This pilot study investigates whether advanced diffusion-weighted MRI (ADW-MRI) can differentiate between true tumor progression (TP) and a pseudoprogression (PsP) in patients with glioblastoma (GBM) or brain metastases.

Advanced diffusion-weighted MRI (ADW-MRI) offer the opportunity of higher sensitivity towards subtle tissue changes associated with increased specificity relating to damage of different tissue components of the central nervous system (CNS). Within the framework of this study, conventional follow up MRI will be complemented by ADW-MRI in case of suspected tumor recurrence and possible surgical resection of the suspicious tissue. In the case of surgical resection, the histopathological findings will be correlated to the findings of the ADW-MRI. In the depicted pilot phase, the feasibility of the described protocol will be examined and the data concerning correlations between standard histopathologic and genetic workup of the resected tissue and the results concerning tissue features from ADW-MRI will be analyzed.

Inclusion Criteria:

• Patients with histopathologically proven glioblastoma or brain metastasis and suspected tumor progress on standard MRI after first line therapy and who are candidates for elective surgical resection.
• Able to give informed consent

Exclusion Criteria:

• Contraindications to MRI (e.g. claustrophobia, pacemaker or other implants without MRI-approval, pregnancy)
• Patients in a life-threatening condition
• Patients in need of emergent surgery
• Histopathological analyses of insufficient quality
• Unable to give informed consent
• Age <18 Years