Ryn Flaherty Defends PhD in Biomedical Imaging and Technology

Ryn Flaherty has successfully defended his PhD thesis in biomedical imaging and technology at NYU Grossman School of Medicine. The defense was held on Monday, September 8, at NYU Langone Health.

In his dissertation titled “Advanced In Vivo Diffusion and Magnetization Transfer MRI Biomarkers in Older Adults with Subjective Cognitive Decline,” Dr. Flaherty furthers the search for early signs of neurodegenerative risk. His doctoral investigations were advised by Mariana Lazar, PhD, associate professor of radiology at NYU Langone and scientist with the Center for Advanced Imaging Innovation and Research.

Subjective cognitive decline (SCD), a self-reported experience of declining cognition and memory, affects one in nine adults age 45 and older in the U.S. and is a growing public health issue, according to the Centers for Disease Control and Prevention. The term, coined about a decade ago, describes deficits that are felt but fall below the threshold of cognitive impairment on objective tests. For most people, the experienced dulling of the mental blade is medically benign. But for some, SCD turns out to be an early harbinger of neurodegenerative conditions collectively known as Alzheimer’s disease and related dementias (AD/ADRD).

There is no cure for AD/ADRD, but early biomarkers of risk would bring several benefits. Advance notice could enable early interventions to delay the onset and slow down the progression of disease, and predictive markers could inform ongoing research aimed at understanding AD/ADRD and developing effective therapies. Researchers know that degenerative changes in brain tissue begin long before behavioral symptoms emerge. But how to detect such changes in people who still appear cognitively healthy? Dr. Flaherty’s research focuses on advanced MRI techniques as a possible answer.

Drawing from the Cambridge Centre for Ageing and Neuroscience dataset—a publicly available collection that includes brain MRIs and the results of a cognitive battery—Dr. Flaherty and colleagues analyzed diffusion weighted imaging and magnetization transfer imaging data to derive a number of metrics sensitive to particular features of tissue microstructure. Then, the scientists searched for group differences between people who reported memory problems and those who did not.

The team focused on the medial temporal lobe, an area critical to memory and one where Alzheimer’s-related changes tend to appear first. The analyses based on diffusion tensor imaging showed differences between groups in several locations. In a 2024 publication detailing their findings, Dr. Flaherty and colleagues report that the diffusion profiles of the SCD group “are suggestive of a mixed neuroinflammatory and neurodegenerative pathology,” indicating the potential of diffusion MRI as a marker of risk.

In the abstract to his dissertation, Dr. Flaherty writes that diffusion weighted imaging biomarkers “provide evidence of demyelination and inflammation in SCD, as well as accelerated aging and associations with cognition” and calls for further research in this area.

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