1. A computer-implemented method for image registration, comprising: accepting a three-dimensional (3-D) image of an organ, the image comprising a first plurality of image points with respective image coordinates; accepting a map defining a distribution of values of a physiological parameter over the organ, the map comprising a second plurality of map points with respective map coordinates; associating respective confidence levels with one or more of the map coordinates and image coordinates; assigning weights to at least some of the map points and image points responsively to the confidence levels of the respective map coordinates and image coordinates; and fitting the 3-D image with the map by calculating a geometrical transformation between the map coordinates and the image coordinates based on the weights.