Provide a method and system for preventing the laser beam emitting portion of the burn to the diagnosis and treatment using a laser catheter for irradiating the laser beam. A method of controlling a laser irradiation apparatus including a laser catheter to be treated or diagnosed by irradiating a laser beam includes a laser beam emitting unit and a laser beam transmission means, to the heart chamber or blood vessel, heart or blood vessel lasers for comprising the step of in response to the time variation of the diffuse reflected light intensity due to red blood cells of a laser beam irradiated to the cavity, to control the laser radiation output and to prevent scorching of the blood of the beam emitting unit of the apparatus including a laser catheter method of controlling the light irradiation.レーザ光を照射するレーザカテーテルを用いた治療や診断においてレーザ光出射部が焦げ付くのを防止する方法及びシステムの提供。レーザ光伝送手段及びレーザ光出射部を含む、血管内又は心腔内にレーザ光を照射して診断又は治療を行うレーザカテーテルを含む装置のレーザ光照射の制御方法であって、血管内又は心腔内に照射したレーザ光の赤血球による拡散反射光強度の時間変化に応じて、レーザ照射出力を制御する工程を含む、レーザカテーテルを含む装置のレーザ出射部の血液の焦げ付きを防止するためのレーザ光照射の制御方法。
