In a stereotactic needle biopsy, an MRI scan is done to determine the exact location of the tumor in the brain while the head is held still in a frame, states WebMD. A small hole is made in the skull and a needle guided through the hole to the tumor.
A stereotactic needle biopsy, or stereotaxis, may be done for brain tumors in hard-to-reach areas or very sensitive areas within the brain that may be damaged by a more extensive operation, explains Mayo Clinic. After the neurosurgeon removes tumor tissue using the needle guided by the MRI scan, the biopsy sample is viewed under a microscope by a pathologist to determine if it is cancerous or benign.
Magnetic resonance imaging, or MRI, is commonly used to help diagnose brain tumors, according to Mayo Clinic. In some cases a dye may be injected through a vein in the arm during the MRI study. A number of specialized MRI scan components, including functional MRI, perfusion MRI and magnetic resonance spectroscopy, may be used to evaluate the tumor and plan treatment. Other imaging tests may include computerized tomography, also known as a CT or CAT scan, and positron emission tomography, also known as a PET scan.