Imaging Colitis Inflammation with PET-CT

PET-CT scanning was performed 48 h after colitis induction in selected experiments as described previously (24 (link)) with minor modifications. Briefly, fasted (for 6 h) mice were anesthetized with isoflurane and received 200 µCi [¹⁸F]FDG by intraperitoneal (i.p.) injection. One hour later, these mice received 200 µl MD-Gastroview (Mallinckrodt Inc., MO) rectally via a 3.5 French (F) catheter immediately before scan initiation. Computed tomography (CT) scanning was performed for 10 min followed by PET scanning for 20 min using the Inveon PET-CT multimodality system (Siemens). Mice were kept sedated during the scanning process by constant isoflurane inhalation. The images were recorded, and FDG standardized uptake values (SUVs) were analyzed blindly using Inveon Research Workplace software. The MD-Gastroview appears as radiopaque in the CT image, thus highlighting the colon clearly. A region of interest (ROI) comprising the colon was extracted from the CT scan and transferred to the space of the PET scan. Tissues/organs (such as the bladder) other than the colon were excluded from the measurements, and the averages of SUVs of the remaining voxels were calculated to represent the severity of the inflammation.