A. There is subtle low density in the left occipital lobe and compression of the occipital horn of the left lateral ventricle.
B, C. There is focal FDG uptake in the left occipital lobe (SUV_max 9.6), surrounded by a large area of decreased FDG uptake extending to the cortex. There is asymmetry between the occipital lobes.

Cerebral metastases.

As normal cortical brain activity is high, and most cerebral metastases occur at the grey-white matter junction, the sensitivity of PET for cerebral metastases remains low, at approximately 50%. The presence of cerebral metastases may be indicated by focal areas of increased FDG uptake, or alternatively by focal areas of decreased FDG uptake, reflecting perilesional vasogenic oedema, as occurred in this case. One group has also shown that cerebral metastases may be indicated by the presence of abnormal increased FDG uptake along the posterior ocular globe, the pathogenesis of which is uncertain.