Inclusion Criteria:

- neuroradiologically suspected Glioblastoma multiforme

- histological verification will be obtained either by microsurgery or by stereotactic
biopsy. The neuropathological diagnosis will be verified by a reference
neuropathologist

- patients will undergo radiochemotherapy subsequent to surgical procedure

- patients older than 18 years

- Karnofsky Performance Score >=70

- pregnant or nursing female patients will not be included in this study

- safe contraceptive methods during the radiochemotherapy and chemotherapy

Exclusion Criteria:

- patients in whom informed consent cannot be obtained due to organic brain syndrome or
insufficient language skills

- patients who cannot lie quiet for a time period of app. two hours during the FET-PEt
scan

- medical history of a metastatic brain disease

- patients in whom an MRI scan cannot be performed due to claustrophobia metallic
protheses or pacemakers etc.