Bowel Hot Spots at PET-CT

Abstract

Positron emission tomography (PET) with 2-[fluorine-18]fluoro-2-deoxy-d-glucose (FDG) has been shown to be sensitive in the detection of many bowel malignancies, but its specificity is lower because of various physiologic and pathologic patterns of bowel FDG uptake. PET-computed tomography (CT) can be useful in localizing and characterizing foci of increased FDG uptake within the bowel. As the use of PET-CT in the staging and monitoring of oncologic disease continues to expand, familiarity with these patterns of bowel FDG uptake is essential and can help determine the need for and the relative urgency of further testing. Although a variety of imaging protocols are used for PET-CT, the use of negative oral contrast agent allows improved bowel distention while eliminating potential artifacts caused by high-density oral contrast agents. In addition, correlation with the CT portion of the combined PET-CT examination can sometimes help identify the cause of focal or segmental bowel uptake. The radiologist should be aware of potential pitfalls in the evaluation of FDG-avid foci within the abdomen, including bowel motility and low-attenuation lesions mimicking bowel. Nevertheless, even though the precise role of combined PET-CT for bowel assessment has yet to be determined, the application of sound basic principles of image interpretation will help ensure the accurate interpretation of bowel findings seen with this combined modality.

Colonography by CT, MRI and PET/CT combined with conventional colonoscopy in colorectal cancer screening and staging

“…It is confirmed that PET activity correlated well with active inflammation in both UC and CD, suggesting that this may be a noninvasive method of identifying disease activity in patients with IBD [66] . Neurath et al suggested that FDG-PET appear to be a reliable noninvasive tool for simultaneous detection of inflamed areas in the small and large bowel of patients with CD and can be used to detect disease activity in the terminal ileum and colon of CD patients with high sensitivity and specificity [67] .…”

PET/CT Enterography in Crohn Disease: Correlation of Disease Activity on CT Enterography with 18F-FDG Uptake

“…CT enterography usually uses negative oral contrast material that causes bowel distention without increasing CT attenuation and helps avoid the potential PET attenuation artifacts that can be seen with high-density barium-or iodinebased oral contrast material. Also, the bowel distension obtained by CT enterography reduces background 18 F-FDG activity and physiologic uptake of 18 F-FDG in the bowel, allowing better definition of uptake in the bowel wall (14)(15)(16).…”

The Role of Positron Emission Tomography in Inflammatory Bowel Disease

“…This method permits to obtain a distension of the bowel and an optimal evaluation of the wall thickening. There are also some negative oral contrast media commercially available (7)(8)(9)(10).…”