The images were also three-dimensional, an effect that the researchers achieved by moving the laser up and down and back and forth while spinning the mouse. A similar principle is used in clinical computed tomography (CT) scans, which use x-rays instead of infrared light and an imaging system that moves around the patient.
Improving image resolution by catching early-arriving photons isn’t a new idea, but it took some technical finesse to make it happen. Bruce Tromberg, director of the Laser Microbeam and Medical Program at the University of California, Irvine’s Beckman Laser Institute, says that the new work is “retro cool.” When researchers like Tromberg first started working on imaging with infrared light, they hoped to look at the early-arriving photons but didn’t have good enough fluorescent markers or hardware. Now that better markers and cameras are available, Tromberg says, it’s logical to revisit the idea.
Arjun Yodh, a professor of physics and astronomy at the University of Pennsylvania and another optical-imaging pioneer, is skeptical that the new approach will work in thick tissues in people, where the scattering is greater than it is in a mouse’s chest cavity. Niedre himself cautions that the work is still in its early stages, and that the instrumentation and image processing will need substantial improvement before the technique can be applied to larger animals and humans.
Until that time, the technique will allow researchers to study the progression of cancer in greater detail in animal models. Much of the basic biology of cancer is still a mystery–in particular, the molecular processes that allow it to spread from the initial tumor site to others throughout the body–and the new technique will give biologists a better look.