A pen-like device that collects both fluorescence and Raman spectra could enable more accurate surgeries to remove tumors.
The SpectroPen in the lab setting: Michael Mancini (left) and Aaron Mohs used the SpectroPen to detect a breast tumor model grown in a nude mouse.
A device shaped like a pen collects both fluorescence and Raman spectra from tissue; it can detect cancerous tissue at the edges of tumors and satellite tumors during surgery. This could guide surgeons for more accurate surgery to remove tumors. Removing all the cancer during surgery is the single most important predictor of patient survival for almost all solid tumors, but the difference between cancerous and benign tissue isn't always obvious to the eye.
In an animal study, the SpectroPen, developed by a team of researchers led by Shuming Nei of Emory University and Georgia Tech, was used to precisely detect the borders of the tumor before and during surgery using two near-IR contrast agents (Anal. Chem., doi: 10.1021/ac102058k).
The handheld device incorporates optical fibers for emitting light from a diode laser at 785 nm, and collecting both fluorescence and surface-enhanced Raman scattering (SERS) signals, which are filtered in the "pen" and resolved into spectra in the spectrometer at the far end of the fibers. The tissue is treated with either a fluorescence contrast agent (indocyanine green) and a SERS contrast agent (pegylated colloidal gold), which gathers at tumors.
The other imaging methods for use during operations have their own drawbacks: MRIs cost a lot and extend the length of the surgery, while sonography misses small masses. In trials on mice, the SpectroPen was able to provide indications of whether tissue contained high levels of the target molecules, and indicated the presence of secondary tumors. Studies of excised tissue showed that signals could be resolved through 5 to 10 mm of flesh. (The fluorescence signals penetrated better through fat tissues, which implies that it may be useful for fat-rich tissues such as breasts.)
Next, Nie says, "we plan to test the use of our SpectroPen for image-guided surgery of spontaneous tumors in companion dogs." In addition, "our collaborator Sunil Singhal at the University of Pennsylvania has just obtained institutional review board approval for clinical feasibility studies of lung cancer patients."
Yvonne Carts-Powell is a freelance science writer who specializes in optics and photonics.