When surgeons can't determine the edges of a tumour, it's a problem. Cut too much, and they risk hurting the patient. Cut too little, and they may leave stray cancer cells behind. Now, researchers have developed a surgical knife that can sniff the smoke made as it cuts tissue, almost instantly detecting whether cells are cancerous or healthy.
The souped-up scalpel works by analyzing lipids, the fatty molecules that make up much of the cell membrane. In the past few years, chemists have shown ratios of certain lipids can be used to identify various biological tissues, including tumours. But this requires first removing and preparing the tissue for a technique called mass spectrometry, which analyzes the mass and structure of charged molecules.
Hungarian chemist Zolt°n Tak°ts wondered if he could speed things up by directly analyzing the smoke created by the electrosurgical knives that surgeons use to cut and cauterize blood vessels. Although the smoke is "a very nasty" tarry mixture, Tak°ts says, he realized one component is a vapour containing ionized molecules -- just what mass spectrometry needs. His team has shown the lipid profiles identified by piping this vapour from an electrosurgical knife to a mass spectrometer correspond to different tissue types from animals.
His group at Imperial College London, together with Jeremy Nicholson, a biochemist who heads Imperial College's department of surgery and cancer, has tested what they've dubbed the "intelligent knife," or iKnife, in the operating room. The team collected nearly 3,000 tissue samples from about 300 cancer patients' surgeries, had pathologists identify if a sample was healthy tissue or a type of cancer, then matched up each result with the lipid profile they got by touching the iKnife to the same sample. They showed the iKnife could distinguish normal and tumour tissues from different organs, such as breast, liver, and brain, and could even identify the origin of a tumour that was a metastasis, a secondary growth seeded by a primary tumour elsewhere in the body.
The researchers next tried out the iKnife during 81 actual cancer surgeries using the 3,000-sample database as a reference. The iKnife results matched pathology lab results after the surgery for cancerous and normal tissues for nearly all patients, the researchers reported online Wednesday in Science Translational Medicine. With only a 1- to 3-second delay for an iKnife readout, "it's real-time information" Tak°ts says. Waiting for pathologists to analyze a sample can take up to 30 minutes. That feedback could minimize the time a patient is under anesthesia and allow surgeons to work faster and more effectively.