Detection of intestinal NET by (68)Ga-DOTATOC PET/multiphase CT

Objectives Interpretation of small intestinal NET lesions by Ga-68-DOTATOC PET can be difficult by using non-contrast CT only. The potential impact of multiphase CT for the detection of intestinal NET lesions was evaluated.

Methods Out of 313 consecutive (68)Ga-DOTATOC PET/CT for NET examination during the last 4 years 24 patients (11 with CUP, 14 for staging) had NET suspicious findings in the bowel. Arterial and portalvenous phases were performed for the epigastrium only, the venous phase for the whole body. Two experienced radiologists together with a nuclear medicine physician rated the CT findings as suspicious for a malignant lesion, not suspicious, suspicious in combination with PET.

Results 8/24 patients showed multifocal intestinal lesions resulting in 41 suspicious findings overall. 40 findings were detected by PET, 1 only by CT (histology: middle grade NET with Ki67: 5%). 38 findings were judged as intestinal NET lesions based on other diagnostic tools and/or histopathology (available for 11 patients) serving as reference standard. 3 PET findings were false positive. All three had negative arterial and venous CT findings. 13 PET positive NET lesions could be evaluated by both arterial and venous phases. Arterial phase results: suspicious 2, not suspicious 1, suspicious in combination with PET 10. Venous phase results: suspicious 2, not suspicious 13, suspicious in combination with PET 1. 16 PET positive lesions could be evaluated only in the venous phase: suspicious 1, not suspicious 16.

Conclusions The arterial phase of multiphase (68)Ga-DOTATOC PET/CT could ameliorate localisation and help improving the diagnostic reliability of intestinal NET lesions. The venous phase of multiphase (68)Ga-DOTATOC PET/CT however was not helpful for NET detection