Brain Imaging: What Are the Different Types?

Positron Emission Topography

Positron Emission Topography (PET) measures brain metabolism. Different applications of PET allow one to "see" pathology associated with Alzheimer's disease, for instance, that cannot be visualized any other way. Used in a different way, PET also allows doctors to see how different areas of the brain use oxygen or glucose - both very important to understanding not just what the damage might look like but also how the brain provides energy to itself.

T1-Weighted MRI

The T1-Weighted MRI is the standard imaging test and part of every general MRI exam. It provides doctors with a very clear view of brain anatomy and structure. It can also show damage in brain injury but generally only when the damage is very significant.

T2-Weighted MRI

The T2-Weighted MRI is also a standard part of every MRI exam. But unlike T1-weighted imaging, the T2 allows visualization of severe diffuse axonal injury such as what is expected following severe TBI.

Diffusion Weighted Magnetic Resonance Imaging

Diffusion Weighted MRI (DWI) shows alterations in tissue integrity. In ischemic injury - such as many types of stroke or when blood is not able to get to all parts of the brain - there is a chemical reaction in the cells. As the cells die because of lack of blood flow (with oxygen), there is an increase in sodium and this changes (increases) the amount of water in the tissue. DWI is very sensitive to this change. In fact, using DWI, doctors can identify a stroke or ischemic injury within seconds of occurrance.

Fluid-Attenuated Inversion Recovery MRI

Fluid-Attenuated Inversion Recovery (FLAIR) MRI is also sensitive to water content in brain tissue. This is very useful in patients who have reductions in brain tissue following an injury. Most commonly, however, FLAIR is used to visualize alterations in tissue in diseases such as multiple sclerosis.

Diffusion Tensor Imaging

Diffusion Tensor Imaging (DTI) shows white matter tracts in brain tissue. These tracts allow different parts of the brain to talk to each other. Think of the brain as if it were a computer. With DTI doctors can see and measure the "cables" connecting parts of the brain. DTI can provide information about damage to parts of the nervous system as well as about connections among brain regions.

Gradient Record MRI

Gradient Record MRI (GRE) shows blood or hemorrhaging in the brain tissue. This is very important in acute head injury. CT scans are also very useful in this stage but sometimes miss very small bleeds - or so called microbleeds - in the brain. MRI and types of MRI more sensitive to blood can identify these and allow doctors to monitor the patient.

Functional MRI

Functional MRI (fMRI) is a newer type of MRI that takes advantage of the iron in blood and the fact that when neurons fire there is - eventually - an increase in local iron in the areas where the neurons fired. For this imaging test, doctors ask patients to do something while in the MRI machine like opening and closing their right hand for 30 seconds and then opening and closing their left hand for 30 seconds. Then, the doctors model the change in signal associated with an increase in blood related to that task. So, areas involved in opening the right hand will show increased signal. This allows images to be created that reveal how the brain does tasks. This is potentially useful in TBI when the brain structures all appear normal but the brain is functioning in a different way. It is important to know that fMRI is not approved for clinical use for diagnosis of TBI.

Posted on BrainLine April 22, 2011.

Comments (4)

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Can you describe Progressive Supranuclear Palsy...and which tests would be used to diagnose?

Alcohol damage to the brain depends on how young the user was when drinking started, how much was imbibed, over how long a period, and the severity of the damage. There is also a genetic predisposition to alcoholism. SPECT scans show the damage. How much the brain can heal depends on the interventions, on too many variables, and no one can answer the question, but everything ought to be tried e.g neurofeedback, transcranial magnetic resonation, etc.
hi can a junior who plays football and had more than 4 conclussions in his life,that now has brusing on his brain please help me his in college but dont want him to continue to play football please explain to me what is brusing on his brain mean please help me!!!!!
hi i want to know does does the brain heal all the way back to normal from alcohol addiction?