Thanh: A book of First Class stamps converting celexa to lexapro Developed by Xie and colleagues in 2008, SRS works by shining non-invasive lasers into tissue and detecting the weak signal that emerges. By analyzing the signal’s spectrum, researchers can build images of the cellular makeup of the tissue. By amplifying those signals, they transform a technique that once took hours or days into one that works in real time, and could offer a critical insight to surgeons in the operating room.