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FIGURE 3. Imaging studies performed before and during course of treatment for patient with rectal cancer. (Upper row) Images from CT performed in prone position before chemoradiotherapy (RT), during chemoradiotherapy, and at time of surgery. (Middle row) Images from MRI performed in supine position before chemoradiotherapy, during chemoradiotherapy, and at time of surgery. (Lower row) Images from 18F-FDG PET performed before chemoradiotherapy, during chemoradiotherapy, and at time of surgery. Tumor (red arrows) shows high level of uptake of 18F-FDG before start of treatment; 18F-FDG signal decreases during treatment and is lowest at time of surgery. 18F-FDG PET can help in delineating GTV before treatment and in replanning radiation treatment during course of treatment. White arrows indicate urinary bladder.
