PHOENIX –
Chris Richards/University of Arizona
Dr. Jennifer Barton, director of the University of Arizona BI05 Institute, has spent years developing a device small enough to image the fallopian tubes.
In a lecture during a multispecialty roundup of cutting-edge energy-based device applications at the annual conference of the American Society for Laser Medicine and Surgery, Dr. Barton, a biomedical engineer who directs the BIO5 Institute at the University of Arizona, Tucson, said that while no current modality exists to enable physicians in dermatology and other specialties to view internal structures throughout the entire body with cellular resolution, refining existing technologies is a good way to start.
In 2011, renowned cancer researchers Douglas Hanahan, PhD, and Robert A. Weinberg, PhD, proposed six hallmarks of cancer, which include sustaining proliferative signaling, evading growth suppressors, resisting cell death, enabling replicative immortality, inducing angiogenesis, and activating invasion and metastasis. Each hallmark poses unique imaging challenges. For example, enabling replicative immortality “means that the cell nuclei change size and shape; they change their position,” said Dr. Barton, who is also professor of biomedical engineering and optical sciences at the university. “If we want to see that, we’re going to need an imaging modality that’s subcellular in resolution.”
Similarly, if clinicians want to view how proliferative signaling is changing, “that means being able to visualize the cell surface receptors; those are even smaller to actually visualize,” she said. “But we have technologies where we can target those receptors with fluorophores. And then we can look at large areas very quickly.” Meanwhile, the ability of cancer cells to resist cell death and evade growth suppressors often results in thickening of epithelium throughout the body. “So, if we can measure the thickness of the epithelium, we can see that there’s something wrong with that tissue,” she said.
As for cancer’s propensity for invasion and metastasis, “here, we’re looking at how the collagen structure [between the cells] has changed and whether there’s layer breakdown or not. Optical imaging can detect cancer. However, high resolution optical techniques can only image about 1 mm deep, so unless you’re looking at the skin or the eye, you’re going to have to develop an endoscope to be able to view these hallmarks.”
OCT images the tissue microstructure, generally in a resolution of 2-20 microns, at a depth of 1-2 mm, and it measures reflected light. When possible, Dr. Barton combines OCT with laser-induced fluorescence for enhanced accuracy of detection of cancer. Induced fluorescence senses molecular information with the natural fluorophores in the body or with targeted exogenous agents. Then there’s multiphoton microscopy, an advanced imaging technique that enables clinicians to view cellular and subcellular events within living tissue. Early models of this technology “took up entire benches” in physics labs, Dr. Barton said, but she and other investigators are designing smaller devices for use in clinics. “This is exciting, because not only do we [view] subcellular structure with this modality, but it can also be highly sensitive to collagen structure,” she said.