This study directly compares standard CT scanning with PET/CT scanning with gating (computer adjusted for breathing excursions) in patients with advanced EOC. The primary objective of this study is to obtain definitive evidence on the value of gated PET/CT compared to current standard imaging (CT scan) for the diagnosis of extra-abdominal and thoracic involvement. This study will give precise estimates on the sensitivity and specificity of CT compared with gated PET/CT, and allow calculation of the positive predictive value and negative predictive value. The proportion of patients upstaged to Stage IV (extra-abdominal involvement) from Stage III by gated PET/CT will be calculated.