Diffusion imaging is not limited to basic measures such as classical DTI FA (fractional anisotropy); other microstructure measures can be of major interest. Free-water  is a telling example.

Imeka’s diffusion imaging tools are able to measure extracellular water fraction (free-water), which in turn can be sensitive neuroinflammation.

There is currently no way to measure inflammation in white matter. Certain PET markers are in development, but they are not considered as usable options in the near future. Furthermore, PET imaging is a highly invasive and expensive.

Free-water imaging based on diffusion MRI  is a fast and cost-effective method that can help understand neuroinflammation, and it is available today.

Imeka’s infrastructure is already used in a clinical trial setting. For example, our team has worked on existing databases (ADNI, ADNI+, ADNI2) and significant differences between normal, MCI and AD groups were observed based on this measure.

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Neuroinflammation is undeniably a subject of great importance, and it will remain so in the foreseeable future. Imeka is currently the only company to use diffusion MRI tools to help understand inflammation in the white matter.

Imeka and Pfizer collaboration

Imeka’s expertise with free-water imaging lead to a collaboration with Pfizer, a project that became the subject of an abstract at the 2018 ISMRM conference.

The principle behind the technique

The diffusion MRI signal can be modeled by a tissue part and free-water part. It’s a simple, yet powerful way of assessing extra-cellular water, which can be associated with neuroinflammation.

It’s a simple, yet powerful way of assessing extra-cellular water which can be associated with inflammation.

Time matters

The acquisition time necessary for us to get proper data to perform processing is short. In the order of 5 minutes of diffusion MRI in the protocol.

Legacy dataWe are also able to work with data that was acquired in the past. With a limited amount of directions of acquisition (20 or more), we can perform free-water modelling and advanced tractography from legacy data.

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Revealing more with free-water

Free-water imaging can also be used to remove free-water from the signal. This is particularly useful in cases of brain lesions in order to discern what’s hidden within.
The best example? Multiple Sclerosis. We have been able to “track” through lesions by removing the free-water component of the signal.

Differentiating edema from tumour

Another very important aspect of the free-water component for neurosurgeons is that we can help differentiate edema from tumor and from sane tissue in the brain.

Why not turn to NODDI?
If you have multi-shell data available, more advanced modelling techniques such as NODDI (neurite orientation dispersion and density imaging) or crossing-fiber, robust microstructure modelling can be done.

At the moment, multi-shell acquisitions do not scale well outside research centers with research keys, which means single-shell solutions should be preferred for eventual multi-site clinical trials.

Free-water modelling is suited to single-shell data and give the fraction of extra-cellular water, as NODDI does from a multi-shell acquisition.

Imeka can produce comparable results without the need for multi-shell imaging.
Our technology’s acquisition time is shorter, and our sequence can be done on any MRI in the world.

Our processing pipeline is fully robust to single-shell diffusion MRI with 20+ directions.

Imeka’s role towards finding a cure to Alzheimer’s
Our current projects in Alzheimer’s are centered on “whole white matter” free-water imaging. Meaning that we average the white matter metrics across the white matter of each brain being studied. Using that technique, we see significant differences between control groups and Alzheimer’s disease groups. However, we do believe that we could be even more precise by looking at specific pathways in the brain, which we can extract thanks to our unique and powerful expertise in fiber tractography and fiber bundling