the aim of this study is to measure brain metabolism in patients with lung cancer.FDG uptake in the brain in patients with malignant tumors will be compared to the amount of tracer activity found in patients who have benign pulmonary process. if differences between the brain uptake of FDG in the two groups will be found, further assessment will be performed in order to evaluate if such differences could be attributed and specifically localized to the brain regions innervated by the vagus