Fig. 1A–D.

Preoperative (A) coronal, (B) sagittal, and (C) axial sections of CT-MR fusion images and (D) a 3-D bone model for Patient 4 with a left distal femur osteosarcoma are shown. (A) A fusion image is in the fusion mode, which has slightly higher CT weighting than MR images. (B–C) Fusion images are in the splitting mode in which the rectangular window displays overlaid MR images on the base CT images. An image fusion is accurate and acceptable for navigation planning if the bony contours on the CT-MR images at the region of interest match within a 1-mm margin of error as visually assessed by the authors. Tumor extent (red color) is outlined on each MR image. (D) The 3-D bone tumor model reconstructed from CT images and MR segmented tumor volume is shown.