[18F-FDG PET/CT in ocular and orbital abnormalities not only neopastic: comparison with traditional imaging]

Orbital and ocular neoplasms are rare tumors that could be benign or malign, primary or metastatic. Abnormalities within the orbit present a challenge in evaluation for imaging, both for morphologic examinations (ME) as weel as computed tomography (CT) and magnetic resonance (MR) and [18F]-2-deoxy-D-glucose Positron emission tomography/computed tomography (18F-FDG PET/CT). The aim of our study was evaluate 18F-FDG PET/CT role in orbital abnormalities, comparing it with CT and MR.

A retrospective analysis of 67 patients (pts) (34 males and 33 females; mean age 59.91 years old) who performed 18F-FDG PET/CT for orbital and ocular abnormalities was performed. Comparison between 18F-FDG PET/CT and ME was performed by Cohen's K also within the most representative hystologic subtypes.

18F-FDG PET/CT resulted positive in 19/67 pts. 47/67 pts performed ME (27/47 performed CT and 20/27 MR) within 20 days before 18F-FDG PET/CT and concordance was very poor (K=0.154). Considering 27/47 pts who performed CT, concordance was very poor (K=0.100). Considering the 20/47 pts who performed MR concordance was poor (K=0.266). Considering 19/47 pts with primary ocular NHL concordance resulted poor (K=0.269). Considering 6/47 pts with primary ocular melanoma concordance resulted very poor (K=0.182). In 9/47 pts with metastases diagnosis, concordance was absent (K=-0.189).

CT and MR are ME that permit the evaluation of the orbital region even with limits related to the difficulties of the region. 18F-FDG PET/CT is a sensitive tecnique for several malignancies. The low concordance among 18F-FDG PET/CT and ME suggests their complementary role, then to associate 18F-FDG PET/CT even for the whole-body evaluation.