Xiaoye Wu PhD, Presenter: Nothing to Disclose

Piero Ugo Simoni PhD, Abstract Co-Author: Nothing to Disclose

Thomas Louis Toth, Abstract Co-Author: Nothing to Disclose

Tom Myers PhD, Abstract Co-Author: Nothing to Disclose

Charlie Shaughnessy, Abstract Co-Author: Nothing to Disclose

With the development of volumetric CT system, the conventional method of performing spectral calibration using phantoms for removing beam-hardening and ring/band artifacts exceeds practical limits: (1) the required length of the phantoms increases due to larger Z-coverage – becoming heavy and unmanageable; (2) the time required for calibration limits the design number of beam shaping filters.

The detection efficiency of each detector element is measured as a function of incident photon energy. This detection efficiency and the incident X-ray beam spectrum completely determine the spectral response of each detector and subsequently can be use to accurately calculate the proper spectral correction coefficients for different system configurations, such as a different beam filter. In principle, this method does not require the measurement of any phantom, and is applicable to systems with a multiplicity of beam filters. To further improve calibration sensitivity, a single small-size phantom is scanned with an offset from ISO-center.

The new spectral calibration algorithm has been extensively tested on LightSpeed series (GE Healthcare) CT scanners. The calibration time has been reduced by a factor of 8 to 10. Compared to conventional spectral calibration, this algorithm offers better image quality in ring/band, center artifacts and uniformity.

An algorithm to effectively and efficiently perform spectral calibration for a volumetric CT system is described. Compared with the conventional method of performing calibration, which requires multiple bulky phantoms, this new algorithm provides better accuracy and improved image quality, and significantly simplifies the calibration process.

C.S.,T.L.T.,X.W.,P.U.S.,T.M.: All the authors work for GE

Wu, X, Simoni, P, Toth, T, Myers, T, Shaughnessy, C, Volumetric CT Spectral Calibration.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4412102.html