Abstract: A method/device are disclosed for performing procedures in body lumens using a local energy source, with quantitative information to determine treatment parameters, to accomplish efficient, safe body lumen treatment. In one embodiment, the system comprises a special optical fiber connected to a laser device capable of emitting laser radiation, receiving reflected laser radiation and processing signals as fiber is inserted into body lumen. Quantitative measurements are carried out, while advancing the optical fiber along the lumen. In another embodiment, lumen diameter and tissue reflectivity are measured along lumen's length. The system uses accumulated data to calculate/set optimal treatment parameters, such as radiation parameters and withdrawal speed, employing physical-mathematical models relating lumen characteristics to the energy/length required to efficiently treat the lumen. Once optical fiber reaches start position, lumen characteristics have been mapped along its complete length.