Dual energy computed tomography: simulated monoenergetic and material-selective imaging

A dual beam-quality technique was used to reduce the beam hardening artifact in CT and to obtain separate images of osseous and soft-tissue structures in phantom and clinical CT studies. Recordings were made with pulsed low and high kVp spectra with the Somatom DR2. Conventional polyenergetic and simulated monoenergetic images were reconstructed from the measurements. In the monoenergetic images the beam hardening artifacts were 60-90% lower than in the high kVp polyenergetic images whereas the noise was of the same order of magnitude in the two types. Noise in the monoenergetic images was lowest around 70-80 keV both in body and skull examinations although the contrast in the monoenergetic image was rather independent of energy.