Quantitative MRI of Tissue Properties in the Human Brain

Project Background

Magnetic resonance imaging (MRI) is a critical tool for the clinical assessment of brain disease. A non‐invasive method that does not use ionizing radiation, MRI enables the scientist and clinician to visualize the human brain without harming the subject. Yet, there is an important limitation of most MRI methods that is not widely appreciated: In most clinical applications of MRI, diagnoses are based on a qualitative assessment of image appearance. The qualitative nature of the MRI data significantly limits their utility; without units, scientists and clinicians cannot rigorously compare images obtained at different MR sites or even from the same individual at different points in time. Just as we have units to record a child’s height or a patient’s temperature, we need quantitative MR measures to assess brain development or the effect of a drug on neural tissue.

A New Method

Aviv Mezer, from our research group, has developed a new MRI technique that produces remarkably precise and quantitative measurements of human brain tissue in vivo (Mezer et al., 2012; Mezer et al., 2013). The method will have significant scientific and clinical applications for understanding human cognition and neurological disease.

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How it works

The method we have developed estimates both the tissue (macromolecules and lipid membrane) volume and the rate of interaction between water molecules and the tissue surface. These fundamental brain tissue biomarkers are measured at high resolution, within each brain voxel (roughly 1 mm3). These measurements are quantitative and thus can be meaningfully compared across sites and within a single individual across time. The MR scans are efficient, and the calculations are simple and fast enough to be used in any clinical MR center. Stanford recently applied for a patent on the method (Mezer, 2012); preliminary results are summarized in an article that is published in Nature Medicine.

Application

The quantification of tissue volume and tissue‐water interaction rates will have significant value for scientists seeking to monitor healthy brain development across the lifespan as well as for clinicians characterizing and monitoring brain pathologies (Tofts, 2003 ). For example, we are applying the method in our research lab to understanding tissue development in pathways essential for learning to read; and we are collaborating with colleagues in the Medical School on applying the method to multiple sclerosis (MS).