PET/CT > Artifacts & Pitfalls > Barium

Intraluminal Barium

68 year old male with large B-cell lymphoma, status post six cycles of chemotherapy. PET/CT ordered for restaging.

Patient had had an upper GI barium examination one week prior to PET/CT to evaluate for nausea and vomiting. Evaluation of the abdomen and pelvis is limited by artifact created by retained barium within the colon. Careful evaluation of the non-attenuation-corrected and attenuation-corrected data sets as well as the CT data demonstrates no definite evidence for a gross abnormality in the abdomen or pelvis.

Recently ingested dense oral barium solutions such as those used in upper GI and barium enema examinations create artifacts related to attenuation correction similar to those discussed earlier for metallic hardware. During the attenuation correction process, "overcorrection" will occur with the PET computer essentially "adding in" activity to the bowel containing the barium. As described with metallic hardware, this could also create the appearance of increased activity in tissues closely approximated to the barium-filled bowel loops. Again, inspection of the non-attenuation corrected images will often reveal whether or not there is truly any abnormal activity in the tissues located immediately adjacent to the barium-filled bowel.

The non-attenuation-corrected data shown in the bottom row confirms that there is actually no increased activity in the region of the colon, as was apparent on the attenuation-corrected data shown in the top row. The attenuation correction process resulted in artifactually increased activity related to highly concentrated metallic density barium within the lumen of the colon.

The general thinking is that oral contrast agents with densities less than 400-500 Hounsfield units (HU) such as those used for routine CT imaging should not produce any significant attenuation-correction related artifact (unless they have become inspissated and concentrated in the bowel in which case their HU would be increased above these values).