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OHSU Biomedical Engineers develop technique to determine the weight of particles so small, you need a microscope to see them

Research may aid several fields: From diagnosing disease to studying bacteria

Researchers at Oregon Health & Science University (OHSU) have developed a technique that, similar to a carnival barker at the circus, can determine weight based on appearance. Today, an article outlining the technique was published in the Physical Review Letters, a premier journal in the physics field. The results of the article will pave the way for microscope users to perform mass measurements on a cellular level.

The optical imaging technique, called tomographic bright field imaging (TBFI) could be applied in various scientific research settings and has the potential to directly impact blood cell research in cancer patients, explained Owen McCarty, Ph.D., associate professor in the Department of Biomedical Engineering in the OHSU School of Medicine and research member at the Knight Cancer Institute.

The study was led by Kevin Phillips, Ph.D., a postdoctoral fellow in the OHSU Department of Biomedical Engineering; and included Steven Jacques, Ph.D., professor, OHSU Department of Biomedical Engineering.

“TBFI could play a significant role in personalized cancer treatment,” said McCarty, who is the senior author of the article. “It utilizes certain metrics to measure cell mass. So for instance, it could be used to monitor growth dynamics and gauge the progression of a patient’s battle with cancer over time.”

TBFI applies a complex algorithm to analyze how light passes through a cell and combines those data – called the refractive index – with the cell’s dimensions and volume, resulting in a three-dimensional view of the cell’s mass. These data can be gathered through the use of a common microscope, the variety that can be found in any standard biology lab. Until now, these measurements have relied on custom-built instruments, complex mathematical analysis and the use of ‘biomarkers’ such as a stain or protein injected into the cell that makes it easier to see through a microscope.


The image above shows a TBFI reconstruction of refractive index and dry mass density of red blood cells. (a) Red blood cells as seen through the commonly used light microscope, (b) refractive index map of red blood cells computed using TBFI, (c) mass density map of red blood cells.

The TBFI technique could also benefit other scientific research from environmental toxicology to microbiology to botany, as it will help scientists measure cellular specimens related to environmental changes over time.

The study was supported, in part, by the National Cancer Institute (NCI), part of the National Institutes of Health (NIH), through grant numbers U54CA143906 and P30CA069533.

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