Conventional CT (left column), perfusion CT (middle column), and FDG-PET (right column) images of patients with (a) active lymphoma, (b) inactive lymphoma, and (c) colorectal liver metastases. Arrows indicate the tumour masses. Active lymphoma demonstrated high blood flow and high FDG uptake, inactive lymphoma, low blood flow and low FDG uptake, whilst the colorectal liver metastasis demonstrates low blood flow and high glucose metabolism.