Prospective, monocentric study aiming to evaluate the PET-CT (Positron Emission Tomography - Computed Tomography) scanner performances to detect infra-centimetric lesions in two groups of patients with cancer and of different BMI (Body Mass Index) classes (BMI ≤ 25 and BMI > 25).

For each patient, two consecutive PET-CT scanner will be performed using the "Discovery MI" and "Discovery IQ" PET-CT scanner systems.

Virtual lesions will then be created on images obtained. Images will be interpreted by two independent observers.

The study participation of each patient will be a maximum of 24 hours.

Inclusion Criteria:

1. Age ≥ 18 years old.
2. A patient with a cancer for which a FDG-PET (fluorodeoxyglucose-positron emission tomography) must be performed according to the standard practices
3. OMS ≤ 1, Karnofsky Index > 70.
4. Negative pregnancy test at inclusion.
5. Patient able to maintain a lying position in a strict supine position twice.
6. Patient affiliated to a Social Health Insurance in France.
7. Patient who has signed informed consent prior inclusion in the study and before any specific procedures for the study.

Exclusion Criteria:

1. Patient with unbalanced diabetic
2. Patient with a formal contraindication usual for certain imaging procedures (severe claustrophobia, wearing a heart valve, pacemaker, etc.)
3. Pregnant or breastfeeding woman
4. Any psychological, family, geographical or sociological condition that does not allow medical follow-up and/or procedures provided for in the study protocol to be respected
5. Patient protected by law