MR Research Lab: Imaging Techniques

Imaging Techniques

The MR Research Laboratory is equipped to collect a variety of data types, both qualitative and quantitative. Several of the data acquisition techniques used in the laboratory are described below.


Conventional Structural MRI

In clinical practice, MRI is primarily used for the acquisition of structural images that provide cross sectional views of internal structures. All three MR systems in the laboratory can be used to acquire structural anatomic images. Structural images are used by researchers for the establishment of diagnoses, measurement of tissue volumes, monitoring the effects of treatment, and can serve as localization references for other types of information that can be acquired with MR, such as localized spectroscopy.

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MR Angiography

MR angiography (MRA) provides a clear view of blood vessels throughout the body non-invasively. MRA techniques use physical properties of blood flow to selectively enhance the appearance of arteries and veins. Conventional MRA often does not require injection of a contrast agent prior to imaging. Contrast-enhanced MRA can be used in select situations to provide detailed vessel information useful in research with specific vascular interests and needs.

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Functional MRI

With functional MRI (fMRI), rapid dynamic images are acquired at a rate of approximately 1 image every 100 milliseconds. The images are used to derive information about regional changes in blood flow and blood oxygenation to identify areas of the brain associated with specific tasks. This non-invasive technique requires no injection and is highly sensitive to the brainís response to motor, sensory and cognitive tasks. With this technique, investigators throughout the UW community utilize the MR Research Laboratory resources to study a variety of neurodevelopmental and neurodegenerative disorders, including dyslexia, autism, HIV dementia, fetal alcohol syndrome, traumatic brain injury, stroke and multiple sclerosis.

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MR Spectroscopy

Magnetic resonance spectroscopy (MRS) allows scientists to detect, compare, and quantify the concentration of a variety of biological metabolites. MR Research Laboratory systems are used to perform these measurements in very specific locations in the body for sample sizes down to the order of approximately 1 cubic centimeter of tissue in vivo. Techniques have also been developed in the lab to calculate the spatial distribution of different metabolites across cross sections of tissue in the brain.

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Functional MR Spectroscopy

MR Spectroscopy can be used to measure dynamic changes in chemical concentrations over time. This technique is called functional MR spectroscopy (fMRS). One application of this technique is recording changes in chemical concentrations in the brain as a subject performs a task, using methodology analogous to that used for fMRI.

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Perfusion Imaging

MR can also be used to generate images that measure blood flow through the brain capillaries, also known as tissue perfusion. This can be done using either a contrast agent or with a non-invasive MR technique called arterial spin labeling (ASL).

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CSF Flow Imaging

Quantitative measurements of the velocity and volume of cerebral spinal fluid (CSF) flow can be obtained using special MR acquisition and data analysis techniques. These methods allow scientists to dynamically view CSF flow and to calculate both the speed and direction as it changes due to vascular pulsation and respiration. Specific flow measurements in regions of interest are useful for evaluating abnormalities in the spaces in and surrounding the brain and spinal cord, such as Chiari malformation or arachnoid cysts.

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Diffusion Tensor Imaging (DTI)

Diffusion tensor imaging (DTI) is a MRI technique that enables the measurement of the restricted diffusion of water in tissue. The principal application is in the imaging of white matter where the location, orientation, and anisotropy of the tracts can be measured. The architecture of the axons in parallel bundles, and their myelin sheaths, facilitate the diffusion of the water molecules preferentially along the dominant direction. Such preferentially oriented diffusion is called anisotropic diffusion. Scientists have used DTI to study white matter fiber tract differences between dyslexic and normal readers.

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Last Modified: Wednesday, 19-Dec-2007 14:13:52 PST