4DST MIP (A), 4DST axial (B), CT (C), FDG axial (D), and FDG MIP images (E). PET images (axial and maximum-intensity-projection) with 4DST and FDG for lymph node lesions and the primary lung cancer in patient No. 23. The background uptake is clearly lower in 4DST than FDG. 4DST and FDG show intense uptake at the left lower paratracheal lymph node (#4 L) and the left hilar lymph node. 4DST also shows uptake at the lower paratracheal lymph node (arrow), not clearly identified on FDG.