Bernhard Krauss PhD, Presenter: Employee, Siemens AG, Forchheim, Germany

Bernhard Schmidt PhD, Abstract Co-Author: Employee, Siemens AG

Thomas G. Flohr PhD, Abstract Co-Author: Employee, Siemens AG

To measure electron density by processing Dual Energy CT images.

A commercially available tissue characterization phantom (Model 467, GAMMEX rmi, Middleton, WI) simulating the abdomen (33cm of water equivalent material) was scanned on a Dual Source Dual Energy CT Scanner (SOMATOM Definition Flash, Siemens Healthcare Sector, Forchheim, Germany). The tube voltages were set to 100/Sn140kV, 80/Sn140kV and 140/80kV, respectively, where the use of an additional tin filter is indicated by "Sn". Material inserts were interchanged (5 combination) to study position dependence. Reconstructions were done with a standard Dual Energy kernel (D30f) and a Dual Energy kernel with beam hardening correction (D34f). Images were analyzed by a MATLAB program, which uses a two material decomposition approach with water and iodine as base materials and subsequently calculates electron density.  

While the standard images (D30f) showed beam hardening artifacts between the dense bone equivalent inserts, artifacts were no longer visible with beam-hardening correction (D34f). Measured electron density in the body material inserts did not depend on beam-hardening correction (measured difference <0.5%). There was good agreement with the nominal values; deviations were typically lower than 2%.

It is possible to directly measure electron density with Dual Source Dual Energy CT and image based methods; a calibration curve of electron density versus tissue CT-value is not necessary.

A reliable measurement of electron density is important for radiation therapy as well as PET attenuation correction.

Krauss, B, Schmidt, B, Flohr, T, Measuring Electron Density with Dual-Source Dual-Energy CT.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11015939.html