Interest of Early Dynamic Analysis of [18F]-FDG PET Images in the Differential Diagnosis Between Recurrence and Radionecrosis in Brain Metastases.

Various treatment options are available for brain metastases, depending on factors such as lesion site or number lesions. Radiotherapy is a commonly used treatment. Following stereotactic radiotherapy for brain metastases, a potential complication, namely brain radionecrosis, can occur subsequently. It is essential to differentiate between this radionecrosis and lesion recurrence in order to determine the appropriate treatment approach. Contrast-enhanced magnetic resonance imaging (MRI) is the most widely used technique for monitoring brain metastases. Therefore, patients undergo routine MRI at 3 months and during subsequent follow-ups, but if the lesion evolve and if distinguishing between recurrence and radionecrosis is challenging, an [18F]-FDG PET scan is then prescribed by oncologists or radiotherapists during follow-up consultations. As part of the standard patient management protocol, a 10-minute image acquisition begins after a 45-60 minutes wait following the radiotracer injection. A second image acquisition is then conducted 3-4 hours later. For both acquisitions, a low-dose X-ray scanner is synchronously coupled to allow attenuation correction of the PET images.

Patient for whom a [18F]-FDG PET cerebral examination has been prescribed as part of the usual management of brain metastases will be eligible to the protocol. If the patient agrees to participate, an early imaging session is initiated immediately upon radiotracer injection, lasting 15 minutes in addition to the standard acquisition protocol.