A method of mapping a chosen point in real space to its corresponding location in image space includes obtaining a diagnostic medical image of a subject including multiple rigid objects, and individually computing separate transforms which register each of the rigid objects in real space with their corresponding locations in image space. After choosing a target point in real space, the target point is mapped to image space using a designated transform. A number of the rigid objects are selected which are closest to the target point in image space, and an interpolated transform is generated from the separate transforms which correspond to the selected rigid objects. The target point is re-mapped in image space using the interpolated transform, and the interpolated transform is set as the designated transform for subsequent mappings.