FOR ARMS 1-3

Inclusion Criteria:

• Age =18 years.
• Patient is able to lie in the PET/CT scanner for at least 60 minutes while undergoing scanning.
• Patient is willing and able to review, understand, and provide written consent for the study procedures and indicates that they are aware of the investigational nature of this study.

Exclusion Criteria:

• Patients who are pregnant or lactating are excluded. Premenopausal women (defined per institutional guidelines) must have a negative pregnancy test (urine or serum) within 7 days of the PET scan.
• Severe increased intracranial pressure, status epilepticus, or other severe or progressing clinical symptoms requiring urgent intervention in the opinion of the treating
• Karnofsky performance score <60, as determined by one of the clinician co- investigators.

ADDITIONAL CRITERIA FOR ARM 1:

Inclusion Criteria:

• Histopathology/cytopathological diagnosis of a glioblastoma without a history of radiation.
• The tumor is deemed amenable for radiation treatment (pre-radiation planning MRI can be done before or after the PET scan).

ADDITIONAL CRITERIA FOR ARM 2:

Inclusion Criteria:

• Previous histopathology/cytopathological diagnosis of glioblastoma.
• History of glioma radiation.
• Presence of a new or progressing enhancing brain lesion on follow-up clinical MRI suspicious for post-radiation glioma progression or late radiation-induced MRI changes (i.e., radiation injury), at least 7 mm in bidirectional diameter.
• The most recent MRI, used for comparison with the PET/CT, is performed within 4 weeks of the planned PET scan.

ADDITIONAL CRITERIA FOR ARM 3

Inclusion Criteria:

• MRI diagnosis of a brain tumor, previously verified to be a low-grade (WHO grade 2, IDH (isocitrate dehydrogenase) mutant glioma, based on histopathology from biopsy or resection.
• The detected mass on the most recent clinical MRI is at least 7 mm in bidirectional diameter (i.e., twice the PET scanner resolution).
• The tumor does not require urgent (within 1 month) resection, steroid treatment, or radiation.
• The most recent MRI, used for comparison with the PET/CT, is performed within 4 weeks.
• Patient agrees to have a baseline and follow-up PET/CT scan (approximately 1 month later) and interval oral treatment with 200mg/day minocycline.
• Due to planned minocycline treatment, patients will need to have adequate renal function

Exclusion Criteria:

• Active connective tissue disorders, such as lupus or scleroderma.
• History of allergic reaction to minocycline or any tetracyclines.
• Ongoing treatment with warfarin with INR > 1.5.
• History of colitis during antibiotics treatment.