An apparatus including: a lumen scanner (260) configured to scan a body lumen and acquire data for rendering a 3D model of the body lumen. The lumen scanner includes: an optical sensor (240) configured to acquire images of the body lumen while the lumen scanner is disposed inside the body lumen; and a fluid nozzle (202) configured to direct fluid onto an area of the body lumen imaged by the optical sensor while the lumen scanner is disposed inside the body lumen.