n.19 – 18F-FDG PET/CT IN OCULAR AND ORBITAL ABNORMALITIES: COMPARISON WITH TRADITIONAL MORPHOLOGICAL IMAGING



Abstract

BACKGROUND-AIM
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.
METHODS
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. Lesions were localized in orbit (36/67), ocular globe (20/67), lacrimal gland (8/67) and conjuntiva (2/67). 58/67 were primary tumors (30/58 Non Hodgkin Lymphomas (NHL), 13/58 melanomas, 7/58 carcinomas, 8/67 other lesions) and 9/67 metastasis (from NHL in 4/9, breast in 3/9, lung in 1/9 and liver in 1/9). Comparison between 18F-FDG PET/CT and ME was performed by Cohen’s K also within the most representative hystologic subtypes.
RESULTS
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. In 14/47 pts 18F-FDG PET/CT and ME were both positive; in 1/47 18F-FDG PET/CT was positive and ME negative; in 23/47 pts 18F-FDG PET/CT was negative while ME was positive; in 9/47 pts the two techniques were both negative. Concordance was very poor (K=0.154). Considering 27/47 pts who performed CT, in 8/27 pts 18F-FDG PET/CT and CT were both positive; in 16/27 pts 18F-FDG PET/CT was negative while CT positive; in 3/27 pts the two techniques were both negative. Concordance was very poor (K=0.100). Considering the 20/47 pts who performed MR, 18F-FDG PET/CT and MR were both positive in 6/20 pts; in 1/20 pts 18F-FDG PET/CT was positive while MR negative; in 7/20 pts 18F-FDG PET/CT was negative and MR positive; in 6/20 pts both the techniques were negative. Concordance was poor (K=0.266). Considering 19/47 pts with primary ocular NHL, 18F-FDG PET/CT and ME were both positive in 7/19 pts; 18F-FDG PET/CT was negative while ME was positive in 8/19 pts; both techniques were negative in 4/19 pts. Concordance resulted poor (K=0.269). Considering 6/47 pts with primary ocular melanoma, in 1/6 pts 18F-FDG PET/CT and ME were both positive; in 3/6 pts 18F-FDG PET/CT was negative and the ME negative; in 2/6 pts both the techniques were negative. Concordance resulted very poor (K=0.182). In 9/47 pts with metastases diagnosis, 18F-FDG PET/CT and ME were concordant in 1/9 pts; in 1/9 pts 18F-FDG PET/CT was positive while ME was negative; in 6/9 pts 18F-FDG PET/CT was negative while ME was positive; in 1/9 pts the two techniques were negative. Concordance was absent (K=-0.189).
CONCLUSION
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.

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