Types of Imaging - Neurology in the Speech Language Pathology Field

Types of Structural Imaging

1. Computerized Tomography (CT) is a form of structural imaging. It uses X-Ray beams that reflect of body's dense tissues, like bone. A 2D image is produced that can be rendered into a 3D image. The advantages of CT imaging include that it is commonly used, easily accessible, inexpensive, and has a quick processing time. The disadvantages include the use of x-rays causes a cancer risk, it shows structure only, there is a difficulty observing new damage, and it has a poor clarity of image

2. Magnetic Resonance Imaging (MRI) is a form of structural imaging. Magnetic current is applied to body that flips proton's in body's water molecules. It produces a 3D image. The MRI produces much better images than the CT, it has multiple dimension images, there are no x-rays involved, and no preparation is needed (e.g. injections, etc.) However, the MRI is more expensive with CT, it is dangerous for patients with metal in their body, patients must be still, and those with claustrophobia may struggle with the exam.

There are 2 techniques involved in Functional Imaging:

1. Spatial Resolution: The location of brain activity when a stimulus is introduced

2. Temporal Resolution: The time between a stimulus is presented and the brain's response to that stimulus.

Types of Functional Imaging

1. Positron Emission Tomography (PET) is used when active brain areas need more energy. The image is based on glucose metabolism in the brain. It uses radioisotope and emitted radiation is detected and an image is formed from it. The PET scan produces a good image of location of brain activity, but it is invasive because of injections, uses radioactive material, and is more expensive than a CT and MRI.

2. Magnetoencephalography (MEG) and Electroencephalography (EEG) both show electrical responses to a particular stimulus. Stimuli can be presented in any modality: visual, auditory, somatosensory, or olfactory. The advantages include that they have a low cost, are readily available, and shows good information on brain function. The disadvantage is the poor image quality.

Structural + Functional Imaging: fMRI

1. Functional Magnetic Resonance Imaging (fMRI) uses blood oxygenation in the brain during introduction of a stimulus. It is safe and allows us to see structural and function at the same time. However, it is expensive and not wide spread

Why is Neurological Imaging important?

Neuroimaging techniques are exciting, continuing developing tools that help us understand the power of the brain. We can use these techniques to understand relationships between the brain, language, and other cognitive functions. It Is important to be familiar with neuroimaging techniques so that you can be a good consumer of research and clinical information.