PET-MRI scanning regarding amino acid metabolic profile, functional and morphological details will be performed on set intervals to patients with brain tumor & brain metastases in order to try to optimize the study protocol, distinguish between pseudo-response to anti-angiogenic therapy and tumor progression, and most importantly try to distinguish between progressive tumor and treatment related effects.3 cohort of patients will be included in the study.

The multimodality approach for management of primary and secondary brain tumors includes surgery, radiotherapy and chemotherapy. Determination of an objective response to treatment relies on imaging findings (e.g. CT, MRI, PET).During the course of the disease patients with brain tumors often develop new or worsening contrast-enhancing lesions on routine follow-up imaging.These lesions may reflect tumor recurrence, treatment effect, or a combination of both. Discerning between tumor recurrence and treatment effect is clinically significant issue and a major challenge in neuro-oncology. Treatment-related effects exist within a spectrum, with "pseudoprogression" reflecting subacute and often transient injury, and "radiation necrosis" reflecting later and more permanent damage.The difficulty in differentiating tumor progression from treatment-related effects has serious implications for individual patient treatment decisions and prognosis as well as for clinical trial design and interpretation of results.

A contemporary hybrid scanner technology is capable of acquiring both metabolic information from PET and morphological and functional details from MRI. This new integrated technique opens new horizons for clinical and research evaluation of brain tumors and the associated treatment effects.

The aim of the current study is to use the combined data obtained by PET-MRI scanning regarding amino acid metabolic profile, functional and morphological details in order to:

1. Distinguish between progressive tumor and treatment related effects
2. To identify pseudo-response to antiangiogenic therapy from tumor progression
3. To optimize the study protocol of PET-MRI for future routine clinical application.

The study will include three cohorts of patients with brain tumors:

1. Primary brain tumors:

   A cohort of 60 adult patients (age: 18-70) with newly diagnosed high grade gliomas (Glioblastoma, Anaplastic Astrocytoma, Anaplastic Oligodendroglioma, Anaplastic Oligoastrocytoma) scheduled for a combined treatment with chemotherapy and radiotherapy. Patients will be eligible for the study immediately after receiving the pathological diagnosis and prior to any further treatment. These patients will undergo the PET-MRI scanning at 4 time points as follows:

   • 1st scan: after surgery or biopsy and before any further treatment
   • 2nd scan: will be performed up to 4 weeks after completing the combined radiotherapy and chemotherapy regimen.
   • 3rd and 4th scans: will follow with interval of 3 months between studies.
   • Additional scans will be performed by the decision of the investigators or when the patient is scheduled for antiangiogenic therapy

2. Brain metastases treated with stereotactic radiosurgery (SRS):

   A cohort of 60 adult patients (age: 18-75) who are being followed after SRS treatment for brain metastases secondary to breast or lung cancer whose recent imaging showed signs of progression in at list one of the previously treated lesion. Progression will be determined by Response Assessment in Neuro-Oncology Criteria (RANO criteria) for brain metastases. Number of target lesions should not exceed 4 with size of lesions ranging between 5-40 mm. These patients will undergo the PET-MRI scanning at three time points as follows:

   • 1st scan: Following determination of progression of SRS treated lesion based on standard surveillance MRI
   • 2nd and 3rd scans: will be performed every 2 months after the first scan
   • Additional scans will be performed by the decision of the investigators

3. Brain metastases not treated with SRS/radiotherapy

A cohort of 20 adult patients (age: 18-75) with a diagnosis of brain metastases secondary to human epidermal growth factor receptor 2 (HER2) positive breast cancer or anaplastic lymphoma kinase (ALK) or Epidermal Growth Factor Receptor (EGFR) gene mutant lung cancer who might be candidate for SRS treatment and in whom targeted therapy is selected instead. The size of the lesions should range between 5-40 mm. These patients will undergo the PET-MRI scanning at three time points as follows:

• 1st scan: after the first documentation of brain metastases on standard MRI
• 2nd and 3rd scans: will be performed every 2 months after the first scan
• In case of progression and SRS treatment follow-up scanning will be performed every 2 months
• Additional scans will be performed by the decision of the investigators

Inclusion Criteria:

• Subject with glial brain tumors,
• Subjects with metastatic brain tumors that were treated with stereotactic radiation (SRS), * Subjects with metastatic brain tumors which were not treated

Exclusion Criteria:

• glial tumor with no histological diagnosis
• non breast of lung metastasis
• non compliance
• unable to lay still during the scanning
• mri non
• renal failure/gadolinium sensitivity
• less than 5 mm metastatic tumors
• bleeding brain tumors
• pregnancy