In the hope of helping oncologists remove every piece of tumor tissue during surgery, researchers are developing new imaging tools that work in real time in the operating room. European researchers have now demonstrated that a chemical analysis instrument called a mass spectrometer can be coupled with an electroscalpel to create a molecular profile of tissue during surgery. The researchers have shown that the method can be used to map out different tissue types and distinguish cancerous tissue. The device will begin clinical trials next month.

"When a surgeon is performing cancer surgery, he doesn't have any direct information on where the tumor is," says Zoltán Takáts, a professor at Justus-Liebig University in Giessen, Germany. Instead, surgeons rely on preoperative imaging scans and on feedback from pathologists examining tissue biopsies under a microscope. "We want to provide a tool that's right in their hands, so that if they think a structure looks suspicious, they can just test it," says Takáts.

Mass spectrometry, a very precise method for identifying molecules by analyzing the ratio between their mass and charge, is already being used by a handful of research groups to study biological samples. Researchers have known for many years that tumor tissue and healthy tissue have different molecular profiles and that this can be used to tell them apart, or even to determine how aggressive a particular tumor is. Other research groups have used mass spectrometry to analyze biopsied tissue and have shown that it can make these differentiations. The problem with using mass spectrometry in the operating room is sample collection. Before molecules can be analyzed, they have to be ionized and sucked up into the machine. Creating ions requires bombarding a sample with a stream of charged particles, often a gas, and these methods aren't suitable for the operating room. "A high-voltage nitrogen jet is not compatible with the human body," says Takáts.

Takáts realized that some surgical cutting tools, including electroscalpels, produce gaseous ions as a kind of waste product that are suitable for analysis with mass spectrometry. And these fumes, often called "surgical smoke," are already collected during surgery because they're harmful to the lungs. Takáts and his collaborators found that mass spectrometry of surgical smoke can be used to make a molecular map of a tumor. After the fumes are sucked into the mass spectrometer, the chemicals in the sample are identified and checked against a database to give the surgeon a readout. Gathering and analyzing a chemical sample takes a few hundred milliseconds. "We can draw a map and say this part is healthy liver, that is connective tissue, this is adipose tissue, that is cancer," says Takáts.