Diagnosis of Brain Cancer
The first step in diagnosing brain cancer involves evaluating symptoms and taking a medical history. If there is any indication that there may be a brain tumor, various tests are done to confirm the diagnosis, including a complete neurological examination, imaging tests, and biopsy.
Imaging Tests to Diagnose Brain Cancer
Magnetic resonance imaging (MRI scan) is the diagnostic test of choice for brain cancer. ELectromagnetic energy produces detailed computer images of the brain from different angles. It can detect edema (swelling of brain tissue) and hemorrhage (bleeding). In some cases, a dye is injected intravenously to improve the contrast between an abnormal mass and normal tissue.
Computed axial tomography (CAT or CT scan) involves the use of x-rays and a computer to obtain images of the brain. A dye is often injected intravenously to improve the contrast between an abnormal mass and normal tissue. Not only can the tumor be seen, but the type of tumor sometimes can be identified with a CT scan.
Positron emission tomography (PET scan) helps the physician evaluate brain function and cell growth by producing images of physical and chemical changes in the brain. An injected radiopharmaceutical substance is absorbed by tumor cells in the brain. Measurements of brain activity are determined by concentrations of the substance and then fed into a computer, which produces an images of the brain.
PET can precisely locate a tumor and detect metastatic and recurrent brain cancer at earlier stages than MRI or CT scan. This technique also can be used to evaluate the tumor's response to chemotherapy and radiation treatment.
Brain Tumor Biopsy
Examination of tumor tissue is the only way to arrive at an exact diagnosis of the tumor. In a biopsy, a small part of tumor tissue is removed surgically and then sent to a lab, where a pathologist examines it.
The type of tumor is determined by the type or types of cells (called grading) seen under the microscope, and, if malignant, the stagethat is, the degree of invasiveness, the growth rate, and the cancer cells' similarity to normal cellsis also determined.
In stereotactic biopsy imaging tests are used to locate the tumor, a small hole is made in the skull, and a hollow needle is passed through to obtain a core of tumor tissue. Examination of the sample provides an accurate diagnosis in over 90 percent of cases.
Possible complications resulting from the procedure include blood clot, hemorrhage, and infection. The rate of complications is very low, about 3 percent.