Can a breath hold PET/CT improve the detection and assessment of metastatic liver lesions?

All patients will undergo the intervention at the end of their standard whole-body PET/CT, thus no additional F18-FDG is required. The intervention in no way affects the diagnostic accuracy of the control and vice versa. The participant will be instructed by the nuclear medicine technician to perform several deep breaths, then a single deep inspiration following a short countdown from 5 seconds. A low dose non contrast CT of the upper abdomen will be performed (50mAs tube voltage, 120kV tube current, 3mm slice thickness, 2mm increments, diaphragm to inferior liver margin approximately 25cm). Once this breath hold CT is complete, the participant will be asked to regain their breath. After 30 seconds, they will be instructed by the nuclear medicine technician to perform several deep breaths, then a single deep inspiration following a short countdown from 5 seconds. Once at full inspiration by visual confirmation, PET data is acquired in a single bed position of the upper abdomen. After 20 seconds as timed using a digital stopwatch by the nuclear medicine technician, the patient will be instructed to breathe normally. If the breath is interrupted during the PET acquisition, a repeat attempt will be performed. If failed a second time, breath hold will be abandoned. Adherence to the intervention is controlled by the study investigators, nuclear medicine technicians and supervising radiologist/nuclear medicine physician. Interrupted breath hold for CT is not repeated, in order to ensure minimal radiation to the patient. Interrupted breath hold for PET will be repeated once only, after this the intervention will be abandoned. Patients are reviewed by a nurse following their standard PET/CT to ensure participant wellness and normal vital observations, which will occur in this study. This is standard care following a PET/CT. No specific additional post-trial provisions are planned.