Spinal surgery. Surgeon operating on a patient's spine. A Siemens ARCADIS Orbic 3D unit is being used to assist the surgeon. This equipment produces a three dimensional computed tomography scan of the patient's spine. The monitor showing the scanned images is seen at upper left while the scanner is seen circling around the patient, underneath the operating table. The images on the monitor are seen as a real-time video of what is happening beneath the layers of the patient's skin, minimising the need for large surgical incisions.