Methods, apparatuses and computer program products implementembodiments of the present invention that include receiving,from an imaging system operating in an image coordinate system,a three-dimensional image of a body cavity including open spaceand body tissue, and receiving, from a medical probe having alocation sensor and inserted into the body cavity, a signalindicating a location of a distal tip of the medical probe in asensor coordinate system.The image coordinate system isregistered with the sensor coordinate system so as to identifyone or more voxels in the three-dimensional image at theindicated location, and when the identified voxels have densityvalues in the received three-dimensional image that do notcorrespond to the open space, the density values of theidentified voxels are updated to correspond to the open space.
