Albuquerque, N.M., Mar. 28 -- Scientists at the US Department of Energy's Sandia National Laboratories have developed what they describe as a smart scalpel that can distinguish between cancerous and healthy cells as a surgeon cuts away a tumor obscured by blood, muscle and fat. Called a biological microcavity laser, the device is expected to help surgeons more accurately remove malignant growths while minimizing the amount of healthy tissue involved. According to researchers, the patented device would essentially tell a surgeon when to stop cutting. We can quickly identify a cell population that has abnormal protein content, as do tumor cells, by passing only a few hundred cells -- a billionth of a liter -- through our device, says Paul Gourley, leader of the Sandia team.The scalpel works by incorporating blood cells into the lasing process. Individual cells are pushed by a micropump through tiny channels cut into the glass surface of the device; the cells are then entered by a vertical microlaser beam. The additional protein present in cancerous cells lends these cells added density, which changes the speed of the laser light passing through them. A receiver registers this change as a difference in output frequency and transmits the reading by optical fiber to a laptop computer a few feet from the instrument. The data is translated by means of an algorithm into a constantly changing graph that provides surgeons with information that shows when blood pumped from the incision has been cleared of cancerous cells.