Methodological accuracy of image-based electron-density assessment using   dual-energy computed tomography
  Purpose: Electron density is the most important tissue property influencing photon and ion dose distributions in radiotherapy patients. Dual-energy computed tomography (DECT) enables the determination of electron density by combining the information on photon attenuation obtained at two different tube voltages. Most algorithms suggested so far use the CT numbers provided after image reconstruction as input parameters, i.e. are imaged-based. To explore the accuracy that can be achieved with these approaches, we quantify the intrinsic methodological and calibration uncertainty of the seemingly simplest approach. 
Christian M\"ohler, Patrick Wohlfahrt, Christian Richter, Steffen   Greilich
physics.med-ph