The goal of this clinical trial is to evaluate the value of 99mTc-CNDG for diagnosis of brain tumors by comparing it with 18F-FDG-PET. The main questions it aims to answer are:

1. What is the diagnostic consistency between 99mTc-CNDG and 18F-FDG?
2. What is the correlation between the SUVmax value of 99mTc-CNDG and tumor type?

Participants will:

Receive18F-FDG-PET and 99mTc-CNDG examination within 2 weeks before surgery. Obtain pathological diagnosis by surgery or biopsy as the gold standard.

Inclusion Criteria:

• Patients with clinical diagnosis of brain tumor;
• Be at least 18 years old;
• The final pathological results could be obtained by surgery or biopsy;
• Informed consent and the ability to be followed up;
• Those who did not meet the exclusion criteria.

Exclusion Criteria:

• Insulin-dependent diabetes mellitus or fasting blood glucose >7 mmol/L before 99mTc-CNDG injection;
• Severe liver or kidney disease (serum creatinine level >3.0mg/dL or any liver enzyme level ≥ 5 times the upper limit of normal);
• Severe hypersensitivity or hypersensitivity to radiocontrast agents;
• Claustrophobia (inability to undergo SPECT/CT or PET/CT scans);
• Patients receiving radiotherapy and chemotherapy;
• Being pregnant or breastfeeding.