The earlier cancer is detected, the better the odds of treating it. But of course tumors can be hard to spot until they get to a certain size, at which point it might be too late. Now MIT researchers have developed a new optical imaging system that could be used to spot tiny tumors deep inside the body.
Currently, there's a bit of a trade-off in medical imaging between depth and resolution. MRI and CT scans can see all the way through the body but will miss tumors smaller than about 1 cm (0.4 in). Optical imaging techniques, on the other hand, can see smaller tumors but can't peer any deeper into the patient than about 3 cm (1.2 in).
"We want to be able to find cancer much earlier," says Angela Belcher, co-lead author of the study. "Our goal is to find tiny tumors, and do so in a noninvasive way."
For the new study, the researchers tried to get the best of both worlds. With its longer wavelengths, near-infrared light can be used to penetrate deeper into the body than other optical methods, and do so at a higher resolution. The trick is to image in multiple near-infrared wavelengths at once, a process known as hyperspectral imaging.
These signals can then be picked up from outside the body and analyzed using algorithms developed by the team, to identify where in the body a probe is and how deep it is. The team calls their system DOLPHIN, for "Detection of Optically Luminescent Probes using Hyperspectral and diffuse Imaging in Near-infrared."
To test the DOLPHIN system, the team used probes containing different nanoparticles that would fluoresce in different wavelengths of near-infrared light. They then had mice swallow the probes and tracked their progress through the digestive system. That's particularly impressive given that the probes were just 0.1 mm long, far smaller than is usually possible with optical imaging.
Better yet, the team also broke depth records. In another test, particles were injected into the bodies of mice and rats, and could be seen as deep as 4 cm (1.6 in). That maximum depth was doubled when they tested on samples of animal tissue and human-like tissue.
As it stands, this was just a proof of concept to see if it was possible to use the DOLPHIN system to image something so small, so deep in the body. And now that it works, the team plans on adapting the probes so they can seek and tag tumors, making them fluorescent.
"In terms of practical applications, this technique would allow us to non-invasively track a 0.1-millimeter-sized fluorescently-labeled tumor, which is a cluster of about a few hundred cells," says Neelkanth Bardhan, co-lead author of the study. "To our knowledge, no one has been able to do this previously using optical imaging techniques."
The team's first target is ovarian cancer, which is notoriously difficult to detect until it's too late. Pancreatic, brain and skin cancers are also in the crosshairs.
The research was published in the journal Scientific Reports.