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FIGURE 3. Precise characterization of increased 18F-FDG uptake and retrospective lesion detection on CT, after PET/CT. A 35-y-old man, 22 mo after treatment for colon cancer, with negative high-resolution contrast-enhanced CT and normal levels of serum tumor markers, was referred for 18F-FDG PET for further assessment of pelvic pain. (A) Coronal PET images show area of increased 18F-FDG uptake in left pelvic region (arrow), interpreted as equivocal for malignancy, possibly related to inflammatory changes associated with ureteral stent or to physiologic bowel uptake. (B) Hybrid PET/CT axial image (top) precisely localizes uptake to soft-tissue mass adjacent to left ureter, anterior to left iliac vessels. Mass (arrow) was detected only retrospectively on both diagnostic CT and CT component of hybrid imaging study (bottom). Patient received chemotherapy, resulting in pain relief and decrease in size of pelvic mass on follow-up CT.
