Clinically Significant Incidental Findings on the Unenhanced CT Portion of Pediatric FDG PET/CT Studies: Frequency in 410 cases.

Objectives In FDG PET/CT, the unenhanced CT portion, performed for attenuation correction and lesion localization, provides additional independent diagnostic information not apparent on PET alone. The objective of this study was to evaluate the incremental added value and frequency of potentially clinically significant incidental findings from the unenhanced CT portion of PET/CT studies in the pediatric population

Methods From 2000 to 2015 at a single institution, 22,133 PET/CT exams were obtained. Of those exams, 410 pediatric cases were referred for clinical evaluation of known or suspected cancer. Unenhanced CT studies were retrospectively read without knowledge of findings from the PET portion of the PET/CT study. Findings from the unenhanced CT were considered clinically significant if they were not detected or explained by PET findings and were considered, after examination of all available clinical data, to require additional work-up. Most of these findings were worth mentioning in the impression of the report and few cases needed immediate action to alert the ordering physician

Results Unenhanced CT revealed incidental findings in 77/410 cases (18.3%) that were non-FDG avid. Of the 77 cases, 41(53%) were considered clinically significant and required further workup. Furthermore, of those 41 cases, 17(41%) required an immediate call to alert the ordering physician. Examples of such cases include 7 with undescended testicles, 6 with a moderate pleural effusion, 1 with bowel obstruction, 1 with moderate pneumothorax, 1 with moderate ascites and 1 with pectus excavatum

Conclusions Clinically significant findings from the unenhanced CT portion of the PET/CT in the pediatric population are relatively frequent (18.3%). When present, such findings could be serious enough to warrant major alterations in clinical management in at least 17/410 (4%). Thus, we believe careful evaluation of the CT portion of the study needs to be interpreted with special attention to the lesions that PET alone can fail to detect