Piecewise removal of myomata (fibroids, benign tumors) from the uterine wall is performed using a hysteroresectoscope inserted through the vagina. Only radical removal of the myoma prevents regrowth, whereas penetration of the uterine wall should be avoided. Preoperative MR (Magnetic Resonance) images show the full outline and the location of the myoma in the uterine wall. Preoperative 3D US (ultrasound) reveals the part of the myoma that protrudes into the uterine cavity, but the part located in the uterine wall is almost invisible. The images and extracted preoperative information must be registered to the preoperative situation. A pragmatic solution in the form of three point incremental matching is applied. Three patients were scanned and the matching was performed on the data. The procedure provided a good match on two patients.@en