tissue (MT). E. coli can be seen in the higher magnification. (D) Phosphorimaging of frozen section from E. coli-infected muscle (IM) and normal muscle (NM), collected 1 h after radiotracer injection. Standard: ¹⁴C standard activity values were converted to ¹⁸F activity in MBq/g by using a calibration curve. Control: NM ¹⁸F-FDG–WBC, tissue uptake = 0.1 kBq/g. ¹⁸F-FDG–WBC: IM ¹⁸F-FDG–WBC, tissue uptake = 2.035 kBq/g. ¹⁸F-FDG: IM ¹⁸F-FDG, tissue uptake = 0.99 kBq/g. DPG = (injected dose/gram of tissue) × 100; GI = gastrointestinal; Inf. = infected; Uninf. = uninfected.