title: Increased 18F-FDG uptake in the posterior ocular bulb is associated with brain metastasis: a retrospective study.
abstract: OBJECTIVE
  An observation of increased (18)F-FDG uptake in the posterior ocular bulb led us to the hypothesis that increased posterior ocular bulb uptake is likely abnormal and may indicate intracranial lesions.
  
  
  METHODS
  Fifteen healthy volunteers and 35 patients with lung carcinoma-14 without brain metastasis and 21 with brain metastases-were retrospectively studied. The individuals underwent whole-body PET/CT including the brain with low-dose and unenhanced CT. Two nuclear medicine physicians visually analyzed the posterior ocular bulb uptake of both eyes. Standardized uptake values (SUVs) in the posterior ocular bulb were compared among the study groups. A radiologist reviewed brain MRI scans for abnormalities in the ocular bulbs and orbits.
  
  
  RESULTS
  Visual interpretation showed normal FDG uptake at the posterior ocular bulb in 14 of the 15 healthy volunteers and 12 of the 14 (86%) patients without brain metastasis. Seventeen of the 21 (81%) patients with brain metastases showed increased uptake in the posterior ocular bulb. Visual interpretation showed no statistically significant difference between the healthy volunteers and patients without brain metastasis (p = 0.671). However, there was a significant difference between the patients with brain metastases and healthy volunteers as well as patients without brain metastasis (both, p < 0.001). High interrater agreement (kappa = 0.83) was noted. Brain MRI showed no abnormalities at the posterior ocular bulb in all study subjects. SUV results were inaccurate because of the intense tracer activity in the posterior orbit nearby. A good correlation between visually increased posterior ocular bulb uptake and the presence of brain metastasis was present (Cramer's V = 0.61).
  
  
  CONCLUSIONS
  Visually increased FDG uptake along the posterior ocular bulb is an abnormal finding and may indicate intracranial structural abnormalities such as brain metastases.
authors.affiliation: Department of Radiology, Division of Nuclear Medicine, St. Louis University Hospital, 3635 Vista Ave. at S Grand Blvd., St. Louis, MO 63110, USA. nguyenn@slu.edu
authors.forename: Nghi C
authors.initials: NC
authors.lastname: Nguyen
authors.forename: E Isin
authors.initials: EI
authors.lastname: Akduman
authors.forename: Mohamed H
authors.initials: MH
authors.lastname: Sayed
authors.forename: Dana
authors.initials: D
authors.lastname: Oliver
authors.forename: Medhat M
authors.initials: MM
authors.lastname: Osman
mesh_terms: D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000556:secondary*; D005134:Eye Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000556:secondary*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18