A University of Waterloo engineer’s MRI invention reveals better than many existing imaging technologies how COVID-19 can change the human brain.
Feasibility of diffusion tensor and correlated diffusion imaging to study white matter microstructural abnormalities: application in COVID-19 Summary There has been increasing attention on the effect of COVID-19 on white matter microstructure, especially among those who self-isolated after becoming infected. There is also great scientific interest and potential clinical utility in evaluating the sensitivity of single-layer diffusion magnetic resonance (MR) methods to detect such effects. In this work, we compare the performances of three single-layer supported diffusion MRI modeling methods for detecting the effect of COVID-19, including diffusion tensor imaging, diffusion tensor decomposition of orthogonal moments, and correlated diffusion images. Imaging was performed on self-isolated patients at baseline and at 3-month follow-up, along with age- and sex-matched controls. We demonstrate through simulations and experimental data that correlated diffusion imaging is associated with much higher sensitivity, being the only one of three single-layer methods to demonstrate COVID-19-related brain effects. The results suggest less restricted diffusion in the frontal lobe in patients with COVID-19, but also more restricted diffusion in the white matter of the cerebellum, in accordance with several existing studies highlighting the vulnerability of the cerebellum to COVID-19 infection. . These results, together with the simulation results, suggest that a significant proportion of COVID-19-related white matter microstructural pathology manifests as a change in tissue diffusivity. Interestingly, different b values also confer different sensitivities to the effects. No significant differences were observed in patients at 3-month follow-up, probably due to the limited size of the follow-up cohort. In summary, correlated diffusion imaging proves to be a viable single-layer diffusion analysis approach that allows us to uncover opposing patterns of diffusion changes in the frontal and cerebellar regions of COVID-19 patients, suggesting that the two regions react differently to viral infection. |
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The new imaging technique known as correlated diffusion imaging (CDI) was developed by systems design engineering professor Alexander Wong and was recently used in a groundbreaking study by scientists at Baycrest’s Rotman Research Institute and Sunnybrook Hospital. in Toronto.
“Some may think that COVID-19 affects only the lungs,” Dr. Wong said. “What was found is that this new MRI technique we created is very good at identifying changes in the brain due to COVID-19. “COVID-19 changes the white matter in the brain.”
Wong, a Canada Research Chair in Artificial Intelligence and Medical Imaging, had previously developed correlated diffusion imaging (CDI) in a successful search for a better imaging measure to detect cancer. CDI is a new form of MRI that can better highlight differences in the way water molecules move in tissue by capturing and mixing MRI signals at different gradient pulse intensities and times.
Researchers at Rotman, a world-renowned center for the study of brain function, saw Wong’s imaging discovery and thought it could probably also be used to identify changes in the brain due to COVID-19. Subsequent tests proved the theory correct. CDI imaging of frontal lobe white matter revealed less restricted diffusion of water molecules in COVID-19 patients. At the same time, it showed a more restricted diffusion of water molecules in the cerebellum of COVID-19 patients.
Wong highlights that the two brain regions react differently to COVID-19 and points to two key findings from the research. First, the human cerebellum could be more vulnerable to COVID-19 infections. Second, the study reinforces the idea that COVID-19 infections can cause changes in the brain.
Not only is Rotman’s study one of the few to have demonstrated the effects of COVID-19 on the brain, it is the first to report diffusion abnormalities in the white matter of the cerebellum . Although the study was designed to show changes, rather than specific damage, in the brain from COVID-19, its final report looks at potential sources of those changes, and many relate to disease and damage.
In response, Wong suggests that future tests could focus on whether COVID-19 actually damages brain tissue. Additional studies could also determine whether COVID-19 can change the brain’s gray matter.
“Hopefully, this research can lead to better diagnoses and treatments for COVID-19 patients,” Wong said. “And that could be just the beginning for CDI, as it could be used to understand degenerative processes in other diseases such as Alzheimer’s or to detect breast or prostate cancers.”
The study, Feasibility of Diffusion Tensor and Correlated Diffusion Imaging for Studying White Matter Microstructural Abnormalities: Application in COVID-19, involving Wong and his student Hayden Gunraj as co-authors, is published in the journal Human Brain Mapping .
