[Lumbar reprolapse or scar tissue? An attempt at differentiation via a computer tomographic bicolor mode].

The bicolour mode for computer tomography is explained. It replaces the soft tissue level of the computer tomogram by setting the window level to +55 Hu and its width to 1 Hu. Structures in the spinal canal with attenuation values greater than 56 Hu appear white. The cauda equina has an attenuation value of less than +45 Hu. Disc prolapses, scar tissue and solid tumours (with the exception of lipomas) have attenuation values greater than +55 Hu. The use of the bicolour mode combined with intravenous contrast in patients with post-operative symptoms can often help to differentiate between reprolapse and scarring. A time-saving method for the bicolour mode is described.