Patients with glioblastoma, an aggressive brain tumor, are recommended to undergo treatment with tumor treating fields using the Optune device as part of standard of care therapy. While undergoing treatment, patients are monitored regularly with brain MRI scans to look for tumor progression, but there are currently no means to predict which, or when, patients will progress. The purpose of the current study is to prospectively analyze these MRI scans to look for subtle imaging markers that can predict for future brain tumor progression while undergoing tumor treating field therapy.

The proposed trial involves the prospective collection of imaging data at standard clinical time points before and during treatment with TTFields. All patients who are offered treatment with TTFields will also be offered enrollment in this non-randomized, observational study. Imaging data will include the standard battery of MRI sequences, which includes DWI and ADC reconstruction. These data will be collected at standard time points and the proposed study will not rely on any additional imaging or tests outside of the clinical standard of care.

Inclusion Criteria:

• Patients age 18 or older with newly diagnosed WHO grade IV glioblastoma or patients with recurrent glioblastoma not previously treated with TTFields.
• Patients may have undergone surgical resection or biopsy.
• Residual tumor, absence of treatment with temozolomide or radiation therapy will not be an exclusion criteria for the study.

Exclusion Criteria:

• Patients previously treated with TTFields will not be included in the study.
• Patients will also be excluded if they are undergoing active treatment with systemic agents, including bevacizumab, during treatment with TTFields.

Any patient with newly diagnosed or with recurrent glioblastoma who meet the eligibility criteria of the study.