Lesions blurred by respiratory motion are common in fluorine-18 PET/CT studies. To avoid these artefacts, several standard gating correction technics are available. the investigator aimed to compare the impact of different gating techniques based on phase, amplitude, elastic-motion monitored with and without pressurre sensor device on standardized uptake value (SUVmax and SUVpeak) and uptake volume (UV) measurements on different sizes of pulmonary and liver lesions. The feasability of this study will be done using anthropomorphic coupled with a motion phantom and on a series of patients.

PET-CT images will be acquired on a Biograph Vision600 PET/CT, fitted with 26cm axial field of view and time of flight.

Phantom study will use an anthropomorphic TORSO phantom with a programmable motion phantom, mimicking respiratory motion (QUASAR). Spheres with various internal diameters will be introduce into the lungs (air density) adding an axial mechanical device simulating breathing movement of +/-20mm. Concentration in the spheres will be the same for all diameters. The background and liver activities will be approximatively respectively 38 and 14 MBq. This phantom will be a simulating patient only for lung lesions.

The investigator will compare 6 different PET acquisitions: standard 3min acquisition without movement as our reference of "trues SUVmax and UV", 3min acquisition with simulated breathing movement without any gating and 3min with respectively gating techniques based on phase, amplitude, elastic-motion monitored with and without pressurre sensor device.

Patient study will be on 50 consecutive patients with lung or liver nodules. 18F-FDG injection will be around 2.5 MBq/kg.

The investigator will compare 5 different PET acquisitions: standard acquisition with free respiratory movement as our reference of "trues SUVmax and UV", acquisitions with respectively gating techniques based on phase, amplitude, elastic-motion monitored with and without pressurre sensor device.

Inclusion Criteria:

• presence at least of one hepatic or lung nodule

Exclusion Criteria:

• none

Patients with lung or liver nodules