Contrast-enhanced magnetic resonance imaging is the most widely used examination for detecting the presence of brain metastasis. Functional sequences such as perfusion weighted imaging makes it possible to differentiate tumor recurrence from cerebral radionecrosis. However, this imaging technique may exhibit limitations, especially for brain lesions consisting of a mixture of necrotic tissue and tumor progression or depending on the location of the lesion in the brain. The use of 18F-DOPA PET is another option available to oncologists. Many studies on gliomas showed the superiority of this imaging technique over contrast-enhanced MRI. However, this imaging solution has been very poorly studied for brain metastases. The new PET technology equiped with silicon detectors makes it possible to obtain greater sensitivities than those of previous generations. It also make possible to obtain images in very short acquisition times. After injection, the hardware allows to obtain the perfusion kinetics of the lesion thanks to a very short temporal sampling (i.e. three seconds).

The main objective of this pilot study is to evaluate the association between early activity measurements (< 4 minutes post-injection) of 18F-FDOPA in PET and the differential diagnosis between radionecrosis and recurrence of cerebral metastases treated by radiotherapy.

Inclusion Criteria:

• Patient referred for cerebral 18F-FDOPA PET examination prescribed as part of his usual medical care for brain metastasis
• Age ≥ 18 years old
• Affiliation to a social security program
• Ability of the subject to understand and express opposition

Exclusion Criteria:

• Age under 18
• Person under guardianship or curators
• Pregnant woman