Brain Imaging Techniques

Computed Tomography Scan (CT Scan) CT scans use a series of X- ray beams passed through the head. The images are then developed on sensitive film. This method creates cross-sectional images of the brain and shows the structure of the brain, but not its function. Image courtesy of the Yousef Mohammad, M.D., MSc; Assistant Professor of Neurology Division of Cerebrovascular Diseases, The Ohio State University Medical Center ge.html

Courtesy of Dr. Susan Courtney of the National Institute of Mental Health of the NIH. A person getting a PET scan lies down on a table. The brain is surrounded by detectors. The PET imager will be able to show, in three dimensions, where in the brain specific mental activities are taking place or where a tumor might be growing. The PET scanner picks these up because when a portion of the brain is active or when a tumor is growing, the flow of blood to that region is increased. The detectors pick up radiation emitted from tagged (radioactive) compounds that are injected into the person's vein right before the scanner is turned on. The compounds travel in the bloodstream and arrive in the brain within a minute or so. PET Scans

Magnetic Resonance Imaging (MRI)

How an MRI works Using strong magnets, radiofrequency waves are directed at protons, the nuclei of hydrogen atoms, in a strong magnetic field. The protons are first "excited" and then "relaxed," emitting radio signals that can be computer-processed to form an image. In the body, protons are most abundant in the hydrogen atoms of water—the "H" of H2O —so that an MR image shows differences in the water content and distribution in various body tissues. Even different types of tissue within the same organ, such as the gray and white matter of the brain, can easily be distinguished.

The “sections” of an MRI in action

An “fMRI” of a patient involved in using the sense of sight Functional MRI Functional MRI detects changes in blood flow to particular areas of the brain. It provides both an anatomical and a functional view of the brain. A fMRI scan showing regions of activation in orange, including the primary visual cortex

How fMRI technology works fMRI uses MRI technology to identify regions of the brain where blood vessels are expanding, chemical changes are taking place or extra oxygen is being delivered—all signs that this part of the brain is currently processing information and giving commands to the body.

Thalamus Cortex These 2 images show the averaged data from 14 subjects who received a painful injection of the chemical capsaicin into the upper arm. The colored part of the images show increased blood flow (the PET) to the thalamus and primary somatosensory cortex after the injection. The gray areas of the images (the MRI) show the brain anatomy. So using this method can identify the areas of the brain that are active during specific conditions. This technique could be used to study just about any other cognitive function.capsaicin (These two PET/MRI images were provided by Dr. Robert C. Coghill at Wake Forest University School of Medicine. ) Here are some examples of using a combination of PET and MRI techniques: