More than 26,000 people are diagnosed with primary cancers of the brain and nervous system each year in the United States, and many more develop metastatic brain cancers resulting from primary tumors in other parts of the body. Neurosurgery can help to achieve several goals in patients with brain tumors, including decreasing tumor mass, relieving seizures and other symptoms, and prolonging overall survival. However, brain surgery is also associated with the risk of damaging regions of the cerebral cortex that are important for language, sensory and motor function, or other tasks. Functional magnetic resonance imaging (fMRI) allows surgeons to visualize critical regions of the cerebral cortex to aid in surgical planning and to assess the potential risk of permanent brain injury associated with surgical intervention. This approach uses the blood oxygen level-dependent (BOLD) effect, which is based on differences in magnetic resonance signal properties between oxygenated and deoxygenated hemoglobin in the brain. Patients are asked to complete a number of sensory, motor, or language-related tasks, which result in activation of corresponding brain regions and a corresponding increase in cerebral blood flow. fMRI detects the increased presence of oxygenated hemoglobin associated with these hemodynamic changes. fMRI is able to identify brain regions that are important for language or other cognitive tasks with a high level of precision, even when the anatomy of the brain has been altered due to tumor growth or prior surgery. Patient preparation is essential to ensure success of the fMRI session, including screening to identify appropriate patients, ensuring patients understand task requirements, and minimizing or correcting for head motion. It is also essential to understand potential limitations for fMRI, including artifacts associated with prior surgery, the presence of metal or medical devices, and effects of image processing.
After reading this article, the participant should be able to:
- Discuss the rationale for functional magnetic resonance imaging (fMRI) in the evaluation of patients with brain tumors, including the physiologic basis of fMRI and the advantages and disadvantages of the technique.
- List cortical regions that are especially important in sensory, motor, and language testing; and identify fMRI paradigms that are used to identify these regions.
- Describe guidelines and procedures and increase the likelihood of successfully performing fMRI in patients with brain tumors.
Categories: Magnetic Resonance Imaging, Radiology