Frequency and clinical relevance of PET/CT incidentalomas

Rationale and objectives: To assess the frequency of clinically significant incidental CT findings on PET/CT. Materials and methods: Reports of 345 cases of baseline standard skull base to thighs PET/CT exams done over the course of a 6 month period at an outpatient facility affiliated with a large tertiary care level 1 trauma medical center were retrospectively reviewed. Incidental CT findings were assigned a level of clinical significance on a scale of 1-5, from doubtful significance to very significant. CT findings already known from prior CT reports were not included. CT findings corresponding to PET findings were also excluded. A score of 3 or greater was considered significant and reportable. Results: Out of 345 cases, 171 (50%) had a least one CT finding rated at or above a score of 3 on our scale of significance, while 96 (28%) were found to have at least one CT finding with score at or above 4, and 25 cases (7%) showed at least one CT finding rated 5. Conclusion: A substantial percentage of baseline PET/CT studies contain previously undiagnosed, significant incidental findings on the CT images.