Opsens Inc. of Quebec City has filed a patent application for its OptoWire diagnostic tool that can assess coronary lesions using the fractional flow reserve (FFR) technique. The company developed the instrument in parallel with EasyWire, also used in FFR, an index of the functional severity of a coronary stenosis that is calculated from pressure measurements taken before and after a narrowing of the arteries during coronary arteriography. The OptoWire is a guide wire with a fiber optic pressure sensor that is drift-free and that provides high-fidelity measurement of blood pressure in coronary arteries.